JP4748217B2 - 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 autonomously distributed operation of each communication station without particularly disposing the apparatus.

  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 general, in order to configure a local area network using wireless technology, a device serving as a control station called an “access point” or “coordinator” is provided in the area. A method of forming a network under comprehensive control is 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.

  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. Information for determination can be acquired through, for example, the following processing procedure.

(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 currently used frequency channel, evaluates the channel quality, and reports the result to the AP. Accumulated by following the processing procedure.

  Also, 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. Existence is essential to construct a network, which is a reference for frequency channel hopping patterns and synchronization in the time axis direction. When the master disappears, the network formed up to that point 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 that performs control mainly is essential. If the central control station such as AP or master disappears, some protocol processing or artificial setting change work to select the central control station to replace it will be necessary, and communication will be 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 a multi-channel is realized by intervening base stations and cannot be applied to an autonomous distributed system.

  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. Of course, the beacon transmission channel selected by the communication station on the basis of its own station is not necessarily a channel that can be received by all peripheral communication stations.

  If 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, 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 Control Data ETSI TS 101 761-2 V1.3.1 Broadband Radio Access Networks (BRAN); HIPERLAN Type2; Data Link Control (DLC) Layer; Part2: Radio Link Control (LC)

  It is an object of the present invention to provide an excellent wireless network capable of suitably forming a network by operating in a distributed manner without mutual interference between communication stations in a communication environment in which a plurality of channels are prepared. A communication system, a wireless communication 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.

The present invention has been made in consideration of the above-mentioned problems. The first aspect of the present invention is that autonomous distribution 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 of a type,
Each communication station transmits a beacon signal at a predetermined cycle using a channel that can be received by more peripheral stations.
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. Of course, the beacon transmission channel selected by the communication station on the basis of its own station is not necessarily a channel that can be received by all peripheral stations. 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, the level information of the interference received by the local station is transmitted on the beacon signal (or a signal for reporting some interference information) periodically transmitted by each communication station. Therefore, the communication station determines the communication channel after grasping the interference state based on the beacon information received from the peripheral station. Therefore, it is possible to control the communication channel in an autonomous and distributed manner by avoiding the use of a channel in which peripheral communication stations are severely interfered as a communication channel.

  The communication station selects, as a beacon transmission channel, a channel that can be received by as many communication stations as possible based on the interference information of each channel described in the beacon signal when newly entering or refreshing. If there is a peripheral station that cannot receive a beacon, it tries to change the beacon transmission channel.

  Therefore, according to the present invention, in consideration of the interference level of peripheral stations in each channel, a channel that can be received by as many communication stations as possible is selected and operated as a beacon transmission channel. It is possible to avoid falling into a deadlock state where it is impossible to avoid as much as possible. Further, each communication station does not need to switch channels during a period when there is no transmission data and only beacon reception is performed.

  If the interference received by the communication station is an acceptable level, the communication station uses the same communication channel as that of the peripheral communication station as much as possible, thereby reducing the overhead required for RTS / CTS packet exchange and channel transition. can do.

  The communication station may perform data transmission operation using a channel other than the beacon transmission channel. For example, traffic may be transmitted using an optimum channel with a low interference level between communication stations based on interference information obtained from a beacon signal of a communication partner.

  For example, the communication station may determine the beacon transmission channel according to whether or not the local station requires a wide band. For example, when the own station requires a wide band, a channel having a low interference level for itself is selected as much as possible without being used by another communication station, and beacon transmission is started. The same operation is performed on both the transmitting side and the receiving side.

  On the other hand, communication stations that do not need a wide band should transmit beacons on the same channel as possible as peripheral communication stations, considering the overhead at the time of channel change. Focus on (most channels).

  When the peripheral station including itself does not receive a large interference on the most frequent channel, beacon transmission is started on that channel. Also, if there are multiple communication stations that have received a large amount of interference that cannot be received by the beacon transmitted at the lowest rate, select the channel with the lowest average interference level and start transmitting the beacon there. .

  Moreover, according to the radio | wireless communications system which concerns on this invention, traffic transmission can be managed autonomously distributed by giving a preferential communication right with respect to the beacon transmission station after beacon transmission. At this time, after beacon transmission, it is also possible to shift the channel used preferentially to a channel optimum for traffic transmission, which is different from the beacon transmission channel, according to the interference state on the receiving side.

  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 communication system, 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. Start data transmission.

  Here, assuming that there is a communication station that is a hidden terminal from the communication station that is the data transmission destination, the communication station that is the data transmission source is on the beacon transmission channel of its own station prior to the transmission of the RTS signal. A beacon multiplexed with the RTS signal may be transmitted. The peripheral station that has received such a beacon avoids interference by withholding data transmission for a predetermined time on a channel on which data transmission based on the RTS / CTS procedure is performed.

  At this time, if the beacon transmission channel of the data transmission source matches the beacon transmission channel of the communication station of the data transmission destination, the RTS signal and the multiplexed beacon are regarded as the RTS signal itself. The data transmission destination communication station can start data transmission by returning a CTS signal in response to receiving the beacon. In this way, by omitting retransmission of the RTS signal, the overhead of the RTS / CTS procedure in the multi-channel can be reduced.

A second aspect of the present invention is a wireless communication system in which a plurality of communication stations form a network in an autonomous and distributed manner without arranging a control station in a communication environment in which a plurality of channels are prepared. ,
Each communication station transmits a beacon at a predetermined transmission frame period on its own beacon transmission channel, and the beacon transmission channel set by another station that does not need to communicate is currently used by its own station. If it is different from the existing channel, the beacon reception operation from the other station is omitted, and the channel switching for beacon reception is not performed.
This is a wireless communication system.

  As described above, according to the wireless communication system according to the first aspect of the present invention, in a multi-channel autonomous distributed network, a communication station can set a more optimal channel as its own beacon transmission channel. .

  Here, each communication station needs to transmit a beacon at a predetermined transmission frame period to grasp the presence of the peripheral station and notify the network status, and to receive the beacon of the peripheral station. In a multi-channel network, in order to receive a beacon, a communication station must shift to a beacon transmission channel in accordance with the beacon transmission timing of a peripheral station. However, channel switching takes about 300 microseconds in terms of hardware operation. For this reason, a communication station that is performing data communication interrupts data communication in order to receive the beacon of another station, performs channel transition and beacon reception, then transitions to the original channel and resumes data communication. , The overhead gets bigger.

  Therefore, in the second aspect of the present invention, when the communication station grasps that the beacon transmission timing of another station is approaching, after determining whether it is necessary to communicate with the beacon transmission station, When there is no need to receive a beacon and the currently used channel is different from the beacon transmission channel, the beacon receiving operation is omitted.

