JP4311262B2 - COMMUNICATION SYSTEM AND COMMUNICATION METHOD, COMMUNICATION DEVICE, COMMUNICATION CONTROL METHOD, AND COMPUTER PROGRAM - Google Patents

Description

  The present invention relates to a communication system and a communication method in which a plurality of wireless communication stations operate in an autonomous distributed control manner to form a wireless network having a plurality of communication channels, and perform data communication between the plurality of wireless communication stations, and In particular, the present invention relates to a communication apparatus and communication control method used in these communication systems and communication methods, and a computer program, and in particular, a communication system and communication method suitable for application to a so-called wireless LAN (Local Area Network), communication apparatus, and The present invention relates to a communication control method and a computer program.

  In recent years, for example, wireless communication technology for wirelessly connecting various information processing terminal devices such as personal computers and portable information terminals and their peripheral devices has been developed. As a typical example, so-called IEEE (Institute) is developed. of Electrical and Electronics Engineers) 802.11 wireless LANs compliant with the 802.11 system are becoming widespread.

  In the IEEE802.11 wireless LAN, as a media access control (MAC) technology related to protocols such as distributed control or centralized control of the data link layer, contention free that performs media access control by polling is used. There are standardized sections and contention sections that perform media access control by carrier sense. Of these, the contention section for performing carrier sense is widely used.

  As this contention section, a CSMA / CA (Carrier Sense Multiple Access Collision Aidance) system that follows the autonomous distributed control system used in so-called Ethernet (registered trademark) is standardized. In general, the CSMA / CA scheme is a communication channel in which a communication station trying to transmit data performs carrier sense in advance so that it does not collide with data transmitted by other communication stations. In this technique, data is transmitted if the bandwidth is not used, and data transmission is postponed until an idle state is reached if the bandwidth is in use. In the wireless LAN of the IEEE 802.11 system, as a networking method based on the concept of so-called BSS (Basic Service Set), an access point (Access Point: AP) as a control station exists, and a radio wave reachable range of the access point Are defined as an infrastructure mode for controlling a plurality of terminals (STAs) existing in the network and an ad hoc mode in which a plurality of terminals operate in an autonomous distributed control manner without an access point. Both the access point and the plurality of terminals communicate with each other by following a procedure compliant with the CSMA / CA system.

  Here, a specific communication operation in an IEEE 802.11 wireless LAN will be described.

  First, the operation in the infrastructure mode will be described.

  In an infrastructure mode BSS, an access point that coordinates in the system is essential. In the infrastructure mode, for example, as shown in FIG. 19, the radio wave reachable range of the access point STA0 is gathered as BSS, which constitutes a cell corresponding to a so-called cellular system. As a result, the terminals STA1 and STA2 belonging to the radio wave coverage of the access point STA0 enter the network as members of the BSS. Then, the access point STA0 transmits a control signal called a beacon at a predetermined time interval. Each terminal STA1 and STA2 receives this beacon signal, recognizes that the access point STA0 exists in the vicinity, and establishes a connection with the access point STA0.

  As described above, the access point STA0 transmits a beacon signal at a predetermined time interval, and the transmission time of the next beacon signal is within the beacon signal called Target Beacon Transmission Time (TBTT). It is determined using the parameters to be described. Each terminal STA1 and STA2 can grasp the transmission time of the next beacon signal by receiving the beacon signal and referring to the TBTT. Thereby, each terminal STA1 and STA2 can also switch to the sleep state by turning off the power of the receiver until the next time or a plurality of forward TBTTs, for example, when reception is not necessary.

  Next, the operation in the ad hoc mode will be described.

  In the ad hoc mode, each terminal autonomously defines an IBSS (Independent BSS) by performing a predetermined negotiation with another terminal. In the ad hoc mode, for example, as shown in FIG. 20, when the IBSS is defined, the terminals STA1 and STA2 determine TBTT at predetermined time intervals at the end of the negotiation. When each terminal STA1, STA2 recognizes that the time has reached TBTT by referring to its own clock, other terminals are transmitting beacon signals after a time delay determined by a uniform random number. When it is recognized that there is no beacon, a beacon signal is transmitted.

