JP7582478B2 - Wireless communication system and method - Google Patents

Description

The present invention relates to technology for spatial multiplexing transmission of radio signals.

In recent years, various means of increasing speed have been considered in response to the growing demand for wireless communication. One effective means is a method of equivalently increasing the number of communication paths by spatial multiplexing. MIMO communication using multiple antenna configurations, in particular the OFDM-MIMO method combined with OFDM (Orthogonal Frequency Domain Multiplexing) modulation, has been put to practical use in wireless communication systems such as wireless LAN and LTE/5G (Non-Patent Document 1).

In MIMO communications, spatial multiplexing transmission and reception is generally performed on the premise of time synchronization between antenna ports. In other words, the sampling timing of transmitting antenna ports #1-#N is the same, and signals to be spatially multiplexed are superimposed in the same sample range at each antenna port according to rules such as radio frames, and MIMO detection processing is performed on the receiving side (Non-Patent Document 2).

Another effective way to increase speed is to use wider bandwidth, but as available radio wave resources become scarce, RF frequency bands that can use wider bandwidths are becoming higher and higher. Traditional methods such as the superheterodyne method via IF frequency involve many analog devices when upconverting baseband signals to the RF frequency at which they are actually transmitted. High-frequency analog devices are more expensive than low-frequency analog devices, which generally increases the cost of radio equipment, and is a factor that inhibits the spread of wireless communication systems, and especially terminal devices.

In recent years, as a means of realizing low-cost high-frequency radios, radios have appeared that use an appropriate BPF (band-pass filter) to extract alias components that appear when baseband signals are oversampled in digital signal processing, and transmit (and receive) them as RF frequency band signals. On the other hand, such low-cost radio configurations are premised on the operation of a DAC with high-speed sampling of the GSa/s class, and when transmitting (receiving) from multiple antenna ports as in a MIMO antenna configuration, it becomes difficult to synchronize the sample levels between antenna ports. For example, in the case of the radio in Non-Patent Document 3, the specifications are such that a maximum deviation of ±1 sample occurs between antenna ports.

"MIMO Wireless Communication", Tokyo Denki University Press, Chapters 1.5-1.6, 2009 S. Yang and L. Hanzo, "Fifty Years of MIMO Detection: The Road to Large-Scale MIMOs," in IEEE Communications Surveys & Tutorials, vol. 17, no. 4, pp. 1941-1988, Fourthquarter 2015, doi: 10.1109/COMST.2015.2475242. XILINX, Zynq UltraScale+ RFSoC Data Sheet:DC and AC Switching Characteristics, DS926 (v1.8) April 6, 2021.

As mentioned above, in principle, in MIMO communications, spatially multiplexed signals can be separated by signal processing such as spatial filtering. However, if it is difficult to synchronize the sample levels between antenna ports, there is a problem that this leads to degradation of separation performance characteristics.

The disclosed technology aims to improve sample-level synchronization performance between antenna ports and properly separate spatially multiplexed signals.

The disclosed technology is a wireless communication system that has a transmitting device and a receiving device and performs MIMO communication, in which the transmitting device transmits a wireless communication signal to the receiving device, and the receiving device acquires information indicating a maximum value of jitter that indicates the sample synchronization capability between antenna ports of the transmitting device, and determines an FFT interval to be used for demodulating or signal equalizing the signal transmitted from the transmitting device based on the maximum value of jitter of the transmitting device and the maximum value of jitter of the receiving device.

Improved sample-level synchronization performance between antenna ports enables proper separation of spatially multiplexed signals.

1 is a configuration diagram of a communication system according to an embodiment of the present invention. FIG. 11 is a diagram for explaining synchronization of sample levels between antenna ports. FIG. 11 is a first diagram for explaining a situation in which inter-symbol interference occurs. FIG. 11 is a second diagram for explaining the occurrence state of inter-symbol interference. FIG. 10 is a diagram for explaining a method of offsetting an FFT interval according to the first embodiment; FIG. 2 is a diagram illustrating a configuration example of a transmitting device according to a first embodiment. FIG. 2 is a diagram illustrating a configuration example of a receiving device according to a first embodiment. FIG. 11 is a diagram illustrating a configuration example of a transmitting device according to a second embodiment. FIG. 11 is a diagram illustrating a configuration example of a receiving device according to a second embodiment. FIG. 11 is a diagram for explaining a method of offsetting an FFT interval according to a second embodiment. FIG. 13 is a diagram for explaining a method of offsetting an FFT interval in uplink multi-user MIMO. FIG. 11 is a diagram illustrating a configuration example of a wireless communication system according to a third embodiment. FIG. 13 is a diagram illustrating a configuration example of a transmitting device according to a fourth embodiment. FIG. 13 is a diagram for explaining a method of offsetting an FFT interval according to a fourth embodiment.

