JP2005064672A - Control method and control apparatus for wireless network - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a MAC protocol capable of suppressing interference from other stations and bringing efficiency to the SDMA in a multi-hop wireless network. <P>SOLUTION: A control method or a control apparatus is provided to the wireless network wherein a plurality of wireless stations each including an antenna capable of forming beams having both a sector pattern with a prescribed beam width and an omnidirectional beam pattern are provided and wireless communication is executed between a sender wireless station and a destination wireless station among the plurality of wireless stations. Each wireless station detects a wireless signal from a sender wireless station by using an omnidirectional or sector pattern, searching an azimuth angle at which a maximum signal strength is obtained by using the sector pattern to rotate a beam direction of the antenna over all azimuth angles and thereafter inhibiting wireless communication using the sector pattern to the azimuth angle of a wireless station when the detected wireless signal indicates that the wireless station is not the wireless station for the wireless communication. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a control method and a control apparatus for a wireless network such as an ad hoc wireless network that performs packet communication in a wireless network such as a wireless LAN including a plurality of wireless stations.

  With recent advances in wireless communication and personal computers, it was assumed that each node wireless station operates as a mobile station router device equipped with a wireless transceiver and is a network without infrastructure (base) that can be implemented at high speed. Ad hoc wireless networks are being studied.

  Usually, in an ad hoc wireless network, all node radio stations are equipped with omni-pattern antennas. However, an ad hoc wireless network equipped with an omni-pattern antenna secures a wireless medium over a wide area, thereby consuming a large part of the network capacity, RTS (Request To Send; Communication Start Control Signal) / CTS (Clear To Send; The floor securing method based on the communication acceptance signal) is used. As a result, many adjacent node radio stations in the vicinity of the transmitter and receiver must wait indefinitely for the end of data communication between the transmitter and the receiver. To alleviate this problem, researchers have proposed the use of directional (fixed or adaptively controlled) antennas that direct the transmit and receive beams only to the receive node radio station and the transmit node radio station. This significantly reduces radio interference, thereby improving the utilization of the radio medium and thus improving the network throughput (see Patent Documents 1 and 2 and Non-Patent Documents 1 to 11).

  Next, the research related to the present invention will be briefly described below. Despite the advantages of directional antennas, research into efficient MAC (Media Access Control) protocols that use directional antennas in wireless communication systems for ad hoc wireless networks has been focused on mobility in ad hoc wireless networks. Limited due to the inherent difficulties associated with responsiveness and distributed control. Some researchers have attempted to tackle this issue in several ways. Zander proposed the use of directional antennas in packet radio networks (see Non-Patent Document 1). Non-Patent Document 2 also proposes a MAC protocol using a directional antenna. In this case, each station is assigned a tone signal unique to the adjacent node radio station. When a station receives a packet, it immediately broadcasts its tone signal over a period of time so that its adjacent node radio station can identify its presence and avoid transmission in that direction Can do.

  Furthermore, in recent years, several MAC protocols that rely on RTS / CTS type handshake as defined in IEEE 802.11 have been proposed using directional antennas (see Non-Patent Documents 3 to 11). ). In Non-Patent Document 3, a combination of directivity / omnidirectional RTS / CTS is used to block transmission in a direction that interferes with existing data communication by the node radio station, while transmitting in the other direction. A D-MAC (Directive MAC) method has been proposed that enables this. In Non-Patent Document 4, a MAC protocol for establishing multi-hop efficiency is proposed using multi-hop RTS-single hop CTS using a directional antenna. In this mechanism, the use of a larger range of directional beams allows the destination to be reached with fewer hops than when using an omni-pattern antenna. In both methods of Non-Patent Documents 3 and 4, it is assumed that mobile node radio stations recognize the physical positions of their own and their neighboring node radio stations using GPS. However, due to the directional RTS / directional CTS method, the gain asymmetry and the problem of new hidden terminal due to unrecognized RTS / CTS, the problem of hearing loss and the more directional as described in Non-Patent Document 4. Some problems such as high quality interference remain unresolved.

  Furthermore, in Non-Patent Document 5, the proposed MAC protocol does not need to recognize location information, and the source radio station and the destination radio station are exchanged on the basis of on-demand RTS-CTS. Identify each other's direction. It is assumed that all neighboring node radio stations of the originating radio station Ns and the destination radio station Nd that heard this RTS-CTS dialog use this information to prevent interference with ongoing data transmission. However, due to the omnidirectional transmission of RTS and CTS packets, this protocol does not provide any benefit of spatial reuse of the radio channel. However, this protocol still improves the throughput over the MAC using the omni-pattern antenna by reducing the amount of interference generated due to directional data transmission (see Non-Patent Document 11).

  Also, in Non-Patent Document 6, Ramanathan investigated the performance of ad hoc wireless networks using beamforming antennas with changing antenna patterns and beam control, channel access mechanisms, link power control and discovery of adjacent node radio stations. Yes. Furthermore, in Non-Patent Document 7, the authors assume that the position information is pre-recognized, and one directional NAV (DNAV (Directional Network Allocation Vector) concept is used for each sector. Instead of having to postpone transmission until the simultaneous transmission on all sectors is secure, non-patent document 8 allows for the immediate transmission of control packets on a clear sector pattern. Proposed a DNAV method with a direction and width that is set depending on the signal strength of the direction, again using a smarter antenna and using multiple antennas due to its multipath component of one signal. Can be identified and used to block multiple DNAVs of different widths and azimuths.

  Developing an appropriate MAC protocol in an ad hoc wireless network to take advantage of directional antennas with the goal of improving overall performance requires proper location tracking and proximity recognition. Each node radio station must recognize a direction in which it can communicate directionally with an adjacent node radio station. This information makes it possible to select an azimuth or beamforming that ensures effective communication. At the same time, each node radio station must be aware of the current communication state in the shared neighborhood so that it can start communication in the other direction without interfering with existing communication. In addition, the propagation of this neighborhood information, including directional access information between each node radio station and each adjacent node radio station, is efficient and proactive because it facilitates the retention of proper network status information by the network. It is also useful for the design of routing protocols (innovative anticipation) (see Non-Patent Document 10).

JP 2001-024431A. Japanese Patent Laid-Open No. 2001-244983. J. Zander, “Slotted ALOHA multihop packet radio networks with directional antennas”, Electronic Letters ”, Vol. 26, No. 25, 1990. T. S. Yum et al., “Design algorithms for multihop packet radio networks with multiple directional antennas stations”, IEEE Transactions on Communications, Vol. 40, No. 11, pp. 1716-1724, 1992. Y. B. Ko et al., “Medium access control protocols using directional antennas in ad hoc networks”, Proceedings of the IEEE INFOCOM 2000, March 2000. Romit Roy Choudhury et al., “Using directional antennas for medium access control in ad hoc networks”, Proceedings of the eighth annual international conference on Mobile computing and networking, September 2002. Nasipuri, S. et al., “A MAC Protocol for Mobile Ad Hoc Networks Using Directional Antennas”, Proceedings of the IEEE WCNC 2000. R. Ramanathan, “On the Performance of Ad Hoc Networks with Beamforming Antennas”, ACM MobiHoc, October 2001. Kou Kobayashi et al., “Spatially divided channel scheme using sectored antennas for CSMA / CA-directional CSMA / CA”, Proceedings of PIMRC '2000, 2000. M. Takai et al., “Directional Virtual Carrier Sensing for Directional Antennas in Mobile Ad Hoc Networks”, ACM MobiHoc, June 2002. S. Bandyopadhyay et al., “An Adaptive MAC Protocol for Wireless Ad Hoc Community Network (WACNet) Using Electronically Steerable Passive Array Radiator Antenna”, Proceedings of the GLOBECOM 2001, November 25-29, 2001, San Antonio, Texas, USA. S. Bandyopadhyay et al., “An Adaptive MAC and Directional Routing Protocol for Ad Hoc Wireless Network Using Directional ESPAR Antenna”, Proceedings of the ACM Symposium on Mobile Ad Hoc Networking & Computing 2001 (MOBIHOC 2001), Long Beach, California, USA , 4-5 October 2001. Asis Nasipuri et al., “Power Consumption and throughput in Mobile Ad Hoc Networks using Directional Antennas”, in Proceedings of the IEEE International Conference on Computer Communication and Networks (ICCCN2002), October 14-16, 2002, Miami, Florida. QualNet Simulator Version 3.1, Scalable Network Technologies, http://www.scalable-networks.com. J. C. Liberti et al., “Smart Antennas for Wireless Communications: IS-95 and Third Generation CDMA Applications”, Prentice-Hall, 1999. Per H. Lehne et al., “An Overview of Smart Antenna Technology for Mobile Communications Systems”, IEEE Communications Surveys, http://www.comsoc.org/pubs/surveys, Fourth Quarter 1999, Vol. 2 No. 4. T. Ueda et al., “Evaluating the Performance of Wireless Ad Hoc Network Testbed With Smart Antenna”, Fourth IEEE Conference on Mobile and Wireless Communication Networks (MWCN2002), September 2002. T. Ohira, “Adaptive array antenna beamforming architectures as viewed by a microwave circuit designer”, 2000 Asia-Pacific Microwave Conference., Sydney, Dec. 2000. T. Ohira et al., “Electronically Steerable Passive Array Radiator (ESPAR) Antennas for Low-cost Adaptive Beam forming”, IEEE International Conference on Phased Array Systems, Dana Point, California, May 2000. K. Gyoda et al., “Beam and Null Steering Capability of ESPAR Antennas”, Proceedings of the IEEE AP-S International Symposium, July 2000.

  In Non-Patent Document 2 described above, tracking of the position of a mobile radio station is performed by using a tone set and holding a large amount of network status (status) information at each node radio station in the network. However, this is impractical for dynamic methods. For example, in Non-Patent Document 5, the originating radio station and the destination radio station identify each other's direction during an omnidirectional RTS-CTS exchange. However, with this mechanism, the node radio station does not recognize its complete neighborhood information.