  Also in IBSS, each terminal STA1 and STA2 can transition to a sleep state by turning off the power of the transceiver until next time or a plurality of TBTTs as necessary. In the IEEE 802.11 system, when the sleep mode is applied in the IBSS, a predetermined time zone from the TBTT is defined as an ATIM (Annunciation Traffic Indication Message) window.

  All the terminals belonging to the IBSS operate the receiver during the time period of the ATIM window, and basically, even when operating in the sleep mode during this time period, reception is performed. It is possible. When each terminal has data to be transmitted to an arbitrary terminal, a beacon signal is transmitted in the time zone of this ATIM window, and then an ATIM packet is transmitted to the arbitrary terminal. Then, it notifies the arbitrary terminal that it has data to be transmitted. Then, the terminal that has received the ATIM packet operates the receiver until the reception from the terminal that has transmitted the ATIM packet is completed.

  Here, the communication operation using the ATIM window will be specifically described with reference to FIG. In the example shown in FIG. 21, three terminals STA1, STA2, and STA3 exist in the IBSS. In this case, when the time reaches TBTT, each terminal STA1, STA2, and STA3 operates a back-off tag provided for data collision avoidance while monitoring the media state over a time determined by a uniform random number. . In the illustrated example, the case where the timer of the terminal STA1 finishes counting earliest and the terminal STA1 transmits a beacon signal is shown. In this case, since the other terminals STA2 and STA3 have recognized that the terminal STA1 has transmitted a beacon signal, they do not transmit a beacon signal.

  Here, it is assumed that the terminal STA1 has data destined for the terminal STA2, and the terminal STA2 has data destined for the terminal STA3. In this case, first, each of the terminals STA1 and STA2 ends the transmission / reception of the beacon signal, and operates the back-off timer while monitoring the media state over the time determined by the uniform random number again. Here, assuming that the timer of the terminal STA2 has finished counting earliest, the terminal STA2 transmits an ATIM packet to the terminal STA3. Accordingly, when receiving the ATIM packet, the terminal STA3 transmits a so-called ACK (Acknowledgement) signal after a predetermined time SIFS (Short Inter Frame Space) has elapsed. Then, when the transmission of the ACK signal from the terminal STA3 is completed, the terminal STA1 further operates the back-off timer while monitoring the media state over the time determined by the uniform random number, and the time set in this timer When elapses, an ATIM packet is transmitted to the terminal STA2. In response to this, when receiving the ATIM packet, the terminal STA2 transmits an ACK signal after a predetermined time SIFS.

  In the wireless LAN of the IEEE 802.11 system, when such transmission / reception of the ATIM packet and the ACK packet is performed within the time zone of the ATIM window, the terminal STA3 receives data from the terminal STA2 even in the subsequent section. Therefore, the receiver STA2 operates the receiver to receive data from the terminal STA1. A terminal that has not received an ATIM packet within a time zone of the ATIM window or a terminal that does not have data to be transmitted can turn off the transceiver until the next TBTT, thereby reducing power consumption. .

  As a technique related to access control when performing such wireless communication, there is a technique described in Patent Document 1, for example. In this document, in response to an inquiry about the radio status of the master unit, the slave unit detects the presence / absence of a control signal radio signal of another master unit between the control signal transmission timings of the master unit, and transmits the radio wave presence information to the master unit. The reporting technique is disclosed. In the same document, when a control signal radio wave of another base unit exists, the base unit detects a time difference between the transmission timing and the transmission timing of the own station, and the detected time difference is determined in advance. A technique for changing the control signal transmission timing of the parent device when the value is equal to or less than the specified value is disclosed.

JP-A-8-217914

  By the way, in the wireless LAN of the IEEE 802.11 system, a license-free band such as a so-called 5.2 GHz band or 2.4 GHz band is used. These bands are further divided into a plurality of bands, and each communication station performs communication using one of the divided bands. For example, in IEEE802.11a, a 5.2 GHz band is divided into four bands of 20 MHz, and a terminal that performs wireless communication selects one of the divided bands as a communication channel. Become.

