Wireless communication system, receiving station, wireless communication method, and program for wireless communication

Abstract

The purpose of the present disclosure is to provide a wireless communication system that can collectively apply MIMO signal processing to reception signals received by a plurality of reception antennas. A wireless communication system according to the present disclosure is provided with a transmitting station, and a receiving station that performs MIMO wireless communication with the transmitting station. The receiving station includes a plurality of reception antennas, one or more synthesis circuits, a synchronization / equalization circuit, and a demodulation circuit. The synthesis circuit synthesizes reception signals of some of the plurality of reception antennas so that synthesized signals equal to or greater than the number of transmission antennas of the transmitting station remain. The synchronization / equalization circuit applies timing synchronization to the synthesized signals, and equalizes the signals in terms of time and frequency domain. The demodulation circuit demodulates the equalized synthesized signals.

Description

Wireless communication system, receiving station, wireless communication method, and wireless communication program

[0001] The present disclosure relates to a wireless communication system, a receiving station, a wireless communication method, and a program for wireless communication.

[0002] Non-terrestrial networks (NTNs) are expected to have many use cases, such as direct accommodation of terrestrial terminals, mobile backhaul, and accommodation of IoT terminals, and are expected to generate more traffic than existing satellite communications (e.g., Non-Patent Document 1). To increase the capacity of the line, a technique has been disclosed for performing MIMO (Multiple-Input and Multiple-Output) wireless communications using multiple antennas installed at an overhead radio station and multiple antennas installed at a terrestrial base station (e.g., Non-Patent Document 2). Alternatively, a method has been proposed for configuring massive MIMO by distributing a large number of small antennas over a wide area at terrestrial base stations (e.g., Non-Patent Document 3).

[0003] Non-Patent Document 4 discloses a technique for inserting dummy frames into radio frames and using the dummy frames to perform timing synchronization and channel estimation for signals received at each receiving antenna, which makes it possible to perform MIMO signal processing while maintaining frequency utilization efficiency.

[0004] 3GPP TR 38.821, 3rd Generation Partnership Project; Technical Specification Group Radio Access Network; Solutions for NR to Support Non-Terrestrial Networks (NTN) (Release 16), V16.1.0, May 2021. A. Knopp, RT Schwarz, D. Ogermann, CA Hofmann and B. Lankl, "Satellite System Design Examples for Maximum MIMO Spectral Efficiency in LOS Channels," IEEE GLOBECOM 2008 - 2008 IEEE Global Telecommunications Conference, 2008, pp. 1-6. Tategami et al., "Proposal of a Hierarchical Base Station Configuration for Ultra-Wideband Massive MIMO Systems," IEICE General Conference, Proceedings of Communications Lectures 1, B-3-5, Mar 2023. Goto et al., "Frame Efficiency Evaluation of LEO-MIMO for DVB-S2X Transmission Systems," IEICE General Conference, Communications Conference Proceedings 1, B-3-4, Mar 2023.

[0005] However, the technique of Non-Patent Document 4 requires MIMO signal processing such as timing synchronization, channel estimation, and equalization to be individually performed on signals received at multiple receiving antennas, which imposes a heavy processing load.

[0006] In order to solve the above-mentioned problems, a first object of the present disclosure is to provide a wireless communication system capable of collectively performing MIMO signal processing on signals received by a plurality of receiving antennas.

[0007] A second object of the present disclosure is to provide a receiving station that can collectively perform MIMO signal processing on signals received at a plurality of receiving antennas.

[0008] A third object of the present disclosure is to provide a wireless communication method capable of collectively performing MIMO signal processing on signals received at a plurality of receiving antennas.

[0009] A fourth object of the present disclosure is to provide a wireless communication program that can collectively perform MIMO signal processing on signals received by a plurality of receiving antennas.

[0010] A first aspect of the present disclosure is preferably a wireless communication system comprising: a transmitting station; and a receiving station that performs MIMO wireless communication with the transmitting station, wherein the receiving station has a plurality of receiving antennas; one or more combining circuits that combine some of the received signals from the plurality of receiving antennas so that a number of combined signals remains that is greater than or equal to the number of transmitting antennas possessed by the transmitting station; a synchronization / equalization circuit; and a demodulation circuit, wherein the synchronization / equalization circuit is configured to perform timing synchronization on the combined signal and to perform equalization in the time and frequency domains; and the demodulation circuit is configured to perform demodulation of the equalized combined signal.

