JP4222143B2 - Wireless communication system, wireless communication apparatus, wireless communication method, and computer program - Google Patents

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, and in particular, each communication station appropriately determines its own beacon transmission channel and data transmission channel to form a multi-channel autonomous distributed wireless network. The present invention relates to a wireless communication system, a wireless communication apparatus, a wireless communication method, and a computer program.

  By connecting multiple computers and configuring a LAN, you can share information such as files and data, share peripheral devices such as printers, and exchange information such as e-mail and data / content transfer Can be done.

  Conventionally, it has been common to use an optical fiber, a coaxial cable, or a twisted pair cable to connect to a wired LAN. In this case, however, a line laying work is required, and it is difficult to construct a network easily. The cable routing becomes complicated. In addition, even after LAN construction, the movement range of the device is limited by the cable length, which is inconvenient.

  Therefore, a wireless LAN has attracted attention as a system that releases users from wired LAN connection. 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. In particular, recently, in order to establish a small-scale wireless network between a plurality of electronic devices existing around a person and perform information communication, introduction of a personal area network (PAN) has been studied. For example, different wireless communication systems are defined using frequency bands that do not require a license from a supervisory authority, 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 for configuring a wireless network, “Ad-hoc communication” in which terminals perform wireless communication autonomously 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.

  Therefore, in the conventional wireless network system, a plurality of frequency channels are prepared in advance for coexistence with other networks, and one frequency channel to be used in the wireless communication device serving as an access point is selected and operated. The method of starting is generally adopted.

  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.

  In order to use a plurality of frequency channels properly, taking HiperLAN / 2 as an example, 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 initiative. Specifically, the information used for the determination is as follows: (1) In response to an instruction from the AP, the currently connected MT temporarily stops communication, scans another frequency channel, and evaluates the channel quality. (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 being used, and evaluates the channel quality. It is accumulated by following the processing procedure such as reporting to 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 wireless communication system, the timing of frequency channel switching, the setup process realized by exchanging messages and the frequency channel switching to start the frequency channel switching operation in synchronization with each other are determined. A complicated mechanism such as an arbitration process 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 to the measurement of the interference of the own channel, a radio communication system that determines the frequency channel by measuring the interference when an adjacent channel is used has been proposed (for example, see Patent Document 1). This is a system in which multi-channel is realized by intervening base stations.

  For example, 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; Part 1: Basic Trunk Data Control 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)

  A further object of the present invention is to provide an excellent radio communication system, radio, which can suitably form an appropriate ad hoc network without interfering with each other in a communication environment in which a plurality of channels are prepared. 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 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.

The present invention has been made in consideration of the above-mentioned problems, and a first aspect of the present invention is that an ad hoc communication is performed by a plurality of communication stations without arranging a control station in a communication environment in which a plurality of channels are prepared. A wireless communication system forming a network based on
Each communication station transmits a beacon on a beacon transmission channel that is optimal for its own reception, and performs data transmission using the beacon transmission channel of the data transmission destination communication station.
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.

  In an autonomous decentralized wireless communication system, each communication station broadcasts beacon information within a transmission frame period, and can recognize a network configuration by performing a scanning operation of beacon signals from other stations. However, in the case of an autonomous decentralized network that uses multi-channels, since the transmission frame is multiplexed on the frequency axis by the number of channels used, the communication station uses the same channel at the beacon transmission timing of other communications. If it is not shifted upward, it is impossible to receive a beacon, and it is difficult for a new entry station to determine its own beacon transmission timing and transmission channel.

  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.

  In the present invention, each communication station selects a channel with the best communication quality for its own station as a beacon transmission channel, and arranges the beacon transmission timing of its own station on this channel to perform beacon transmission. When the beacon transmission timing of an existing station is already set on the own beacon transmission channel, the own beacon transmission timing is determined so as not to overlap in time. In the beacon information, for example, interference information in each channel is described. Further, the communication station shifts to the beacon transmission channel of the other station and receives the beacon according to the beacon transmission timing of the other station.

  On the other hand, when data is transmitted from a communication station, data is transmitted using a channel suitable for reception at the communication station serving as a data transmission destination, regardless of the beacon transmission channel of the local station. Which channel has good communication quality in each communication station can be easily determined depending on which channel the station is using for beacon transmission.

  In this way, each communication station determines a beacon transmission channel depending only on its own interference situation, and this is known as a channel for receiving its own traffic. Control at each communication station below becomes easy.

  Here, each communication station may acquire a priority transmission period in accordance with its own beacon transmission timing.

  In addition, each communication station shifts to the beacon transmission channel of the other station according to the beacon transmission timing of the other station and receives the beacon, and then gives priority transmission given to the other station on the beacon transmission channel. Even during the period, data transmission operations on other channels are allowed.

