JP4869407B2 - MIMO communication system - Google Patents

Description

  The present invention relates to a MIMO communication system that efficiently uses radio resources for pilot signals.

  In recent years, the shortage of radio wave resources in mobile communications has become serious, while the demand for high-speed and high-capacity wireless broadband has been increasing day by day. Under these circumstances, use of high frequency band / wideband frequency and repeated use at one frequency are required.

  However, the use of high-frequency and broadband frequencies makes the cell radius very small, and in order to consider the repeated use of one frequency, a communication method that avoids cell-sector interference is urgently required. . In this case, it is necessary to consider interference avoidance between cells and sectors in pilot signal mapping.

  Further, in mobile communication, a MIMO (Multi Input Multi Output) communication method has been gradually introduced as a method for dramatically improving the transmission capacity. Accordingly, it is necessary to consider interference avoidance between transmission antennas also in mapping of pilot signals.

  In the mobile communication system, it is very important to design an efficient pilot mapping method that suppresses the degradation of the transmission path estimation value and minimizes the overhead due to the pilot signal mapping in response to the above requirements.

  In such a background, there is a conventional technique related to a wireless multicarrier communication system in which a plurality of base stations transmit pilot signals in the downlink (see, for example, Patent Document 1). In Patent Document 1, in order to perform frequency orthogonality, time orthogonality (for example, by using an orthogonal code), or coherent data demodulation, soft handoff, and hard handoff, frequency and time orthogonality. It is described that pilot signals that are orthogonal to each other are used by using both.

  In the IEEE 802.16e-2005 specification (see, for example, Non-Patent Document 1), when performing MIMO communication, the pilot signal to be used is divided into subcarriers (frequency direction) and symbols (time direction) for each antenna. In addition, orthogonality is provided between pilot signals to realize MIMO communication in a mobile communication environment.

JP-T-2006-517759 IEEE Std 802.16e-2005 and IEEE Std 802.16-2004 / Cor1-2005, “Air Interface for Fixed and Mobile Broadband Wireless Access Systems”, 2006.

However, the prior art has the following problems.
In the pilot signal transmission, a conventional method for simultaneously avoiding cell-sector interference and interference between transmission antennas in MIMO communication is a method of taking orthogonality in the frequency direction or time-divisional orthogonality in the time direction. Possible ways to take. However, these methods have a problem that in many radio resources, that is, in a radio multicarrier communication system, many subcarriers are consumed for pilot signals, resulting in a large overhead.

  In addition, when orthogonality is taken in the time direction using orthogonal codes, there is a problem that it is not possible to cope with movement of the terminal, or that free mapping in the time direction as shown in the IEEE 802.16e specification is restricted. It was.

  The present invention has been made in view of the above, and efficiently avoids radio interference for pilot signals while simultaneously avoiding cell-sector interference and interference between transmission antennas in MIMO communication in pilot signal transmission. It aims at obtaining the MIMO communication system to utilize.

  The MIMO communication system according to the present invention is a communication system that performs communication between a plurality of transmission-side communication devices and one or more reception-side communication devices located in a place where transmission target areas of the plurality of transmission-side communication devices overlap. A plurality of transmitting side communication devices change communication methods by dynamically assigning usable pilot signals based on radio channel quality information using pilot signals reported from one or more receiving side communication devices. Then, when two or more pilot signals are assigned, MIMO communication is performed, and one or more receiving-side communication apparatuses change reception processing based on radio channel quality information using the pilot signals, and perform a plurality of transmissions. The combined signal from the side communication side device is separated by the MIMO reception process, and the interference signal from the other cell / sector is discarded.

  According to the present invention, in the pilot signal transmission by dynamically allocating the pilot signal based on the wireless channel quality information between the transmission side communication device and the reception side communication device and selecting the optimum communication method, It is possible to obtain a MIMO communication system that efficiently uses radio resources for pilot signals while simultaneously avoiding interference between cells and sectors and interference between transmission antennas in MIMO communication.

