JP2006173806A - Transmission method and wireless device utilizing it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enhance the detection probability of a burst signal for a wireless device corresponding to the other communication system. <P>SOLUTION: A wireless section 20 transmits a preamble corresponding to one of a plurality of antennas 12, and a burst signal arranged with data corresponding, respectively, to at least two of the plurality of antennas 12 in predetermined timing. The wireless section 20 also transmits a beacon periodically by switching one of the plurality of antennas 12. Upon receiving the burst signal from a wireless device, an acquiring section 32 acquires information about the source antenna 12 of a beacon received by the wireless device. A selecting section 34 selects an antenna 12 which should transmit a preamble out of the plurality of antennas 12. At the time of transmitting the burst signal, the wireless section 20 transmits the preamble from the antenna 12 selected at the selecting section 34. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a transmission technique, and more particularly to a transmission method for transmitting a burst signal using a plurality of antennas and a radio apparatus using the transmission method.

One technique for effectively using frequency resources in wireless communication is an adaptive array antenna technique. The adaptive array antenna technology controls the directivity pattern of an antenna by controlling the amplitude and phase of a signal to be processed for each of a plurality of antennas. There is a MIMO (Multiple Input Multiple Output) system as a technique for increasing the data rate by using such adaptive array antenna technology. In the MIMO system, the transmission device and the reception device each include a plurality of antennas, and channels corresponding to the respective antennas are set. That is, the data rate is improved by setting channels up to the maximum number of antennas for communication between the transmission device and the reception device. Furthermore, if an OFDM (Orthogonal Frequency Division Multiplexing) modulation scheme is combined with such a MIMO system, the data rate is further increased (see, for example, Patent Document 1).
JP 2004-180313 A

  A system that is not a MIMO system and uses an OFDM modulation scheme (hereinafter referred to as “normal system”) includes IEEE802.11a, g, which is a standard for a wireless LAN (Local Area Network). Further, IEEE802.11n is a MIMO system that uses the OFDM modulation scheme (hereinafter simply referred to as “MIMO system”). When the normal system and the MIMO system coexist in the same frequency band, if the receiving radio device corresponding to one of the normal system and the MIMO system can detect the burst signal of the other system, the radio device does not transmit the burst signal. Therefore, collision of burst signals in the radio section can be avoided. That is, it is desirable that the transmitting-side radio apparatus can cause the receiving-side radio apparatus to detect burst signals in different systems in order to reduce the collision probability of burst signals.

  In order to detect a burst signal, it is effective to define a common preamble signal in both systems and to arrange such a preamble signal at the head portion of the burst signal. Here, in order for the radio apparatus on the reception side in the normal system to receive the preamble signal, the preamble signal should correspond to the normal system and correspond to transmission from one antenna. Therefore, a radio device on the transmission side in the MIMO system selects any one of a plurality of antennas and transmits a preamble signal from the selected antenna. At that time, depending on the selected antenna, the transmitted preamble signal may not be detected by the receiving-side radio apparatus in the normal system. For example, this is the case where there is a shield between them. In such a case, the collision probability of the burst signal increases, and the throughput may be deteriorated.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a transmission method for improving the detection probability of a burst signal and a wireless device using the same for a wireless device compatible with another communication system. There is to do.

  In order to solve the above problems, a radio apparatus according to an aspect of the present invention includes a first control signal corresponding to one of a plurality of antennas and a data signal corresponding to at least two of the plurality of antennas. Transmitting the received burst signal at a predetermined timing and switching while selecting one of the plurality of antennas, and a transmission unit that periodically transmits the second control signal, and the first of the burst signals Acquired by the acquisition unit and the acquisition unit for acquiring information related to the transmission source antenna of the second control signal received by the wireless device from the wireless device that is targeted for processing the control signal and not the data signal. And a selection unit that selects an antenna to which the first control signal is to be transmitted among a plurality of antennas based on information on the received antenna.The transmission unit transmits the first control signal from the antenna selected by the selection unit when transmitting the burst signal.

  According to this aspect, when the second control signal transmitted from any one of the plurality of antennas is received by the wireless device in the same manner as the first control signal, it is based on the information regarding the transmission source antenna at that time. Thus, since the antenna to which the first control signal is to be transmitted is determined, it is possible to determine an antenna that improves the detection probability of the burst signal while reflecting the reception result of the second control signal.

  When transmitting the second control signal, the transmission unit includes the identification code of the antenna to which the second control signal is to be transmitted in the second control signal, and the acquisition unit receives information about the antenna from the wireless device. The identification code of the antenna included in the signal may be acquired. In this case, since the identification code of the antenna is used as the information regarding the antenna, it is possible to improve the specific accuracy of the antenna that has transmitted the second control signal.

  You may further provide the receiving part which receives the signal from a radio | wireless apparatus with several antennas, and the measurement part which measures the quality of the signal received in each of several antennas. The acquisition unit may select one antenna based on each of the measured qualities, and use the identification code of the selected one antenna as information related to the antenna. In this case, since the processing can be completed inside the wireless device that should transmit the first control signal, it is not necessary to add a new function of the wireless device that transmits the signal.

  The selection unit may total the information on the antenna acquired by the acquisition unit in units of each identification code of the antenna, and may select the antenna to which the first control signal should be transmitted based on the total result. . In this case, since the antenna is selected based on the total result, the influence of the error can be reduced, and the selection accuracy can be improved.

  A storage unit that stores an identification code of the wireless device to be prioritized may be further included. The acquisition unit also acquires the identification code of the wireless device included in the signal from the wireless device, and the selection unit acquires the identification code of the wireless device stored in the storage unit by the identification code of the wireless device acquired by the acquisition unit. May be selected, the antenna to which the first control signal should be transmitted may be selected while giving priority to the information related to the antenna corresponding to the signal. In this case, since it is possible to select an antenna that gives priority to a wireless device stored in advance, it is possible to provide a service that gives priority to the wireless device. The selection unit may update the selected antenna at a predetermined timing. In this case, the antenna can be selected so as to follow even when the wireless transmission path varies.

  Another aspect of the present invention is a transmission method. In this method, a first control signal corresponding to one of a plurality of antennas and a burst signal in which data signals respectively corresponding to at least two of the plurality of antennas are arranged are transmitted at a predetermined timing, and a plurality of signals are transmitted. A transmission method for periodically transmitting a second control signal by switching while selecting one of the antennas, and processing the first control signal of the burst signal and processing the data signal An antenna to which the first control signal of the plurality of antennas should be transmitted from the information after acquiring information about the transmission source antenna of the second control signal received by the wireless device from a non-target wireless device And the first control signal is transmitted.