  For example, data transmission is performed using a beacon transmission channel of a destination communication station using a priority transmission period acquired after a beacon transmission by a certain communication station. Then, when the beacon reception timing of the other station approaches during the priority period, the transmission is temporarily stopped and the transmission proceeds to the beacon transmission scheduled channel. In the destination channel, the other station uses the priority transmission period, but if it is different from the channel used by the own station, it can return to the original channel and continue the data transmission operation.

  Therefore, according to the present invention, each communication station can autonomously determine a communication channel and efficiently avoid interference, and can effectively improve communication capacity by effectively using multiple channels. it can.

  Also, in the autonomous distributed wireless communication system according to the present invention, random access based on CSMA / CA can be performed in a period other than the priority transmission period arranged immediately after the beacon transmission timing on each channel. At this time, the RTS / CTS method can be adopted as means for avoiding collision and improving communication quality.

  In such a case, the data transmission source communication station transmits a transmission request packet RTS on the beacon transmission channel of the data transmission destination communication station, and responds to reception of the confirmation notification packet CTS from the data transmission destination communication station. Then, data transmission may be started.

  In addition, assuming that there is a communication station that is a hidden terminal from the data transmission destination communication station, the data transmission source communication station precedes the transmission of the RTS signal, on its own beacon transmission channel, You may make it transmit the beacon which specified the communication station of a data transmission destination, and its beacon transmission channel. A peripheral station that has received such a beacon refrains from interfering with data transmission for a predetermined time on a beacon transmission channel of a data transmission destination communication station, that is, a channel on which data transmission based on the RTS / CTS procedure is performed. Try to avoid it.

  At this time, if the beacon transmission channel of the data transmission source and the beacon transmission channel of the data transmission destination communication station match, a beacon specifying the data transmission destination communication station and the beacon transmission channel is represented by a pseudo RTS signal. Consider it. Further, the data transmission destination communication station can start data transmission by returning a CTS signal in response to receiving a beacon specifying the data transmission destination communication station and its beacon transmission channel. Thus, by omitting the RTS signal transmission procedure (RTS signal retransmission), the overhead of the RTS / CTS procedure in multi-channel can be reduced.

A second aspect of the present invention is a computer in which a plurality of channels are prepared, and a process for operating in an autonomous and distributed manner in a wireless communication environment in which a specific control station is not arranged is executed on a computer system. A computer program written in a readable format,
A channel setting step for setting a channel for data transmission and reception;
A communication control step for controlling the timing of data transmission and reception;
A beacon generating step for generating a beacon signal of the own station;
A beacon analyzing step for analyzing a received beacon signal from a peripheral station,
In the channel setting step, the self-beacon transmission channel is determined from the plurality of channels, and at the time of data transmission, the beacon transmission channel of the data transmission destination communication station is determined as the data transmission channel.
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.

  In addition, 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 is achieved 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.

  In addition, according to the present invention, in an autonomous distributed multi-channel wireless network, each communication station performs frequency allocation efficiently and performs flexible interference avoidance, thereby improving the overall system throughput and other neighboring wireless networks. The impact on the system can be reduced. Further, since a plurality of channels can be used simultaneously, the throughput of the entire system can be improved also in this respect.

  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.

  The propagation path of communication assumed in the present invention is wireless, and a network is constructed between 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 a wireless communication system in which no control station is particularly arranged in this way, each communication station notifies beacon information so that other communication stations in the vicinity (that is, within the communication range) can know the existence of itself, and the network configuration can be changed. Notice. 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.

  Each wireless communication apparatus arbitrarily determines one of the available channels as a reference channel to be used for transmitting its own beacon signal, and defines a predetermined transmission frame period on the reference channel. This reference channel is selected from among the multi-channels based on the own station such that the communication quality is good for the own station. In such a case, there is a possibility that the channel that is optimal for the local station is a channel that is receiving interference for the communication station that receives the beacon. In this embodiment, since the beacon transmission channel of each communication station is most suitable for reception, data transmission is performed using the beacon transmission channel of the communication station of the data transmission destination, and interference is avoided. I try to get communication quality. 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. The figure shows a state where communication devices # 0 to # 6 are distributed in the same space.

  In addition, in the same figure, the communication range of each communication device is indicated by a broken line, and it is defined not only as being able to communicate with other communication devices within the range, but also as a range in which a signal transmitted by itself interferes. . 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 apparatus 100 includes an interface 101, a data buffer 102, a central control unit 103, a beacon generation unit 104, a control signal generation unit 105, a wireless transmission unit 106, a timing control unit 107, and a channel setting unit. 108, an antenna 109, a wireless reception unit 110, a control signal analysis unit 111, a beacon analysis unit 112, and an information storage unit 113.

