JP4152370B2 - Diversity method and apparatus - Google Patents

Description

  The present invention relates to diversity technology, and more particularly to a diversity method and apparatus for combining two received signals.

An OFDM (Orthogonal Frequency Division Multiplexing) modulation scheme, which is one of the multicarrier schemes, is a communication scheme that enables high-speed data transmission and is strong in a multipath environment. This OFDM modulation method is applied to IEEE802.11a, g and HIPERLAN / 2, which are standardization standards for wireless LANs. A signal received in such a wireless LAN generally passes through a transmission path environment that fluctuates with time, and is affected by frequency selective fading. Therefore, the receiving apparatus should dynamically perform transmission path estimation. Two types of known signals are provided for the receiving apparatus to perform transmission path estimation. One is a known signal provided for all carriers at the head of the burst signal, which is a so-called preamble or training signal. The other is a known signal provided for a part of the carriers in the data section of the burst signal, which is a so-called pilot signal (see, for example, Non-Patent Document 1).
Sine Coleri, Mustafa Ergen, Anuj Puri, and Ahmad Bahai, “Channel Estimation Techniques Based on Pilot Arrangement in OFDM Systems”, IbnEnts. 48, no. 3, pp. 223-229, Sept. 2002.

  In the field of wireless communication, the spread spectrum communication system (SS) has been studied conventionally. The spread spectrum communication system includes a direct spread system (DS) and a frequency hopping system (FH). In the FH system, spread spectrum communication is performed by hopping the frequency of a carrier wave one after another based on a code sequence. For this reason, the spectrum distribution in the FH system occupies a wide band when observed for a long time, but is a signal that occupies only a specific frequency band when observed in units of one bit or symbol, and is narrower than the DS system. It is a serious signal. Therefore, since it can be said that it is an interference avoidance type SS, there is an advantage that the probability that a plurality of users communicate at the same timing and at the same frequency is reduced.

  An MB-OFDM method combining such an FH method and the above-described OFDM modulation method has been proposed, and this is applied to WPAN (Wireless Personal Area Network). WPAN is a wireless network in a narrower range than a wireless LAN, and is a short-range wireless network between PDAs and peripheral devices. Further, in UWB (Ultra Wideband) using such an MB-OFDM modulation scheme, use of a band from 3.1 GHz to 10.6 GHz is planned.

  The MB-OFDM modulation scheme applied to WPAN supports multiple types of data transmission rates. Under such circumstances, when the data transmission rate is low, the same symbol is transmitted continuously. The signal strength and signal-to-noise ratio for each of the symbols transmitted in succession may be different. In such a case, if those symbols are synthesized as they are, the symbol having the lower signal strength or signal-to-noise ratio has an effect, so that the synthesis gain is lowered.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a diversity method and apparatus that suppresses a decrease in the combined gain of symbols when the same symbol is transmitted and the quality of the symbols is different. It is to be.

  In order to solve the above problems, a diversity apparatus according to an aspect of the present invention includes an input unit that inputs a signal in which a symbol having the same content is repeated a predetermined number of times, and a symbol having the same content that is repeated a predetermined number of times. A derivation unit for deriving a number of weighting factors according to a predetermined number of times while reflecting the corresponding signal strength, a number of weighting factors according to a predetermined number of times, and a symbol having the same content repeated a predetermined number of times And a combining unit that combines the symbols having the same content after weighting the symbols having the same content by weighting coefficients corresponding to a predetermined number of times.

  According to this aspect, since the weighting factor corresponding to each of the same content symbols repeated a predetermined number of times reflects the signal strength for each of the same content symbols, the quality of one of the same content symbols is low. Even in this case, it is possible to suppress a decrease in the combined gain of the symbols.

  The derivation unit may update the weighting factor in symbol units while reflecting the signal strength in symbol units. In this case, it is possible to derive a weighting factor that follows fluctuations in the wireless transmission path.

  The signal input to the input unit is frequency hopped, and the derivation unit derives a weighting factor for each hopping frequency while reflecting the signal strength corresponding to each of a plurality of hopping frequencies defined in the frequency hopping. May be. In this case, a weighting factor corresponding to frequency hopping can be derived.

  The signal input to the input unit is a burst signal including a plurality of symbols, and the deriving unit may derive a weighting factor for each hopping frequency in a partial period of the burst signal. In this case, it is only necessary to derive the weighting coefficient during a partial period of the burst signal, so that the processing period can be shortened.

  Another aspect of the present invention is also a diversity apparatus. The apparatus is configured to input a signal in which a symbol having the same content is repeated a predetermined number of times, and a signal-to-noise ratio corresponding to each of the symbols having the same content that is repeated a predetermined number of times. The number corresponding to the predetermined number of times, the deriving unit for deriving the number of weighting factors corresponding to each, the number of weighting factors corresponding to the predetermined number of times, and the symbols having the same contents repeated a predetermined number of times And a combining unit that combines the symbols having the same content after weighting the symbols having the same content by the weighting coefficient. Among the signals input to the input unit, one symbol is formed by a transmission interval and a non-transmission interval, and the derivation unit determines the signal from the signal strength in the transmission interval and the non-transmission interval in one symbol. Deriving the noise-to-noise ratio.