  In this way, by omitting unnecessary beacon reception operations, the time required for beacon transition and the power consumption of the apparatus can be omitted, and the communication capacity can be increased.

  Here, in the wireless communication system according to the present invention, traffic traffic is managed in an autonomous and distributed manner by giving a priority communication right to the beacon transmission station (described above). You do not always get priority transmission rights on the channel. That is, the beacon transmitting station may shift the channel used preferentially to a channel optimal for traffic transmission different from the beacon transmission channel according to the interference state on the receiving side.

  There is a possibility that the beacon transmission station shifts the channel immediately after the beacon transmission and starts data communication. However, if the communication station omits the beacon reception operation, such a channel shift operation cannot be recognized. Therefore, when the beacon reception operation is omitted, the communication station estimates the RTS and CTS signal transmission timing based on the beacon transmission timing, performs the reception operation on the channel currently used only for these timings, Detects whether the transmitting station has shifted to the channel currently used.

  When the communication station detects that the beacon transmission station has shifted to the channel currently used at the transmission timing of the RTS and CTS signals, the communication station refrains from the data communication operation of the local station, thereby Avoid collisions. On the other hand, if not detected, the beacon transmitting station recognizes that it has acquired the priority transmission right on another channel, and continues its own data communication operation on the currently used channel. Do.

  In this way, when the beacon reception operation of another station is omitted, the beacon transmission station performs the reception operation only for a predetermined period in the priority transmission period acquired by beacon transmission, so that unnecessary channel transition is not performed. In addition, a communication collision can be avoided.

According to a third aspect of the present invention, there is provided a computer in which a plurality of channels are prepared and processing for operating in an autonomous 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 data transmission and reception;
A beacon generating step of generating a beacon signal including level information of interference received by the own station;
A beacon analysis step for analyzing a beacon signal received from a peripheral station is provided.
In the channel setting step, the communication channel is determined after grasping the interference status of each channel in the peripheral station based on the interference level information included in the beacon received from the peripheral station.
This is a computer program characterized by the above.

According to a fourth aspect of the present invention, there is provided a computer in which a plurality of channels are prepared and a process for operating in an autonomous 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 beacon transmission step of setting a beacon transmission channel of the local station and transmitting a beacon;
A beacon reception control step for controlling beacon reception operation from a peripheral station;
A beacon analysis step for analyzing a beacon signal received from a peripheral station;
A communication control step of setting a data communication channel and controlling data communication operation;
The beacon reception control step includes:
A sub-step for grasping that the beacon transmission timing of another station is approaching,
A sub-step for determining whether it is necessary to communicate with the beacon transmitting station;
Including a sub-step in which it is not necessary to receive a beacon and the currently used channel is different from the beacon transmission channel, omitting the beacon receiving operation.
This is a computer program characterized by the above.

  The computer program according to each of the third and fourth aspects of the present invention defines a computer program described in a computer-readable format so as to realize predetermined processing on the computer system. In other words, by installing the computer program according to each of the third and fourth aspects 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, the same operational effects as those of the wireless communication system according to the first and second aspects of the present invention can be obtained.

  Advantageous Effects of Invention According to the present invention, in an autonomous distributed wireless network that does not require a specific control station, an excellent wireless communication system and wireless communication that can perform channel access by effectively using a plurality of frequency channels. An apparatus, a wireless communication method, and a 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 multi-channel autonomous decentralized wireless communication system according to the present invention, it is possible to suitably avoid a deadlock state between communication stations and to improve the throughput of the entire system by an efficient frequency arrangement. Furthermore, the influence on other systems can be reduced.

  In addition, according to the multi-channel autonomous decentralized wireless communication system according to the present invention, it is necessary to transmit the beacon to grasp the presence of the peripheral station and notify the network state, and to receive the beacon of the peripheral station. By omitting unnecessary beacon reception operations, the time required for beacon transition and the power consumption of the apparatus can be omitted, and the communication capacity can be increased.

  When the beacon reception operation is omitted, the transmission timing of the RTS and CTS signals is estimated based on the beacon transmission timing, and the reception operation is performed on the channel currently used only for these timings. A communication collision can be avoided without performing a transition.

  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 between a plurality of communication stations using a transmission medium composed of a plurality of frequency channels, that is, multichannels. 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 its vicinity (that is, within the communication range) can communicate their Notify existence and notify network configuration. Each communication station detects a peripheral station by scanning on the use channel and receiving a beacon signal, and recognizes a network configuration by decoding information described in the beacon (or in the network). Can enter). 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.

  The processing in each communication station described below is basically processing executed in all communication stations that participate in the autonomous distributed 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 station is not arranged, 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 manages a series of information transmission and reception processing and transmission path access control in the wireless communication apparatus 100 (multi-channel scan setting operation, channel setting operation, beacon receiving operation, data in accordance with the RTS / CTS method) Including communication operations).

  The beacon generation unit 104 generates a beacon signal that is periodically exchanged with a nearby wireless communication device.

  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. In the present embodiment, the RTS signal and the beacon signal may be multiplexed and transmitted. However, the RTS / CTS communication system in a multi-channel autonomous distributed 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. In this embodiment, the beacon signal is transmitted at the lowest settable rate so that as many communication stations as possible can receive it.

  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. In this embodiment, each communication station determines its own beacon transmission channel and data communication channel based on the communication quality of each channel. For this reason, the radio receiving unit 110 estimates the propagation path condition in each channel and notifies the central control unit 103 of the estimated channel condition.

  The timing control unit 107 controls timing for transmitting and receiving radio signals. For example, the local station's beacon transmission timing at the beginning of the transmission frame cycle defined on its own beacon transmission channel, the beacon reception timing from peripheral stations in each channel, the scan operation cycle in each channel, the beacon transmission channel and channel interference It controls the refresh cycle for setting information, the transmission timing (interframe space (IFS)) of each packet (RTS, CTS, data, ACK, etc.) in accordance with the RTS / CTS method.

  The channel setting unit 108 selects a channel for actually transmitting and receiving a multi-channel radio signal. In this embodiment, a channel that can be received by as many communication stations as possible is set as a beacon transmission channel. Further, based on the interference information obtained from the beacon signal of the communication partner, an optimum channel having a low interference level between communication stations can be set as the data transmission channel.

  Which channel is optimal for receiving traffic in the local station can be determined by measuring the communication quality when, for example, each channel is scanned. In addition, since the state of each channel changes from moment to moment, in addition to new entry, a refresh operation is performed at a predetermined period to obtain the latest channel interference information and a channel setting operation is performed. Of course, the beacon transmission channel may be reset when the communication quality in any channel changes by a predetermined value or more. 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 (including an RTS signal multiplexed into a beacon 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 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, and the like are stored.