  In Non-Patent Documents 3 and 4, the use of GPS (Global Positioning System) is proposed to track the position of each node radio station. However, regarding the exact mechanism of information exchange and the resulting overhead, Not discussed. In the previous research, the present inventors conducted a maintenance of a table (hereinafter referred to as an AS table) in which each node radio station indicates SINR for each azimuth, thereby dynamically maintaining a predetermined neighborhood information. A protocol was developed (see Non-Patent Document 9). In this method, in order to form an AS table, each node radio station sequentially transmits directional beacons in the direction of directional broadcast periodically in 30-degree intervals in all directions, and transmits the entire 360-degree space. Cover. The node radio station receiving these signals at different azimuths determines the best signal strength received and sends the information back to the originating radio station as a data packet with an RTS / CTS handshake. However, with this method disclosed in Non-Patent Document 6, the overhead due to the control packet is extremely high.

  For example, as shown in FIG. 10, while the node radio station Nn communicates with the node radio station Nm using the omni pattern antenna of the omni pattern An0, the node radio stations Np and Nr must be in an unused state. I must. However, when using the directional beam patterns An, Ar, Ap, while the node radio station Nn is communicating with the node radio station Nm, the node radio stations Np and Nr are both node radio stations Nq and Ns, respectively. And the efficiency of medium utilization or SDMA (Space Division Multiple Access) is dramatically improved.

  In order to fully utilize the capability of the directional antenna, each node radio station needs to recognize information on adjacent node radio stations (node radio station ID, direction, link quality, etc.) in advance. Communication between the node radio stations Np and Nq is started only when the direction from the node radio station Np to the node radio station Nq is not the same as the direction from the node radio station Np to Nm or from the node radio station Np to the node radio station Nn. can do. Thus, whenever the originating radio station and the destination radio station are communicating, all neighboring node radio stations of the originating radio station and the destination radio station must be able to initiate new radio communications in the other direction. The direction of communication must be known, thereby preventing interference with ongoing data communication between the originating radio station and the destination radio station. In other words, in order to implement an effective MAC and routing protocol in the wireless communication system, the node radio station must be aware of how to set its transmission direction for transmitting packets to its neighboring node radio stations. I must. Therefore, it is inevitable that each node radio station has a mechanism for tracking the position of the adjacent node radio station.

  However, this position tracking mechanism in a wireless communication system of an ad hoc wireless network using a directional antenna is a serious problem because of a great control overhead.

  Second, in order to fully utilize the capability of the directional antenna, each node radio station not only avoids transmission in the direction in which data communication is already in progress, but also other adjacent node radio stations. It is necessary to notify the communication state (communication status). In other words, the exposed terminal problem and the hidden terminal problem must be solved simultaneously. In particular, a string topology in an ITS (Intelligent Transportation System) highway traffic control method (as shown in FIG. 22, a topology in which two wireless links spaced apart from each other extend in a straight line. In some cases, some of the node wireless stations that are not aware of the ongoing wireless communication may try to communicate with a node wireless station that is already in use for some wireless communication. This can degrade the throughput of the directional mode and can be worse than in the omnidirectional mode. Thus, even if multiple parallel communications are possible with a directional antenna, the hidden terminal factor limits the gain provided by the directional antenna. As a result, not only does it have a location tracking mechanism for the adjacent node radio station that sets its transmission direction toward the destination radio station, but also a lot of waste that interferes with ongoing data communication by hidden node radio stations. It is essential to implement a broadcast mechanism that prevents the transmission of stale packets.

  The object of the present invention is to solve the above-mentioned problems, and in a multi-hop wireless network, it is possible to suppress interference from other stations and to provide an efficient MAC protocol for SDMA. It is to provide a method and a control device.

According to a first aspect of the present invention, there is provided a radio network control method comprising a plurality of radio stations each including an antenna capable of forming both a sector pattern having a predetermined beam width and an omnidirectional beam pattern. In a control method for a wireless network that performs wireless communication with a plurality of hops between a source wireless station and a destination wireless station among wireless stations,
A communication start control signal (RTS: Request To Send) from the transmission source and a communication reception signal (CTS: Clear To Send) from the reception source are both transmitted by the omnidirectional antenna, and the data signal (DATA) and reception are completed. Transmitting a notification signal (ACK: Acknowledge) with directivity;
After detecting a radio signal from another radio station using an omni pattern or sector pattern and rotating the beam direction of the antenna over all azimuth angles using the sector pattern to search for the azimuth angle with the maximum signal strength The method includes a step of prohibiting wireless communication using a sector pattern with respect to an azimuth angle of the wireless station when the detected wireless signal is not a wireless station performing wireless communication.

  In the wireless network control method, each of the wireless stations wirelessly transmits using a sector pattern, and the receiver sensitivity and the receiver threshold are set substantially equal to each other in each of the wireless stations. And

According to a second aspect of the present invention, there is provided a wireless network control device including a plurality of wireless stations each including an antenna capable of forming both a sector pattern having a predetermined beam width and a non-directional beam pattern. In a control device for a wireless network that performs wireless communication with a plurality of hops between a source wireless station and a destination wireless station among wireless stations,
A communication start control signal (RTS: Request To Send) from the transmission source and a communication reception signal (CTS: Clear To Send) from the reception source are both transmitted by the omnidirectional antenna, and the data signal (DATA) and reception are completed. Means for transmitting a notification signal (ACK: Acknowledge) with directivity;
After detecting a radio signal from another radio station using an omni pattern or sector pattern and rotating the beam direction of the antenna over all azimuth angles using the sector pattern to search for the azimuth angle with the maximum signal strength And a means for prohibiting wireless communication using a sector pattern with respect to the azimuth angle of the wireless station when the detected wireless signal is not a wireless station performing wireless communication.

  In the wireless network control device, each of the wireless stations wirelessly transmits using a sector pattern, and the receiver sensitivity and the receiver threshold value are set substantially equal to each other in each of the wireless stations. And

  Therefore, according to the wireless network control method or control apparatus of the present invention, in a wireless communication system such as ITS, for example, under a topology in which all wireless stations are located on one line, the directional RTS / CTS is The intention of communication by the source radio station can be notified in the opposite direction of the destination radio station, and many packets are not transmitted from the hidden node radio station. Therefore, as will be described later in detail with reference to the simulation result, the throughput and the end-to-end delay time can be improved as compared with the prior art even if the number of hops increases.

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

First embodiment.
FIG. 1 is a plan layout diagram of a plurality of radio stations 1-1 to 1-9 (generally referred to by reference numeral 1) showing the configuration of an ad hoc radio network according to an embodiment of the present invention. These are block diagrams which show the structure of each radio station 1 of FIG.

  In the wireless communication system of this embodiment, as shown in FIG. 1, a plurality of wireless stations 1 are present in a plane and each wireless station 1 has a gain, transmission power, and reception sensitivity of the variable beam antenna 101. A predetermined service area determined by parameters such as, and can perform packet communication within the service area. When performing packet communication with the wireless station 1 outside the service area, the wireless station 1 within the service area Is used as a relay station to relay packet data, thereby transmitting the packet data to a desired destination wireless station 1. That is, each wireless station 1 has a router function for routing packets and operates as a source wireless station, a relay station, or a destination wireless station.

  The wireless communication system of this embodiment is applied to a packet communication system of an ad hoc wireless network such as a wireless LAN, for example, and includes an omni pattern that is an omnidirectional radiation pattern and a predetermined plane in a horizontal plane centered on the own station. A variable beam antenna 101 capable of selectively switching between a sector beam pattern capable of selectively changing a sector-shaped main beam for each azimuth angle and an exclusive sector pattern capable of forming a null point for each azimuth angle. An adjacent node that can be measured when a radio signal is received from an adjacent node radio station (a node radio station that can perform radio communication from the own station) 1 in a service area centered on the own station AS table that is an azimuth and signal strength level table for storing the azimuth and signal strength levels for the radio station Stores Angle and Signal strength Table) in the database memory 154, based on these tables, is characterized by performing a routing of the packet signal while controlling the radiation pattern of variable beam antenna 101.

  This embodiment proposes a receiver-centric approach, especially for location tracking and MAC protocol. Each node radio station 1 periodically collects its neighbor information in order to track the position of its adjacent node radio station, and forms the AS table. Based on the AS table, the node radio station 1 recognizes the direction of the adjacent node radio station and controls medium access during transmission and reception. As will be described in detail later, the performance evaluation results regarding the QualNet network simulator (see, for example, Non-Patent Document 12) are highly efficient with respect to the increased number of communications and the increased data rate of our protocol. The throughput of the 1-hop MAC according to the present inventors' protocol is 1.8 times that of the IEEE 802.11 standard.

  In this embodiment, a receiver-oriented location tracking mechanism for reducing control overhead and a simple MAC protocol for efficient medium utilization are described. The inventors performed extensive performance evaluation using Qualnet and demonstrated its effectiveness. This MAC protocol is based on an omnidirectional exchange between RTS and CTS. However, the purpose of RTS / CTS in this case is not to prohibit transmission or reception by adjacent node radio stations of the transmitter and receiver, as in the case of using an omni pattern antenna, but to notify them about this communication. Is to do. This also specifies the approximate duration of the communication. All adjacent node wireless stations for transmission and reception track communication whose direction is known from each AS table for each of them, and set DNAV for virtual carrier detection to prohibit communication in that direction only To do.

  Next, the device configuration of each radio station 1 will be described with reference to FIG. In FIG. 2, a radio station 1 includes a variable beam antenna 101, a directivity control unit 103 for controlling the directivity thereof, a circulator 102, a data packet transmission / reception unit having a data packet transmission unit 140 and a data packet reception unit 130. 104, a traffic monitor unit 105, a line control unit 106, and an upper layer processing apparatus 107.

