JP4806660B2 - Wireless communication system and communication method thereof - Google Patents

Description

  According to the present invention, in a wireless communication system that operates a plurality of systems at the same frequency, a new system (Secondary system) does not receive interference from the Primary system based on information from a conventional system (priority system: Primary system), and The present invention relates to a radio communication system that does not interfere with a primary system and a communication method therefor.

  In recent years, with the widespread use of mobile phones, wireless LANs, and the like, techniques for performing transmission as fast as possible in a limited frequency band have been studied. In recent years, MIMO (Multiple Input Multiple Output) technology has attracted attention as means for realizing high-speed transmission in a limited band. MIMO uses array antennas for the transmitting side and the receiving side, respectively, and on the transmitting side, different data is transmitted for each antenna, and on the receiving side, different signals are restored by some interference cancellation / decoding technology. By doing so, it is a technique that remarkably improves the transmission speed at the same frequency as compared with transmission / reception between single antennas. Already introduced in wireless LAN systems and the like.

  However, in the MIMO technology, the number of transmission / reception antennas is a key for high-speed transmission. Therefore, in order to realize very high frequency utilization efficiency, a considerable number of antenna elements are required. When considering a small terminal, an increase in the number of antenna elements is undesirable because it increases the hardware scale.

  Cognitive radio technology has attracted attention as a means for effectively using frequencies by a method different from the MIMO technology (see, for example, Non-Patent Document 1). The cognitive radio technology is a technology in which a radio device recognizes a surrounding radio wave environment, selects an appropriate frequency band and uses it, thereby effectively utilizing an available frequency band. Since cognitive radio can effectively use frequencies and time that have not been attracting attention, the frequency per unit area can be greatly improved.

  FIG. 7 is a conceptual diagram for explaining the outline of the cognitive radio technology. In FIG. 7, 1-1 and 1-2 are two priority systems (Primary system), and 2-1 to 2-6 are a plurality of cognitive systems (Secondary systems). Reference numeral 3 denotes a communicable area of the primary system. Reference numerals 4-1 and 4-2 denote antenna directivities of the primary systems 1-1 and 1-2, respectively.

In cognitive radio, the primary systems 1-1 and 1-2 that originally use a certain communication band and the frequencies and times that are not used by the primary systems 1-1 and 1-2 are monitored, and this information is obtained. There are secondary systems 2-1 to 2-6 that perform communication based on the above. Basically, the primary systems 1-1 and 1-2 can use a preferentially assigned communication band, and the secondary systems 2-1 to 2-6 can perform communication by themselves. By interfering with the primary systems 1-1 and 1-2, the efficiency of the primary systems 1-1 and 1-2 should not be reduced. In addition, the primary systems 1-1 and 1-2 cannot normally recognize the existence of the secondary systems 2-1 to 2-6.
S. Haykin, “Cognitive radio: Brain-employed wireless communications”, vol. 23, no. 2, pp. 201-220, Feb. 2005.

In cognitive radio, communication is usually performed by the following means.
(Procedure 1) The Secondary systems 2-1 to 2-6 detect times or frequencies that are not used by the Primary systems 1-1 and 1-2.
(Procedure 2) The Secondary systems 2-1 to 2-6 confirm whether or not to interfere with the receivers of the Primary systems 1-1 and 1-2 through communication performed by themselves.
(Procedure 3) If the Secondary systems 2-1 to 2-6 determine that there is no problem in the procedure 2, the communication is performed at the frequency or time detected in the procedure 1.

  The above is the communication procedure in cognitive radio. However, first, a problem occurs when the procedure 1 is performed. For example, consider TDD (Time Division Duplex). In a TDD system, a station receives at a certain timing and does not transmit during that time. On the other hand, no signal is received during transmission. As hardware, a time division switch (TDD switch) is arranged between the transmission device and the reception device. Therefore, for example, even if interference from the primary system 1-1 is not detected at a certain time, if transmission is performed at that time, interference is given to the primary system 1-2.

  Further, even if the receivers of the secondary systems 2-1 to 2-6 determine that no signal has arrived at “a certain frequency” or “a certain time”, the state fluctuates with time. The signal may not be detected correctly due to the possibility or the presence of a hidden terminal. Therefore, in cognitive radio, signal detection with very high accuracy is required.

  As a means for improving this, a detection method using signal periodicity has been proposed. This is described in, for example, Reference 1 (D. Cabric, S.M. pp. 772-776, 7-10 / Nov / 2004.). In this method, signal detection is possible even at a very low CNR (Carrier to Noise Ratio) if the carrier frequencies of the Primary systems 1-1 and 1-2, or the symbol rate and modulation scheme are known in advance. . However, this method requires a very large amount of time and the number of signal samples for detection, so that it is difficult to cope with a case where the propagation environment of the primary systems 1-1 and 1-2 changes. Occurs.

  Next, a problem also occurs in the above procedure 2. As described above, in principle, the primary systems 1-1 and 1-2 cannot recognize the secondary system. For example, even if the secondary systems 2-1 to 2-6 determine that the signal level from the transmitter of the primary system 1-1 is low at a certain frequency and determine that this frequency can be used, transmission is performed as is at that frequency. May cause interference to the primary system 1-2. Therefore, the interference given by the Secondary systems 2-1 to 2-6 is most surely determined by the receivers of the Primary systems 1-1 and 1-2.

  However, the primary systems 1-1 and 1-2 cannot recognize the existence of the secondary systems 2-1 to 2-6. Therefore, in order to realize this, the secondary systems 2-1 to 2-6 regularly observe a certain signal generated by the primary systems 1-1 and 1-2, and the primary systems 1-1 and 1-2 have A method of grasping the existence is considered.

  Even if this is not cognitive radio, it can be considered as the same principle as carrier sense in the conventional radio system. The carrier sense is disclosed in, for example, Reference 2 (Morikura, Kubota, “Revised 802.11 High-Speed Wireless LAN Textbook”, Impress, 2004). When the secondary systems 2-1 to 2-6 approach the receivers of the primary systems 1-1 and 1-2, the primary system 1 is received by receiving signals transmitted from the primary systems 1-1 and 1-2. -1, 1-2 are grasped, and the secondary systems 2-1 to 2-6 can perform the procedure 2 based on the magnitude of the signal power.

  However, when considering cognitive radio, if the primary systems 1-1 and 1-2 eventually generate intentional signals for notifying their existence, it is necessary to provide a mechanism other than normal communication. This leads to hardware complexity. Further, it is necessary to newly provide a frequency and time for transmitting this signal. This causes a problem that it becomes a factor of reducing the communication utilization efficiency of the primary systems 1-1 and 1-2.

  The present invention has been made in view of such circumstances, and its purpose is an environment in which the Primary system employs an FDD (Frequency Division Duplex) system that uses different frequency bands for transmission and reception. Another object of the present invention is to provide a radio communication system capable of performing cognitive radio without interfering with each other between the primary system and the secondary system, and a communication method therefor.