  The “transmitted section” indicates a section in which the transmission apparatus transmits some signal, and the “non-transmission section” indicates a section in which the transmission apparatus does not transmit a signal. Since these sections need only be specified in the transmission apparatus, the reception apparatus may not receive a signal in the “transmitted section” or may receive a signal in the “non-transmission section”. .

  According to this aspect, since the weighting factor corresponding to each of the same content symbols repeated a predetermined number of times reflects the signal-to-noise ratio corresponding to each of the same content symbols, the quality of one of the same content symbols is improved. Even when the value is low, it is possible to suppress a decrease in the combined gain of symbols.

  Of the signals input to the input unit, one symbol uses a plurality of carriers, and the combining unit may combine symbols having the same content in units of the plurality of carriers. In this case, a multicarrier signal can also be handled.

  Yet another embodiment of the present invention is a diversity method. This method inputs a signal in which a symbol having the same content is repeated a predetermined number of times, and reflects the signal intensity corresponding to each of the symbols having the same content repeated a predetermined number of times, while corresponding to each symbol having the same content. A weighting factor is derived, symbols having the same content are weighted by the weighting factor, and then symbols having the same content are synthesized.

  Yet another embodiment of the present invention is also a diversity method. This method is a signal in which a symbol having the same content is repeated a predetermined number of times, and a signal including a symbol formed by a transmission section and a non-transmission section is input, and the signal having the same content is repeated a predetermined number of times. The signal-to-noise ratio corresponding to each of the symbols, and corresponding to each symbol of the same content while reflecting the signal-to-noise ratio calculated from the signal strength in the transmission and non-transmission intervals in one symbol The weighting coefficients obtained are derived, the symbols having the same contents are weighted by the weighting coefficients, and then the symbols having the same contents are synthesized.

  Yet another embodiment of the present invention is also a diversity method. A step of inputting a signal in which a symbol having the same content is repeated a predetermined number of times, and a weighting coefficient corresponding to the predetermined number of times while reflecting the signal intensity corresponding to each of the symbols having the same content repeated a predetermined number of times. , Respectively, and a number of weighting factors corresponding to a predetermined number of times and a symbol of the same content repeated by a predetermined number of times, and a number of weighting factors corresponding to the predetermined number of times. Each of which is weighted, and then synthesizing symbols having the same content.

  In the deriving step, the weighting factor may be updated in symbol units while reflecting the signal strength in symbol units. The signal input to the input step is frequency hopped, and the derivation step sets the weighting factor of the hopping frequency unit while reflecting the signal strength corresponding to each of a plurality of hopping frequencies defined in the frequency hopping. Each may be derived. The signal input to the inputting step is a burst signal including a plurality of symbols, and the deriving step may derive a weighting factor for each hopping frequency in a partial period of the burst signal.

  Yet another embodiment of the present invention is also a diversity method. The step of inputting a signal in which a symbol having the same content is repeated a predetermined number of times and a signal-to-noise ratio corresponding to each of the symbol having the same content repeated a predetermined number of times are reflected in a number corresponding to the predetermined number of times. Each step of deriving a weighting factor, a number of weighting factors corresponding to a predetermined number of times, and a symbol having the same content repeated a predetermined number of times are associated with the same content by the number of weighting factors corresponding to the predetermined number of times. And synthesizing symbols having the same contents after weighting each of the symbols. Of the signals input to the input step, one symbol is formed by a transmission interval and a non-transmission interval, and the deriving step is based on the signal strength in the transmission interval and the non-transmission interval in one symbol. Deriving the signal-to-noise ratio.

  In the deriving step, the weighting factor may be updated in symbol units while reflecting the signal-to-noise ratio in symbol units. The signal input to the input step is frequency hopped, and the step of deriving is a weight for each hopping frequency while reflecting a signal-to-noise ratio corresponding to each of a plurality of hopping frequencies defined in the frequency hopping. Each coefficient may be derived. The signal input to the inputting step is a burst signal including a plurality of symbols, and the deriving step may derive a weighting factor for each hopping frequency in a partial period of the burst signal. Of the signals input to the input step, one symbol uses a plurality of carriers, and the combining step may combine symbols having the same content in units of the plurality of carriers. .

  It should be noted that any combination of the above-described constituent elements and a conversion of the expression of the present invention between a method, an apparatus, a system, a recording medium, a computer program, etc. are also effective as an aspect of the present invention.

  ADVANTAGE OF THE INVENTION According to this invention, when the same symbol is transmitted and the quality of those symbols differs, the fall of the synthetic gain of a symbol can be suppressed.

  Before describing the present invention in detail, an outline will be described. Embodiments of the present invention relate to a receiving apparatus in a communication system in which frequency hopping is performed on a symbol basis. The OFDM modulation scheme is applied to the frequency hopped symbols, and the communication system according to the embodiment targets UWB to which the MB-OFDM modulation scheme is applied. In the communication system according to the present embodiment, symbols having the same contents are transmitted in two consecutive symbols. Therefore, symbols having the same content are transmitted at different times and at different frequencies. When the receiving apparatus demodulates the received signal, it combines the symbols having the same content to obtain a diversity effect. At that time, a signal-to-noise ratio (hereinafter referred to as “SNR (Signal to Noise Ratio)”) corresponding to two symbols having the same content is derived, and a weighting coefficient is derived from the SNR. The receiving apparatus weights the symbols having the same content by weighting factors corresponding to the symbols, and then synthesizes the symbols having the same content.