  Transmission signal data for communication in packet format generated by the upper layer processing device 107 that processes data to be transmitted / received is input to the modulator 143 via the transmission buffer memory 142, and the modulator 143 has a predetermined radio frequency. The carrier wave signal is subjected to spread spectrum modulation in accordance with the input communication transmission signal data using a predetermined communication channel spreading code generated by the spread code generator 160 by the CDMA method, and the modulated transmission signal is transmitted at a high frequency. Output to the machine 144. The high-frequency transmitter 144 performs processing such as amplification on the input transmission signal, and then transmits the variable signal from the variable beam antenna 101 to another wireless station 1 via the circulator 102. On the other hand, the communication signal received in the packet format received by the variable beam antenna 101 is input to the high-frequency receiver 131 via the circulator 102, and the high-frequency receiver 131 performs low noise amplification on the input received signal. After executing the above process, the data is output to the demodulator 132. The demodulator 132 demodulates the input received signal by spectrum despreading using the communication channel spreading code generated by the spreading code generator 160 by the CDMA method, and receives the demodulated received signal data as a receiving buffer. The data is output to the upper layer processing apparatus 107 via the memory 133 and also output to the traffic monitor unit 105 for traffic monitoring.

In the present embodiment, the variable beam antenna 101 that is a directional antenna is connected to a plurality of antenna elements and a control unit 103 that controls the directivity,
(A) an omni pattern which is an omnidirectional radiation pattern;
(B) For example, as shown in FIG. 3, a sector beam pattern that is a directivity pattern capable of selectively changing the sector-shaped main beam for each predetermined azimuth angle in a horizontal plane centered on the own station;
(C) An antenna capable of selectively switching an exclusive sector pattern capable of forming a null point for each azimuth angle by electrical control.

  The variable beam antenna 101 may be, for example, a known phased array antenna device, or, as will be described in detail later with reference to FIGS. 11 and 12, Patent Documents 1 and 2, Non-Patent Documents It may be a variable beam antenna which is an electronically controlled array antenna apparatus (Electronically Steerable Passive Array Radiator Array Antenna Apparatus) disclosed in 16, 17 and 18.

  The traffic monitor unit 105 includes a search engine 152, an update engine 153, a database memory 154, and a clock circuit 155, and performs routing and communication processing described later, and the wireless station 1 communicates with other wireless stations 1. The communication channel to be used in the packet communication is determined, and the spread code generator 160 sends the spread code designation data corresponding to the determined communication channel to the spread code generator 160 via the line control unit 106. The transmission timing control unit is controlled by generating a spreading code corresponding to the designated data and sending the designated data of the time slot corresponding to the determined communication channel to the transmission timing control unit 141 via the line control unit 106. 141 is a communication channel transmission signal by the transmission buffer memory 142 Controls to transmit the signal for the communication channel is transmitted in the corresponding time slot by controlling the writing and reading of over data. The clock circuit 155 counts the current date and time and outputs the information to the management control unit 151 as necessary.

  The search engine 152 of the traffic monitor unit 105 searches the data in the database memory 154 under the control of the management control unit 151 and returns the searched data to the management control unit 151. The update engine 153 updates data in the database memory 154 under the control of the management control unit 151. Further, an AS table is stored in the database memory 154. In the modification of the first embodiment to be described later, the database memory 154 further stores a DNAV control table.

  In this embodiment, the effective transmission beam width of the sector beam pattern for changing the directivity so that the gain in the direction of a single communication partner is maximized is set to 30 °, and the variable beam antenna 101 is used. The azimuth angle can be selectively changed every 30 °. The changing azimuth of the beam width and azimuth may be 60 ° or other azimuth. Further, the packet data used in the packet communication system of the present embodiment has a format of the format shown in FIG. That is, the packet data includes the ID of the destination wireless station, the packet type (tone, RTS (Request To Send), CTS (Clear To Send), DATA, etc.), the ID of the local station, and data (data in the upper layer). Etc.). In the case of an RTS signal or a CTS signal, the data includes a communication duration in the wireless communication. Furthermore, as shown in FIG. 5, the AS table stored in the database memory 154 stores azimuth and signal strength level information for each adjacent node radio station in the service area of its own station. It is created and updated by 15 wireless communication control processes.

  Further, the wireless communication system used in the present embodiment will be described in detail.

  First, details of the variable beam antenna 101 which is a smart antenna used in the present embodiment will be described. As a smart antenna used in the wireless network according to the present embodiment, basically, two types of a switch beam or a fixed beam antenna and a rotary adaptive array antenna can be used (for example, Non-Patent Document 12, 13, 14). The switch beam antenna generates a plurality of predefined fixed directional beam patterns, and sets one pattern at a time when a signal is received. This is the simplest technique and consists of N antenna elements deployed between separate directional antennas or in a non-overlapping fixed sector pattern, each spanned at an azimuth of 360 / N degrees. It consists only of the basic switching function between the predefined beams of the array antenna. Signal detection is performed in all sector patterns, and the variable beam antenna 101 has a capability of recognizing a sector having the maximum gain. Upon reception, exactly one sector pattern, generally selected by the detection process, collects and receives the signals.

  For rotating adaptive array antennas that have evolved from switched beam antennas, the beam configuration is adapted to the radio frequency (RF) signal environment and directs the beam towards the desired radio signal to maximize antenna gain. At the same time, the antenna pattern in the direction of the interference signal is suppressed (by setting it to null) (see Non-Patent Document 14). For adaptive array antennas, an algorithm is required to control the output signal, ie, to maximize the signal-to-interference plus noise ratio (SINR). The difference between these two smart antennas can be assumed as follows. That is, the fixed beam antenna concentrates its smartness in the direction of the strongest signal beam, while the adaptive array antenna uses weight vector adjustment to benefit from all received information in all antenna elements. To optimize the output SINR.

  The present inventors have developed a test bed of an ad hoc wireless network using a smart antenna (see Non-Patent Document 15), and each user terminal is small and low-profile known as an electronically controlled waveguide array antenna device. A cost smart antenna is used (see Non-Patent Documents 16, 17, and 18). An adaptive array antenna is usually a digital beamforming antenna. In contrast, electronically controlled waveguide array antenna devices rely on RF beamforming, which dramatically reduces circuit complexity. Since the electronically controlled waveguide array antenna device requires only one receiver output, the required number of frequency converters and analog-to-digital converters is reduced by the number of array branches, reducing DC power dissipation and manufacturing costs. Both can be improved dramatically (see Non-Patent Document 16).

  Next, a specific example of the electronically controlled waveguide array antenna device will be described in detail below. FIG. 11 shows an array antenna device 100 that is the electronically controlled waveguide array antenna device and an array antenna control device including peripheral circuits thereof, and FIG. 12 shows a longitudinal sectional view of the array antenna device 100. In FIG. 11, the array antenna apparatus 100 corresponds to the variable beam antenna 101 of FIG. 1, the circulator 6 corresponds to the circulator 102 of FIG. 1, the wireless transmitter 7 corresponds to the packet transmitter 140 of FIG. The portions from the low noise amplifier 1L to the demodulator 4 correspond to the packet receiver 130 in FIG. 1, and the adaptive control controller 20 and the learning sequence signal generator 21 correspond to the directivity controller 103 in FIG.

  As shown in FIG. 1, the array antenna control apparatus includes one excitation element A0, six non-excitation elements A1 to A6 each loaded with variable reactance elements 12-1 to 12-6, and a ground conductor. 11 and an adaptive control type controller 20 are configured.

  Here, the adaptive control type controller 20 is configured by a digital computer such as a computer, for example, and is included in a radio signal transmitted from the counterpart transmitter before starting radio communication by the demodulator 4 at the time of reception. A learning signal generated by the learning sequence signal generator 21 having the same signal pattern as the received signal y (t) when the learning sequence signal is received by the excitation element A0 of the array antenna apparatus 100. Based on the sequence signal r (t), for example, adaptive control processing by the steepest gradient method is executed. In this adaptive control processing, bias voltages applied to the variable reactance elements 12-1 to 12-6 for directing the main beam of the array antenna apparatus 100 in the direction of the desired wave and directing null in the direction of the interference wave The value is searched and set using the control voltage signal. Although the steepest gradient method is used in the above description, the present invention is not limited to this, and other adaptive control methods may be used. An input device (not shown) such as a keyboard is connected to the adaptive control type controller 20, and before starting wireless communication using the demodulator or the wireless transmitter 7, the user uses the input device to perform adaptive control. The operation of the adaptive control type controller 20 can be controlled by selecting a method or the like.

  In FIG. 1, an array antenna apparatus 100 is composed of seven antenna elements provided on a ground conductor 11, that is, an excitation element A0 and non-excitation elements A1 to A6. The excitation element A0 is on the circumference of a radius d. Are arranged so as to be surrounded by six non-excitation elements A1 to A6. Preferably, each of the non-excitation elements A1 to A6 is provided on the circumference of the radius d so as to be equidistant from each other (that is, spaced apart from each other by an equal azimuth angle with the excitation element A0 as the center). Each of the excitation elements A0 and the non-excitation elements A1 to A6 is configured to be a monopole element having a length of about λ / 4 with respect to the wavelength λ of the desired wave, and the radius d is λ / 4. Configured to be. Each antenna element has a diameter of 0.02λ. The feeding point of the excitation element A0 is connected to the low noise amplifier (LNA) 1 via the coaxial cable 5 and the circulator 6, and the non-excitation elements A1 to A6 are connected to the variable reactance elements 12-1 to 12-6, respectively. These variable reactance elements 12-1 to 12-6 change their reactance values in response to a control voltage signal from the adaptive control type controller 20.

  FIG. 2 is a longitudinal sectional view of the array antenna device 100. In FIG. 2, the excitation element A0 is electrically insulated from the ground conductor 11, and the non-excitation elements A1 to A6 are connected to the ground conductor 11 through the variable reactance elements 12-1 to 12-6 at high frequency. Grounded. The operation of the variable reactance elements 12-1 to 12-6 will be described. For example, when the longitudinal lengths of the excitation element A0 and the non-excitation elements A1 to A6 are substantially the same, for example, the variable reactance element 12-1 Is inductive (L property), the variable reactance element 12-1 becomes an extension coil, and the electrical lengths of the non-excitation elements A1 to A6 are longer than that of the excitation element A0, and function as a reflector. On the other hand, for example, when the variable reactance element 12-1 has capacitance (C-type), the variable reactance element 12-1 becomes a shortening capacitor, and the electrical length of the non-excitation element A1 becomes shorter than that of the excitation element A0. Acts as a director. The non-excitation elements A2 to A6 connected to the other variable reactance elements 12-2 to 12-6 operate in the same manner.