  Here, in the wireless LAN of the IEEE802.11 system, as described above, communication is started after confirming a free communication channel by following a procedure compliant with the CSMA system. Must use the same communication channel. Therefore, in the wireless LAN, although a plurality of communication channels are prepared by dividing the band, the communication channels actually used for signal transmission are substantially only for one channel.

  In addition, since these bands are unlicensed bands, there may be situations where wireless LANs with different systems use the same communication channel. In such a case, it is possible to avoid interference from other systems by changing the communication channel of the own system, but in order to realize this, it is necessary to detect the presence of other systems.

  In a situation where there are a plurality of such systems, there is a technique described in Patent Document 2, for example, as a technique for selecting a free communication channel to avoid interference from other systems.

JP 2002-158667 A

  In Patent Document 2, the optimum channel is determined by judging the radio wave conditions of all the wireless channels that can be used when the master station is started up, and the transmission of the own network is periodically stopped, and the slave stations are dispersed and nearby. A technique for selecting an optimum channel with respect to a change in ambient conditions by monitoring the radio wave condition of the network is disclosed.

  Here, as a wireless communication system different from the wireless LAN, there is a mobile phone system such as a so-called PDC (Personal Digital Cellular). In these mobile phone systems, terminal control information is centrally managed by the base station, and the communication time and communication channel are controlled for each terminal.

  In such a cellular phone system or a system that adopts a centralized control system such as an infrastructure mode in an IEEE802.11 wireless LAN, the burden on base stations and access points for centralized control is large and large-scale. The cost required for system construction also increases. Further, in a system that employs such a centralized control method, there is a problem that the network cannot be easily constructed.

  On the other hand, if the system adopts an autonomous distributed control system such as an ad hoc mode in an IEEE 802.11 wireless LAN, each terminal independently determines the surrounding situation and easily expands the network. be able to.

  However, conventional techniques related to communication channel selection, including the technique described in Patent Document 2 described above, assume a centralized control system based on base stations, access points, etc., and adopt an autonomous distributed control system. It cannot be applied to a system that does this.

  As described above, in a system adopting the autonomous distributed control method, it is not possible to use a plurality of communication channels at the same time while using an access control method based on carrier sense like the CSMA method. There is a problem that there is a limit.

  The present invention takes into account the technical problems as described above, and its main purpose is to employ an access control method based on carrier sense when adopting an autonomous distributed control method and performing wireless communication, It is an object to provide an excellent communication system and communication method, communication apparatus and communication control method, and computer program capable of simultaneously using a plurality of communication channels and increasing communication capacity.

A first aspect of the present invention is a communication system in which a plurality of communication stations each operate in an autonomous distributed control manner to form a network using a plurality of communication channels,
Each communication station manages at least time information related to the transmission / reception time of the beacon signal and communication channel information related to the communication channel to be used,
Transmitting communication station attempting to transmit the beacon signals or data, switches the communication channel to use based on the time information and the communication channel information, and transmission of a beacon signal or data,
A receiving communication station trying to receive a beacon signal or data switches a communication channel to be used based on the time information and the communication channel information, and receives a beacon signal or data.
This is a communication system characterized by the above.

  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 the communication system according to the present invention, communication can be performed by being distributed over a plurality of communication channels, so that an increase in communication capacity can be expected and the communication channel can be switched according to the interference situation for each communication channel. . In the communication system according to the present invention, since a network can be formed by autonomous distributed control while using a plurality of communication channels, the network can be easily formed and the cost can be reduced. Can do.

Here, in the beacon signal, time information and communication channel information known by the wireless communication station that transmits the beacon signal are described. Therefore, a wireless communication station newly entering the network appropriately grasps the status of the other wireless communication station based on the time information and communication channel information described in the beacon signal received from the other wireless communication station. The time and communication channel at which other wireless communication stations are communicating can be grasped.

  Then, the wireless communication station that newly enters the network determines the transmission time of the beacon signal transmitted by itself and the communication channel to be used based on the grasped time information and communication channel information.