Hereinafter, an embodiment of the present invention (the present embodiment) will be described with reference to the drawings. The embodiment described below is merely an example, and the embodiment to which the present invention is applicable is not limited to the following embodiment.

(System Configuration)
1 is a configuration diagram of a communication system according to an embodiment of the present invention. As shown in FIG. 1, the wireless communication system according to the embodiment includes a transmitting device 100 and a receiving device 200.

Next, the synchronization of sample levels between antenna ports in this embodiment will be explained using examples from Example 1 to Example 5.

Figure 2 is a diagram for explaining the synchronization of sample levels between antenna ports. For example, as shown in Figure 2, when the antenna ports of each channel are completely synchronized, the receiver side synchronizes based on a SYNC signal (synchronization signal) for time synchronization multiplexed on a specific antenna port (ch1 in the figure), so that the FFT (Fast Fourier Transform) section applied to the received signal of each antenna port contains only its own symbol, that is, no inter-symbol interference occurs. The FFT section is a section used for signal demodulation or signal equalization. In the case of the OFDM method assuming mobile wireless communication, in order to suppress inter-symbol interference caused by delayed waves, a cyclic prefix (hereinafter referred to as CPrefix) that is a copy of the end of the signal waveform of the DATA section (data signal) is added before the DATA section, and the receiving side generally removes these and then performs FFT to obtain the modulation symbol for each subcarrier. However, if the sample levels of antenna ports are not synchronized in MIMO-OFDM, the sample position of CPrefix shifts for each MIMO channel, which becomes a cause of inter-symbol interference.

Figure 3 is the first diagram for explaining the occurrence of intersymbol interference. As in Figure 2, a SYNC signal is multiplexed on a specific antenna port (ch1 in the figure), and the receiver detects it to identify the start and end of the following CPrefix and the start and end of the DATA section. In normal operation, the receiver performs OFDM demodulation with the end of CPrefix as the start of the FFT, that is, the FFT section from the start to the end of the DATA section. If the sample levels are not synchronized between antenna ports, intersymbol interference occurs if the received signal of other antenna ports is shifted forward compared to the received signal of a specific antenna port that serves as a reference.

In this case, if the jitter on the transmitter side is ±Δ _Tx and the jitter on the receiver side is ±Δ _Rx , a shift of up to 2 (Δ _Tx +Δ _Rx ) samples may occur.

Figure 4 is a second diagram for explaining the occurrence of intersymbol interference. As shown in Figure 4, the most severe intersymbol interference occurs when the reference antenna port (ch1) is the rearmost.

(FFT interval offset method according to the first embodiment)
5 is a diagram for explaining a method of offsetting an FFT interval according to the first embodiment. In this embodiment, the transmitting device 100 grasps in advance the maximum value of jitter indicating the sample synchronization capability between antenna ports. The receiving device 200 acquires the information from the transmitting device 100. At this time, the jitter on the transmitting device 100 side is ±Δ _Tx and the jitter on the receiving device 200 side is ±Δ _Rx .

The receiving device 200 determines the end point of the CPrefix inserted by the transmitting device 100 for delay wave countermeasures by a synchronization signal of a specific antenna port, and performs transmission channel estimation, equalization, and OFDM demodulation with a sample point of the CPrefix at least 2 (Δ _Tx + Δ _Rx ) samples ahead from the end point as the start point of the FFT section. Note that since the CPrefix is a cyclic shift signal of the DATA section, it undergoes phase rotation, but OFDM demodulation is possible without inter-symbol interference (ISI). The effect of the phase rotation is compensated for by transmission channel estimation.

