JP5288469B2 - Wireless network system and control method thereof - Google Patents

Description

  The present invention provides a wireless local area network (hereinafter referred to as a local area network) that performs wireless communication by exchanging RTS (Request to Send) / CTS (Clear to Send) / DATA / ACK (Acknowledgement) signals, for example. A wireless system including a system and a secondary wireless communication system (hereinafter referred to as a secondary system) that is provided in the same cover area and performs wireless communication using the same operating frequency as the wireless LAN system. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wireless network system that enables wireless communication with a secondary system wireless station and a control method thereof.

  In recent years, with the increase in demand for wireless communication, severe frequency tightness has occurred. For this reason, research and development of a frequency sharing technique in which a plurality of wireless systems jointly use the same frequency band has been made for a significant improvement in frequency resource utilization efficiency (see, for example, Non-Patent Document 1). These frequency sharing technologies are roughly classified into a method in which the secondary system uses unused time and frequency in the primary system, and a method in which the primary and secondary systems use the same frequency at the same time. The former performs spectrum sensing for the operating frequency band and operates the secondary system in a time or frequency band that is not used. For this reason, when the network load of the primary system is high, the operating frequency band is occupied by the primary system, and the secondary system cannot communicate. On the other hand, in the latter, the secondary system takes measures against interference and simultaneously superimposes a plurality of communications at the same frequency. Since the arrival time of a desired signal cannot always be predicted in an asynchronous system, the receiver starts synchronization processing when an RSSI (Received Signal Strength Indication) exceeding a certain level is observed.

JP 2008-278450 A.

S. Haykin, "Cognitive radio: Brain-empowered wireless communications", IEEE Journal on Selected Areas in Communications, Vol.23, No.2, pp.201-220, February 2005. A. Singh, et al., "Spatial reuse through adaptive interference cancellation in multi-antenna wireless networks", Proceedings of IEEE GLOBECOM 2005, pp.3092-3096, December 2005. Yuta Nakao et al., "A Study on Interference Avoidance Technology for UWB-WPAN Using Weight Control Using Hierarchical Array Antenna Concept", Proceedings of SITA 2008, pp.293-298, October 2008. Jun Naganawa et al., “Modulation method that does not require channel information for superimposition communication by cognitive radio”, Society Conference of IEICE, B-17-9, February 2008. IEEE Standard 802.11-2007, Part11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications, June 2007. Nobuyoshi Kikuma, “Adaptive Antenna Technology”, Ohm, October 2003. Lal Chand Godara, "Smart Antenna", CRC Press LLC, January, 2004.

FIG. 3 is a timing chart showing an example of possible synchronization acquisition at the receiving wireless station of the secondary system in the wireless communication network according to the prior art, and FIG. 4 is a reception of the secondary system in the wireless communication network according to the prior art. It is a timing chart which shows the example in which the synchronous acquisition in a side radio station is impossible. That is, FIG. 3 and FIG. 4 show examples where synchronization acquisition is possible and impossible on the receiving side of the secondary system in superimposed transmission. In FIG. 3, the receiver starts synchronization processing (t0) with respect to a signal that arrives in advance, so that if the signal of the secondary system arrives within the time window (T _w ) of synchronization processing, synchronization acquisition is performed. Although it is possible (FIG. 3), synchronization acquisition becomes impossible when it comes after the time window (FIG. 4). Non-Patent Documents 2 to 4 disclose research examples related to superposition transmission. However, these do not take into account the above-mentioned problem relating to reception timing synchronization.

  Non-Patent Document 2 discloses that in a wireless LAN system in which radio communication is performed by exchanging RTS / CTS signals, an RTS / CTS signal is transmitted omnidirectionally, and a transmission beam is transmitted to a destination terminal when a DATA / ACK signal is transmitted. A method of forming is disclosed. In this method, the length of the NAV (Network Allocation Vector: a packet transmission prohibition period) is set to the RTS / CTS signal so that other terminals can start exchanging RTS / CTS signals during DATA transmission of the preceding communication. Only adjusted to protect. However, if the next RTS / CTS signal exchange is started during DATA transmission of the preceding communication, interference from the preceding communication occurs. As a result, there is a possibility that the reception timing synchronization of the RTS addressed to the own station, and thus the reception of the RTS signal, may fail.

  In Non-Patent Document 3, a coordinator device of an Ultra-Wideband Wireless Personal Area Network (UWB WPAN) has a directional antenna and is a wireless LAN existing in a signal band. There has been proposed a method for avoiding interference and interference by forming a null for a transmission / reception terminal of a system. When the PAN coordinator device exchanges the CTS / DATA signal of the wireless LAN system, it calculates the weight that forms a null for the wireless LAN system transmitting and receiving terminals, and can communicate with surrounding wireless PAN terminals using the obtained weight A control signal notifying that the transition has been made is transmitted. However, since the interference from the wireless LAN system is not suppressed, the wireless PAN terminal may not be able to detect the reception timing of the control signal transmitted from the PAN coordinator device. In addition, a technique has been proposed in which a transmission terminal of the secondary system receives a transmission signal of the primary system, adds its own low-power information signal, and retransmits the signal (for example, see Non-Patent Document 4).

  The receiving terminal of the primary system performs demodulation using the signals relayed from the transmitting terminal of the primary system and the transmitting terminal of the secondary system. The receiving terminal of the secondary system demodulates the desired signal after removing the interference from the primary system. However, since the signal of the secondary system is transmitted with sufficiently smaller power than that of the primary system, there is a possibility that accurate reception timing detection cannot be performed.

  The object of the present invention is to solve the above problems, for example, a wireless LAN system that performs wireless communication by exchanging RTS / CTS / DATA / ACK signals, and the same wireless LAN system that is provided in the same cover area as the wireless LAN system. In a wireless network system including a secondary system that performs wireless communication using an operating frequency of the same, it is possible to easily obtain timing synchronization and enable wireless communication at a wireless station of the secondary system, and It is to provide a control method.

A wireless network system according to a first invention is
A first wireless communication system configured with a plurality of wireless stations and performing data transmission after exchanging control signals;
A wireless network system including a second wireless communication system configured to include a plurality of wireless stations and performing data transmission using the same frequency band as that of the first wireless communication system and superimposed in time. And
The transmitting-side radio station of the second radio communication system receives the control signal of the first radio communication system, and predicts the data transmission timing of the first radio communication system based on the received control signal. And at the same time as the data transmission of the first wireless communication system at the predicted timing, the data to be transmitted is transmitted,
The receiving radio station of the second radio communication system receives the control signal of the first radio communication system, and predicts the timing of data transmission of the first radio communication system based on the received control signal. Then, data from the transmitting radio station of the second radio communication system is received at the predicted timing.

  In the wireless network system, the first wireless communication system is a wireless LAN system that performs wireless communication using a control signal that is an RTS / CTS signal, and the transmission-side wireless station and reception of the second wireless communication system. The side radio station receives the CTS signal from the first radio communication system, adds a short frame interval (SIFS) to the received CTS signal, and predicts the data transmission timing of the first radio communication system. It is characterized by doing.