  Accordingly, in the array antenna apparatus 100 of FIG. 1, the reactance that is the junction capacitance value is changed by changing the bias voltage value applied to the variable reactance elements 12-1 to 12-6 connected to the non-excitation elements A1 to A6. By changing the value, the plane directivity of the array antenna apparatus 100 can be changed.

  A transmitting station that transmits a radio signal received by the array antenna 100 includes digital data having a predetermined symbol rate including a learning sequence signal having the same signal pattern as the predetermined learning sequence signal generated by the learning sequence signal generator 21. According to the signal, a radio frequency carrier signal is modulated using a digital modulation method such as BPSK or QPSK, and the modulated signal is amplified and transmitted to the array antenna apparatus 100 of the receiving station. In this embodiment, before performing data communication, a radio signal including a learning sequence signal is transmitted from the transmitting station to the receiving station, and adaptive control processing by the adaptive control type controller 20 is executed at the receiving station.

  The array antenna apparatus 100 receives a radio signal from a transmitting station, and the received signal is input to a low noise amplifier (LNA) 1 through a feeding coaxial cable 5 and a circulator 6 and amplified, and then downed. The converter (D / C) 2 performs low-frequency conversion of the amplified signal into a signal having a predetermined intermediate frequency (IF signal). Further, the A / D converter 3 A / D converts the low-frequency converted analog signal into a digital signal, and outputs the digital signal to the adaptive control controller 20 and the demodulator 4. Next, the adaptive control type controller 20 sequentially perturbs the reactance value of each variable reactance element by a predetermined difference width based on the input received signal y (t) and the learning sequence signal r (t). A predetermined evaluation function value (for example, received signal power) is calculated with respect to the reactance value, and the evaluation function value is maximized using the steepest gradient method based on the calculated evaluation function value. In addition, by repeatedly calculating each reactance value, the reactance value of each variable reactance element for directing the main beam of the array antenna apparatus 100 toward the desired wave and the null toward the interference wave is calculated. Control to set. Thus, the bias voltage value of each variable reactance element for directing the main beam of the array antenna apparatus 100 in the direction of the desired wave and the null in the direction of the interference wave is searched so that the evaluation function value becomes maximum. Then, a control voltage signal having each searched bias voltage value is output to each variable reactance element and set.

  The radio transmitter 7 modulates a radio carrier wave by a predetermined modulation method based on the input transmission baseband signal, and the radio signal that is the modulated radio carrier wave is arrayed via the circulator 6 and the feeding coaxial cable 5. The signal is output to the excitation element A0 of the antenna device 100, whereby a radio signal is radiated from the array antenna device 100.

  By the way, the characteristics of the array antenna device 100 which is an electronically controlled waveguide array antenna device include beam direction control, formation of multiple beams (frequency is the same), mechanical rotating beam (360 degree sweep), and null steering control. . For receiver applications, the null must be oriented in the direction in which the interference signal arrives. The adaptive null steering algorithm in the receiver can also be used for automatic suppression of interference signals coming from other directions (see Non-Patent Document 17). It has been observed that if the 7-element array antenna apparatus 100 is used, 360-degree continuous beam / null steering is possible with simultaneous 8 dBi beam gain and −30 dBi null (see Non-Patent Document 17). It has also been observed that the 7-element array antenna apparatus 100 can simultaneously form directional multiple beams and many nulls.

  Developing a suitable MAC protocol with adaptive antennas in ad hoc wireless networks is a difficult but interesting task. As such, most of the research done in wireless communication systems for ad hoc wireless networks assumes the use of simpler switched beam antennas. Also in this embodiment, the present inventors preferably use an array antenna device 100 which is a smart electronically controlled waveguide array antenna device as a switch beam antenna. The array antenna apparatus 100 selects a plurality of receiver outputs (frequency converter and analog-digital converter) by selecting a reactance value of one specific directional beam from a plurality of directional beam patterns. Without being used, it can also be used as a generalized switch beam antenna or a pseudo switch beam antenna. Details As described below, continuous tracking can be achieved by including some mechanism for detecting the direction of arrival (DOA) of the signal received from the user, and this is considered a generalization of the concept of switched beams. (See Non-Patent Document 14). Again, the received power is maximized. The advantage of using the array antenna apparatus 100 as a generalized switch beam antenna is that it can be continuously tracked with only one receiver output and can have a variable number of beam patterns. In other words, when used in the switched beam mode, the directional beam formed using the electronically controlled waveguide array antenna device is as in a conventional switched beam antenna having a plurality of N elements. It is not necessary to be limited to non-overlapping fixed sectors each having an azimuth angle of 360 / N degrees. Since array antenna apparatus 100 is a low-cost, low-power small antenna, it can be considered to promote reduction of power consumption of user terminals in an ad hoc wireless network and bring all the advantages of a switch beam antenna. It is done.

  13A and 13B show antenna patterns of the array antenna apparatus 100 having a beam width of 60 degrees. FIG. 13 (a) shows a radiation pattern when the azimuth angle Ad is 0 degrees. In this beam pattern, six beams are formed in each antenna element in a section of 0 to 60 degrees, a section of 60 to 120 degrees, and the like. . FIG. 13B shows a radiation pattern at 30 degrees, and in this beam pattern, six more beams are formed in each section between 30 and 90 degrees, 90 to 150 degrees, and the like. These constitute twelve overlapping patterns combined at 30 degree intervals. FIG. 13 (c) shows a Qualnet default antenna pattern with a 45 degree beam width, and FIG. 13 (d) shows an ideal directional antenna with a 45 degree beam width with insignificant side lobes. As demonstrated in the performance evaluation, the performance of an ideal directional antenna is (as expected) best, and at the same time, the performance of the array antenna device 100 is far superior to the Qualnet default antenna pattern. The reason is that the radiation pattern of the array antenna apparatus 100 has a smaller effective range than the case of the default antenna pattern in the qualnet, and the side lobe is not so conspicuous.

  Next, the direction of arrival (DOA) detection and the position tracking mechanism according to the present embodiment will be described in detail below.

  In this embodiment, each node radio station 1 stands by in an omnidirectional reception mode while in an idle state. When any radio signal exceeding the threshold is detected, it enters a rotating sector pattern receive mode. In the reception mode of the rotating sector pattern, the node radio station 1 sequentially rotates the variable beam antenna 101, which is the directional antenna, in all directions at intervals of 30 degrees, and sequentially receives the entire 360-degree space in each direction. The signal received in each direction is detected. After one rotation, the node radio station 1 determines the best receivable direction with the received signal having the maximum signal strength. Next, the node radio station 1 sets the beam in the direction and receives a radio signal.

  However, to enable the receiver to decode the received signal, each control packet (including a beacon signal, an RTS signal, or a CTS signal) is preceded by a preceding tone signal (unmodulated carrier as shown in FIG. 7). ) Is transmitted for a duration such that the time to rotate the receiver's rotating receive beam 360 degrees is shorter than the duration of the tone signal. The purpose of transmitting the tone signal in this way before any control packet is to allow the receiver to track the best possible direction of the radio signal. When the receiver sets the beam in that direction, the purpose of the tone signal is fulfilled and a control packet is subsequently transmitted.

In the proposed wireless communication system according to the present embodiment, the inventors of the present invention have three types of control packets, that is, beacon signals or “hello” packets used for tracking the position of the adjacent node wireless station 1, and medium access control. RTS signal and CTS signal are used. The beacon signal is a periodic signal and is transmitted from each node radio station 1 at a predefined interval. At each periodic interval, each node radio station 1, for example Nm, transmits an omnidirectional beacon signal to its adjacent node radio station if the medium is free. As pointed out above, each beacon signal is transmitted following a tone signal that assists the receiver in detecting the best possible direction of the beacon signal. Each receiver then sets its beam in that direction and receives and decodes the beacon signal. Thus, for example, the node radio station Nn, which is an adjacent node radio station of the node radio station Nm, forms signal level information for each azimuth angle of the node radio station Nm, and similarly forms information of other adjacent node radio stations. . The input of the node radio station Nn to the AS table related to the adjacent node radio station Nm is “SIGNAL ^α _{n, m} (t)”, which is the node radio station Nn to the node radio station Nn. The maximum intensity of the signal received at the azimuth angle α and detected at any time point t by the node radio station Nn. Based on the AS table, the node radio station Nn recognizes the direction of the node radio station Nm and controls medium access during transmission and reception.

  Since the RTS signal is a broadcast packet and includes a source address, the node radio station can also form an AS table that is a signal level table for each azimuth by decoding the RTS signal. . Therefore, the inventors used the RTS signal as a beacon signal. When the RTS signal is transmitted, the beacon signal timer is reset. The use of an RTS signal as a beacon signal is effective in high frequency traffic where the overhead due to the beacon signal is minimized. This is because the transmitting-side node radio station does not need to send an additional beacon signal to notify its neighbor node radio station of its presence.

  Next, a medium access control protocol that supports directional communication will be described below. The IEEE 802.11 MAC protocol standard uses an RTS-CTS / data-acknowledgement (ACK; exchange completion notification signal) exchange mechanism to ensure reliable data communication. In our method, first, when the node radio station Nn desires communication with the node radio station Nm, the medium is detected, and if the medium is free (unused), an omnidirectional RTS signal is transmitted. The back-off mechanism is the same as in IEEE 802.11. The purpose of the RTS signal is to notify all adjacent node radio stations of the node radio station n including the node radio station Nm that communication is requested from the node radio station Nn to the node radio station Nm. This also specifies the approximate duration of the communication. All neighboring node radio stations of the node radio station Nn track this request from the node radio station Nn, the direction of which is recognized by each of these node radio stations from the received RTS signal. The mechanism for receiving the RTS signal is the same as for the beacon signal.