  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 own beacon transmission timing is determined at an arbitrary timing when there is no existing station so that the existing stations do not overlap in time. Information regarding the communication quality of each channel, the beacon transmission channel of the own station, and other beacon transmission / reception is stored in the information storage unit 113. The configuration of the beacon signal will be described later.

B. In this embodiment, the wireless communication apparatus 100 operating as a communication station has a moderate 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. A communication operation such as transmission control using a plurality of channels effectively by random transmission (MAC) frames or random access based on CSMA / CA is performed.

  Here, CSMA is a connection method for performing multiple access based on carrier detection. In wireless communication, it is difficult to receive a signal transmitted by itself, so it is confirmed that there is no information transmission of other communication devices by CSMA / CA method instead of CSMA / CD, Avoid collisions by initiating transmissions.

  Each communication station selects, as a beacon transmission channel, a channel that can be received by as many communication stations as possible based on the interference information of each channel of the local station and the peripheral stations. Then, by notifying the beacon information on the most frequent channels, other communication stations in the neighborhood (that is, within the communication range) are informed of the existence of itself, and by notifying the network configuration, the neighborhood (ie, within the communication range) Notify other communication stations of their existence and notify the network configuration. The beacon transmission cycle is defined as “transmission frame (T_SF)” and is set to 40 milliseconds, for example. The beacon transmission channel is set by the channel setting unit 108.

  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 be recognized. Then, the beacon transmission timing of the local station is set to a timing at which the beacon is not transmitted from the peripheral station while being gently synchronized with the beacon reception timing.

  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 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. 3, 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.

  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.

  Here, since each communication station acquires a preferential use area (TPP) immediately after the beacon transmission (described later), when placing a new beacon in a transmission frame, each communication station has one channel on each channel. It is more preferable in terms of transmission efficiency that the beacon transmission timings are evenly distributed within the transmission frame period than are dense. Therefore, in this embodiment, as shown in FIG. 3, beacon transmission is basically started in the middle of the time zone in which the beacon interval is the longest within 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. 4 shows an example of beacon transmission timing within a transmission frame 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. The position where the beacon transmission timing can be arranged in the transmission frame is also referred to as “slot”. Each communication station intentionally transmits at a time having a slight time offset (TBTT offset) from TBTT (Target Beacon Transmission Time) which is the beacon transmission timing of the local station.

  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 5 milliseconds, only a maximum of 16 beacons can be arranged per transmission frame. That is, 16 or more communication stations cannot enter the network.

  In the present embodiment, a plurality of inter-frame spaces are defined as in the case of the IEEE 802.11 system or the like. As shown in FIG. 5, Short Inter Frame Space (SIFS) and Long Inter Frame Space (LIFS) are defined as the inter-frame space.

  When a normal packet is transmitted according to the procedure of CSMA, as shown in FIG. 5B, after the transmission of some packet is finished, the media state is first monitored by LIFS, and the medium is cleared or transmitted during this period. If there is no signal, random backoff is performed, and if there is no transmission signal during this period, the transmission right is given. As a method for calculating the random back-off value, a method known in the existing technology such as using a pseudo-random sequence is applied.

  On the other hand, when a packet with high priority or urgency is transmitted, it is allowed to transmit after a SIFS interframe space shorter than LIFS. That is, as shown in FIG. 5A, the media state is monitored only by SIFS, and if the media is cleared during this period, that is, if no transmission signal exists, a transmission right is given. As a result, a packet having a high degree of urgency can be transmitted prior to a packet transmitted according to a normal CSMA procedure (that is, transmitted after waiting for LIFS + random backoff).

  For example, a communication station within a priority transmission period (TPP) starts transmission after an interframe space of SIFS, thereby securing the right to transmit packets preferentially. In addition, according to the RTS / CTS method, CTS, data, and ACK packets transmitted following RTS are also transmitted in the interframe space of SIFS, so that a series of communication procedures are executed without being disturbed by neighboring stations. can do.

  In short, by defining different types of inter-frame spaces, priority is given to packet contention rights according to the length of the inter-frame space.

  Furthermore, in the present embodiment, in addition to “SIFS” and “LIFS + backoff” which are the interframe spaces described above, as shown in FIGS. 5C and 5D, “LIFS” and “FIFS + backoff”. (FIFS: FarInter Frame Space) is defined. Normally, an interframe space of “SIFS” and “LIFS + backoff” is applied. On the other hand, in a time zone in which the priority of transmission is given to a certain communication station, the other station uses the inter-frame space of “FIFS + backoff”, and the station to which priority is given is a frame in SIFS or LIFS. Use a space.

  Each communication station transmits a beacon at regular intervals, but for a while after transmitting the beacon, a preferential transmission period (TPP) in which transmission can be preferentially transmitted to the station that transmitted the beacon is performed. To win. FIG. 6 shows a state in which priority is given to the beacon transmitting station. In this specification, this priority section is defined as Transmission Priority Period (TPP). In the TPP, the communication station secures the right to transmit packets preferentially by starting transmission after the inter-frame space of SIFS.

  In addition, a section other than TPP is defined as “Fairly Access Period (FAP)”, and each communication station performs communication by a normal CSMA / CA system. In other words, all communication stations including beacon transmitting stations that have passed TPP can start transmission after waiting for LIFS + random backoff, in other words, transmission rights are equally given by random backoff. Will be.

  FIG. 7 illustrates an operation for a beacon transmitting station and other stations in the TPP section to obtain a transmission right.

  The beacon transmitting station can start transmission after a shorter bucket interval SIFS after transmitting its own beacon. In the illustrated example, the beacon transmission station transmits an RTS packet after SIFS. After that, the transmitted CTS, data, and ACK packets are similarly transmitted in the interframe space of SIFS, so that a series of communication procedures can be executed without being disturbed by neighboring stations.

  On the other hand, after the beacon is transmitted, the other stations first monitor the media state by LIFS, and during this time, if the media is cleared, that is, if there is no transmission signal, random backoff is performed. If no exists, the right to send is granted. For this reason, if the beacon transmitting station first transmits the RTS signal after the SIFS has elapsed, the media is not clear, and other stations cannot start transmission.

  FIG. 8 illustrates an operation for the communication station to start transmission in each of the TPP section and the FAP section.

  Within the TPP interval, the communication station can start transmission after a shorter bucket interval SIFS after transmitting its own beacon. In the illustrated example, the beacon transmission station transmits an RTS packet after SIFS. After that, the transmitted CTS, data, and ACK packets are similarly transmitted in the interframe space of SIFS, so that a series of communication procedures can be executed without being disturbed by neighboring stations.