[0011] A second aspect is a receiving station that performs MIMO wireless communication with a transmitting station, and is preferably equipped with: a plurality of receiving antennas; one or more combining circuits that combine some of the received signals from the plurality of receiving antennas so that a total number of combined signals remains that is greater than or equal to the number of transmitting antennas possessed by the transmitting station; a synchronization / equalization circuit; and a demodulation circuit, wherein the synchronization / equalization circuit is configured to perform timing synchronization on the combined signal and to perform equalization processing in the time and frequency domains; and the demodulation circuit is configured to perform processing to demodulate the equalized combined signal.

[0012] A third aspect is preferably a wireless communication method including: a receiving station that uses a plurality of receiving antennas to perform MIMO wireless communication with a transmitting station, combining some of the received signals from the plurality of receiving antennas so that the number of remaining combined signals is greater than the number of transmitting antennas possessed by the transmitting station; performing timing synchronization on the combined signals and equalizing them in the time and frequency domains; and demodulating the equalized combined signals.

[0013] A fourth aspect is preferably a wireless communication program to be executed by a receiving station that performs MIMO wireless communication with a transmitting station using a plurality of receiving antennas, the program including a program that causes the receiving station to execute the following processes: combining some of the received signals from the plurality of receiving antennas so that the number of remaining composite signals is greater than the number of transmitting antennas possessed by the transmitting station; performing timing synchronization on the composite signals and equalizing them in the time and frequency domains; and demodulating the equalized composite signals.

[0014] According to the present disclosure, signals received at multiple receiving antennas are combined using a combining circuit. The combined signal can be regarded as a pseudo-multipath signal, and time-frequency domain equalization can be applied. Therefore, it is possible to provide a wireless communication system, a receiving station, a wireless communication method, and a wireless communication program that can collectively perform MIMO signal processing on signals received at multiple receiving antennas.

[0015] FIG. 1 is a diagram illustrating a configuration example of a wireless communication system according to a first embodiment of the present disclosure. FIG. 2 is a block diagram of a transmitting station according to the first embodiment of the present disclosure. FIG. 3 is a block diagram of a receiving station according to the first embodiment of the present disclosure. FIG. 4 is a flowchart of processing performed by the transmitting station and the receiving station according to the first embodiment of the present disclosure. FIG. 5 is a diagram illustrating a configuration example of a wireless communication system according to a modified example of the first embodiment of the present disclosure. FIG. 6 is a frame format of an information signal transmitted by a transmitting station according to a second embodiment of the present disclosure. FIG. 7 is a block diagram of a transmitting station according to the second embodiment of the present disclosure. FIG. 8 is a diagram illustrating a CP length calculation method performed by a CP length calculation circuit according to the second embodiment of the present disclosure.

[0016] Embodiments of the present disclosure will be described with reference to the drawings. The same or corresponding components will be designated by the same reference numerals, and repeated description may be omitted.

[0017] 1 is a diagram illustrating a configuration example of a wireless communication system 100 according to a first embodiment of the present disclosure. The wireless communication system 100 includes a transmitting station 110 and a receiving station 120. The transmitting station 110 has two transmitting antennas (hereinafter referred to as antennas) 111-1 and 111-2. The receiving station 120 has multiple receiving antennas (hereinafter referred to as antennas) 121-1, 121-2, and so on.

[0018] In the following description, the description can be applied to each of the antennas 111-1, 111-2, etc., and when there is no need to distinguish between them, they will simply be referred to as antenna 111. The same applies to antennas 121-1, 121-2, etc., and lines 10-1, 10-2, etc., lines 20-1, 20-2, etc., which will be described later.

[0019] The multiple antennas 111 of the transmitting station 110 are connected to each of the multiple antennas 121 of the receiving station 120 via line 10 or line 20, and perform MIMO wireless communication using spatial multiplexing. Specifically, the antenna 111-1 connects the antennas 121-1, 121-2, etc. to line 10-1, line 10-2, etc., respectively. Similarly, the antenna 111-2 connects the antennas 121-1, 121-2, etc. to line 20-1, line 20-2, etc., respectively.

[0020] The transmitting station 110 transmits information signals s to the antennas 111-1, 111-2, . １ , s ２ , ... are generated and distributed to the target antennas 111. The antenna 111 transmits the received information signals to the receiving station 120 via the multiple lines 10 or 20 connected to the antenna 111. The receiving station 120 receives the information signals s originating from the antennas 111-1, 111-2, ... １ , s ２ , . . . are received by each antenna 121.