(Configuration example of a transmitting device according to the first embodiment)
6 is a diagram showing a configuration example of a transmitting device according to a first embodiment. The transmitting device 100 includes a bit distribution circuit 110 and a plurality of transmitting circuits 120. The number of transmitting circuits 120 included in the transmitting device 100 corresponds to the number of spatial multiplexing layers of a transmission signal. Each transmitting circuit 120 includes a transmission path estimation signal adding circuit 121, an m-QAM modulation circuit 122, a frequency multiplexing circuit 123, an IFFT circuit 124, a cyclic prefix adding circuit 125, a synchronization signal multiplexing circuit 126, a transmitting side synchronization capability information sending circuit 127, a radio frame configuration circuit 128, and a frequency conversion circuit 129.

The bit distribution circuit 110 distributes the input bits to n MIMO channels for spatial multiplexing. The m-QAM modulation circuit 122 of each MIMO channel performs symbol mapping for each subcarrier.

In this embodiment, multi-level amplitude IQ orthogonal modulation such as 16QAM or 64QAM is assumed, but other modulation methods such as QPSK (4QAM) or BPSK may also be used. In addition to these data subcarriers, a transmission path estimation signal output from a transmission path estimation signal addition circuit 121 is multiplexed onto a specific subcarrier by a frequency multiplexing circuit 123, and then an IFFT circuit 124 for OFDM modulation generates a time domain data signal.

Next, the cyclic prefix adding circuit 125 adds a CPrefix, which is a copy of the latter half of the time domain data signal, to the beginning of the time domain data signal. The length of the CPrefix may generally be treated as a fixed parameter as a measure against inter-symbol interference caused by delayed waves, but a separate means for controlling it may also be provided.

Next, the radio frame configuration circuit 128 embeds the control information sent by the transmitting side synchronization capability information sending circuit 127 in the control information channel, etc. The control information includes information indicating the maximum value of jitter (±Δ _{Tx ) indicating the sample synchronization capability between the antenna ports of the transmitting device 100. Note that since the information indicating the maximum value of jitter (±Δ Tx )} is a value specific to the wireless device, the transmitting device 100 may report it only once in the initial connection stage before MIMO communication is performed.

In addition, for a specific MIMO channel (e.g., ch1), a synchronization signal (e.g., a modulated wave generated based on an M sequence) sent from the synchronization signal multiplexing circuit 126 is time-multiplexed onto the beginning of the radio frame. When the aforementioned transmission path estimation signal is designed in the time domain, the radio frame configuration circuit 128 may multiplex the transmission path estimation signal at an appropriate location.

The signals of each MIMO channel are sent from the respective antenna ports via a frequency conversion circuit 129. As a frequency conversion means, a low-cost configuration can be used in which alias components that appear when the baseband signal is oversampled are extracted using an appropriate BPF and transmitted as a signal in the RF frequency band.

(Configuration example of a receiving device according to the first embodiment)
7 is a diagram showing a configuration example of a receiving device according to the first embodiment. The receiving device 200 includes a bit mixing circuit 210, a plurality of m-QAM demodulation circuits 220, a MIMO equalization circuit 230, and a plurality of receiving circuits 240. The number of receiving circuits 240 included in the receiving device 200 corresponds to the number of spatial multiplexing layers of the received signal. Each receiving circuit 240 includes a transmission path estimation signal detection circuit 241, an FFT interval determination circuit 242, a radio frame position detection circuit 243, a transmission side synchronization capability information detection circuit 244, a synchronization signal detection circuit 245, an FFT circuit 246, and a frequency multiplexing/demultiplexing circuit 247.

For a received signal of a specific MIMO channel (e.g., ch1) in which a synchronization signal is multiplexed, the synchronization signal detection circuit 245 detects a known synchronization signal (e.g., a modulated wave generated based on an M sequence) by sliding correlation or the like. The radio frame position detection circuit 243 determines the position of the radio frame, i.e., the start and end points of the CPrefix and the start and end points of the DATA portion of each OFDM symbol.