  On the other hand, in the FAP section, the communication station waits for LIFS + random backoff and starts transmission similarly to the other peripheral stations. In other words, transmission rights are equally given by random backoff. In the illustrated example, after the beacon of the other station is transmitted, the media state is first monitored by LIFS, and during this time, if the media is cleared, that is, if there is no transmission signal, random backoff is performed, and transmission is also performed during this period. When there is no signal, an RTS packet is transmitted. A series of packets such as CTS, data, and ACK transmitted due to the RTS signal is transmitted in the interframe space of SIFS, so that a series of communication procedures can be executed without being disturbed by neighboring stations. .

  FIG. 9 shows the configuration of the transmission frame period (T_SF). As shown in the figure, following transmission of a beacon from each communication station, a TPP is allocated to the communication station that transmitted the previous beacon, and only the station preferentially transmits in a short interframe space called SIFS. You can get the right.

  When the TPP interval elapses, FAP is entered, and each communication station communicates with the normal CSMA / CA system. That is, all communication stations wait for LIFS + random backoff before starting transmission, so that the transmission right is equally given. Then, the FAP ends when a beacon is transmitted from the next communication station adjacent to the beacon transmission timing. Thereafter, the sequence of the FAP period after the TPP is given to the beacon transmitting station is repeated.

  Although FIG. 9 shows an example in which TPP starts immediately after the transmission of a beacon, the present invention is not limited to this. For example, the start time of TPP is set by the relative position (time) from the transmission time of beacon. May be.

  Here, when summarizing the inter-frame space on one channel, each communication station is given high priority for beacon and packet transmission within its own TPP by allowing transmission at SIFS intervals. . That is, each time a beacon is transmitted, the communication station can start transmission in a short inter-frame space, so that an opportunity to transmit data preferentially is obtained.

  On the other hand, other FAPs are allowed to perform transmission at the interval of LIFS + backoff.

  In addition, the communication station can preferentially obtain the transmission right within the TPP of its own station, but does not occupy the medium in this section. That is, even within the TPP of the local station, other communication stations are allowed to start transmission with an interval of LIFS + backoff. For example, a communication station acquires a TPP by transmitting a beacon, but does not know that there is nothing to transmit to the local station and that the other station holds information that the local station wants to transmit In some cases, the communication operation is not started in the interframe space of SIFS. As a result, the beacon transmitting station has abandoned its own TPP. Then, other communication stations not provided with TPP can start transmission even in this time zone after LIFS + backoff or FIFS + backoff has elapsed.

  FIG. 10 shows an operation when the beacon transmitting station abandons TPP. If the beacon transmitting station does not start transmission at the SIFS interval due to the abandonment of TPP, the other stations can start transmitting packets with LIFS + backoff. In this case, other communication stations not provided with TPP can start transmission even during this time period after LIFS + backoff or FIFS + backoff has elapsed. Even if the TPP is abandoned, if the beacon transmitting station is of course within the TPP section of its own station, the communication station preferentially further at SIFS intervals after the transmission operation of other stations is completed. Transmission can be started.

  Further, regarding the transmission of packets in the TPP of another station, transmission is performed at an interval of FIFS + backoff, and a low priority is given. In the IEEE802.11 scheme, FIFS + backoff is always adopted as an inter-frame space. However, according to the configuration of the present embodiment, 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 TPP. However, the priority transmission right is also given to the communication station called by the communication station in the TPP. Basically, in TPP, transmission is given priority, 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”.

  Considering the configuration in which TPP continues immediately after beacon transmission as shown in FIG. 9, 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.

  In this embodiment, traffic is managed in an autonomous and distributed manner by giving a preferential communication right to the beacon transmitting station (described above). However, in a multi-channel environment, the beacon transmitting station does not always transmit beacons. You don't always get a TPP on the channel. That is, the beacon transmitting station may shift the channel used preferentially to a channel optimal for traffic transmission different from the beacon transmission channel according to the interference state on the receiving side.

  FIG. 11 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) TOIS: TBTT offset indicator (TBTT Offset Indication Sequence)
NBOI: Neighbor Beacon Offset Information
TIM: Traffic Indication Map (Traffic Indication Map)
PAGE: Paging

  In the TOIS field, information for determining the TBTT offset (described above) (for example, a pseudo-random sequence) is stored, and how much the beacon is transmitted with respect to the beacon transmission timing TBTT. Indicates. By providing a TBTT offset, the actual beacon transmission time can be shifted, even when two communication stations have beacon transmission timings arranged in the same slot on the transmission frame, and at a certain transmission frame period. Even if a beacon collides, in another transmission frame period, each communication station hears each other's beacon (or neighboring communication stations hear both beacons), that is, can recognize the collision.

  The TIM is broadcast information indicating to which communication station this communication station currently has information, and by referring to the TIM field, the receiving station recognizes that it must receive it. Can do. Paging is a field indicating that transmission is scheduled in the immediately following TPP among the receiving stations listed in the TIM, and the station specified in this field must be prepared for reception at the TPP. .

  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).

  Further, when the communication station intends to perform data transmission based on the RTS / CTS procedure from now on, it uses the ETC field (or provides a dedicated field for PSDU) and the beacon transmission of the data transmission destination communication station. The channel may be specified. 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 field is information describing the beacon position (reception time) of an adjacent station that can be received by the own station in the transmission frame. In the present embodiment, as shown in FIG. 4, since a slot in which a maximum of 16 beacons are arranged in one transmission frame is prepared, information on the arrangement of received beacons is a 16-bit bitmap format. Describe in. That is, the beacon transmission timing TBTT of the local station is mapped to the first bit (MSB) of the NBOI field, and the other slots are mapped to bit positions corresponding to relative positions (offsets) based on the TBTT of the local station. To do. Then, 1 is written in the bit position assigned to each slot of the transmission beacon of the own station and the receivable beacon, and the other bit positions remain 0.

  FIG. 12 shows a description example of the NBOI when the number of used channels is one. In the example shown in the figure, the communication station 0 creates an NBOI field such as “1100,0000,0100,0000”. As shown in FIG. 4, the communication station 0 shown in FIG. 3 has the communication station 0 shown in FIG. 3 in a communication environment in which the communication stations 0 to F set TBTT in each slot capable of accommodating a maximum of 16 stations. This means that “the beacon from the communication station 1 and the communication station 9 can be received” is transmitted. That is, for each bit of the NBOI corresponding to the relative position of the reception beacon, a mark is allocated when the beacon can be received, and a space is allocated when the beacon is not received. The MSB is 1 because the own station is transmitting a beacon, and a place corresponding to the time at which the own station is transmitting a beacon is also marked.

  When each communication station receives each other's beacon signal on a certain channel, based on the description of the NBOI included therein, each communication station arranges its own beacon transmission timing while avoiding a beacon collision on the channel, or a neighboring station. Beacon reception timing can be detected.

  FIG. 13 shows a state where the newly entered communication station sets its own TBTT based on the NBOI of each beacon obtained from the beacon received from the peripheral station.