  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 the wireless communication apparatus 100 to operate a wireless network, the communication quality in each channel is confirmed, and the best channel for the own station is set as a reference channel for beacon transmission. Then, on the beacon transmission channel of the own station, the position of the own beacon transmission slot is determined at an arbitrary timing when there is no existing station so that the existing stations do not overlap in time. Information relating to the communication quality of each channel, the beacon transmission channel of the own station, and other beacon transmissions are stored in the information storage unit 113. The configuration of the beacon signal will be described later.

  Prior to data transmission, the control signal generation unit 105 generates control information (described later) such as a transmission request (RTS: Request to Send) signal and a confirmation notification (CTS: Clear to Send) signal as necessary. The RTS / CTS communication method in the multi-channel communication environment will be described in detail later.

  The wireless transmission unit 106 performs predetermined modulation processing to wirelessly transmit data and beacons 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 long-distance communication applicable to a wireless LAN, for example, can be applied. Specifically, a UWB system, an OFDM system, a CDMA system, or the like can be employed.

  The timing control unit 107 controls timing for transmitting and receiving radio signals. For example, the control unit controls the beacon transmission timing of the local station at the beginning of the transmission frame cycle defined on the beacon transmission channel of the local station, the scan operation cycle of each channel, the beacon reception timing from the peripheral station in each channel, and the like.

  The channel setting unit 108 selects a channel for actually transmitting and receiving a multi-channel radio signal. Specifically, among the plurality of prepared frequency channels, the best channel interference is set as the beacon transmission channel of the own station, and the communication station that is the transmission destination at the time of data transmission is a channel suitable for reception ( That is, the beacon transmission channel of the receiving station is sequentially set as a data transmission channel.

  Which channel is optimal for receiving traffic in the local station can be determined, for example, by measuring communication quality when scanning each channel. In addition, since the state of each channel changes from moment to moment, the channel setting unit 108 resets the beacon transmission channel of the own station when the channel state changes by a predetermined value or more or every predetermined period. May be. Note that the channel quality measurement method and beacon transmission channel resetting are not directly related to the gist of the present invention and will not be described further in this specification.

  The control signal analysis unit 111 analyzes control information such as an RTS signal and a CTS signal transmitted from a peripheral wireless communication device.

  The beacon analysis unit 112 analyzes a beacon signal received from a peripheral station, and analyzes the presence of a nearby wireless communication device. For example, information such as the beacon transmission channel of the peripheral station, its reception timing, and the channel interference information described in the reception beacon are stored in the information storage unit 113 as neighboring device information.

  The information storage unit 113 executes a sequence of access control operations executed by the central control unit 103 (program for performing scan setting, channel setting, etc.), own beacon transmission timing, beacon transmission channel, and other communication Multi-channel information such as the beacon transmission timing of the station and the beacon transmission channel, neighboring device information, interference information in each channel of the own station and peripheral stations, etc. are stored.

  In the present embodiment, the wireless communication apparatus 100 operating as a communication station performs a gradual time division multiplexing in an ad hoc network environment without a specific control station in a communication environment in which a plurality of channels are prepared. Communication operation such as transmission control using a plurality of channels effectively or random access based on CSMA / CA is performed by a transmission (MAC) frame having an access structure.

  Each communication station determines the channel for beacon transmission based on its own communication quality and informs other communication stations in the neighborhood (that is, within the communication range) of its own presence by notifying the beacon information. Notify the 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, only the operation on a specific channel will be mentioned.

  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 transmitted 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. However, 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.

  For example, it is assumed that a new communication station 02 appears in a network state where only the communication station 01 exists, as shown in the uppermost stage 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, a minimum beacon interval Bmin is specified so that the band (transmission frame period) does not overflow with beacons, and it is not allowed to place two or more beacon transmission timings within 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 priorities are allowed to be transmitted at SIFS packet intervals, and other packets are allowed to be transmitted after LIFS + random backoff packet interval to obtain a value after confirming that the media is clear . As a method for calculating the random back-off value, a method known in 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)”. FIG. 7 shows the configuration of the transmission frame period. 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 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 this example, this interval can be reduced, and more effective packet transmission can be performed.

  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. However, 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 (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. In addition, 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. .

  A field (ETC field) other than the above is also prepared in the beacon. The ETC field may include a field describing a degree of interference in each prepared frequency channel, that is, an interference level (IntLCH).

  In addition, when the communication station intends to perform data transmission based on the RTS / CTS procedure, the communication station may specify the data transmission destination communication station and its beacon transmission channel using the ETC field. When performing random access based on CSMA / CA, the communication quality can be maintained by the RTS / CTS procedure, which will be described later.

