CN109156019B

CN109156019B - OFDM symbol transmission method and device

Info

Publication number: CN109156019B
Application number: CN201680085690.2A
Authority: CN
Inventors: 马雅男
Original assignee: Huawei Technologies Co Ltd
Current assignee: Huawei Technologies Co Ltd
Priority date: 2016-06-20
Filing date: 2016-06-20
Publication date: 2020-09-29
Anticipated expiration: 2036-06-20
Also published as: WO2017219215A1; CN109156019A

Abstract

An OFDM symbol transmission method and device are used for solving the problems that the CP length determined in an OFDM communication system in the prior art is inaccurate, cannot be adaptively changed according to different application environments, and is poor in applicability. The method comprises the following steps: the method comprises the steps that a sending device sends a first OFDM symbol added with a CP according to a preset first CP length to a receiving device, the receiving device generates and feeds back CP position information and CP length information to the sending device according to the first OFDM symbol, and the sending device adds the CP to a subsequent OFDM symbol according to the CP position information and the CP length information. The receiving equipment can self-adaptively determine the CP position information and the CP length information of the OFDM symbols which are suitable for the subsequent transmission of the OFDM communication system according to the OFDM symbols which are transmitted in advance, so that the inter-symbol interference is eliminated, and the method is suitable for various OFDM communication systems and has strong applicability.

Description

OFDM symbol transmission method and device

Technical Field

The present application relates to the field of communications technologies, and in particular, to a method and an apparatus for transmitting OFDM symbols.

Background

Orthogonal Frequency Division Multiplexing (OFDM) is a multi-carrier communication scheme with overlapped middle Frequency bands, and has the advantages of high Frequency utilization rate and resistance to multi-path fading, so that OFDM communication systems are widely used.

In an OFDM communication system, the transmission medium between a transmitting device and a receiving device may be an optical fiber, a coaxial cable, a network cable, etc., or the transmitting device transmits OFDM symbols by radio. When a transmission medium such as an optical fiber transmits a signal, signal pulses are spread, leading to mutual overlapping of front and rear pulses, and a wireless channel also has a multipath propagation problem, which causes Inter-Symbol Interference (ISI), thereby destroying orthogonality between subcarriers. The transmitting device needs to insert a guard interval between adjacent two OFDM symbols before transmitting the OFDM symbols. In order to eliminate the inter-symbol interference to the maximum, the length of the guard interval needs to be greater than the maximum delay spread of the channel, so that one OFDM symbol does not cause interference to the next OFDM symbol, thereby eliminating the inter-symbol interference, where the maximum delay spread of the channel may also be referred to as the maximum channel delay or the channel impulse response length.

For example, a Cyclic Prefix (CP) is inserted as a guard interval in each OFDM symbol. The transmitting device firstly determines the length of the CP (namely the length of the guard interval), and then takes the tail part of each OFDM symbol, copies the content of the CP length to the starting position of each corresponding OFDM symbol to form a prefix, namely the CP.

As can be seen from the above discussion, the transmitting device first determines the maximum delay spread of the channel of the current OFDM communication system, and then sets the CP length according to the principle that the CP length needs to be greater than the maximum delay spread of the channel. However, the CP length determined by the above method is only an estimated value, has a small probability of being most suitable for the current communication system, and cannot be adaptively changed according to different application environments, and is not suitable for a communication system in which the maximum delay spread cannot be obtained, and the applicability is poor.

Disclosure of Invention

The embodiment of the invention provides an OFDM symbol transmission method and device, which are used for solving the problems that the determined CP length in an OFDM communication system in the prior art is inaccurate, can not change according to different application environments and has poor applicability.

In one aspect, an embodiment of the present invention provides an OFDM symbol transmission method, which is applied in an OFDM communication system, and includes the following steps:

the method comprises the steps that a sending device adds a CP (cyclic prefix) at a preset position in a first OFDM (orthogonal frequency division multiplexing) symbol according to a preset CP length of a first CP, and sends the first OFDM symbol added with the CP to a receiving device, so that the receiving device adaptively determines the CP position and CP length information of the subsequently sent OFDM symbol suitable for the OFDM communication system according to the first OFDM symbol and feeds the CP position and CP length information back to the sending device; after the transmitting device receives the CP position information and the CP length information sent by the receiving device, a CP is added to a second OFDM symbol sent subsequently according to the CP position information and the CP length information, and the second OFDM symbol after the CP is added is sent to the receiving device. The CP position information is used to indicate a position where a CP needs to be added in a second subsequent OFDM symbol when the transmitting device adds the CP to the second subsequent OFDM symbol, and the CP length information includes a CP length corresponding to the position indicated by the CP position information.

By adopting the method, the receiving equipment can self-adaptively determine the CP position information and the CP length information of the OFDM symbols which are suitable for the subsequent transmission of the OFDM communication system according to the OFDM symbols which are transmitted in advance, thereby eliminating the interference between the symbols, effectively reducing the error rate of the system and improving the stability of the OFDM communication system; when the OFDM communication system changes, the receiving device can re-determine CP position information and CP length information suitable for the current OFDM communication system, manual configuration is not needed, maintenance cost is reduced, and stability of the OFDM communication system is further guaranteed; in addition, the determined CP position information and the determined CP length information in the method are not determined according to the maximum delay spread of the OFDM system, so the method is suitable for various OFDM communication systems and has strong applicability.

In one possible design, the first OFDM symbol may be an OFDM symbol that is first transmitted to the receiving device by the transmitting device, so that the receiving device may receive the first OFDM symbol to which the CP is added, determine CP position information and CP length information, and transmit the CP position information and CP length information to the transmitting device, so that the transmitting device may add the CP to the subsequent second OFDM symbol according to the CP position information and the CP length information. Therefore, the receiving device can quickly and adaptively determine the CP position information and the CP length information of the OFDM symbols which are suitable for the OFDM communication system and are transmitted subsequently according to the OFDM symbols which are transmitted for the first time, eliminate the interference among the symbols, reduce the error rate of the system to the maximum extent and improve the stability of the OFDM communication system.

In one possible design, when the sending device adds a CP at a preset position in a first OFDM symbol according to the first CP length and sends the first OFDM symbol after adding the CP to the receiving device, the sending device includes the following steps: after the first OFDM symbol is generated, firstly, performing serial-to-parallel conversion on the first OFDM symbol to generate a plurality of first parallel data, wherein each first parallel data in the plurality of first parallel data is carried on one subcarrier; then, mapping the plurality of first parallel data into a plurality of first data in a preset first modulation format; performing N-point inverse Fourier transform on the plurality of first data to generate a plurality of first time domain signals, wherein N is the same as the plurality of first parallel data in number; then, adding a CP at the preset position of each first time domain signal in the plurality of first time domain signals according to the length of the first CP, and generating a plurality of CP-added first time domain signals; and performing parallel-to-serial conversion processing on the plurality of first time domain signals added with the CP to generate first serial data, finally adding a synchronization sequence to the first serial data, performing digital-to-analog conversion processing to generate a first analog signal, and sending the first analog signal to the receiving equipment.

By the above method, the transmitting device may convert OFDM symbols into analog signals that may be transmitted through a channel between the transmitting device and the receiving device.

In one possible design, a transmission medium of a channel between the sending device and the receiving device is an optical fiber, and in the above design, when the sending device sends the first analog signal to the receiving device, the sending device needs to perform an electro-optical conversion process on the first analog signal to generate a first optical signal, and then send the first optical signal to the receiving device through the optical fiber.

By the above method, the sending device may convert the first analog signal into a first optical signal for transmission in an OFDM communication system in which a transmission medium of a channel is an optical fiber.

In one possible design, after the sending device sends the first OFDM symbol to which the CP is added to the receiving device, before the sending device adds the CP to the second OFDM symbol according to the CP location information and the second CP length corresponding to the location indicated by the CP location information, the sending device obtains a channel quality parameter of each subcarrier in a plurality of subcarriers carrying the first OFDM symbol, where the channel quality parameter of any one subcarrier includes any one or a combination of the following: bit error rate BER, signal-to-noise ratio SNR; and determining a modulation format corresponding to each subcarrier according to the channel quality parameter of each subcarrier in the plurality of subcarriers and the corresponding relation between the channel quality parameter stored in the sending equipment and the adjustment format.

By the method, the sending equipment can determine the modulation format corresponding to each subcarrier according to the channel quality parameter of each subcarrier in the plurality of subcarriers, so that the water injection process of the OFDM communication system can be realized, the utilization rate of resources is improved, and the system performance is optimized.

In one possible design, when the sending device adds a CP to the second OFDM symbol according to the CP location information and a second CP length corresponding to a location indicated by the CP location information, and sends the second OFDM symbol after the CP is added to the receiving device, the sending device includes the following steps: firstly, performing serial-to-parallel conversion processing on the second OFDM symbol to generate a plurality of second parallel data, wherein each of the plurality of second parallel data is carried on one subcarrier; then, according to the modulation format corresponding to each subcarrier determined in the above design, determining a scheduling format corresponding to a subcarrier carrying each second parallel data in the plurality of second parallel data; mapping each second parallel data in the plurality of second parallel data into second data of a scheduling format corresponding to a subcarrier carrying the corresponding second parallel data; then, performing M-point inverse fourier transform on a plurality of second data mapped by the plurality of second parallel data to generate a plurality of second time domain signals, wherein M is the same as the plurality of second parallel data in number; adding a CP to each second time domain signal in the plurality of second time domain signals according to the CP position information and the CP length information to generate a plurality of CP-added second time domain signals; and finally, performing parallel-serial conversion processing on the plurality of second time domain signals added with the CP to generate second serial data, adding a synchronization sequence to the second serial data, performing digital-to-analog conversion processing to generate a second analog signal, and sending the second analog signal to the receiving equipment.

Through the above steps, in the process of sending the subsequent second OFDM symbol by the sending device, firstly, according to the CP position information and the CP length information applicable to the OFDM communication system, the CP is added to the second OFDM symbol, so that inter-symbol interference of the subsequently transmitted OFDM symbol can be eliminated, the system error rate is effectively reduced, and the stability of the OFDM communication system is improved.

In a possible design, a transmission medium of the channel is an optical fiber, and in the above design, when the sending device sends the second analog signal to the receiving device, the sending device further needs to perform an electro-optical conversion process on the second analog signal to generate a second optical signal, and finally sends the second optical signal to the receiving device through the optical fiber.

By the above method, the sending device may convert the second analog signal into a second optical signal for transmission in the OFDM communication system in which the transmission medium of the channel is an optical fiber.

In one possible design, the position to be added in the second OFDM symbol indicated by the CP position information includes any one or a combination of the following: the front end of the data content, the back end of the data content. Therefore, the CP position information can ensure that the OFDM symbols are suitable for subsequent transmission of the OFDM communication system, after the transmitting equipment adds a CP to a subsequent second OFDM symbol according to the CP position information, the intersymbol interference can be eliminated, the system error rate is reduced to the maximum extent, and the stability of the OFDM communication system is improved.