  Specifically, a wireless communication station newly entering the network overlaps all time information and communication channel information described in a beacon signal received from another wireless communication station, and is already used in the other communication station. The peripheral station use time zone information related to the current time zone is created. Then, based on the created peripheral station use time zone information, the transmission time of the beacon signal transmitted by itself and the communication channel to be used are determined.

  Thereby, in the communication system according to the present invention, it is possible to avoid a situation in which a beacon signal is transmitted at the time and communication channel at which another wireless communication station receives the beacon signal.

In addition, a wireless communication station that newly enters the network selects the time at which the interval at which beacon signals are transmitted and received is the maximum as the transmission time at which the beacon signal is transmitted based on the created peripheral station usage time zone information To do. Furthermore, a wireless communication station that newly enters the network divides the created peripheral station use time zone information into peripheral station use time zone information for each communication channel, and evaluates the transmission time of the selected beacon signal for each communication channel. The communication channel having the maximum interval for transmitting and receiving the beacon signal is selected as the communication channel for transmitting the beacon signal.

  Thereby, in the communication system according to the present invention, transmission and reception of beacon signals by each wireless communication station can be dispersed as much as possible, and the time until the next beacon signal can be maximized. Therefore, in the communication system according to the present invention, it is possible to divide the communication time fairly for each wireless communication station, and to allocate a communication channel with the largest communication capacity.

  Further, each of the plurality of wireless communication stations transmits time information related to transmission / reception times of beacon signals of other wireless communication stations on a communication channel scheduled to be transmitted, and beacon signals on other communication channels of a transmission destination wireless communication station. Based on the time information related to the transmission / reception time, the maximum transmission possible time, which is the maximum time during which data can be transmitted, is grasped, and then data transmission is attempted.

  Thereby, in the communication system according to the present invention, the idle time of the communication channel scheduled to be transmitted can be properly grasped, and transmission can be attempted until the idle time. It becomes possible.

  Furthermore, each of the plurality of wireless communication stations uses a preamble provided in a packet to be transmitted / received in common with a preamble used in another system, detects that a packet of the other system is generated due to an error in information after the preamble, The communication channel used is changed based on the frequency of occurrence of packets in other systems.

  Thereby, in the communication system according to the present invention, it is possible to detect interference from other systems, and to avoid other communication channels with less interference. As a result, data collisions are reduced and throughput can be improved.

  In addition, each of the plurality of radio communication stations records the frequency of occurrence of packets of other systems as well as the reception time on each communication channel, and if the reception time exceeds a predetermined time, the error at that time The number is updated as a valid value used for determining the change of the communication channel.

  Thereby, in the communication system according to the present invention, it becomes possible to compare the interference status of other systems fairly between communication channels. Moreover, in the communication system according to the present invention, since the material used for determining the change of the communication channel is continuously updated, it is possible to appropriately consider the change in the interference state.

  Furthermore, when a wireless communication station that receives data detects interference, the transmission time and use of the beacon signal are transmitted to the wireless communication station that transmits data using the communication channel in which the interference occurs. Request change of communication channel.

  As described above, in the communication system according to the present invention, by detecting interference on the receiving side, it is possible to avoid the use of a communication channel having a bad reception condition and appropriately change to a better communication channel.

  Furthermore, when the wireless communication station that transmits data detects interference, the wireless communication station measures the number of times there is no response from the wireless communication station that receives data, and when the frequency exceeds a predetermined value, Change the signal transmission time and the communication channel to be used.

  Thus, in the communication system according to the present invention, by detecting interference on the transmission side, it is possible to recognize the deterioration of the reception status of the transmission destination on the transmission side, and voluntarily set the communication channel at its own discretion. It can be changed appropriately.

The second aspect of the present invention is a communication method in which a plurality of communication stations each operate in an autonomous distributed control manner and form a network using a plurality of communication channels,
Each communication station manages at least time information related to the transmission / reception time of the beacon signal and communication channel information related to the communication channel to be used,
Transmitting communication station attempting to transmit the beacon signals or data, switches the communication channel to use based on the time information and the communication channel information, and transmission of a beacon signal or data,
A receiving communication station trying to receive a beacon signal or data switches a communication channel to be used based on the time information and the communication channel information, and receives a beacon signal or data.
This is a communication method characterized by the above.