  In the wireless network system, when the transmitting wireless station of the second wireless communication system receives a control signal from the receiving wireless station of the first wireless communication system, Based on this, the directivity pattern of data transmission is controlled so as to form a null for the receiving-side radio station of the first radio communication system using an adaptive control method.

  Furthermore, in the wireless network system, the transmitting wireless station of the second wireless communication system receives a control signal from the transmitting wireless station of the first wireless communication system and When the data length transmitted from the transmitting radio station is longer than the data length from the transmitting radio station of the first radio communication system, the adaptive control method is used to perform the first control based on the received control signal. A directivity pattern of data transmission is controlled so as to form a null for a transmitting-side radio station of a radio communication system.

Still further, in the wireless network system, when the receiving wireless station of the second wireless communication system receives the control signal from the transmitting wireless station of the first wireless communication system, the received control signal Based on the above, the directivity pattern of data reception is controlled using an adaptive control method so as to form a null for the transmitting-side radio station of the first radio communication system.

In the radio network system, the receiving radio station of the second radio communication system receives a control signal from the receiving radio station of the first radio communication system, and the second radio communication system When the data length transmitted from the transmitting radio station is longer than the data length from the transmitting radio station of the first radio communication system, the adaptive control method is used to perform the first control based on the received control signal. A directivity pattern of data reception is controlled so as to form a null for a receiving-side radio station of the radio communication system.

  Further, in the wireless network system, when the transmitting wireless station of the second wireless communication system receives a control signal from the first wireless communication system, whether or not to start data transmission according to predetermined access control It is characterized by determining.

The control method of the wireless network system according to the second invention is:
A first wireless communication system configured with a plurality of wireless stations and performing data transmission after exchanging control signals;
Control of a radio network system including a second radio communication system configured to include a plurality of radio stations and performing data transmission using the same frequency band as that of the first radio communication system and superimposed in time A method,
The transmitting-side radio station of the second radio communication system receives the control signal of the first radio communication system, and predicts the data transmission timing of the first radio communication system based on the received control signal. And at the same time as the data transmission of the first wireless communication system at the predicted timing, the data to be transmitted is transmitted,
The receiving radio station of the second radio communication system receives the control signal of the first radio communication system, and predicts the timing of data transmission of the first radio communication system based on the received control signal. Then, data from the transmitting radio station of the second radio communication system is received at the predicted timing.

  In the control method of the wireless network system, the first wireless communication system is a wireless LAN system that performs wireless communication using a control signal that is an RTS / CTS signal, and the transmission-side wireless of the second wireless communication system. The station and the receiving radio station receive the CTS signal from the first radio communication system, add a short frame interval (SIFS) to the received CTS signal, and perform data transmission of the first radio communication system. It is characterized by predicting timing.

  In the wireless network system control method, the transmitting wireless station of the second wireless communication system receives the control signal when receiving the control signal from the receiving wireless station of the first wireless communication system. Based on the control signal, the directivity pattern of data transmission is controlled using an adaptive control method so as to form a null for the receiving radio station of the first radio communication system.

  Furthermore, in the control method of the wireless network system, the transmitting wireless station of the second wireless communication system receives a control signal from the transmitting wireless station of the first wireless communication system and receives the second wireless communication system. When the data length transmitted from the transmission side radio station of the communication system is longer than the data length from the transmission side radio station of the first radio communication system, the adaptive control method is used based on the received control signal. The directivity pattern of data transmission is controlled so as to form a null for the transmitting side radio station of the first radio communication system.

Still further, in the control method of the wireless network system, the receiving radio station of the second radio communication system receives the control signal when receiving a control signal from the transmitting radio station of the first radio communication system. Based on the control signal, a directivity pattern of data reception is controlled using an adaptive control method so as to form a null for the transmitting-side radio station of the first radio communication system.

In the wireless network system control method, the receiving wireless station of the second wireless communication system receives a control signal from the receiving wireless station of the first wireless communication system and receives the second wireless communication system. When the data length transmitted from the transmission side radio station of the communication system is longer than the data length from the transmission side radio station of the first radio communication system, the adaptive control method is used based on the received control signal. The directivity pattern of data reception is controlled so as to form a null for the receiving radio station of the first radio communication system.

  Further, in the wireless network system, when the transmitting wireless station of the second wireless communication system receives a control signal from the first wireless communication system, whether or not to start data transmission according to predetermined access control It is characterized by determining.

According to the wireless network system and the control method thereof according to the present invention, timing synchronization can be easily obtained as compared with the prior art, and wireless communication at the wireless station of the second wireless communication system can be enabled. . In particular, it has the following specific effects.
(1) The reception timing synchronization in the receiving radio station of the second radio communication system can be easily realized. That is, the second wireless communication system observes frame transmission of the first wireless communication system, predicts the data transmission start timing, and matches the data transmission start timing of the second wireless communication system to match the second wireless communication system. The arrival timing of the desired signal can be predicted at the receiving radio station of the system.
(2) In addition, it is possible to estimate a propagation path condition between the first and second radio communication systems by allowing the transmitting radio station of the second radio communication system to observe the prior communication of the first radio communication system. Therefore, the interference is spatially suppressed using the estimated propagation path information. That is, the processing at the transmitting-side radio station of the second radio communication system is in the order of observation of prior communication → propagation path state estimation → interference suppression.
(3) Further, the reception side radio station of the second radio communication system observes the prior communication of the first radio communication system, so that it is possible to estimate the propagation path condition between the first and second radio communication systems. Therefore, interference is spatially suppressed using the estimated propagation path information. That is, the processing at the receiving radio station of the second radio communication system is in the order of prior communication observation → channel state estimation → interference suppression.
(4) Still further, in the access control in the second wireless communication system, the second wireless communication system is configured such that the condition satisfying the condition for enabling the superimposed transmission of the second wireless communication system is set as the minimum unit of access control. Enables access control within the communication system.