  After turning on the power, the communication station first attempts to receive a signal over a scanning operation, that is, the transmission frame length or longer, and confirms the presence of a beacon transmitted by the peripheral station. In this process, if a beacon is not received from a peripheral station, the communication station sets an appropriate timing as TBTT. On the other hand, when a beacon transmitted from a peripheral station is received, the NBOI field of each beacon received from the peripheral station is referred to by taking a logical sum (OR) while shifting according to the reception time of the beacon. The beacon transmission timing is extracted from the timing corresponding to the bit positions that are not finally marked.

  In the example illustrated in FIG. 13, attention is paid to the newly appearing communication station A, and a communication environment in which the communication station 0, the communication station 1, and the communication station 2 exist around the communication station A is assumed. Then, it is assumed that the communication station A has received the beacons from the three stations 0 to 2 in the transmission frame by the scanning operation.

  The NBOI field is described in the bitmap format in which the beacon reception time of the peripheral station is mapped to the relative position with respect to the beacon of the local station (described above). Therefore, the communication station A shifts the NBOI fields of the three beacons that can be received from the peripheral station according to the reception time of each beacon, aligns the corresponding positions of the bits on the time axis, and then sets the NBOI bits at each timing. Take the OR of

  As a result of integrating and referencing the NBOI fields of the peripheral stations, the obtained sequence is “1101,0001,0100,1000” indicated by “OR of NBOIs” in FIG. The relative position at the timing when TBTT has already been set, and 0 indicates the relative position at the timing when TBTT is not set. In this series, the longest run length of space (zero) is 3, and there are two candidates. In the example shown in FIG. 13, the communication station A defines the 15th bit in the TBTT of its own beacon.

  The communication station A sets the time of the 15th bit as the TBTT of its regular beacon (that is, the head of its own transmission frame) and starts transmitting a beacon. At this time, the NBOI field transmitted by the communication station A marks the reception time of the beacons of the communication stations 0 to 2 capable of receiving beacons and the bit position corresponding to the relative position from the transmission time of the regular beacon of the local station. It is described in a bitmap format and is as indicated by “NBOIfor TX (1 Beacon TX)” in FIG.

  The present invention relates to a multi-channel autonomous distributed network, and requires NBOI information describing beacon arrangement for each available frequency channel, which will be described later.

  FIG. 14 shows a state in which a new entry 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. 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. 14 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. 14 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.

  14 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.

  And as shown in FIG. 15, STA2 determines beacon transmission timing in the middle of the beacon interval of STA0 and STA1 at this time. 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.

C. As access operation described above under a multi-channel environment, the autonomous distributed wireless communications system, with each communication station notifies beacon information in the transmission frame period, to perform a scanning operation of the beacon signal from another station Thus, the network configuration on one channel can be recognized.

  However, the multi-channel autonomous distributed network according to the present embodiment has a configuration in which transmission frames as shown in FIG. 4 are arranged on the frequency axis by the number of used channels (see FIG. 16). ). 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 the present embodiment, the level information of the interference received by the local station is transmitted on the beacon signal periodically transmitted by each communication station, and the interference status is grasped based on the beacon information received from the peripheral station. The communication channel is determined above. For example, the communication channel is controlled in an autonomous and distributed manner by avoiding the use of a channel in which peripheral communication stations are severely interfered as a communication channel.

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

  In the wireless communication system shown in the figure, three channels # 1 to # 3 are prepared as usable channels, but channel # 1, channel # 2, and channel # 3 are provided on the left and right sides of the space. Interfering stations serving as interfered channels are respectively arranged.

  In communication station # 2 and communication station # 3 arranged in the approximate center of this space, beacons can be heard on all channels. Also, in communication station # 1, channel # 1 and channel # 2 are interfered channels, and in communication station # 4, channel # 3 is an interfered channel, but the beacon signal transmitted at the lowest rate is Receivable interference level.

  Communication station # 2 can receive the beacon from each station and acquire interference information for each channel in each station. Then, using the channel # 3 through which all communication stations can transmit beacons, their own beacon signals are transmitted.

  Further, the communication station # 2 may perform the data transmission operation using a channel other than the beacon transmission channel. For example, when transmitting traffic to the communication station # 4, after transmitting a beacon using the channel # 3, the communication station # 4 moves to the channel # 1 or the channel # 2 having a low interference level, Start sending.

  As described above, in the multi-channel autonomous distributed wireless network according to the present embodiment, as many communication stations as possible based on the interference information of each channel described in the beacon signal at the time of new entry or refresh. The channel that can be received is selected as the beacon transmission channel. If there is a peripheral station that cannot receive a beacon, it tries to change the beacon transmission channel.

  In this way, by performing a beacon transmission operation using a channel that can be received by as many communication stations as possible as a beacon transmission channel, more communication stations can receive each other's beacons and recognize their existence, and dead It is possible to avoid falling into the locked state as much as possible.

  Further, each communication station does not need to switch channels during a period when there is no transmission data and only beacon reception is performed. The communication station can reduce the overhead of channel transition by using the same communication channel as that of the peripheral communication station as much as possible if the interference received by the local station is at an allowable level. Since the channel shift requires a delay time of about 300 microseconds in terms of hardware operation, the communication capacity can be increased by reducing the number of channel shifts.

  In addition, the communication station may determine the beacon transmission channel depending on, for example, whether the local station requires a wide band. For example, when the own station requires a wide band, a channel having a low interference level for itself is selected as much as possible without being used by another communication station, and beacon transmission is started. The same operation is performed on both the transmitting side and the receiving side.

  On the other hand, a communication station that does not need a wide band should transmit a beacon on the same channel as possible as a peripheral station in consideration of overhead at the time of channel change. Pay attention to the most channels).

  When the peripheral station including itself does not receive a large interference on the most frequent channel, beacon transmission is started on that channel. In addition, if there are multiple communication stations that have received a large amount of interference that cannot be received by the beacon transmitted at the lowest rate, select the channel with the lowest average interference level and start transmitting the beacon there. To do.

  Each communication station regularly refreshes the communication channel to the optimum one by performing this operation periodically.

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

  First, a scanning operation is performed on each channel according to a predetermined procedure, and reception of a beacon signal transmitted from a peripheral station is attempted (step S1).

  Here, when the beacon signal of the peripheral station can be found (step S2), it is then determined whether or not the local station needs a wide band (step S3). Whether or not a wide band is necessary is determined in consideration of both the transmitting side and the receiving side of the local station.

  When the local station does not need a wide band, pay attention to the channel (the most frequent channel) where the most communication stations among the peripheral stations transmit beacons (step S4), and the peripheral including the self in the most frequent channel. It is further determined whether or not the station is receiving large interference (step S5).