The transmitting side synchronization capability information detection circuit 244 acquires information indicating the maximum value ±Δ _Tx of jitter indicating the sample synchronization capability between antenna ports of the transmitting device 100. The radio frame position detection circuit 243 transmits this information to the receiving circuits 240 of other MIMO channels to share it within the receiving device 200.

Next, the FFT interval determination circuit 242 determines a sample interval equivalent to the FFT size (2048 samples for 2048 FFT) from the sample point of CPrefix at least 2 (Δ _Tx + Δ _Rx ) samples forward from the end point of the identified CPrefix as the start point of the FFT interval. The FFT circuit 246 performs FFT based on the determined FFT interval and decomposes it into subcarriers.

The frequency demultiplexing circuit 247 separates the transmission path estimation signal. The transmission path estimation signal detection circuit 241 estimates information indicating the transmission path. Here, the information indicating the transmission path includes not only the amplitude change and phase rotation in spatial propagation, but also the amount of phase rotation due to offsetting the FFT start point mentioned above forward.

The MIMO equalization circuit 230 uses the transmission path information to perform MIMO interference removal and equalization on the data subcarriers of each MIMO channel separated by the frequency multiplexing/demultiplexing circuit 247. Well-known methods of interference removal and equalization include ZeroForcing in the frequency domain, but other methods may also be used.

The number of m-QAM demodulation circuits 220 provided in the receiving device 200 corresponds to the number of MIMO channels of the received signal after equalization by the MIMO equalization circuit 230. Each m-QAM demodulation circuit 220 converts the signal of each MIMO channel after equalization into bits. The bit mixing circuit 210 combines the bits distributed to each spatial multiplex and outputs them.

In addition, the transmitting device 100 may obtain the maximum value ± _ΔRx of jitter indicating the sample synchronization ability between the antenna ports of the receiving device 200 in the feedback link from the receiving device 200 to the transmitting device 100, and then variably control CPrefix so that it is 2 ( _ΔTx + _ΔRx ) samples or more, and in this case, it is desirable to control it while considering the delayed wave resistance. In other words, if the longest delay of the expected delayed wave is Cp samples, the transmitting device 100 may set the length of CPrefix to Cp + 2 ( _ΔTx + _ΔRx ) samples, for example.

In this embodiment, communication assuming OFDM-MIMO is given as an example, but it can also be applied to other MIMO transmission methods assuming block-type frequency domain signal processing. For example, DFT-s-OFDM (DFT-spreading-OFDM) and SC-FDE (Single Carrier-Frequency Domain Equalization) are possible. Forward error correction codes may also be combined.

In each embodiment of the present embodiment, n×n MIMO is assumed in which n antennas are used to realize n spatial multiplexing for both the transmitting device 100 and the receiving device 200, but this is not particularly limited. It is also applicable to a k×n MIMO antenna configuration with k transmitting antennas and n receiving antennas, or to OAM wireless multiplexing using a UCA antenna, which is considered as one form of MIMO.

The maximum jitter values ±Δ _Tx and ±Δ _Rx indicate the sample synchronization capability between the antenna ports of the transmitting device 100 and the receiving device 200, but may be values taking into account the influence of other factors. For example, in the above-mentioned SC-FDE, a raised-cosine filter with a low roll-off rate may be combined as a band-limiting filter in order to improve frequency utilization efficiency, but in cases where inter-symbol interference occurs from the subsequent OFDM symbol due to a long time response, the absolute value of the jitter in the forward direction may be large.

Furthermore, the maximum jitter value ±Δ _Tx (±Δ _Rx ) is notified as control information, but it may be stored in advance in the transmitting device 100 and the receiving device 200 as known information.

Example 2
A second embodiment will be described below with reference to the drawings. The second embodiment differs from the first embodiment in that a synchronization signal is multiplexed into each MIMO channel, and the receiving device 200 directly detects the amount of synchronization deviation of each antenna port with respect to a specific antenna port. Therefore, the following description of the second embodiment will focus on the differences from the first embodiment, and the same reference numerals as those used in the description of the first embodiment will be given to components having the same functional configuration as the first embodiment, and the description thereof will be omitted.

(Configuration example of a transmitting device according to the second embodiment)
8 is a diagram illustrating a configuration example of a transmitting device according to Example 2. Each transmitting circuit 120 of the transmitting device 100 according to this embodiment has a configuration in which the transmitting side synchronization capability information sending circuit 127 is deleted from the transmitting circuit 120 according to Example 1.