  The NBOI is information describing the beacon arrangement of neighboring communication stations. 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, based on the beacon transmission timing of the local station, 1 is written in the bit corresponding to the relative position 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 remains 0. To do. In this embodiment, NBOI information is prepared for each available frequency channel.

  FIG. 9 shows a description example of the NBOI. 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. Regarding the bit corresponding to the relative position of the beacon that can be received, a mark is assigned if a beacon is received, and a space is assigned if it is not received. For other purposes, marking may be performed on a bit corresponding to a timing when a beacon is not received.

  Each communication station receives each other's beacon signal and arranges its own beacon transmission timing while avoiding beacon collisions on each available frequency channel based on the description of the NBOI included in the communication station. Beacon reception timing 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.

  As described above, in an autonomous distributed wireless communication system, each communication station broadcasts beacon information within a transmission frame period, and performs a scanning operation of a beacon signal from another station, thereby configuring a 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). ). In the present embodiment, it is assumed that each communication station has a single antenna, cannot perform transmission and reception in parallel, and cannot handle multiple frequency channels at the same time. (Mentioned above). 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.

  Therefore, in this embodiment, each communication station selects the channel with the best communication quality for its own station as the beacon transmission channel, while when transmitting data, the data transmission destination is independent of its own beacon transmission channel. The communication station to be used performs data transmission using a channel having good communication quality and suitable for reception.

  Which channel has good communication quality in each communication station can be easily determined depending on which channel the station is using for beacon transmission. Each communication station determines a beacon transmission channel depending only on its own interference situation, and this is known as a channel for receiving its own traffic, so each communication station in a multi-channel autonomous distributed communication environment Control in the communication station becomes easy.

  Here, consider a state in which two or more communication stations are arranged in an interference environment as shown in FIG.

  Each communication station sets the channel with the best communication quality as the beacon transmission channel of the local station in consideration of only the interference situation in the local station. In the example shown in the figure, communication station # 2 receives interference on channel # 4 and communication station # 3 receives interference on channel # 1. Therefore, in order to avoid interference at the time of data reception, communication station # 2 transmits a beacon on channel # 3 and communication station # 3 transmits a beacon on channel # 2, respectively. The peripheral station can be instructed to send on the other channel.

  Further, since the communication station # 1 has not received any interference on the channel # 1, the local station beacon is transmitted using the channel # 1 to efficiently reuse the frequency. Similarly, since the communication station # 4 has not received interference on the channel # 4, the local station beacon is transmitted using the channel # 4 to efficiently reuse the frequency. By transmitting a beacon on a channel that receives traffic, it is possible to declare that the band will be used and to reduce interference from other systems.

  FIG. 14 shows how each communication station performs beacon transmission and data transmission on each channel. However, in the illustrated example, each communication station acquires the priority transmission period TGP immediately after its own beacon transmission timing.

  Each communication station sets the channel with the best communication quality in its own station as its own beacon transmission channel. In the illustrated example, communication station # 1 is channel # 1, communication station # 2 is channel # 3, communication station # 3 is channel # 2, communication station # 4 is channel # 4, and the beacon of the time station. It is set as a transmission channel.

  Since each communication station transmits a beacon at the beginning of its own frame period on its own beacon transmission channel, the transmission frame period is defined by the beacon interval. The transmission frame period is composed of a plurality of slots (five in the example shown in the figure), and the first beacon transmission slot is arranged on the beacon transmission channel of the own station, and the own reception slot and the surroundings are provided on other channels. A beacon receiving slot from the station is arranged.

  Each communication station transmits a beacon to a beacon slot determined on the beacon transmission channel of the time station at a timing that does not overlap with other beacons in time. Each communication station shifts to the beacon transmission channel of the other station and receives a beacon with the arrival of the beacon transmission timing of the other station.

  The communication station can receive the beacon signal of the other station on each channel, for example, by a scanning operation at the time of activation, and acquire these beacon transmission channels and beacon transmission timing. In addition, the communication station performs a scanning operation at a predetermined interval on the beacon transmission channel of the local station or other channels that can communicate (not receiving interference), and the beacon transmission channel of other stations, the beacon transmission timing, etc. The neighborhood information may be constantly updated. Note that the procedure of the scanning operation itself is not directly related to the gist of the present invention and will not be described further in this specification.

  Each communication station can acquire the priority transmission period TGP following the beacon transmission (see FIG. 7). The communication station that has obtained the priority transmission right moves to the optimum channel on the receiving side (that is, the beacon transmission channel on the receiving side) and starts transmitting traffic.

  When the beacon transmission timing of another station approaches during the priority transmission period, the communication station that is transmitting data temporarily stops the data transmission operation and shifts to a beacon transmission scheduled channel for reception of the beacon. Then, the other station that transmitted the beacon continues to acquire the priority transmission period TGP.