In order to solve the above-described problem, the present invention includes a first wireless system including a plurality of wireless stations having priority and a second wireless system including a plurality of wireless stations not having priority. The base station of the first radio system and a plurality of subscriber stations use the first frequency band for the downlink signal from the base station of the first radio system to the subscriber station, and In a communication system for performing communication by time-division multiplexing the downlink signal and the uplink signal using a second frequency band for the uplink signal from the user station to the base station of the first wireless system, In the second radio system, the base station of the second radio system transmits the first radio system based on a downlink signal in the first frequency band transmitted from the base station of the first radio system. The amount of interference given to the base station When the interference amount estimation means to be determined and the interference amount is larger than a threshold value, the first frequency band is used as a use frequency band, and the interference amount is smaller than the threshold value. , said second frequency band determining unit according to the frequency band used frequency band, based on the base station of the first wireless system to said interfering amount scheduling information to be transmitted to the subscriber station When the amount of interference is larger than a threshold value, the first wireless system joins in the downlink from the base station of the first wireless system using the first frequency band to the subscriber station. The amount of interference given to the user station is estimated, communication is performed using a timing at which the amount of interference given to the subscriber station of the first wireless system is equal to or less than the threshold, and the amount of interference is smaller than the threshold In the case, the first using the second frequency band Communicate with the timing of uplink is not a interference from subscriber stations in the line system to the base station, avoiding means for avoiding interference from the first wireless system f of the interfering and the first wireless system A wireless communication system.

In order to solve the above-described problem, the present invention includes a first wireless system including a plurality of wireless stations having priority and a second wireless system including a plurality of wireless stations not having priority. The base station of the first radio system and a plurality of subscriber stations use the first frequency band for the downlink signal from the base station of the first radio system to the subscriber station, and In a communication system for performing communication by time-division multiplexing the downlink signal and the uplink signal using a second frequency band for the uplink signal from the user station to the base station of the first wireless system, Downlink reception power measuring means for measuring downlink reception power of a downlink signal from the base station of the first radio system to the subscriber station, and uplink from the subscriber station of the first radio system to the base station Uplink received power of line signal Uplink received power measuring means for measuring, amplifier gain holding means for holding gain values of amplifiers of the first radio system and the second radio system, and downlink measured by the downlink received power measuring means Based on the received power and the gain value of the amplifier held in the amplifier gain holding means, the interference estimation means for estimating the amount of interference given to the base station of the first radio system by the second radio system When the amount of interference estimated by the interference estimation unit is larger than a threshold, the first frequency band is used as a use frequency band, and when the amount of interference is smaller than the threshold, a transceiver frequency band determination means for the used frequency band of the second frequency band, the scheduling information obtaining means for obtaining scheduling information of the first wireless system, the If the amount of interference is greater than the threshold, the subscriber station of the first radio system in the downlink from the base station of the first radio system using the first frequency band to the subscriber station When the amount of interference to be applied is estimated, the timing at which the amount of interference to be given to the subscriber station of the first wireless system falls below the threshold is detected as an empty channel, and the amount of interference is smaller than the threshold Detects a timing at which the uplink from the subscriber station of the first radio system using the second frequency band to the base station does not interfere with the idle channel as a free channel. Empty channel detecting means for detecting a channel , and communication channel determining means for determining an empty channel detected by the empty channel detecting means as a communication channel of the second wireless system. A wireless communication system is provided.

The present invention further comprises interference signal removal means for removing an interference signal from the first radio system when the number of empty channels is less than the number of channels required by the communication channel determination means in the above invention. It is characterized by doing.

  The present invention includes the transmission power control means for controlling the transmission power of the second system so that the amount of interference estimated by the interference estimation means does not exceed a threshold value in the above invention. It is characterized by.

  In order to solve the above-described problem, the present invention includes a first wireless system including a plurality of wireless stations having priority and a second wireless system including a plurality of wireless stations not having priority. The base station of the first radio system and a plurality of subscriber stations use the first frequency band for the downlink signal from the base station of the first radio system to the subscriber station, and In a communication system for performing communication by time-division multiplexing the downlink signal and the uplink signal using a second frequency band for the uplink signal from the user station to the base station of the first wireless system, A control station arranged in the vicinity of the base station of the second radio system, wherein the control station has received downlink power of a downlink signal from the base station of the first radio system to the subscriber station; Downlink received power measuring means to measure and An uplink received power measuring means for measuring an uplink received power of an uplink signal from a subscriber station to a base station of the first radio system; an amplifier of the first radio system and the second radio system; Based on the amplifier gain holding means for holding the gain value, the downlink received power measured by the downlink received power measuring means, and the gain value of the amplifier held in the amplifier gain holding means, the second An interference estimation means for estimating the amount of interference given by the base station of the wireless system to the base station of the first wireless system; and when the estimated amount of interference is greater than a threshold, When the frequency band of 1 is set as the use frequency band and is smaller than the threshold, the transmission / reception frequency band determining means using the second frequency band as the use frequency band; Based on scheduling information acquisition means for acquiring scheduling information, and uplink reception power measured by the scheduling information and the uplink reception power measurement means, a free channel of a terminal of the first radio system is detected. A wireless communication system, comprising: a free channel detecting means for performing notification; and a notification means for notifying a free channel detected by the free channel detecting means to a base station and a terminal of the second wireless system. is there.

In order to solve the above-described problem, the present invention provides a first wireless system including a plurality of wireless stations having priority and a second wireless system including a plurality of wireless stations not having priority. The base station of the first radio system and a plurality of subscriber stations use the first frequency band for the downlink signal from the base station of the first radio system to the subscriber station, A communication method for performing communication by time division multiplexing the downlink signal and the uplink signal using a second frequency band for the uplink signal from the subscriber station to the base station of the first wireless system The base station of the second radio system supplies the base station of the first radio system to the base station of the first radio system based on the downlink signal of the first frequency band transmitted from the base station of the first radio system. Estimating the amount of interference; and Based from the base station of the first wireless system and the interfering amount scheduling information to be transmitted to the subscriber station, if the interfering amount is larger than the threshold value, the first frequency band The amount of interference given to the subscriber station of the first radio system in the downlink from the base station of the first radio system using the first radio system to the subscriber station, and the interference given to the subscriber station of the first radio system If the amount of interference is smaller than the threshold value, communication is performed using a timing at which the amount is less than or equal to the threshold value. From the subscriber station of the first wireless system using the second frequency band, Communicating with a timing at which the uplink to the base station does not cause interference to avoid interference with the first radio system and interference from the first radio system. Wireless communication method

