JP2005079985A - Wireless communication system, wireless communication apparatus and wireless communication method, and computer program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To form an appropriate ad hoc network suitably without interference among communication stations under such a communication environment as a plurality of channels are prepared. <P>SOLUTION: Even when communication conditions of a specific channel are bad, communication can be carried out using other communication channel by altering the channel periodically. Consequently, average communication conditions are improved as compared with a case where the specific channel is used continuously. When the method for altering the channel regularly is employed, a mechanism for determining and notifying a communication channel between terminals is not required and the operation is simplified. CSMA/CA system packet communication can be realized under autonomous distributed communication environment where each terminal transmits its own beacon. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a wireless communication system, a wireless communication apparatus, a wireless communication method, and a computer program that communicate with each other between a plurality of wireless stations such as a wireless LAN (Local Area Network), and more particularly to a control station. The present invention relates to a wireless communication system, a wireless communication apparatus and a wireless communication method, and a computer program in which a wireless network is constructed by ad-hoc communication without any particular device.

  More specifically, the present invention relates to wireless communication that forms an autonomous decentralized wireless network without the intervention of a specific control station without interference between neighboring wireless systems in a communication environment in which a plurality of channels are prepared. The present invention relates to a system, a wireless communication apparatus, a wireless communication method, and a computer program. In particular, each communication station preferably selects its own beacon transmission channel or a beacon reception channel from an adjacent station, and intervenes in the control station or changes the channel The present invention relates to a wireless communication system, a wireless communication apparatus, a wireless communication method, and a computer program that realize multi-channel communication operation by autonomous distributed control without a special mechanism for notifying the user.

  As a system for releasing a user from a wired LAN connection, a wireless LAN has attracted attention. According to the wireless LAN, most of the wired cables can be omitted in a work space such as an office, so that a communication terminal such as a personal computer (PC) can be moved relatively easily. In recent years, the demand for wireless LAN systems has increased remarkably with the increase in speed and cost. Particularly recently, introduction of a personal area network (PAN) has been studied in order to construct a small-scale wireless network between a plurality of electronic devices existing around a person and perform information communication. For example, different radio communication systems and radio communication apparatuses are defined using frequency bands that do not require a license from a supervisory agency, such as 2.4 GHz band and 5 GHz band.

  One standard for wireless networks is IEEE (The Institute of Electrical and Electronics Engineers) 802.11 (for example, see Non-Patent Document 1), HiperLAN / 2 (for example, Non-Patent Document 2 or Non-Patent Document 2 or Non-Patent Document 2). (See Patent Document 3), IEEE 302.15.3, Bluetooth communication, and the like. As for the IEEE802.11 standard, there are various wireless communication systems such as the IEEE802.11a standard, the IEEE802.11b standard, etc., depending on the wireless communication system and the frequency band to be used.

  In order to configure a local area network using wireless technology, a single device serving as a control station called an “access point” or “coordinator” is provided in the area, and is under the overall control of this control station. A method of forming a network is generally used.

  In a wireless network in which an access point is arranged, when information is transmitted from a certain communication device, a bandwidth necessary for the information transmission is first reserved in the access point so that there is no collision with information transmission in another communication device. In this way, an access control method based on bandwidth reservation that uses a transmission line is widely adopted. That is, by arranging access points, synchronous wireless communication is performed in which communication devices in a wireless network are synchronized with each other.

  However, when asynchronous communication is performed between the communication device on the transmission side and the reception side in a wireless communication system in which an access point exists, wireless communication via the access point is always required. There is a problem that the efficiency is halved.

  On the other hand, as another method of configuring a wireless network, “ad-hoc communication” in which terminals perform wireless communication directly and asynchronously has been devised. In particular, in a small-scale wireless network composed of a relatively small number of clients located in the vicinity, ad-hoc communication that allows any terminal to perform asynchronous wireless communication directly without using a specific access point is provided. It seems to be appropriate.

  By the way, in the work environment in which information devices such as personal computers (PCs) are widespread and many devices are mixed in an office, it is assumed that communication stations are scattered and a plurality of networks are overlapped. The Under such circumstances, in the case of a wireless network using a single channel, there is no room for repairing the situation even if another system interrupts during communication or communication quality deteriorates due to interference or the like.

  For this reason, in a conventional wireless network system, a plurality of frequency channels are prepared for coexistence with other networks, and one frequency channel used in a wireless communication device serving as an access point is selected and operated. The method of starting is generally adopted. For example, in a standard such as IEEE 802.11h, a mechanism for dynamically changing a channel (DFS: Dynamic Frequency Select) is being studied.

  According to such a multi-channel communication method, when other systems can interrupt during communication or communication quality deteriorates due to interference or the like, the network operation is maintained by switching the frequency channel to be used, Coexistence with other networks can be realized.

  For example, even in an IEEE 802.15.3 high-speed wireless PAN system, a plurality of frequency channels that can be used in the system are prepared, and a wireless communication device transmits a beacon signal as a piconet coordinator (PNC) to the surroundings after power-on In order to confirm the presence or absence of a device, an algorithm is adopted in which a frequency channel to be used is selected by performing a scanning operation over all available channels.

  In an autonomous decentralized ad hoc network that does not have a control station, resource management for frequency channels is important in order to minimize interference with different wireless networks operating in the vicinity. However, in order to simultaneously switch the frequency channels used in the network, it is necessary for a representative station called a coordinator or an access point to instruct each terminal station about the channel to be used. In other words, it is difficult to switch frequency channels in an ad hoc network.

  Taking HiperLAN / 2 as an example, in order to use a plurality of frequency channels properly, a method of switching channels all at once has been considered. For example, an AP (base station) that is a central control station repeatedly notifies that the frequency channel is to be changed, and at a certain timing, the AP and an MT (mobile station) connected to the AP simultaneously switch channels. The decision as to whether or not to switch is determined by the AP. Information for determination is accumulated by following the processing procedure shown below. That is,

(1) In response to an instruction from the AP, the currently connected MT temporarily stops communication, scans another frequency channel, evaluates channel quality, and reports the result to the AP.
(2) In response to an instruction from the AP, the AP temporarily stops transmission of the broadcast channel, the connected MT scans the frequency channel currently in use and performs channel quality evaluation, and reports the result to the AP.

  Further, in Bluetooth communication, a method is used in which each frequency channel is used fairly by performing frequency hopping randomly based on a central control station called a master. In order to configure a network, the existence of a central control station called a master is indispensable, which is a reference for frequency channel hopping patterns and synchronization in the time axis direction. When the master disappears, the network formed so far is temporarily disconnected, and a process for selecting a new master is required.

  In addition, in an IEEE802.11 wireless LAN system, a network is formed by using a frequency channel initially set by an access point, so it is difficult to construct an ad hoc network without arranging a base station. It is. When communicating with a wireless communication device (terminal) accommodated in an AP operating on another frequency channel, the APs must be connected to each other by, for example, a wired LAN cable. That is, if the accommodated APs are not connected to each other, communication cannot be performed even if the wireless communication apparatuses (terminals) that are physically adjacent to each other are accommodated in different APs.

  Also, in the IEEE 802.15.3 high-speed wireless PAN system, it is possible to scan all frequency channels first and search for coordinators existing in the vicinity. If this is started, it is impossible to grasp the usage status of other frequency channels. For this reason, even if there is a piconet with a different frequency channel used in the vicinity, communication with a wireless communication apparatus connected to the piconet cannot be performed.