  FIG. 1 shows a configuration of a receiving apparatus 100 according to an embodiment of the present invention. The receiving apparatus 100 includes an antenna 10, a radio unit 12, a baseband processing unit 14, and a control unit 16.

  The antenna 10 receives a signal from a transmission device (not shown) via a wireless section. An OFDM modulation scheme and an FH scheme are applied to the received signal. Each subcarrier is phase-modulated by QPSK (Quadrature Phase Shift Keying). Further, an OFDM symbol which is one unit in the OFDM modulation scheme is frequency hopped by a predetermined hopping pattern. Here, the OFDM symbol will be described later. The received signal has a predetermined radio frequency.

  The radio unit 12 converts the radio frequency signal received by the antenna 10 into a baseband signal. The radio unit 12 includes a code generator for performing frequency hopping according to a predetermined hopping pattern, and a pseudo-random code signal generated from the code generator is a hopping pattern in a received radio frequency signal. Synchronized with. The code generator performs synchronization with the hopping pattern on the received radio frequency signal by a predetermined method. Since the baseband signal includes in-phase components and quadrature components, it should generally be indicated by two signal lines. Here, for the sake of clarity, the signal is indicated by one signal line. And The same applies to the following.

  The baseband processing unit 14 demodulates the baseband signal input from the wireless unit 12. Since the OFDM modulation scheme is applied to the baseband signal, the baseband processing unit 14 performs FFT (Fast Fourier Transform) on the baseband signal. Further, as will be described in detail later, since two consecutive OFDM symbols have the same content, the baseband processing unit 14 performs diversity processing on these signals. Further, the baseband processing unit 14 performs demapping processing corresponding to QPSK, and then performs deinterleaving processing to perform decoding. Corresponding to this, interleaving and encoding are performed in a transmitting apparatus (not shown).

  The control unit 16 controls the entire receiving apparatus 100 so that the receiving apparatus 100 can execute a predetermined process. In particular, the control unit 16 controls timing in the receiving device 100.

  FIG. 2 shows a hopping frequency of a signal received by receiving apparatus 100. Here, for simplification of explanation, two frequencies of “band 1” and “band 2” are used as shown in the figure. The signal in “Band 1” is further OFDM modulated. Since the communication system in the present embodiment uses frequency hopping, it switches between “band 1” and “band 2” at a predetermined timing. Here, for simplification of explanation, “band 1” and “band 2” are used alternately. That is, hopping patterns such as “Band 1”, “Band 2”, “Band 1”, and “Band 2” are used.

  FIGS. 3A to 3C show symbol configurations of signals received by the receiving apparatus 100. FIG. FIG. 3A shows a signal (hereinafter referred to as “IFFT signal”) subjected to IFFT in the transmission apparatus. In the transmission apparatus, the frequency domain signal is IFFT and converted into a time domain signal. Here, the IFFT of the transmission device and the FFT of the reception device are both executed as a unit, that is, as an FFT window (hereinafter, the timing corresponding to one of the 128 data is referred to as “FFT point”). "). FIG. 3A shows the data of 128 FFT points as “D1”, “D2”, “D3”, and “D4” in order from the front.

  FIG. 3B shows a signal obtained by adding a guard interval (GI) to the IFFT signal shown in FIG. As shown in the drawing, “GI” is added to the back of each of “D1”, “D2”, “D3”, and “D4”, which is data of 128 FFT points. Here, “GI” corresponds to a portion where no signal is transmitted, that is, a non-transmission section. Further, a combination of 128 FFT point data and “GI” is referred to as the “OFDM symbol” described above. For example, “D1” and “GI” correspond to one OFDM symbol. The same applies to “D2”, “D3”, and “D4”.

  As described above, since the frequency hopping is performed while the hopping frequency is alternately switched in units of one OFDM symbol, the first “D1” and “GI” are transmitted by “band 1” as illustrated. The next “D2” and “GI” are transmitted by “Band 2”. Further, the next “D3” and “GI” are transmitted by “band 1”, and “D4” and “GI” are further transmitted by “band 2”. Hereinafter, the “OFDM symbol” is used not only for the time domain signal as shown, but also for the frequency domain signal. When “OFDM symbols” are used for frequency domain signals, “GI” may be excluded.

  FIG. 3C shows a signal obtained by adding GI to the IFFT signal as in FIG. However, FIG. 3C corresponds to the case of a data transmission rate lower than the data transmission rate of FIG. 3B among a plurality of data transmission rates defined in UWB. Since “D1” and “D1 ′” in the figure have the same content, and “D2” and “D2 ′” have the same content, the OFDM symbols having the same content are transmitted in two consecutive OFDM symbols. . Thus, since two OFDM symbols having the same contents are transmitted in succession, the data transmission rate is halved, but the effect of time diversity is obtained. Furthermore, since the hopping frequencies of two OFDM symbols transmitted in succession are different, the effect of frequency diversity can also be obtained. For example, “D1” and “GI” are transmitted by “band 1”, and “D1 ′” and “GI” are transmitted by “band 2”. Note that the receiving apparatus 100 in FIG. 1 processes a signal having the format of FIG. 3C.