In order to solve the above-described problem, the present invention provides a first wireless system including a plurality of wireless stations having priority and a second wireless system including a plurality of wireless stations not having priority. The base station of the first radio system and a plurality of subscriber stations use the first frequency band for the downlink signal from the base station of the first radio system to the subscriber station, A communication method for performing communication by time division multiplexing the downlink signal and the uplink signal using a second frequency band for the uplink signal from the subscriber station to the base station of the first wireless system Measuring the downlink received power of the downlink signal from the base station of the first radio system to the subscriber station; and the uplink signal from the subscriber station of the first radio system to the base station. Step to measure uplink received power And the step of holding the gain values of the amplifiers of the first radio system and the second radio system, and the second downlink power and the gain value of the amplifier based on the measured downlink received power and the gain value of the amplifier. Estimating a first amount of interference given to the base station of the first radio system by the base station of the radio system; and when the first amount of interferer is greater than a threshold, A frequency band of 2 is a frequency band used by the second radio system, and if the frequency band is smaller than a threshold, the second frequency band is a frequency band used by the second radio system ; If the amount of interference is greater than a threshold value, the subscriber of the first radio system in the downlink from the base station of the first radio system using the first frequency band to the subscriber station Estimate the amount of interference to the station The timing at which the amount of interference given to the subscriber station of the first wireless system falls below the threshold is detected as an empty channel, and when the amount of interference is smaller than the threshold, the second frequency band Detecting a free channel of a terminal of the first wireless system by detecting, as a free channel, a timing at which the uplink from the subscriber station of the first wireless system using the base station does not interfere with the base station; and Determining a detected empty channel as a communication channel of the second wireless system.

According to the present invention, in the above invention, the step of acquiring scheduling information included in an uplink signal from the first radio system, and the second frequency band is determined as a use frequency band of the second radio system And receiving based on the scheduling information using a free channel that is not subject to interference, and determining whether or not the number of free channels is greater than the total number of terminals in the second wireless system. And a weight that reduces interference from a subscriber station of the first wireless system by the second wireless system when the number of empty channels is larger than the total number of terminals of the second wireless system. And receiving.

  According to the present invention, in the above invention, when the first amount of interference is smaller than a threshold value, the step of determining the first frequency band as a use frequency band of the second radio system; , When acquiring scheduling information included in an uplink signal from a subscriber station of the first radio system, and when the first frequency band is determined to be a use frequency band of the second radio system, Based on the measured received power by the second system and the power ratio of the base station of the second radio system and the amplifier of the terminal, the base station of the second radio system sends the first radio Based on the step of estimating the second amount of interference given to the subscriber station of the system, and the timing at which the second amount of interference is less than or equal to the threshold, the second radio system causes the second interference amount to be No The method further includes a step of controlling transmission timing of the system, and a step of calculating a weight for reducing interference from a base station of the first wireless system by the second wireless system, and receiving using the weight. It is characterized by that.

  The present invention is characterized in that, in the above-described invention, the method further includes a step of controlling transmission power of the second radio system so that the estimated amount of interference does not exceed a threshold value.

  In order to solve the above-described problem, the present invention provides a first wireless system including a plurality of wireless stations having priority and a second wireless system including a plurality of wireless stations not having priority. The base station of the first radio system and a plurality of subscriber stations use the first frequency band for the downlink signal from the base station of the first radio system to the subscriber station, A communication method for performing communication by time division multiplexing the downlink signal and the uplink signal using a second frequency band for the uplink signal from the subscriber station to the base station of the first wireless system The control station arranged in the vicinity of the base station of the second radio system measures the downlink received power of the downlink signal from the base station of the first radio system to the subscriber station; and The subscriber station of the first radio system Measuring uplink received power of an uplink signal to a base station; holding gain values of amplifiers of the first radio system and the second radio system; and the measured downlink received power Estimating the amount of interference given by the base station of the second radio system to the base station of the first radio system based on the gain value of the amplifier held in the amplifier gain holding means; When the estimated amount of interference is larger than a threshold value, the first frequency band is used as a use frequency band, and when it is smaller than the threshold value, the second frequency band is used. A frequency band, a scheduling information acquisition step of acquiring scheduling information of the first radio system, the scheduling information and the measured uplink reception Detecting a vacant channel of a terminal of the first radio system based on power, and notifying the detected vacant channel to a base station and a terminal of the second radio system. This is a wireless communication method.

  According to this invention, the second radio system is configured so that the base station of the second radio system transmits the first frequency band downlink signal transmitted from the base station of the first radio system. When the amount of interference given to the base station of the wireless system is estimated and the amount of interference is larger than the threshold value, the first frequency band is set as the use frequency band, and the amount of interference is less than the threshold value. If it is small, the second frequency band is used as a frequency band to be used, and based on scheduling information transmitted from the base station of the first radio system to the subscriber station and the amount of interference, Interference and from the first wireless system. Therefore, the difference in traffic density between the primary system base station and the subscriber station is utilized to monitor the signal from the primary system base station, and the secondary system determines the frequency band to be used according to the signal strength. Thus, there is an advantage that the cognitive radio can be started under a condition that causes as little interference as possible to the Primay system.

  Further, according to the present invention, the downlink received power of the downlink signal from the base station of the first radio system to the subscriber station, and the uplink signal from the subscriber station of the first radio system to the base station Uplink received power is measured, the gain values of the amplifiers of the first radio system and the second radio system are held, and based on the measured downlink received power and the gain values of the held amplifiers The second wireless system estimates the amount of interference given to the base station of the first wireless system, and if the estimated amount of interference is larger than the threshold, the first frequency band is used as a frequency. If the frequency band is smaller than the threshold value, the second frequency band is set as the use frequency band, the scheduling information of the first radio system is acquired, and the scheduling information and the measured uplink received power are Based on the first Detecting a vacant channel of the terminal of a radio system, on the basis of the estimated interfering amount and idle channels to determine the communication channel of the second wireless system. Therefore, the secondary system acquires scheduling information transmitted from the primary system to the subscriber station, and assigns a channel to be used in the secondary system based on the scheduling information, so that interference from the primary system to the secondary system can be performed as much as possible. The advantage is that cognitive radio can be realized without interference and without causing interference to the primary system.

  Further, according to the present invention, when a communication channel is not determined, an interference signal from the first radio system is removed. Therefore, there is an advantage that cognitive radio can be realized without interference from the primary system to the secondary system as much as possible and without causing interference to the primary system.

  In addition, according to the present invention, the transmission power of the second system is controlled so that the estimated amount of interference does not exceed the threshold value. Therefore, there is an advantage that a channel that cannot be used because the amount of interference exceeds a threshold value can be used.