  The target node radio station Nm issues a request by transmitting an omnidirectional CTS signal, and the node radio station Nm receives data from the node radio station Nn to the adjacent node radio station of the node radio station Nm. Notify that you are going. This also specifies the approximate duration of the communication. All adjacent node radio stations of the node radio station Nm track the receiving node radio station Nm, and its direction is recognized by each of these node radio stations from the received CTS signal. Again, the mechanism for receiving the CTS signal is the same as for the beacon signal. However, the purpose of RTS / CTS in this case is not to prohibit transmission or reception by the node radio stations Nn and Nm adjacent to the node radio stations Nn and Nm, as in the case of using an omni-pattern antenna. This is to notify Nm adjacent node radio stations that the node radio station Nm is receiving data from the node radio station Nn.

  When the omnidirectional CTS signal is transmitted, the receiving node radio station stands by in the directional reception mode, and returns to the omnidirectional reception mode when a data signal is transmitted or a time-out occurs. Also, when a CTS signal is received, the transmitting side transmits data directionally and waits for an acknowledgment signal (ACK signal) in a directional pattern, and when an acknowledgment signal (ACK signal) is received, or When timeout occurs, it returns to the omnidirectional reception mode. A directional reception mode ensures proper signal reception from the required direction and minimization of interference from other directions.

  Other adjacent node radio stations in the vicinity of the node radio stations Nn and Nm that have received (heard; overheard) the exchange of RTS / CTS receive their DNAVs in the direction of arrival of the RTS signal or CTS signal, respectively. Is set in the detected direction. At this point, if they have a packet to send to a node radio station whose direction as recognized from the AS table is not in the direction of the blocked DNAV, they will communicate between the node radio stations Nn and Nm. Both RTS and CTS signals can be issued omnidirectionally without interference. If the direction of the receiving node radio station is blocked by DNAV and an RTS signal is issued, the CTS signal is most likely not issued, otherwise a collision with the RTS signal may occur. As a result, the node radio station increases its collision window and enters backoff. This may occur repeatedly, and as a result, the node radio station decreases the transmission opportunities. Therefore, in this case, the inventors do not permit transmission of the RTS signal. Here, the node radio station waits for the DNAV time and tries to start communication. This is similar to the NAV standby described in the IEEE 802.11 standard.

FIG. 14 shows two simultaneous communication mechanisms that occur in the same service area according to a modification of the first embodiment. The communicating shall originating a source radio station N _S and a destination radio station N _D. Figure 14 shows the directional beam from the source radio station N _S including the destination radio station N _D. Here, both assumed that the radio station N _S other neighboring nodes a radio station pair present in the vicinity of the omnidirectional and N _D N _X and N _Y wants wireless communication (Fig. 14). Both the node radio stations N _X and N _Y have already received RTS / CTS from the radio stations N _S and N _D. From their respective AS table, the node radio station N _X recognizes the azimuthal position with respect to the node radio station N _X of the source radio station N _S and a destination radio station N _D, also the node radio station N _X and N _Y The It recognizes the azimuthal position with respect to the node radio station N _Y radio station N _S and N _D. Both the node radio stations N _X and N _Y set DNAV toward the radio stations N _S and N _D. If the directional beam from the node radio station N _X to node radio station N _Y is by capturing a radio station N _S or N _D, the node radio station N _X remains idle until a timeout is mentioned in DNAV And thus hope for wireless communication is postponed. If other, the node radio station N _X may issue a RTS signal. In other words, the node radio station can issue the RTS signal only when the radio communication does not enter the existing radio communication area.

  FIG. 15 is a state transition diagram in the wireless communication control process executed in the present embodiment. In FIG. 15, first, in the state S101, it is in an idle state, and waits in the omni pattern detection mode or the rotation sector detection mode. Here, when the beacon timer for issuing a periodic beacon signal times out, after the beacon signal is transmitted in an omni pattern in the state S102, the process returns to the state S101. When there is data to be transmitted in the state S101, after transmitting the RTS signal in the omni pattern in the state S103 (at this time, since it is an omni pattern, the DNAV in the direction of the receiving radio station is not blocked), the process returns to the state S101. Further, when a signal having a signal level exceeding the detection threshold is received in the state S101, the sector pattern is rotated once in the state S104 to track the signal arrival direction and direct the main beam in the maximum reception direction, and then in the state S105. A packet signal is received with a sector pattern.

  When the beacon signal is received in the state S105, the state transits from the state S106 to the state S107, and the information data is stored in the state S107. Here, the azimuth and the signal intensity level in the AS table are updated, and then the state returns to the state S101. .

  Further, when the RTS signal is received in the state S105, the state transits from the state S108 to the state S109, and in the state S109, it is checked whether or not the target receiving radio station is desired to perform wireless communication. On the other hand, if NO, the flow proceeds to the state S113. In state S110, a CTS signal is transmitted in an omni pattern. In state S111, a DATA signal is waited for in a sector pattern. When a DATA signal is received, an ACK signal is transmitted in a sector pattern in state S112. Return to. On the other hand, when a time-out occurs in the state S111, the process returns to the state S101. Further, when NO in the above state S109, “time data” calculated by adding a predetermined communication time, which will be described in detail later, to the current time as control data in the DNAV control table in the state S113 (until the azimuth angle until the time After indicating that wireless communication is impossible, the process returns to the state S101.

  Furthermore, when the CTS signal is received in the state S105, the state transits from the state S114 to the state S115, where it is checked whether or not it is the intended receiving radio station to be wirelessly communicated. If YES, the state transits to the state S116. On the other hand, if it is NO, the flow goes to the state S118. In state S116, after transmitting the DATA signal in the sector pattern, in state S117, it waits for the ACK signal in the sector pattern, and returns to state S101. In the state S118, “time data” calculated by adding a predetermined communication time, which will be described in detail later, to the current time as control data in the DNAV control table (until this time, wireless communication is impossible at the azimuth angle). ) Is recorded, and the process returns to the state S101.

  Furthermore, some assumptions and theoretical grounds in the wireless communication system according to the present embodiment will be described below.

  When the node radio station antenna is operating in omnidirectional mode, it has the ability to send and receive signals from all directions, for example with an omnidirectional gain Gomni, and during idle periods the node radio station is omnidirectional Operates in receive mode.

  When the node radio station's antenna is operating in a directional mode, the node radio station directs its beam (main lobe) in a particular direction that is a gain of the beam width w and Gdir (Gdir >> Gomni), for example. Can do. In our simulation, the beam width is about 60 degrees.

  Therefore, with regard to the predetermined input power amount, the transmission arrival distance (radius) Rdir using the directional antenna is much larger than the transmission arrival distance Romni when the corresponding omni pattern antenna is used.

  The inventors define a node radio station adjacent to the node radio station Nn as a node radio station set within the transmission service area of the omnidirectional transmission reach of the node radio station Nn. These are assumed to be one hop away from the node radio station Nn. This is because a node radio station outside the omnidirectional transmission service area of the node radio station Nn uses a directional beam formed from the node radio station Nn to the node radio station. This means that even if it can be reached by the station Nn in one hop, it is not regarded as an adjacent node radio station of the node radio station Nn. From the viewpoint of directional data communication, this means that, for example, an adjacent node radio station of Nm, for example, of a node radio station of Nn is always a strong adjacent node radio station. As shown in FIG. 10, when the node radio station Nn forms a directional beam toward the adjacent node radio station Nm, the node radio station Nm is completely within the transmission zone of the transmission service area thus formed. (See FIG. 10). Therefore, the strength of the signal received from the node radio station Nn at the node radio station Nm is always strong enough to ensure proper acquisition even in the presence of other interference. Therefore, there is a possibility that the link connection of the node radio station Nm is disconnected or the link connection is weakened during the data packet transfer from the node radio station Nn due to the outward mobility of either the node radio station Nm or Nn. The nature is extremely low.

  Thereby, the problem of the hidden terminal as pointed out in Non-Patent Document 4 is alleviated. Consider FIG. 16 where the node radio station Nn is in radio communication with the node radio station Nm by a directional beam. Here, the node radio station Np wishes to communicate with the node radio station Nq. If the node radio station Np is in the vicinity of the node radio station Nn (in the transmission service area), the node radio station Np is not allowed to form a directional beam in the direction of the node radio station Nn and / or Nm. This communication is not started. However, if the node radio station Np is outside the node radio station Nn (transmission service area), the node radio station Np forms a directional beam toward the node radio station Nq and starts communication. This may interfere with reception of the node radio station Nm. However, since the distance between the node radio station Np and the node radio station Nm is longer than the distance between the node radio station Nn and the node radio station Nm by the omni pattern gain Romni (omnidirectional range), the node radio station Nm The signal received from the node radio station Nn is dominant, and the possibility of data packets being lost due to this interference is negligible.

  However, as a result of this assumption, the use of a directional antenna can be achieved because the destination radio station can be reached with fewer hops than by using a directional beam with a larger transmission service area. The multi-hop efficiency that could have been done is sacrificed. However, as demonstrated by the performance evaluation, what we are trying to obtain is SDMA efficiency.

  FIG. 8 is a timing chart showing the types of radiation patterns and radio communication protocols in each node radio station used in the first embodiment. In FIG. 8, an omni pattern is used in the transmission of the tone signal + RTS signal and the transmission of the tone signal + CTS signal from the node wireless station on the transmission side. On the other hand, in the reception of the tone signal + RTS signal at the receiving node radio station, the tone signal is detected by the omni pattern or the center pattern at the start thereof, and then rotated once in a range of 360 degrees using the sector pattern. (Rotating sector pattern) An azimuth angle capable of obtaining the maximum signal strength is detected, a sector pattern directed to the azimuth angle based on the AS table is used, and adaptive control is performed during communication using the sector pattern. And a RTS signal is received using a sector pattern (or an omni pattern or an adaptive control pattern).

  As described above, according to the first embodiment, after detecting the radio signal from the source radio station, the beam pattern of the antenna is rotated over all azimuth angles using the sector pattern to maximize the signal strength. After searching for an azimuth angle having an angle, control is performed so that wireless communication is performed with the beam direction of the antenna directed toward the azimuth angle having the maximum signal strength. Therefore, in a wireless network in which wireless communication is performed with one hop between a source wireless station and a destination wireless station, overhead can be greatly reduced as compared with the prior art, and position tracking can be performed at high speed.