  4A to 4B show waveforms of signals received by the receiving apparatus 100. FIG. FIG. 4A shows a waveform of a signal corresponding to FIG. 3B or FIG. As shown in the figure, the OFDM symbol is formed by repeating a transmission / reception period corresponding to the IFFT signal and a non-transmission period corresponding to the GI. FIG. 4B shows a signal waveform when the signal of FIG. 4A is received by the antenna 10 through the wireless transmission path. Since a delayed wave is generated in the wireless transmission path, the antenna 10 receives a predetermined signal even in the GI section. However, the signal strength in the GI section is smaller than that in the IFFT signal section.

  FIG. 5 shows a burst format of a signal received by receiving apparatus 100. In the burst signal, “preamble”, “header”, and “data” are arranged from the head. “Preamble”, “header”, and “data” are each formed by a predetermined number of OFDM symbols or IFFT signals. In these, a predetermined modification may be added to the OFDM symbol or the IFFT signal. The “preamble” is a known signal used by the receiving apparatus 100 when the receiving apparatus 100 executes timing synchronization and transmission path estimation. “Header” is a control signal, and “data” is information to be transmitted from a transmission device (not shown).

  FIG. 6 shows the configuration of the baseband processing unit 14. The baseband processing unit 14 includes a delay symbol synthesis unit 20, a symbol timing synchronization unit 22, a derivation unit 24, an FFT 26, an equalization unit 28, a synthesis unit 30, a demapping unit 32, a deinterleave unit 34, and a decoding unit 36. Further, the received signal 200, the synthesis control signal 202, the equalized data 204, and the synthesized data 206 are included as signals.

  As shown in FIG. 3C or FIG. 4B, the baseband processing unit 14 receives a signal in which OFDM symbols having the same contents are repeated a predetermined number of times. Here, the predetermined number of times is two. Of the input signal, one OFDM symbol is formed by a transmission period and a non-transmission period. The signaled section corresponds to the IFFT signal, and the non-transmitted section corresponds to GI. The input signal is frequency hopped in units of OFDM symbols, and one OFDM symbol among the input signals uses a plurality of carriers. Note that a signal input to the baseband processing unit 14 is a received signal 200.

  The symbol timing synchronization unit 22 detects the timing of the OFDM symbol included in the received signal 200 during the preamble period of the input received signal 200. The detection of the timing of the OFDM symbol is performed by, for example, correlation processing. That is, the symbol timing synchronization unit 22 includes a matched filter therein, and a known signal sequence corresponding to the preamble is stored in the tap coefficient of the matched filter.

  In such a configuration, the correlation value output from the matched filter increases at the timing when the preamble value of the received signal 200 input to the matched filter becomes close to the tap coefficient. The symbol timing synchronization unit 22 detects the timing of the OFDM symbol by detecting the peak of the correlation value. Further, the symbol timing synchronization unit 22 separates an IFFT signal section and a GI section, that is, a transmission section and a non-transmission section, in one OFDM symbol. This is done by counting the number of symbols from the peak position. For example, a signal corresponding to a section from the peak to the IFFT signal is an IFFT signal.

  The deriving unit 24 receives the received signal 200 and inputs information about the timing of the OFDM symbol and the boundary between the IFFT signal section and the GI section from the symbol timing synchronization section 22. In the received signal 200, as described above, two OFDM symbols having the same contents are repeated. The deriving unit 24 derives an SNR corresponding to each of two repeated OFDM symbols having the same contents while reflecting information on the timing of the OFDM symbol and the boundary between the IFFT signal section and the GI section.

  Here, the deriving unit 24 derives the SNR from the interval of the IFFT signal and the GI interval in one symbol. A method for deriving the SNR will be described later. Further, since the deriving unit 24 derives the SNR in units of OFDM symbols, this corresponds to deriving the SNR corresponding to each of a plurality of hopping frequencies defined in the frequency hopping. Furthermore, the deriving unit 24 generates a control signal for deriving a weighting factor from the derived SNR, and outputs this as a combined control signal 202. Here, the combining control signal 202 indicates the ratio of SNR in two OFDM symbols to be combined.

  The delay symbol synthesis unit 20 receives the received signal 200 and receives information about the timing of the OFDM symbol and the boundary between the IFFT signal section and the GI section from the symbol timing synchronization section 22. The delay symbol synthesizer 20 separates the OFDM symbol in the received signal 200 into an IFFT signal section and a GI section based on information about the boundary between the IFFT signal section and the GI section. Furthermore, the delay symbol synthesis unit 20 synthesizes the delayed wave component received in the GI section and the IFFT signal.

  The FFT 26 performs FFT on the signal synthesized by the delay symbol synthesis unit 20. As a result, the time domain signal is converted to a frequency domain signal, and each frequency domain signal corresponds to a subcarrier signal. Hereinafter, an OFDM symbol corresponds to a frequency domain signal. Here, the number of points of the FFT is set to “128” as in the IFFT.