  Also, according to the present invention, some functions of the base station and terminal of the second radio system, that is, downlink received power measuring means, uplink received power measuring means, amplifier gain holding means, and interference estimation Means, transmission / reception frequency band determination means, scheduling information acquisition means, idle channel detection means, and notification means for notifying the detected idle channel to the base station and terminal of the second radio system, A control station arranged in the vicinity of the base station of the wireless system is prepared. Therefore, there is an advantage that it can be operated efficiently only in the frequency band used by the access point or the terminal.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a conceptual diagram for explaining a communication system according to the first embodiment of the present invention. FIG. 1 shows an example of the transmission / reception cycle of the primary system in TDMA (Time Division Multiple Access) -FDD (Frequency Division Duplex) of the primary system. In a conventional wireless system, a single frequency is different for a plurality of subscriber stations SS # 1 to SS # 3 with respect to one base station (primary system base station BS (Base Station)), which is called multiple access. When dividing by frequency, code, etc., the order of transmission and reception between the base station BS and the subscriber stations SS # 1 to SS # 3 must be determined. This is called scheduling.

  In this case, since it is necessary to share scheduling information between the base station BS and the non-end SS # 1 to SS # 3, the header portion is always the base station BS and the subscriber station as shown in FIG. Provided between SS # 1 to SS # 3. In the example shown in FIG. 1, scheduling information is provided at the beginning of the downlink (base station: transmission, terminal: reception). is there.

  Further, since the subscriber stations SS # 1 to SS # 3 also transmit the scheduling information to the base station BS, the scheduling information is also included in the transmission signals from the subscriber stations SS # 1 to SS # 3. In any case, as an important point, if the secondary systems 101-1 and 101-2 can receive the scheduling information, the order in which the terminals TS transmit can be grasped. The present invention takes advantage of this feature.

  In this example, it is assumed that three users are divided by time for one channel. However, in reality, there are f1 (1) to f1 (N) (N: number of channels) channels on the downlink frequency axis, and f2 (1) to f2 (N) channels on the uplink frequency axis. Will do. FIG. 1 shows only f1 (1) and f2 (1), that is, only the channel on the first frequency axis for simplification. As is clear from FIG. 1, since the base station BS of the primary system 100 must communicate with all the subscriber stations SS # 1, SS # 2, SS # 3, the base station BS Will be used.

  On the other hand, the subscriber stations SS # 1, SS # 2, and SS # 3 do not use the channel at the time when other terminals communicate. That is, the probability of giving interference to the terminals SS # 1, SS # 2, and SS # 3 is lower than that of the base station BS. Further, as shown in FIG. 1, when the primary system 100 has a relatively large service area and the secondary systems 101-1 and 101-2 have a small service area, the primary system 100 is more secondary. This means that transmission is performed with a larger transmission power than the systems 101-1 and 101-2.

  In such a case, even if an interference wave reaches the secondary systems 101-1 and 101-2 from the base station BS of the primary system 100, the base station BS of the primary system 100 from the secondary systems 101-1 and 101-2 Interference waves may not reach. That is, in the example illustrated in FIG. 1, the secondary system 101-1 may cause interference to the base station BS, but the secondary system 101-2 has less possibility. Therefore, even when all the channels of the base station BS are used, there is a case where interference with the base station BS does not occur depending on the positions of the secondary systems 101-1 and 101-2. The present invention uses the above-described features of the present invention when the secondary systems 101-1 and 101-2 having a relatively small service area exist in the FDD system with respect to the primary system 100.

  Next, FIG. 2 is a block diagram showing the configuration of the communication apparatus (access point) according to the first embodiment. In the figure, a plurality of receivers 112-1 to 212 -K and a plurality of transmitters 113-1 to 213 -K are each set, and each array antenna is connected via transmission / reception separators 111-1 to 111 -K. 110-1 to 110-K. Each of the transmission / reception separating units 111-1 to 111-K is connected to the receivers 112-1 to 112-K and the transmitters 113-1 to 113-K and the array antennas 110-1 to 110-K according to a predetermined timing. Switch the connection.

  The reception signal branching unit 114 branches the reception signals received by the receivers 112-1 to 112 -K, receives the reception power determination unit 115, the reception power determination unit 116, the primary system scheduling information acquisition unit 120, and interference This is supplied to the signal removal weight calculator 123. The reception power determination unit 115 measures the reception power of the downlink signal (frequency f1) from the base station BS of the primary system to the subscriber stations SS # 1 to SS # 3 and notifies the interference estimation unit 118 of the reception power. The reception power determination unit 116 measures the reception power of the uplink signal (frequency f2) from the subscriber stations SS # 1 to SS # 3 of the primary system 100 to the base station BS, and notifies the interference estimation unit 118 of the reception power.

  The interfering estimation unit 118 receives the received power of the downlink signal (frequency f1) from the base station BS of the primary system to the subscriber stations SS # 1 to SS # 3 or the subscriber stations SS # 1 to SS # 1 of the primary system 100. From the received power of the uplink signal (frequency f2) from SS # 3 to the base station BS and the power ratio between the amplifiers of the access point AP and the subscriber stations SS # 1 to SS # 3, the base station of the primary system 100 Estimate the amount of interference given to the BS. The amplifier value holding unit 119 holds the values of the amplifiers of the primary system 100 and the secondary systems 101-1 and 101-2. The scheduling information acquisition unit 120 acquires scheduling information from uplink signals from the subscriber stations SS # 1 to # 3 to the base station BS. The idle channel detection unit 121 detects an idle channel that does not cause interference from the interference power and scheduling information of each of the subscriber stations SS # 1 to # 3.

  The AP / terminal use channel determination unit 122 determines a free channel to be allocated to the access point AP and the terminal TS from the available free channels when communication is started. The interference signal removal weight calculation unit 123 receives signals from the subscriber stations SS # 1 to SS # 3 when all channels are filled with interference from the subscriber stations SS # 1 to SS # 3. A weight for canceling the interference is generated, and the weight is weighted by the weight to cancel the interference.

  The transmission signal generation unit 124 generates a transmission signal according to the empty channel determined by the AP / terminal use channel determination unit 122 and supplies the transmission signal to the transmitters 113-1 to 113-K via the branching unit 125. Further, the transmission / reception frequency band determination unit 126 determines a frequency band to be used in the secondary system 101 based on the amount of interference estimated by the interference estimation unit 118, and the reception operation of the receivers 112-1 to 112-K. To control.

Next, FIG. 3 is a flowchart for explaining the operation of the first embodiment.
First, a place where a new secondary system access point AP is to be installed is determined (step S1). Next, in the access point AP, the reception power determination unit 115 measures the reception power (downlink power) of the downlink signal (frequency band f1) transmitted from the base station BS to the subscriber stations SS # 1 to SS3. (Step S2).

  As shown in FIG. 1, the primary system 100 generally has a plurality of frequency channels. Here, the expression “frequency band” represents a plurality of frequency channels. When a single frequency channel is represented, it is expressed as f1 (*) or f2 (*). When the primary system 100 has a plurality of frequency channels, the received power for each frequency channel is measured and averaged.