In one possible design, the position indicated by the CP location information includes a front end of data content, and the sending device, when adding a CP to each of the plurality of second time domain signals according to the CP location information and the CP length information, includes the following steps: the method comprises the steps of firstly selecting first data content with a second CP length from the end position of the data content in a third time domain signal, and then adding the selected first data content to the front end of the data content in the third time domain signal as the CP of the third time domain signal. The third time domain signal is any one of the plurality of second time domain signals, and the second CP length is a CP length corresponding to a front end of data content included in the CP length information.

By the method, the sending device can add the CP to the second OFDM symbol according to the CP position information and the CP length information.

In one possible design, the position indicated by the CP position includes a back end of data content, and the sending device, when adding a CP to each of the plurality of second time domain signals according to the CP position information and the CP length information, includes the following steps: firstly, selecting a second data content with a third CP length backwards from the initial position of the data content in a fourth time domain signal; then, the selected second data content is used as the CP of the fourth time domain signal and added to the back end of the data content in the fourth time domain signal. The fourth time domain signal is any one of the plurality of second time domain signals, and the third CP length is a CP length corresponding to a back end of the data content included in the CP length information.

On the other hand, the embodiment of the invention also provides an OFDM symbol transmission method, which is applied to an OFDM communication system, and comprises the following steps:

the method comprises the steps that a receiving device obtains a first Orthogonal Frequency Division Multiplexing (OFDM) symbol sent by a sending device, wherein the first OFDM symbol requires the sending device to add a Cyclic Prefix (CP) at a preset position according to a preset CP length of a first CP before sending; the receiving device obtains equalization information of the receiving device for performing equalization processing on the first OFDM symbol, so that the position information and the length information of the CP can be determined according to the equalization information, and finally the determined position information and the determined length information of the CP are sent to the sending device. Wherein the equalization information includes a plurality of tap positions and a tap coefficient corresponding to each tap position, and any one tap position is used for representing a delay time of one tap relative to a specified time; the CP position information is used to indicate a position where the CP needs to be added in a second subsequent OFDM symbol when the transmitting device adds the CP to the second subsequent OFDM symbol, and the CP length information includes a CP length corresponding to the position indicated by the CP position information.

In one possible design, the receiving device, when acquiring (or recovering, or demodulating) the first OFDM symbol, includes the steps of: the receiving device acquires a first analog signal, wherein the first analog signal is generated after the transmitting device processes the first OFDM symbol; performing analog-to-digital conversion processing and synchronous processing on the first analog signal to generate first serial data; carrying out equalization processing and serial-parallel conversion processing on the first serial data to obtain a plurality of first time domain signals added with the CP; removing the CP from the plurality of CP-added first time domain signals according to the length of the first CP and the preset position to generate a plurality of CP-removed first time domain signals; performing N-point Fourier transform and frequency domain equalization on the plurality of CP-removed first time domain signals to generate a plurality of first data, wherein N is the same as the number of the plurality of CP-removed first time domain signals; according to a preset first adjustment format, demapping the first data to generate first parallel data; and performing parallel-to-serial conversion processing on the plurality of first parallel data to generate the first OFDM symbol. The first modulation format is agreed between the sending device and the receiving device, and since the sending device maps the first OFDM symbol according to the first modulation format, the receiving device also performs demapping according to the first modulation format after receiving the first OFDM symbol. In this way, it can be ensured that the receiving device can demodulate the first OFDM symbol.

In a possible design, a transmission medium of a channel between the sending device and the receiving device is an optical fiber, and when the receiving device obtains the first analog signal, the receiving device first receives a first optical signal sent by the sending device through the optical fiber; then, the first optical signal is subjected to photoelectric conversion processing to generate the first analog signal.

By the method, the receiving device can convert the received first optical signal into an electrical signal, so that the first OFDM symbol can be demodulated by subsequent processing.

In one possible design, when determining the CP location information and the CP length information according to the equalization information, the receiving device includes the following steps: firstly, according to the sequence of tap positions, sorting tap coefficients corresponding to each tap position to generate a first queue; then, in the first queue, determining a first tap coefficient with the largest value; acquiring a tap threshold, setting a tap coefficient smaller than the tap threshold in the first queue to be 0, and generating a second queue; determining a second position of a second tap coefficient in the second queue and a third position of a third tap coefficient in the second queue, wherein the second tap coefficient is a tap coefficient which is first from left to right and is not 0 in the second queue, and the third tap coefficient is a tap coefficient which is first from right to left and is not 0 in the second queue; and finally, determining the CP position information and the CP length information according to the first position, the second position and the third position of the first tap coefficient in the second queue.

By the method, the receiving device can obtain the CP position information and the CP length information according to the tap characteristic of the equalization processing of the first OFDM symbol, so that the determined CP position information and the CP length information are suitable for the OFDM communication system, the inter-symbol interference of the subsequently transmitted OFDM symbol can be eliminated, the system error rate is effectively reduced, and the stability of the OFDM communication system is improved.

In one possible design, the determining, by the receiving device, the CP location information and the CP length information according to the first location, the second location, and the third location includes:

firstly, the receiving device obtains the sampling interval T between any two adjacent taps for equalization processing_eAnd a sampling interval T for the transmission of OFDM symbols by the transmission device_d(ii) a Then, the receiving device determines a difference between a value of the first position and a value of the second position as a first distance, and a difference between a value of the third position and a value of the second position as a second distance; when the first distance is not 0, the receiving device determines that the CP position information comprises the front end of the data content, and the receiving device determines that the CP position information comprises the front end of the data content according to the first distance and the T_eAnd said T_dDetermining a second CP length corresponding to the front end of the data content included in the CP length information; when the second distance is not 0, the receiving device determines that the CP position information comprises the back end of the data content, and the receiving device determines that the CP position information comprises the back end of the data content according to the second distance and the T_eAnd said T_dDeterminingAnd the CP length information comprises a third CP length corresponding to the back end of the data content.

By the method, the receiving device can accurately determine the CP position information and the CP length information which are suitable for the OFDM communication system, and then the CP can be added to the second OFDM symbol which is transmitted subsequently through the two items of information, so that the inter-symbol interference of the OFDM symbol which is transmitted subsequently is eliminated, the system error rate is effectively reduced, and the stability of the OFDM communication system is improved.

In one possible design, the second CP length, conforms to the following equation:

wherein S is₁Is the first distance;

the third CP length, according to the following formula:

wherein S is₂Is the second distance.

By the method, the receiving device can accurately determine the CP length information suitable for the OFDM communication system.

In one possible design, after the receiving device obtains the first OFDM symbol, the receiving device determines a channel quality parameter of each of a plurality of subcarriers carrying the first OFDM symbol, and sends the determined channel quality parameter of each of the plurality of subcarriers carrying the first OFDM symbol to the sending device, so that the sending device can determine a modulation format corresponding to each subcarrier according to the channel quality parameter of each of the plurality of subcarriers, thereby implementing a water injection procedure of the OFDM communication system, improving a utilization rate of resources, and optimizing system performance. Wherein, the channel quality parameter of any subcarrier includes any one or combination of the following: bit error rate BER, signal-to-noise ratio SNR.

In order to implement the water injection process of the OFDM communication system, improve the utilization rate of resources, and optimize the system performance, the sending device determines the modulation format corresponding to each subcarrier according to the channel quality parameter of each subcarrier of the plurality of subcarriers, and maps the data carried in each subcarrier to the corresponding scheduling format according to the modulation format corresponding to each subcarrier, so that when the receiving device receives an OFDM symbol, the receiving device also needs to demap the data carried in each subcarrier according to the adjustment format corresponding to each subcarrier, thereby ensuring that the receiving device can demodulate to obtain the OFDM symbol.

In one possible design, the receiving device acquires (or recovers, or demodulates) a second OFDM symbol, where the second OFDM symbol requires the transmitting device to add a CP according to the CP location information and the CP length information before transmitting, and specifically includes the following steps: the receiving device acquires a second analog signal, wherein the second analog signal is generated after the transmitting device processes the second OFDM symbol; performing analog-to-digital conversion processing and synchronous processing on the second analog signal to generate second serial data; performing equalization processing and serial-parallel conversion processing on the second serial data to obtain a plurality of second time domain signals added with the CP; removing the CP from the plurality of CP-added second time domain signals according to the CP position information and the CP length information to generate a plurality of CP-removed second time domain signals; performing M-point Fourier transform and frequency domain equalization on the plurality of CP-removed second time domain signals to generate a plurality of second data, wherein the M is the same as the plurality of CP-removed second time domain signals in number; according to the modulation format corresponding to each subcarrier, one second data in the plurality of second data carried in the corresponding subcarrier is subjected to demapping to generate a plurality of second parallel data; and performing parallel-serial conversion processing on the plurality of second parallel data, and demodulating the second OFDM symbol.

By the method, the receiving device can demodulate the second OFDM symbol.

In a possible design, a transmission medium of a channel between the sending device and the receiving device is an optical fiber, and when the receiving device obtains the second analog signal, the receiving device first receives a second optical signal sent by the sending device through the optical fiber; then, the second optical signal is subjected to photoelectric conversion processing to generate the second analog signal.

By the method, the receiving device can convert the received second optical signal into an electrical signal, so that the second OFDM symbol can be demodulated by subsequent processing.

In another aspect, an embodiment of the present invention further provides a sending device, where the sending device has a function of implementing a behavior of the sending device in the foregoing method example. The functions can be realized by hardware, and the functions can also be realized by executing corresponding software by hardware. The hardware or software includes one or more modules corresponding to the above-described functions.

In a possible design, the structure of the sending device includes a processing unit and a receiving unit, and these units may execute corresponding functions in the foregoing method example, which is specifically referred to the detailed description in the method example, and is not described herein again.

In one possible design, the control device includes a transceiver, a processor, a bus, and a memory, where the transceiver is configured to perform communication interaction with a receiving device in the OFDM communication system, and the processor is configured to support a sending device to perform corresponding functions in the above method. The memory is coupled to the processor and retains program instructions and data necessary for the transmitting device.

In another aspect, an embodiment of the present invention further provides a receiving device, where the receiving device has a function of implementing a behavior of the receiving device in the foregoing method example. The functions can be realized by hardware, and the functions can also be realized by executing corresponding software by hardware. The hardware or software includes one or more modules corresponding to the above-described functions.

In a possible design, the structure of the receiving device includes a processing unit and a sending unit, and these units may execute corresponding functions in the foregoing method example, which is specifically referred to the detailed description in the method example, and is not described herein again.

In one possible design, the receiving device includes a transceiver, a processor, a bus, and a memory, wherein the transceiver is configured to perform communication interaction with a transmitting device in the OFDM communication system, and the processor is configured to support the receiving device to perform the corresponding functions in the above method. The memory is coupled to the processor and retains program instructions and data necessary for the receiving device.