It is a block diagram which shows the structure of the radio | wireless communication network which concerns on embodiment of this invention. It is a block diagram which shows the structure of each radio station 2-1 and 2-2 of FIG. It is a timing chart which shows the example in which the synchronous acquisition in the receiving side radio station of a secondary system is possible in the radio | wireless communication network which concerns on a prior art. It is a timing chart which shows the example in which the synchronization acquisition in the receiving side radio station of a secondary system is impossible in the radio | wireless communication network which concerns on a prior art. 2 is a timing chart showing a frame exchange flow between a wireless LAN system 101 and a secondary system 102 in the wireless communication network of FIG. 1. FIG. 2 is a flowchart showing a first part of communication processing of a transmitting side radio station 2 and a receiving side radio station 2 in the secondary system 102 of FIG. 1. FIG. 7 is a flowchart showing a second part of communication processing between the transmitting-side radio station 2 and the receiving-side radio station 2 in the secondary system 102 of FIG. 1. It is a timing chart which shows the timing synchronous process by the mutual synchronization which concerns on this embodiment. FIG. 3 is a block diagram illustrating a configuration of a reception directivity control circuit 14 of the reception-side radio station 2 in FIG. 2. FIG. 3 is a block diagram illustrating a configuration of a transmission directivity control circuit 18 of the reception-side radio station 2 in FIG. 2. FIG. 2 is a plan view showing an arrangement of wireless stations and a direct wave arrival angle model in the wireless communication network of FIG. 1. It is a figure which shows the delay profile in the simulation performed using the radio | wireless communication network of embodiment. FIG. 6 is a result of a simulation performed using the wireless communication network according to the embodiment, in which the signal-to-noise power ratio ( 2 is a table showing SNR) and signal-to-interference power ratio (SIR). It is the result of the simulation performed using the radio | wireless communication network of embodiment, Comprising: It is a graph which shows the frame error rate FER with respect to transmission power ratio when the number of antenna elements M = 2. It is the result of the simulation performed using the radio | wireless communication network of embodiment, Comprising: It is a graph which shows the frame error rate FER with respect to transmission power ratio when the number of antenna elements M = 3. It is the result of the simulation performed using the radio | wireless communication network of embodiment, Comprising: It is a graph which shows the frame error rate FER with respect to transmission power ratio when the number of antenna elements M = 4.

1, 1-1, 1-2, 1-3, 2, 2-1, 2-2 ... wireless station,
1a: antenna element,
10-0 to 10- (M-1) ... antenna element,
11-0 to 11- (M-1) ... switch,
12-0 to 12- (M-1) ... low noise amplifier,
13-0 to 13- (M-1) ... power amplifier,
14: Reception directivity control circuit,
15 ... wireless receiver circuit,
16: Signal processing circuit,
17 ... wireless transmission circuit,
18: Transmission directivity control circuit,
20 ... Controller,
21-0-1 to 21- (M-1)-(Lp-1) ... delay circuit,
22-0-0 to 22- (M−1) − (Lp−1)... Multiplier
23-0-1 to 23- (M-1)-(Lp-1) ... adder,
24 ... adder,
25. Distributor,
26-0-1 to 26- (M-1)-(Lp-1) ... delay circuit,
27-0-0 to 27- (M-1)-(Lp-1) ... multiplier
28-0-1 to 28- (M-1)-(Lp-1) ... adder,
100: Cover area where mutual radio waves reach,
101 ... Wireless LAN system,
102 ... Secondary system,
200: Array antenna.

  Hereinafter, embodiments according to the present invention will be described with reference to the drawings. In addition, in each following embodiment, the same code | symbol is attached | subjected about the same component.

  FIG. 1 is a block diagram showing a configuration of a radio communication network according to an embodiment of the present invention, and FIG. 2 is a block diagram showing a configuration of each radio station 2-1 and 2-2 in FIG.

  In the embodiment according to the present invention, in order to solve the above-mentioned problems of the prior art, a superposition transmission method for solving the reception timing synchronization problem of the secondary system is examined. Specifically, as shown in FIG. 1, for example, a wireless LAN system 101 including a plurality of wireless stations 1-1 to 1-3 (generally referred to as reference numeral 1) each having a single antenna element 1a. Is an array antenna 200 (a plurality of M antenna elements 10-1 to 10-) that are located in the cover area 100 where radio waves can reach each other and can change the directivity, for example. (M-1)) and a plurality of wireless stations 2-1 to 2-2 (generally referred to by reference numeral 2), and the operating frequency band of the wireless LAN system 101 (that is, the same) We propose a new secondary system 102 that uses the operating frequency secondarily. The proposed wireless communication network is characterized by facilitating acquisition of timing synchronization at the receiver of the secondary system 102 by determining the transmission timing on the secondary system 102 side in consideration of the IEEE 802.11 protocol. Also, it is possible to improve the timing synchronization system and realize superimposition communication by calculating the weight of the adaptive array that suppresses the interfered / interfered signal when exchanging RTS / CTS signals, and forming the transmit / receive beam during DATA transmission. It is said.

In FIG. 2, each radio station 2 of the secondary system 102 is configured to include the following components.
(1) An array antenna 200 composed of a plurality of M antenna elements 10-0 to 10- (M-1) (for example, a variable directional antenna such as an ESPAR antenna may be provided instead of the array antenna 200). );
(2) Transmission / reception selector switches 11-0 to 11- (M-1) controlled by the controller 20;
(3) Low noise amplifiers 12-0 to 12- (M-1);
(4) Power amplifiers 13-0 to 13- (M-1);
(5) A reception directivity control circuit 14 that is controlled by the controller 20 and controls the directivity pattern of the array antenna 200 when receiving a reception signal;
(6) a wireless reception circuit 15 including a down converter and a demodulator;
(7) RTS / CTS / DATA _W / ACK signals are generated in the wireless LAN mode, and these signals are detected (note that these signals are also detected in the secondary system mode). A signal processing circuit 16 for generating a DATA _S signal and detecting the signal in order to execute the communication processing of FIGS. 6 and 7 in the mode;
(8) a wireless transmission circuit 17 including a modulator and an up-converter;
(9) a transmission directivity control circuit 18 which is controlled by the controller 20 and controls the directivity pattern of the array antenna 200 at the time of transmission of a transmission signal; and (10) wireless by executing the communication processing of FIG. 6 and FIG. A controller 20 that controls each component of the station 2.

Each wireless station 1 of the wireless LAN system 101 may have the same configuration as the wireless station 2 or may not have the array antenna 200 but may have only a single antenna element 1a. In this case, the reception directivity control circuit 14 and the transmission directivity control circuit 18 are not provided. Further, the signal processing circuit 16 of the wireless station 1 may have only a function of generating RTS / CTS / DATA _W / ACK signals and detecting these signals.

  In the radio station 2 of FIG. 2, the signal generated by the signal processing circuit 16 is modulated and up-converted by the radio transmission circuit 17, and then the transmission directivity control circuit 18, power amplifiers 13-0 to 13- (M− 1) The data is transmitted to the counterpart radio station via the contact b side of the transmission / reception change-over switches 11-0 to 11- (M-1) and the antenna elements 10-0 to 10- (M-1). On the other hand, the received signals received by the antenna elements 10-0 to 10- (M-1) are transmitted to the contact a side of the transmission / reception selector switches 11-0 to 11- (M-1), and the low noise amplifiers 12-0 to 12-12. -(M-1) and the reception directivity control circuit 14 are input to the radio reception circuit 15, the received signal is down-converted and demodulated, and then the demodulated signal is input to the signal processing circuit 16 to obtain a predetermined value. Signal processing is performed.

  Next, a method and operation procedure for easily realizing timing synchronization in the secondary system 102 that performs superimposed transmission to the wireless LAN system 101 will be described.

  When starting communication of the secondary system 102, it is important to avoid a decrease in transmission opportunities due to obstructing the progress of the back-off processing of the wireless LAN system 101 of the primary system and to sufficiently reduce the influence of interference. is there. Therefore, the secondary system 102 according to the present embodiment refrains from data transmission when exchanging the RTS / CTS signal of the wireless LAN system 101, and superimposes its own frame transmission on the DATA signal frame transmission of the wireless LAN system 101. At that time, the signal is separated on the space axis by weight control of the adaptive array, and the interference and the interference are suppressed.