It is a block diagram of the communication system in Embodiment 1 of this invention. It is an illustration figure of pilot signal arrangement | positioning in Embodiment 1 of this invention. It is a cell structural example of the transmission side communication apparatus in Embodiment 1 of this invention. It is explanatory drawing of the MIMO reception process in Embodiment 1 of this invention. It is explanatory drawing of the MIMO reception process in Embodiment 1 of this invention. It is another explanatory drawing of the MIMO reception process in Embodiment 1 of this invention. It is another explanatory drawing of the MIMO reception process in Embodiment 1 of this invention. It is another illustration figure of the pilot signal arrangement | positioning in Embodiment 1 of this invention. It is a block diagram of the communication system in Embodiment 2 of this invention. It is explanatory drawing regarding the zone division at the time of the pilot signal transmission in Embodiment 3 of this invention.

  Hereinafter, preferred embodiments of a MIMO communication system of the present invention will be described with reference to the drawings.

Embodiment 1 FIG.
In the first embodiment, a configuration of a multicarrier communication system that realizes a downlink MIMO communication system while linking a plurality of transmission side communication apparatuses, effectively using pilot signals, and avoiding cell-sector interference. explain. In the following description, only portions related to downlink communication are extracted and detailed.

  FIG. 1 is a configuration diagram of a MIMO communication system according to Embodiment 1 of the present invention. The MIMO communication system according to the first embodiment includes a host device 11, a plurality of transmission side communication devices 31 and 32, and a reception side communication device 51.

  In FIG. 1, a higher-level device 11 on the transmission side is a device arranged above the plurality of transmission-side communication devices 31 and 32, and represents, for example, a base station control device in mobile communication. In FIG. 1, only two internal configurations of the first transmission side communication device 31 and the second transmission side communication device 32 are illustrated as a plurality of transmission side communication devices for the sake of simplicity.

  In the following description, a case will be described in which a plurality of transmission side communication apparatuses are configured with two units. However, in reality, a large number of transmission side communication devices are connected, and the same can be considered for a large number of cases. The plurality of transmission side communication devices 31 and 32 communicate with the reception side communication device 51 via the communication paths 41 and 42, respectively.

  In addition, in the example of FIG. 1, only one receiver communication device 51 is described for the sake of simplicity, but in reality, a large number of receiver communication devices are connected wirelessly. In the following description, a processing example of one receiving-side communication device 51 will be described. However, the processing is not limited to one, and the same can be considered for many cases.

  The host device 11 and the plurality of transmission side communication devices 31 and 32 may be connected by wire or wirelessly. In addition, even if it is the structure by which a part of function of the high-order apparatus 11 is arrange | positioned in several transmission side communication apparatuses 31 and 32, or the structure integrated with several transmission side communication apparatuses 31 and 32, it is. I do not care.

  Here, the plurality of transmission side communication devices 31 and 32 indicate, for example, a base station in mobile communication or a set of units for performing sector transmission within the base station. For example, the plurality of transmission side communication devices 31 and 32 may be devices that perform 2 · 2 MIMO communication. That is, a plurality of transmission side communication devices 31 and 32 are arranged at different positions, or are installed so that the transmission beam directions are different as in the above-mentioned sector transmission, so that the transmission target areas are different. And

  The first transmission side communication device 31 includes a data storage unit 311, an encoding / frame mapping unit 312, a modulation unit 313, a demodulation / decoding unit 314, an ACK / NACK processing unit 315, a quality information processing unit 316, and a transmission scheduling unit. 317. Similarly, the second transmission side communication device 32 includes a data storage unit 321, an encoding / frame mapping unit 322, a modulation unit 323, a demodulation / decoding unit 324, an ACK / NACK processing unit 325, a quality information processing unit 326, and The transmission schedule unit 327 is configured.

  The ACK / NACK processing units 315 and 325 are functions required when ARQ (including Hybrid ARQ) is operated between the plurality of transmission side communication devices 31 and 32 and the reception side communication device 51. If the ARQ is not operated, it may be omitted.

  The receiving-side communication device 51 is a device capable of MIMO reception, and indicates, for example, a mobile terminal in mobile communication. The reception-side communication device 51 includes a demodulation / decoding unit 511, a user information reception processing unit 512, a quality information processing unit 513, and an encoding / frame mapping / modulation unit 514.

  Next, a flow of processing will be described for a downlink MIMO communication scheme in which a plurality of transmission side communication devices 31 and 32 in Embodiment 1 are linked to achieve effective use of pilot signals.

  The host device 11 transmits user data 211 and 221 and control signals 212 and 222 for controlling the transmission side communication devices 31 and 32, for example, in the form of IP packets. The host apparatus 11 notifies the transmission side communication apparatuses 31 and 32 of the pilot signal index numbers that can be used for a certain period of time by the control signals 212 and 222.