  In this embodiment, even during a priority transmission period of a certain communication station, other data transmission operations are allowed on channels other than those used for this priority transmission. That is, if the channel used by the communication station that transmitted the beacon as TGP is different from the channel currently used by the local communication station, the channel can be used continuously after receiving the beacon.

  In the example shown in FIG. 14, the communication station # 1 transmits data using channel # 3, which is the beacon transmission channel of the data transmission destination communication station # 2, in its own priority transmission period acquired with beacon transmission. Perform the action.

  After that, before sending the transmission data, the beacon transmission timing of the other communication station # 3 is approaching. Therefore, the data transmission operation is temporarily stopped, and the communication is shifted to the channel # 2 which is a beacon transmission scheduled channel. The beacon of station # 3 is received. The communication station # 3 performs a data transmission operation using the channel # 4, which is the beacon transmission channel of the data transmission destination communication station # 4, in the priority transmission period acquired along with the beacon transmission.

  At this time, the communication station # 1 continues to use the channel after receiving the beacon because the channel # 4 used as the priority transmission period by the communication station # 3 is different from the channel # 3 currently used by the local station. can do. That is, after receiving the beacon of the communication station # 3, the communication station # 1 continuously obtains a priority transmission period on the channel # 3 and resumes the data transmission operation to the communication station # 2.

  After shifting to the beacon transmission channel of the other station and receiving the beacon, the data transmission operation is continued regardless of the channel other than the channel on which the other station transmits data. In the present embodiment, as shown in FIG. 14, when the channel used before receiving the beacon of the other station is used as it is, data transmission can be performed without performing a new negotiation particularly between the communication stations. . However, when using channels other than those used before receiving beacons by other stations, if there are multiple channels that can be communicated, the receiving side must use the same channel in advance. It is necessary to negotiate the usage channel.

  Therefore, according to the present invention, each communication station can autonomously determine a communication channel and efficiently avoid interference, and can effectively improve communication capacity by effectively using multiple channels. it can.

  Also, in the autonomous distributed wireless communication system according to the present invention, random access based on CSMA / CA can be performed in a period other than the priority transmission period arranged immediately after the beacon transmission timing on each channel. At this time, the RTS / CTS method can be adopted as means for avoiding collision and improving communication quality.

  In this case, prior to transmission of the net information, the transmission source communication station transmits RTS (Request to Send), and if the reception destination communication station can receive the RTS and receive data, the response As CTS (Clear to Send). Then, data transmission is executed after a connection is established between the transmitting and receiving stations by exchanging RTS / CTS information.

  Here, a general data transmission / reception sequence using RTS / CTS information exchange will be described with reference to FIG. However, the example shown in the figure is a sequence when data transmission is performed from the transmission source communication station # 1 to the reception destination communication station # 2 on a specific channel. Further, the communication station # 0 is a hidden terminal for the communication station # 2, and the communication station # 3 is a hidden terminal for the communication station # 1.

  First, prior to transmitting data from the communication station # 1 to the communication station # 2, after detecting that the channel is empty in the communication station # 1, a predetermined preamble signal P (131) and an RTS signal (132) ).

  Here, the RTS signal describes time information until the CTS is received, and the peripheral station that has received the RTS signal performs a collision avoidance operation by stopping signal transmission during that period. In the illustrated example, when the communication station # 0 receives the RTS signal of the communication station # 1, the communication station # 0 performs an operation of setting a time (transmission standby period) during which transmission from the communication station # 0 is refrained from the reception time information. On the other hand, since the communication station # 3 is a hidden terminal, it cannot receive the RTS signal.

  Further, if the communication station # 2 can receive the RTS signal and can receive data thereafter, it returns a predetermined preamble signal P (133) and a CTS signal (134).

  The CTS signal describes time information until data reception is completed, and the peripheral station that has received this CTS signal performs a collision avoidance operation by stopping signal transmission during that period. In the illustrated example, when the communication station # 3 receives the CTS signal of the communication station # 2, the communication station # 3 performs an operation of setting a time (transmission standby period) to refrain from transmission from the reception time information.

  In this way, even a communication station that is a hidden terminal for one of the transmitting and receiving stations does not perform a transmission operation for a predetermined time by receiving either the RTS or CTS signal, thereby avoiding interference and improving communication quality. Is maintained.

  Then, the communication station # 1 that has received this CTS signal performs a transmission process of a predetermined preamble signal P (135) and data Data (136) over the time described in the CTS signal, and the communication station # 2 At the same time, the data Data (136) is received.

  At this time, in the communication station # 0, it is grasped from the header information Head (not shown) of the data Data (136) that the data communication from the communication station # 1 is performed, and over this data communication duration, the communication station # You may make it perform the control which does not perform transmission addressed to 1.