FIG. 5 is a timing chart showing a frame exchange flow between the wireless LAN system 101 and the secondary system 102 in the wireless communication network of FIG. 6 and 7 are flowcharts showing communication processing (communication procedure) of the transmitting-side radio station 2 and the receiving-side radio station 2 in the secondary system 102 of FIG. Here, the transmitting-side wireless station 1-1 and the receiving-side wireless station 1-2 in the wireless LAN system 101 represent terminals that transmit and receive DATA _W frames, respectively. The DATA _W frame is a DATA frame transmitted from the transmission-side wireless station 1-1 of the wireless LAN system 101, and the DATA _S frame is a DATA frame transmitted from the transmission-side wireless station 2-1 of the secondary system 102. is there. Further, NAV (RTS) is a collision prevention packet transmission prohibition period based on the scheduled use period in the Duration / ID field of the RTS signal, and NAV (CTS) is a collision prevention based on the scheduled use period in the Duration field of the CTS signal. Packet transmission prohibited period. Also, SIFS (Short Inter Frame Space) is a short frame interval used in radio channel access control using a CSMA / CA (Carrier Sense Multiple Access with Collision Avoidance) system defined in IEEE 802.11. In the communication processing of FIGS. 5 to 7, for convenience of explanation, reference numerals are given to the radio stations, but each radio station can be a transmission side or a reception side.

In FIG. 6, the transmitting-side radio station 2-1 of the secondary system 102 according to the present embodiment starts RSSI measurement in response to a transmission request (S1). If no signal level exceeding the carrier sense threshold Pth is detected within the RSSI measurement time Tcs (NO in S2 and YES in S3), the target band is regarded as an empty band and DATA _S frame transmission is started (S4). . On the other hand, when the RSSI measurement value exceeds the threshold value Pth (YES in S2), signal reception processing is started (S5).

When the received signal is an RTS frame (YES in S6), calculation of a weight for forming a null (minimum value in the directivity pattern, the same applies hereinafter) for the transmitting wireless station 1-1 of the wireless LAN system 101. And CTS / DATA _W / ACK frame transmission start / end timing prediction (S8; phase A in FIG. 6). If the received signal is a CTS frame (YES in S7 and YES in S9), the calculation of the weight for forming a null for the receiving side wireless station 1-2 of the wireless LAN system 101 and the start of transmission of the DATA _W / ACK frame The end timing is predicted (S10; phase B in FIG. 6). If the received signal is not the RTS / CTS frame of the wireless LAN system 101 (NO in S6 and NO in S7), the RSSI measurement is resumed (S1). If the CTS frame has been successfully received (YES in S9), the process proceeds to step S11 in FIG. 7 to determine whether or not to start the DATA _S frame transmission according to access control such as random backoff. If the transmission of the DATA _S frame can be started (YES in S11), a null is formed for the receiving side radio station 1-2 of the wireless LAN system 101 (S12), and the transmission of the DATA _S frame is started (S13; FIG. 7). Phase C). The details of the transmission beam forming will be described later. On the other hand, if CTS frame reception fails or transmission is not performed due to access control (NO in S11), RSSI measurement is resumed (S1).

The transmission DATA _S frame length is set within a range not exceeding the predicted DATA _W frame length. However, if the RTS frame is successfully received, null formation can be performed for the transmitting-side wireless station 1-1 of the wireless LAN system 101, so that interference can be avoided even during ACK frame transmission. That is, it is possible to transmit a DATA _S frame exceeding the DATA _W frame length. Therefore, if necessary, the DATA _S frame length is set within a range not exceeding the prediction end timing of the ACK frame. In this case (YES in S14), the weight is switched to a weight that forms null for the receiving wireless station 1-2 of the wireless LAN system 101 in synchronization with the prediction end timing of the DATA _W frame (S15; phase D in FIG. 7). After the transmission of the DATA _S frame (S4), RSSI measurement is resumed (S1).

In FIG. 6, the receiving side radio station 2-2 of the secondary system 102 continuously performs RSSI measurement (S21), and if a signal level exceeding the threshold value Pth is detected (YES in S22), signal reception is performed. The process is started (S23). If the received signal is an RTS frame (YES in S24), the calculation of the weight for forming a null for the transmitting side wireless station 1-1 of the wireless LAN system 101 and the prediction of the transmission start / end timing of the CTS / DATA _W / ACK frame (S27; phase A in FIG. 6). When the received signal is a CTS frame (YES in S25 and YES in S28), a calculation of a weight for forming a null for the receiving-side wireless station 1-2 of the wireless LAN system 101 and transmission start / end timing of the DATA _W / ACK frame (S29; phase B in FIG. 6). Then, the process proceeds to step S31 in FIG.

On the other hand, if the received signal is a DATA _S frame (YES in S26 in FIG. 6), after reception timing synchronization processing (S33 in FIG. 7), a reception beam is formed and reception is started (S34; phase C in FIG. 7). Details of reception beam forming will be described later. Here, when the RTS frame is successfully received (YES in S31), a null is formed for the transmission-side wireless station 1-1 of the wireless LAN system 101, and reception timing synchronization processing is performed after suppressing interference (S33). ). This can be expected to improve the synchronization acquisition performance. When receiving a DATA _S frame exceeding the DATA _W frame length (YES in S35), if the CTS frame has been successfully received in advance (YES in S36), wireless communication is performed in accordance with the predicted end timing of the DATA _W frame. The receiving side wireless station 1-2 of the LAN system 101 is switched to a weight that forms a null (S37). Next, the reception beam is updated for the desired signal, and the DATA _S frame reception is resumed (S38; phase D in FIG. 7). After receiving the DATA _S frame, RSSI measurement is resumed (S21).

  Next, a timing synchronization method according to the present embodiment will be described below.

In the Duration / ID field of the wireless LAN frame of IEEE 802.11, the occupation time of the wireless channel is described (for example, refer to Non-Patent Document 5). The transmission / reception radio stations 2-1 and 2-2 of the secondary system 102 according to the present embodiment detect the RTS / CTS signal of the wireless LAN system 101 and demodulate the Duration / ID field to approximate the DATA _W frame. Get the transmission timing and its end timing. In addition, CTS and DATA _W frames are determined to start transmission after a short frame interval SIFS (Short Inter Frame Space) after transmission of RTS and CTS frames, respectively (see, for example, Non-Patent Document 5). It is possible to predict these timings.