Next, after measuring the received power of the downlink, the access point AP estimates a given interference power that may be given to the base station BS of the Primary system 100. This can be realized if the secondary systems 101-1 and 101-2 recognize the antenna gain of the primary system 100 and the gain of the amplifier. The received power R _BS-AP received by the access point AP from the base station BS of the primary system 100 and the interference signal noise power ratio INR _AP of the access point AP are given by the following equations (1) and (2).

  Here, G represents the gain of the amplifier and the antenna. The suffix HPA corresponds to the transmission amplifier, LNA corresponds to the reception amplifier, and ANT corresponds to the antenna. The subscripts BS and AP are generated at the base station BS and the access point AP. L represents the path loss of the propagation path.

Similarly, the interference power _RAP-BS given from the access point AP to the base station BS and the interference signal noise power ratio INR _BS in the base station BS are given by the following equations (3) and (4).

  Here, when calculation of Formula (1)-Formula (3) is performed, the following Formula (5) is obtained.

Here, since the reversibility of the propagation path is established, the relationship of L _BS-AP = L _AP-BS is used. When the formula (5) is substituted for the formula (4), the following formula (6) is obtained.

That is, the interference from the access point AP to the base station BS can be given by Expression (6). This is because the interference signal noise power ratio INR _AP obtained by being transmitted from the base station BS to the access point AP, the difference between the reception amplifier and the gain of the base station BS and the access point AP, the transmission amplifier of the access point AP and the base station BS, and Expressed in gain difference. The first term of Equation (6) is obtained when the access point AP receives a received signal, and the second and third terms are obtained by recognizing the gain of the amplifier of the Primary system 100.

  In FIG. 3, the interference estimation unit 118 calculates Equation (6) to estimate the amount of interference (step S3). In order to perform this calculation, the amplifier values of the primary system 100 and the secondary systems 101-1 and 101-2 are acquired from the amplifier value holding unit 119 shown in FIG. Next, it is determined whether or not the estimated amount of interference exceeds a threshold value α (step S4).

  This threshold value α is set to a level that does not cause a problem in the operation of the primary system 100. For example, when Equation (6) is equal to or less than the thermal noise power (0 dB), it is determined that there is almost no problem. If the estimated amount of interference does not exceed the threshold value α, the frequency band to be used is set to f2 (uplink SS → BS) (step S5). Here, when the estimated amount of interference does not exceed the threshold value α, the frequency band f2 is used, including the access point AP, and the secondary systems 101-1 and 101-2 interfere with the base station BS. This is because the secondary systems 101-1 and 101-2 perform communication without considering the interference.

  On the other hand, when the estimated amount of interference exceeds the threshold value α, the frequency band to be used is set to f1 (downlink BS → SS) (step S10). In this case, that is, when there is a possibility of giving interference, the base station BS may receive a signal at all timings. For this reason, the frequency band f1 is used in order to avoid interference. In this case, since the downlink signals from the base station BS to the subscriber stations SS # 1 to # 3 are received, the secondary systems 101-1 and 101-2 are connected to the subscriber stations SS # 1 to # 3. It is necessary to pay attention to the interference. This result is supplied to the transmission / reception frequency band determination unit 126.

  In FIG. 1, the secondary system 101-1 is located in the vicinity of the base station BS, and the secondary system 101-2 is located far from the base station BS. In this case, since the signal from the Secondary system 101-2 does not cause interference with the base station BS, the frequency band f2 is used. On the other hand, the Secondary system 101-1 uses the frequency band f1 because it has a high probability of causing interference to the base station BS.

  Next, regardless of whether the frequency band f1 or the frequency band f2 is used, the access point AP acquires the uplink signal from the subscriber stations SS # 1 to # 3 and the scheduling information of the primary system (steps S6 and S11). ). At this time, the received power determination unit 116 determines the power (uplink signal power) of the uplink signal from the subscriber stations SS # 1 to # 3 to the base station BS. The scheduling information is acquired by the scheduling information acquisition unit 120.

  From here, the operation differs depending on whether the frequency band f1 (downlink) or the frequency band f2 (uplink) is used as the use frequency band. This is because required interference avoidance and interference cancellation differ between the two.

  First, a case will be described in which it is determined that the frequency band f2 (uplink: SS → BS) is used in the Secondary system 101-2 as the use frequency band. In this case, as described above, since the interference is a signal from the secondary system 101-2 to the base station BS, control is not necessary for this. In short, it is important how to avoid interference from the subscriber stations SS # 1- # 3.

  At this time, since the uplink signal power and scheduling information from each of the subscriber stations SS # 1 to # 3 to the base station BS are acquired, an empty channel that does not cause interference by the empty channel detection unit 121 is obtained. Detect (step S7). For example, in the example of FIG. 1, since the subscriber stations SS # 2 and SS # 3 are close to the secondary system 101-2 and the subscriber station SS # 1 is away from the secondary system 101-2, the subscriber station SS # 1 transmission timing (frequency band f2 (1)) is an empty channel.

  Next, it is determined whether or not the number of free channels that are not subject to interference is greater than the number of users (step S8). 101-2 starts communication as it is. When communication is started, an empty channel is allocated to the access point AP and the terminal TS by the AP / terminal use channel determination unit 122 shown in FIG.

  On the other hand, when the number of empty channels is smaller than the required number of channels, that is, when all the channels are filled with interference from the subscriber stations SS # 1 to SS # 3, the interference signal removal weights The calculation unit 123 generates a weight for canceling the interference from the signals from the subscriber stations SS # 1 to SS # 3, and performs weighting with the weight to cancel the interference (step S9).

  As a specific calculation method, a method known as an adaptive array antenna or an interference canceller may be applied. However, as described above, the signals from the subscriber stations SS # 1 to SS # 3 are transmitted at all times when viewed from the individual subscriber stations SS # 1, SS # 2, and SS # 3. Therefore, it is necessary to execute step S9 only when the subscriber stations SS # 1, SS # 2, and SS # 3 are all in the vicinity of the Secondary system 101-2 in the example of FIG. It is. In practice, the probability of this situation is low. Therefore, in reality, both interference avoidance and interference avoidance can be realized up to step S8. If step S9 is included, interference avoidance can be completely realized.

  Next, a case will be described in which it is determined that the frequency system f1 (downlink, BS → SS) is used in the Secondary system 101-1 as the use frequency band. In this case, instead of always avoiding interference with the base station kBS, it is necessary to avoid interference with the subscriber stations SS # 1 to SS # 3. Further, since interference always comes from the base station BS, in this case, interference cancellation for canceling the signal of the base station BS is necessarily required.