  In such a communication method according to the present invention, communication can be performed in a distributed manner over a plurality of communication channels, so that an increase in communication capacity can be expected and communication can be performed according to the interference situation for each communication channel. It is possible to switch channels. Further, in the communication method according to the present invention, it is possible to easily form a network by autonomous distributed control while using a plurality of communication channels, and it is possible to realize cost reduction.

According to a third aspect of the present invention, there is provided a communication apparatus that performs network operation autonomously and distributedly in a communication environment in which a plurality of communication channels are prepared.
A communication means for transmitting and receiving wireless data over a communication channel;
Communication control means for setting a communication channel to be used and controlling data transmission / reception in the communication means;
Beacon generating means for generating a beacon signal;
Beacon analysis means for analyzing beacon signals received from peripheral stations,
The communication control means includes
Manage at least time information related to the transmission / reception time of the beacon signal and communication channel information related to the communication channel used,
When transmitting a beacon signal or data, switch the communication channel to be used based on the time information and the communication channel information, try to transmit a beacon signal or data,
Upon reception of a beacon signal or data, the communication channel to be used is switched based on the time information and the communication channel information, and a beacon signal or data is received.
It is a communication apparatus characterized by this.

  When such a communication device according to the present invention attempts to transmit data, the communication device uses the communication channel to be used based on the time information regarding the transmission / reception time of the beacon signal and the communication channel information regarding the communication channel to be used. By switching and transmitting a beacon signal and attempting communication, even if a beacon signal is transmitted, it does not collide with other beacon signals. Therefore, in the system to which the communication apparatus according to the present invention is applied, even when the carrier control access control method is used, a situation is established in which a plurality of spatially overlapping communication channels are used simultaneously. It becomes possible to increase the communication capacity that can be used substantially. Further, the communication apparatus according to the present invention can easily form a network by autonomous distributed control while using a plurality of communication channels, and can construct a system that realizes cost reduction.

Further, the fourth aspect of the present invention is described in a computer-readable format so that processing for performing autonomous distributed network operation in a communication environment in which a plurality of communication channels are prepared is executed on a computer system. Computer program,
A beacon generating step for generating a beacon signal;
A beacon analysis step for analyzing a beacon signal received from a peripheral station;
Managing at least time information related to transmission / reception times of beacon signals and communication channel information related to communication channels to be used;
At the time of transmitting a beacon signal or data, switching a communication channel to be used based on the time information and the communication channel information, and attempting to transmit a beacon signal or data;
When receiving a beacon signal or data, switching a communication channel to be used based on the time information and the communication channel information, and receiving a beacon signal or data;
A computer program characterized by comprising:

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

According to the present invention, each terminal that operates as an autonomous distributed control and forms a wireless network having a plurality of communication channels has time information related to transmission / reception times of beacon signals and communication channel information related to communication channels to be used. Based on this information, beacon signals are periodically transmitted at predetermined time intervals, so that access control based on carrier sense can be performed simultaneously, and a plurality of communication channels can be used at the same time. Therefore, it is possible to construct a wireless network that can greatly increase the communication capacity and perform communication while avoiding a communication channel with interference.

  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, specific embodiments to which the present invention is applied will be described in detail with reference to the drawings.

  In the network according to this embodiment, there is no access point (AP), and a plurality of terminals (Stations) as wireless communication stations operate in an autonomous distributed manner to form a wireless network. It operates in the mode and periodically transmits beacon signals at predetermined time intervals. In this communication system, it is possible to use a plurality of communication channels at the same time while using a so-called CSMA (Carrier Sense Multiple Access) method for performing access control by carrier sense. Each communication station has at least time information related to the transmission / reception time of the beacon signal and communication channel information related to the communication channel to be used, and when trying to transmit data, the communication channel to be used is determined based on these information. Switch and try to communicate by sending a beacon signal.

FIG. 1 schematically shows a configuration of a wireless communication apparatus that performs terminal operation in the communication system according to the present embodiment. As shown in FIG. 1, as a communication means, each terminal has an antenna 11 connected to a transmission processing unit 14 and a reception processing unit 13 via a duplexer 12, and a transmission processing unit 14 and a reception processing unit 13 are connected to each terminal. It is configured to be connected to the baseband unit 15.