  As described above, in the conventional method, in order to determine the frequency channel switching timing, the setup process realized by message exchange or the like so that the participating terminals can start the frequency channel switching operation in synchronization with each other. A complicated mechanism such as mediation processing is required. In addition, the existence of a central control station such as an AP in IEEE802.11 or HiperLAN / 2 and a master in Bluetooth communication, which performs control mainly, is essential. If a central control station such as an AP or master disappears, some protocol processing or artificial setting change work is required to select a central control station to replace it, and communication is interrupted during that processing. There is a problem.

  In addition, since the locations used by the terminals are different, it is expected that the interference received varies from terminal to terminal. In this case, in a method in which all terminals move to one common channel all at once, there is a possibility that an inconvenient channel is selected because there is much interference for a certain terminal.

  For example, the interference of the own channel has been proposed not only for measurement but also for a wireless communication system that determines the frequency channel by measuring interference when an adjacent channel is used (see, for example, Patent Document 1). This is a system in which multi-channel is realized by intervening base stations.

  In addition, a method is conceivable in which a communication station designates a traffic reception channel by transmitting a beacon using a channel optimal for the local station. However, even a channel that is optimal for the local station may be a channel that is receiving interference for a communication station that receives the beacon. For example, if the beacon transmission channel of one station is an interference channel or an unusable channel because the communication quality deteriorates in the other station, these communication stations may communicate with each other on the other channel. Even if they can, they will fall into a deadlock state where they cannot recognize each other's existence forever.

JP-A-6-37762 International Standard ISO / IEC 8802-11: 1999 (E) ANSI / IEEE Std 802.11, 1999 Edition, Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layers (PH) ETSI Standard ETSI TS 101 761-1 V1.3.1 Broadband Radio Access Networks (BRAN); HIPERLAN Type 2; Data Link Control (DLC) Layer; Part1: BasicControl ETSI TS 101 761-2 V1.3.1 Broadband Radio Access Networks (BRAN); HIPERLAN Type 2; Data Link Control (DLC) Layer; Part2: Radio Link Control (LC)

  An object of the present invention is to provide an excellent radio communication system and radio communication capable of suitably forming an appropriate ad hoc network without interfering with each other in a communication environment in which a plurality of channels are prepared. An apparatus, a wireless communication method, and a computer program are provided.

  A further object of the present invention is to provide an excellent radio communication system, radio capable of performing channel access by effectively using a plurality of frequency channels in an autonomous distributed radio network that does not require a specific control station. To provide a communication device, a wireless communication method, and a computer program.

  A further object of the present invention is to provide an excellent wireless communication system and wireless communication apparatus capable of avoiding a deadlock state in which each communication station cannot recognize each other's existence and forming an autonomous distributed multi-channel wireless network. And a wireless communication method, and a computer program.

  A further object of the present invention is that each communication station preferably selects its own beacon transmission channel and a beacon reception channel from an adjacent station, and uses autonomous distributed control without a special mechanism for notifying the intervention of the control station or channel change. An object is to provide an excellent wireless communication system, wireless communication apparatus, wireless communication method, and computer program capable of realizing multi-channel communication operation.

The present invention has been made in consideration of the above-mentioned problems. The first aspect of the present invention is that ad hoc communication is performed by a plurality of wireless communication devices without a control station in a communication environment in which a plurality of channels are prepared. A wireless communication system forming a network based on communication,
Each communication station transmits a beacon at a predetermined beacon period while sequentially switching its own beacon transmission channel from the plurality of channels at a predetermined time interval.
This is a wireless communication system.

  However, “system” here refers to a logical collection of a plurality of devices (or functional modules that realize specific functions), and each device or functional module is in a single housing. It does not matter whether or not.

  Each communication station changes the beacon transmission channel according to a predetermined selection rule with reference to the initial channel. Here, by making the channel selection rule for changing the beacon transmission channel the same in all communication stations, each communication station can grasp the beacon transmission time and beacon transmission channel of the adjacent station by autonomous distributed control. That is, each communication station obtains the next beacon transmission channel based on the beacon reception timing from the adjacent station and the initial channel information, and waits for reception in accordance with the beacon transmission timing of the adjacent station on the channel. Good.

  Therefore, according to the present invention, even when communication on a certain channel is difficult due to interference or the like, communication is possible by periodically changing the channel. In addition, since a procedure for deciding a communication channel between communication stations is unnecessary, a simple operation can be realized, and unnecessary communication is reduced, so that the throughput of the entire system is improved.

  Here, each communication station may transmit a beacon including channel quality information describing the communication quality of each channel for the own station.

  In addition, when the communication station determines that transmission on a specific channel is difficult, the communication station may continuously select the next or previous channel on the selection rule. In such a case, the adjacent station recognizes the skip of channel change in the beacon transmission side communication station based on the channel quality information described in the beacon of the beacon transmission side communication station, and What is necessary is just to wait for reception of a beacon on the previous channel.

  In addition, when there is a channel that is determined to be difficult to receive in the adjacent station based on the channel quality information described in the beacon from the adjacent station, the communication station changes the channel according to the selection rule. It is also possible to skip (that is, avoid beacon transmission on a channel that is difficult to receive at an adjacent station) and continuously select the next or previous channel. In addition, the adjacent station on the beacon receiving side also recognizes the skip of channel change in the communication station on the beacon transmitting side based on the channel quality information of its own station, and the next or previous time on the selection rule. Wait for beacons to be received on the channel.

  As a result, it is possible to prevent a decrease in average throughput by performing communication while avoiding channels having poor communication quality in both transmitting and receiving terminal stations.

A second aspect of the present invention provides a computer-readable format for executing a process for performing autonomous distributed communication operation in a wireless communication environment in which a plurality of channels are prepared on a computer system. A written computer program comprising:
A beacon signal generating step for generating a beacon signal describing information about the own station;
A communication channel setting step for setting a beacon signal transmission channel of the own station and a beacon signal reception channel from a peripheral station,
A control step for controlling a communication operation on the channel set by the communication channel setting step;
A beacon signal analyzing step for analyzing a beacon signal received from an adjacent station;
With
In the communication channel control step, the own beacon transmission channel is sequentially switched at a predetermined time interval from the plurality of channels.
This is a computer program characterized by the above.

  The computer program according to the second aspect of the present invention defines a computer program described in a computer-readable format so as to realize predetermined processing on a computer system. In other words, by installing the computer program according to the second aspect of the present invention in the computer system, a cooperative action is exhibited on the computer system, and it operates as a wireless communication device. By activating a plurality of such wireless communication devices to construct a wireless network, it is possible to obtain the same effects as the wireless communication system according to the first aspect of the present invention.

  According to the present invention, in a communication environment in which a plurality of channels are prepared, an excellent ad hoc network can be suitably formed without causing communication stations to interfere with each other. An apparatus, a wireless communication method, and a computer program can be provided.

  Further, according to the present invention, in an autonomous decentralized wireless network that does not require a specific control station (access point, base station, master station, etc.), channel access can be made by effectively using a plurality of frequency channels. An excellent wireless communication system, wireless communication apparatus, wireless communication method, and computer program can be provided.

  Further, according to the present invention, an excellent wireless communication system and wireless communication capable of forming an autonomous distributed multi-channel wireless network by avoiding a deadlock state in which each communication station cannot recognize each other's existence. An apparatus, a wireless communication method, and a computer program can be provided.

  According to the present invention, even when communication on a certain channel is difficult due to interference or the like, communication is possible by periodically changing the channel. In addition, since a procedure for deciding a communication channel between communication stations is not required, a simple operation can be realized, and unnecessary communication is reduced, so that the throughput of the entire system is improved.

  In the wireless communication network according to the present invention, each communication station can receive the beacon by grasping the beacon transmission time and the beacon transmission channel of the adjacent station by autonomous distributed control.