  Yet another aspect of the present invention is also a transmission method. In this method, a first control signal corresponding to one of a plurality of antennas and a burst signal in which data signals respectively corresponding to at least two of the plurality of antennas are arranged are transmitted at a predetermined timing, and a plurality of signals are transmitted. By switching while selecting one of the antennas, the step of periodically transmitting the second control signal, the first control signal of the burst signal as a processing target, and the data signal as a processing target A step of acquiring information related to the transmission source antenna of the second control signal received by the wireless device from the wireless device, and a first control among the plurality of antennas based on the acquired information related to the antenna. Selecting an antenna to transmit a signal. The transmitting step transmits the first control signal from the selected antenna when transmitting the burst signal.

  In the transmitting step, when transmitting the second control signal, the identification code of the antenna to which the second control signal is to be transmitted is included in the second control signal, and the acquiring step is performed as wireless information about the antenna. An antenna identification code included in the signal from the apparatus may be acquired. You may further comprise the step which receives the signal from a radio | wireless apparatus with several antennas, and the step which measures the quality of the signal received in each of several antennas. In the obtaining step, one antenna may be selected based on each of the measured qualities, and the identification code of the selected one antenna may be information on the antenna.

  In the selecting step, information on the acquired antennas may be totaled for each of the identification codes of the antennas, and the antenna to which the first control signal should be transmitted may be selected based on the totaling result. The acquiring step also acquires the identification code of the wireless device included in the signal from the wireless device, and the selecting step includes the identification code of the wireless device that should be prioritized and stored in advance. May be selected, the antenna to which the first control signal should be transmitted may be selected while giving priority to the information related to the antenna corresponding to the signal. The selecting step may update the selected antenna at a predetermined timing.

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

  According to the present invention, the detection probability of a burst signal can be improved with respect to a radio apparatus compatible with another communication system.

Example 1
Before describing the present invention in detail, an outline will be described. Embodiment 1 of the present invention relates to a radio apparatus compatible with a MIMO system (hereinafter referred to as “MIMO radio apparatus”). Here, not the MIMO system but also a system using the OFDM modulation method (hereinafter referred to as “normal system”) coexists in the same frequency band as the MIMO system. Here, each preamble signal in the MIMO system and the normal system has a common preamble arranged at the head portion. Therefore, the burst signal transmitted from the MIMO radio apparatus is detected by a radio apparatus (hereinafter referred to as “normal radio apparatus”) corresponding to the normal system. The MIMO radio apparatus includes a plurality of antennas and transmits a preamble from one of the plurality of antennas, but does not transmit from the remaining antennas. Therefore, depending on one selected from the plurality of antennas, the preamble may not be detected by the normal radio apparatus. As a result, the normal radio apparatus may not recognize the presence of the burst signal of the MIMO system and may transmit the burst signal of the normal system.

  In addition, each base station apparatus of the MIMO system and the normal system periodically transmits a beacon at a predetermined interval. Each terminal device of the MIMO system and the normal system recognizes the presence of the base station device by receiving a beacon. Such a beacon has a common structure in the MIMO system and the normal system. In addition, base station apparatuses and terminal apparatuses in the MIMO system are collectively referred to as MIMO radio apparatuses, and base station apparatuses and terminal apparatuses in the normal system are collectively referred to as normal radio apparatuses. Since the MIMO wireless apparatus includes a plurality of antennas, a beacon is transmitted from one of them.

  The MIMO wireless apparatus according to the present embodiment transmits a beacon while switching one of a plurality of antennas. For example, a predetermined beacon is transmitted from the “first antenna”, and the next beacon is transmitted from the “second antenna”. At this time, an identification code assigned to each of the plurality of antennas (hereinafter referred to as “antenna identification code”) and corresponding to the antenna transmitting the beacon is included in the beacon and transmitted. Normally, when a wireless device receives a beacon, it extracts an antenna identification code from the received beacon. Further, the normal wireless device includes the extracted antenna identification code when transmitting the burst signal. The MIMO wireless apparatus that has received the burst signal extracts an antenna identification code.

  By repeating such processing, the MIMO radio apparatus acquires antenna identification codes from a plurality of normal terminal apparatuses. Here, the large number of acquired antenna identification codes corresponds to an antenna in which a beacon is easily transmitted to a normal wireless device. Like the beacon, the preamble is also transmitted from one of the plurality of antennas, so the MIMO radio apparatus transmits the preamble from the antenna corresponding to the large number of acquired antenna identification codes. Here, the normal system is a wireless LAN compliant with the IEEE 802.11a standard, and the MIMO system is a wireless LAN that should be compliant with the IEEE 802.11a standard.

  FIG. 1 shows a configuration of a communication system 100 according to Embodiment 1 of the present invention. Here, it is assumed that the communication system 100 includes the above-described MIMO system and normal system. The communication system 100 includes a first MIMO radio apparatus 10a, a second MIMO radio apparatus 10b, and a normal radio apparatus 16 that are collectively referred to as the MIMO radio apparatus 10. The first MIMO radio apparatus 10a includes a first antenna 12a, a second antenna 12b, a third antenna 12c, and a fourth antenna 12d, which are collectively referred to as an antenna 12, and the second MIMO radio apparatus 10b is collectively referred to as an antenna 14. A first antenna 14a, a second antenna 14b, a third antenna 14c, and a fourth antenna 14d are included. The first MIMO radio apparatus 10a corresponds to a base station apparatus in the MIMO system, the second MIMO radio apparatus 10b corresponds to a terminal apparatus in the MIMO system, and the normal radio apparatus 16 corresponds to a terminal apparatus in the normal system. The first MIMO radio apparatus 10a may also serve as a base station apparatus in the normal system.

  Before describing the configuration of the communication system 100, an outline of a MIMO system will be described. It is assumed that data is transmitted from the first MIMO radio apparatus 10a to the second MIMO radio apparatus 10b. The first MIMO radio apparatus 10a transmits different data from each of the first antenna 12a to the fourth antenna 12d. As a result, the data rate is increased. The second MIMO radio apparatus 10b receives data from the first antenna 14a to the fourth antenna 14d.