  In addition, if necessary, whether or not the data has been correctly received may be returned from the wireless communication device # 2 to the wireless communication device # 1 as ACK information (not shown).

  Next, an application example of the RTS / CTS scheme to the multi-channel autonomous distributed wireless network according to the present embodiment will be described with reference to FIG.

  As already described, in the present embodiment, the data transmission source communication station shifts to the beacon transmission channel of the data transmission destination communication station and performs the data transmission operation. For this reason, if a peripheral station that is a hidden terminal for a data transmission destination communication station has an interfering channel as a transition destination channel, an RTS signal transmitted on the transition destination channel cannot be heard. The hidden terminal problem occurs.

  Therefore, assuming that there is a communication station that is a hidden terminal from the data transmission destination communication station, the data transmission source communication station precedes the RTS signal transmission on its own beacon transmission channel, A beacon specifying the data transmission destination communication station and its beacon transmission channel is transmitted.

  This beacon signal functions as an RTS signal in a pseudo manner. The hidden terminal can avoid interference by withholding the data transmission operation for a predetermined time in response to receiving the pseudo RTS signal on the original channel.

  Thereafter, the data transmission source communication station shifts to the beacon transmission channel of the data transmission destination communication station, transmits a transmission request packet RTS, and responds to reception of the confirmation notification packet CTS from the data transmission destination communication station. Start data transmission.

  FIG. 17 shows another example in which the RTS / CTS scheme is applied to the multi-channel autonomous distributed wireless network according to the present embodiment.

  In this embodiment, the data transmission source communication station precedes the transmission of the RTS signal in order to avoid the hidden terminal problem associated with the data transmission operation by shifting to the beacon transmission channel of the data transmission destination communication station. Then, on the beacon transmission channel of the local station, the data is transmitted together with the beacon specifying the data transmission destination communication station and the beacon transmission channel.

  At this time, if the beacon transmission channel of the data transmission source and the beacon transmission channel of the data transmission destination communication station match, a beacon specifying the data transmission destination communication station and the beacon transmission channel is represented by a pseudo RTS signal. Consider it.

  In addition, the data transmission destination communication station returns a CTS signal without waiting for the arrival of a regular RTS signal in response to receiving a beacon specifying the data transmission destination communication station and its beacon transmission channel. Thus, data transmission can be started.

  Thus, by omitting the RTS signal transmission procedure (RTS signal retransmission), the overhead of the RTS / CTS procedure in multi-channel can be reduced.

  18 to 20 show, in the form of flowcharts, processing procedures for the wireless communication apparatus 100 to operate autonomously as a communication station in the multipath autonomous distributed wireless network according to the present embodiment. However, it is assumed that the wireless communication station 100 has already acquired neighboring station information such as beacon transmission channels and beacon transmission timings of peripheral stations by a scanning operation (not shown). As illustrated, the communication station has a steady operation mode that does not depend on a transmission request, a transmission start mode triggered by beacon transmission, and a transmission continuation mode. Such a processing procedure is actually realized in a form in which the central control unit 103 executes an execution instruction program stored in the information storage unit 113.

  Under the steady operation mode, when the beacon transmission timing of the peripheral station arrives until the beacon transmission timing arrives (step S16), the mobile station shifts to the beacon transmission channel of the peripheral station and receives the beacon (step S17). ).

  When the beacon transmission timing of the local station arrives (step S1), it is checked whether or not there is a transmission request from an upper layer of the communication protocol (for example, an external device connected via the interface 101) (step S2). If there is no transmission request, a beacon is transmitted on the beacon transmission channel that is optimum for itself (step S13).

  On the other hand, when there is a transmission request from an upper layer, for the RTS / CTS procedure, on the beacon transmission channel of the local station, a beacon specifying the communication station as the data transmission destination and the beacon transmission channel is specified. Transmission is performed at the beacon transmission timing (step S3).

  Next, transition is made to the transmission start mode, and it is checked whether the beacon transmission channel of the local station and the beacon transmission channel of the data transmission destination communication station (that is, the channel used for data transmission) match (step S4).

  If the beacon transmission channels do not match each other, the RTS signal is transmitted (step S15) after shifting to the beacon transmission channel of the data transmission destination communication station (step S14). On the other hand, if the beacon transmission channels match each other, the beacon specifying the data transmission destination communication station and the beacon transmission channel is regarded as a pseudo RTS signal, and transmission of a regular RTS signal and channel transition operation are performed. Is omitted. Then, it waits for a CTS signal from the data transmission destination communication station (step S5).

  Here, when the CTS signal cannot be received within the predetermined time (step S6), the process proceeds to step S15 to retransmit the RTS signal.