  Also, according to the present invention, by making the next communication channel selection rule the same for all communication stations, if there is information on the channel of the initial beacon, the beacon channel that changes between terminals can be known between terminals. It is possible to match the channels on the transmission side and the reception side.

  Further, according to the present invention, each communication station transmits the beacon information including its own channel quality information. Therefore, when it is judged that transmission on a certain channel is difficult, the transmitting station side skips the channel change and transmits the beacon on the next channel or the same channel as the previous time, and accordingly the receiving station side Then, based on the channel quality information described in the beacon from the transmitting station, the channel change skip is recognized and reception is waited on the change destination channel. On the transmitting station side, the channel change destination is selected based on the channel information described in the beacon from the receiving station side, and transmission is performed. Wait for reception. As a result, it is possible to prevent a decrease in average throughput by performing communication while avoiding channels having poor communication quality in both transmitting and receiving terminal stations.

  Other objects, features, and advantages of the present invention will become apparent from more detailed description based on embodiments of the present invention described later and the accompanying drawings.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

A. System Configuration The propagation path of communication assumed in the present invention is wireless, and a network is constructed among a plurality of communication stations using a transmission medium composed of a plurality of frequency channels. Further, the communication assumed in the present invention is a storage and exchange type traffic, and information is transferred in units of packets.

  The wireless network system according to the present invention has an autonomous distributed system configuration in which no coordinator is arranged, and transmission control that effectively uses a plurality of channels by a transmission (MAC) frame having a gradual time division multiple access structure. Is done. Each communication station can also perform ad hoc communication in which information is directly and asynchronously transmitted according to an access procedure based on CSMA (Carrier Sense Multiple Access).

  In this way, in a wireless communication system in which no control station is particularly arranged, each communication station broadcasts beacon information on a beacon transmission channel that is appropriately selected, so that other communication stations in the vicinity (that is, within the communication range) can communicate their own information. Notify existence and notify network configuration. In addition, a communication station that newly enters the communication range of a certain communication station detects that it has entered the communication range by receiving a beacon signal, and decodes information described in the beacon to configure the network configuration Can know. Also, since the communication station transmits a beacon at the beginning of the transmission frame period, the transmission frame period in each channel used by each communication station is defined by the beacon interval.

  Here, in a multi-channel communication environment, when each communication apparatus transmits a beacon only on a specific channel, there is a problem that a communication station that cannot transmit a beacon appears. For example, when a communication station selects a beacon transmission channel based on its own station, such as communication quality is good for its own station, even if it is the optimum channel for its own station, the communication station receiving the beacon receives interference. Channel. Even if these communication stations can communicate with each other on other channels, they fall into a deadlock state in which they cannot recognize each other forever.

  Therefore, in the present embodiment, each wireless communication apparatus determines one of the prepared channels as an initial channel, and changes the beacon transmission channel according to a predetermined selection rule with reference to the initial channel. I tried to go. Here, by making the channel selection rule for changing the beacon transmission channel the same in all communication stations, each communication station grasps the beacon transmission time and beacon transmission channel of the adjacent station by autonomous distributed control, and Since it can be received, a deadlock condition is avoided. Details of this mechanism will be described later.

  The processing in each communication station described below is basically processing executed in all communication stations that enter the ad hoc network according to the present invention. However, depending on the case, not all communication stations configuring the network execute the processing described below.

  FIG. 1 shows an arrangement example of communication devices constituting a wireless communication system according to an embodiment of the present invention. In this wireless communication system, a specific control pole is not disposed, and each communication device operates in an autonomous and distributed manner to form an ad hoc network. In the figure, a state where communication devices # 0 to # 6 are distributed in the same space is shown.

  In addition, the communication range of each communication device is indicated by a broken line in the same figure, and is defined as a range in which signals transmitted by itself can interfere with each other as well as communication with other communication devices within the range. That is, the communication device # 0 is in a range in which communication is possible with communication devices # 1, # 4 in the vicinity, and the communication device # 1 is in a range in which communication is possible with communication devices # 0, # 2, # 4 in the vicinity. The communication device # 2 is in a range in which communication with the communication devices # 1, # 3, and # 6 in the vicinity is possible, and the communication device # 3 is in a range in which communication is possible with the communication device # 2 in the vicinity. , Communication device # 4 is in a range where it can communicate with neighboring communication devices # 0, # 1, # 5, and communication device # 5 is within a range where it can communicate with neighboring communication device # 4. Device # 6 is in a range where it can communicate with communication device # 2 in the vicinity.

  When communication is performed between specific communication devices, there is a communication device that can be heard from one communication device that is a communication partner but cannot be heard from the other communication device, that is, a “hidden terminal”.

  FIG. 2 schematically shows a functional configuration of a wireless communication apparatus that operates as a communication station in a wireless network according to an embodiment of the present invention. The illustrated wireless communication apparatus performs appropriate channel access within the same wireless system in a communication environment in which a plurality of channels are prepared, so that appropriate ad hoc communication can be performed without interfering with other wireless systems. A network can be formed.

  The wireless communication device 100 includes an interface 101, a data buffer 102, a central control unit 103, a beacon generation unit 104, a wireless transmission unit 106, a timing control unit 107, a channel setting unit 108, an antenna 109, The wireless reception unit 110, the channel quality measurement unit 111, the beacon analysis unit 112, and the information storage unit 113 are included.

  The interface 101 exchanges various types of information with an external device (for example, a personal computer (not shown)) connected to the wireless communication apparatus 100.

  The data buffer 102 is used to temporarily store data sent from a device connected via the interface 101 and data received via the wireless transmission path before sending the data via the interface 101. The

  The central control unit 103 centrally performs a series of information transmission and reception processing management and transmission path access control (multi-channel scan setting, channel setting, etc.) in the wireless communication apparatus 100.

  The beacon generation unit 104 generates a beacon signal that is periodically exchanged with a nearby wireless communication device. In order for radio communication apparatus 100 to operate a radio network, its own beacon transmission slot position in each channel, its own reception slot position in each channel, beacon reception slot position from a neighboring communication apparatus in each channel, each channel Stipulates its own scan operation cycle. These pieces of information are stored in the information storage unit 113, and are described in a beacon signal to notify surrounding wireless communication devices. In the present embodiment, channel quality information related to the communication quality of each channel measured at the own station, and further, channel quality information extracted from the beacon signal of the adjacent station are described in the beacon. . The configuration of the beacon signal will be described later. Since the wireless communication device 100 transmits a beacon at the beginning of the transmission frame cycle, the transmission frame cycle in each channel used by the wireless communication device 100 is defined by the beacon interval.

  The wireless transmission unit 106 performs predetermined modulation processing to wirelessly transmit data and beacon signals temporarily stored in the data buffer 102.

  The antenna 109 wirelessly transmits a signal addressed to another wireless communication device on a selected frequency channel, or collects a signal transmitted from the other wireless communication device. In this embodiment, it is assumed that a single antenna is provided and that transmission and reception cannot be performed in parallel. Also, it is assumed that a plurality of frequency channels cannot be handled at the same time.

  The wireless receiving unit 110 receives and processes signals such as information and beacons sent from other wireless communication devices at a predetermined time. As a wireless transmission / reception method in the wireless transmission unit 106 and the wireless reception unit 110, various communication methods suitable for relatively short-distance communication applicable to a wireless LAN, for example, can be applied. Specifically, an Ultra Wide Band (UWB) system, an Orthogonal Frequency Multiplexing (OFDM) system, a Code Division Multiple Access (CDMA) system, or the like can be employed.

  For example, the channel quality measurement unit 111 analyzes a signal received from an adjacent station, measures the communication quality of each channel in the own station, and stores the measurement result in the information storage unit 113 as channel quality information.