  Here, since the number of antennas 12 is “4” and the number of antennas 14 is also “4”, the combination of transmission paths between the antennas 12 and 14 is “16”. A transmission path characteristic between the i-th antenna 12i and the j-th antenna 14j is denoted by hij. In the figure, the transmission path characteristic between the first antenna 12a and the first antenna 14a is h11, the transmission path characteristic between the first antenna 12a and the second antenna 14b is h12, the second antenna 12b and the first antenna. 14a, the transmission path characteristic between the second antenna 12b and the second antenna 14b is h22, and the transmission path characteristic between the fourth antenna 12d and the fourth antenna 14d is h44. Has been. Note that transmission lines other than these are omitted for the sake of clarity.

  The second MIMO radio apparatus 10b operates so as to independently demodulate data transmitted from the first antenna 12a to the fourth antenna 12d by adaptive array signal processing. For the sake of clarity, it is assumed that the first MIMO radio apparatus 10a does not perform adaptive array signal processing when transmitting data, but in order to improve the transmission quality of data, the first MIMO radio apparatus 10a 10a may perform adaptive array signal processing during transmission.

  The first MIMO radio apparatus 10a transmits different data from the first antenna 12a to the fourth antenna 12d. The first MIMO radio apparatus 10a transmits data by including it in a burst signal, but adds a preamble to the head part of the burst signal. Since the preamble is common to the preamble in the normal system, unlike the data, the preamble is transmitted from one of the first antenna 12a to the fourth antenna 12d. The selection of one antenna 12 will be described later. Moreover, the 1st MIMO radio | wireless apparatus 10a transmits a beacon regularly. Similarly to the preamble, the beacon is also common to the beacon in the normal system, and is transmitted from one of the first antenna 12a to the fourth antenna 12d.

  The first MIMO radio apparatus 10a transmits a beacon while switching the first antenna 12a to the fourth antenna 12d one by one in order. That is, the antenna 12 is switched in the order of “first antenna 12a”, “second antenna 12b”, “third antenna 12c”, “fourth antenna 12d”, and “first antenna 12a”. The first MIMO radio apparatus 10a includes in the beacon the identification code of the antenna 12 that should transmit the beacon. Note that beacons are also burst signals, but here, for the sake of clarity, a burst signal including data is referred to as a “burst signal”, and beacons are excluded.

  The second MIMO radio apparatus 10b receives data from the first MIMO radio apparatus 10a while performing adaptive array signal processing from the first antenna 14a to the fourth antenna 14d. Note that the operations of the first MIMO radio apparatus 10a and the second MIMO radio apparatus 10b may be reversed. In this case, the second MIMO radio apparatus 10b does not perform adaptive array processing when transmitting a burst signal, and the first MIMO radio apparatus 10a performs adaptive array processing when receiving a burst signal.

  The normal radio apparatus 16 communicates with the first MIMO radio apparatus 10a or another base station apparatus (not shown). Further, the normal radio device 16 receives the beacon from the first MIMO radio device 10a, and extracts the identification code of the antenna 12 included in the beacon. Furthermore, the normal radio apparatus 16 includes the extracted identification code of the antenna 12 in the burst signal when transmitting the burst signal. As described above, the normal radio apparatus 16 can detect the burst signal corresponding to the MIMO system, but the normal radio apparatus 16 does not transmit the burst signal over the period of detection. Actually, the normal radio apparatus 16 receives the burst signal from the first MIMO radio apparatus 10a and the burst signal from the second MIMO radio apparatus 10b. Here, in order to clarify the explanation, the case of receiving a burst signal from the first MIMO radio apparatus 10a will be explained.

  FIG. 2 shows a configuration of a signal transmitted in the communication system 100. In FIG. 2, the horizontal axis indicates time. In addition, “B1”, “B2”, “B3”, “B4”, “B5”, “B6” indicate beacons, and the numbers given to these are used for convenience to distinguish the beacons. Has been. As described above, the beacon is transmitted by the first MIMO radio apparatus 10a. Also, “B1” is transmitted from the first antenna 12a, “B2” is transmitted from the second antenna 12b, “B3” is transmitted from the third antenna 12c, “B4” is transmitted from the fourth antenna 12d, “B5” is transmitted from the first antenna 12a, and “B6” is transmitted from the second antenna 12b. That is, the first MIMO radio apparatus 10a is switched while selecting the antenna 12. A continuous beacon, for example, an interval between “B1” and “B2” is called a “beacon interval”. Burst signals are transmitted in the beacon interval. Here, the burst signal is transmitted from the first MIMO radio apparatus 10a, the second MIMO radio apparatus 10b, and the normal radio apparatus 16.

  FIGS. 3A and 3B show the configuration of the burst format in the communication system 100. FIG. FIG. 3 (a) shows a burst format defined in a normal system. This is a burst format used in a speech channel conforming to the IEEE 802.11a standard of a wireless LAN (Local Area Network). As shown in the figure, “Legacy STS (Short Training Sequence)”, “Legacy LTS (Long Training Sequence)”, “Legacy Signal”, and “Data” are arranged from the top. “Legacy STS” is used for timing synchronization and AGC (Automatic Gain Control), etc., “Legacy LTS” is used for channel estimation, “Legacy signal” includes control information, and “Data” is usually Data transmitted in the system.

  The IEEE 802.11a standard applies an OFDM modulation scheme. In the OFDM modulation method, generally, the sum of the size of the Fourier transform and the number of symbols in the guard interval is defined as one unit. In the present embodiment, this single unit is called an “OFDM symbol”. In the IEEE 802.11 standard, the size of the Fourier transform is 64 (hereinafter, one FFT (Fast Fourier Transform) point is referred to as an “FFT point”), and the number of FFT points in the guard interval is 16, so the OFDM symbol Corresponds to 80 FFT points.

  FIG. 3B shows a burst format defined in the MIMO system. Although the figure is divided into four stages, it corresponds to signals transmitted from the first antenna 12a, the second antenna 12b, the third antenna 12c, and the fourth antenna 12d from the upper stage to the lower stage. In the burst format shown in FIG. 3B, “Legacy STS”, “Legacy LTS”, and “Legacy signal” are arranged from the top in the same manner as the burst format shown in FIG. Following these, a “MIMO signal” is arranged. The above signals are transmitted from the first antenna 12a. These may be transmitted from the antennas 12 other than the first antenna 12a, and may be transmitted from one antenna 12. The “MIMO signal” and subsequent signals are signals specific to the MIMO system, and the “MIMO signal” includes control information corresponding to the MIMO system.