In another aspect, an embodiment of the present invention provides an OFDM system, which includes a transmitting device and a receiving device.

In the embodiment of the invention, a sending device sends a first OFDM symbol added with a CP according to a preset first CP length to a receiving device, and the receiving device generates and feeds back CP position information and CP length information to the sending device according to the first OFDM symbol, so that the sending device adds the CP to a subsequent OFDM symbol according to the CP position information and the CP length information. The receiving equipment can self-adaptively determine the CP position information and the CP length information of the OFDM symbols which are suitable for the subsequent transmission of the OFDM communication system according to the OFDM symbols which are transmitted in advance, so that the inter-symbol interference is eliminated, and the method is suitable for various OFDM communication systems and has strong applicability.

Drawings

Fig. 1 is a schematic diagram of an OFDM communication system according to an embodiment of the present invention;

fig. 2 is a flowchart of an OFDM symbol transmission method according to an embodiment of the present invention;

fig. 3 is a flowchart of another OFDM symbol transmission method according to an embodiment of the present invention;

fig. 4 is a schematic diagram illustrating BER curves corresponding to two CP adding modes according to an embodiment of the present invention;

fig. 5 is a schematic structural diagram of a sending device according to an embodiment of the present invention;

fig. 6 is a schematic structural diagram of a receiving device according to an embodiment of the present invention;

fig. 7 is a schematic structural diagram of another sending device according to an embodiment of the present invention;

fig. 8 is a schematic structural diagram of another receiving device according to an embodiment of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention clearer, the present invention will be described in further detail with reference to the accompanying drawings, and it is apparent that the described embodiments are only a part of the embodiments of the present invention, not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

The embodiment of the invention provides an OFDM symbol transmission method and device, which are used for solving the problems that the determined CP length in an OFDM communication system in the prior art is inaccurate, can not change according to different application environments, and has poor applicability. The method and the device are based on the same inventive concept, and because the principles of solving the problems of the method and the device are similar, the implementation of the device and the method can be mutually referred, and repeated parts are not repeated.

By adopting the technical scheme of the invention, when sending an OFDM symbol to a receiving device by a sending device in an OFDM communication system, a CP is added to a first OFDM symbol to be sent according to a preset first CP length, and the first OFDM symbol added with the CP is sent to the receiving device, so that the receiving device generates CP position information and CP length information according to the received first OFDM symbol added with the CP, and feeds the CP position information and the CP length information back to the sending device; the transmitting device may add a CP to a subsequent OFDM symbol (a second OFDM symbol) according to the CP position information and the CP length information, and transmit the second OFDM symbol to which the CP is added to the receiving device. The CP position information is used to indicate a position where a CP needs to be added in a second subsequent OFDM symbol when the transmitting device adds the CP to the second subsequent OFDM symbol, and the CP length information includes a CP length corresponding to the position indicated by the CP position information. In this way, in the OFDM communication system, the receiving device can adaptively determine CP position information and CP length information of the OFDM symbols which are suitable for the subsequent transmission of the OFDM communication system according to the OFDM symbols which are transmitted in advance, so that the inter-symbol interference is eliminated, the system error rate is effectively reduced, and the stability of the OFDM communication system is improved; when the OFDM communication system changes, the receiving device can re-determine CP position information and CP length information suitable for the current OFDM communication system, manual configuration is not needed, maintenance cost is reduced, and stability of the OFDM communication system is further guaranteed; in addition, the determined CP position information and the determined CP length information in the method are not determined according to the maximum delay spread of the OFDM system, so the method is suitable for various OFDM communication systems and has strong applicability.

It is to be understood that the terms "first," "second," and the like in the description of the present application are used for descriptive purposes only and not for purposes of indicating or implying relative importance, nor for purposes of indicating or implying order.

The OFDM symbol transmission method provided in the embodiment of the present invention is suitable for the OFDM communication system shown in fig. 1, where the OFDM communication system includes a sending device 101 and a receiving device 102, the sending device 101 and the receiving device 102 are connected through a channel, and the sending device 101 transmits an OFDM symbol to the receiving device 102 through the channel.

The channel may be a wireless channel corresponding to a wireless transmission mode through a specific transmission medium, such as a cable, a network cable, an optical fiber, and the like;

before transmitting the OFDM symbol to the OFDM symbol through the channel, the sending device 101 needs to process the OFDM symbol, which specifically includes: serial-to-parallel conversion processing, modulation format mapping processing, inverse fourier transform processing, CP adding processing, parallel-to-serial conversion processing, synchronization sequence adding processing, digital-to-analog conversion processing, and the like, and finally an analog signal is generated. Optionally, when the transmission medium of the channel is an optical fiber, after the sending device 101 generates the analog signal, it needs to perform an electrical-to-optical conversion process to convert the analog signal into an optical signal that can be transmitted in the optical fiber.

Optionally, in the sending device 101, according to a logic function of the sending device 101 performing the above processing on the OFDM symbol, the sending device 101 may be divided into a plurality of logic modules, for example, as shown in the figure, the sending device 101 includes: a first serial-to-parallel conversion unit 1011, a mapping unit 1012, an inverse fourier transform unit 1013, an adding CP unit 1014, a first parallel-to-serial conversion unit 1015, a first synchronization unit 1016, and a digital-to-analog conversion unit 1017. Optionally, when the transmission medium of the channel is an optical fiber, the sending apparatus 101 further includes an electrical-to-optical conversion unit 1018.

The first serial-to-parallel conversion unit 1011 is configured to perform serial-to-parallel conversion on the to-be-transmitted OFDM symbol generated by the sending device, and generate a plurality of parallel data, where each parallel data is carried on one subcarrier;

the mapping unit 1012 is configured to map the plurality of parallel data into corresponding formatted data;

the inverse fourier transform unit 1013 is configured to perform inverse fourier transform on the plurality of data mapped by the mapping unit 1012 to generate a plurality of time domain signals;

the CP adding unit 1014 is configured to add a CP to the plurality of time domain signals, respectively;

the first parallel-to-serial conversion unit 1015 is configured to perform parallel-to-serial conversion on the plurality of time domain signals to which the CP is added, and generate serial data;

the first synchronization unit 1016 is configured to add a synchronization sequence to the serial data generated by the first parallel-to-serial conversion unit 1015;

the digital-to-analog conversion unit 1017 is configured to convert the serial data to which the synchronization sequence is added into an analog signal;

the electrical-to-optical conversion unit 1018 is configured to convert an analog signal (electrical signal) into an optical signal for transmission in an optical fiber, for example, the electrical-to-optical conversion unit 1018 may be an 850nm vcsel laser.

The receiving device 102 may obtain an analog signal or an optical signal through the channel, and when a transmission medium of the channel is an optical fiber, the receiving device 102 receives the optical signal through the channel. The process of obtaining the OFDM symbol by the receiving device 102 according to the received analog signal sequentially includes: analog-to-digital conversion processing, synchronization processing, equalization processing, serial-to-parallel conversion processing, CP removal processing, fourier transform processing, frequency domain equalization processing, demapping processing, and parallel-to-serial conversion processing. Optionally, when the receiving device 102 obtains an OFDM symbol according to the received optical signal, before sequentially performing the above processing, a photoelectric conversion process is further included to convert the optical signal into an electrical signal (analog signal).

Optionally, in the receiving device 102, the receiving device 102 may be divided into a plurality of logic modules according to a logic function of the receiving device 102 performing the above processing on the analog signal, for example, as shown in the figure, the receiving device 102 includes: an analog-to-digital conversion unit 1021, a second synchronization unit 1022, a first equalizer 1023, a second serial-to-parallel conversion unit 1024, a CP removal unit 1025, a fourier transform unit 1026, a second equalizer 1027, a demapping unit 1028, and a second parallel-to-serial conversion unit 1029. Optionally, when the transmission medium of the channel is an optical fiber, the receiving device 102 further includes an optical-to-electrical conversion unit 1020.

The photoelectric conversion unit 1020 is configured to convert an optical signal received through an optical fiber into an analog signal (electrical signal) for subsequent processing, so as to restore an OFDM symbol;

the analog-to-digital conversion unit 1021 is configured to convert the analog signal converted by the photoelectric conversion unit 1020 or the analog signal received through a channel into a digital signal;

the second synchronization unit 1022 is configured to perform synchronization detection on the digital signal to generate serial data;

the first Equalizer 1023 includes a plurality of taps and is used for performing equalization processing on the serial data to reduce the bit error rate, and the equalization processing may be Feed-Forward Equalizer (FFE) equalization processing or Decision Feedback Equalizer (DFE) equalization processing, or the like.

The second serial-to-parallel conversion unit 1024 is configured to perform serial-to-parallel conversion on the equalized serial data to obtain a plurality of time domain signals to which CPs are added;

the CP removing unit 1025 is configured to perform CP removing processing on the plurality of CP-added time domain signals to generate a plurality of CP-removed time domain signals;

the fourier transform unit 1026 is configured to perform fourier transform on the plurality of CP-removed time domain signals;

the second equalizer 1027 is configured to perform frequency domain equalization on the time domain signal after fourier transform;

the demapping unit 1028 is configured to demap corresponding data to generate multiple parallel data, where the multiple frequency domain equalized data correspond to the adjustment format;

the second parallel-to-serial conversion unit 1029 is configured to perform parallel-to-serial conversion processing on the multiple parallel data, and restore an OFDM symbol.

Mapping the parallel data into corresponding data with adjusted format;

the receiving equipment demaps the plurality of first data according to a preset first adjustment format to generate a plurality of first parallel data;

and the receiving equipment performs parallel-serial conversion processing on the plurality of first parallel data to generate the first OFDM symbol.

An embodiment of the present invention provides an OFDM symbol transmission method, which is applied to a transmitting device in an OFDM communication system shown in fig. 1, and as shown in fig. 2, a specific process of the method includes:

step 201: the sending equipment adds the CP at a preset position in the first OFDM symbol according to a preset first CP length, and sends the first OFDM symbol added with the CP to the receiving equipment.

The length of the first CP and the preset position are agreed between the sending device and the receiving device, so that CP removal processing is performed subsequently after the receiving device receives the first OFDM symbol to which the CP is added, according to the length of the first CP and the preset position. The preset position may also be a front end of the data content and/or a back end of the data content. When the number of the preset positions is two, the first CP length is a preset CP length corresponding to the front end of the data content and a preset CP length corresponding to the rear end of the data content.

Optionally, the first OFDM symbol may be an OFDM symbol that is first sent to the receiving device by the sending device, so that the receiving device may receive the first OFDM symbol to which the CP is added, determine CP position information and CP length information, and send the CP position information and CP length information to the sending device, so that the sending device may add the CP to the subsequent second OFDM symbol according to the CP position information and the CP length information. Therefore, the receiving device can quickly and adaptively determine the CP position information and the CP length information of the OFDM symbols which are suitable for the OFDM communication system and are transmitted subsequently according to the OFDM symbols which are transmitted for the first time, eliminate the interference among the symbols, reduce the error rate of the system to the maximum extent and improve the stability of the OFDM communication system.