The transmitting device 100 according to this embodiment multiplexes the synchronization signal sent from the synchronization signal multiplexing circuit 126 in each MIMO channel onto the beginning of the radio frame. The transmitting device 100 may reuse a single synchronization signal for each MIMO channel by time division processing that changes the MIMO channel into which the synchronization signal is multiplexed for each radio frame, or may spatially multiplex multiple synchronization signals (for example, modulated waves generated based on a Zadoff-Chu sequence) that have excellent cross-correlation characteristics as well as auto-correlation characteristics onto each MIMO channel.

(Configuration example of a receiving device according to the second embodiment)
FIG. 9 is a diagram illustrating an example of a configuration of a receiving device according to the second embodiment.

The receiving device 200 according to this embodiment calculates the sample shift Δi (i = 2, ..., N) of each MIMO channel relative to a specific MIMO channel (e.g., ch1) from the synchronization information identified by the radio frame position detection circuit 243 of each MIMO channel. The FFT interval determination circuit 242 sets the end point of the CPrefix of the MIMO channel received at the earliest timing as the start point of the FFT interval of each MIMO channel, and determines a sample interval equivalent to the FFT size (2048 samples for 2048 FFT) from there as the FFT interval. The FFT circuit 246 performs FFT based on the determined FFT interval and decomposes it into subcarriers.

Figure 10 is a diagram for explaining a method of offsetting an FFT interval according to the second embodiment. The transmitting device 100 multiplexes a synchronization signal with good cross-correlation characteristics onto each MIMO channel. The receiving device 200 detects the sample position of the radio frame of each MIMO channel using the synchronization signal. This allows OFDM demodulation to be performed with the end point of the CPrefix of the earliest arriving MIMO channel as the start point of the FFT interval.

Example 3
A third embodiment will be described below with reference to the drawings. The third embodiment differs from the first embodiment in that the transmitting device 100 individually transmits the maximum value of the jitter to the receiving device 200. Therefore, in the following description of the third embodiment, the differences from the first embodiment will be mainly described, and the same reference numerals as those used in the description of the first embodiment will be given to components having the same functional configuration as the first embodiment, and the description thereof will be omitted.

According to the wireless communication system of this embodiment, it is possible to support uplink multi-user MIMO from multiple terminal stations (an example of a transmitting device 100) to one base station (an example of a receiving device 200).

Fig. 11 is a diagram for explaining a method of offsetting an FFT interval in uplink multi-user MIMO. In uplink multi-user MIMO in a cellular wireless communication system, a synchronization signal is detected in the downlink in principle, while transmission timing control is performed taking into account transmission delays to achieve uplink synchronization, but as described above, it may be difficult to synchronize the sample level between antenna ports. Furthermore, if the terminal design differs for each user, the inter-antenna port jitter Δ _Tx may also have a different value Δ _{Tx_UEi} for each user.

Therefore, the transmitting device 100 and the receiving device 200 share information indicating Δ _{Tx — UEi} using a control channel or the like during non-MIMO communication.

FIG. 12 is a diagram showing a configuration example of a wireless communication system according to a third embodiment. As a premise, when wireless devices (an example of the transmitting device 100) with different capabilities are mixed, it is considered that the sample deviation amount (magnitude of jitter) between antenna ports differs depending on the wireless device. Therefore, each terminal station (transmitting station) (an example of the transmitting device 100) individually notifies a base station (receiving station) (an example of the receiving device 200) of the maximum value of jitter ±Δ _{Tx _UEi} (i = 1, ..., n) indicating the sample synchronization ability between antenna ports of the transmitting device 100. In addition, in a cellular wireless communication system, in a design in which detection of a synchronization signal is performed only in the downlink and synchronization of the uplink is established by transmission timing control based on the synchronization information of the downlink, the transmitting device 100 (terminal station) in the uplink does not need to include a synchronization signal multiplexing circuit 126.