  The channel setting unit 108 selects a channel to be used when actually transmitting / receiving a multi-channel radio signal. For example, when transmitting a beacon signal, the beacon transmission channel is changed according to a predetermined selection rule with the initial channel as a reference.

  Here, by making the channel selection rule for changing the beacon transmission channel the same in all communication stations, each communication station grasps the beacon transmission time and beacon transmission channel of the adjacent station by autonomous distributed control, and Can be received (described later). If it is determined that transmission / reception on a certain channel is difficult based on the channel quality information of its own station or adjacent station, the channel change is skipped according to the above selection rule, and the next or previous Channels are continuously selected (described later).

  The timing control unit 107 controls timing for transmitting and receiving a radio signal on the channel set by the channel setting unit 108. For example, it controls its own beacon transmission timing at the beginning of the transmission frame cycle in the beacon transmission channel, beacon reception timing from other communication devices in each channel, scan operation cycle in each channel, and the like.

  The beacon analysis unit 112 analyzes a beacon signal that can be received from an adjacent station, and analyzes the presence of a nearby wireless communication device. For example, information such as beacon reception timing, initial channel information, and neighboring beacon reception timing of neighboring stations is stored in the information storage unit 113 as neighboring device information. Further, the channel quality information described in the beacon is also stored in the information storage unit 113.

  The information storage unit 113 executes an execution procedure instruction (a program for performing scan setting, channel setting, etc.) such as a series of access control operations executed in the central control unit 103, beacon transmission timing of other communication stations, and channel quality information. Store neighboring device information.

  In this embodiment, the wireless communication apparatus 100 operating as a communication station has a transmission (MAC) frame having a gradual time division multiple access structure in a communication environment in which a plurality of channels are prepared and a specific control station is not arranged. Thus, communication operation such as transmission control using a plurality of channels effectively or random access based on CSMA / CA is performed.

  Each communication station reports its beacon information while changing the beacon transmission channel according to a predetermined selection rule with reference to the initial channel, so that other communication stations in the vicinity (that is, within the communication range) can identify themselves. Notify and notify network configuration. In addition, a communication station that newly enters the communication range of a certain communication station detects that it has entered the communication range by receiving a beacon signal, and decodes information described in the beacon to configure the network configuration Can know.

  A beacon transmission procedure of each communication station according to the present embodiment will be described with reference to FIG. However, here, a case where beacons of respective communication stations are arranged on a single channel will be described first.

  If the information transmitted by the beacon is 100 bytes, the time required for transmission is 18 microseconds. Since transmission is performed once every 40 milliseconds, the media occupation rate of the beacon for each communication station is as small as 1/22222.

  Each communication station synchronizes gently while listening to beacons that oscillate in the vicinity. When a new communication station appears, the new communication station sets its own beacon transmission timing so that it does not collide with the beacon transmission timing of the existing communication station.

  When there is no communication station in the vicinity, the communication station 01 can start transmitting a beacon at an appropriate timing. The beacon transmission interval is 40 milliseconds (described above). In the example shown at the top in FIG. 2, B01 indicates a beacon transmitted from the communication station 01.

  Thereafter, the communication station that newly enters the communication range sets its own beacon transmission timing so as not to collide with the existing beacon arrangement. At this time, since each communication station acquires a preferential use area (TGP) immediately after beacon transmission, the beacon transmission timing of each communication station is evenly distributed within the transmission frame period on one channel rather than being dense. Dispersion is more preferable in terms of transmission efficiency. Therefore, in this embodiment, beacon transmission is started in the middle of the time zone in which the beacon interval is the longest in the range where the user can hear it.

  For example, it is assumed that a new communication station 02 appears on a channel where only the communication station 01 exists, as shown in the uppermost row in FIG. At this time, the communication station 02 receives the beacon from the communication station 01 and recognizes its existence and beacon position, and as shown in the second stage of FIG. 3, is approximately in the middle of the beacon interval of the communication station 01. Set own beacon transmission timing and start beacon transmission.

  Furthermore, it is assumed that a new communication station 03 appears. At this time, the communication station 03 receives at least one of the beacons transmitted from each of the communication station 01 and the communication station 02 and recognizes the existence of these existing communication stations. Then, as shown in the third stage of FIG. 3, transmission is started at a timing almost in the middle of the beacon interval transmitted from the communication station 01 and the communication station 02.

  Thereafter, the beacon interval is narrowed every time a communication station newly enters the neighborhood according to the same algorithm. For example, as shown at the bottom of FIG. 3, the communication station 04 that appears next sets the beacon transmission timing at a timing almost in the middle of the beacon interval set by each of the communication station 02 and the communication station 01, and then The appearing communication station 05 sets the beacon transmission timing at substantially the middle of the beacon interval set by the communication station 02 and the communication station 04.

  However, the minimum beacon interval Bmin is defined so that the band (transmission frame period) does not overflow with beacons, and two or more beacon transmission timings are not allowed to be placed in Bmin. For example, if the minimum beacon interval Bmin is defined as 2.5 milliseconds with a transmission frame period of 40 milliseconds, only a maximum of 16 communication stations can be accommodated within the reach of radio waves.

  FIG. 4 shows an example of beacon transmission timing on one channel. However, in the example shown in the figure, the passage of time in a transmission frame period of 40 milliseconds is represented as a clock in which the hour hand moves clockwise on the ring.

  In the example shown in FIG. 4, a total of 16 communication stations from the communication station 0 to the communication station F are configured as nodes of the network. As described with reference to FIG. 3, beacon placement is performed according to an algorithm in which beacon transmission timings of new entrant stations are sequentially set at almost the middle of the beacon interval set by an existing communication station. And When Bmin is defined as 2.5 milliseconds, no more communication stations can enter the network.

  Similar to the case of the IEEE 802.11 system and the like, a plurality of packet intervals are also defined in this embodiment. The definition of the packet interval here will be described with reference to FIG. The packet interval here defines a short inter frame space (SIFS) and a long inter frame space (LIFS). Only packets with high priority are allowed to be transmitted at SIFS packet intervals, and other packets are confirmed to be clear by the packet interval of (LIFS + random backoff to obtain a value at random). Allow transmission. As a method for calculating the random back-off value, a method known in the existing technology is applied.

  Further, in the present embodiment, “LIFS” and “FIFS + backoff” (FIFS: Far Inter Frame Space) are defined in addition to the above-described packet intervals “SIFS” and “LIFS + backoff”. Normally, the “SIFS” and “LIFS + backoff” packet intervals are applied, but in the time zone in which a certain communication station is given priority for transmission, other stations use the “FIFS + backoff” packet interval. The station to which priority is given uses the packet interval in SIFS or LIFS.

  Each communication station transmits a beacon at regular intervals, but for a while after transmitting the beacon, the station that transmitted the beacon is given transmission priority. FIG. 6 shows a state in which priority is given to the beacon transmitting station. This priority section is defined as Transmission Guaranteed Period (TGP). Further, a section other than TGP is defined as “Fairly Access Period (FAP)”, and communication is performed between communication stations by the CSMA / CA method. FIG. 7 shows the configuration of the transmission frame period (T_SF). As shown in the figure, following the transmission of the beacon from each communication station, the TGP of the communication station that transmitted the beacon is allocated, and when the time has elapsed by the length of the TGP, it becomes FAP, and the next communication station FAP ends with the transmission of the beacon from. In addition, although the example where TGP starts immediately after the transmission of the beacon is shown here, the present invention is not limited to this. For example, the start time of the TGP is set by the relative position (time) from the transmission time of the beacon. Also good.