  The equalization unit 28 performs equalization processing on the subcarrier signal input from the FFT 26. That is, since the subcarrier signal includes amplitude distortion and phase distortion due to multipath delay in the wireless transmission path, the subcarrier signal is corrected. The execution of the equalization process generally requires estimation of a wireless transmission path, but the equalization unit 28 performs wireless transmission using, for example, an LMS (Least Mean Square) algorithm in a preamble section. Estimate the road. Note that the estimation of the wireless transmission path is executed for each subcarrier. Here, the equalization unit 28 outputs the signal of the subcarrier that has been subjected to the equalization process as equalized data 204.

  The synthesis unit 30 receives the synthesis control signal 202 from the derivation unit 24 and receives the equalization data 204 from the equalization unit 28. The combining unit 30 derives weight coefficients corresponding to the number of times the number of OFDM symbols having the same content is repeated while reflecting the combining control signal 202. Here, since the OFDM symbol having the same content is repeated twice, two weighting factors are derived. Further, since the deriving unit 24 updates the weighting coefficient in symbol units, this corresponds to deriving the weighting coefficient in hopping frequency units. The combining unit 30 synthesizes the OFDM symbols having the same contents in the equalized data 204 after weighting the OFDM symbols having the same contents by the weighting coefficients while making the two weighting coefficients correspond to the OFDM symbols having the same contents. Here, the combining unit 30 combines two OFDM symbols having the same content in units of a plurality of carriers. The synthesizer 30 outputs the synthesized signal as synthesized data 206.

  The demapping unit 32 demaps the combined data 206 to QPSK signal points. Note that the composite data 206 is phase-modulated, and here, the phase modulation method is QPSK. The demapping unit 32 associates the signal point of the composite data 206 with the closest signal point among the four signal points of QPSK.

  The deinterleaving unit 34 deinterleaves the signal from the demapping unit 32 according to a rule corresponding to the rule of interleaving performed in a transmission device (not shown). The decoding unit 36 decodes the signal from the deinterleaving unit 34. If the encoding performed in the transmission device (not shown) is convolutional encoding, the decoding unit 36 performs Viterbi decoding. Note that the decoding unit 36 may execute Viterbi decoding based on a hard decision signal or a soft decision signal. At that time, the number of bits of the signal from the demapping unit 32 is different.

  This configuration can be realized in terms of hardware by a CPU, memory, or other LSI of an arbitrary computer, and in terms of software, it is realized by a program having a reservation management function loaded in memory. The functional block realized by those cooperation is drawn. Accordingly, those skilled in the art will understand that these functional blocks can be realized in various forms by hardware only, software only, or a combination thereof.

  FIG. 7 shows the configuration of the derivation unit 24. The derivation unit 24 includes a power integration unit 40, an averaging unit 42, an SNR calculation unit 44, and an SNR comparison unit 46.

  The power integration unit 40 integrates the power of the section of the IFFT signal in one OFDM symbol. Here, the power in the interval of the input IFFT signal is integrated according to the sampling interval at which the baseband processing unit 14 operates. Further, the power integration unit 40 integrates the power of the GI section in one OFDM symbol. Here, the power of the input GI section is integrated according to the sampling interval at which the baseband processing unit 14 operates. The separation of the IFFT signal section and the GI section in the OFDM symbol is performed based on the information about the boundary between the IFFT signal section and the GI section input from the symbol timing synchronization unit 22.

  The averaging unit 42 averages the power of the IFFT signal section integrated by the power integration unit 40 according to the number of samples in the section of the IFFT signal. In addition, the averaging unit 42 performs the same process in the GI section. That is, since the IFFT signal section and the GI section have different lengths, it is difficult to directly process the integrated power of the IFFT signal section and the integrated power of the GI section. Therefore, the averaging unit 42 executes the averaging process so that the process can be executed between them.

  The SNR calculation unit 44 inputs the average power of the IFFT signal section and the average power of the GI section from the averaging unit 42. The SNR calculator 44 divides the average power of the IFFT signal section by the average power of the GI section to derive the SNR. Here, since the delayed wave is also received in the GI section, the average power of the GI section is different from the complete noise level, but is generally lower than the average power of the IFFT signal section. Consider noise level. Note that, as the average power in the GI section, the power in the rear portion may be averaged in the GI section. Thereby, the influence of the delayed wave can be reduced.

  The SNR comparison unit 46 inputs the SNR in units of OFDM symbols from the SNR calculation unit 44. Further, the SNR comparison unit 46 compares the SNRs for two OFDM symbols having the same content, and generates a signal indicating the ratio of the sizes. For example, the SNR comparison unit 46 generates a signal indicating the comparison result as “1: 2” for two OFDM symbols. The SNR comparison unit 46 outputs the generated signal as the synthesis control signal 202.

  FIG. 8 shows the configuration of the synthesis unit 30. The synthesis unit 30 includes a multiplication unit 50, a buffer 52, an addition unit 54, a scaling unit 56, a weighting coefficient table 58, and a timing output unit 60. Further, a timing signal 208 is included as a signal.

  The timing output unit 60 receives the synthesis control signal 202 from the derivation unit 24 and receives the timing signal 208 from the control unit 16. The timing signal 208 is a signal indicating the timing of the OFDM symbol, for example. The timing output unit 60 outputs the input synthesis control signal 202 to the weighting coefficient table 58 at a predetermined timing based on the timing signal 208. Further, the timing output unit 60 outputs a timing signal for controlling the buffer 52 and the scaling unit 56.