[0021] Although the case where the transmitting station 110 has two antennas 111 has been described here, the number of antennas 111 is not limited as long as it is equal to or greater than the number of information signals to be transmitted. Therefore, if there is one information signal to be transmitted, one antenna 111 may be sufficient.

[0022] 2 is a block diagram of a transmitting station 110 according to the first embodiment of the present disclosure. A transmission signal generating circuit 112 generates an information signal s to be transmitted. １ , s ２ , ..., performs signal processing such as S / P (Serial to Parallel) conversion, error correction coding, modulation, etc. The modulation method used is a method that allows equalization in the time and frequency domains at the receiving station 120, such as OFDM, spectrum spread, DFTs (Discrete Fourier Transform-spread)-OFDM, etc. The transmission signal generation circuit 112 generates the information signal s １ , s ２ , . . . are distributed to the target antennas 111.

[0023] 3 is a block diagram of the receiving station 120 according to the first embodiment of the present disclosure. Each antenna 121 guides radio waves that reach it and converts them into power signals. The power signals at each antenna 121 are converted into optical signals by an electro-optical (EO) converter 122 specific to each antenna 121 and transmitted to a receiver 123 via an optical fiber. The receiver 123 converts the received optical signals back into power signals. In this way, the radio waves that reach the antenna 121 are received. Hereinafter, the radio waves converted into power signals by the receiver 123 specific to each antenna 121 will be referred to as the received signals at each antenna 121.

[0024] Here, the radio-on-fiber technology has been described as being used to convert the power signal at each antenna 121 into an optical signal and then transmit it to the receiver 123. Using optical fiber can reduce transmission loss, which is particularly useful when the distance from the antenna 121 to the receiver 123 is long. However, the power signal at each antenna 121 does not necessarily have to be converted into an optical signal, and may be transmitted to the receiver 123 using a coaxial cable or the like.

[0025] The signals received by each antenna 121 are transmitted to a combining circuit 124 connected to a specific destination for each antenna 121. Each of the multiple combining circuits 124 combines some of the signals received from the multiple antennas 121 to generate a combined signal.

[0026] For example, combining circuit 124-1 combines received signals for a first combination of antennas 121-1, 121-3, and 121-5, while combining circuit 124-2 combines received signals for a second combination of antennas 121-2, 121-4, and 121-6.

[0027] Here, the number of synthesis circuits 124 is N ｍｉｎ , where N is the number of antennas 111 of the transmitting station 110, N ｍｉｎ ≧N. This is because the demodulation circuit 126, which will be described later, demodulates the plurality of information signals s included in the composite signal. １ , s ２ , ..., the number of combined signals required is greater than the number of information signals to be separated. Therefore, if the transmitting station 110 has one antenna 111, only one combining circuit 124 is required.

[0028] The synchronization and equalization circuit 125 performs timing synchronization on the combined signal received from the combining circuit 124 connected thereto, and performs equalization in the time and frequency domains. The demodulation circuit 126 receives the combined signal from each of the synchronization and equalization circuits 125, performs channel estimation on the combined signal, and extracts a plurality of information signals s included in the combined signal. １ , s ２ , .... Furthermore, the demodulation circuit 126 demodulates the combined signal.

[0029] When there is only one information signal to be separated, the demodulation circuit 126 does not separate the combined signal.

[0030] In this manner, in the present disclosure, the combined signal generated in each combining circuit 124 is subjected to MIMO signal processing such as timing synchronization, channel estimation, and equalization.

[0031] Next, a description will be given of the combined signal generated in the combining circuit 124. Here, the information signal s is transmitted from the antennas 111-1 and 111-2 of the transmitting station 110. １ , s ２ are transmitted, and the information signals s １ , s ２ The following description will be given taking the case where the following is received as an example.

[0032] First, the power r of the received signal at the kth antenna 121-k is ｋ can be written as follows:

[0033]

[0034] where t is time and τ ｋ is an offset time that differs for each antenna 121. １ (t), s ２ (t) is the information signal s at time t １ , s ２ Indicates the power of

[0035] Here, combining circuit 124 combines the received signals from each antenna 121 without timing synchronization. In this case, in combining circuit 124-1 that combines received signals for the first combination of antennas 121-1, 121-3, and 121-5, the power of the combined signal is as follows:

[0036]

[0037] Since timing synchronization is not performed on the received signals at each antenna 121, in (Equation 2), the offset time τ ｋ The information signal s １ , s ２ Note that the are added together.