In the method according to the present embodiment, its own DATA _S frame is transmitted in accordance with the predicted transmission timing of the DATA _W frame of the wireless LAN system 101. The reception-side radio station 2-1 of the secondary system 102 considers propagation delay and transmission timing error, sets a time window for detecting the arrival timing of the received signal so as to include the margin period of the predicted transmission timing, and Timing synchronization processing is started by calculating a cross-correlation value with a received preamble while shifting a known reference preamble during a time window. It is possible to secure the maximum transmission time of the DATA _S frame in the secondary system 102 by matching the DATA _S frame transmission timing of the secondary system 102 with the DATA _W frame predicted transmission timing of the wireless LAN system 101. is there. That is, both the wireless LAN system 101 and the secondary system 102 have a preamble at the head of the frame. The wireless station 2 of the secondary system 102 is known for both the wireless LAN system 101 and the preamble of the secondary system 102. When receiving the RTS / CTS frame, timing synchronization is performed using the preamble of the wireless LAN system 101. Further, when receiving a DATAs frame (data of the secondary system 102 itself), timing synchronization processing is performed with a known preamble arranged at the head of the DATAs frame. Since the DATAs frame is transmitted in synchronization with the transmission start timing of the DATAw frame of the primary system at the transmitting side radio station 2-1 of the secondary system 102, the DATAs frame is received at the receiving side radio station 2-2 of the secondary system 102. Can be predicted, and the synchronization process may be performed on the DATAs frame.

FIG. 8 is a timing chart showing the timing synchronization processing by mutual synchronization according to the present embodiment, that is, the assumed timing synchronization processing. T _s in the drawing synchronization point search start timing in consideration of the transmission timing error, T _w denotes the width of the time window in consideration of the propagation delay. Timing synchronization is a mutual relationship between a reference signal (preamble) that is a data pattern that is known in advance to be transmitted from the radio station 2 of the secondary system 102 and a received signal (preamble) that is actually received from the radio station 2. The correlation value is calculated, and the timing synchronization point and the delay wave arrival timing are estimated by detecting the peak value of the cross-correlation value.

  Further, interference suppression and interference suppression will be described below.

The transmission / reception radio stations 2-1 and 2-2 of the secondary system 102 estimate the propagation path response between the transmission / reception radio stations 1-1 and 1-2 of the wireless LAN system 101 when the RTS / CTS frame is received. A weight with a null constraint is obtained for the propagation path response. Then, when transmitting and receiving the DATA _S frame, the respective weights are applied to suppress interference and interference. Hereinafter, a specific method will be described.

Generation of transmission weights and reception weights will be described below. In the transmission-side radio station 2-1 of the secondary system 102, a tapped delay line adaptive array antenna (TDL-AAA) is used to suppress delay waves exceeding the degree of freedom of the array in broadband transmission. TDL-AAA ”is used (for example, see Non-Patent Document 7). When the RTS / CTS signal frame is received, the channel response between the transmitting and receiving radio stations 1-1 and 1-2 of the wireless LAN system 101 is estimated, and a weight with a null constraint is obtained for the estimated channel response. During transmission of the DATA _S frame, interference with the wireless LAN system 101 is avoided by transmission TDL-AAA based on this weight.

9 is a block diagram showing the configuration of the reception directivity control circuit 14 of the reception-side radio station 2 in FIG. 2, and FIG. 10 is a block diagram showing the configuration of the transmission directivity control circuit 18 of the reception-side radio station 2 in FIG. FIG. FIG. 9 and FIG. 10 show configurations of reception TDL-AAA and transmission TDL-AAA, respectively. Here, M is the number of antenna elements, Lp is the number of branches of each TDL, T is the sampling interval, z _{Tx, m} (t) is an input signal to the m-th antenna element 10-m, and s (t) is DATA. _{The S} frame signal, w _{Tx, m, l} represents the weight in the lth branch of the mth antenna element 10-m. However, it is assumed the time delay tau _l is τ ₀ (= ₀₎ at an integer multiple of the sample interval _{T ≦ τ 1 ≦ ... ≦ τ} Lp-1 and.

  In FIG. 9, the reception directivity control circuit 14 has a so-called transversal filter configuration, and a plurality of (Lp-1) delay circuits 21-0-1 to 21 that are cascade-connected to each other by the antenna elements and delay received signals. 21- (M-1)-(Lp-1) and each delay circuit 21-0-1 to 21- (M-1)-(Lp-1) are connected to the input / output terminals and weights are assigned to the respective delay signals. Each of the multipliers 22-0-0 to 22- (M-1)-(Lp-1) to be multiplied and the multipliers 22-0-0 to 22- (M-1)-(Lp-1) Adders 23-0-1 to 23- (M-1)-(Lp-1) for adding signals and an adder 24 for adding all the received signals and outputting the received signal y (t). Configured.

  In FIG. 10, the transmission directivity control circuit 18 has a configuration opposite to that of the reception directivity control circuit 14, and is connected in cascade with each other by a distributor 25 that distributes the transmission signal s (t) to M and each antenna element. Delay circuits 26-0-1 to 26- (M-1)-(Lp-1) for delaying the respective distributed transmission signals, and multipliers 27-0-0 to 27 for multiplying the transmission signals of the respective antenna elements by weights. -(M-1)-(Lp-1), signals from the multipliers 27-0-0 to 27- (M-1)-(Lp-1), and delay circuits 26-0-1 to 26-0-1. 26- (M-1)-(Lp-1) includes adders 28-0-1 to 28- (M-1)-(Lp-1) that add empty signals.

  In FIG. 9, the output signal from the reception directivity control circuit 14 is expressed by the following equation.

  The optimal weight for performing null constraint on the channel response between the transmission-side radio station 2-1 of the secondary system 102 and the transmission / reception radio stations 1-1 and 1-2 of the wireless LAN system 101 is directional constraint. It is calculated by the following equation using an output power minimization method (DCMP: Directionally Constrained Minimization of Power; hereinafter referred to as DCMP method) (for example, see Non-Patent Document 6).

The transmission optimum weight W _{TX, opt} that satisfies the equation (2) is expressed by the following equation.

Here, R _Tx , w _Tx , C _A, and q represent the correlation matrix, weight, constraint matrix, and constraint response vector of the input signal z _Tx (t), respectively, and are expressed by the following equations.

[Equation 1]
R _Tx = E [z _Tx (t) z ^H _Tx (t)] (4)
[Equation 2]
z ^T _Tx (t) = [z ′ ^T _Tx (t)... z ′ ^T _Tx (t−τ _Lp−1 )] (5)
[Equation 3]
z ′ _Tx (t) = [z _{Tx, 0} (t)... z _Tx , _M−1 (t)] ^T (6)
[Equation 4]
^{_{w T Tx = [w T Tx}} , 0 ... w T Tx, Lp-1] (7)
[Equation 5]
_{wTx, l} = [ _{wTx, 0, l} ... _{wTx, M-1, l} ] ^T (8)
[Equation 6]
C _A = [p _Tx d] (9)
[Equation 7]
q = [0 1] ^T (10)

Here, E [•] represents an ensemble average, H represents a complex conjugate transpose, and T and * represent transpose and complex conjugate, respectively. Note that p _Tx = E [z _Tx (t) d ^* _ref (t)] is a correlation vector between z _Tx (t) and the reference signal d _ref (t), and d _ref (t) is a wireless LAN. The preamble waveform of the system 101 is assumed. In the present embodiment, the transmission-side radio station 2-1 of the secondary system 102 sets propagation path response information in its own system to be unknown, and d = [1... 1] ^T. However, when the channel response information from the receiving side is obtained in advance, the received signal-to-noise power ratio (SNR) can be improved by setting d to the channel response in the desired signal.