The transmission processing unit 14 performs various processes such as A / D conversion and modulation on the baseband signal supplied from the baseband unit 15, and further converts the RF signal into, for example, an RF (Radio Frequency) signal. Supply to the duplexer 12. As a transmission processing method in the transmission processing unit 14 , various methods suitable for relatively short distance communication applicable to a wireless LAN can be applied. Specifically, a so-called UWB (Ultra Wideband) method is applicable. An Orthogonal Frequency Division Multiplexing (OFDM) scheme, a Code Division Multiple Access (CDMA) scheme, or the like can be applied. On the other hand, the reception processing unit 13 converts the received signal into an RF signal, and further supplies a baseband signal obtained by performing various processes such as D / A conversion and demodulation to the baseband unit 15 that is a control means. To do.

  The baseband unit 15 includes an interface unit 16, a media access control (Media Access Control: MAC) unit 17, a data link control (Data Link Control: DLC) unit 18, and the like, for example, creates a beacon signal. As described above, processing in each layer in the media access control system implemented in this communication system is executed. At this time, the baseband unit 15 holds at least time information related to the transmission / reception time of the beacon signal and communication channel information related to the communication channel to be used, and switches the communication channel to be used based on the time information and the communication channel information. .

  Packets transmitted and received in a communication system in which a network is formed by such terminals have a format as shown in FIG. 2, for example. As shown in the figure, a packet is composed of a preamble, a heading area, and a payload part.

The preamble is provided at the head of the packet and is composed of a unique word. This preamble is provided for the purpose of informing the existence of the packet.

  The heading area is provided immediately after the preamble, and describes information indicating the payload part transmission rate when the physical layer is in the multi-transmission rate mode in addition to information indicating the attribute, data length, and transmission power of the packet. . When this heading area is transmitted, the transmission rate is lowered so that the required SNR (Signal to Noise Ratio) is about several dB lower than the payload part. This heading area is different from a so-called MAC header stored in the payload portion.

  The payload portion is described as PSDU (PHY Service Data Unit) in the figure, and is provided immediately after the heading area. This payload portion describes substantial information to be transmitted by the packet, such as a control signal and data. This payload part is composed of a MAC header and an MSDU (MAC Service Data Unit), and a data string passed from an upper layer to the MSDU is described.

  Now, the beacon signal transmitted / received between the terminals is stored in the payload portion, and the fact that the packet is a beacon signal is described in the heading area. FIG. 3 shows a format example of the beacon signal. The beacon signal shown in the figure has at least the MAC address (TX.ADDR) field describing the MAC address of the terminal that transmits the packet and the transmission timing of the beacon signal for the purpose of avoiding continuous collision of the beacon signal. An offset indicator (TOTT) field that describes an offset value when intentionally shifting from the target beacon transmission time (TBTT), and neighboring beacon offset information (Neighboring Beacon Information: NTT). Traffic indication map (TIM) field and page Paging (PAGE) field, and other fields (ETC) are also provided.

  In the NBOI field, as will be described in detail later, information indicating the position (reception time) of the beacon signal that can be received by the terminal transmitting the beacon signal as a relative position from the position of the beacon signal of the terminal, and the communication channel Frequency information is described.

  Also, in the TIM field, broadcast information indicating which communication station the terminal that transmits the beacon signal currently holds is described. A terminal that should receive data can recognize that it is necessary to perform reception by referring to this TIM.

  Further, in the paging field, among the receiving terminals described in the TIM, a receiving terminal that is scheduled to transmit data in a priority period described later is described. The terminal specified in this paging field can be prepared for reception in the priority period.

  In the communication system according to the present embodiment, beacon signals stored in such packets are transmitted and received between the terminals.

  Here, for example, as shown in FIG. 4, each terminal is assigned a priority period (transmission guaranteed period: TGP) in which communication can be performed preferentially at a predetermined time after transmitting a beacon signal. It is done. As shown in the figure, the priority period is not limited to the one that starts immediately after the transmission of the beacon signal. For example, the priority period starts at the relative position (time) from the transmission time of the beacon signal. It may be set, and the start time of the priority period may be set by the time from TBTT.