  Here, the packet interval on one channel is considered again as follows. Each communication station performs transmission at an interval of LIFS + backoff in FAP. In addition, regarding the transmission of packets within the TGP of the local station of beacons, transmission at SIFS intervals is permitted. In addition, regarding the transmission of the packet within the TGP of the own station, the transmission at the LIFS interval is allowed. Further, regarding transmission of packets within the TGP of another station, transmission is performed at an interval of FIFS + backoff. In the IEEE802.11 scheme, FIFS + backoff is always taken as a packet interval. However, according to the configuration of the present embodiment, this interval can be reduced, and more effective packet transmission is possible.

  In the above description, the priority transmission right is given only to the communication station in the TGP. However, the priority transmission right is also given to the communication station called by the communication station in the TGP. Basically, in TGP, priority is given to transmission, but there is nothing to be transmitted within the local communication station, but when it is known that other stations hold information to be transmitted to the local station, A paging message or a polling message may be sent to “other station”.

  Conversely, if you have sent a beacon, but your station has nothing to send and you do not know that the other station has the information you want to send to your station, Do nothing, abandon the transmission priority given by TGP, and do nothing. Then, after the LIFS + back-off or FIFS + back-off has elapsed, another station starts transmission even in this time zone.

  Considering the configuration in which TGP continues immediately after beacon transmission as shown in FIG. 7, the transmission efficiency is better when the beacon transmission timing of each communication station is evenly distributed within the transmission frame period than when it is dense. More preferred. Therefore, in this embodiment, beacon transmission is started in the middle of the time zone in which the beacon interval is the longest in the range where the user can hear it. Of course, there is also a utilization method in which the beacon transmission timing of each communication station is concentrated and the reception operation is stopped in the remaining transmission frame period to reduce the power consumption of the apparatus.

  FIG. 8 shows a configuration example of the beacon signal format. As shown in the figure, the beacon signal has a preamble for notifying the presence of the signal followed by a heading and a payload part PSDU. In the heading area, information indicating that the packet is a beacon is posted. Further, the following information that is desired to be notified by a beacon is described in PSDU.

TX. ADDR: MAC address of transmitting station (TX) TOI: TBTT offset indicator (TBTT Offset Indicator)
NBOI: Neighbor Beacon Offset Information
TIM: Traffic Indication Map (Traffic Indication Map)
PAGE: Paging

  The TIM is broadcast information indicating to which communication station this communication station currently has information, and by referring to the TIM, the receiving station can recognize that it must receive it. it can. Further, Paging is a field indicating that transmission is scheduled in the immediately following TGP among the receiving stations listed in the TIM, and the station specified in this field must be prepared for reception by TGP. . Other fields (ETC fields) are also prepared. The ETC field may include, for example, a field describing a degree of interference, that is, an interference level (IntLCH) as channel quality information in each prepared frequency channel.

  The NBOI is information describing the beacon arrangement of neighboring communication stations in a transmission frame on a channel. In the present embodiment, since a maximum of 16 beacons can be arranged in the transmission frame period in each channel, the NBOI is configured as a 16-bit length field corresponding to each beacon position, and the arrangement of received beacons is related. Describe information in bitmap format. Then, with reference to the beacon transmission timing of the local station, 1 is written in the bit corresponding to the relative position (offset) of the beacon reception timing from each communication station, and the bit position corresponding to the relative position of the timing not receiving the beacon is 0. Leave as it is.

  FIG. 9 shows a description example of the NBOI when the number of used channels is one. In the example shown in the figure, an NBOI field for indicating that the communication station 0 shown in FIG. 3 “can receive beacons from the communication stations 1 and 9” is shown. The most significant bit of the NBOI field is assigned to the beacon transmission position of the local station, and the mark corresponding to the relative position of the beacon of the adjacent station that can be received with reference to this position is marked and received when the beacon is received. If not, allocate space. For other purposes, marking may be performed on a bit corresponding to a timing when a beacon is not received. In this embodiment, NBOI information that describes the beacon arrangement for each frequency channel that can be used is necessary. This point will be described later.

  When each communication station receives each other's beacon signal on a channel, it determines its beacon transmission timing while avoiding beacon collision on each available frequency channel based on the description of the NBOI included in the communication station. The beacon reception timing from other stations can be detected.

  FIG. 10 shows how a new entrant station arranges its own beacon transmission timing on a certain frequency channel while avoiding a collision with an existing beacon based on the description of NBOI. In each stage of the figure, the entry states of the communication stations STA0 to STA2 are shown. The left side of each stage shows the arrangement state of each communication station, and the right side shows the arrangement of beacons transmitted from each station.

  The upper part of FIG. 10 shows a case where only the communication station STA0 exists. At this time, since STA0 tries to receive a beacon but is not received, STA0 can set an appropriate beacon transmission timing and can start beacon transmission in response to the arrival of this timing. The beacon is transmitted every 40 milliseconds (transmission frame). At this time, all bits in the NBOI field described in the beacon transmitted from STA0 are 0.

  The middle part of FIG. 10 shows a state where STA1 has entered within the communication range of the communication station STA0. When STA1 attempts to receive a beacon, the beacon of STA0 is received. Further, since all the bits other than the bit indicating the transmission timing of the local station are 0 in the NBOI field of the beacon of STA0, the own beacon transmission timing is set approximately in the middle of the beacon interval of STA0 according to the above-described processing procedure.

  In the NBOI field of the beacon transmitted by STA1, 1 is set in the bit indicating the transmission timing of the local station and the bit indicating the beacon reception timing from STA0, and all other bits are 0. Also, when STA0 recognizes the beacon from STA1, it sets 1 to the corresponding bit position in the NBOI field.

  The lowermost part of FIG. 10 shows a state in which STA2 has entered the communication range of communication station STA1 after that. In the illustrated example, STA0 is a hidden terminal for STA2. For this reason, STA2 cannot recognize that STA1 has received a beacon from STA0, and as shown on the right side, there is a possibility that a beacon is transmitted at the same timing as STA0 and a collision occurs.

  The NBOI field is used to avoid this phenomenon. First, the NBOI field of the beacon of STA1 is set to 1 in the bit indicating the timing at which STA0 is transmitting a beacon in addition to the bit indicating the transmission timing of the local station. Therefore, STA2 cannot directly receive the beacon transmitted by STA0, which is a hidden terminal, but recognizes the beacon transmission timing of STA0 based on the beacon received from STA1, and avoids beacon transmission at this timing.

  Then, as shown in FIG. 11, at this time, the STA2 determines the beacon transmission timing substantially in the middle of the beacon interval between the STA0 and the STA1. Of course, in the NBOI in the transmission beacon of STA2, the bit indicating the beacon transmission timing of STA2 and STA1 is set to 1. With such a beacon collision avoidance function based on the description of the NBOI field, a beacon collision can be avoided by grasping the beacon position of a hidden terminal, that is, two adjacent stations.

B. Avoiding interference and deadlock in a multi-channel environment As described above, in an autonomous distributed wireless communication system, each communication station broadcasts beacon information within a transmission frame period and scans beacon signals from other stations. By performing the operation, the network configuration on one channel can be recognized. However, in the case of the multi-channel autonomous distributed network according to the present embodiment, the transmission frames as shown in FIG. 4 are arranged on the frequency axis by the number of used channels (see FIG. 12). ). For this reason, a communication station cannot receive a beacon unless it has shifted to the same channel at the beacon transmission timing of another communication, and it is difficult to grasp the network configuration on all channels.

  Further, even if the communication station is the optimum channel for the own station, there is a possibility that the other station which is the communication partner is a channel receiving interference. For example, if the beacon transmission channel of one station is an interference channel or an unusable channel because the communication quality deteriorates in the other station, these communication stations may communicate with each other on the other channel. Even if they can, they will fall into a deadlock state where they cannot recognize each other's existence forever.