  Here, it is assumed that pilot signals having different indexes have a frequency orthogonality, a time orthogonality, or a combination thereof. A method in which the higher-level device 11 selects a pilot signal that can be used for the plurality of transmission-side communication devices 31 and 32 and a MIMO communication method after assigning the pilot signal will be described later.

  The transmission side communication devices 31 and 32 that have received the user data 211 and 221 queue transmission data in the data storage units 311 and 321, respectively. Next, the encoding / frame mapping units 312 and 322 perform mapping to radio frames on the user data queued by the data storage units 311 and 321 in accordance with instructions from transmission schedule units 317 and 327 described later. .

  At this time, the encoding / frame mapping units 312 and 322 perform error correction encoding as necessary, and after performing transmission diversity processing, STC (Space Time Coding) processing, SM (Spatial Multiplexing) MIMO processing, and the like. Perform mapping to radio frame.

  Furthermore, the encoding / frame mapping units 312 and 322 also perform mapping of pilot signals to radio frames in accordance with instructions from the transmission scheduling units 317 and 327 simultaneously with the user data mapping process. Then, the modulation units 313 and 323 perform digital modulation processing such as BPSK, QPSK, and multilevel QAM on the mapping data, and convert it to the time axis by IFFT, and then the user data via the communication paths 41 and 42. The signals 411 and 421 are transmitted to the receiving communication device 51.

  The demodulation / decoding unit 511 in the reception-side communication device 51 converts the modulation signals (user data signals 411 and 421) received via the communication channels 41 and 42 into a frequency axis by FFT, and MIMO reception described later. Processing and error correction decoding are performed, and the result is passed to the user information reception processing unit 512.

  For example, when the user information reception processing unit 512 delivers the user data 61 to the application layer and operates ARQ between the transmission side communication devices 31 and 32 and the reception side communication device 51, the user information reception processing unit 512 receives ACK / The NACK information is transferred to the encoding / frame mapping / modulation unit 514. The encoding / frame mapping / modulation unit 514 transmits the ACK / NACK information passed from the user information reception processing unit 512 to the transmission side communication devices 31 and 32 via the wireless communication paths 41 and 42.

  In addition, the demodulation / decoding unit 511 in the reception-side communication device 51 passes the demodulated preamble signal and pilot signal to the quality information processing unit 513. The quality information processing unit 513 uses the demodulated preamble signal and pilot signal as communication channel quality information, such as RSSI (Received Signal Strength Indicator), CINR (Carrier-to-Interference plus Noise Ratio), and the like. And is passed to the encoding / frame mapping / modulation unit 514.

  The encoding / frame mapping / modulation unit 514 transmits the quality information 413 and 423 transferred from the quality information processing unit 513 to the transmission-side communication devices 31 and 32 via the wireless communication paths 41 and 42.

  When receiving the ACK / NACK information 412, 422, the transmitting communication devices 31, 32 ACK the transmission scheduling units 317, 327 via the demodulation / decoding units 314, 324 and the ACK / NACK processing units 315, 325. / NACK information is input. The transmission schedule units 317 and 327 instruct the data storage units 311 and 321 to transmit retransmission data when NACK information is received, and perform a buffer clear instruction when ACK information is received.

  Further, when receiving the quality information 413, 423, the transmission side communication devices 31, 32 communicate with the transmission schedule units 317, 327 via the demodulation / decoding units 314, 324 and the quality information processing units 316, 326, respectively. Enter quality information. The transmission schedule units 317 and 327 notify the quality information 213 and 223 of the respective communication channels 41 and 42 to the higher-level device 11 and communicate with the communication device 51 on the receiving side, MCS (Modulation and Coding Scheme). Determine the level.

  Next, the host apparatus 11 according to the first embodiment selects a pilot signal that can be used for the transmission side communication apparatuses 31 and 32, and the MIMO reception of the reception side communication apparatus 51 after assigning the pilot signal. An example of the method will be described with reference to FIGS.

  FIG. 2 is an exemplary diagram of pilot signal arrangement in Embodiment 1 of the present invention, and more specifically shows IEEE 802.16e DL PUSC 4 · 4 MIMO pilot signal arrangement. As an example, a case where the signal arrangement shown in FIG. 2 is applied to the first embodiment will be described.