  On the other hand, if the CTS signal is successfully received within the predetermined time, the data transmission requested from the upper layer is executed (step S7). Then, it is checked whether or not there is a further transmission request from the upper layer (step S8). When the transmission request is completed, the process returns to step S1 to perform a beacon transmission / reception operation under the steady operation mode.

  When the transmission request continues, the mode transits to the transmission continuation mode. Then, it is checked whether there is still room until the beacon transmission timing of the own station (step S9). If there is no room, the process returns to step S1 to perform a beacon transmission operation under the steady operation mode.

  If there is still room until the beacon transmission timing of the local station, it is further checked whether there is still room until the beacon transmission timing of the peripheral station (step S10). If there is no room, the mobile station shifts to the beacon transmission channel of the peripheral station and receives a beacon (step S16).

  Then, it is checked whether the beacon transmission channel of the local station and the beacon transmission channel of the data transmission destination communication station match (step S17). If the beacon transmission channels do not match, the process proceeds to step S15 to retransmit the RTS signal. If the beacon transmission channels match each other, the process returns to step S1 to perform a beacon transmission operation under the steady operation mode.

  If there is a margin until the beacon transmission timings of the own station and the peripheral stations (step S10), the process proceeds to step S15 to retransmit the RTS signal.

  If there is no allowance for the beacon transmission timing of the peripheral station (step S9), the process returns to step S1 to perform the beacon transmission operation under the steady operation mode.

[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 according to an embodiment of the present invention. FIG. 3 is a diagram for explaining a beacon transmission procedure of each communication station according to the present embodiment. FIG. 4 is a diagram showing an example of beacon transmission timing on one channel. FIG. 5 is a diagram for explaining 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 showing the configuration of the transmission frame period. 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. 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 the own beacon transmission timing is arranged while avoiding the beacon transmission timing of the hidden terminal based on the beacon information received by the new entry station. FIG. 12 is a diagram schematically showing a transmission frame configuration of an autonomous distributed multi-channel wireless communication system. FIG. 13 is a diagram illustrating a state in which each communication station transmits its own beacon using a channel that receives traffic. FIG. 14 is a diagram illustrating a state in which each communication station performs beacon transmission and data transmission using the priority transmission period TGP on each channel. FIG. 15 is a diagram showing an operation sequence of the RTS / CTS method. FIG. 16 is a diagram illustrating an example in which the RTS / CTS scheme is applied to a multi-channel autonomous distributed wireless network according to the present invention. FIG. 17 is a diagram illustrating another example in which the RTS / CTS scheme is applied to the multi-channel autonomous distributed wireless network according to the present invention. FIG. 18 is a flowchart showing a processing procedure for the wireless communication apparatus 100 to operate autonomously as a communication station in the multipath autonomous distributed wireless network according to the present invention. FIG. 19 is a flowchart showing a processing procedure for the wireless communication apparatus 100 to autonomously operate as a communication station in the multipath autonomous distributed wireless network according to the present invention. FIG. 20 is a flowchart showing a processing procedure for the wireless communication apparatus 100 to autonomously operate as a communication station in the multipath autonomous distributed wireless network according to the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 ... Wireless communication apparatus 101 ... Interface 102 ... Data buffer 103 ... Central control part 104 ... Beacon generation part 105 ... Control signal generation part 106 ... Wireless transmission part 107 ... Timing control part 108 ... Channel setting part 109 ... Antenna 110 ... Wireless Reception unit 111 ... Control signal analysis unit 112 ... Beacon analysis unit 113 ... Information storage unit

Claims (21)