Next, reception weight generation will be described below. The receiving side radio station 2-2 of the secondary system 102 uses two types of TDL-AAA weights. First, in order to improve the path detection accuracy of the desired wave, a null-constrained weight for suppressing interference is generated by the same processing as that on the transmission side. Then, path detection of the desired signal is performed on the synthesized signal based on the weight. Next, in order to improve demodulation accuracy, a TDL-AAA tap position is determined based on the path detection result, and an MMSE weight is generated. The path detection weight is obtained by the DCMP method in the same manner as the transmission side when the RTS / CTS frame is received. The reception optimum weight W _{Rx, opt} is expressed by the following equation.

Here, R _Rx = E [z _Rx (t) z ^H _Rx (t)] is a correlation matrix of the input signal z _Rx (t), C _B = [p _Rx d] is a constraint matrix, and p _Rx = E [z _Rx (t) d ^* _ref (t)] represents a correlation vector. When path detection is performed on the combined signal based on the weight obtained by the above equation, interference detection is suppressed, so that improvement in path detection accuracy can be expected.

After the path is detected, the preamble signal arranged at the head of the DATA _S frame is used, and the weight control of the reception directivity control circuit 14 (reception TDL-AAA) is performed so that the reception SINR of the desired signal is improved. Specifically, the optimum weight is obtained based on the following MMSE (Minimum Mean Square Error) standard that minimizes the mean square error between the output signal from the reception directivity control circuit 14 and the preamble signal d _tr (t). (For example, refer nonpatent literature 6.).

However, z _{Rx, D} (t) is an input signal to the reception directivity control circuit 14 (reception TDL-AAA) when the DATA _S frame is received. Accordingly, the reception optimum weights W _{Rx, MMSE, and opt} are expressed by the following equations.

Here, R _{Rx, D} = E [z _{Rx, D} (t) z ^H _{Rx, D} (t)] is the correlation matrix of the input signal z _{Rx, D} (t), p _{Rx, D} = E [z _{Rx, D} (t) d ^* _tr (t)] represents a correlation vector.

  On the other hand, when the RTS frame reception fails, path detection is performed using the received signal at any of the reference antenna elements. Based on the detection result, weight control of the reception directivity control circuit 14 (reception TDL-AAA) is performed using the above MMSE norm to suppress interference.

In addition, when receiving a DATA _S frame exceeding the DATA _W frame length, if the reception of the CTS frame that has just arrived is successful, the initial state is to suppress interference caused by the ACK frame of the wireless LAN system 101. After setting the weight, the reception beam forming weight is updated in accordance with the DATA _W frame prediction end timing, and the DATA _S frame reception is resumed. On the other hand, if the CTS frame reception fails, the reception beam forming weight is updated with respect to the desired signal without resetting the weight, and the DATA _S frame reception is resumed.

  In the above embodiment, as shown in FIG. 2, FIG. 9, and FIG. 10, the transmission directivity and the reception directivity are controlled in the radio frequency band, but the present invention is not limited to this, and the intermediate frequency band or You may comprise so that transmission directivity and reception directivity may be controlled in a baseband.

  Next, the present inventors will explain the results of computer simulation using the wireless communication network system of FIG.

FIG. 11 is a plan view showing an arrangement of wireless stations and a direct wave arrival angle model in the wireless communication network of FIG. In FIG. 11, the topology of each wireless station arrangement is a square, and the routes of the wireless LAN system 101 and the secondary system 102 intersect each other. Here, phi _x represents the broadside direction of the adaptive array radio station x, the angle which the straight line forms connecting radio station 21 and the radio station 2-2. phi _A and phi _B gave randomly to 0 to 180 degrees for each run.

  FIG. 12 is a diagram illustrating a delay profile in a simulation performed using the wireless communication network of the embodiment. The propagation path model is assumed to be a 5-wave model (L = 5) shown in FIG. 12, and the preceding wave is assumed to be a direct wave only and the delayed wave is subjected to Rayleigh fading. Further, it was assumed that the propagation loss is a square law and the inter-antenna fading correlation of the delayed wave is uncorrelated.

  The TDL branch number Lp is set to Lp = L in weight generation by the DCMP method for suppressing interference and interference between the wireless LAN system 101 and the secondary system 102. Further, Lp = 2 × L−1 is set in the weight generation according to the MMSE norm in receiving the desired wave. This is because the apparent propagation path response to the desired signal is a convolution of the impulse response of the transmission directivity control circuit 18 (transmission TDL-AAA) and the actual propagation path response. Tables 1 and 2 show simulation specifications for characteristic evaluation in the simulation performed using the wireless communication network of the embodiment.

[Table 1]
Specifications of wireless LAN system 101 ―――――――――――――――――――――――――――――――――――――――
Sampling rate 20MHz
Modulation method 16QAM-OFDM
Number of subcarriers 52 (data: 48, pilot: 4)
FFT points 64
Effective symbol period 3.2 μsec (64 samples)
Guard period l0.8μsec (16 samples)
Channel coding Convolutional code (rate: 1/2, constraint length: 7)
Channel decoding Hard input Viterbi algorithm Interleaver type Block interleaver (depth: 12 x 16)
Payload length 1000 bytes Number of antenna elements 1
―――――――――――――――――――――――――――――――――――――――

[Table 2]
Specifications of the secondary system 102 ―――――――――――――――――――――――――――――――――――――――
Sampling rate 20MHz
Modulation method π / 4-DQPSK DS-SS
Spreading code M-sequence code length 63 (training), 15 (data)
Number of training symbols 3
Channel coding Convolutional code (rate: 1/2, constraint length: 7)
Channel decoding Hard input Viterbi algorithm Interleaver type Block interleaver (depth: 4x2)
Payload length 60 byte array antenna configuration Number of linear array antenna elements 2-4
Antenna spacing Half wavelength ―――――――――――――――――――――――――――――――――――――――

  The parameters of the wireless LAN system 101 are assumed to conform to the IEEE802.11a standard (for example, refer to Non-Patent Document 5). In the standard, the interval from the end timing of the last symbol in the preceding frame to the transmission timing of the first symbol in the preamble of the next frame is defined as a short frame interval (SIFS), and the allowable transmission timing error is set to 10% or less of the contention slot length. Yes. In this simulation, considering the allowable timing error, ts = −18 samples from the predicted arrival timing, and the time window Tw = (18 × 2) samples + Lp samples of the synchronization process.

The frame of the secondary system 102 is composed of a leading preamble and information data, and the preamble includes three M-sequences of period 63 for synchronization acquisition, delay wave detection, and reception weight control. Further, the information data uses an M-sequence with a period of 15 as a spreading code. The reference signal d _tr (t) uses 189 samples of the preamble, and the reference signal d _ref (t) uses 128 samples of the long preamble section of the wireless LAN system 101 excluding the guard interval.