  Here, when the peripheral station including the own station does not receive large interference in the most frequent channel, the most frequent channel is selected (step S6), and beacon transmission is started on the channel (step S7).

  Further, when there are a plurality of communication stations receiving a large amount of interference in the most channels, the channel having the lowest average interference level is selected (step S10), and beacon transmission is started there (step S7).

  If it is determined in step S3 that the local station requires a broadband communication capacity, a channel having a low interference level for the local station is selected as much as possible and is not used by another communication station (step S9). Is started (step S7). The same operation is performed on both the transmitting side and the receiving side.

  In step S2, if a beacon signal from a peripheral station is not found, a channel optimum for the own station, specifically, a channel having the lowest interference level for the own station is selected as a beacon transmission channel ( Step S8), beacon transmission is started (step S7).

  When the regular refresh time arrives (step S11), the communication station returns to step S1 and repeats the beacon transmission channel selection operation. As described above, the communication station regularly refreshes the communication channel to the optimum one by periodically performing the above-described operation.

  Next, an operation of the communication station performing channel change in time series in the multi-channel autonomous distributed wireless network according to the present embodiment will be described.

  In the autonomous distributed wireless communication system according to the present embodiment, the priority transmission period (TPP) arranged immediately after the beacon transmission timing on each channel, and the RAP based on CSMA / CA in each period of FAP following TPP. Access. At this time, the RTS / CTS method can be adopted as a means for assigning a priority transmission right according to an inter-frame space and avoiding a collision and improving communication quality (see, for example, FIGS. 7 and 8).

  In the RTS / CTS method, prior to transmission of net information, the transmission source communication station transmits RTS (Request to Send), and the reception communication station can receive this RTS and receive data. As a response, CTS (Clearto Send) is returned. 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 one 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, An RTS signal and a multiplexed beacon signal (a beacon signal including information on a channel performing data communication) are transmitted.

  This beacon signal functions as an RTS signal in a pseudo manner. In response to receiving a beacon in which an RTS signal is multiplexed on a beacon transmission channel (a beacon including channel information for performing data communication), the hidden terminal refrains from performing a data transmission operation for a predetermined time. Interference can be avoided.

  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. 21 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 transmits an RTS signal in order to avoid a hidden terminal problem associated with performing a data transmission operation by shifting to a channel with a low interference level for the data transmission destination communication station. Prior to this, on the beacon transmission channel of the local station, the RTS signal and a beacon multiplexed (a beacon including channel information for performing data communication) are transmitted.

  At this time, if the beacon transmission channel of the data transmission source matches the beacon transmission channel of the communication station of the data transmission destination, the beacon obtained by multiplexing the RTS signal is regarded as a pseudo RTS signal itself.

  At this time, if the beacon transmission channel of the data transmission source matches the channel for data transmission, the RTS signal multiplexed beacon (beacon including channel information for data communication) is regarded as the RTS signal itself. .

  In addition, the communication station of the data transmission destination does not wait for the arrival of the normal RTS signal in response to receiving the beacon in which the RTS signal is multiplexed (the beacon including the channel information performing data communication). The data transmission can be started by returning the CTS signal.

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

  22 to 24 show, in the form of flowcharts, processing procedures for the wireless communication device 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 S31), the mobile station shifts to the beacon transmission channel of the peripheral station and receives the beacon (step S32). ).

  When the beacon transmission timing of the local station comes (step S21), 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 S22). If there is no transmission request, a beacon is transmitted on the beacon transmission channel that is optimum for itself (step S33).

  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 (a beacon including channel information on which data communication is performed) is multiplexed. ) At a predetermined beacon transmission timing (step S23).

  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 S24).

  Here, if the beacon transmission channels do not match each other, the RTS signal is transmitted (step S35) after shifting to the beacon transmission channel of the data transmission destination communication station (step S34). On the other hand, when the beacon transmission channels match each other, a beacon obtained by multiplexing the RTS signal (a beacon including channel information for performing data communication) is regarded as the RTS signal itself, and transmission of a regular RTS signal is performed. The channel transition operation is omitted. Then, it waits for a CTS signal from the data transmission destination communication station (step S25).

  If the CTS signal cannot be received within a predetermined time (step S26), the process proceeds to step S35, and the RTS signal is retransmitted.

  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 S27). Then, it is checked whether or not there is a further transmission request from the upper layer (step S28). When the transmission request is completed, the process returns to step S21 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 or not there is still room until the beacon transmission timing of the own station (step S29). If there is no room, the process returns to step S21 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 S30).

  When there is a margin until the beacon transmission timing of the own station and the peripheral station (step S30), the process proceeds to step S35, where the RTS signal is transmitted and the data communication operation is continued.

  When there is no allowance for the beacon transmission timing of the peripheral station, if the currently used channel and the beacon transmission channel of the peripheral station are different, the channel shifts (steps S36 and S37), and the beacon is received (step S38).

  Then, after receiving the beacon of the peripheral station, it is checked whether the beacon transmission channel of the peripheral station that is the transition destination matches the use channel that the local station has used so far for data transmission (step) S39). If the beacon transmission channels do not coincide with each other, the process proceeds to step S34, transitions to the beacon transmission channel of the data transmission destination communication station, transmits the RTS signal (step S35), and resumes the data communication operation. When the beacon transmission channels match each other, the priority transmission section of the beacon transmission station is set, and the communication station cannot resume the data communication operation. In this case, the process returns to step S21, and the beacon transmission operation is performed under the steady operation mode.

  By setting a beacon transmission channel according to the procedure shown in FIG. 18, in a multi-channel autonomous distributed network, a communication station can set a more optimal channel as its own beacon transmission channel. it can. Also, according to the communication operation procedure shown in FIGS. 22 to 24, the communication station transmits a beacon at a predetermined transmission frame period to grasp the existence of the peripheral station and notify the network state, and Data communication according to the RTS / CTS method can be performed while shifting to a beacon transmission channel in accordance with the transmission timing and performing a beacon reception operation.

  Here, switching the channel requires about 300 microseconds in terms of hardware operation. For this reason, when a communication station in data communication interrupts data communication in order to receive the beacon of another station, performs channel shift and beacon reception, then shifts to the original usage channel and resumes data communication. , The overhead gets bigger.

  In FIG. 25, a communication station in data communication interrupts data communication in order to receive a beacon of another station, performs channel shift and beacon reception, then shifts to the original channel and resumes data communication. An operation example is shown.

  As shown in the figure, on the channel CH2, in response to the transmission of the RTS packet from the communication station # 2 that is the data transmission source and the return of the CTS packet from the communication station # 3 that is the data transmission destination, Station # 2 starts a data packet transmission operation.