As can be seen from the above discussion of the transmitting device in the OFDM communication system shown in fig. 1 in the above embodiment, the transmitting device needs to perform processing, such as serial-to-parallel conversion processing, modulation format mapping processing, inverse fourier transform processing, CP adding processing, parallel-to-serial conversion processing, synchronization sequence adding processing, digital-to-analog conversion processing, and the like, on the OFDM symbols before transmitting the OFDM symbols to the OFDM symbols through the channel. Optionally, an electrical-to-optical conversion process is further included, so that the OFDM symbol can be transmitted in a channel.

Optionally, the sending device adds a CP at a preset position in a first OFDM symbol according to the first CP length, and sends the first OFDM symbol to which the CP is added to the receiving device, including the following steps:

after the sending device generates the first OFDM symbol, performing serial-to-parallel conversion on the first OFDM symbol to generate a plurality of first parallel data, where each of the plurality of first parallel data is carried on one subcarrier;

the sending equipment maps the plurality of first parallel data into a plurality of first data in a preset first modulation format;

the sending equipment performs N-point inverse Fourier transform on the plurality of first data to generate a plurality of first time domain signals, wherein N is the same as the plurality of first parallel data in number;

the sending equipment adds a CP at the preset position of each first time domain signal in the plurality of first time domain signals according to the length of the first CP, and generates a plurality of CP-added first time domain signals;

and the sending equipment performs parallel-to-serial conversion processing on the plurality of first time domain signals added with the CP to generate first serial data, adds a synchronization sequence to the first serial data, performs digital-to-analog conversion processing to generate a first analog signal, and sends the first analog signal to the receiving equipment.

The preset first modulation format may be Quadrature Amplitude Modulation (QAM), Quadrature Phase Shift Keying (QPSK), and the like, which is not limited in the present invention. The first modulation format is agreed between the transmitting device and the receiving device, so that the receiving device performs demapping according to the first modulation format after receiving the first OFDM symbol.

Optionally, the adding, by the sending device, a CP to each of the plurality of first time domain signals according to the first CP length to generate a plurality of CP-added first time domain signals, includes:

the sending device may adopt a conventional CP adding technique to select the data content with the length of the first CP from the end position of the data content in each first time domain signal, and add the data content to the front end of the data content in the corresponding first time domain signal. However, since the first CP length is only an estimated value, there is a small probability that it is most suitable for the OFDM communication system. Compared with the ideal CP length which is most suitable for the OFDM communication system, when the first CP length is smaller, the intersymbol interference can not be completely eliminated, so that the system error rate can not be effectively reduced, and the stability of the OFDM communication system can not be optimized; when the first CP length is large, although inter-symbol interference can be completely eliminated, the data content length included in each OFDM symbol is small, which causes resource waste and reduces the data transmission efficiency of the OFDM communication system.

Optionally, when a transmission medium of a channel between the sending device and the receiving device is an optical fiber, the sending device sends the first analog signal to the receiving device, including:

the sending equipment carries out electro-optical conversion processing on the first analog signal to generate a first optical signal;

and the sending equipment sends the first optical signal to the receiving equipment through an optical fiber.

Step 202: the sending device receives CP position information and CP length information sent by the receiving device, wherein the CP position information and the CP length information are determined by the receiving device according to the received first OFDM symbol added with the CP, the CP position information is used for indicating the position of the second OFDM symbol to which the CP needs to be added when the sending device adds the CP to the subsequent second OFDM symbol, and the CP length information comprises the CP length corresponding to the position indicated by the CP position information.

The CP position and CP length information are determined by the receiving device according to equalization information obtained by the receiving device performing equalization processing on the first OFDM symbol in an acquisition process after acquiring the first OFDM symbol, where the equalization information includes a plurality of tap positions and tap coefficients corresponding to each tap position, and any one of the tap positions is used to indicate a delay time of one tap with respect to a specified time.

In the embodiment of the invention, the CP position information and the CP length information sent by the receiving equipment are obtained according to the tap characteristics of the equalization processing, so that the determined CP position information and the determined CP length information are suitable for the OFDM communication system, the inter-symbol interference of subsequently transmitted OFDM symbols can be eliminated, the system error rate is effectively reduced, and the stability of the OFDM communication system is improved.

Step 203: and the sending equipment adds the CP to the second OFDM symbol according to the CP position information and the CP length information, and sends the second OFDM symbol after the CP is added to the receiving equipment.

Optionally, after step 201 and before step 203, the method further includes:

the sending device obtains a channel quality parameter of each subcarrier of a plurality of subcarriers carrying the first OFDM symbol, and the channel quality parameter of any one subcarrier includes any one or a combination of the following: bit Error Rate (BER), Signal to Noise Ratio (SNR); optionally, the channel quality parameter of each of the multiple subcarriers carrying the first OFDM symbol may be sent by the receiving device;

and the sending equipment determines the modulation format corresponding to each subcarrier according to the channel quality parameter of each subcarrier in the plurality of subcarriers.

The sending device stores the corresponding relation between the channel quality parameter and the adjustment format, so that the sending device can determine the modulation format corresponding to each subcarrier according to the channel quality parameter of each subcarrier in the plurality of subcarriers, thereby realizing the water injection process of the OFDM communication system, improving the utilization rate of resources and optimizing the system performance.

The sending device adds a CP to the second OFDM symbol according to the CP location information and a second CP length corresponding to a location indicated by the CP location information, and sends the second OFDM symbol after the CP is added to the receiving device, including:

the sending device performs serial-to-parallel conversion processing on the second OFDM symbol to generate a plurality of second parallel data, wherein each of the plurality of second parallel data is carried on one subcarrier;

the sending equipment determines a scheduling format corresponding to a subcarrier carrying each second parallel data in the plurality of second parallel data according to a modulation format corresponding to each subcarrier;

the sending equipment maps each second parallel data in the plurality of second parallel data into second data of a scheduling format corresponding to a subcarrier carrying the corresponding second parallel data;

the sending device performs M-point inverse Fourier transform on a plurality of second data mapped by the plurality of second parallel data to generate a plurality of second time domain signals, wherein M is the same as the plurality of second parallel data in number;

the sending equipment adds a CP to each second time domain signal in the plurality of second time domain signals according to the CP position information and the CP length information to generate a plurality of second time domain signals added with the CP;

and the transmitting equipment performs parallel-serial conversion processing on the plurality of second time domain signals added with the CP to generate second serial data, adds a synchronization sequence to the second serial data, performs digital-to-analog conversion processing to generate a second analog signal, and transmits the second analog signal to the receiving equipment.

Optionally, when the transmission medium of the channel is an optical fiber, the sending device sends the second analog signal to the receiving device, including:

the sending equipment carries out electro-optical conversion processing on the second analog signal to generate a second optical signal;

and the transmitting equipment transmits the second optical signal to the receiving equipment through an optical fiber.

Specifically, the position to be added in the second OFDM symbol indicated by the CP position information includes any one or a combination of the following: the front end of the data content, the back end of the data content. Obviously, the location indicated by the CP location information includes three cases:

in the first case: a front end comprising only data content;

in the second case: a back end comprising only data content;

in the third case: including the front end of the data content and the back end of the data content.

It should be noted that, in the process of adding a CP by a sending device, the data content with the set length is selected as the data content with the set length to be copied.

Optionally, in the first case, the adding, by the sending device, a CP to each of the plurality of second time domain signals according to the CP position information and the CP length information includes:

the sending device selects a first data content with a second CP length from the end position of the data content in a third time domain signal forward, wherein the third time domain signal is any one of the plurality of second time domain signals, and the second CP length is a CP length corresponding to the front end of the data content included in the CP length information;

the sending device adds the selected first data content as the CP of the third time domain signal to the front end of the data content in the third time domain signal, that is, adds the first data content to the extra front of the front end of the data content in the third time domain signal.

Optionally, in the second case, the adding, by the sending device, a CP to each of the plurality of second time domain signals according to the CP position information and the CP length information includes:

the sending device selects a second data content with a third CP length backwards from the starting position of the data content in a fourth time domain signal, wherein the fourth time domain signal is any one of the plurality of second time domain signals, and the third CP length is a CP length corresponding to the rear end of the data content included in the CP length information;

the sending device adds the selected second data content to the back end of the data content in the fourth time domain signal, that is, adds the second data content to the additional back of the back end of the data content in the fourth time domain signal, as the CP of the fourth time domain signal.

Optionally, in a third case, the adding, by the sending device, a CP to each of the plurality of second time domain signals according to the CP position information and the CP length information includes:

the sending equipment selects a third data content with a fourth CP length from the end position of the data content in the fifth time domain signal; selecting a fourth data content with a fifth CP length from the initial position of the data content in the fifth time domain signal; the fifth time domain signal is any one of the plurality of second time domain signals, the fourth CP length is a CP length corresponding to a front end of the data content included in the CP length information, and the fifth CP length is a CP length corresponding to a rear end of the data content included in the CP length information;

the sending device takes the selected third data content as the CP of the fifth time domain signal, and adds the CP to the front end of the data content in the third time domain signal; and adding the selected fourth data content as the CP of the fifth time domain signal to the back end of the data content in the fourth time domain signal.

By the method, the sending equipment can add the CP to each second time domain signal in the plurality of second time domain signals according to the CP position information and the CP length information, so that the inter-symbol interference of subsequently transmitted OFDM symbols can be eliminated, the system error rate is effectively reduced, and the stability of the OFDM communication system is improved.

By adopting the OFDM symbol transmission method provided by the embodiment of the invention, in an OFDM communication system, when a sending device sends an OFDM symbol to a receiving device, a CP is added to a first OFDM symbol to be sent according to a preset first CP length, and the first OFDM symbol with the CP added is sent to the receiving device, so that the receiving device generates CP position information and CP length information according to the received first OFDM symbol with the CP added, and feeds the CP position information and the CP length information back to the sending device; the transmitting device may add a CP to a subsequent OFDM symbol (a second OFDM symbol) according to the CP position information and the CP length information, and transmit the second OFDM symbol to which the CP is added to the receiving device. The CP position information is used to indicate a position where a CP needs to be added in a second subsequent OFDM symbol when the transmitting device adds the CP to the second subsequent OFDM symbol, and the CP length information includes a CP length corresponding to the position indicated by the CP position information. In this way, in the OFDM communication system, the receiving device can adaptively determine CP position information and CP length information of the OFDM symbols which are suitable for the subsequent transmission of the OFDM communication system according to the OFDM symbols which are transmitted in advance, so that the inter-symbol interference is eliminated, the system error rate is effectively reduced, and the stability of the OFDM communication system is improved; when the OFDM communication system changes, the receiving device can re-determine CP position information and CP length information suitable for the current OFDM communication system, manual configuration is not needed, maintenance cost is reduced, and stability of the OFDM communication system is further guaranteed; in addition, the determined CP position information and the determined CP length information in the method are not determined according to the maximum delay spread of the OFDM system, so the method is suitable for various OFDM communication systems and has strong applicability.