  The weighting factor table 58 stores in advance a table in which the SNR ratio and the two weighting factor values are associated with each other, and based on the table, based on the SNR ratio included in the synthesis control signal 202, two identical values are stored. Convert to two weighting factors for the content OFDM symbol. Here, since two OFDM symbols having the same contents are continuously arranged in time series, the weighting coefficient table 58 outputs the weighting coefficients at timings corresponding to them.

  FIG. 9 shows the data structure in the weighting coefficient table 58. The column “synthesis control signal” corresponds to the ratio of the SNR included in the synthesis control signal 202. That is, as shown in the figure, it is defined as “10: 1”. The “previous symbol coefficient” indicates a weighting factor for the front OFDM symbol among the two OFDM symbols having the same content, and the “rear symbol coefficient” is a weight for the rear OFDM symbol among the two OFDM symbols having the same content. Indicates the coefficient. Here, “A1” and the like indicate arbitrary values. Through the above processing, a plurality of weighting factors are derived so as to reflect the SNR ratio.

  Returning to FIG. The multiplication unit 50 multiplies the equalization data 204 by the weight coefficient from the weight coefficient table 58. The equalized data 204 includes OFDM symbols, and the OFDM symbols further include signals of a plurality of subcarriers. Multiplier 50 multiplies signals of a plurality of subcarriers included in one OFDM symbol by the same weight coefficient. Further, the multiplication unit 50 multiplies the front OFDM symbol by the “previous symbol coefficient” among the two OFDM symbols having the same content, and performs the multiplication for the rear OFDM symbol among the two OFDM symbols having the same content. Multiply by the “post symbol coefficient”.

  The buffer 52 delays the OFDM symbol multiplied by the previous symbol coefficient for one OFDM symbol period. The adder 54 adds the OFDM symbol delayed in the buffer 52 and the OFDM symbol from the multiplier 50. The former corresponds to the OFDM symbol multiplied by the “previous symbol coefficient”, and the latter corresponds to the OFDM symbol multiplied by the “back symbol coefficient”. Since one OFDM symbol is composed of signals of a plurality of subcarriers, the adding unit 54 performs addition in units of subcarriers. The addition here corresponds to synthesis. The scaling unit 56 adjusts the number of output bits of the signal added by the adding unit 54. The scaling unit 56 outputs a signal in which the number of output bits is adjusted as synthesized data 206.

  The operation of the receiving apparatus 100 having the above configuration will be described. The radio unit 12 converts the frequency-hopped signal in units of OFDM symbols from a radio frequency to a baseband frequency and outputs the received signal 200. The symbol timing synchronization unit 22 extracts the timing of the OFDM symbol from the symbol timing synchronization unit 22. The derivation unit 24 receives the OFDM symbol timing from the symbol timing synchronization unit 22, calculates the SNR per OFDM symbol in the received signal 200, derives the SNR ratio for two OFDM symbols of the same content, and obtains the result. Output as a synthesis control signal 202. Delay symbol combining section 20 combines the signal in the IFFT signal section and the signal in the GI section in the OFDM symbol of received signal 200.

  The FFT 26 performs FFT on the signal synthesized in the delay symbol synthesis unit 20. The equalizing unit 28 estimates the characteristics of the wireless transmission path from the preamble, equalizes the signal subjected to the FFT in the FFT 26 based on the estimated characteristics of the wireless transmission path, and outputs the equalized data 204. The combining unit 30 derives weighting factors for two OFDM symbols having the same contents while reflecting the combining control signal 202. The combining unit 30 combines two OFDM symbols having the same content in the equalized data 204 after weighting them with a weighting coefficient, and derives them as combined data 206. The demapping unit 32 demaps the composite data 206. The deinterleave unit 34 deinterleaves the signal demapped by the demapping unit 32. The decoding unit 36 decodes the signal deinterleaved by the deinterleaving unit 34.

  Here, another aspect of the present embodiment will be described. Up to this point, the deriving unit 24 has calculated the SNR from the received signal 200 in order to derive the weighting factor. In another aspect of the present embodiment, the deriving unit 24 derives the signal strength from the received signal 200. Therefore, in another aspect of the present embodiment, the weighting factor can be derived even when a signal is transmitted in the GI section.

FIG. 10 shows another configuration of the derivation unit 24. The deriving unit 24 includes a power integrating unit 40, an averaging unit 42, and a comparing unit 70.

  The power integration unit 40 integrates the power in one OFDM symbol. Here, the power of the OFDM symbol interval is integrated according to the sampling interval at which the baseband processing unit 14 operates. The averaging unit 42 averages the power of the OFDM symbol section integrated by the power integration unit 40 according to the number of samples in the OFDM symbol section.

  The comparison unit 70 receives the averaged power from the averaging unit 42. Furthermore, the comparison unit 70 compares the power as the signal strength for two OFDM symbols having the same content, and generates a signal indicating the ratio of the magnitudes. The comparison unit 70 outputs the generated signal as the synthesis control signal 202.

  In another aspect of this embodiment, the baseband processing unit 14 receives a received signal 200 in which OFDM symbols having the same contents are repeated a predetermined number of times. Here, the predetermined number of times is “2” as in the above-described embodiment. Here, the OFDM symbol signal is formed by the IFFT signal and the GI, but the GI may be a non-transmission section or a part of the IFFT signal may be transmitted. In the latter case, the GI may be arranged before the IFFT signal.