  “First MIMO-STS” to “fourth MIMO-STS” are used for timing synchronization and AGC, etc., “first MIMO-LTS” to “fourth MIMO-LTS” are used for channel estimation, and “first data To “fourth data” is data to be transmitted in the MIMO system. Here, “first MIMO-STS” to “fourth MIMO-STS” are configured by patterns that reduce mutual interference. The same applies to “first MIMO-LTS” to “fourth MIMO-LTS”. Here, description of these configurations is omitted.

  “Legacy STS”, “Legacy LTS”, and “Legacy signal” in FIGS. 3A and 3B correspond to the “preamble” described above. In particular, in FIG. 3B, signals transmitted from one antenna 12 are collectively referred to as “preamble”, and signals transmitted from a plurality of antennas 12 are collectively referred to as “data”. The “MIMO signal” is transmitted from the same antenna 12 or antenna 14 as the “preamble”. Such a preamble is a signal that is compatible with a normal system except for the “MIMO signal”. That is, the preamble of the burst signal is a processing target of the normal wireless device 16, and the data is not a processing target of the normal wireless device 16.

  FIG. 4 shows the configuration of the first MIMO radio apparatus 10a. The first MIMO radio apparatus 10a includes a first radio unit 20a, a second radio unit 20b, a fourth radio unit 20d, which are collectively referred to as a radio unit 20, and a first processing unit 22a and a second processing unit 22b, which are collectively referred to as a processing unit 22. , A fourth processing unit 22d, a first modulation / demodulation unit 24a, a second modulation / demodulation unit 24b, a fourth modulation / demodulation unit 24d, an IF unit 26, a control unit 30, an acquisition unit 32, and a selection unit 34. Further, as signals, a first time domain signal 200a, a second time domain signal 200b, a fourth time domain signal 200d, which are collectively referred to as a time domain signal 200, a first frequency domain signal 202a, which is collectively referred to as a frequency domain signal 202, and a second time domain signal 200b. A frequency domain signal 202b and a fourth frequency domain signal 202d are included.

  As a reception operation, the radio unit 20 performs frequency conversion on a radio frequency signal received by the antenna 12 to derive a baseband signal. The radio unit 20 outputs the baseband signal as the time domain signal 200 to the processing unit 22. In general, baseband signals are formed by in-phase and quadrature components, so they should be transmitted by two signal lines. Here, for clarity of illustration, only one signal line is used. Shall be shown. An AGC and A / D converter are also included. As a transmission operation, the radio unit 20 performs frequency conversion on the baseband signal from the processing unit 22 and derives a radio frequency signal. Here, a baseband signal from the processing unit 22 is also shown as a time domain signal 200. The radio unit 20 outputs a radio frequency signal to the antenna 12. Further, a PA (Power Amplifier) and a D / A converter are also included. The time domain signal 200 is a multicarrier signal converted into the time domain, and is a digital signal. Further, the signal processed in the radio unit 20 forms a burst signal, and the burst format is as shown in FIG. Further, a beacon is transmitted at a predetermined interval as shown in FIG. In that case, it is transmitted from one of the radio units 20.

  As a receiving operation, the processing unit 22 converts each of the plurality of time domain signals 200 into the frequency domain, and performs adaptive array signal processing on the frequency domain signal. The processing unit 22 outputs the result of adaptive array signal processing as the frequency domain signal 202. One frequency domain signal 202 corresponds to a signal transmitted from one antenna 14 in FIG. 1, and this corresponds to a signal corresponding to one transmission path. As a transmission operation, the processing unit 22 receives a frequency domain signal 202 as a frequency domain signal from the modem unit 24, converts the frequency domain signal 202 into the time domain, and outputs the time domain signal 200. Here, the frequency domain signal 202 that is a frequency domain signal includes a plurality of subcarrier components. For the sake of clarity, it is assumed that the signals in the frequency domain are arranged in the order of subcarrier numbers to form a serial signal.

  FIG. 5 shows the structure of a signal in the frequency domain. One of a plurality of carriers in the OFDM modulation system is generally called a subcarrier, but here, one subcarrier is designated by a “subcarrier number”. Here, as in the IEEE802.11a standard, 53 subcarriers from subcarrier numbers “−26” to “26” are defined. The subcarrier number “0” is set to null in order to reduce the influence of the DC component in the baseband signal. Each subcarrier is modulated by a variably set modulation scheme. As a modulation method, any one of BPSK (Binary Phase Shift Keying), QSPK (Quadrature Phase Shift Keying), 16QAM (Quadrature Amplitude Modulation), and 64QAM is used.

  Here, one combination of subcarrier numbers “−26” to “26” corresponds to the “OFDM symbol” described above. In the “i” th OFDM symbol, subcarrier components are arranged in the order of subcarrier numbers “1” to “26” and subcarrier numbers “−26” to “−1”. Also, the “i−1” th OMDM symbol is arranged before the “i” th OFDM symbol, and the “i + 1” th OMDM symbol is arranged after the “i” th OFDM symbol. And

  Returning to FIG. The modem unit 24 performs demodulation and decoding on the frequency domain signal 202 from the processing unit 22 as reception processing. Note that demodulation and decoding are performed in units of subcarriers. The modem unit 24 outputs the decoded signal to the IF unit 26. Further, the modem unit 24 performs encoding and modulation as transmission processing. The modem unit 24 outputs the modulated signal to the processing unit 22 as the frequency domain signal 202. It is assumed that the modulation scheme and coding rate are specified by the control unit 30 during the transmission process.

  The IF unit 26 combines signals from the plurality of modulation / demodulation units 24 as a reception process to form one data stream. The IF unit 26 outputs a data stream. In addition, the IF unit 26 inputs one data stream as transmission processing and separates it. Further, the separated data is output to a plurality of modems 24.

  With the configuration as described above, the IF unit 26, the modem unit 24, the processing unit 22, and the radio unit 20 correspond to a preamble corresponding to one of the plurality of antennas 12 and at least two of the plurality of antennas 12, respectively. A burst signal in which data is arranged is transmitted at a predetermined timing. Here, it is assumed that the radio unit 20, the processing unit 22, and the modem unit 24 corresponding to the antenna 12 that does not transmit a preamble or data do not execute a process for transmission. The IF unit 26, the modem unit 24, the processing unit 22, and the radio unit 20 periodically transmit beacons by switching while selecting any of the plurality of antennas 12. In this case, the IF unit 26, the modem unit 24, the processing unit 22, and the radio unit 20 corresponding to the antenna 12 that should transmit the beacon execute processing for transmission.