  FIG. 3 is a cell configuration example of a plurality of transmission side communication apparatuses according to Embodiment 1 of the present invention. More specifically, FIG. 3 shows a cell configuration when omni transmission is performed using the transmission side communication apparatus as one radio base station. It is an example. Here, it is assumed that each of the transmission side communication devices 31 to 37 has a plurality of antennas. In order to simplify the description, it is assumed below that each transmission-side communication device 31 to 37 has two antennas.

  In addition, one pilot signal is fixedly assigned in advance to each of the transmission side communication devices 31 to 37 (any one of Pilots # 0 to # 2 is fixedly assigned), Pilot # 3 will be described as being dynamically allocated additionally by a control signal from the host apparatus 11 in the configuration of FIG. However, this Embodiment 1 is not limited to assigning a pilot signal fixedly with respect to each transmission side communication apparatuses 31-37.

  The higher-level device 11 reports each transmission-side communication device reported from each reception-side communication device 51 in an active state within an area, for example, in the area covered by the transmission-side communication devices 31 to 37 in FIG. Quality information (RSSI, CINR, etc.) for 31 to 37 is acquired. Here, each receiving-side communication device 51 obtains quality information of each pilot signal and reports it to the higher-level device 11 via the transmitting-side communication devices 31 to 37 of its own cell.

  Based on this report, the host device 11 responds to the transmission side communication devices 31 to 37 in which many reception side communication devices 51 whose quality information values (for example, RSSI values) of the own cell are equal to or greater than a predetermined threshold are distributed. Then, an additional pilot signal Pilot # 3 is allocated. Note that the higher-level device 11 may assign the additional pilot signal Pilot # 3 in order by the transmission-side communication devices 31 to 37 regardless of the quality information of each reception-side communication device 51.

  For example, when the higher order apparatus 11 assigns the pilot signal Pilot # 3 to the transmission side communication apparatus 31, in order to avoid interference of pilot signals in the adjacent transmission side communication apparatuses 32-37, the pilot apparatus # 3 The other transmission side communication devices 32 to 37 are not assigned.

  That is, the transmission side communication device 31 to which two pilot signals are allocated enables 2 · 2 SM MIMO communication, and the transmission side communication devices 32 to 37 use only one pilot and transmit diversity using two antennas. Or beamforming transmission.

  In this case, the MIMO reception method of the reception side communication device 51 in the transmission side communication device 31 area when the quality information value is an RSSI value is as follows. 4 and 5 are explanatory diagrams of the MIMO reception process according to the first embodiment of the present invention, and two cases (cases 1 and 2) will be described based on these drawings.

(Case 1) As shown in FIG. 4, the RSSI value of the own cell (that is, the RSSI values of the two pilot signals Pilot # 0 and # 3 assigned to the transmitting side communication device 31) is the RSSI value of the other cell (that is, The communication quality for the own cell is determined in advance in comparison with the communication quality for the other cells (ie, the RSSI values of the other two pilot signals Pilot # 1 and # 2). The reception side communication device 51 in the area of the transmission side communication device 31 uses the pilot signal of its own cell as the control signal from the transmission side communication device 31, and 2 · 2 SM MIMO. Perform reception processing.

  Note that a receiving communication apparatus that does not have a sufficient RSSI value may be recognized on the transmitting communication apparatus 31 side, and transmission to the receiving communication apparatus may be switched to diversity transmission or beam forming transmission. In this case, the receiving-side communication device 51 performs reception diversity processing.

(Case 2) As shown in FIG. 5, when the RSSI value of the own cell is not so different from one of the RSSI values of other cells (RSSI value of Pilot # 1) (that is, the communication quality for other cells is predetermined permissible) When the difference is higher than the value and the difference from the communication quality for the own cell is not more than a predetermined value as shown in FIG. 5), the receiving communication device 51 in the area of the transmitting communication device 31 uses three pilot signals. After performing 3.3 SM MIMO reception processing, information from other cells is discarded.

  In addition, when the number of antennas of the receiving communication device is 2, or when the receiving communication device is not a sufficient RSSI value, the transmitting communication device 31 recognizes it and transmits to the receiving communication device. You may switch to diversity transmission or beamforming transmission. In this case, after performing the 2 · 2 SM MIMO reception processing, information from other cells is discarded.