[0038] Similarly, in combining circuit 124-2 that combines received signals for a second combination of antennas 121-2, 121-4, and 121-6, the power of the combined signal is as follows:

[0039]

[0040] Here, the first term on the right side of (Equation 2) is the information signal s １ The first term is the sum of the received power of the information signal s １ The second term can also be considered as an information signal s ２ can be considered as a state in which the signals interfere in the time domain. １ ｓｕｍ can be regarded as a pseudo multipath signal. ２ ｓｕｍ The same is true for .

[0041] Based on the finding that time-frequency domain equalization used in OFDM or spectrum spread, etc., can be applied to a composite signal having such characteristics, in this disclosure, time-frequency domain equalization processing is performed on the composite signal.

[0042] The synchronization process here is performed by synchronizing the synthesized signal r １ ｓｕｍ from the offset time τ ｋ or the offset time τ ｋ This means that the synthesized signal r ２ ｓｕｍ The same is true for .

[0043] 4 is a flowchart of a process executed by the transmitting station 110 and the receiving station 120 according to the first embodiment of the present disclosure. １ , s ２ , ... and distributes them to the target antennas 111 (step S01). Next, the antennas 111 transmit the received information signals to the receiving station 120 via the line 10 or line 20 connected to the antennas 111 (step S02).

[0044] Furthermore, the receivers 123 connected to the antennas 121 of the receiving station 120 receive the information signals (step S03). Each of the combining circuits 124 combines some of the received signals from the multiple antennas 121 to generate a combined signal (step S04). Next, the synchronization and equalization circuit 125 performs timing synchronization on the combined signal received from the combining circuit 124 connected thereto, and further performs equalization in the time and frequency domains (step S05). Furthermore, the demodulation circuit 126 demodulates the multiple information signals s included in the combined signal. １ , s ２ , ... are separated and demodulated (step S06). Finally, the process ends.

[0045] As described above, according to the present disclosure, received signals from multiple antennas 121 are combined by combining circuit 124. The combined signal can be considered a pseudo-multipath signal, and time-frequency domain equalization can be applied to the combined signal. Therefore, it is possible to provide a wireless communication system, a receiving station, a wireless communication method, and a wireless communication program that can collectively perform MIMO signal processing on received signals received by multiple receiving antennas.

[0046] The wireless communication system 100 of the present disclosure also exhibits the above-described effects when applied to an NTN system. For example, the transmitting station 110 is an airborne wireless station such as a satellite moving in the sky, including outer space, and the receiving station 120 is a terrestrial base station. The lines 10 and 20 are feeder link lines.

[0047] <Modification of First Embodiment> Figure 5 is a diagram showing an example configuration of a wireless communication system 100 according to a modification of the first embodiment of the present disclosure. The wireless communication system 100 includes a transmitting station 110 as a terrestrial base station and a receiving station 120 connected to multiple satellites 130. Here, an example is shown in which three satellites 130-1, 130-2, and 130-3 are distributed with respect to the receiving station 120. Distributing the satellites 130 in this manner is known from LEO (Low Earth Orbit) satellite constellations and the like.

[0048] Antennas 121 of receiving stations 120 are arranged on each satellite 130. The signals received by each antenna 121 are transmitted via optical link 30 to combining circuits 124, each of which is connected to a specific antenna 121. Each of the two combining circuits 124 combines the received signals for the combination of antennas 121 selected one by one from each satellite 130. The above-mentioned MIMO signal processing is then carried out in the subsequent synchronization / equalization circuit 125 and demodulation circuit 126. This achieves the same effects as in embodiment 1.

[0049] The combining circuit 124, synchronization and equalization circuit 125, and demodulation circuit 126 may be located in one of the satellites 130. In this case, however, it is necessary to connect the multiple satellites 130 with optical links 30 and transmit the signals received at each antenna 121 to the satellite 130 in which the circuits are located.

[0050] Second Embodiment In this embodiment, a frame of an information signal includes a preamble 51 for timing synchronization and a pilot symbol 53. The following describes the changes from the first embodiment.

[0051] 6 shows the frame format of an information signal transmitted by a transmitting station 110 according to the second embodiment of the present disclosure. The information signal has a frame format similar to that of a burst frame used in a wireless LAN (Local Area Network) and LTE (Long Term Evolution). That is, the information signal includes a preamble 51, data symbols 52, and pilot symbols 53 in one frame. The symbols here are, for example, OFDM symbols. The number of preambles 51, data symbols 52, and pilot symbols 53 in one frame, as well as the spacing between the pilot symbols 53, are not limited.

[0052] A guard interval (cyclic prefix, CP) is inserted at the beginning of each symbol.