  Furthermore, the characteristics of the wireless communication control process according to the modification of the first embodiment will be described below. FIG. 6 is a table showing an example of the DNAV control table stored in the database memory 154 of FIG. 2 and used in the modification of the first embodiment, and FIG. 9 shows each peripheral used in the modification of the first embodiment. FIG. 14 shows the types of radio patterns and radio communication protocols in adjacent radio stations (more precisely, in FIG. 14, a node radio station existing in a transmission service area that is an omni pattern area of a source radio station NS). It is a timing chart.

  First, creation and update processing of the DNAV control table used in the modification of the first embodiment will be described below. Note that the variable beam antenna 101 has a sector pattern in which the azimuth of the beam can be set every 30 degrees. As shown in FIG. 6, the DNAV control table is provided with “time data” and “usable” information in the control data column for each set azimuth angle. This indicates that the azimuth is in use, that is, it cannot be used until that time. “Usable” indicates that wireless communication can be used for the azimuth angle.

First, in the initial state, “usable” information is inserted in all the columns of the control data of the DNAV control table. Next, when NO in the state S109 or S115 in FIG. 15, the control data is recorded as follows in the DNAV control table, and the process returns to the state S101.
(Case 1) In the DNAV control table, when the field of control data corresponding to the azimuth angle of the received RTS signal or CTS signal is “available”, the communication duration included in the RTS signal or CTS signal is The communication end time is calculated by adding to the time, and the calculated “time data” is recorded with respect to the azimuth angle of the received RTS signal or CTS signal.
(Case 2) In the DNAV control table, when the field of control data corresponding to the azimuth angle of the received RTS signal or CTS signal is a predetermined “time data”, the communication duration included in the RTS signal or CTS signal The communication end time is calculated by adding the time to the current time, and if the calculated communication end time is the same as or earlier than the already recorded “time data” time, no processing is performed. When the calculated communication end time is later than the already recorded “time data” time, the later calculated communication end time is recorded as “time data” of the azimuth.

  Furthermore, in the idle state in state S101, when the time of “time data” described in the control data column of the DNAV control table has passed the current time, the “time data” is changed to “usable” and updated. To do.

  That is, each neighboring neighboring radio station transmits a tone signal and an RTS signal or transmits a tone signal and a CTS signal in response to the start of radio communication with another radio station as shown in FIG. In doing so, wireless communication is performed using only the sector pattern of the azimuth angle that can be used with reference to the DNAV control table. Therefore, each node wireless station can know the wireless communication currently in progress for each predetermined azimuth by generating and using the DNAV control table, and using this information, a new communication in another direction can be performed. Wireless communication can be started, and at this time, interference with currently ongoing wireless communication can be prevented. This can provide an efficient MAC protocol for SDMA in a one-hop wireless network.

  The present inventors performed a simulation as follows for the wireless communication system according to the first embodiment, and obtained the following simulation results. The simulation was performed using QualNet 3.1 (see Non-Patent Document 12). The simulation of the array antenna device 100, which is an electronically controlled waveguide array antenna device, was performed in the form of a pseudo-switched beam antenna that was rotated discretely at an azimuth angle of 30 degrees to cover a span of 360 degrees.

Here, the following radiation pattern described above was used for the simulation of the MAC protocol.
(I) The radiation pattern of the electronically controlled waveguide array antenna device 100 simulated (referred to as “array antenna device 100” in FIGS. 17 to 20);
(Ii) Qualnet default directional antenna pattern (referred to as “Qualnet default antenna” in FIGS. 17 to 20);
(Iii) An ideal directional antenna pattern without side lobes (referred to as “ideal directional antenna” in FIGS. 17 to 20).

  The Qualnet Simulator was modified to perform directional virtual carrier detection in the MAC layer and directional transmission in the physical layer of the Qualnet Simulator. In the simulation, based on the hardware performance of the array antenna apparatus 100, the duration of the preceding tone in the control packet signal was selected to be 200 microseconds.

  In order to avoid the influence of the routing protocol and clearly show the difference between the MAC protocol defined in IEEE 802.11 and the MAC protocol according to the present embodiment proposed by the present inventors, a simple randomly selected One-hop wireless communication was used. We also used static routes to stop all packets generated by any routing protocol, whether proactive or active. In the simulation, the performance of the conventional omnidirectional IEEE 802.11 MAC protocol and the MAC protocol according to the present embodiment were compared and investigated by changing the data rate and the number of simultaneous communications. In the investigation of the MAC protocol according to the present embodiment proposed by the present inventors, different antenna patterns as described above were used in order to confirm the robustness of the MAC protocol according to the present embodiment. In the execution, the array antenna apparatus 100 was used as one of the antenna patterns, and the performance of the array antenna apparatus 100 was also evaluated.

  In the simulation, 40 node radio stations 1 are randomly arranged in an area range of 1000 m × 1000 m. The simulation is performed in two steps. First, the number of simultaneous communications is maintained at 10, and the data rate is sequentially set to 2.048 Mbps (512-byte data packet transmitted at 50-millisecond intervals) from 81.92 kbps (at 2-millisecond intervals). Increase the number of simultaneous communications from 4 to 12, keeping the data rate at 409.6 kbps (512-byte data packets transmitted at 10 millisecond intervals). Increased. In both steps, the average throughput and the average end-to-end delay time of 1 hop were evaluated. Table 1 shows the parameter set used.

  Next, the results and examination of the simulation will be described below. The conventional MAC protocol defined in IEEE 802.11, which is denoted as “IEEE 802.11” in FIGS. 17 to 20, is used as a benchmark for comparison, and each of the array antenna apparatus 100, the Qualnet default antenna, The performance of the MAC protocol proposed by the present inventors was evaluated with an ideal directional antenna. The evaluation was based on two criteria: average throughput and 1 hop average end-to-end delay.

  17 to 20 show the simulation results, respectively. Each reported result is an average of 10 runs with different seeds. Therefore, in order to obtain perfect results, we were forced to simulate over 400 scenarios, each of which was run in the simulator for 5 minutes to obtain an overall average result.

  In FIG. 17, as the data rate increases, the average throughput of the MAC protocol proposed by the present inventors using an arbitrary directional antenna pattern (hereinafter referred to as E-MAC protocol) is more omni pattern. It can be seen that it is far superior to the case of IEEE 802.11 using an antenna. Also from FIG. 18, the E-MAC 1-hop average end-to-end delay time performance using any directional antenna is achieved using the IEEE 802.11 MAC protocol. It turns out that it is far superior to the thing.

  In the omnidirectional IEEE 802.11 MAC protocol, it is more likely that a backoff state must be entered when the medium is found to be in use. As the data rate increases, MAC contention increases. However, if the directional antenna is used and the directional virtual carrier detection is performed, the E-MAC protocol according to the present embodiment cannot be generated by the “IEEE 802.11 MAC protocol” using the omni pattern antenna. Create an environment with lower contention. Therefore, as shown in FIG. 17, when the data rate increases, the average throughput increases rapidly in the E-MAC protocol. In the E-MAC protocol, when the RTS / CTS handshake is executed, the node radio station transmits data directionally with high gain and receives an acknowledgment signal (ACK signal). Therefore, the possibility of failing to receive data at the receiver side or an acknowledgment signal (ACK signal) at the transmitter side is minimized. However, in the IEEE 802.11 protocol, there is a greater possibility that data will be missed than in the case of RTS / CTS. This is because (a) data is transmitted in all directions with the same gain as in RTS / CTS, and is received in all directions. (B) Data packets are larger than RTS / CTS and are received properly. For two reasons that the SINR level needs to be kept high over a long period of time. These reasons also explain that the average throughput is higher and the end-to-end delay time is lower in the E-MAC protocol than in IEEE 802.11.

  The performance of the MAC protocol greatly depends on the pattern of the directional antenna. Therefore, the simulation is performed on three different types of directional antenna patterns. Qualnet's default antenna is a standard antenna pattern. An ideal directional antenna is an ideal directional antenna pattern without side lobes. This is as described above. The average throughput using the array antenna apparatus 100 is superior to the Qualnet default antenna, and the throughput gain achieved by the array antenna apparatus 100 is approximately 1.8 times that of IEEE 802.11.

  In FIG. 19, it is observed that the average throughput decreases with both the E-MAC protocol and the IEEE 802.11 protocol as the number of simultaneous communications increases, but the E-MAC protocol significantly increases the average throughput. Show a good gain. This is because the E-MAC protocol does not prohibit transmission by the adjacent node radio station, but merely notifies the adjacent node radio station of the ongoing communication and its direction, so that the adjacent node radio station moves to the other direction. By being able to start communication. However, IEEE 802.11 using an omni-pattern antenna issues RTS / CTS to keep all adjacent node radio stations in a silent state (silent silent state).

  Further, as the number of simultaneous communication increases, as shown in FIG. 19, the average end-to-end delay time (1 hop) increases in both the IEEE 802.11 protocol and the E-MAC protocol. The “IEEE 802.11 protocol” is much more prominent than the E-MAC protocol regardless of the use of the directional antenna pattern. When the number of simultaneous communications increases, the interference of each communication increases due to the interference corresponding to the added number of simultaneous communications. However, since the E-MAC protocol notifies the other node radio stations in the vicinity of the ongoing communication, and transmits and receives using a directional radiation pattern with a larger acquisition, interference from other directions is also caused. Minimized. In this way, the E-MAC protocol exploits SDMA efficiency that allows for a greater number of simultaneous communications, so less queuing delay and less one-hop average end as observed in FIG. -A two-end delay time can be obtained.

  As described above, the use of a directional antenna in an ad hoc wireless network can dramatically improve system performance if an appropriate MAC protocol can be designed. If the directional antenna is used, the medium can be utilized to the maximum by the directional setting of the virtual carrier detection. By minimizing the location tracking overhead, the gain achieved with the MAC can be enormous. At the same time, the success of the MAC protocol is highly dependent on the pattern of directional antennas. The average throughput when using the array antenna device 100, which is an electronically controlled waveguide array antenna device, is better than that of the Qualnet default antenna, and the throughput gain achieved by the array antenna device 100 is the MAC of IEEE 802.11. This is approximately 1.8 times that of the protocol.