Based on the foregoing embodiments, an embodiment of the present invention further provides another OFDM symbol transmission method, where the method is applied to a receiving device in an OFDM communication system as shown in fig. 1, and with reference to fig. 3, a specific flow of the method includes:

step 301: the method includes the steps that a receiving device obtains a first OFDM symbol sent by a sending device, wherein the first OFDM symbol needs the sending device to add a CP at a preset position according to a preset first CP length before sending.

Wherein, the first CP length and the preset position are agreed between the sending device and the receiving device, so that after the receiving device receives the first OFDM symbol after CP is added, CP removal processing is performed according to the first CP length and the preset position.

According to the above embodiment, as the sending device performs processing operation on the first OFDM symbol, correspondingly, the receiving device needs to perform the following processing on an original signal received through a channel to restore the first OFDM symbol: analog-to-digital conversion processing, synchronization processing, equalization processing, serial-to-parallel conversion processing, CP removal processing, fourier transform processing, frequency domain equalization processing, demapping processing, and parallel-to-serial conversion processing. Optionally, when the original signal received by the receiving device is an optical signal, before the above processing is sequentially performed, a photoelectric conversion process is further performed.

Optionally, the obtaining, by the receiving device, the first OFDM symbol specifically includes the following steps:

the receiving equipment acquires a first analog signal;

the receiving equipment performs analog-to-digital conversion processing and synchronous processing on the first analog signal to generate first serial data;

the receiving equipment performs equalization processing and serial-parallel conversion processing on the first serial data to obtain a plurality of first time domain signals added with the CP; wherein, the equalization process may be an FFE equalization process or a DFE equalization process, etc., which is not limited in the present invention;

the receiving device removes the CP from the plurality of CP-added first time domain signals according to the length of the first CP and the preset position, and generates a plurality of CP-removed first time domain signals;

the receiving device performs N-point Fourier transform and frequency domain equalization on the plurality of CP-removed first time domain signals to generate a plurality of first data, wherein N is the same as the number of the plurality of CP-removed first time domain signals;

The first modulation format is agreed between the sending device and the receiving device, and since the sending device maps the first OFDM symbol according to the first modulation format, the receiving device also performs demapping according to the first modulation format after receiving the first OFDM symbol. In this way, it can be ensured that the receiving device can demodulate the first OFDM symbol.

Optionally, when a transmission medium of a channel between the sending device and the receiving device is an optical fiber, the obtaining, by the receiving device, the first analog signal includes:

the receiving equipment receives a first optical signal sent by the sending equipment through an optical fiber;

and the receiving equipment carries out photoelectric conversion processing on the first optical signal to generate the first analog signal.

The first OFDM symbol may be an OFDM symbol that is first transmitted to the receiving device by the transmitting device, and thus, the receiving device may receive the first OFDM symbol to which the CP is added, determine CP position information and CP length information, and transmit the CP position information and CP length information to the transmitting device, so that the transmitting device may add the CP to the subsequent second OFDM symbol according to the CP position information and CP length information. Therefore, the receiving device can quickly and adaptively determine the CP position information and the CP length information of the OFDM symbols which are suitable for the OFDM communication system and are transmitted subsequently according to the OFDM symbols which are transmitted for the first time, eliminate the interference among the symbols, reduce the error rate of the system to the maximum extent and improve the stability of the OFDM communication system.

Step 302: the receiving device obtains equalization information for equalizing the first OFDM symbol by the receiving device, where the equalization information includes a plurality of tap positions and a tap coefficient corresponding to each tap position, and any one of the tap positions is used to indicate a delay time of one tap with respect to a specified time.

Step 303: and the receiving equipment determines CP position information and CP length information according to the equalization information, wherein the CP position information is used for indicating the position of a CP required to be added in a second subsequent OFDM symbol when the transmitting equipment adds the CP to the second subsequent OFDM symbol, and the CP length information comprises the CP length corresponding to the position indicated by the CP position information.

Optionally, when executing step 303, the receiving device specifically includes the following steps:

the receiving equipment sorts the tap coefficients corresponding to each tap position according to the order of the tap positions to generate a first queue;

the receiving equipment determines a first tap coefficient with the largest value in the first queue;

the receiving equipment acquires a tap threshold, sets a tap coefficient smaller than the tap threshold in the first queue to be 0, and generates a second queue; optionally, the tap threshold may be preset in the receiving device, or the receiving device may determine according to the first tap coefficient, for example, the receiving device obtains a threshold coefficient, and takes a product of the threshold coefficient and the first tap coefficient as the tap threshold;

the receiving device determines a second position of a second tap coefficient in the second queue and a third position of a third tap coefficient in the second queue, wherein the second tap coefficient is a tap coefficient which is first from left to right and is not 0 in the second queue, and the third tap coefficient is a tap coefficient which is first from right to left and is not 0 in the second queue;

and the receiving equipment determines the CP position information and the CP length information according to the first position, the second position and the third position of the first tap coefficient in the second queue.

As can be known from the discussion of the above method, the tap threshold is used to filter the tap coefficients in the first queue (the tap coefficients in the first queue that are smaller than the tap threshold are set to 0), where the tap threshold may affect the accuracy of the CP position information and the CP length information, and when the tap threshold is small, the tap coefficients filtered in the first queue are fewer, so that the CP length information finally determined according to the tap coefficients in the second queue is more accurate; when the value of the tap threshold is large, more tap coefficients are filtered out from the first queue, and therefore the accuracy of the CP length information finally determined according to the tap coefficients in the second queue is slightly poor. Optionally, when the accuracy of the CP length information required by the OFDM communication system is high, the tap threshold may be set to 0.

Optionally, the determining, by the receiving device, the CP location information and the CP length information according to the first location, the second location, and the third location includes:

the receiving equipment acquires sampling between any two adjacent taps for equalization processingSample interval T_eAnd a sampling interval T for the transmission of OFDM symbols by the transmission device_d；

The receiving device determines a difference between a value of the first position and a value of the second position as a first distance, and a difference between a value of the third position and a value of the second position as a second distance;

when the first distance is not 0, the receiving device determines that the CP position information comprises the front end of the data content, and the receiving device determines that the CP position information comprises the front end of the data content according to the first distance and the T_eAnd said T_dDetermining a second CP length corresponding to the front end of the data content included in the CP length information; when the first distance is 0, the receiving device determines that the CP position information does not include the front end of the data content;

when the second distance is not 0, the receiving device determines that the CP position information comprises the back end of the data content, and the receiving device determines that the CP position information comprises the back end of the data content according to the second distance and the T_eAnd said T_dDetermining a third CP length corresponding to the back end of the data content included in the CP length information; when the second distance is 0, the CP location information determined by the receiving device always does not include the back end of the data content.

Specifically, the second CP length complies with the following formula:

wherein S is₁Is the first distance;

the third CP length, according to the following formula:

wherein S is₂Is the second distance.

Since the receiving device can obtain the CP position information and the CP length information according to the tap characteristic of the equalization processing on the first OFDM symbol by the above method. Therefore, the determined CP position information and the CP length information are suitable for the OFDM communication system, so that the inter-symbol interference of subsequently transmitted OFDM symbols can be eliminated, the system error rate is effectively reduced, and the stability of the OFDM communication system is improved.

For example, after the receiving apparatus acquires 21 tap positions and corresponding tap coefficients, the receiving apparatus generates a first queue of [0.06, 0.001, 0.001, 0.03, 0.09, 0.11, 0.51, 0.13, 0.008, 0.02, 0.006, 0.002, 0.001, 0.005, 0.003, 0.007, 0.002, 0.001, 0.001, 0.002, 0.010] by sorting the tap coefficients corresponding to each tap position according to the order of the tap positions.

Obviously, the receiving device may determine, in the first queue, that the first tap coefficient with the largest value is 0.51;

in order to improve the accuracy of the CP length information, in this embodiment, the tap threshold is set to 0, so that the tap coefficients in the first queue are filtered according to the tap threshold, and the generated second queue is the same as the first queue;

the receiving device determines that the first tap coefficient 0.51 is 7 th at the first position in the second queue; determining that the first non-0 tap coefficient from left to right in the second queue is 0.06, and the second position in the second queue is the 1 st; determining that the tap coefficient of the first non-0 from right to left in the second queue is 0.010, and the third position in the second queue is the 21 st position;

the receiving device determines that the difference between the value (7) of the first position and the value (1) of the second position is 6, and determines that the difference between the value (21) of the third position and the value (7) of the first position is 14;

because the difference between the value (7) of the first position and the value (1) of the second position is not 0, the receiving device may determine that the CP position information includes the front end of the data content, and the CP length corresponding to the front end of the data content included in the CP length information is CP length

(ii) a Similarly, since the difference between the value (21) of the third position and the value (7) of the first position is not 0, the receiving device may determine that the CP position information includes the back end of the data content, and the CP length corresponding to the back end of the data content included in the CP length information is CP length

。

Step 304: and the receiving equipment sends the position information of the CP and the length information of the CP to the sending equipment.

Through the above steps, the receiving device sends the determined position information of the CP and the length information of the CP to the sending device, so that the sending device transmits the subsequent OFDM symbols according to the position information of the CP and the length information of the CP.

Optionally, after the receiving device acquires the first OFDM symbol, the method further includes:

the receiving device determines a channel quality parameter of each of a plurality of subcarriers carrying the first OFDM symbol, wherein the channel quality parameter of any one subcarrier includes any one or a combination of the following: BER, SNR;

the receiving device sends the determined channel quality parameter of each subcarrier in a plurality of subcarriers carrying the first OFDM symbol to the sending device, so that the sending device determines a modulation format corresponding to each subcarrier according to the channel quality parameter of each subcarrier in the plurality of subcarriers;

and the receiving equipment receives the modulation format corresponding to each subcarrier sent by the sending equipment.

In the foregoing case, the receiving device obtains a second OFDM symbol, where the second OFDM symbol requires the transmitting device to add a CP according to the CP location information and the CP length information before transmitting, and specifically includes the following steps:

the receiving equipment acquires a second analog signal;

the receiving equipment performs analog-to-digital conversion processing and synchronous processing on the second analog signal to generate second serial data;

the receiving equipment performs equalization processing and serial-parallel conversion processing on the second serial data to obtain a plurality of second time domain signals added with the CP;

the receiving equipment removes the CP from the plurality of second time domain signals added with the CP according to the CP position information and the CP length information to generate a plurality of second time domain signals removed with the CP;

the receiving device performs M-point Fourier transform and frequency domain equalization on the plurality of CP-removed second time domain signals to generate a plurality of second data, wherein the M is the same as the plurality of CP-removed second time domain signals in number;

the receiving device de-maps one second data in the plurality of second data carried in the corresponding subcarrier according to the modulation format corresponding to each subcarrier to generate a plurality of second parallel data;

and the receiving equipment performs parallel-to-serial conversion processing on the plurality of second parallel data to generate the second OFDM symbol.