  First, in the access point AP, the interference estimation unit 118 measures the uplink signal reception power measured in step S11 and the power ratio between the amplifiers (transmission and reception) of the access point AP and the subscriber stations SS # 1 to SS # 3. Then, the amount of interference given to the subscriber stations SS # 1 to SS # 3 by the access point AP is estimated (step S12). This process can be realized by replacing BS with SS in the above-described equations (1) to (6). However, in this case, the amount of interference with respect to all the subscriber stations SS # 1 to SS # 3 is estimated based on the scheduling information acquired in step S11.

  Next, in the access point AP, the vacant channel detection unit 121 detects a vacant channel based on the timing when the interference power becomes equal to or less than the threshold, and the AP / terminal use channel determination unit 122 The transmission timing of the terminal TS is controlled (step S13). As a result, since a channel that may cause interference is not used as a transmission channel, interference from the secondary system 101-1 to the subscriber stations SS # 1 to SS # 3 can be avoided. Also, in this case, since the secondary system 101-1 uses the fact that the subscriber stations SS # 1 to SS # 3 have more free channels than the base station BS, the available channels should be used effectively. It is also possible.

  Finally, in the access point AP and the terminal TS, the interference signal removal weight calculation unit 123 calculates a weight for reducing the interference from the base station BS, and receives the weight using the weight (step S14). In this case, interference cancellation is always required, but a specific calculation method may be a method known from an adaptive array antenna or interference canceller, as in step S9 described above. However, since interference from the base station BS is always targeted, the interference information does not fluctuate and can be realized with relatively slow control.

  According to the first embodiment described above, the secondary systems 101-1 and 101-2 can avoid coherency with the primary system 100 and can realize cognitive radio without receiving interference from the primary system 100. Can do.

B. Second Embodiment Next, a second embodiment of the present invention will be described.
FIG. 4 is a block diagram for explaining a communication system according to the second embodiment. In the first embodiment described above, in order to estimate the amount of interference and the amount of interference from the primary system 100 and determine the frequency band to be used in the secondary systems 101-1 and 101-2, There was a need to receive a signal. However, the unused frequency band is inefficient because it is used only for this detection.

  In the second embodiment, as shown in FIG. 4, control stations 210-1 to 210-4 are provided in the secondary system 101-1, and these control stations 210-1 to 210-4 are shown in FIG. A part of the function of the access point AP is shared. As a result, it is possible to operate only in the frequency band used by the access point AP and the terminal TS.

  The control stations 210-1 to 210-4 include an antenna 210-2-1, a transmission / reception separating unit 210-2-2, a receiver 210-2-3, and a transmitter 210- corresponding to both the frequency bands f1 and f2. 2-4, a reception signal branching unit 210-2-5, an empty channel information notification unit 210-2-6, and a block 200 surrounded by a dotted line shown in FIG. That is, operations other than steps S9 and S14 shown in FIG. 3 are executed.

  The control stations 210-1 to 210-4 notify the information acquired by the control station to the access point AP and the terminal TS as the empty channel information by the empty channel information notification unit 210-2-6. Specifically, for example, when the secondary system 101-1 considers using the frequency band f1, the control station 210-1 receives the signal (f2) from the subscriber stations SS # 1 to SS # 3. Then, the flowchart shown in FIG. 3 is executed. However, since the interference cancellation needs to be performed by the access point AP or the terminal TS, the control stations 210-1 to 210-4 do not need to have these functions themselves. Further, as shown in the figure, even when the zone of the secondary system 101-1 is widened, if a plurality of control stations 210-1 to 210-4 are provided, highly accurate interference and interference can be detected.

  In the illustrated example, only the secondary system 101-1 has been described, but the same applies to the secondary system 101-2.

C. Third Embodiment Next, a third embodiment of the present invention will be described.
In the third embodiment, when the primary system 100 is a narrow-band system and the secondary systems 101-1 and 101-2 are wide-band systems, the secondary system is used by using transmission power control according to the interference power. The channel utilization efficiency of 101-1 and 101-2 is improved.

  FIG. 5 is a block diagram showing a configuration of a communication apparatus (access point) according to the third embodiment. It should be noted that parts corresponding to those in FIG. In the third embodiment, a transmission power determination unit 127 is provided. When the interference is a problem in many channels, that is, when the interference estimation unit 118 determines that the interference power exceeds a threshold value in many channels, Control is performed so that the transmission power in the transmission signal generator 124 is reduced to some extent.

  6A and 6B are conceptual diagrams for explaining a channel allocation method according to the third embodiment. In the figure, a case where a downlink signal (frequency band f1) is used as the secondary systems 101-1 and 101-2 is shown. In this case, it is necessary to avoid interference with the subscriber stations SS # 1 to SS # 3.

  As shown in FIG. 6A, the primary system 100 performs channel assignment to the subscriber stations SS # 1 to SS # 3 in the time direction and the frequency direction. This is the same as the method shown in FIG. On the other hand, in FIG. 6B, since the secondary systems 101-1 and 101-2 want to perform communication in a wide band, it is considered that communication is performed using a plurality of channels of the primary system 100. In addition, as shown in the figure, multiplexing is performed on the frequency axis using orthogonal frequency division multiplexing (Orthogonal Frequency Division Duplex).

  In OFDM, as shown in FIGS. 6A and 6B, subcarriers are arranged on the frequency axis like fs1, fs2,. In the illustrated example, two carriers are provided per f1 (1), but this value can be arbitrarily adjusted by the size of the FFT (Fast Fourier Transform) and the band to be used. Each subcarrier is orthogonal. OFDM is attracting attention as a technique for improving communication quality by broadband transmission. For example, it is disclosed in Document 2 mentioned above.

  In the first embodiment described above, when OFDM is used, if interference with subscriber stations SS # 1 to SS # 3 becomes a problem, interference is generated by transmitting the channel without setting up a subcarrier. Can be avoided.

  However, as shown in FIG. 6A, when the interference becomes a problem in many channels, the efficiency of the Secondary systems 101-1 and 101-2 is lowered. Therefore, in the third embodiment, transmission power control is used in combination. For example, when the original transmission power is P [dB] and the threshold level of interference is α [dB], and the transmission power is P-1 [dB], the interference level is α-1 [dB]. It becomes no problem. That is, sub-channel transmission power control may be performed so that the use of OFDM is effectively utilized and the interference level does not exceed the threshold value. Accordingly, it is possible to secure usable channels as compared with the first embodiment in which a channel that causes interference is not used.

  Specifically, in the first embodiment, a channel that could not be used can be used by reducing the transmission power of the subchannel. That is, if the interference level is β, the transmission power P (fs (k)) (k = 1, 2, 3, 4,...) Is determined by the following equation (7).

  In the above equation (7), Pmax is the transmission power when the interference does not matter.

  According to the third embodiment described above, the signal can be transmitted without reducing the channel efficiency as shown in FIG. 5B by reducing the transmission power of the subchannel and making it usable. Can do.