The payload length is set to 60 bytes so that the DATA _S frame length of the secondary system 102 is temporally shorter than the DATA _W frame of the wireless LAN system 101. This assumes transmission of control information. The transmission side wireless station 2-1 of the secondary system 102 obtains the weight of the transmission directivity control circuit 18 (transmission TDL-AAA) when the wireless LAN system 101 receives the CTS frame. Then, the reception side radio station 2-2 of the secondary system 102 obtains the weight of the reception directivity control circuit 14 (reception TDL-AAA) for path detection when the wireless LAN system 101 receives the RTS frame. A known SMI (Sample Matrix Inversion) algorithm was used for weight generation of the MMSE norm for demodulation.

  Next, simulation results will be described below.

FIG. 13 shows the result of simulation performed using the wireless communication network of the embodiment. Signal-to-noise at the reception-side wireless station 1-2 of the wireless LAN system 101 and the reception-side wireless station 2-2 of the secondary system 102 It is a table | surface which shows power ratio (SNR) and signal-to-interference power ratio (SIR). That is, in FIG. 13, the ratio between the transmission power P _{Tx, W} of the wireless LAN system 101 and the transmission power P _{Tx, S} of the secondary system 102 (Transmission Power Ratio: TPR = P _{Tx, W} / P _{Tx, S} ), wireless The relationship between the signal-to-noise power ratio (SNR) and the signal-to-interference power ratio (SIR) in the receiving-side radio station 2-2 of the LAN system 101 and the secondary system 102 is shown. Here, the SNR and SIR at the receiving-side radio station 2-2 of the secondary system 102 were calculated based on the average signal power after despreading per receiving antenna.

  The number of array elements of the transmitting and receiving side radio station 2 of the secondary system 102 is the same, and the average frame error rate (Frame Error Rate: FER) with respect to the TPR of the wireless LAN system 101 and the secondary system 102 in the number of elements M = 2, 3 and 4. ) The characteristics are shown in FIGS. 14, 15 and 16, respectively. When superimposing transmission is performed under the conditions shown in Table 2, the wireless LAN (WLAN with secondary) is greatly degraded in the low TPR region as compared with the case where superimposing transmission is not performed (WLAN with secondary), but as the TPR increases. It can be seen that interference can be avoided. In addition, when the number of array elements M = 2, the FER characteristics of the wireless LAN system 101 are greatly deteriorated in the low TPR region as compared with the case of M = 3. However, when M = 3 and M = 4, they are approximately the same. This shows the effect of suppressing interference.

  The secondary system 102 (Secondary with WLAN) achieves an average FER = 1% at about TPR = −3 dB when the number of array elements M = 2. However, the interference with the wireless LAN system 101 is large, and the average FER of the wireless LAN system 101 shows a significant deterioration. On the other hand, when M = 3, TPR = 6 dB, and when M = 4, the average FER = 1% is achieved at about TPR = 10 dB, and the influence of interference on the wireless LAN system 101 can be sufficiently suppressed. ing. From the above results, it can be seen that the secondary system 102 can communicate with the average FER = 1% or less while avoiding interference with the wireless LAN system 101 by using an array element of M = 3 or more.

  As described above, according to the present embodiment, as a solution to the reception timing synchronization problem of the secondary system 102 in the superimposed transmission, the superimposed transmission method that easily realizes the timing synchronization processing considering the protocol of the wireless LAN system 101. Devised. Furthermore, as a countermeasure for delayed waves in wideband transmission, verification of interference suppression and interference suppression methods by transmission / reception TDL-AAA was performed. As a result of the evaluation by computer simulation, the influence of the interference on the wireless LAN system 101 can be sufficiently avoided by the appropriate number of transmission adaptive array elements and transmission power. Further, it is considered that the interference from the wireless LAN system 101 can be suppressed by using the space-time signal processing by TDL-AAA even when the transmission power of the secondary system 102 is limited.

Modification of communication processing of secondary system 102.
In the communication processing according to the embodiment shown in FIGS. 7 and 8, when the CTS frame reception fails (NO in S7 of FIG. 7), the RSSI measurement (S1) is resumed without performing the superimposed transmission (FIG. 7). 7 Phase B). However, even when CTS frame reception has failed (DATA demodulation has failed) by the method described below, superimposed transmission can be started if null formation is possible for the receiving radio station 1-2.

(A) Communication processing of transmitting side radio station 2-1.
(1) The transmitting side radio station 2-1 of the secondary system 102 starts RSSI measurement in response to the transmission request. If no signal level exceeding the carrier sense threshold value Pth is detected within the RSSI measurement time Tcs, the target band is regarded as an empty band and DATA _S frame transmission is started. On the other hand, when the RSSI measurement value exceeds the threshold value Pth, signal reception processing and measurement of bandwidth and duration are started.
(2) Successful reception of RTS frame, or measurement result of bandwidth and duration When the arrival of RTS frame is estimated, calculation of weight for forming null for transmitting side radio station 1-1 of wireless LAN system 101 And CTS / DATA _W / ACK frame transmission start / end timing prediction (phase A in FIG. 6). In addition, when the reception of the CTS frame is successful or the arrival of the CTS frame is estimated as a result of the bandwidth and duration measurement, the calculation of the weight for forming a null for the receiving wireless station 1-2 of the wireless LAN system 101 and The transmission start / end timing of the DATA _W / ACK frame is predicted (phase B in FIG. 6). If the received signal is not an RTS / CTS frame of the wireless LAN system 101, RSSI measurement is resumed.
(3) When the reception of the CTS frame is successful or the reception of the RTS frame is successful and the arrival of the CTS frame is estimated, whether to start the transmission of the DATA _S frame is determined according to access control such as random backoff. When the transmission of the DATA _S frame can be started, a null is formed for the reception-side wireless station 1-2 of the wireless LAN system 101 and the transmission is started (phase C in FIG. 7). On the other hand, if the CTS frame reception failure or the arrival of the CTS frame is not estimated, or if transmission is not performed by access control, RSSI measurement is resumed.
(4) The transmission DATA _S frame length is set within a range not exceeding the predicted DATA _W frame length. However, if the RTS frame is successfully received, null formation can be performed for the transmitting-side wireless station 1-1 of the wireless LAN system 101, so that interference can be avoided even during ACK frame transmission. That is, it is possible to transmit a DATA _S frame exceeding the DATA _W frame length. Therefore, if necessary, the DATA _S frame length is set within a range not exceeding the prediction end timing of the ACK frame. In this case, in accordance with the DATA _W frame prediction end timing, the reception side wireless station 1-2 of the wireless LAN system 101 is switched to a weight that forms a null (phase D in FIG. 7). After the transmission of the DATA _S frame, RSSI measurement is resumed.