Optionally, when a transmission medium of a channel between the sending device and the receiving device is an optical fiber, the obtaining, by the receiving device, the second analog signal includes:

the receiving equipment receives a second optical signal sent by the sending equipment through an optical fiber;

and the receiving equipment performs photoelectric conversion processing on the second optical signal to generate the second analog signal.

By adopting the OFDM symbol transmission method provided by the embodiment of the invention, in an OFDM communication system, when a sending device sends an OFDM symbol to a receiving device, a CP is added to a first OFDM symbol to be sent according to a preset first CP length, and the first OFDM symbol with the CP added is sent to the receiving device, so that the receiving device determines CP position information and CP length information according to the tap characteristic of equalization processing on the first OFDM symbol and feeds the CP position information and the CP length information back to the sending device; the transmitting device may add a CP to a subsequent OFDM symbol (a second OFDM symbol) according to the CP position information and the CP length information, and transmit the second OFDM symbol to which the CP is added to the receiving device. The CP position information is used to indicate a position where a CP needs to be added in a second subsequent OFDM symbol when the transmitting device adds the CP to the second subsequent OFDM symbol, and the CP length information includes a CP length corresponding to the position indicated by the CP position information. In this way, in the OFDM communication system, the receiving device can adaptively determine CP position information and CP length information of the OFDM symbols which are suitable for the subsequent transmission of the OFDM communication system according to the OFDM symbols which are transmitted in advance, so that the inter-symbol interference is eliminated, the system error rate is effectively reduced, and the stability of the OFDM communication system is improved; when the OFDM communication system changes, the receiving device can re-determine CP position information and CP length information suitable for the current OFDM communication system, manual configuration is not needed, maintenance cost is reduced, and stability of the OFDM communication system is further guaranteed; in addition, the determined CP position information and the determined CP length information in the method are not determined according to the maximum delay spread of the OFDM system, so the method is suitable for various OFDM communication systems and has strong applicability.

Fig. 4 shows a BER curve simulation diagram corresponding to two CP adding manners of adding a CP to an OFDM symbol by using a fixed CP length and adding a CP to the OFDM symbol by using a dynamic CP length in the same OFDM communication system, where the fixed CP length is 10 microseconds (10 data values) at both the front end and the rear end of the data content of the OFDM symbol, and the dynamic CP length is determined by a receiving device in the OFDM communication system according to a tap characteristic of equalizing the previously received OFDM symbol by using the method in the above embodiment. As can be seen from the figure, when the signal power of the OFDM symbol is the same, the BER of the dynamic CP length adding CP is lower than that of the fixed CP length adding CP, that is, the inter-symbol interference cancellation effect is better, so that the power margin of the dynamic CP length adding CP is higher at the same BER, and the power consumption of the OFDM communication system for transmitting the OFDM symbol is also reduced.

Based on the foregoing embodiment, an embodiment of the present invention further provides a sending apparatus, and referring to fig. 5, the sending apparatus 500 includes: a processing unit 501, a receiving unit 502, wherein,

a processing unit 501, configured to add a CP at a preset position in a first OFDM symbol according to a preset first cyclic prefix CP length, and send the first OFDM symbol with the CP added to a receiving device;

a receiving unit 502, configured to receive CP position information and CP length information sent by the receiving device, where the CP position information and the CP length information are determined by the receiving device according to the received first OFDM symbol after adding a CP, the CP position information is used to indicate a position where a CP needs to be added in a subsequent second OFDM symbol when the processing unit 501 adds a CP to the second OFDM symbol, and the CP length information includes a CP length corresponding to the position indicated by the CP position information;

the processing unit 501 is further configured to add a CP to the second OFDM symbol according to the CP position information and the CP length information, and send the second OFDM symbol after the CP is added to the receiving device.

Optionally, the processing unit 501 is specifically configured to:

after the first OFDM symbol is generated, performing serial-to-parallel conversion processing on the first OFDM symbol to generate a plurality of first parallel data, wherein each first parallel data in the plurality of first parallel data is carried on one subcarrier;

mapping the plurality of first parallel data into a plurality of first data of a preset first modulation format;

performing N-point inverse Fourier transform on the plurality of first data to generate a plurality of first time domain signals, wherein N is the same as the plurality of first parallel data;

adding a CP at the preset position of each first time domain signal in the plurality of first time domain signals according to the length of the first CP, and generating a plurality of CP-added first time domain signals;

and performing parallel-serial conversion processing on the plurality of first time domain signals added with the CP to generate first serial data, adding a synchronization sequence to the first serial data, performing digital-to-analog conversion processing to generate a first analog signal, and sending the first analog signal to the receiving equipment.

Optionally, the processing unit 501 is further configured to:

after the first OFDM symbol with the CP added is sent to the receiving device, acquiring a channel quality parameter of each subcarrier of a plurality of subcarriers carrying the first OFDM symbol before adding the CP to the second OFDM symbol according to the CP position information and a second CP length corresponding to a position indicated by the CP position information, where the channel quality parameter of any one subcarrier includes any one or a combination of the following: bit error rate BER, signal-to-noise ratio SNR;

determining a modulation format corresponding to each subcarrier according to the channel quality parameter of each subcarrier in the plurality of subcarriers;

when adding a CP to the second OFDM symbol according to the CP location information and the second CP length corresponding to the location indicated by the CP location information, and sending the second OFDM symbol after the CP is added to the receiving device, the processing unit 501 is specifically configured to:

performing serial-to-parallel conversion processing on the second OFDM symbol to generate a plurality of second parallel data, wherein each of the plurality of second parallel data is carried on one subcarrier;

determining a scheduling format corresponding to a subcarrier carrying each second parallel data in the plurality of second parallel data according to a modulation format corresponding to each subcarrier;

mapping each second parallel data in the plurality of second parallel data into second data of a scheduling format corresponding to a subcarrier carrying the corresponding second parallel data;

performing M-point inverse Fourier transform on a plurality of second data mapped by the plurality of second parallel data to generate a plurality of second time domain signals, wherein M is the same as the plurality of second parallel data in number;

adding a CP to each second time domain signal in the plurality of second time domain signals according to the CP position information and the CP length information to generate a plurality of CP-added second time domain signals;

and performing parallel-serial conversion processing on the plurality of second time domain signals added with the CP to generate second serial data, adding a synchronization sequence to the second serial data, performing digital-to-analog conversion processing to generate a second analog signal, and sending the second analog signal to the receiving equipment.

Optionally, the position that needs to be added in the second OFDM symbol indicated by the CP position information includes any one or a combination of the following: the front end of the data content, the back end of the data content.

Optionally, when the position indicated by the CP position information includes a front end of a data content, the processing unit 501, when adding a CP to each of the plurality of second time domain signals according to the CP position information and the CP length information, is specifically configured to:

selecting a first data content with a second CP length from the end position of the data content in a third time domain signal forward, wherein the third time domain signal is any one of the plurality of second time domain signals, and the second CP length is the CP length corresponding to the front end of the data content included in the CP length information;

and adding the selected first data content as the CP of the third time domain signal to the front end of the data content in the third time domain signal.

Optionally, when the position indicated by the CP position includes a back end of the data content, the processing unit 501, when adding a CP to each of the plurality of second time domain signals according to the CP position information and the CP length information, is specifically configured to:

selecting a second data content with a third CP length backward from the initial position of the data content in a fourth time domain signal, wherein the fourth time domain signal is any one of the plurality of second time domain signals, and the third CP length is a CP length corresponding to the rear end of the data content included in the CP length information;

and adding the selected second data content as the CP of the fourth time domain signal to the back end of the data content in the fourth time domain signal.

When the sending equipment sends the OFDM symbols to the receiving equipment in the OFDM communication system, adding a CP to a first OFDM symbol to be sent according to a preset first CP length, sending the first OFDM symbol added with the CP to the receiving equipment, so that the receiving equipment generates CP position information and CP length information according to the received first OFDM symbol added with the CP, and feeds the CP position information and the CP length information back to the sending equipment; the transmitting device may add a CP to a subsequent OFDM symbol (a second OFDM symbol) according to the CP position information and the CP length information, and transmit the second OFDM symbol to which the CP is added to the receiving device. The CP position information is used to indicate a position where a CP needs to be added in a second subsequent OFDM symbol when the transmitting device adds the CP to the second subsequent OFDM symbol, and the CP length information includes a CP length corresponding to the position indicated by the CP position information. In this way, in the OFDM communication system, the receiving device can adaptively determine CP position information and CP length information of the OFDM symbols which are suitable for the subsequent transmission of the OFDM communication system according to the OFDM symbols which are transmitted in advance, so that the inter-symbol interference is eliminated, the system error rate is effectively reduced, and the stability of the OFDM communication system is improved; when the OFDM communication system changes, the receiving device can re-determine CP position information and CP length information suitable for the current OFDM communication system, manual configuration is not needed, maintenance cost is reduced, and stability of the OFDM communication system is further guaranteed; in addition, the CP position information and the CP length information determined by the receiving device are not determined according to the maximum delay spread of the OFDM system, so the transmitting device and the receiving device are suitable for various OFDM communication systems and have strong applicability.

Based on the foregoing embodiments, an embodiment of the present invention further provides a receiving apparatus, and referring to fig. 6, the receiving apparatus 600 includes: a processing unit 601 and a sending unit 602, wherein,

a processing unit 601, configured to obtain a first orthogonal frequency division multiplexing OFDM symbol sent by a sending device, where the first OFDM symbol requires that the sending device add a CP at a preset position according to a preset first cyclic prefix CP length before sending;

acquiring equalization information for equalizing the first OFDM symbol by the receiving equipment, wherein the equalization information comprises a plurality of tap positions and tap coefficients corresponding to each tap position, and any tap position is used for representing the delay time of one tap relative to a specified time; and

according to the equalization information, determining Cyclic Prefix (CP) position information and CP length information, wherein the CP position information is used for indicating the position of a second OFDM symbol to which a CP needs to be added when the sending equipment adds the CP to the subsequent second OFDM symbol, and the CP length information comprises the CP length corresponding to the position indicated by the CP position information;

a sending unit 602, configured to send the location information of the CP and the length information of the CP to the sending device.

Optionally, when acquiring the first OFDM symbol, the processing unit 601 is specifically configured to:

acquiring a first analog signal;

performing analog-to-digital conversion processing and synchronous processing on the first analog signal to generate first serial data;

carrying out equalization processing and serial-parallel conversion processing on the first serial data to obtain a plurality of first time domain signals added with the CP;

removing the CP from the plurality of CP-added first time domain signals according to the length of the first CP and the preset position, and generating a plurality of CP-removed first time domain signals;

performing N-point Fourier transform and frequency domain equalization on the plurality of CP-removed first time domain signals to generate a plurality of first data, wherein N is the same as the number of the plurality of CP-removed first time domain signals;

according to a preset first adjustment format, demapping the first data to generate first parallel data;

and performing parallel-to-serial conversion processing on the plurality of first parallel data to generate the first OFDM symbol.