  As already mentioned, each communication station is equipped with a single antenna, it is assumed that transmission and reception cannot be performed in parallel, and that it is not possible to handle multiple frequency channels at the same time. . Here, consider a state in which two communication stations are arranged in an interference environment as shown in FIG.

  The communication station # 1 is arranged in a communication environment with a left slanted line indicating that it is receiving interference on the channel CH1 but not receiving interference on the channel CH2 (clear). It is set as a transmission channel. Further, the communication station # 2 is arranged in a communication environment with a right oblique line indicating that the channel CH2 receives interference but the channel CH1 does not receive interference (clear). Is set as the beacon transmission channel. In this situation, since the beacons are transmitted through the mutual interference channels, the existence of both parties cannot be noticed forever.

  Therefore, in this embodiment, each communication station changes the beacon transmission channel according to a predetermined selection rule with reference to the initial channel. Here, by making the channel selection rule for changing the beacon transmission channel the same in all communication stations, each communication station grasps the beacon transmission time and beacon transmission channel of the adjacent station by autonomous distributed control, and Can be received.

  In an autonomous distributed multi-channel wireless communication environment, a wireless communication device operating as a communication station obtains the next beacon transmission channel based on the beacon reception timing from the adjacent station and the initial channel information, and is adjacent on the channel. Wait for reception according to the beacon transmission timing of the station.

  Therefore, even when communication on a certain channel is difficult due to interference or the like, communication is possible by periodically changing the channel. In addition, since a procedure for deciding a communication channel between communication stations is unnecessary, a simple operation can be realized, and unnecessary communication is reduced, so that the throughput of the entire system is improved.

  Below, the operation example which changes a use channel in a radio | wireless communication apparatus is demonstrated.

B-1. Channel change method 1
FIG. 13 shows a state in which communication stations A to D arrange beacon transmission timing on each channel in a multi-channel communication system including four channels 1 to 4. As shown in the figure, the communication stations A to D are shifted from each other so that the beacon transmission timing does not collide with the beacons of other stations. In addition, channels for transmitting and receiving beacons are also set for each communication station.

  Assuming that the minimum step of the beacon interval of each terminal is T_SF / 8, in the case of the beacon transmission time and relative channel arrangement as shown in FIG. 13, as the beacon position information described as shown in FIG. I can grasp it.

  In the example illustrated in FIG. 14, columns of beacon position information are prepared for the number of beacons that can be arranged in the transmission frame period T_SF. The first column is assigned to the beacon transmission position of the own station, and the beacon transmission channel (initial channel) is written. The subsequent columns are assigned to transmission times for each T_SF / 8 based on the beacon transmission position of the local station, and can be received at the corresponding relative position (offset) from the beacon transmission position of the local station. The channel information of the completed beacon is written.

  The beacon position information as shown in FIG. 14 includes the presence / absence of a beacon at the transmission time corresponding to each column, and the channel if there is a beacon, and is recorded in the neighboring communication device information NBOI in a multi-channel communication environment. Equivalent to. Each communication station creates beacon position information based on a beacon that the local station has received on each channel, and writes the information in the beacon so as to notify the neighboring stations. Also, beacon position information is extracted from the received beacon and the contents of the beacon position information of the own station are updated.

  The communication station obtains a beacon transmission channel in each transmission frame period based on the description content of such beacon position information, and switches to the corresponding channel when the beacon transmission / reception time comes, and tries transmission / reception.

  The relative channel arrangement of the beacons is preferably arranged such that the transmission times of the beacons are as far as possible from each other. This is because data communication in the priority transmission period TGP acquired after beacon transmission / reception is performed on the channel of the beacon, and therefore, when the beacon is separated as much as possible, each communicable time can be increased (same as above). FIG. 15 shows a beacon arrangement example of each communication station on the multi-channel.

  In this embodiment, each communication station changes the beacon transmission channel according to a predetermined selection rule with reference to the initial channel. Here, the beacon transmission channel is changed every transmission frame period, that is, every beacon transmission. Further, as selection criteria for the beacon transmission channel, it is assumed that selection rules of the round robin method are common to all communication stations in the order of channel 1 → channel 2 → channel 3 → channel 4 → channel 1 →.

  In such a case, the channel arrangement of the beacon of each communication station in the next transmission frame period after the transmission frame period T_SF as shown in FIG. 13 is as shown in FIG.

  As shown in FIG. 14, the communication station can grasp the beacon time of the adjacent station and the beacon channel (initial channel) by referring to the beacon position information, that is, the NBOI in the multi-channel communication environment. It is known in advance that the channel selection order is in the order of channel 1 → channel 2 → channel 3 → channel 4 → channel 1 →... Therefore, even if the adjacent station changes the beacon transmission channel every T_SF, the channel at the next beacon reception timing can be predicted. That is, the communication station waits for reception of a beacon on the predicted channel in accordance with the arrival of the beacon time of the adjacent station.

  In the present embodiment, it is assumed that communication is performed between communication stations by the CSMA / CA method. Each communication station predicts the beacon transmission timing of the adjacent station and its transmission channel based on the initial channel of beacon transmission and the channel selection rule. And if it is waiting on the channel predicted at the beacon time, it is possible to receive a beacon packet. By analyzing the received beacon, the presence of the beacon transmission terminal is grasped, and information such as the interference state (channel quality information) where the beacon transmission station is located and the peripheral station (hidden terminal) is grasped. Thereafter, following the beacon, data communication is performed between the transmitting terminal and other terminals. The communication section with the adjacent station on the beacon transmission side continues until the next beacon reception time.

  In this way, in the autonomous distributed control wireless communication system in which each communication station transmits a beacon, packet communication based on the CSMA / CA method is possible while periodically changing the channel. That is, by periodically changing the channel, even if the communication status of a specific channel is bad, it is possible to communicate on another communication channel. As a result, the average communication situation is better than when staying on a specific channel. In addition, the method of regularly changing channels in this way eliminates the need for a mechanism for determining and notifying the communication channel between communication stations, thus realizing a multi-channel communication system with simple operation without the intervention of a control station. can do.

B-2. Channel change method 2
Here, as described above, a multi-channel communication system is assumed in which a plurality of channels 1 to 4 are prepared, and each communication station arranges beacon transmission timing on each channel. In the beacon from each communication station, channel quality information describing the interference level received on each channel is described (described above).

  Here, when the communication station determines that the communication quality is poor and transmission is difficult on a specific channel, the communication station avoids the change to the channel with the poor communication quality on the channel selection rule. Select the previous channel continuously. Such an operation is referred to as “skip channel change” in this specification. And the adjacent station side can recognize the skip of channel change in the communication station on the beacon transmission side based on the channel quality information described in the beacon of the communication station on the beacon transmission side. Wait for beacon reception on the next or previous channel.

  For example, if a communication station that has received a beacon detects that communication on channel 3 is poor and communication is not possible at the communication station on the beacon transmission side, it avoids waiting for reception on channel 3 and the channel selection rule It waits on channel 2 (or channel 4), which is the previous channel. Similarly, the transmission side avoids transmission on channel 3 with poor communication quality, and transmits a beacon on channel 2 (or channel 4) by channel change skip.

  In this way, by communicating the channel quality to each other by notifying the beacon information, it is possible to avoid communication on that channel and to use the channel immediately before (or one ahead) in the channel selection order. Continue communication.

  FIG. 17 shows an operation example in which channel change skipping is performed in accordance with the communication quality in the communication channel, that is, the interference situation. Here, it is assumed that a channel selection rule of changing beacon transmission channels in the order of channel 1 → channel 2 → channel 3 → channel 4 → channel 1 →.