[0053] 7 is a block diagram of a transmitting station 110 according to a second embodiment of the present disclosure. A CP length calculation circuit 113 calculates a CP length to be provided in a frame of an information signal to be transmitted, based on location information of the transmitting station and the receiving station 120, using a method described below. A location information acquisition circuit 114 acquires location information of the transmitting station and the receiving station 120 using GPS or the like. In addition to the processing described in the first embodiment, the transmission signal generation circuit 112 further performs processing to provide the CP length calculated by the CP length calculation circuit 113 to the symbols of the information signal to be transmitted.

[0054] Meanwhile, in the receiving station 120, a synchronization and equalization circuit 125 performs timing synchronization based on a preamble 51 included in the information signal, and a demodulation circuit 126 performs channel estimation based on a pilot symbol 53 included in the information signal.

[0055] In this way, by including the preamble 51 for synchronization and the pilot symbol 53 for channel estimation in the frame of the information signal, it is possible to reduce the time required for MIMO signal processing in the receiving station 120. Therefore, this is particularly useful when MIMO signal processing must be performed in a short time, such as when at least one of the transmitting station 110 and the receiving station 120 is a mobile station.

[0056] Although the information signal is described above as being a burst frame transmitted at regular intervals, the information signal may be a continuous frame if the transmitting station 110 that transmits the information signal is not a mobile station, or if it appears to be stationary relative to the Earth, such as a geostationary satellite.

[0057] Although the symbols are described above as OFDM symbols, any method that allows equalization in the time and frequency domains may be used, and symbols in a single-carrier method such as DFTs-OFDM or SC-FDE (Single-Carrier Modulation with Frequency Domain Equalization) may also be used.

[0058] 8 is a diagram illustrating a CP length calculation method performed by the CP length calculation circuit 113 according to the second embodiment of the present disclosure. The CP length calculation circuit 113 (not shown) calculates the line lengths of the lines 10 and 20 connecting the local station with the receiving station 120 based on the position information of the local station and the receiving station 120. Here, the line length of the line 10-N connecting the antenna 111-1 and the antenna 121-N of the lines 10 and 20 is the maximum D ｍａｘ In addition, the line length of the line 10-1 connecting the antenna 111-1 and the antenna 121-1 is the smallest D ｍｉｎ It is said that this is the case.

[0059] The CP length calculation circuit 113 calculates the arrival time difference Δ of the information signal between the antenna 121-N in charge of the line 10-N with the longest line length and the antenna 121-1 in charge of the line 10-1 with the shortest line length. The arrival time difference Δ is calculated by using the line length difference and the speed of light c as follows: ((D ｍａｘ -D ｍｉｎ ) / c). The CP length calculation circuit 113 determines the CP length so as not to exceed the calculated arrival time difference Δ. This allows the delay time, which is the difference between the information signal that arrives at the receiving station 120 the earliest and the information signal that arrives at the receiving station 120 the latest, to be within the CP length, and the receiving station 120 can normally equalize the combined signal.

[0060] If the distance from the antenna 121 to the receiver 123 is long, the line length from each antenna 121 to the receiver 123 may be taken into consideration in addition to the line lengths of the lines 10 and 20 .

[0061] The processes performed by the combining circuit 124, synchronization / equalization circuit 125, and demodulation circuit 126 of the receiving station 120 and the processes performed by the CP length calculation circuit 113 of the transmitting station 110 may be executed by a program using a computer equipped with a CPU and memory and storing a program in the memory. Alternatively, the processes may be executed by a program using an integrated circuit such as an FPGA (Field Programmable Gate Array). The program may be provided by being recorded on a storage medium or via a network. This point is common to all the embodiments.

[0062] The present disclosure is not limited to the above-described embodiments, and various modifications can be made in the implementation stage without departing from the spirit of the present disclosure. Furthermore, the embodiments may be implemented in appropriate combinations, and in such cases, the combined effects can be obtained.