Optionally, when determining the CP location information and the CP length information according to the equalization information, the processing unit 601 is specifically configured to:

according to the sequence of the tap positions, sorting the tap coefficients corresponding to each tap position to generate a first queue;

determining a first tap coefficient with the largest value in the first queue;

acquiring a tap threshold, setting a tap coefficient smaller than the tap threshold in the first queue to be 0, and generating a second queue;

determining a second position of a second tap coefficient in the second queue and a third position of a third tap coefficient in the second queue, wherein the second tap coefficient is a tap coefficient which is first from left to right and is not 0, and the third tap coefficient is a tap coefficient which is first from right to left and is not 0 in the second queue;

and determining the CP position information and the CP length information according to the first position, the second position and the third position of the first tap coefficient in the second queue.

Optionally, when determining the CP location information and the CP length information according to the first location, the second location, and the third location, the processing unit 601 is specifically configured to:

acquiring sampling interval T between any two adjacent taps for equalization processing_eAnd a sampling interval T for the transmission of OFDM symbols by the transmission device_d；

Determining a difference between a value of the first position and a value of the second position as a first distance, and a difference between a value of the third position and a value of the second position as a second distance;

when the first distance is not 0, determining that the CP position information comprises the front end of the data content, and the receiving equipment determines that the CP position information comprises the front end of the data content according to the first distance and the T_eAnd said T_dDetermining a second CP length corresponding to the front end of the data content included in the CP length information;

when the second distance is not 0, determining that the CP position information comprises the back end of the data content, and the receiving equipment determines that the CP position information comprises the back end of the data content according to the second distance and the T_eAnd said T_dAnd determining a third CP length corresponding to the back end of the data content included in the CP length information.

Optionally, the second CP length conforms to the following formula:

wherein S is₁Is the first distance;

the third CP length, according to the following formula:

wherein S is₂Is the second distance.

Optionally, the processing unit 601 is further configured to determine, after obtaining the first OFDM symbol, a channel quality parameter of each subcarrier of a plurality of subcarriers carrying the first OFDM symbol, where the channel quality parameter of any one subcarrier includes any one or a combination of the following: bit error rate BER, signal-to-noise ratio SNR;

the sending unit 602 is further configured to send the determined channel quality parameter of each of the multiple subcarriers carrying the first OFDM symbol to the sending device;

the receiving device further comprises a receiving unit, configured to receive a modulation format corresponding to each subcarrier sent by the sending device;

the processing unit 601 is further configured to obtain a second OFDM symbol, where the second OFDM symbol requires the transmitting device to add a CP according to the CP location information and the CP length information before transmitting, and when obtaining the second OFDM symbol, the processing unit 601 is specifically configured to:

acquiring a second analog signal;

performing analog-to-digital conversion processing and synchronous processing on the second analog signal to generate second serial data;

performing equalization processing and serial-parallel conversion processing on the second serial data to obtain a plurality of second time domain signals added with the CP;

removing the CP from the plurality of second time domain signals added with the CP according to the CP position information and the CP length information to generate a plurality of second time domain signals removed with the CP;

performing M-point Fourier transform and frequency domain equalization on the plurality of CP-removed second time domain signals to generate a plurality of second data, wherein the M is the same as the plurality of CP-removed second time domain signals in number;

according to the modulation format corresponding to each subcarrier, one second data in the plurality of second data carried in the corresponding subcarrier is subjected to demapping to generate a plurality of second parallel data;

and performing parallel-to-serial conversion processing on the plurality of second parallel data to generate the second OFDM symbol.

By adopting the receiving equipment provided by the embodiment of the invention, in the OFDM communication system, the receiving equipment can self-adaptively determine the CP position information and the CP length information of the OFDM symbols which are suitable for the subsequent transmission of the OFDM communication system according to the OFDM symbols which are transmitted in advance, thereby eliminating the interference between the symbols, effectively reducing the error rate of the system and improving the stability of the OFDM communication system; when the OFDM communication system changes, the receiving device can re-determine CP position information and CP length information suitable for the current OFDM communication system, manual configuration is not needed, maintenance cost is reduced, and stability of the OFDM communication system is further guaranteed; in addition, the CP position information and the CP length information determined by the receiving device are not determined according to the maximum delay spread of the OFDM system, so the transmitting device and the receiving device are suitable for various OFDM communication systems and have strong applicability.

It should be noted that the division of the unit in the embodiment of the present invention is schematic, and is only a logic function division, and there may be another division manner in actual implementation. The functional units in the embodiments of the present application may be integrated into one processing unit, or each unit may exist alone physically, or two or more units are integrated into one unit. The integrated unit can be realized in a form of hardware, and can also be realized in a form of a software functional unit.

The integrated unit, if implemented in the form of a software functional unit and sold or used as a stand-alone product, may be stored in a computer readable storage medium. Based on such understanding, the technical solution of the present application may be substantially implemented or contributed by the prior art, or all or part of the technical solution may be embodied in a software product, which is stored in a storage medium and includes instructions for causing a computer device (which may be a personal computer, a server, a network device, or the like) or a processor (processor) to execute all or part of the steps of the method according to the embodiments of the present application. And the aforementioned storage medium includes: various media capable of storing program codes, such as a usb disk, a removable hard disk, a Read-Only Memory (ROM), a Random Access Memory (RAM), a magnetic disk, or an optical disk.

Based on the above embodiments, an embodiment of the present invention further provides a transmitting apparatus, where the transmitting apparatus is applied to an OFDM communication system shown in fig. 1, and referring to fig. 7, the transmitting apparatus 700 includes: a transceiver 701, a processor 702, a bus 703, and a memory 704, wherein,

the transceiver 701, the processor 702, and the memory 704 are connected to each other through the bus 703; the bus 703 may be a Peripheral Component Interconnect (PCI) bus, an Extended Industry Standard Architecture (EISA) bus, or the like. The bus may be divided into an address bus, a data bus, a control bus, etc. For ease of illustration, only one thick line is shown in FIG. 7, but this is not intended to represent only one bus or type of bus.

The transceiver 701 is configured to perform communication interaction with a receiving device in the OFDM communication system.

The processor 702 is configured to implement the OFDM symbol transmission method shown in fig. 2, and includes:

adding a CP at a preset position in a first Orthogonal Frequency Division Multiplexing (OFDM) symbol according to a preset first Cyclic Prefix (CP) length, and sending the first OFDM symbol added with the CP to a receiving device;

receiving CP position information and CP length information sent by the receiving device, where the CP position information and the CP length information are determined by the receiving device according to the received first OFDM symbol after adding a CP, the CP position information is used to indicate a position where the CP needs to be added in a subsequent second OFDM symbol when the processor 702 adds a CP to the second OFDM symbol, and the CP length information includes a CP length corresponding to the position indicated by the CP position information;

and adding a CP to the second OFDM symbol according to the CP position information and the CP length information, and sending the second OFDM symbol after the CP is added to the receiving equipment.

A memory 704 for storing programs and the like. In particular, the program may include program code comprising computer operating instructions. The memory 704 may include a Random Access Memory (RAM) and may also include a non-volatile memory (non-volatile memory), such as at least one disk memory. The processor 702 executes the application program stored in the memory 704 to implement the above-described functions, thereby implementing the OFDM symbol transmission method shown in fig. 2.

Based on the above embodiments, an embodiment of the present invention further provides a receiving device, where the receiving device is applied to an OFDM communication system shown in fig. 1, and referring to fig. 8, the receiving device 800 includes: a transceiver 801, a processor 802, a bus 803, and a memory 804, wherein,

the transceiver 801, the processor 802 and the memory 804 are connected to each other by the bus 803; the bus 803 may be a Peripheral Component Interconnect (PCI) bus, an Extended Industry Standard Architecture (EISA) bus, or the like. The bus may be divided into an address bus, a data bus, a control bus, etc. For ease of illustration, only one thick line is shown in FIG. 8, but this is not intended to represent only one bus or type of bus.

The transceiver 801 is configured to perform communication interaction with a sending device in the OFDM communication system.

The processor 802 is configured to implement the OFDM symbol transmission method shown in fig. 3, and includes:

acquiring a first Orthogonal Frequency Division Multiplexing (OFDM) symbol sent by sending equipment, wherein the first OFDM symbol requires the sending equipment to add a Cyclic Prefix (CP) at a preset position according to a preset CP length of a first CP before sending;

acquiring equalization information for equalizing the first OFDM symbol by the receiving equipment, wherein the equalization information comprises a plurality of tap positions and tap coefficients corresponding to each tap position, and any tap position is used for representing the delay time of one tap relative to a specified time;

and sending the position information of the CP and the length information of the CP to the sending equipment.

A memory 804 for storing programs and the like. In particular, the program may include program code comprising computer operating instructions. The memory 804 may include a Random Access Memory (RAM) and may also include a non-volatile memory (non-volatile memory), such as at least one disk memory. The processor 802 executes the application program stored in the memory 804 to implement the above-described functions, thereby implementing the OFDM symbol transmission method shown in fig. 3.

In summary, the OFDM symbol transmission method and apparatus provided in the embodiments of the present invention are: the method comprises the steps that a sending device sends a first OFDM symbol added with a CP according to a preset first CP length to a receiving device, the receiving device generates and feeds back CP position information and CP length information to the sending device according to the first OFDM symbol, and the sending device adds the CP to a subsequent OFDM symbol according to the CP position information and the CP length information. Therefore, the receiving equipment can self-adaptively determine the CP position information and the CP length information of the OFDM symbols which are suitable for the subsequent transmission of the OFDM communication system according to the OFDM symbols which are transmitted in advance, eliminate the inter-symbol interference, effectively reduce the system error rate and improve the stability of the OFDM communication system; when the OFDM communication system changes, the receiving device can re-determine CP position information and CP length information suitable for the current OFDM communication system, manual configuration is not needed, maintenance cost is reduced, and stability of the OFDM communication system is further guaranteed; in addition, the determined CP position information and the determined CP length information in the method are not determined according to the maximum delay spread of the OFDM system, so the method is suitable for various OFDM communication systems and has strong applicability.

As will be appreciated by one skilled in the art, embodiments of the present invention may be provided as a method, system, or computer program product. Accordingly, the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present invention may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein.

The present invention is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each flow and/or block of the flow diagrams and/or block diagrams, and combinations of flows and/or blocks in the flow diagrams and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.

These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.

These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.

While preferred embodiments of the present invention have been described, additional variations and modifications in those embodiments may occur to those skilled in the art once they learn of the basic inventive concepts. Therefore, it is intended that the appended claims be interpreted as including preferred embodiments and all such alterations and modifications as fall within the scope of the invention.

It will be apparent to those skilled in the art that various modifications and variations can be made in the embodiments of the present invention without departing from the spirit or scope of the embodiments of the invention. Thus, if such modifications and variations of the embodiments of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to encompass such modifications and variations.