  According to the first to third embodiments described above, the difference in traffic density between the base station BS of the primary system 100 and the subscriber stations SS # 1 to SS # 3 is used to determine whether the base station BS of the primary system 100 By monitoring the signal and determining the frequency band used by the secondary systems 101-1 and 101-2 according to the signal strength, it is possible to start communication under conditions that do not interfere with the primary system 100 as much as possible. .

  Further, the secondary systems 101-1 and 101-2 acquire scheduling information transmitted from the primary system 100 to the subscriber stations SS # 1 to SS # 3, and based on the scheduling information, the secondary systems 101-1, By allocating a channel to be used in 101-2, cognitive radio is realized without receiving interference from the primary system 100 to the secondary systems 101-1 and 101-2 as much as possible and without causing interference to the primary system 100. be able to.

It is a conceptual diagram for demonstrating the communication system in 1st Embodiment of this invention. It is a block diagram which shows the structure of the communication apparatus (access point) by this 1st Embodiment. It is a flowchart for demonstrating the operation | movement of this 1st Embodiment. It is a block diagram for demonstrating the communication system by 2nd Embodiment of this invention. It is a block diagram which shows the structure of the communication apparatus (access point) by this 3rd Embodiment. It is a conceptual diagram for demonstrating the channel allocation method by this 3rd Embodiment. It is a conceptual diagram for demonstrating the outline | summary of a cognitive radio | wireless technique.

Explanation of symbols

100 Primary system (first wireless system)
BS base station subscriber station SS # 1- # 3
101-1 and 101-2 Secondary system (second wireless system)
AP access point (base station of second radio system)
TS terminal f1 frequency band (first frequency band)
f2 frequency band (second frequency band)
110-1 to 101-K antennas 111-1 to 111-K transmission / reception separators 112-1 to 112-K receivers 113-1 to 113-K transmitters 114 received signal branching units 115 received power determination units (power measuring means) )
116 Received power determination unit 118 Interference estimation unit (interference amount estimation means)
119 Amplifier value holding unit 120 Scheduling information acquisition unit (scheduling information acquisition means)
121 Free channel detection unit (free channel detection means)
122 AP / terminal use channel determination unit (frequency band determination means, transmission / reception frequency band determination means, communication channel determination means)
123 Weight calculation part for interference signal removal (avoidance means, interference signal removal means)
124 transmission signal generation unit 125 branching unit 126 transmission / reception frequency band determination unit 127 transmission power determination unit (transmission power control means)
210-2 to 210-4 Control station 210-2-1 Antenna 210-2-2 Transmission / reception separation unit 210-2-3 Receiver 210-2-4 Transmitter 210-2-5 Received signal branching unit 210-2- 6 Free channel information notification section (notification means)

Claims (11)