  Further, when transmitting the beacon, the control unit 30 includes the identification code of the antenna 12 to which the beacon is transmitted in the beacon. Here, it is assumed that the identification code of the antenna 12 is given in advance to the “first antenna 12a” as “1”. In addition, assuming that there are a plurality of base station apparatuses compatible with the MIMO system in the vicinity, the identification code assigned to the first MIMO radio apparatus 10a may be combined with the identification code of the antenna 12. Since the data structure of the beacon may be the same as the data structure of the beacon in the IEEE 802.11a standard, the description is omitted here. For example, the identification code of the antenna 12 may be inserted into “Reserved” included in “Capability information” in the beacon.

  The acquisition unit 32 relates to the antenna 12 that is the transmission source of the beacon received by the normal radio device 16 when the burst signal is received from the normal radio device 16 via the radio unit 20, the processing unit 22, and the modem unit 24. Get information. Here, the information regarding the antenna 12 corresponds to the identification code of the antenna 12 included in the burst signal from the normal radio device 16. For this purpose, the normal wireless device 16 receives a beacon, extracts the identification code of the antenna 12 included in the received beacon, and includes the identification code of the antenna 12 therein when transmitting a burst signal. To do. Note that the burst signal transmitted from the normal wireless device 16 corresponds to FIG. Further, the transmission destination of the burst signal may not be the first MIMO radio apparatus 10a, but may be a base station apparatus corresponding to a normal system (not shown). At that time, the first MIMO radio apparatus 10a receives a burst signal to other radio apparatuses and extracts the identification code of the antenna 12 from the burst signal.

  The selection unit 34 inputs the identification code of the antenna 12 acquired by the acquisition unit 32, and selects the antenna 12 that should transmit the preamble from the plurality of antennas 12 based on the identification code. At this time, the selection unit 34 aggregates the identification codes of the antenna 12 in units of the identification codes of the antennas 12, and selects the antenna 12 to which the preamble is to be transmitted based on the aggregation results. Here, the number acquired by the acquisition unit 32 is counted up for each of the identification codes “1”, “2”, “3”, and “4” of the antenna 12. Furthermore, the antenna 12 having the maximum counted up result is selected. The identification code of the antenna 12 acquired by the acquisition unit 32 corresponds to the identification code of the antenna 12 that is transmitted in advance by being included in the beacon. It corresponds to the antenna 12 that has transmitted the received beacon.

  That is, it can be said that the antenna 12 is likely to be normally detected by the wireless device 16 when transmitting the preamble from one of the plurality of antennas 12. Here, in order to improve the processing accuracy, the selection unit 34 performs selection of the antenna 12 when the counted up result becomes larger than a predetermined value. Further, the selection unit 34 updates the selected antenna 12 at a predetermined timing even after the antenna 12 is selected. As a result, at the timing, the antenna 12 that should transmit the preamble is changed. Further, the IF unit 26, the modem unit 24, the processing unit 22, and the radio unit 20 transmit a preamble from the antenna 12 selected by the selection unit 34 when transmitting a burst signal.

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

  FIG. 6 shows a configuration of the first processing unit 22a. The first processing unit 22a includes an FFT (Fast Fourier Transform) unit 40, a synthesis unit 42, a reference signal generation unit 44, a received weight vector calculation unit 54, an IFFT unit 48, and a preamble addition unit 50. The combining unit 42 includes a first multiplying unit 56 a, a second multiplying unit 56 b, a fourth multiplying unit 56 d, and an adding unit 60 that are collectively referred to as the multiplying unit 56.

  The FFT unit 40 receives a plurality of time domain signals 200 and performs a Fourier transform on each of them to derive a frequency domain signal. As described above, in a single frequency domain signal, signals corresponding to subcarriers are serially arranged in the order of subcarrier numbers.

  Multiplier 56 weights the frequency domain signal with the received weight vector from received weight vector calculator 54, and adder 60 adds the output of multiplier 56. Here, since the signals in the frequency domain are arranged in the order of the subcarrier numbers, the reception weight vectors from the reception weight vector calculation unit 54 are also arranged so as to correspond thereto. That is, one multiplication unit 56 sequentially receives reception weight vectors arranged in the order of subcarrier numbers. Therefore, the addition unit 60 adds the multiplication results in units of subcarriers. As a result, the added signals are also serially arranged in the order of subcarrier numbers as shown in FIG. The added signal is the frequency domain signal 202 described above.

  In the following description, when the signal to be processed is defined in the frequency domain, the processing is basically executed in units of subcarriers. Here, in order to simplify the description, the processing in one subcarrier will be described. Therefore, processing for a plurality of subcarriers can be handled by executing processing on one subcarrier in parallel or serially.

  The reference signal generation unit 44 stores the “Legacy STS”, “Legacy LTS”, “Legacy STS”, “Ligacy STS”, “Legacy STS”, “Ligacy STS”, “Legacy STS”, “Legacy STS”, “Last STY”, “STS” and “first MIMO-LTS” are output as reference signals. In addition to these periods, the frequency domain signal 202 is determined based on a predetermined threshold value, and the result is output as a reference signal. The determination may be a soft determination instead of a hard determination.

  The reception weight vector calculation unit 54 derives a reception weight vector based on the frequency domain signal from the FFT unit 40, the frequency domain signal 202, and the reference signal. The method for deriving the reception weight vector may be any method, one of which is the derivation by the LMS (Least Mean Square) algorithm. Further, the reception weight vector may be derived by correlation processing. In this case, the frequency domain signal and the reference signal are input not only from the first processing unit 22a but also from the second processing unit 22b and the like through a signal line (not shown). The frequency domain signal in the first processing unit 22a is denoted by x1 (t), the frequency domain signal in the second processing unit 22b is denoted by x2 (t), the reference signal in the first processing unit 22a is denoted by S1 (t), the second If the reference signal in the processing unit 22b is represented as S2 (t), x1 (t) and x2 (t) are represented by the following equations.

ここで、雑音は無視する。第１の相関行列Ｒ１は、Ｅをアンサンブル平均として、次の式のように示される。

参照信号間の第２の相関行列Ｒ２は、次の式のように計算される。

Here, noise is ignored. The first correlation matrix R1 is expressed as the following equation, where E is an ensemble average.

The second correlation matrix R2 between the reference signals is calculated as follows:

最終的に、第２の相関行列Ｒ２の逆行列と第１の相関行列Ｒ１を乗算することによって、受信応答ベクトルが導出される。

さらに、受信ウエイトベクトル計算部５４は、受信応答ベクトルから受信ウエイトベクトルを計算する。

Finally, the reception response vector is derived by multiplying the inverse matrix of the second correlation matrix R2 by the first correlation matrix R1.