[0063] Aspects of the present disclosure are summarized below as appendices: (Appendix 1) A wireless communication system comprising: a transmitting station; and a receiving station that performs MIMO wireless communication with the transmitting station, wherein the receiving station has: a plurality of receiving antennas; one or more combining circuits that combine some of the received signals from the plurality of receiving antennas so that the number of combined signals remaining is equal to or greater than the number of transmitting antennas of the transmitting station; a synchronization and equalization circuit; and a demodulation circuit, wherein the synchronization and equalization circuit is configured to perform timing synchronization on the combined signal and perform equalization in the time and frequency domains, and the demodulation circuit is configured to perform demodulation of the equalized combined signal. (Supplementary Note 2) The wireless communication system according to Supplementary Note 1, wherein the transmitting station is further configured to perform the following processes: calculating the line lengths of the lines connecting the transmitting antennas of the transmitting station to the receiving antennas based on location information of the transmitting station and the receiving station; calculating the arrival time difference of the information signal at the receiving antenna responsible for the line with the longest line length and the receiving antenna responsible for the line with the shortest line length; and transmitting the information signal via the lines after adding a cyclic prefix length of a length not exceeding the arrival time difference to the symbols of the information signal to be transmitted. (Supplementary Note 3) A receiving station that performs MIMO wireless communication with a transmitting station, comprising: a plurality of receiving antennas, one or more combining circuits that combine some of the received signals from the plurality of receiving antennas so that a total number of combined signals equal to or greater than the number of transmitting antennas possessed by the transmitting station, a synchronization / equalization circuit, and a demodulation circuit, wherein the synchronization / equalization circuit is configured to perform timing synchronization on the combined signal and perform equalization in the time and frequency domains, and the demodulation circuit is configured to perform demodulation on the equalized combined signal. (Supplementary Note 4) A wireless communication method in which a receiving station that performs MIMO wireless communication with a transmitting station using a plurality of receiving antennas comprises: combining some of the received signals from the plurality of receiving antennas so that a total number of combined signals equal to or greater than the number of transmitting antennas possessed by the transmitting station remains, performing timing synchronization on the combined signal and equalizing it in the time and frequency domains, and demodulating the equalized combined signal.(Supplementary Note 5) A wireless communication program to be executed by a receiving station that performs MIMO wireless communication with a transmitting station using a plurality of receiving antennas, the program including a program that causes the receiving station to execute the following processes: combining some of the received signals from the plurality of receiving antennas so that the number of remaining combined signals is equal to or greater than the number of transmitting antennas possessed by the transmitting station; performing timing synchronization on the combined signals and equalizing them in the time and frequency domains; and demodulating the equalized combined signals.

[0064] 10, 20 Line, 30 Optical link, 51 Preamble, 52 Data symbol, 53 Pilot symbol, 100 Wireless communication system, 110 Transmitting station, 111 Transmitting antenna, 112 Transmit signal generating circuit, 113 CP length calculation circuit, 114 Position information acquisition circuit, 120 Receiving station, 121 Receiving antenna, 122 EO converter, 123 Receiver, 124 Combining circuit, 125 Synchronization and equalization circuit, 126 Demodulation circuit, 130 Satellite

Claims

1. A wireless communication system comprising a transmitting station and a receiving station that performs MIMO wireless communication with the transmitting station. The receiving station includes a plurality of receiving antennas, one or more combining circuits that combine some of the received signals among the plurality of receiving antennas so that a combined signal remains that is equal to or greater than the number of transmitting antennas of the transmitting station, a synchronization / equalization circuit, and a demodulation circuit. The synchronization / equalization circuit is configured to perform processing for timing synchronization on the combined signal and equalization in the time and frequency domains, and the demodulation circuit is configured to perform processing for demodulating the equalized combined signal.

2. A receiving station that performs MIMO wireless communication with a transmitting station, comprising a plurality of receiving antennas, one or more combining circuits that combine some of the received signals among the plurality of receiving antennas so that a combined signal remains that is equal to or greater than the number of transmitting antennas of the transmitting station, a synchronization / equalization circuit, and a demodulation circuit. The synchronization / equalization circuit is configured to perform processing for timing synchronization on the combined signal and equalization in the time and frequency domains, and the demodulation circuit is configured to perform processing for demodulating the equalized combined signal.

3. A wireless communication method including: combining some of the received signals among a plurality of receiving antennas so that a combined signal remains that is equal to or greater than the number of transmitting antennas of a transmitting station when performing MIMO wireless communication with the transmitting station using the plurality of receiving antennas; performing timing synchronization on the combined signal and equalization in the time and frequency domains; and demodulating the equalized combined signal.

4. A wireless communication program to be executed by a receiving station that performs MIMO wireless communication with a transmitting station using a plurality of receiving antennas, the program including causing the receiving station to perform processing for combining some of the received signals among the plurality of receiving antennas so that a combined signal remains that is equal to or greater than the number of transmitting antennas of the transmitting station, processing for performing timing synchronization on the combined signal and equalization in the time and frequency domains, and processing for demodulating the equalized combined signal.

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