  On the other hand, there are the following two cases (cases 3 and 4) for the MIMO reception method of the reception side communication device 51 in the transmission side communication device 32-37 area. FIGS. 6 and 7 are other explanatory diagrams of the MIMO reception process in Embodiment 1 of the present invention, and two cases (cases 3 and 4) will be described based on these drawings. In cases 3 and 4, the pilot signal of the own cell is Pilot # 1.

(Case 3) As shown in FIG. 6, when the RSSI value of the own cell is very large with respect to the RSSI value of the other cell (that is, compared with the communication quality for the other cell, the communication quality for the own cell) Is greater than a predetermined tolerance and the difference between the two is large), the receiving side communication device 51 in the transmitting side communication device 32 to 37 area performs reception diversity processing.
(Case 4) As shown in FIG. 7, when the RSSI value of the own cell is not so different from one of the RSSI values of the other cell (that is, the communication quality for Pilot # 0 of the other cell and the Pilot # 1 of the own cell) When the difference between the communication quality is small and both RSSI values are equal to or larger than the predetermined allowable value), the receiving side communication device 51 in the transmitting side communication device 32-37 area has two in the example of FIG. After performing 2 · 2 SM MIMO reception processing using the pilot signal, information from other cells is discarded.

  In FIG. 2, an example using the IEEE 802.16e DL PUSC 4 · 4 MIMO pilot signal arrangement has been described. However, as already described, orthogonal pilot signals may be divided by time orthogonal using orthogonal codes. . FIG. 8 is another exemplary diagram of pilot signal arrangement in Embodiment 1 of the present invention. More specifically, FIG. 8 is based on or is based on IEEE 802.16e DL PUSC 4 · 4 MIMO pilot signal arrangement. An example of a deformed cluster structure is shown.

  In the first embodiment, depending on the position of the receiving-side communication device 51, signals from other cells and sectors do not become interference components, so the use of pilot signals becomes more efficient by using orthogonal codes.

  As described above, according to the first embodiment, in a higher-level device arranged at a higher level of a plurality of transmission-side communication devices, based on the wireless channel quality information between the transmission-side communication device and the reception-side communication device. A pilot signal is dynamically allocated to determine a communication method and an MCS level. As a result, in a system that repeatedly uses one frequency, the number of SM MIMO streams can be dynamically changed between cells and sectors while significantly reducing interference from other cells and sectors while minimizing the overhead caused by pilot signals. It becomes possible to switch to.

Embodiment 2. FIG.
FIG. 9 is a configuration diagram of a communication system according to Embodiment 2 of the present invention. The communication system according to the second embodiment includes a host device 11, a plurality of transmission-side communication devices 31, 32, and a reception-side communication device 51, and the basic configuration is the same as that in FIG. It is.

  However, in comparison with FIG. 1 in the first embodiment, in the configuration of FIG. 9 in the second embodiment, control signals 212, 222 transmitted from the host device 11 to the transmission side communication devices 31, 32, and Quality information 213 and 223 transmitted from the transmission side communication devices 31 and 32 to the higher level device 11 is not required, and the transmission scheduling units 317 and 327 in the transmission side communication devices 31 and 32 transmit pilot signals that are used autonomously. The decision point is different.

  Next, in the second embodiment, the transmission schedule units 317 and 327 in the transmission side communication devices 31 and 32 autonomously select pilot signals that can be used for the transmission side communication devices 31 and 32. An example will be described with reference to FIGS. 2 to 5 as in the description of the first embodiment.

  The description regarding FIG. 2 and FIG. 3 is substantially the same as the description in the first embodiment. However, in this Embodiment 2, Pilot # 3 differs in the point by which the transmission side communication apparatuses 31-37 are autonomously allocated to an own cell.

  As shown in FIG. 4, each of the transmission side communication devices 31 to 37 indicates that a large number of reception side communication devices 51 whose own cell quality information values (for example, RSSI values) are equal to or greater than a predetermined threshold are distributed. When it is recognized, there are a large number of receiving side communication devices whose quality information values (for example, RSSI values) of the own cell are equal to or higher than a predetermined threshold and sufficiently larger than the quality information values of other cells. If this is recognized, pilot signal Pilot # 3 is assigned by itself.

  On the other hand, as shown in FIG. 5, each of the transmission side communication devices 31 to 37, for example, when the quality information value of its own cell is not much different from the quality information value of another cell, When the quality information value is equal to or less than a predetermined threshold value, pilot signal Pilot # 3 is not allocated by itself. Note that an example of the MIMO reception method of the reception-side communication apparatus 51 is the same as that in the first embodiment.