(B) Communication processing of receiving side radio station 2-2.
(1) The reception side (STA-B) of the secondary system 102 continuously performs RSSI measurement. When a signal level exceeding Pth is detected, signal reception processing and measurement of bandwidth and duration are started. .
(2) When the reception of the RTS frame is successful, or when the arrival of the RTS frame is estimated as a result of the measurement of the bandwidth and the duration, the weight for forming a null for the transmitting side radio station 1-1 of the wireless LAN system 101 Calculation and prediction of transmission start / end timing of CTS / DATA _W / ACK frame are performed (phase A in FIG. 6). If the reception of the CTS frame is successful, or if the arrival of the CTS frame is estimated as a result of the bandwidth and duration measurement, the weight calculation for forming a null for the receiving side radio station 1-2 of the wireless LAN system 101 and DATA _The start / end timing of transmission of the _W / ACK frame is predicted (phase B in FIG. 6).
(3) On the other hand, when the reception signal is a DATA _S frame, after reception timing synchronization processing, a reception beam is formed and reception is started (phase C in FIG. 7). Here, when the reception of the RTS frame is successful or the arrival of the RTS frame is estimated, a null is formed for the transmitting-side radio station 1-1 of the wireless LAN system 101, and the reception timing synchronization process is performed after suppressing interference. I do. This can be expected to improve the synchronization acquisition performance.
(4) When a DATA _S frame exceeding the DATA _W frame length is received, if the CTS frame is successfully received or the arrival of the CTS frame is estimated in advance, it is matched with the predicted end timing of the DATA _W frame. The receiving side wireless station 1-2 of the wireless LAN system 101 is switched to a weight that forms a null. Next, the reception beam is updated for the desired signal, and the DATA _S frame reception is resumed (phase D in FIG. 7).

As described above in detail, according to the radio network system and the control method thereof according to the present invention, timing synchronization can be easily obtained as compared with the prior art, and radio communication at a radio station of the second radio communication system. Can be made possible. In particular, it has the following specific effects.
(1) The reception timing synchronization in the receiving radio station of the second radio communication system can be easily realized. That is, the second wireless communication system observes frame transmission of the first wireless communication system, predicts the data transmission start timing, and matches the data transmission start timing of the second wireless communication system to match the second wireless communication system. The arrival timing of the desired signal can be predicted at the receiving radio station of the system.
(2) In addition, it is possible to estimate a propagation path condition between the first and second radio communication systems by allowing the transmitting radio station of the second radio communication system to observe the prior communication of the first radio communication system. Therefore, the interference is spatially suppressed using the estimated propagation path information. That is, the processing at the transmitting-side radio station of the second radio communication system is in the order of observation of prior communication → propagation path state estimation → interference suppression.
(3) Further, the reception side radio station of the second radio communication system observes the prior communication of the first radio communication system, so that it is possible to estimate the propagation path condition between the first and second radio communication systems. Therefore, interference is spatially suppressed using the estimated propagation path information. That is, the processing at the receiving radio station of the second radio communication system is in the order of prior communication observation → channel state estimation → interference suppression.
(4) Still further, in the access control in the second wireless communication system, the second wireless communication system is configured such that the condition satisfying the condition for enabling the superimposed transmission of the second wireless communication system is set as the minimum unit of access control. Enables access control within the communication system.

Claims (4)

A first wireless communication system configured with a plurality of wireless stations and performing data transmission after exchanging control signals;
A wireless network system including a second wireless communication system configured to include a plurality of wireless stations and performing data transmission using the same frequency band as that of the first wireless communication system and superimposed in time. And
The transmitting-side radio station of the second radio communication system receives the control signal of the first radio communication system, and predicts the data transmission timing of the first radio communication system based on the received control signal. And at the same time as the data transmission of the first wireless communication system at the predicted timing, the data to be transmitted is transmitted,
The receiving radio station of the second radio communication system receives the control signal of the first radio communication system, and predicts the timing of data transmission of the first radio communication system based on the received control signal. And receiving data from the transmitting wireless station of the second wireless communication system at the predicted timing ,
When the transmitting wireless station of the second wireless communication system receives a control signal from the receiving wireless station of the first wireless communication system, the transmitting wireless station uses an adaptive control method based on the received control signal. Control the directivity pattern of data transmission so as to form a null for the receiving radio station of the first radio communication system,
When the receiving radio station of the second radio communication system receives a control signal from the transmitting radio station of the first radio communication system, the receiving radio station uses an adaptive control method based on the received control signal. And a directivity pattern for data reception so as to form a null for the transmitting-side radio station of the first radio communication system. Data transmitted from the transmitting radio station of the second radio communication system and received from the transmitting radio station of the second radio communication system by the transmitting radio station of the second radio communication system When the length is longer than the data length from the transmitting wireless station of the first wireless communication system, the transmitting wireless station of the first wireless communication system using the adaptive control method based on the received control signal controlling the directivity pattern of the data transmission so as to form a null to,
The receiving-side radio station of the second radio communication system receives the control signal from the receiving-side radio station of the first radio communication system and transmits data from the transmitting-side radio station of the second radio communication system When the length is longer than the data length from the transmitting wireless station of the first wireless communication system, the receiving wireless station of the first wireless communication system using the adaptive control method based on the received control signal wireless network system according to claim 1, wherein the controlling the directivity pattern of the data received so as to form a null to. A first wireless communication system configured with a plurality of wireless stations and performing data transmission after exchanging control signals;
Control of a radio network system including a second radio communication system configured to include a plurality of radio stations and performing data transmission using the same frequency band as that of the first radio communication system and superimposed in time A method,
The transmitting-side radio station of the second radio communication system receives the control signal of the first radio communication system, and predicts the data transmission timing of the first radio communication system based on the received control signal. And at the same time as the data transmission of the first wireless communication system at the predicted timing, the data to be transmitted is transmitted,
The receiving radio station of the second radio communication system receives the control signal of the first radio communication system, and predicts the timing of data transmission of the first radio communication system based on the received control signal. And receiving data from the transmitting wireless station of the second wireless communication system at the predicted timing ,
When the transmitting wireless station of the second wireless communication system receives a control signal from the receiving wireless station of the first wireless communication system, the transmitting wireless station uses an adaptive control method based on the received control signal. Control the directivity pattern of data transmission so as to form a null for the receiving radio station of the first radio communication system,
When the receiving radio station of the second radio communication system receives a control signal from the transmitting radio station of the first radio communication system, the receiving radio station uses an adaptive control method based on the received control signal. A control method for a radio network system, comprising: controlling a directivity pattern of data reception so as to form a null for the transmitting radio station of the first radio communication system . Data transmitted from the transmitting radio station of the second radio communication system and received from the transmitting radio station of the second radio communication system by the transmitting radio station of the second radio communication system When the length is longer than the data length from the transmitting wireless station of the first wireless communication system, the transmitting wireless station of the first wireless communication system using the adaptive control method based on the received control signal controlling the directivity pattern of the data transmission so as to form a null to,
The receiving-side radio station of the second radio communication system receives the control signal from the receiving-side radio station of the first radio communication system and transmits data from the transmitting-side radio station of the second radio communication system When the length is longer than the data length from the transmitting wireless station of the first wireless communication system, the receiving wireless station of the first wireless communication system using the adaptive control method based on the received control signal 4. The method of controlling a wireless network system according to claim 3, wherein a directivity pattern for data reception is controlled so as to form a null .

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