  The deriving unit 24 derives the two weighting factors while reflecting the signal strengths corresponding to the two OFDM symbols having the same contents. Since the deriving unit 24 updates the weighting coefficient in symbol units while reflecting the signal strength in OFDM symbol units, this reflects the signal strength corresponding to each of a plurality of hopping frequencies defined in frequency hopping. This corresponds to deriving a weighting factor for each hopping frequency. The synthesizing unit 30 synthesizes two OFDM symbols having the same contents while corresponding the OFDM symbols having the same contents to the two weighting coefficients and weighting the OFDM symbols having the same contents by the two weighting coefficients.

  According to the embodiment of the present invention, the weighting factor corresponding to each OFDM symbol having the same content repeated a predetermined number of times reflects the signal-to-noise ratio for each OFDM symbol having the same content. Even when the quality of one of the OFDM symbols is low, a decrease in the combined gain of the OFDM symbols can be suppressed. In addition, a weighting factor is derived while reflecting the SNR corresponding to each of two OFDM symbols having the same content, weighted by the derived weighting factor, and then two OFDM symbols having the same content are synthesized. Even when the quality of one of the OFDM symbols is low, a decrease in the combined gain of the OFDM symbols can be suppressed. In addition, since the SNR is derived from the power for each of the transmission period and non-transmission period in the OFDM symbol, the SNR according to the characteristics of the wireless transmission path can be measured. Moreover, SNR can be measured easily. Moreover, since a weighting factor corresponding to the SNR is used, the combined gain can be improved. In addition, communication quality can be improved. In addition, since the weighting factor is derived for each OFD symbol, it is possible to derive the weighting factor that follows the fluctuation of the wireless transmission path. Further, even if the wireless transmission path is fluctuating, it is possible to suppress a decrease in the combined gain of OFDM symbols.

  Further, since the weighting factor is derived for each hopping frequency, the weighting factor corresponding to the frequency hopping can be derived. Moreover, the effect of time diversity and the effect of frequency diversity can be obtained. Further, since signals are synthesized in units of subcarriers, it is possible to deal with multicarrier signals. Also, since the weighting factor corresponding to each OFDM symbol having the same content that is repeated a predetermined number of times reflects the signal strength for each OFDM symbol having the same content, the quality of one of the OFDM symbols having the same content is low. Even in this case, it is possible to suppress a decrease in the combined gain of the OFDM symbol. In addition, a weighting factor is derived while reflecting the signal strength corresponding to each of two OFDM symbols having the same content, and weighting is performed by the derived weighting factor, and then the two OFDM symbols having the same content are synthesized. Even if the quality of one of the content OFDM symbols is low, a decrease in the combined gain of the OFDM symbols can be suppressed. In addition, since the weighting factor is derived while reflecting the signal strength, the present invention can be applied even when there is no non-transmission section in the OFDM symbol. Further, since the SNR is not calculated, the processing can be simplified. Further, it can be applied to various communication systems.

  In the above, this invention was demonstrated based on the Example. This embodiment is an exemplification, and it will be understood by those skilled in the art that various modifications can be made to the combination of each component and each processing process, and such modifications are also within the scope of the present invention. .

  In the embodiment of the present invention, the receiving apparatus 100 receives a multicarrier signal. However, the present invention is not limited to this. For example, it may not be a multicarrier signal. In this case, the “OFDM symbol” in the embodiment is simply “symbol”. In addition, processing in units of subcarriers is processing for one carrier. According to this modification, the present invention can also be applied to a communication system compatible with a single carrier. That is, it is only necessary to form a signal so that the same symbol is repeated in a predetermined unit.

  In the embodiment of the present invention, the receiving apparatus 100 continuously receives symbols having the same content. However, the present invention is not limited to this. For example, symbols having the same content may not be consecutive. In that case, the receiving apparatus 100 executes the same processing as in the embodiment at the timing when the same symbol is received. According to this modification, symbols having the same contents are transmitted, but the present invention can also be applied to a signal format in which they are not continuous. That is, it is only necessary for receiving apparatus 100 to grasp the regularity in which symbols having the same content are repeated. In addition, symbols having the same content may be received at different timings.

  In the embodiment of the present invention, the receiving apparatus 100 receives a frequency-hopped signal. However, the present invention is not limited to this. For example, the receiving apparatus 100 may not receive a signal that is not frequency hopped. According to this modification, the present invention can be applied to various communication systems. Moreover, the effect of time diversity is also acquired. That is, it is only necessary to form a signal so that the same symbol is repeated in a predetermined unit.

  In the embodiment of the present invention, the synthesizer 30 uses the value stored in the weight coefficient table 58 as the weight coefficient. However, the present invention is not limited to this. For example, the combining unit 30 may use the SNR and signal strength derived by the deriving unit 24 as they are as weighting factors. According to this modification, the weighting coefficient table 58 can be omitted. That is, a weighting factor corresponding to the characteristics of the wireless transmission path may be derived.