  As described above, according to the second embodiment, in each of the plurality of transmission side communication devices, the pilot signal is autonomously transmitted based on the wireless channel quality information between the transmission side communication device and the reception side communication device. Dynamically assigned to determine communication method and MCS level. As a result, in a system that repeatedly uses one frequency, interference from other cells / sectors is reduced probabilistically, and central control by the host device of the transmission side communication device is not required, and overhead due to pilot signals is suppressed as much as possible. As described above, the number of SM MIMO streams can be dynamically switched between cells and sectors.

Embodiment 3 FIG.
In the present third embodiment, in the previous second embodiment, the transmitting side communication device 31 and 32 transmit the pilot signals that are additionally allocated autonomously, and the position of the zone divided in the time direction is defined as the transmitting side communication device 31. , 32 will be described. For example, there is a method of dividing into either the front justification or the back justification.

  FIG. 10 is an explanatory diagram relating to zoning at the time of pilot signal transmission according to Embodiment 3 of the present invention, and exemplifies a case where it is applied to an IEEE 802.16e DL frame. In FIG. 10, the pilot number additional transmission zone transmitted by the transmission side communication device 31 is arranged in the back direction in the time direction, and the pilot number additional transmission zone transmitted by the transmission side communication device 32 is arranged in the front direction in the time direction. Has been placed.

  As described above, according to the third embodiment, the arrangement of zone positions divided in the time direction of pilot signals that are additionally dynamically allocated is determined in advance so as not to interfere with a plurality of transmission side communication apparatuses. Thus, in addition to the effects shown in the second embodiment, it is possible to further reduce the probability of interference of pilot signals from other cell sectors.

Claims (6)

In a MIMO communication system in which communication is performed between a plurality of transmission-side communication devices and one or more reception-side communication devices located in a place where transmission target areas of the plurality of transmission-side communication devices overlap.
The plurality of transmission side communication devices can communicate with each other by dynamically assigning usable pilot signals based on radio channel quality information using pilot signals reported from the one or more reception side communication devices. And the transmitting side communication device to which two or more pilot signals are assigned performs MIMO communication,
The one or more reception side communication devices change a communication method based on the wireless channel quality information using a pilot signal, and separate a combined signal from the plurality of transmission side communication side devices by MIMO reception processing; A MIMO communication system characterized by discarding interference signals from other cell sectors. The MIMO communication system according to claim 1, wherein
Based on the wireless channel quality information reported from the plurality of transmission side communication devices, the pilot signals that can be used in each transmission side communication device are centrally managed, and the pilot signals used by each transmission side communication device are dynamically managed. A MIMO communication system, further comprising a higher-level device to be allocated. The MIMO communication system according to claim 2,
When the higher-level apparatus dynamically allocates a pilot signal, based on the radio channel quality information reported from the plurality of transmission-side communication apparatuses, the higher-order apparatus has a predetermined threshold value or more among the plurality of transmission-side communication apparatuses. A MIMO communication system, characterized in that MIMO communication is performed by increasing the number of pilot signals allocated to a transmission-side communication apparatus that accommodates a large number of reception-side communication apparatuses having the above communication quality. The MIMO communication system according to claim 1, wherein
Each of the plurality of transmission side communication apparatuses uses the wireless channel quality information corresponding to all pilot signals reported from the one or more reception side communication apparatuses, A MIMO communication system, wherein assignment is determined autonomously. The MIMO communication system according to claim 4,
Each of the plurality of transmission side communication devices, when dynamically assigning pilot signals, based on the radio channel quality information corresponding to all pilot signals reported from the one or more reception side communication devices, When accommodating a large number of receiving side communication devices whose communication quality for the own cell is equal to or higher than a predetermined threshold and whose communication quality for the own cell is greater than a predetermined tolerance compared to the communication quality for other cells, autonomously A MIMO communication system characterized by increasing the number of allocated pilot signals and performing MIMO communication. The MIMO communication system according to claim 4 or 5,
When each of the plurality of transmission side communication devices autonomously increases the number of allocated pilot signals, each of the transmission side communication devices is set so that the zone positions in the time direction do not overlap with other transmission side communication devices. And a pilot number additional transmission zone allocated in advance.

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