A first wireless system including a plurality of wireless stations having priority and a second wireless system including a plurality of wireless stations not having priority; a base station of the first wireless system; A plurality of subscriber stations use a first frequency band for downlink signals from the base station of the first radio system to the subscriber station, and from the subscriber station to the base station of the first radio system In a communication system that performs communication by time-division multiplexing the downlink signal and the uplink signal using a second frequency band for the uplink signal of
The second wireless system is:
The amount of interference that the base station of the second radio system gives to the base station of the first radio system based on the downlink signal of the first frequency band transmitted from the base station of the first radio system Interference amount estimation means for estimating
When the amount of interference is larger than a threshold value, the first frequency band is used as a use frequency band, and when the amount of interference is smaller than the threshold value, the second frequency band is used. A frequency band determining means for using a frequency band,
On the basis of the base station of the first wireless system and the interfering amount scheduling information to be transmitted to the subscriber station, the interfering amount if it is larger than the threshold value, the first Estimating the amount of interference given to the subscriber station of the first radio system in the downlink from the base station of the first radio system using the frequency band to the subscriber station, to the subscriber station of the first radio system Communication is performed using a timing at which the amount of interference to be applied is equal to or less than a threshold, and when the amount of interference is smaller than the threshold, the subscriber of the first radio system using the second frequency band An avoiding unit that communicates using a timing at which an uplink from the station to the base station does not cause interference to avoid interference with the first radio system and interference from the first radio system. Wireless communication system featuring Stem. A first wireless system including a plurality of wireless stations having priority and a second wireless system including a plurality of wireless stations not having priority; a base station of the first wireless system; A plurality of subscriber stations use a first frequency band for downlink signals from the base station of the first radio system to the subscriber station, and from the subscriber station to the base station of the first radio system In a communication system that performs communication by time-division multiplexing the downlink signal and the uplink signal using a second frequency band for the uplink signal of
Downlink received power measuring means for measuring downlink received power of a downlink signal from a base station to a subscriber station of the first wireless system;
Uplink received power measuring means for measuring the uplink received power of the uplink signal from the subscriber station of the first wireless system to the base station;
Amplifier gain holding means for holding gain values of amplifiers of the first wireless system and the second wireless system;
Based on the downlink received power measured by the downlink received power measuring means and the gain value of the amplifier held in the amplifier gain holding means, the second radio system is connected to the base of the first radio system. An interference estimation means for estimating the amount of interference given to the station;
When the amount of interference estimated by the interference estimation means is larger than a threshold value, the first frequency band is used as a use frequency band, and when the amount of interference is smaller than the threshold value, the second frequency band A transmission / reception frequency band determining means that uses the frequency band of
Scheduling information acquisition means for acquiring scheduling information of the first wireless system;
If the amount of interference is greater than a threshold value, the subscriber of the first radio system in the downlink from the base station of the first radio system using the first frequency band to the subscriber station The amount of interference given to the station is estimated, the timing when the amount of interference given to the subscriber station of the first wireless system falls below the threshold is detected as an empty channel, and the amount of interference is smaller than the threshold In this case, the terminal of the first radio system is detected by detecting, as an empty channel, a timing at which the uplink from the subscriber station of the first radio system using the second frequency band does not interfere with the base station. A free channel detecting means for detecting a free channel of
Wireless communication system, characterized by comprising a communication channel determining means for determining the detected idle channel from the idle channel detecting means, as the communication channel of the second wireless system. 3. The apparatus according to claim 2, further comprising: an interference signal removing unit that removes an interference signal from the first radio system when the number of empty channels is smaller than a required number of channels by the communication channel determining unit. The wireless communication system described.   The transmission power control means for controlling the transmission power of the second system so that the amount of interference estimated by the interference estimation means does not exceed a threshold value. Wireless communication system. A first wireless system including a plurality of wireless stations having priority and a second wireless system including a plurality of wireless stations not having priority; a base station of the first wireless system; A plurality of subscriber stations use a first frequency band for downlink signals from the base station of the first radio system to the subscriber station, and from the subscriber station to the base station of the first radio system In a communication system that performs communication by time-division multiplexing the downlink signal and the uplink signal using a second frequency band for the uplink signal of
Comprising a control station disposed in the vicinity of the base station of the second wireless system;
The control station
Downlink received power measuring means for measuring downlink received power of a downlink signal from a base station to a subscriber station of the first wireless system;
Uplink received power measuring means for measuring the uplink received power of the uplink signal from the subscriber station of the first wireless system to the base station;
Amplifier gain holding means for holding gain values of amplifiers of the first wireless system and the second wireless system;
Based on the downlink received power measured by the downlink received power measuring means and the gain value of the amplifier held in the amplifier gain holding means, the base station of the second radio system makes the first radio Interference estimation means for estimating the amount of interference given to the base station of the system;
When the estimated amount of interference is larger than a threshold value, the first frequency band is used as a use frequency band, and when it is smaller than the threshold value, the second frequency band is used. A transmission / reception frequency band determining means as a frequency band;
Scheduling information acquisition means for acquiring scheduling information of the first wireless system;
Based on the scheduling information and the uplink received power measured by the uplink received power measuring means, an empty channel detecting means for detecting an empty channel of a terminal of the first radio system;
A wireless communication system, comprising: a notification means for notifying a free channel detected by the free channel detection means to a base station and a terminal of the second wireless system. A first wireless system including a plurality of wireless stations having priority and a second wireless system including a plurality of wireless stations not having priority; a base station of the first wireless system; A plurality of subscriber stations use a first frequency band for downlink signals from the base station of the first radio system to the subscriber station, and from the subscriber station to the base station of the first radio system In a communication method for performing communication by time-division multiplexing the downlink signal and the uplink signal using a second frequency band for the uplink signal of
The amount of interference that the base station of the second radio system gives to the base station of the first radio system based on the downlink signal of the first frequency band transmitted from the base station of the first radio system Estimating
Based on the scheduling information transmitted from the base station of the first wireless system to the subscriber station and the amount of interference, if the amount of interference is greater than a threshold, the first Estimating the amount of interference given to the subscriber station of the first radio system in the downlink from the base station of the first radio system using the frequency band to the subscriber station, to the subscriber station of the first radio system Communication is performed using a timing at which the amount of interference to be applied is equal to or less than a threshold, and when the amount of interference is smaller than the threshold, the subscriber of the first radio system using the second frequency band Communicating with a timing at which the uplink from the station to the base station does not cause interference, and avoiding interference to the first radio system and interference from the first radio system. A wireless communication method. A first wireless system including a plurality of wireless stations having priority and a second wireless system including a plurality of wireless stations not having priority; a base station of the first wireless system; A plurality of subscriber stations use a first frequency band for downlink signals from the base station of the first radio system to the subscriber station, and from the subscriber station to the base station of the first radio system In a communication method for performing communication by time-division multiplexing the downlink signal and the uplink signal using a second frequency band for the uplink signal of
Measuring downlink received power of a downlink signal from a base station of the first wireless system to a subscriber station;
Measuring uplink received power of an uplink signal from a subscriber station of the first radio system to a base station;
Holding a gain value of an amplifier of the first wireless system and the second wireless system;
Estimating a first amount of interference that the base station of the second radio system gives to the base station of the first radio system based on the measured downlink received power and the gain value of the amplifier When,
When the first amount of interference is larger than a threshold value, the second frequency band is used as a frequency band used by the second radio system. When the first interference amount is smaller than a threshold value, Setting a second frequency band as a use frequency band of the second wireless system ;
If the amount of interference is greater than a threshold value, the subscriber of the first radio system in the downlink from the base station of the first radio system using the first frequency band to the subscriber station The amount of interference given to the station is estimated, the timing when the amount of interference given to the subscriber station of the first wireless system falls below the threshold is detected as an empty channel, and the amount of interference is smaller than the threshold In this case, the terminal of the first radio system is detected by detecting, as an empty channel, a timing at which the uplink from the subscriber station of the first radio system using the second frequency band does not interfere with the base station. Detecting free channels of
Determining the detected empty channel as a communication channel of the second wireless system. Obtaining scheduling information included in an uplink signal from the first wireless system;
When the second frequency band is determined to be a use frequency band of the second wireless system, based on the scheduling information, receiving using a free channel that is not subject to interference;
Determining whether the number of free channels is greater than the total number of terminals of the second wireless system;
When the number of empty channels is larger than the total number of terminals of the second wireless system, reception is performed by the second wireless system using a weight that reduces interference from subscriber stations of the first wireless system. The wireless communication method according to claim 7, further comprising: When the first amount of interference is smaller than a threshold value, determining the first frequency band as a use frequency band of the second radio system;
Obtaining scheduling information included in an uplink signal from a subscriber station of the first wireless system;
When the first frequency band is determined to be a frequency band used by the second radio system, the second system performs the measured received power and amplifiers of base stations and terminals of the second radio system. Estimating a second amount of interference given from the base station of the second radio system to the subscriber station of the first radio system based on the power ratio of:
Controlling the transmission timing of the second radio system by the second radio system based on the timing when the second amount of interference becomes equal to or less than the threshold;
The method according to claim 7, further comprising: calculating a weight for reducing interference from a base station of the first wireless system by the second wireless system, and receiving the weight using the weight. Wireless communication method.   8. The wireless communication method according to claim 7, further comprising a step of controlling transmission power of the second wireless system so that the estimated amount of interference does not exceed a threshold value. A first wireless system including a plurality of wireless stations having priority and a second wireless system including a plurality of wireless stations not having priority; a base station of the first wireless system; A plurality of subscriber stations use a first frequency band for downlink signals from the base station of the first radio system to the subscriber station, and from the subscriber station to the base station of the first radio system In a communication method for performing communication by time-division multiplexing the downlink signal and the uplink signal using a second frequency band for the uplink signal of
The control station arranged in the vicinity of the base station of the second wireless system is
Measuring downlink received power of a downlink signal from a base station of the first wireless system to a subscriber station;
Measuring uplink received power of an uplink signal from a subscriber station of the first radio system to a base station;
Holding a gain value of an amplifier of the first wireless system and the second wireless system;
Based on the measured downlink received power and the gain value of the amplifier held in the amplifier gain holding means, the base station of the second radio system gives to the base station of the first radio system Estimating the amount of interference;
When the estimated amount of interference is larger than a threshold value, the first frequency band is used as a use frequency band, and when it is smaller than the threshold value, the second frequency band is used. A step of setting a frequency band;
A scheduling information acquisition step of acquiring scheduling information of the first wireless system;
Detecting a free channel of a terminal of the first wireless system based on the scheduling information and the measured uplink received power;
Notifying the detected empty channel to a base station and a terminal of the second wireless system. A wireless communication method comprising:

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