  The leftmost side of the figure shows the actual channel changing operation when the communication station has no interference in all the used channels and the communication quality is good. In this case, the beacon transmission channel is changed in the order of channel 1 → channel 2 → channel 3 → channel 4 → channel 1 →... According to a predetermined channel selection rule.

  Also, in the second from the left in the figure, since the communication quality of channel 3 is poor and communication cannot be performed, communication on channel 3 is avoided, and channel change skip is used to indicate the previous channel in the channel selection rule. Communication is performed on channel 2.

  Similarly, even when there are a plurality of channels with poor communication conditions, channel change skip is performed in the communication stations on both the beacon transmission side and the reception side in the same manner, and the channel selection order is one previous (or one ahead). On the other channel.

  In the third from the left in FIG. 17, when channel 3 and channel 4 receiving interference are avoided, communication on channel 2 is continued three times following channel 1. Further, on the rightmost side of the figure, since interference is received in channels 2 to 4, only communication on channel 1 is continuously performed.

  In the above description, the case where the quality of the communication channel is bad on the transmitting station side has been described. Similarly, the operation when the quality of the communication channel is bad on the receiving station side is also conceivable.

  The interference information of each communication channel on the receiving station side is described in the beacon transmitted so far by this communication station. Since the transmitting station has already received this beacon, the quality information of the communication channel on the receiving station side can be grasped.

  Therefore, when there is a channel that is determined to be difficult to receive at the receiving station, the transmitting communication station continuously selects the next or previous channel by channel change skip. In addition, the receiving station also recognizes the skip of channel change in the transmitting station based on the channel quality information of its own station, and receives the beacon on the next or previous channel on the selection rule. stand by. As a result, the transmitting and receiving stations perform communication while avoiding communication on inconvenient channels.

B-3. Channel change method 3
Here, as described above, a multi-channel communication system is assumed in which a plurality of channels 1 to 4 are prepared, and each communication station arranges beacon transmission timing on each channel. In the beacon from each communication station, channel quality information describing the interference level received on each channel is described (described above).

  The beacon transmission times of the communication stations are shifted from each other as shown in FIG. 13 so as to avoid collision with other beacons. Also, a channel (initial channel) through which a beacon is transmitted is set for each communication station.

  Here, if the minimum beacon interval Bmin in the transmission frame T_SF is T_SF / 8, the beacon transmission time and the relative channel arrangement as shown in FIG. 13 are the beacon position information (multi-channel) as shown in FIG. It can be grasped as neighboring beacon arrangement information). In the example shown in the figure, as many beacons as the number of beacons that can be arranged in the transmission frame period T_SF are prepared for the beacon position information. The first column is assigned to the beacon transmission position of the own station, and the beacon transmission channel (initial channel) is written. Each subsequent column is assigned to a transmission time for each T_SF / 8 based on the beacon transmission position of the own station, and the beacon that can be received at the corresponding relative position from the beacon transmission position of the own station. Channel information is written.

  Each communication station obtains the current beacon transmission channel based on the beacon position information as shown in FIG. 14, and switches to the corresponding channel when the beacon transmission / reception time comes, and attempts transmission / reception.

  The beacon transmission channel selection rule is the same for all communication stations in the same network. In order to realize this, a limited number of transmission channel selection patterns are determined in advance in the entire communication system, and the number of the selection pattern is described in a beacon, for example. A new entrant station determines its own beacon transmission position and channel by receiving a beacon from a peripheral station and acquiring its initial channel and beacon transmission timing. Furthermore, by analyzing the received beacon and obtaining the channel selection pattern number, the channel selection rule in the network can be known. Thereafter, in accordance with the channel selection rule, the beacon reception standby operation can be performed by obtaining the next transmission channel of the beacon of the peripheral station. Also, the new entry station changes the channel of its own beacon transmission channel according to this channel selection rule.

  In this way, by making the beacon channel selection rule the same for all communication stations in the network, the network operation can be suitably realized. As a result, if there is information on the initial beacon position and its channel, the current transmission / reception channel can be obtained from each other, and the beacon by autonomous distributed control can be obtained without any special mechanism for notifying the intervention of the control station or channel change. A transmission channel moving operation, that is, a multi-channel communication operation can be realized.

  FIG. 18 shows a processing procedure for a communication station to transmit a beacon in the form of a flowchart in the autonomous distributed multi-channel wireless communication network according to the present embodiment. This operation is actually realized in a form in which the central control unit 103 executes an execution command program stored in the information storage unit 113 in the wireless communication apparatus 100 operating as a communication station.

  When the beacon transmission preparation time of the local station comes (step S1), the communication station first moves the use channel RotateCH to the next channel based on a prescribed channel selection rule (step S2).

  Next, it is determined based on the channel quality information described in the beacon of the transmission destination that has already been received whether the current channel RotateCH is not significantly interfered with in the transmission destination station (step S3).

  Here, if the channel RotateCH does not have much interference at the transmission destination, the RotateCH is set to the beacon transmission channel BcnCH (step S4), and the beacon is transmitted.

  On the other hand, if the channel RotateCH has a large interference at the transmission destination, the previous channel indicated by BcnCH is set as the beacon transmission channel (step S5), and the beacon is transmitted.

[Supplement]
The present invention has been described in detail above with reference to specific embodiments. However, it is obvious that those skilled in the art can make modifications and substitutions of the embodiment without departing from the gist of the present invention. That is, the present invention has been disclosed in the form of exemplification, and the contents described in the present specification should not be interpreted in a limited manner. In order to determine the gist of the present invention, the claims section described at the beginning should be considered.

FIG. 1 is a diagram illustrating an arrangement example of communication apparatuses constituting a wireless communication system according to an embodiment of the present invention. FIG. 2 is a diagram schematically illustrating a functional configuration of a wireless communication apparatus that operates as a communication station in the wireless network according to the embodiment of the present invention. FIG. 3 is a diagram showing a beacon transmission procedure of each communication station according to an embodiment of the present invention. FIG. 4 is a diagram showing an example of beacon transmission timing on one channel. FIG. 5 is a diagram showing the definition of the packet interval. FIG. 6 is a diagram showing a state in which priority is given to the beacon transmitting station. FIG. 7 is a diagram illustrating a configuration of a transmission frame period (T_SF). FIG. 8 is a diagram illustrating a configuration example of a beacon signal format. FIG. 9 is a diagram illustrating a description example of the NBOI when the number of used channels is one. FIG. 10 is a diagram showing a state in which a new entrant station arranges its own beacon transmission timing on a certain frequency channel while avoiding a collision with an existing beacon based on the description of the NBOI. FIG. 11 is a diagram showing a state in which a new entrant station determines the beacon transmission timing almost in the middle of the beacon interval. FIG. 12 is a diagram schematically illustrating a configuration of a wireless communication system having a multi-channel configuration. FIG. 13 is a diagram illustrating a state in which communication stations A to D arrange beacon transmission timing on each channel in a multi-channel communication system including four channels 1 to 4. FIG. 14 is a diagram schematically showing the configuration of the beacon position information. FIG. 15 is a diagram illustrating a state in which transmission time channels are arranged so that beacon intervals of communication stations are separated. FIG. 16 is a diagram showing the beacon channel arrangement of each communication station in the next transmission frame period after the transmission frame period T_SF shown in FIG. FIG. 17 is a diagram illustrating an operation example in which channel change skip is performed according to communication quality in a communication channel, that is, an interference state. FIG. 18 is a flowchart showing a processing procedure for a communication station to transmit a beacon in the autonomous distributed multi-channel wireless communication network according to the present invention. FIG. 19 is a diagram showing a deadlock state when the beacon transmission channel of one station is an interference channel or a channel that cannot be used because the communication quality deteriorates in the other station.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 ... Wireless communication apparatus 101 ... Interface 102 ... Data buffer 103 ... Central control part 104 ... Beacon generation part 106 ... Wireless transmission part 107 ... Timing control part 108 ... Channel setting part 109 ... Antenna 110 ... Wireless reception part 111 ... Channel quality Measurement unit 112 ... Beacon analysis unit 113 ... Information storage unit