  Thereby, in the communication system, for example, as shown in FIG. 5, beacon signals are sequentially transmitted from a plurality of terminals, and a priority period TGP is assigned. In the example shown in the figure, a period other than the priority period is defined as FAP (Fairly Access Period). That is, when there are three terminals STA0, STA1, and STA2 in the communication system, when the terminal STA0 transmits a beacon signal, the priority period TGP0 is assigned to the terminal STA0, and the time assigned as TGP0 has elapsed. Until the next terminal STA1 transmits a beacon signal, the period FAP0 is reached. Similarly, when the period FAP0 elapses, the terminal STA1 transmits a beacon signal, the priority period TGP1 is assigned to the terminal STA1, and when the time allocated as TGP1 elapses, the next terminal STA2 transmits a beacon signal. The period FAP1. Then, when the period FAP1 elapses, the terminal STA2 transmits a beacon signal, the priority period TGP2 is allocated to the terminal STA2, and when the time allocated as TGP2 elapses, the period FAP2 is transmitted until the terminal STA0 transmits a beacon signal. It becomes.

  In the communication system according to the present embodiment, each terminal sets the transmission time of the beacon signal at a relative time in a long period from when the terminal transmits a beacon signal to when the terminal transmits the next beacon signal. To grasp. And each terminal will transmit a beacon signal with respect to another terminal when the time which can be transmitted comes.

  In the beacon signal used for such a purpose, as described above, the NBOI field describes the relative time information regarding the transmission / reception time of the beacon signal and the communication channel information regarding the communication channel used by the terminal. Yes. A terminal that newly enters the network (hereinafter referred to as a new entry terminal) receives beacon signals for one or more cycles from each peripheral channel for each communication channel, and refers to the NBOI field of each beacon signal, for example. As shown in FIG. 6A, the relative time information regarding the transmission / reception time of a receivable beacon signal and the communication channel information of the communication channel to which the beacon signal is transmitted are grasped. FIG. 6A shows a case where there are four communication channels CH1 to CH4, the portion indicated by “B” indicates the relative time when the beacon signal is received, and the portion indicated by “0”. Indicates a period FAP other than the priority period shown in FIG. Therefore, in FIG. 6, the communication channel CH1 receives a beacon signal at the seventh time, the communication channel CH2 receives the beacon signal at the first time and the fifth time, and the communication channel CH3 receives the beacon signal at the third time. This indicates that the beacon signal is received at the sixth time on the communication channel CH4.

  When each terminal newly enters the network, it holds the information as shown in FIG. 6B, for example, as information described in the NBOI field by taking the logical sum of the information grasped about the plurality of communication channels. To do. That is, the new entry terminal that grasps the relative time information for each communication channel shown in FIG. 6A takes the logical sum of the relative time information, and as shown in FIG. A beacon signal is transmitted / received using the communication channel CH2, a beacon signal is transmitted / received using the communication channel CH3 at the third time, a beacon signal is transmitted / received using the communication channel CH2 at the fifth time, and a communication channel is transmitted at the sixth time. The beacon signal is transmitted and received using CH4, and information indicating that the beacon signal is transmitted and received using communication channel CH1 is held at the seventh time.

  Then, the new entry terminal determines the transmission time of the beacon signal transmitted by itself and the communication channel to be used. In other words, the received beacon signal describes the relative time information related to the transmission / reception time of the beacon signal known by the terminal that transmitted the beacon signal and the communication channel information related to the communication channel to be used. Based on these pieces of information, the terminal determines the transmission time of the beacon signal transmitted by itself and the communication channel to be used, and updates the information as shown in FIG.

  Specifically, the new entry terminal determines the transmission time of the beacon signal transmitted by itself and the frequency of the communication channel to be used through a series of steps as shown in FIG.