Claims

1. An OFDM symbol transmission method, comprising:

the method comprises the steps that a sending device adds a CP at a preset position in a first Orthogonal Frequency Division Multiplexing (OFDM) symbol according to a preset first Cyclic Prefix (CP) length, and sends the first OFDM symbol added with the CP to a receiving device;

the sending device receives CP position information and CP length information sent by the receiving device, wherein the CP position information and the CP length information are determined by the receiving device according to the received first OFDM symbol added with the CP, the CP position information is used for indicating the position of the second OFDM symbol to which the CP needs to be added when the sending device adds the CP to the subsequent second OFDM symbol, and the CP length information comprises the CP length corresponding to the position indicated by the CP position information;

and the sending equipment adds the CP to the second OFDM symbol according to the CP position information and the CP length information, and sends the second OFDM symbol after the CP is added to the receiving equipment.

2. The method of claim 1, wherein the transmitting device adds a CP to a preset position in a first OFDM symbol according to the first CP length, and transmits the first OFDM symbol to which the CP is added to the receiving device, comprising:

3. The method according to claim 1 or 2, wherein after the transmitting device transmits the first OFDM symbol to which the CP is added to the receiving device, before the transmitting device adds the CP to the second OFDM symbol according to the CP location information and a second CP length corresponding to a location indicated by the CP location information, the method further comprises:

the sending device obtains a channel quality parameter of each subcarrier of a plurality of subcarriers carrying the first OFDM symbol, and the channel quality parameter of any one subcarrier includes any one or a combination of the following: bit error rate BER, signal-to-noise ratio SNR;

the sending equipment determines a modulation format corresponding to each subcarrier according to the channel quality parameter of each subcarrier in the plurality of subcarriers;

4. The method of claim 3, wherein the positions required to be added in the second OFDM symbol indicated by the CP position information include any one or a combination of the following: the front end of the data content, the back end of the data content.

5. The method of claim 4, wherein when the position indicated by the CP location information includes a front end of data content, the transmitting device adding a CP to each of the plurality of second time domain signals according to the CP location information and the CP length information, comprising:

and the sending equipment takes the selected first data content as the CP of the third time domain signal and adds the CP to the front end of the data content in the third time domain signal.

6. The method of claim 4 or 5, wherein when the position indicated by the CP position comprises a back end of data content, the sending device adding a CP to each of the plurality of second time domain signals according to the CP position information and the CP length information, comprising:

and the sending equipment takes the selected second data content as the CP of the fourth time domain signal and adds the CP to the back end of the data content in the fourth time domain signal.

7. An OFDM symbol transmission method, comprising:

the method comprises the steps that a receiving device obtains a first Orthogonal Frequency Division Multiplexing (OFDM) symbol sent by a sending device, wherein the first OFDM symbol requires the sending device to add a Cyclic Prefix (CP) at a preset position according to a preset CP length of a first CP before sending;

the receiving device obtains equalization information for equalizing the first OFDM symbol by the receiving device, wherein the equalization information comprises a plurality of tap positions and tap coefficients corresponding to each tap position, and any one tap position is used for representing the delay time of one tap relative to a specified time;

the receiving device determines Cyclic Prefix (CP) position information and CP length information according to the equalization information, wherein the CP position information is used for indicating the position of a second OFDM symbol to which a CP needs to be added when the transmitting device adds the CP to the subsequent second OFDM symbol, and the CP length information comprises the CP length corresponding to the position indicated by the CP position information; wherein, the determining, by the receiving device, the CP location information and the CP length information according to the equalization information includes: the receiving equipment sorts the tap coefficients corresponding to each tap position according to the order of the tap positions to generate a first queue; the receiving equipment determines a first tap coefficient with the largest value in the first queue; the receiving equipment acquires a tap threshold, sets a tap coefficient smaller than the tap threshold in the first queue to be 0, and generates a second queue; the receiving device determines a second position of a second tap coefficient in the second queue and a third position of a third tap coefficient in the second queue, wherein the second tap coefficient is a tap coefficient which is first from left to right and is not 0 in the second queue, and the third tap coefficient is a tap coefficient which is first from right to left and is not 0 in the second queue; the receiving device determines the CP position information and the CP length information according to the first position, the second position and the third position of the first tap coefficient in the second queue;

and the receiving equipment sends the position information of the CP and the length information of the CP to the sending equipment.

8. The method of claim 7, wherein the receiving device obtaining the first OFDM symbol comprises:

the receiving equipment acquires a first analog signal;

the receiving equipment performs equalization processing and serial-parallel conversion processing on the first serial data to obtain a plurality of first time domain signals added with the CP;

9. The method of claim 7, wherein the determining, by the receiving device, the CP location information and the CP length information based on the first location, the second location, and the third location comprises:

the receiving equipment acquires the sampling interval T between any two adjacent taps for equalization processing_eAnd a sampling interval T for the transmission of OFDM symbols by the transmission device_d；

when the first distance is not 0, the receiving device determines that the CP position information comprises the front end of the data content, and the receiving device determines that the CP position information comprises the front end of the data content according to the first distance and the T_eAnd said T_dDetermining a second CP length corresponding to the front end of the data content included in the CP length information;

when the second distance is not 0, the receiving device determines that the CP position information comprises the back end of the data content, and the receiving device determines that the CP position information comprises the back end of the data content according to the second distance and the T_eAnd said T_dAnd determining a third CP length corresponding to the back end of the data content included in the CP length information.

10. The method of claim 9, wherein the second CP length complies with the following formula:

wherein S is₁Is the first distance;

the third CP length, according to the following formula:

wherein S is₂Is the second distance.

11. The method of any of claims 7-10, wherein after the receiving device acquires the first OFDM symbol, further comprising:

the receiving device determines a channel quality parameter of each of a plurality of subcarriers carrying the first OFDM symbol, wherein the channel quality parameter of any one subcarrier includes any one or a combination of the following: bit error rate BER, signal-to-noise ratio SNR;

the receiving equipment sends the determined channel quality parameters of each subcarrier in a plurality of subcarriers carrying the first OFDM symbol to the sending equipment;

the receiving equipment receives the modulation format corresponding to each subcarrier sent by the sending equipment;

the receiving device obtains a second OFDM symbol, where the second OFDM symbol requires the transmitting device to add a CP according to the CP location information and the CP length information before transmission, and the method specifically includes:

the receiving equipment acquires a second analog signal;

12. A transmitting device, comprising:

the processing unit is used for adding a CP at a preset position in a first OFDM (orthogonal frequency division multiplexing) symbol according to the length of a preset first Cyclic Prefix (CP), and sending the first OFDM symbol added with the CP to receiving equipment;

a receiving unit, configured to receive CP position information and CP length information sent by the receiving device, where the CP position information and the CP length information are determined by the receiving device according to the received first OFDM symbol to which a CP is added, the CP position information is used to indicate a position to which a CP needs to be added in a second subsequent OFDM symbol when the processing unit adds a CP to the second OFDM symbol, and the CP length information includes a CP length corresponding to the position indicated by the CP position information;

the processing unit is further configured to add a CP to the second OFDM symbol according to the CP location information and the CP length information, and send the second OFDM symbol after the CP is added to the receiving device.

13. The sending device of claim 12, wherein the processing unit is specifically configured to:

14. The transmitting device of claim 12 or 13, wherein the processing unit is further configured to:

the processing unit, when adding a CP to the second OFDM symbol according to the CP location information and a second CP length corresponding to a location indicated by the CP location information, and sending the second OFDM symbol after the CP is added to the receiving device, is specifically configured to:

15. The transmitting device of claim 14, wherein the position to be added in the second OFDM symbol indicated by the CP position information includes any one or a combination of: the front end of the data content, the back end of the data content.

16. The transmitting device according to claim 15, wherein when the position indicated by the CP position information includes a front end of data content, the processing unit, when adding a CP to each of the plurality of second time domain signals according to the CP position information and the CP length information, is specifically configured to:

17. The transmitting device according to claim 15 or 16, wherein when the position indicated by the CP position includes a back end of data content, the processing unit, when adding a CP to each of the plurality of second time domain signals according to the CP position information and the CP length information, is specifically configured to:

18. A receiving device, comprising:

a processing unit, configured to obtain a first orthogonal frequency division multiplexing OFDM symbol sent by a sending device, where the first OFDM symbol requires that a CP be added at a preset position by the sending device according to a preset first cyclic prefix CP length before sending;

according to the equalization information, determining Cyclic Prefix (CP) position information and CP length information, wherein the CP position information is used for indicating the position of a second OFDM symbol to which a CP needs to be added when the sending equipment adds the CP to the subsequent second OFDM symbol, and the CP length information comprises the CP length corresponding to the position indicated by the CP position information; wherein, when determining the CP location information and the CP length information according to the equalization information, the processing unit is specifically configured to: according to the sequence of the tap positions, sorting the tap coefficients corresponding to each tap position to generate a first queue; determining a first tap coefficient with the largest value in the first queue; acquiring a tap threshold, setting a tap coefficient smaller than the tap threshold in the first queue to be 0, and generating a second queue; determining a second position of a second tap coefficient in the second queue and a third position of a third tap coefficient in the second queue, wherein the second tap coefficient is a tap coefficient which is first from left to right and is not 0, and the third tap coefficient is a tap coefficient which is first from right to left and is not 0 in the second queue; determining the CP position information and the CP length information according to the first position, the second position and the third position of the first tap coefficient in the second queue;

a sending unit, configured to send the location information of the CP and the length information of the CP to the sending device.

19. The receiving device of claim 18, wherein the processing unit, when obtaining the first OFDM symbol, is specifically configured to:

acquiring a first analog signal;

20. The receiving device of claim 18, wherein the processing unit, when determining the CP location information and the CP length information according to the first location, the second location, and the third location, is specifically configured to:

acquisition of sampling between any two adjacent taps for equalizationSample interval T_eAnd a sampling interval T for the transmission of OFDM symbols by the transmission device_d；

21. The receiving device of claim 20, wherein the second CP length complies with the following formula:

wherein S is₁Is the first distance;

the third CP length, according to the following formula:

wherein S is₂Is the second distance.

22. The receiving device of any of claims 18-21,

the processing unit is further configured to determine, after obtaining the first OFDM symbol, a channel quality parameter of each of a plurality of subcarriers carrying the first OFDM symbol, where the channel quality parameter of any one subcarrier includes any one or a combination of the following: bit error rate BER, signal-to-noise ratio SNR;

the sending unit is further configured to send the determined channel quality parameter of each of the multiple subcarriers carrying the first OFDM symbol to the sending device;

the processing unit is further configured to acquire a second OFDM symbol, where the second OFDM symbol requires the transmitting device to add a CP according to the CP location information and the CP length information before transmitting, and when acquiring the second OFDM symbol, the processing unit is specifically configured to:

acquiring a second analog signal;