  Here, when the beacon transmission timing TBTT by the peripheral station # 1 approaches on another channel CH3, the communication station # 2 (and the communication station # 3) does not change whether the transmission data continues or not. It spends T_CHCH and moves to channel CH3 to receive a beacon.

  The communication station # 1, which is a beacon transmission station, acquires the priority transmission right and starts a preferential data transmission operation according to the RTS / CTS procedure on the channel CH3 within the TPP interval.

  On the other hand, when the communication station # 2 (and the communication station # 3) recognizes that the priority transmission operation is performed on the channel CH3 by the reception of the RTS packet and the data communication can be continued on the data communication channel CH2 of the local station. The channel transition time T_CHCH is consumed to return to the channel CH2. Then, in response to the transmission of the RTS packet from the communication station # 2 and the return of the CTS packet from the communication station # 3, the communication station # 2 resumes the data packet transmission operation.

  As shown in FIG. 25, in a multi-channel communication environment, the overhead of data communication increases with the reception of beacons by peripheral stations. On the other hand, there may be a situation where a beacon from a peripheral station that is not a partner of data communication is not necessarily received every time.

  Therefore, as a modification of the communication operation procedure described above, when the communication station grasps that the beacon transmission timing of another station is approaching, it determines whether or not it is necessary to communicate with the beacon transmission station. If it is not necessary to receive a beacon and the currently used channel is different from the beacon transmission channel, it is proposed to omit the beacon receiving operation.

  In this way, by omitting unnecessary beacon reception operations, the time required for beacon transition and the power consumption of the apparatus can be omitted, and the communication capacity can be increased.

  Here, in this embodiment, traffic traffic is managed in an autonomous and distributed manner by giving a preferential communication right to the beacon transmission station (described above), but the beacon transmission station does not necessarily have to be TPP on the beacon transmission channel. You may not always win. That is, the beacon transmitting station may shift the channel used preferentially to a channel optimal for traffic transmission different from the beacon transmission channel according to the interference state on the receiving side.

  For this reason, there is a problem that if the communication station omits the beacon reception operation, such a channel shift operation cannot be recognized.

  Therefore, when the beacon reception operation is omitted, the communication station estimates the RTS and CTS signal transmission timing based on the beacon transmission timing, performs the reception operation on the channel currently used only for these timings, Detects whether the transmitting station has shifted to the channel currently used.

  When the communication station detects that the beacon transmission station has shifted to the channel currently used at the transmission timing of the RTS and CTS signals, the communication station refrains from the data communication operation of the local station, thereby Avoid collisions. On the other hand, if not detected, the beacon transmitting station recognizes that it has acquired the priority transmission right on another channel, and continues its own data communication operation on the currently used channel. Do.

  Thus, when the beacon reception operation of the other station is omitted, the beacon transmission station performs the reception operation according to the priority transmission period acquired by the beacon transmission, without performing unnecessary channel transition, and Communication collision can be avoided.

  FIG. 26 shows an operation example for the communication station performing data communication to omit the beacon reception of other stations.

  As shown in the figure, on the channel CH2, in response to the transmission of the RTS packet from the communication station # 2 that is the data transmission source and the return of the CTS packet from the communication station # 3 that is the data transmission destination, Station # 2 starts a data packet transmission operation.

  Here, when beacon transmission timing TBTT by peripheral station # 1 approaches on another channel CH3, does communication station # 2 (and communication station # 3) need to receive a beacon from peripheral station # 1? Judge whether. If it is not necessary to receive a beacon and the currently used channel CH2 is different from the beacon transmission channel CH3, the beacon receiving operation is omitted.

  Then, the communication station # 2 (and the communication station # 3) continues the data transmission operation only for a period corresponding to the channel transition time T_CHCH, and then transmits the RTS and CTS signals after the beacon transmission timing TBTT by the peripheral station # 1. Timing is estimated, and reception operation is performed on the channel CH2 currently used only at these timings, and it is detected whether or not the beacon transmitting station has shifted to the channel currently used.

  In the example shown in the figure, the communication station # 1, which is a beacon transmission station, shifts to a channel CH4 that is optimal for traffic transmission different from the beacon transmission channel CH3, and the channel CH4 within the TPP interval based on the acquired priority transmission right. The preferential data transmission operation is started according to the RTS / CTS procedure.

  On the other hand, the communication station # 2 (and the communication station # 3) did not detect during the standby period in which the arrival of the RTS and CTS packets is estimated on the currently used channel CH2, so that the beacon transmission station # 1 is different. Recognizes that the priority transmission right is acquired on the channel. In this case, the data communication operation of the own station can be resumed on the currently used channel. It should be appreciated that data communication can be resumed with the end of the standby period without spending channel transition time T_CHCH.

  When the communication station performs the communication operation as shown in FIG. 26, the communication operation procedure in the transmission continuation state is corrected to the flowchart shown in FIG. 27 instead of FIG.

  After the data transmission is executed in step S27, when the transmission request from the upper layer continues (step S28), the mode transits to the transmission continuation mode. Then, it is checked whether or not there is still room until the beacon transmission timing of the own station (step S29). If there is no room, the process returns to step S21 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 S30).

  When there is a margin until the beacon transmission timing of the own station and the peripheral station (step S30), the process proceeds to step S35, where the RTS signal is transmitted and the data communication operation is continued.

  On the other hand, when there is no allowance for the beacon transmission timing of the peripheral station (that is, when the beacon transmission timing of the other station is approaching), the currently used channel and the beacon transmission channel of the peripheral station are the same. Is determined (step S40).

  If the currently used channel and the beacon transmission channel of the peripheral station are the same, a beacon is received on this channel (step S38).

  On the other hand, when the currently used channel and the beacon transmission channel of the peripheral station are different (step S40), it is further determined whether it is necessary to communicate with the beacon transmission station (step S41).

  Here, when it is determined that it is necessary to receive a beacon, if the beacon transmission channel of the peripheral station is different, the channel shifts (step S37), and the beacon is received (step S38).

  Then, after receiving the beacon of the peripheral station in step S38, it is checked whether or not the beacon transmission channel of the peripheral station that is the transition destination matches the use channel that the local station has used so far for data transmission. (Step S39). If the beacon transmission channels do not coincide with each other, the process proceeds to step S34, transitions to the beacon transmission channel of the data transmission destination communication station, transmits the RTS signal (step S35), and resumes the data communication operation. When the beacon transmission channels match each other, the data transmission operation cannot be resumed because the beacon transmission station has a preferential transmission period. In this case, the process returns to step S21, and the beacon transmission operation is performed under the steady operation mode.

  On the other hand, if it is determined in step S41 that it is not necessary to receive a beacon, and if the currently used channel is different from the beacon transmission channel, the beacon receiving operation is omitted. In this way, by omitting unnecessary beacon reception operations, the time required for beacon transition and the power consumption of the apparatus can be omitted, and the communication capacity can be increased.