The receiving device 200 derives the maximum value of Δ _{Tx _ UEi} (i = 1, ..., n), that is, max {Δ _{Tx _ UEi} (i = 1, ..., n)} = Δ _MAX . In addition, the jitter ± Δ _Rx indicating the sample synchronization capability between the antenna ports of the receiving device 200 itself is also grasped in advance. The FFT interval determination circuit 242 determines the sample interval equivalent to the FFT size (2048 samples for 2048 FFT) from the start point of the FFT interval of each MIMO channel at least 2 x (Δ _MAX + Δ _Rx ) samples forward from the end point of CPrefix identified in a specific MIMO channel (for example, ch1). The FFT circuit 246 performs FFT based on the determined FFT interval and decomposes into subcarriers.

Example 4
A fourth embodiment will be described below with reference to the drawings. The fourth embodiment differs from the first embodiment in that the transmitting device 100 adds a CyclicPostfix (CPostfix) in addition to the CPrefix. Therefore, in the following description of the fourth embodiment, the differences from the first embodiment will be mainly described, and the same reference numerals as those used in the description of the first embodiment will be given to components having the same functional configuration as the first embodiment, and the description thereof will be omitted.

13 is a diagram showing an example of the configuration of a transmission device according to Example 4. Each transmission circuit 120 of the transmission device 100 according to this example has a Cyclic Prefix/Postfix addition circuit 1251 instead of the Cyclic Prefix addition circuit 125 of each transmission circuit 120 according to Example 1.

The cyclic prefix/postfix adding circuit 1251 not only connects Cprefix to the beginning of the time domain data signal, but also connects a cyclic postfix (hereinafter, referred to as Cpostfix) to the end of the time domain data signal. The cyclic prefix/postfix adding circuit 1251 acquires information indicating the maximum value ± _ΔRx of jitter indicating the sample synchronization capability between antenna ports of the receiving device 200 in the feedback link from the receiving device 200 to the transmitting device 100, and then sets or variably controls Cpostfix so that it is 2 ( _ΔTx + _ΔRx ) samples or more.

Figure 14 is a diagram for explaining the offset method of the FFT interval according to the fourth embodiment. The FFT interval determination circuit 242 according to this embodiment sets the end point of the CPrefix identified by the synchronization signal as the start point of the FFT interval, and determines a sample interval equivalent to the FFT size (2048 samples for 2048 FFT) from there as the FFT interval. The FFT circuit 2216 performs FFT based on the determined FFT interval and decomposes it into subcarriers.

In this embodiment, the CyclicPrefix/Postfix addition circuit 1251 adds CPostfix in addition to CPrefix. This allows the forward offset of the sample shift between antenna ports to be absorbed by CPrefix, while the backward offset can be absorbed by CPostfix.

In addition, in this embodiment, the receiving device 200 does not need the transmitting side synchronization capability information detection circuit 244. That is, the receiving device 200 does not need to acquire information indicating the maximum value ±Δ _Tx of jitter indicating the sample synchronization capability between the antenna ports of the transmitting device 100. This is because inter-symbol interference can be avoided by adding a CPostfix of sufficient length to the data signal.

Note that Examples 1 to 4 may be combined as appropriate. For example, Examples 1 and 4 may be combined.

In this case, the transmitting device 100 adds a CPostfix of at least 2Δ _Tx samples to avoid inter-symbol interference due to jitter ±Δ _Tx indicating the sample synchronization capability between antenna ports of the transmitting device 100. On the other hand, the receiving device 200 performs OFDM demodulation by setting a sample point at least 2Δ _Rx samples ahead of the end point of the identified CPrefix as the start point of the FFT interval in a specific MIMO channel where a synchronization signal is detected, in order to avoid inter-symbol interference due to jitter ±Δ _Rx indicating the sample synchronization capability between antenna ports of the receiving device 200.

This eliminates the need for processing to notify information indicating ±Δ _Rx via a feedback link from the receiving device 200 to the transmitting device 100. Note that this is premised on the fact that the sample length of CPrefix is sufficiently longer than Δ _Rx .