Claims (28)

In a communication environment in which a plurality of channels are prepared, a wireless communication system that forms a network based on ad hoc communication with a plurality of wireless communication devices without arranging a control station,
Each communication station transmits a beacon at a predetermined beacon period while sequentially switching its own beacon transmission channel from the plurality of channels at a predetermined time interval.
A wireless communication system. Each communication station sequentially changes the beacon transmission channel according to a predetermined channel selection rule based on a predetermined initial channel.
The wireless communication system according to claim 1. The same channel selection rule for changing the beacon transmission channel in all communication stations,
The wireless communication system according to claim 2. Each communication station obtains the next beacon transmission channel based on the reception timing of the beacon from the adjacent station and the initial channel information, and waits for reception according to the beacon transmission timing of the adjacent station on the channel.
The wireless communication system according to claim 1. Each communication station transmits a beacon including channel quality information describing the communication quality of each channel for the local station.
The wireless communication system according to claim 1. When the communication station determines that transmission on a certain channel is difficult, it skips the next channel change on the selection rule and continuously selects the next or previous channel.
The wireless communication system according to claim 5. The adjacent station recognizes the skip of channel change in the beacon transmission side communication station based on the channel quality information described in the beacon of the beacon transmission side communication station, and on the next or previous channel on the selection rule. Wait for beacon reception,
The wireless communication system according to claim 6. When there is a channel that is determined to be difficult to receive in the adjacent station based on the channel quality information described in the beacon from the adjacent station, the communication station skips the change to the channel according to the selection rule. Select next or previous channel continuously,
The wireless communication system according to claim 5. The adjacent station on the beacon receiving side recognizes the skip of channel change in the communication station on the beacon transmitting side based on the channel quality information of its own station, and waits for beacon reception on the next or previous channel on the selection rule. To
The wireless communication system according to claim 8. A wireless communication device that operates autonomously and distributedly in a wireless communication environment in which a plurality of channels are prepared,
Communication means for transmitting and receiving wireless data in each channel;
Beacon signal generating means for generating a beacon signal describing information about the own station;
A transmission channel for the beacon signal of the local station in the communication means, a communication channel setting means for setting a reception channel for the beacon signal from the peripheral station, and
Control means for controlling a communication operation by the communication means on the channel set by the communication channel setting means;
Beacon signal analyzing means for analyzing a beacon signal received from an adjacent station by the communication means;
With
The communication channel setting means sequentially switches its own beacon transmission channel from the plurality of channels at a predetermined time interval.
A wireless communication apparatus. The communication channel setting means sequentially changes the beacon transmission channel according to a predetermined channel selection rule based on a predetermined initial channel.
The wireless communication apparatus according to claim 10. The communication channel setting means uses the same channel selection rule as the adjacent station.
The wireless communication apparatus according to claim 11. The communication channel setting means obtains the next beacon transmission channel based on the reception timing of the beacon from the adjacent station and the initial channel information,
The control means waits for reception in accordance with the beacon transmission timing of the adjacent station on the beacon transmission channel.
The wireless communication apparatus according to claim 10. Further comprising channel quality acquisition means for acquiring channel quality for each of the plurality of channels based on a received signal or other information by the communication means;
The beacon signal generating means generates a beacon including channel quality information describing communication quality of each channel;
The wireless communication apparatus according to claim 10. The communication channel setting means, when it is determined that transmission on a certain channel is difficult, skips the next channel change on the selection rule and continuously selects the next or previous channel,
The wireless communication apparatus according to claim 14. The communication channel setting means recognizes the skip of channel change in the adjacent station based on the channel quality information described in the beacon received from the adjacent station, and receives the next or previous channel on the selection rule as a beacon. Set the channel for
The control means waits for reception of a beacon on the channel;
The wireless communication apparatus according to claim 15. The communication channel setting means, when there is a channel that is determined to be difficult to receive in the adjacent station based on the channel quality information described in the beacon received from the adjacent station, to the channel according to the selection rule To skip next change and select next or previous channel continuously,
The wireless communication apparatus according to claim 14. The communication channel setting means recognizes the skip of channel change when a neighboring station transmits a beacon based on the channel quality information of the local station, and sets the next or previous channel on the selection rule as a channel for beacon reception. Set,
The control means waits for reception of a beacon on the channel;
The wireless communication apparatus according to claim 17. A wireless communication method for performing autonomous distributed communication operations in a wireless communication environment in which a plurality of channels are prepared,
A beacon signal generating step for generating a beacon signal describing information about the own station;
A communication channel setting step for setting a beacon signal transmission channel of the own station and a beacon signal reception channel from a peripheral station,
A control step for controlling a communication operation on the channel set by the communication channel setting step;
A beacon signal analyzing step for analyzing a beacon signal received from an adjacent station;
With
In the communication channel setting step, the own beacon transmission channel is sequentially switched at a predetermined time interval from the plurality of channels.
A wireless communication method. In the communication channel setting step, the beacon transmission channel is sequentially changed according to a predetermined channel selection rule based on a predetermined initial channel.
The wireless communication method according to claim 19. In the communication channel setting step, the same channel selection rule as that of the adjacent station is used.
21. The wireless communication method according to claim 20, wherein: In the communication channel setting step, the next beacon transmission channel is obtained based on the reception timing of the beacon from the adjacent station and the initial channel information,
In the control step, reception is waited according to the beacon transmission timing of the adjacent station on the beacon transmission channel.
The wireless communication method according to claim 19. A channel quality acquisition step of acquiring channel quality for the local station for each of the plurality of channels based on a received signal or other information;
In the beacon signal generation step, a beacon including channel quality information describing the communication quality of each channel is generated.
The wireless communication method according to claim 19. In the communication channel setting step, when it is determined that transmission on a certain channel is difficult, the next channel change is skipped on the selection rule and the next or previous channel is continuously selected.
24. The wireless communication method according to claim 23. Recognizing channel change skip in the adjacent station based on channel quality information described in the beacon received from the adjacent station in the communication channel setting step, beacon reception of the next or previous channel on the selection rule Set the channel for
The control step makes a beacon reception standby on the channel,
25. The wireless communication method according to claim 24. In the communication channel setting step, when there is a channel that is determined to be difficult to receive in the adjacent station based on the channel quality information described in the beacon received from the adjacent station, To skip next change and select next or previous channel continuously,
24. The wireless communication method according to claim 23. In the communication channel setting step, based on the channel quality information of the own station, the adjacent station recognizes the skip of channel change when beacon is transmitted, and the next or previous channel on the selection rule is set as a channel for beacon reception. Set,
The control step waits for reception of a beacon on the channel,
27. The wireless communication method according to claim 26. A computer program written in a computer-readable format so as to execute a process for performing autonomous distributed communication operation in a wireless communication environment in which a plurality of channels are prepared on a computer system,
A beacon signal generating step for generating a beacon signal describing information about the own station;
A communication channel setting step for setting a beacon signal transmission channel of the own station and a beacon signal reception channel from a peripheral station,
A control step for controlling a communication operation on the channel set by the communication channel setting step;
A beacon signal analyzing step for analyzing a beacon signal received from an adjacent station;
With
In the communication channel setting step, the own beacon transmission channel is sequentially switched at a predetermined time interval from the plurality of channels.
A computer program characterized by the above.

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