Second embodiment.
FIG. 21 is a plan view of each wireless station that executes multihop wireless communication control processing in an ad hoc wireless network according to the second embodiment. The wireless communication system according to the second embodiment has the same hardware as the wireless communication system itself as compared with the wireless communication system according to the first embodiment, but the one-hop wireless in the first embodiment. For communication routing, as shown in FIG. 21, among the node radio stations 1-1 to 1-7 each having at least one radio link with another node radio station, from the source radio station to the destination radio station Multi-hop, i.e., multi-hop wireless communication routing, where each neighboring neighboring wireless station, particularly when starting wireless communication with other wireless stations, as shown in FIG. When transmitting a signal and an RTS signal, or transmitting a tone signal and a CTS signal in response thereto, a sector pad of an azimuth angle that can be used with reference to the DNAV control table is referred to. It is characterized by performing wireless communication by using only over emissions. Specifically, in multi-hop wireless communication, the wireless communication control process of FIGS. 9, 14 and 15 is executed.

  In this embodiment, an efficient directional MAC protocol with a direction search method for ad hoc wireless networks is proposed. This efficient directional MAC protocol is a direction search method oriented to a receiving node radio station 1 in which each node radio station 1 periodically collects directional information in the vicinity thereof and forms an AS table. Is used. Based on the AS table, each node radio station 1 knows the direction of its adjacent node radio station and controls medium access during transmission and reception. As shown in FIG. 9 according to the modification of the first embodiment, the directional DATA / ACK packet is transmitted after the omnidirectional RTS / CTS. This omnidirectional RTS / CTS can be issued without interfering with ongoing wireless communications by using DNAV (Directed Network Position Vector) with azimuth information from the AS table. We are also investigating the effects of equalized receiver sensitivity and receiver threshold.

  In the previous research by the present inventors, each node radio station performs maintenance update of the SINR table for each azimuth, thereby dynamically maintaining predetermined neighborhood information (see Non-Patent Document 9). Developed. In this method, in order to form an AS table, each node radio station periodically transmits a directional beacon signal in the form of a directional broadcast continuously in 30-degree intervals in all directions to cover the entire 360-degree space. To do. A plurality of node radio stations that receive these signals at different azimuth angles determine the best quality of the received signals and send the information back to the source node radio station as data packets with an RTS / CTS handshake. Here, with this method, the overhead due to the control packet is extremely high (see Non-Patent Document 9).

Next, a directional MAC protocol having a directional search method will be described below. The directional MAC protocol according to the present embodiment is basically a “directional MAC protocol based on a receiver-oriented rotating sector” that also functions as a directional search method. In order to track the direction of the adjacent node radio station, each node radio station Nn periodically collects its neighborhood information and forms an AS table. SIGNAL ^θ _{n, m} (t) is the maximum of signals received at the node radio station Nn from the node radio station Nm at the azimuth angle θ with respect to the node radio station Nn and detected by the node radio station Nn at an arbitrary time point t. It is strength. Based on the AS table, the node radio station Nn knows the direction of the node radio station Nm and controls medium access during transmission and reception. In this case, each node radio station stands by in the omnidirectional detection mode. This is a form of directional reception in which a rotating sector reception mode is entered every time a signal exceeding a threshold is detected, and the directional antenna is continuously rotated in all directions at intervals of 30 degrees. Covers the entire 360 degree space and detects the received signal in each direction. Once the rotation is complete, the maximum possible signal reception direction is determined by the maximum received signal strength. The beam is then set in that direction and a signal is received. However, in order for the receiver to be able to decode the received signal, each control packet has a slightly shorter time for the receiver's rotating receive beam to rotate 360 degrees than the duration of the tone (inventor's In these cases, it is transmitted with a preceding tone signal having a duration of 200 microseconds). The purpose of this tone transmitted before any control packet is to allow the receiver to track the best possible direction of signal reception. When the beam is set in that direction, the purpose of the tone signal is fulfilled and a control packet is subsequently transmitted. Each node radio station periodically transmits an omnidirectional beacon, and the adjacent node radio station receiving the beacon signal decodes it and enters it in the AS table. In this case, the RTS / CTS signal is transmitted with a preceding tone signal and includes a source radio station address that also functions as a beacon signal, thereby minimizing the overhead of beacon transmission at high traffic.

  For example, when the node radio station Nn wishes to start data communication with the node radio station Nj, the node radio station Nn checks the radio medium, and if it is free (unused), the node radio station Nn transmits an omnidirectional RTS signal. Issue. The target receiving node radio station Nj that has received the RTS signal transmits and issues an omnidirectional CTS signal. The purpose of RTS / CTS in this case is not to prohibit transmission or reception by the node radio stations adjacent to the node radio stations Nn and Nj as in the case of the omni-pattern antenna, but the node radio station Nj It is to inform the node radio stations Nj and Nn adjacent node radio stations that data is being received from the station Nn. This can also specify the approximate duration of the communication. All adjacent node radio stations of the node radio stations Nn and Nj track communication between the node radio stations Nn and Nj by setting their DNAVs toward the node radio stations Nn and Nj. Thus, adjacent node radio stations in the vicinity of the node radio stations Nn and Nj can start communication in the other direction without interfering with the current communication between the node radio stations Nn and Nj. Next, the source radio station and the destination radio station transmit data and an acknowledgment signal (ACK signal) directionally using the sector pattern, and wait for an acknowledgment signal (ACK signal) and a data signal in the directional reception mode, respectively. .

  As described above, according to the present embodiment, in a wireless network that performs multi-hop wireless communication, a radio signal from another wireless station is detected, and the beam direction of the antenna over all azimuth angles using a sector pattern After searching for the azimuth having the maximum signal strength by rotating, wireless communication is performed using the sector pattern for the azimuth of the wireless station when the detected wireless signal is not a wireless station performing wireless communication. Is prohibited. Therefore, in a wireless communication system such as ITS, for example, in a topology in which all node wireless stations are located on one line, the directional RTS / CTS determines the communication intention of the source wireless station in the opposite direction of the destination wireless station. And many packets are not transmitted from a hidden node radio station. Therefore, as will be described later in detail with reference to the simulation result, the throughput and the end-to-end delay time can be improved as compared with the prior art even if the number of hops increases.

FIG. 29 shows omnidirectional radio communication, where the node radio station N _A has a transmission area A _t1 and the node radio station N _B has a reception area A _r1 determined by the receiver sensitivity. . Further, the node radio station N _A has a carrier detection area A _c1 determined by the receiver threshold value, and generally A _c1 > A _t1 . Further, FIG. 30 shows directional wireless communication according to the second embodiment. According to the IEEE 802.11 _standard , a node radio station existing in the carrier detection area A _c1 must remain in an idle state while radio communication between the node radio stations N _A and N _B is in progress. When using an omni-pattern antenna, if any node radio station in the carrier wave detection area A _c1 , for example, the node radio station N _C starts communication during radio communication between the node radio stations N _A and N _B , since the node radio station N _B is in the omnidirectional reception state, the interference nodes radio station N _B is generated, which is necessary. However, as shown in FIG. 30 according to the present embodiment, the use of directional antennas, the node radio station N _B rotates toward the receiving area A _r2 determined by the sector pattern to the node radio station N _A, other In all directions, nulls can be formed, and the chance of interference from other directions is minimized. In this case, also the node radio station N _C starts to wireless communications, there is no possibility that the radio signal of the node radio station N _C generates the interference at the node radio station N _B.

  Here, each wireless station transmits wirelessly using a sector pattern, and each wireless station mutually receives a receiver sensitivity (a wireless signal modulated by the receiver is substantially error-free as shown in FIG. 30). The reception signal level that can be demodulated is set to be substantially equal to the receiver threshold value (referred to as the signal level threshold value when the presence or absence of a radio signal is determined in the receiver) Is preferred. Therefore, when an antenna having a directional sector pattern is used, wireless communication can be performed simultaneously on two wireless links as shown in FIG. 22 by equalizing the receiver sensitivity and the receiver threshold value. In addition, the SDMA efficiency can be greatly improved. Therefore, the node radio station is silenced only by radio signals that can be received and decoded by the node radio station.

  The present inventors performed a simulation as follows for the wireless communication system according to the second embodiment, and obtained the following results. Here, using the Qualnet 3.1 (see Non-Patent Document 12), in the string topology, the MAC protocol proposed by the present inventors called “E-MAC” and “IEEE802.11 (omnidirectional)” A comparative evaluation was made between the omni-directional IEEE 802.11, designated as "D", and the conventional directional MAC protocol, designated as "D-MAC". In D-MAC, RTS, CTS, DATA, and ACK packets are transmitted using a sector pattern that is a directivity pattern. Stationary node radio stations that are not in radio communication are separated by a distance of 300 m. 1024-byte CBR packets are transmitted at 5.4 millisecond intervals at data rates in excess of 2 Mbps. The duration of the preceding tone signal in the RTS / CTS / beacon signal is 200 microseconds.

  First, evaluation was performed in an ideal case where the directivity gain is equal to the omnidirectional gain. The results in FIGS. 23 and 24 show that E-MAC performs much better than D-MAC and its performance is comparable to that of IEEE 802.11 (omnidirectional). Due to hidden terminals and deafness problems as pointed out in Non-Patent Document 4, D-MAC has low performance in string topology. However, E-MAC performs better than IEEE 802.11 (omnidirectional) as the number of hops increases. However, in reality, the directivity gain of the antenna is larger than the omnidirectional gain. Therefore, the inventors evaluated an E-MAC having a directional gain of 5.4 dBi that is greater than the omnidirectional gain. As in the case of IEEE 802.11, the receiver sensitivity (RS) is kept below the receiver threshold (RT). The graph “E-MAC (RS <RT)” indicates that the performance of the E-MAC does not deteriorate even when the antenna gains are not equal.