  In the embodiment of the present invention, the deriving unit 24 and the synthesizing unit 30 derive weight coefficients for each symbol. However, the present invention is not limited to this. For example, the signal input to the receiving apparatus 100 is a burst signal including a plurality of symbols, and the derivation unit 24 and the synthesis unit 30 perform hopping frequency units in a partial period of the burst signal. May be derived respectively. Here, the “partial period” is set to a preamble, for example. According to the present modification, the weighting coefficient only has to be derived during a partial period of the burst signal, so that the processing period can be shortened. In addition, an increase in power consumption can be suppressed. That is, a weighting factor corresponding to the characteristics of the wireless transmission path may be derived.

It is a figure which shows the structure of the receiver which concerns on the Example of this invention. It is a figure which shows the hopping frequency of the signal received in the receiver of FIG. FIGS. 3A to 3C are diagrams illustrating a symbol configuration of a signal received by the receiving apparatus of FIG. FIGS. 4A to 4B are diagrams illustrating waveforms of signals received by the receiving apparatus of FIG. It is a figure which shows the burst format of the signal received in the receiver of FIG. It is a figure which shows the structure of the baseband process part of FIG. It is a figure which shows the structure of the derivation | leading-out part of FIG. It is a figure which shows the structure of the synthetic | combination part of FIG. It is a figure which shows the structure of the data in the weighting coefficient table of FIG. It is a figure which shows another structure of the derivation | leading-out part of FIG.

Explanation of symbols

  20 delay symbol synthesis unit, 22 symbol timing synchronization unit, 24 derivation unit, 26 FFT, 28 equalization unit, 30 synthesis unit, 32 demapping unit, 34 deinterleave unit, 36 decoding unit, 40 power integration unit, 42 averaging Unit, 44 SNR calculation unit, 46 SNR comparison unit, 50 multiplication unit, 52 buffer, 54 addition unit, 56 scaling unit, 58 weight coefficient table, 60 timing output unit, 100 receiving device.

Claims (9)

An input unit that symbols of the same content to enter a predetermined repeated number Rutomoni, frequency hopping signal,
Rutotomoni to reflect the corresponding signal strength to each of the symbols of the same content is repeated a predetermined number of times, while reflecting a corresponding signal strength to each of the plurality of hopping frequencies defined in the frequency hopping, the weighting coefficients, respectively A derivation unit to derive,
Said weighting factor, while corresponding to the symbols of the same content is repeated a predetermined number of times, since the weighted respective symbols of the same content by the weighting factor, and a combining unit for combining the symbols of the same content,
A diversity apparatus comprising:   The diversity apparatus according to claim 1, wherein the deriving unit updates the weighting coefficient in symbol units while reflecting the signal strength in symbol units. The signal input to the input unit is a burst signal including a plurality of symbols,
The diversity apparatus according to claim 1 , wherein the deriving unit derives a weighting factor for each hopping frequency in a partial period of the burst signal. An input unit that symbols of the same content to enter a predetermined repeated number Rutomoni, frequency hopping signal,
Rutotomoni by reflecting the signal to noise ratio corresponding to each symbol of the same content is repeated a predetermined number of times, while reflecting the signal to noise ratio corresponding to each of a plurality of hopping frequencies defined in the frequency hopping, heavy A derivation unit for deriving each coefficient,
Said weighting factor, while corresponding to the symbols of the same content is repeated a predetermined number of times, since the weighted respective symbols of the same content by the weighting factor, and a combining unit for combining the symbols of the same content,
Among the signals input to the input unit, one symbol is formed by a transmission interval and a non-transmission interval,
The diversity device is characterized in that the derivation unit derives a signal-to-noise ratio from signal strengths in a transmission period and a non-transmission period in one symbol. The diversity apparatus according to claim 4 , wherein the derivation unit updates the weighting coefficient in units of symbols while reflecting a signal-to-noise ratio in units of symbols. The signal input to the input unit is a burst signal including a plurality of symbols,
The deriving unit, in some periods of the burst signal, the diversity device according to claim 4, characterized in that to derive the weighting factors hopping frequency units respectively. Among the signals input to the input unit, one symbol uses a plurality of carriers,
The combining unit is to each of a plurality of carriers to a unit, the diversity device according to each of claims 1-6, characterized in that the synthesis symbols of the same content. Symbols of the same content type the predetermined number of times repeated Rutomoni, frequency hopped signal,
Rutotomoni to reflect the corresponding signal strength to each of the symbols of the same content is repeated a predetermined number of times, while reflecting a corresponding signal strength to each of the plurality of hopping frequencies defined in the frequency hopping, the symbols of the same content Deriving the corresponding weighting factors,
A diversity method characterized in that symbols having the same contents are weighted by weighting factors, and then the symbols having the same contents are synthesized. Same content symbol is repeated a predetermined number of times Rutomoni, a frequency hopping signal, and inputs a signal including symbols formed by chromatic transmission interval and a non-transmission interval,
A signal-to-noise ratio corresponding to each of the same content symbols repeated a predetermined number of times and a signal-to-noise ratio corresponding to each of a plurality of hopping frequencies defined in frequency hopping , and transmission / reception in one symbol While reflecting the signal-to-noise ratio calculated from the signal strength in the interval and the non-transmission interval, derive the weighting factor corresponding to each symbol of the same content,
A diversity method characterized in that symbols having the same contents are weighted by weighting factors, and then the symbols having the same contents are synthesized.

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