Further, the reception weight vector calculation unit 54 calculates a reception weight vector from the reception response vector.

  The IFFT unit 48 performs inverse Fourier transform on the first frequency domain signal 202a to convert it into a time domain signal. As shown in FIG. 3B, the preamble adding unit 50 adds a preamble to the head portion of the burst signal. Here, in addition to “Legacy STS” and “Legacy LTS”, “first MIMO-STS” and “first MIMO-LTS” are also added. The preamble adding unit 50 outputs the signal with the preamble added as the first time domain signal 200a. Note that the above operation is controlled by the control unit 30 in FIG. In particular, if the antenna 12 to which the preamble is to be transmitted is not the first antenna 12a, the preamble adding unit 50 adds “first MIMO-STS” and “first MIMO-LTS” without adding the preamble. In FIG. 6, the first time domain signal 200a and the like are shown in two places. These are signals in one direction, and these correspond to the first time domain signal 200a and the like which are bidirectional signals in FIG.

  FIG. 7 shows the configuration of the selection unit 34. The selection unit 34 includes a separation unit 80, a totaling unit 82, and a determination unit 84. The separation unit 80 inputs the identification code of the antenna 12 acquired by the acquisition unit 32. Here, since the identification codes of the antenna 12 are the four types “1” to “4” as described above, the separation unit 80 classifies the identification codes of the antenna 12 into any of the four types. The separation unit 80 outputs the classified result to the totaling unit 82.

  The totaling unit 82 inputs the classified result, and counts up one of four types of identification codes of the antenna 12 based on the result. For example, if the input classification result is “1”, the identification code “1” of the antenna 12 is counted up. Counting up may be performed so as to derive an accumulated value from a predetermined timing, or counting may be performed while shifting the starting timing of integration, such as a moving average. According to the former, the counted value tends to increase, and the accuracy can be improved by suppressing noise or the like. On the other hand, according to the latter, since the influence at the timing close to the present is taken into account, the accuracy can be improved by following the fluctuation of the transmission path. FIG. 8 shows the structure of data aggregated by the aggregation unit 82. As shown in the figure, the cumulative value of the count-up using the antenna 12 as a unit is recorded.

  Returning to FIG. The determination unit 84 selects the antenna 12 having the maximum value from the cumulative value of the count-up using the antenna 12 as a unit. For example, in the case of FIG. 8, the first antenna 12a is selected. The determination unit 84 outputs the identification code of the selected antenna 12. The output identification code of the antenna 12 corresponds to the antenna 12 used for transmitting the preamble of the burst signal in the control unit 30 (not shown). As described above, the antenna 12 that is the maximum value among the cumulative values of the count-up using the antenna 12 as a unit corresponds to the antenna 12 that has transmitted the beacon that is received most frequently by the normal wireless device 16. The preamble and the beacon are common in that one antenna 12 among the plurality of antennas 12 is used. The aggregation result in the beacon is used for transmitting the preamble. Note that the determination unit 84 determines the antenna 12 when the accumulated value is larger than a predetermined value. For example, in the case of FIG. 8, when the cumulative value exceeds “30”, the determination unit 84 determines the cumulative value. Furthermore, the determination unit 84 executes the determination at a predetermined timing or reflects the latest accumulated value.

  The operation of the communication system 100 configured as above will be described. FIG. 9 is a sequence diagram illustrating a signal transmission procedure in the communication system 100. Here, signal transmission between the first MIMO radio apparatus 10a and the normal radio apparatus 16 is shown. Actually, there are signals between the first MIMO radio apparatus 10a and the second MIMO radio apparatus 10b in addition to these, but the description thereof is omitted here for the sake of clarity. In addition, the target to which the first MIMO radio apparatus 10a illustrated in the figure should transmit the burst signal is not the normal radio apparatus 16, and the target to which the normal radio apparatus 16 should transmit the burst signal may not be the first MIMO radio apparatus 10a. . The first MIMO radio apparatus 10a transmits a beacon from the first antenna 12a (S10). The normal radio device 16 successfully receives the beacon (S12), and extracts the identification code of the antenna 12 included in the received beacon (S14).

  The first MIMO radio apparatus 10a transmits a beacon from the second antenna 12b (S16), but the normal radio apparatus 16 fails to receive the beacon (S18). The first MIMO radio apparatus 10a transmits a beacon from the third antenna 12c (S20), but the normal radio apparatus 16 fails to receive the beacon (S22). The first MIMO radio apparatus 10a transmits a beacon from the fourth antenna 12d (S24), but the normal radio apparatus 16 fails to receive the beacon (S26). Usually, the wireless device 16 generates a burst signal in order to transmit predetermined data (S28). The burst signal generated here conforms to the burst format shown in FIG. 3A, but includes the identification code of the antenna 12 at a predetermined position. Further, a burst signal may be generated in order to transmit the identification code of the antenna 12 to the first MIMO radio apparatus 10a. The first MIMO radio apparatus 10a transmits a burst signal (S30).

  The first MIMO radio apparatus 10a receives the burst signal (S32), and extracts the identification code of the antenna 12 included in the received burst signal (S34). The first MIMO radio apparatus 10a determines the antenna 12 that should transmit the preamble based on the identification code of the antenna 12 (S36). The first MIMO radio apparatus 10a generates a burst signal (S38) and transmits the burst signal (S40). At this time, a preamble of a burst signal is transmitted from the determined antenna 12. The normal radio device 16 detects the preamble of the burst signal (S42). Normally, the wireless device 16 prohibits transmission of its own burst signal (S44).

  FIG. 10 is a flowchart showing a signal transmission procedure in the first MIMO radio apparatus 10a. The control unit 30 switches while selecting the antenna 12 that should transmit the beacon (S50). The modem unit 24, the processing unit 22, and the radio unit 20 transmit a beacon including the identification code of the antenna 12 from the selected antenna 12 (S52). When the radio unit 20, the processing unit 22, and the modem unit 24 receive the burst signal (Y in S54), the acquisition unit 32 extracts the identification code of the antenna 12 from the burst signal (S56). The selection unit 34 aggregates the identification codes of the antennas 12 (S58), and when the number of data exceeds a predetermined value (Y of S60), determines the antenna 12 to which the preamble is to be transmitted (S62). On the other hand, if the radio unit 20, the processing unit 22, and the modem unit 24 do not receive a burst signal (N in S54), or the number of data tabulated in the selection unit 34 is not equal to or greater than a predetermined value (N in S60), the beacon interval is set. If it has not elapsed (N in S64), the process returns to step 54. On the other hand, if the beacon interval has elapsed (Y in S64), the process returns to step 50.