As described with reference to FIGS. 29 and 30, according to the MAC protocol according to the IEEE 802.11 standard, the wireless communication between the node wireless stations N _A and N _B is in progress in the carrier detection area A _c1 . Node radio stations can only exist involuntarily. If start wireless communication is in progress wireless communication between the carrier detection area A _c1 in the example node radio station N _C is any node radio stations Node radio station N _A, N _B, the node radio station N _B is since the interference occurs at the node radio station N _B to have received omnidirectionally, it is necessary to use an omni pattern antenna. However, the use of directional antennas, the node radio station N _B is be capable of rotating the sector pattern towards the node radio station N _A, a null is formed to all other directions, thus The opportunity for interference from other directions is minimized. Now, even if the node radio station N _C starts radio communication, the radio signal from the node radio station N _C can not make interference in the node radio station N _B. Therefore, the efficiency of SDMA can be improved by using directional antennas and making receiver sensitivity and receiver threshold value substantially equal. Therefore, the node radio station is kept in silence only by radio signals having signal strengths that are received and decoded by the node radio station.

  In FIG. 25 and FIG. 26, the graph of “E-MAC (RS = RT)” shows the improvement of the gain of E-MAC in the string topology, which is almost the same as the case of “IEEE802.11 (omnidirectional)”. 2 times. As is clear from FIGS. 27 and 28, the E-MAC is also used in a parallel topology in which the maximum gain obtained is about four times that of “IEEE802.11 (omnidirectional)”. Direction)).

  As described above, according to the present embodiment, it is possible to hold direction information by using the direction-directing method of receiver directivity, and omnidirectional RTS / CTS having DNAV is an exposed terminal problem. And an effective directional MAC protocol that is effective for the hidden terminal problem. When the receiver sensitivity and the receiver threshold are equal, the throughput can be improved by 2 times in the string topology and 4 times in the parallel topology compared to the conventional omnidirectional IEEE 802.11. is there.

1 is a plan layout diagram of a plurality of radio stations 1-1 to 1-9 that constitute an ad hoc radio network according to a first embodiment of the present invention. FIG. 2 is a block diagram showing an internal configuration of each wireless station 1 in FIG. 1. It is a figure which shows an example of the sector beam pattern of the variable beam antenna 101 of FIG. It is a figure which shows the format of the packet data used in the ad hoc wireless network of FIG. 3 is a table showing an example of an azimuth and signal intensity level table (AS table) stored in the database memory 154 of FIG. 2. It is a table | surface which shows an example of the DNAV control table stored in the database memory 154 of FIG. 2, and used in the modification of 1st Embodiment. 2 is a timing chart showing transmission / reception processing of tone signals and packet signals used in the ad hoc wireless network of FIG. 1. It is a timing chart which shows the kind of radiation pattern and radio | wireless communication protocol in each node radio station used in 1st Embodiment. It is a timing chart which shows the kind of radiation pattern and radio | wireless communication protocol in each adjacent neighboring radio station used in the modification of 1st Embodiment. In a 1st embodiment, it is a top view showing a radiation pattern of each node radio station in a radio communications system which has improved SDMA efficiency using a directional antenna. It is a block diagram which shows the structural example of the control apparatus of the array antenna using the array antenna apparatus 100 which is an electronically controlled waveguide array antenna apparatus used in 1st Embodiment. It is a longitudinal cross-sectional view of the array antenna apparatus 100 of FIG. FIG. 11A is a plan view of a radiation pattern when the azimuth angle Ad = 0 degrees of the array antenna control apparatus 100 of FIG. 11, showing various different antenna radiation patterns used in the simulation of the first embodiment. FIG. 11B is a plan view of a radiation pattern when the azimuth angle Ad = 30 degrees of the array antenna control apparatus 100 of FIG. 11, and FIG. 10C shows a radiation pattern of a default switching antenna in a known qualnet. It is a top view, (d) is a top view which shows the radiation pattern of an ideal directional antenna. It is a top view for demonstrating the DNAV method used in the modification of 1st Embodiment. It is a state transition diagram which shows the radio | wireless communication control process performed by the management control part 151 of FIG. In the first embodiment, the reception threshold when the radio wave from the transmission radio station N _n is captured by the reception radio station N _m is sufficient to allow an interference wave from another transmission radio station N _p. It is a top view for demonstrating when it is high. It is a simulation result of 1st Embodiment, Comprising: It is a graph which shows the average throughput with respect to a data rate when using various antennas. It is a simulation result of 1st Embodiment, Comprising: It is a graph which shows the 1 hop average end-to-end delay time with respect to the data rate when using various antennas. It is a simulation result of 1st Embodiment, Comprising: It is a graph which shows the average throughput with respect to the number of simultaneous communications when using various antennas. It is a simulation result of 1st Embodiment, Comprising: It is a graph which shows the average end-to-end delay time of 1 hop with respect to the number of simultaneous communications when using various antennas. It is a top view of each radio station which performs multihop radio communication control processing in an ad hoc radio network concerning a 2nd embodiment. FIG. 22 is a plan view of each wireless station for describing the operational effects in the multi-hop wireless communication control process of FIG. 21. It is a simulation result of 2nd Embodiment, Comprising: The average throughput with respect to the number of hops when the gain of a directional antenna is equal to the gain of an omni pattern antenna in a string topology when using various wireless MAC communication control procedures It is a graph. FIG. 6 is a simulation result of the second embodiment, and when using various wireless MAC communication control procedures, the average end-to-hop with respect to the number of hops when the gain of a directional antenna is equal to the gain of an omni-pattern antenna in a string topology. -It is a graph which shows end delay time. The simulation results of the second embodiment show the average throughput with respect to the number of hops when the gain of the directional antenna is larger than the gain of the omni pattern antenna in the string topology when various wireless MAC communication control procedures are used. It is a graph to show. The simulation results of the second embodiment, when using various wireless MAC communication control procedures, the average end hop count with respect to the number of hops when the gain of the directional antenna is larger than the gain of the omni pattern antenna in the string topology It is a graph which shows a two end delay time. The simulation results of the second embodiment show the average throughput with respect to the number of hops when the gain of the directional antenna is larger than the gain of the omni-pattern antenna in the parallel topology when various wireless MAC communication control procedures are used. It is a graph to show. The simulation result of the second embodiment, when using various wireless MAC communication control procedures, the average end hop count with respect to the number of hops when the gain of the directional antenna is larger than the gain of the omni pattern antenna in the parallel topology. It is a graph which shows a two end delay time. FIG. 10 is a plan view showing a transmission area A _t1 , a reception area A _r1 and a carrier wave detection area A _c1 when an omni pattern antenna is used in the second embodiment. FIG. 10 is a plan view showing a transmission area A _t1 , a reception area A _r1, and a carrier wave detection area A _c1 when a directional antenna is used in the second embodiment.

Explanation of symbols

A0: Excitation element,
A1 to A6 ... non-excited elements,
N S _... originating radio station,
N _D ... destination radio station,
N _X , N _Y ... adjacent radio stations,
1, 1-1 to _{1-9,1-i, 1-j,} 1-k, N s, N r, N n, N m, N p, N q, N A, N B, N C ... node Radio station,
1L ... Low noise amplifier (LNA),
2 ... Down converter,
3 ... A / D converter,
4 ... demodulator,
5 ... Coaxial cable for feeding,
6 ... circulator,
7 ... Wireless transmitter,
11: Ground conductor,
12-1 to 12-6 ... variable reactance element,
20 ... Adaptive control type controller,
21 ... Learning sequence signal generator,
100: Array antenna device.
101 ... Variable beam antenna,
102 ... circulator,
103 ... Direction control unit,
104 ... packet transmission / reception unit,
105 ... Traffic monitor section,
106 ... line control unit,
107 ... upper layer processing apparatus,
130: Packet receiver,
131 ... high frequency receiver,
132: demodulator,
133: Receive buffer memory,
140 ... packet transmitter,
141. Transmission timing control unit,
142 ... transmission buffer memory,
143 ... modulator,
144 ... high frequency transmitter,
151... Management control unit,
152 ... Search engine,
153 ... Update engine,
154 ... Database memory,
155 ... Clock circuit,
160. Spread code generator.

Claims (4)

A plurality of radio stations each including an antenna capable of forming both a sector pattern having a predetermined beam width and an omnidirectional beam pattern, and a source radio station and a destination radio station of the plurality of radio stations In a control method for a wireless network that performs wireless communication with multiple hops between
A communication start control signal (RTS: Request To Send) from the transmission source and a communication reception signal (CTS: Clear To Send) from the reception source are both transmitted by the omnidirectional antenna, and the data signal (DATA) and reception are completed. Transmitting a notification signal (ACK: Acknowledge) with directivity;
After detecting a radio signal from another radio station using an omni pattern or sector pattern and rotating the beam direction of the antenna over all azimuth angles using the sector pattern to search for the azimuth angle with the maximum signal strength And a wireless network control method comprising a step of prohibiting wireless communication using a sector pattern with respect to an azimuth angle of the wireless station when the detected wireless signal is not a wireless station performing wireless communication. .   2. The radio according to claim 1, wherein each radio station performs radio transmission using a sector pattern, and the receiver sensitivity and the receiver threshold are set to be substantially equal to each other in each radio station. Control method for the network. A plurality of radio stations each including an antenna capable of forming both a sector pattern having a predetermined beam width and an omnidirectional beam pattern, and a source radio station and a destination radio station of the plurality of radio stations In a control device for a wireless network that performs wireless communication with multiple hops between
A communication start control signal (RTS: Request To Send) from the transmission source and a communication reception signal (CTS: Clear To Send) from the reception source are both transmitted by the omnidirectional antenna, and the data signal (DATA) and reception are completed. Means for transmitting a notification signal (ACK: Acknowledge) with directivity;
After detecting a radio signal from another radio station using an omni pattern or sector pattern and rotating the beam direction of the antenna over all azimuth angles using the sector pattern to search for the azimuth angle with the maximum signal strength And a means for prohibiting wireless communication using a sector pattern with respect to the azimuth angle of the wireless station when the detected wireless signal is not a wireless station performing wireless communication. Control device. 4. The radio according to claim 3, wherein each radio station performs radio transmission using a sector pattern, and the receiver sensitivity and the receiver threshold are set to be substantially equal to each other in each radio station. Control device for the network.

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