(Summary of the embodiment)
This specification describes at least the wireless communication systems and methods described in the following paragraphs.
(Section 1)
A wireless communication system that performs MIMO communication, comprising a transmitting device and a receiving device,
The transmitting device transmits a wireless communication signal to the receiving device;
The receiving device acquires information indicating a maximum value of jitter indicating a sample synchronization capability between antenna ports of the transmitting device, and determines an FFT interval to be used for demodulation or signal equalization of the signal transmitted from the transmitting device based on the maximum value of jitter of the transmitting device and the maximum value of jitter of the receiving device.
Wireless communication system.
(Section 2)
the transmitting device multiplexes a synchronization signal onto a specific MIMO channel in a radio frame of the signal, and adds a cyclic prefix to a data signal of each MIMO channel;
The receiving device determines, based on a maximum value ΔTx of the jitter of the transmitting device and a maximum value ΔRx of the jitter of the receiving device, a sample point of the cyclic prefix that is at least 2 (ΔTx + ΔRx) samples ahead of an end point of the cyclic prefix identified by the synchronization signal as a start point of the FFT section.
2. A wireless communication system as recited in claim 1.
(Section 3)
The transmitting device acquires information indicating a maximum jitter value ΔRx of the receiving device from the receiving device, and sets the length of the cyclic prefix to at least 2 (ΔTx + ΔRx) samples.
3. A wireless communication system as recited in claim 2.
(Section 4)
the transmitting device multiplexes a synchronization signal onto each MIMO channel in a radio frame of the signal, and adds a cyclic prefix to a data signal of each MIMO channel;
the receiving device detects a sample position of the radio frame of each of the MIMO channels using the synchronization signal, and sets an end point of the cyclic prefix of the earliest arriving MIMO channel as a start point of the FFT section;
4. A wireless communication system according to any one of claims 1 to 3.
(Section 5)
The wireless communication system includes a plurality of transmitting devices,
each of the plurality of transmitting devices adds a cyclic prefix to a data signal of each MIMO channel in a radio frame of the signal, and transmits information indicating a maximum value of the jitter to the receiving device;
The receiving device receives information indicating a maximum value of the jitter from each of the plurality of transmitting devices, derives a maximum value Δ _MAX of the jitter for each of the transmitting devices, and sets a start point of the FFT section at least 2×(Δ _MAX + Δ _Rx ) samples ahead of an end point of the cyclic prefix based on the maximum value Δ _Rx of the jitter of the receiving device.
5. A wireless communication system according to any one of claims 1 to 4.
(Section 6)
the transmitting device multiplexes a synchronization signal onto a specific MIMO channel in a radio frame of the signal, and adds a cyclic prefix and a cyclic postfix to a data signal of each MIMO channel;
The receiving device sets the end point of the cyclic prefix identified by the synchronization signal as the start point of the FFT section.
5. A wireless communication system according to any one of claims 1 to 4.
(Section 7)
the transmitting device multiplexes a synchronization signal into a specific MIMO channel in the radio frame of the signal, adds a cyclic prefix to the data signal of each MIMO channel, and adds a cyclic postfix having a length of at least 2×ΔTx samples based on a maximum value ΔTx of the jitter of the transmitting device;
The receiving device sets the start point of the FFT section to be at least 2×ΔRx samples ahead of the end point of the cyclic prefix identified by the synchronization signal.
5. A wireless communication system according to any one of claims 1 to 4.
(Section 8)
A communication method in a wireless communication system including a transmitting device and a receiving device,
a transmitting device transmitting a wireless communication signal to the receiving device;
The receiving device acquires information indicating a maximum value of jitter indicating a sample synchronization capability between antenna ports of the transmitting device, and determines an FFT interval to be used for demodulation or signal equalization of the signal transmitted from the transmitting device based on the maximum value of jitter of the transmitting device and the maximum value of jitter of the receiving device.
Communication methods.

Although the present embodiment has been described above, the present invention is not limited to such a specific embodiment, and various modifications and variations are possible within the scope of the gist of the present invention as described in the claims.