  According to the embodiment of the present invention, the beacon transmitted from any of the plurality of antennas is transmitted based on the information related to the antenna of the MIMO wireless device when the beacon transmitted from any of the plurality of antennas is received by the normal wireless device. Since the power antenna is determined, it is possible to determine the antenna that improves the detection probability of the burst signal in the normal radio apparatus while reflecting the result of the beacon. Further, when transmitting a beacon, it is possible to grasp how a signal transmitted from each of the plurality of antennas is normally received by the wireless device by switching while selecting any of the plurality of antennas. Further, when transmitting a beacon, any one of the plurality of antennas is switched, so that the number of hidden normal wireless devices can be reduced. In addition, since the antenna that receives the most beacon is selected, it is possible to select an antenna that facilitates reception of the preamble.

  In addition, since the preamble is easily detected in the normal radio apparatus, transmission of burst signals by the normal radio apparatus can be suppressed. In addition, since the burst signal can be transmitted normally by a radio apparatus, the collision probability of the burst signal can be reduced and the frequency can be used effectively. Moreover, since the identification code of the antenna is included when transmitting the beacon, it is possible to improve the specific accuracy of the antenna that transmitted the beacon. Further, since the antenna is selected based on the total result, the influence of the error is reduced, and the selection accuracy can be improved. Also, if the total number of data is small, the selection is not executed, so that the antenna can be selected accurately. Further, since the antenna selection is updated, the antenna can be selected so as to follow even when the wireless transmission path changes.

(Example 2)
In the second embodiment of the present invention, as in the first embodiment, when a normal system coexists in the same frequency band as the MIMO system, the MIMO for determining the antenna to transmit the preamble among the plurality of antennas is determined. The present invention relates to a wireless device. In the second embodiment, unlike the first embodiment, when transmitting a beacon, a MIMO radio apparatus, particularly a base station apparatus corresponding to the MIMO system does not include an identification code of an antenna that transmits a beacon in the beacon. However, when receiving a burst signal from a normal radio apparatus, the MIMO radio apparatus measures the signal strength in units of a plurality of antennas. Furthermore, the MIMO radio apparatus acquires an antenna identification code for the antenna having the highest signal strength. The MIMO wireless apparatus according to the second embodiment determines the antenna to which the preamble is to be transmitted by performing the same aggregation as that of the first embodiment on the acquired antenna identification code.

  The configuration of the first MIMO radio apparatus 10a according to the second embodiment is the same type as the first MIMO radio apparatus 10a of FIG. The first MIMO radio apparatus 10a according to the second embodiment includes a measurement unit for measuring the strength of a signal received at each of the antennas 12 when a burst signal from the normal radio apparatus 16 (not shown) is received by the antennas 12. . For example, the measurement unit is connected from the first radio unit 20a to the fourth radio unit 20d. The acquisition unit 32 selects one antenna 12 having the maximum signal strength from each of the measured signal strengths, and acquires the identification code of the selected one antenna 12. The acquisition unit 32 outputs the acquired identification code of the antenna 12 to the selection unit 34.

  FIG. 11 is a sequence diagram illustrating a signal transmission procedure in the communication system 100 according to the second embodiment of the present invention. Usually, the wireless device 16 generates a burst signal in order to transmit predetermined data (S80). The burst signal generated here conforms to the burst format shown in FIG. The first MIMO radio apparatus 10a transmits a burst signal (S82). The first MIMO radio apparatus 10a receives the burst signal (S84), and measures the signal strength corresponding to each antenna 12 that has received the burst signal (S86). The first MIMO radio apparatus 10a selects the antenna 12 corresponding to the burst signal with the maximum signal strength, and acquires the identification code of the antenna 12 corresponding to the antenna 12 (S88). The first MIMO radio apparatus 10a determines the antenna 12 that should transmit the preamble based on the identification code of the antenna 12 (S90). The first MIMO radio apparatus 10a generates a burst signal (S92) and transmits the burst signal (S94). At this time, a preamble of a burst signal is transmitted from the determined antenna 12. The normal radio apparatus 16 detects the preamble of the burst signal (S96). Normally, the wireless device 16 prohibits transmission of its own burst signal (S98).

  FIG. 12 is a flowchart showing a signal transmission procedure in the first MIMO radio apparatus 10a. If the radio unit 20, the processing unit 22, and the modem unit 24 do not receive a burst signal (N in S100), the radio unit 20, the processing unit 22, and the modem unit 24 continue to wait until they are received. If the radio unit 20, the processing unit 22, and the modem unit 24 receive a burst signal (Y in S100), the measurement unit measures the intensity of the received burst signal while corresponding to each of the antennas 12 (S102). The acquisition unit 32 acquires the identification code of the antenna 12 corresponding to the antenna 12 having the maximum signal strength (S104). The selection unit 34 aggregates the identification codes of the antennas 12 (S106), and when the number of data exceeds a predetermined value (Y in S108), determines the antenna 12 to which the preamble is to be transmitted (S110). On the other hand, if the number of data tabulated in the selection unit 34 is not greater than or equal to the predetermined value (N in S108), the process returns to step 100.

  According to the embodiment of the present invention, the process of selecting an antenna to transmit a preamble can be completed inside the MIMO radio apparatus, so that it is not necessary to add a new function to the normal radio apparatus. In addition, since the antenna having the highest received burst signal strength is selected from the plurality of antennas that should receive the burst signal from the normal wireless device, an antenna that makes the preamble easily received by the normal wireless device is selected. You can choose. Further, since the selection is performed based on the received burst signal, the antenna selection can be easily updated.

  The present invention has been described based on the embodiments. This embodiment is an exemplification, and it will be understood by those skilled in the art that various modifications can be made to combinations of the respective constituent elements and processing processes, and such modifications are also within the scope of the present invention. is there.