  Here, the beacon transmission station does not necessarily acquire TPP on the beacon transmission channel. In other words, the beacon transmitting station may shift to the current use channel of its own station and acquire the priority transmission section TPP. Therefore, if the beacon receiving operation is omitted and data communication is continued, communication may collide. There is sex.

  Therefore, when the beacon reception operation is omitted, the communication station estimates the transmission timing of the RTS and CTS signals based on the beacon transmission timing, and performs the reception operation on the currently used channel only at these timings (steps). S42), it is detected whether or not the beacon transmitting station has shifted to the currently used channel.

  When the RTS and CTS signals are received at the transmission timing of the RTS and CTS signals (step S43), the beacon transmitting station recognizes that it has shifted to the channel currently used, and the data communication operation of its own station Is interrupted (step S44) to avoid a communication collision. In this case, the process returns to step S21, and the beacon transmission operation is performed under the steady operation mode.

  On the other hand, when the communication station does not receive the RTS and CTS signals at the transmission timing of the RTS and CTS signals (step S43), the communication station recognizes that the beacon transmitting station has acquired the priority transmission right on another channel. To do. In this case, the process returns to step S35, and the data communication operation of the own station on the currently used channel is continuously performed by transmitting the RTS signal.

[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 inter-frame space. FIG. 6 is a diagram showing a state in which priority is given to the beacon transmitting station. FIG. 7 is a diagram for explaining an operation for a beacon transmitting station and other stations in the TPP section to obtain a transmission right. It is a figure for demonstrating the operation | movement for a communication station to start transmission in a TPP area and a FAP area, respectively. FIG. 9 is a diagram showing the configuration of the transmission frame period. FIG. 10 is a diagram illustrating an operation when the beacon transmitting station abandons TPP. FIG. 11 is a diagram illustrating a configuration example of a beacon signal format. FIG. 12 is a diagram illustrating a description example of the NBOI. FIG. 13 is a diagram illustrating a state in which a newly entered communication station sets its own TBTT based on the NBOI of each beacon obtained from the beacons received from the peripheral stations. FIG. 14 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. 15 is a diagram illustrating 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. 16 is a diagram schematically illustrating a transmission frame configuration of an autonomous distributed multi-channel wireless communication system. FIG. 17 is a diagram illustrating a state in which two or more communication stations are arranged in an interference environment. FIG. 18 is a flowchart showing an operation procedure for a communication station to select a beacon transmission channel in the multi-channel autonomous distributed wireless network according to the present invention. FIG. 19 is a diagram showing an operation sequence of the RTS / CTS method. FIG. 20 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. 21 is a diagram illustrating another example in which the RTS / CTS scheme is applied to a multi-channel autonomous distributed wireless network according to the present invention. FIG. 22 is a flowchart showing a processing procedure (but a steady state) 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. 23 is a flowchart showing a processing procedure (however, a transmission start state) for the wireless communication device 100 to operate autonomously as a communication station in the multipath autonomous distributed wireless network according to the present invention. FIG. 24 is a flowchart illustrating a processing procedure (however, a transmission continuation state) for the wireless communication device 100 to operate autonomously as a communication station in the multipath autonomous distributed wireless network according to the present invention. FIG. 25 shows an operation in which a communication station in data communication interrupts data communication in order to receive a beacon of another station, performs channel shift and beacon reception, and then shifts to the original channel and resumes data communication. FIG. FIG. 26 is a diagram illustrating an operation for a communication station that is performing data communication to omit beacon reception by another station. FIG. 27 shows 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 (provided that beacon reception is omitted in the transmission continuation state). It is a flowchart.

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 (5)

A wireless communication device that operates in an autonomous and distributed manner in a wireless communication environment in which a plurality of channels are prepared and a specific control station is not disposed,
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 data transmission and reception in the communication means;
Beacon analyzing means for analyzing a beacon signal received from a peripheral station;
Comprising a communication control means for controlling the communication operation on the multi-channel,
When the communication control means grasps that the beacon transmission timing of the other station is approaching, it determines whether it is necessary to communicate with the beacon transmission station, and does not need to receive a beacon. If the channel used by the local station is different from the beacon transmission channel, the beacon reception operation is omitted.
A wireless communication apparatus. In the wireless communication environment, the data transmission source communication station transmits a transmission request packet RTS, and RTS / CTS starts data transmission in response to reception of the confirmation notification packet CTS from the data transmission destination communication station. Method is adopted,
When the communication control means omits the operation of receiving beacons from other stations, the communication control means estimates the transmission timings of the RTS and CTS signals based on the beacon transmission timings, and the channel currently used by the local station only at these timings. Receive operation,
The wireless communication apparatus according to claim 1. A wireless communication method for autonomously distributed operation in a wireless communication environment in which a plurality of channels are prepared and a specific control station is not disposed,
A beacon transmission step of setting a beacon transmission channel of the local station and transmitting a beacon;
A beacon reception control step for controlling beacon reception operation from a peripheral station;
A beacon analysis step for analyzing a beacon signal received from a peripheral station;
A communication control step of setting a data communication channel and controlling data communication operation;
The beacon reception control step includes:
A sub-step for grasping that the beacon transmission timing of another station is approaching,
A sub-step for determining whether it is necessary to communicate with the beacon transmitting station;
Including a sub-step in which it is not necessary to receive a beacon and the currently used channel is different from the beacon transmission channel, omitting the beacon receiving operation.
A wireless communication method. In the wireless communication environment, the data transmission source communication station transmits a transmission request packet RTS, and RTS / CTS starts data transmission in response to reception of the confirmation notification packet CTS from the data transmission destination communication station. Method is adopted,
In the communication control step, when the beacon reception operation from other stations is omitted, the transmission timing of the RTS and CTS signals is estimated based on the beacon transmission timing, and the reception operation is performed on the channel currently used only by these timings. Do,
The wireless communication method according to claim 3. A computer program that is written in a computer-readable format so that a plurality of channels are prepared and processing for autonomously distributed operation in a wireless communication environment in which no specific control station is arranged is executed on a computer system. And
A beacon transmission step of setting a beacon transmission channel of the local station and transmitting a beacon;
A beacon reception control step for controlling beacon reception operation from a peripheral station;
A beacon analysis step for analyzing a beacon signal received from a peripheral station;
A communication control step of setting a data communication channel and controlling data communication operation;
The beacon reception control step includes:
A sub-step for grasping that the beacon transmission timing of another station is approaching,
A sub-step for determining whether it is necessary to communicate with the beacon transmitting station;
Including a sub-step in which it is not necessary to receive a beacon and the currently used channel is different from the beacon transmission channel, omitting the beacon receiving operation.
A computer program characterized by the above.