100 Transmitter 110 Bit distribution circuit 120 Transmitter circuit 121 Transmission path estimation signal addition circuit 122 m-QAM modulation circuit 123 Frequency multiplexing circuit 124 IFFT circuit 125 Cyclic prefix addition circuit 1251 Cyclic prefix/postfix addition circuit 126 Synchronization signal multiplexing circuit 127 Transmitter side synchronization capability information transmission circuit 128 Radio frame configuration circuit 129 Frequency conversion circuit 200 Receiving device 210 Bit mixing circuit 220 m-QAM demodulation circuit 230 MIMO equalization circuit 240 Receiving circuit 241 Transmission path estimation signal detection circuit 242 FFT section determination circuit 243 Radio frame position detection circuit 244 Transmitter side synchronization capability information detection circuit 245 Synchronization signal detection circuit 246 FFT circuit 247 Frequency multiplexing/demultiplexing circuit

Claims (8)

A wireless communication system that performs MIMO communication, comprising a transmitting device and a receiving device,
The transmitting device transmits a wireless communication signal to the receiving device;
The receiving device acquires information indicating a maximum value of jitter indicating a sample synchronization capability between antenna ports of the transmitting device, and determines an FFT interval to be used for demodulation or signal equalization of the signal transmitted from the transmitting device based on the maximum value of jitter of the transmitting device and the maximum value of jitter of the receiving device.
Wireless communication system. the transmitting device multiplexes a synchronization signal onto a specific MIMO channel in a radio frame of the signal, and adds a cyclic prefix to a data signal of each MIMO channel;
The receiving device determines, based on a maximum value Δ _Tx of the jitter of the transmitting device and a maximum value Δ _Rx of the jitter of the receiving device, a sample point of the cyclic prefix that is at least 2 (Δ _Tx + Δ _Rx ) samples ahead of an end point of the cyclic prefix identified by the synchronization signal as a start point of the FFT section.
2. The wireless communication system according to claim 1. The transmitting device acquires information indicating a maximum value Δ _Rx of jitter of the receiving device from the receiving device, and sets the length of the cyclic prefix to at least 2 (Δ _Tx + Δ _Rx ) samples or more.
3. The wireless communication system according to claim 2. the transmitting device multiplexes a synchronization signal onto each MIMO channel in a radio frame of the signal, and adds a cyclic prefix to a data signal of each MIMO channel;
the receiving device detects a sample position of the radio frame of each of the MIMO channels using the synchronization signal, and sets an end point of the cyclic prefix of the earliest arriving MIMO channel as a start point of the FFT section;
4. A wireless communication system according to claim 1. The wireless communication system includes a plurality of transmitting devices,
each of the plurality of transmitting devices adds a cyclic prefix to a data signal of each MIMO channel in a radio frame of the signal, and transmits information indicating a maximum value of the jitter to the receiving device;
The receiving device receives information indicating a maximum value of the jitter from each of the plurality of transmitting devices, derives a maximum value Δ _MAX of the jitter for each of the transmitting devices, and sets a start point of the FFT section at least 2×(Δ _MAX + Δ _Rx ) samples ahead of an end point of the cyclic prefix based on the maximum value Δ _Rx of the jitter of the receiving device.
A wireless communication system according to any one of claims 1 to 4. the transmitting device multiplexes a synchronization signal onto a specific MIMO channel in a radio frame of the signal, and adds a cyclic prefix and a cyclic postfix to a data signal of each MIMO channel;
The receiving device sets the end point of the cyclic prefix identified by the synchronization signal as the start point of the FFT section.
A wireless communication system according to any one of claims 1 to 4. the transmitting device multiplexes a synchronization signal into a specific MIMO channel in the radio frame of the signal, adds a cyclic prefix to the data signal of each MIMO channel, and adds a cyclic postfix having a length of at least 2×Δ _Tx samples based on a maximum value Δ _Tx of the jitter of the transmitting device;
The receiving device sets the start point of the FFT section to be at least 2×Δ _Rx samples ahead of the end point of the cyclic prefix identified by the synchronization signal.
A wireless communication system according to any one of claims 1 to 4. A communication method in a wireless communication system including a transmitting device and a receiving device,
a step of the transmitting device transmitting a wireless communication signal to the receiving device;
The receiving device acquires information indicating a maximum value of jitter indicating a sample synchronization capability between antenna ports of the transmitting device, and determines an FFT interval to be used for demodulation or signal equalization of the signal transmitted from the transmitting device based on the maximum value of jitter of the transmitting device and the maximum value of jitter of the receiving device.
Communication methods.

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