A wireless communication system that forms a network with a plurality of communication stations in a communication environment in which a plurality of channels are prepared,
Each communication station transmits a beacon on a beacon transmission channel that is optimal for its own reception, and performs data transmission using the beacon transmission channel of the data transmission destination communication station.
A wireless communication system. Each communication station determines its own beacon transmission timing so that it does not overlap in time when the beacon transmission timing of the existing station is already set on the beacon transmission channel determined to be optimal for its own reception. ,
The wireless communication system according to claim 1. Each communication station shifts to the beacon transmission channel of the other station as the beacon transmission timing of the other station arrives, and receives a beacon.
The wireless communication system according to claim 1. Each communication station acquires a priority transmission period with its own beacon transmission.
The wireless communication system according to claim 1. Each communication station moves to the beacon transmission channel of the other station according to the beacon transmission timing of the other station, receives the beacon, and even during the priority transmission period given to the other station, Data transmission operation is allowed on a channel other than the channel on which the other station transmits data.
The wireless communication system according to claim 4. The data transmission source communication station transmits a transmission request packet RTS on the beacon transmission channel of the data transmission destination communication station, and starts data transmission in response to receiving the confirmation notification packet CTS from the data transmission destination communication station. To
The wireless communication system according to claim 1. The data transmission source communication station transmits a beacon specifying the data transmission destination communication station and its beacon transmission channel on its own beacon transmission channel,
The peripheral station that has received the beacon refrains from transmitting data on the beacon transmission channel for a predetermined period.
The wireless communication system according to claim 1. The communication station of the data transmission source omits transmission of the transmission request packet RTS when the beacon transmission channel of its own station matches the beacon transmission channel of the communication station of the data transmission destination,
The data transmission destination communication station transmits a confirmation notification packet CTS in response to receiving a beacon specifying the data transmission destination communication station and its beacon transmission channel.
The wireless communication system according to claim 1. A wireless communication device that operates in a wireless communication environment in which a plurality of channels are prepared,
Communication means for transmitting and receiving wireless data in each channel;
Channel setting means for setting a channel for data transmission and reception in the communication means;
Communication control means for controlling the timing of data transmission and reception in the communication means;
Beacon generating means for generating a beacon signal of the own station to be transmitted through the communication means;
A beacon analyzing means for analyzing a beacon signal of a peripheral station received by the communication means,
The channel setting means determines its own beacon transmission channel from the plurality of channels, and sets a beacon transmission channel of a data transmission destination communication station as a data transmission channel at the time of data transmission.
A wireless communication apparatus. The channel setting means determines the channel having the best communication quality or reception suitable for the local station among the plurality of channels as the beacon transmission channel of the local station.
The wireless communication apparatus according to claim 9. The communication control means, when the beacon transmission timing of an existing station is already set on the beacon transmission channel of the own station, determines its own beacon transmission timing so as not to overlap in time.
The wireless communication apparatus according to claim 9. The channel setting means sets the beacon transmission channel of the local station as a transmission channel in response to the beacon transmission timing of the local station approaching,
The communication control means controls the beacon transmission operation in response to the arrival of the beacon transmission timing of the local station.
The wireless communication apparatus according to claim 9. The channel setting means sets the beacon transmission channel of the peripheral station as a reception channel in response to the beacon transmission timing of the peripheral station approaching,
The communication control means controls the reception operation in response to the arrival of the beacon transmission timing of the peripheral station.
The wireless communication apparatus according to claim 9. The communication control means acquires a priority transmission period along with the beacon transmission of the own station.
The wireless communication apparatus according to claim 9. After the communication control means shifts to the beacon transmission channel of the other station according to the beacon transmission timing of the other station and receives the beacon, even during the priority transmission period given to the other station, The data transmission operation is performed on a channel other than the channel on which the other station performs data transmission.
The wireless communication apparatus according to claim 14. The communication control means transmits a transmission request packet RTS on the beacon transmission channel of the data transmission destination communication station, and starts data transmission in response to receiving the confirmation notification packet CTS from the data transmission destination communication station. ,
The wireless communication apparatus according to claim 9. The beacon generating means generates a beacon specifying a data transmission destination communication station and its beacon transmission channel,
The communication control means transmits the beacon on its own beacon transmission channel.
The wireless communication apparatus according to claim 9. The communication control means returns a confirmation notification packet in response to receiving a transmission request packet RTS addressed to the own station or a beacon specifying the own station as a transmission destination on the beacon transmission channel of the own station.
The wireless communication apparatus according to claim 17. The communication control means refrains from transmitting data for a predetermined time on the reception channel in response to receiving a transmission request packet RTS addressed to another station or a beacon specifying the other station as a transmission destination.
The wireless communication apparatus according to claim 17. A wireless communication method that operates in a line communication environment in which a plurality of channels are prepared,
A channel setting step for setting a channel for data transmission and reception;
A communication control step for controlling the timing of data transmission and reception;
A beacon generating step for generating a beacon signal of the own station;
A beacon analyzing step for analyzing a received beacon signal from a peripheral station,
In the channel setting step, the beacon transmission channel is determined from the plurality of channels, and at the time of data transmission, the beacon transmission channel of the data transmission destination communication station is determined as the data transmission channel.
A wireless communication method. A computer program written in a computer-readable format to execute processing on a computer system for operating in a wireless communication environment in which a plurality of channels are prepared,
A channel setting procedure for setting a channel for data transmission and reception;
A communication control procedure for controlling the timing of data transmission and reception;
A beacon generation procedure for generating a beacon signal of the own station;
Run the beacon analysis procedure to analyze the received beacon signal from the peripheral station,
In the channel setting procedure, the self-beacon transmission channel is determined from the plurality of channels, and at the time of data transmission, the beacon transmission channel of the data transmission destination communication station is determined as the data transmission channel.
A computer program characterized by the above.

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