  In the first or second embodiment of the present invention, the selection unit 34 selects the antenna 12 that makes it easy for the normal radio apparatus 16 to detect the preamble signal. For example, the antenna 12 may be selected so that a preamble signal can be easily detected in the normal radio apparatus 16 to be prioritized. At that time, the MIMO radio apparatus 10 is provided with a storage unit that stores the identification code of the normal radio apparatus to be prioritized. The acquisition unit 32 also acquires the identification code of the normal radio device 16 included in the burst signal from the normal radio device 16. If the identification code of the normal radio device 16 acquired by the acquisition unit 32 corresponds to the identification code of the normal radio device 16 stored in the storage unit, the selection unit 34 gives priority to the antenna 12 corresponding to the burst signal. However, the antenna 12 that should transmit the preamble is selected.

  Here, in order to give priority, the antenna 12 corresponding to the burst signal may be selected. Alternatively, the value at the time of counting up the identification code of the antenna 12 may be increased when the selection unit 34 performs the aggregation. For example, if the selection unit 34 inputs the identification code of the antenna 12 “once”, the selection unit 34 counts it up as “10 times”. According to this modification, the antenna 12 selection process that gives priority to the normal wireless device 16 stored in advance can be performed, so that it is possible to provide a service that gives priority to the normal wireless device 16. In addition, by setting the normal wireless device 16 to be prioritized to the normal wireless device 16 having a large communication amount, the collision probability of burst signals can be efficiently reduced, and the frequency utilization efficiency can be improved. That is, it is only necessary that the antenna 12 can be selected such that the preamble is received by the predetermined normal radio apparatus 16.

  In the first or second embodiment of the present invention, the reception weight vector calculation unit 54 uses an LMS algorithm as an adaptive algorithm for estimating a reception weight vector signal. However, the reception weight vector calculation unit 54 may use an adaptive algorithm other than the LMS algorithm. For example, the RLS algorithm. According to this modification, the reception weight vector signal can be drawn faster. That is, it is only necessary to be able to estimate the reception weight vector for executing adaptive array signal processing.

  In the first or second embodiment of the present invention, the communication system 100 transmits a multicarrier signal. However, the present invention is not limited to this. For example, the communication system 100 may transmit a single carrier signal. According to this modification, the present invention can be applied to various communication systems 100. That is, it is sufficient that the MIMO system and the normal system are mixed.

  In Embodiment 2 of the present invention, the measurement unit measures the strength of the received burst signal, and the selection unit 34 selects the antenna 12 that maximizes the signal strength. However, the present invention is not limited to this. For example, quality other than signal strength may be used as the quality of the received burst signal. One example is a delay spread in a wireless transmission path. The measurement unit may measure each delay spread in units of the antenna 12, and the selection unit 34 may select the antenna 12 that minimizes the delay spread. Further, the antenna 12 may be selected by combining the signal strength and the delay spread. According to this modification, the antenna 12 can be selected while considering the signal quality in detail. That is, it is only necessary to select the antenna 12 that should transmit a preamble that is likely to be detected by the normal radio apparatus 16.

It is a figure which shows the structure of the communication system which concerns on Example 1 of this invention. It is a figure which shows the structure of the signal transmitted in the communication system of FIG. FIGS. 3A and 3B are diagrams showing the structure of the burst format in the communication system of FIG. It is a figure which shows the structure of the 1st MIMO radio apparatus of FIG. It is a figure which shows the structure of the signal of the frequency domain in FIG. It is a figure which shows the structure of the 1st process part of FIG. It is a figure which shows the structure of the selection part of FIG. It is a figure which shows the structure of the data totaled in the total part of FIG. It is a sequence diagram which shows the transmission procedure of the signal in the communication system of FIG. 10 is a flowchart showing a signal transmission procedure in the first MIMO wireless apparatus of FIG. 9. It is a sequence diagram which shows the transmission procedure of the signal in the communication system which concerns on Example 2 of this invention. 12 is a flowchart illustrating a signal transmission procedure in the first MIMO wireless apparatus of FIG. 11.

Explanation of symbols

  10 MIMO radio apparatus, 16 normal radio apparatus, 20 radio section, 22 processing section, 24 modem section, 26 IF section, 30 control section, 32 acquisition section, 34 selection section, 80 separation section, 82 counting section, 84 determination section, 100 Communication system.

Claims (7)

A first control signal corresponding to one of the plurality of antennas and a burst signal in which data signals respectively corresponding to at least two of the plurality of antennas are arranged are transmitted at a predetermined timing. A transmitter that periodically transmits the second control signal by switching while selecting
Acquisition of information on the antenna of the transmission source of the second control signal received by the wireless device from a wireless device that is targeted for processing the first control signal of the burst signal and not the data signal. And
A selection unit that selects an antenna that should transmit the first control signal among a plurality of antennas based on information about the antenna acquired by the acquisition unit;
The transmission unit transmits a first control signal from an antenna selected by the selection unit when transmitting a burst signal. When transmitting the second control signal, the transmission unit includes an identification code of an antenna to which the second control signal should be transmitted in the second control signal,
The radio apparatus according to claim 1, wherein the acquisition unit acquires an antenna identification code included in a signal from the radio apparatus as information about the antenna. A receiving unit that receives signals from the wireless device by the plurality of antennas;
A measuring unit that measures the quality of the signal received at each of the plurality of antennas;
The radio apparatus according to claim 1, wherein the acquisition unit selects one antenna based on each of the measured qualities, and uses the identification code of the selected one antenna as information related to the antenna.   The selection unit aggregates information on antennas acquired by the acquisition unit in units of antenna identification codes, and selects an antenna to which the first control signal is to be transmitted based on the aggregation result. The wireless device according to claim 2, wherein: A storage unit for storing an identification code of the wireless device to be prioritized;
The acquisition unit also acquires the identification code of the wireless device included in the signal from the wireless device,
If the identification code of the wireless device acquired in the acquisition unit corresponds to the identification code of the wireless device stored in the storage unit, the selection unit gives priority to information on the antenna corresponding to the signal, The radio apparatus according to claim 2 or 3, wherein an antenna to which the first control signal is to be transmitted is selected.   The radio apparatus according to claim 1, wherein the selection unit updates the selected antenna at a predetermined timing. A first control signal corresponding to one of the plurality of antennas and a burst signal in which data signals respectively corresponding to at least two of the plurality of antennas are arranged are transmitted at a predetermined timing. A transmission method for periodically transmitting the second control signal by switching while selecting
After acquiring information on the antenna of the transmission source of the second control signal received by the wireless device from the wireless device that is targeted for processing the first control signal of the burst signal and not the data signal. A transmission method comprising: selecting an antenna that should transmit a first control signal from a plurality of antennas based on the information, and transmitting the first control signal.

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