  First, as shown in the figure, a new entry terminal receives and transmits a beacon signal from the adjacent node, that is, a neighboring other terminal, in step S1, thereby transmitting and receiving a beacon signal recognized by the other terminal. The relative time information and the communication channel information related to the communication channel to be used are all overlapped and ORed to create peripheral station use time zone information related to the time zone already used by other communication stations. Here, for convenience of explanation, as shown in FIG. 8A, a new entry terminal transmits and receives a beacon signal using the communication channel CH2 at the first time, and uses the communication channel CH3 at the third time. A beacon signal is transmitted / received, and at the fifth time, a beacon signal is transmitted / received using the communication channel CH2, and at the sixth time, peripheral station use time zone information indicating that a beacon signal is transmitted / received using the communication channel CH1 is created. Shall.

Subsequently, in step S2, the new entry terminal selects a position (relative time) at which the interval at which the beacon signal is transmitted and received is the maximum based on the created peripheral station use time zone information. As a result of taking the logical sum of the information about all the communication channels, if the beacon signal is not transmitted / received, it does not collide with other beacon signals even if the beacon signal is transmitted. Since it is desirable to distribute the transmission and reception of beacon signals as much as possible, the time until the next beacon signal can be maximized and the communication time can be divided fairly by selecting the position with the maximum interval. It is based on the idea that it can be done. Specifically, in the case of the peripheral station usage time zone information shown in FIG. 8A, the new entry terminal has the maximum interval for transmitting and receiving beacon signals from the seventh time to the eighth time. Therefore, the eighth time is selected as shown by the middle thick line in FIG.

Subsequently, new entrants terminal, in step S3, by dividing the peripheral stations use time period information by ORing all communication channels created in step S1 to the peripheral stations use time zone information for each communication channel, select The beacon signal transmission time is evaluated for each communication channel. Then, in step S4, the new entry terminal determines whether or not all communication channels have been evaluated.

  Here, the new entry terminal repeats the process from step S3, when evaluation about all the communication channels is not performed. On the other hand, when all the communication channels have been evaluated, the process proceeds to step S5, and based on the evaluation result, the communication channel with the maximum interval for transmitting and receiving beacon signals is selected, and a series of End the process.

Specifically, the new entry terminal divides the peripheral station use time zone information shown in FIG. 8A for each communication channel, and as shown in FIG. A beacon signal is transmitted / received, a beacon signal is transmitted / received at the first and fifth times on the communication channel CH2, a beacon signal is transmitted / received at the third time on the communication channel CH3, and a beacon signal is not transmitted / received on the communication channel CH4. Peripheral station use time zone information consisting of four logical sums is created. Then, as a result of the evaluation for each communication channel, the new entry terminal indicates that the interval of the communication channel CH4 is the maximum at the 8th time selected in step S2, so that it is indicated by a thick line portion in FIG. Then, the communication channel CH4 is selected.

  The new entry terminal can determine the optimal transmission time of the beacon signal and the frequency of the communication channel to be used through such a series of steps.

  Next, in the communication system, when a communication station is allowed to perform reserved communication, an operation for performing communication by reserving a communication time zone and a communication channel will be described. In the communication by reservation, signal collision can be suppressed in the multi-hop link as shown in FIG. 9, and the effect of increasing the communication capacity can be expected.

In a multi-hop link, there are hidden terminals that do not know each other in the communication station. In the example shown in FIG. 9, for example, Sta1 and Sta3 are in a hidden terminal relationship. However, when STA1 reserves a communication time zone and a communication channel for communication with STA2, it is necessary to consider so that it does not overlap with the transmission time zone and channel of STA3, which is a hidden terminal and cannot communicate. Therefore, the NBOI is used here in the same manner as the determination and notification of the beacon signal transmission / reception time.

In such a case, each terminal describes not only the beacon transmission / reception time but also the reserved time zone and communication channel in the NBOI and broadcasts it with a beacon. When a communication channel is reserved, a free time zone is searched from the NBOI information of the adjacent terminal, and the reserved time is written in the NBOI.

An operation procedure when the communication station performs reservation communication will be specifically described. Here, consider a case in which Sta1 makes a reservation for transmission to Sta2 in FIG.

Sta1 receives beacon signals from adjacent terminals a, b, and c, and superimposes the NBOIs obtained from the signals for each channel. As a result, the result of the second-stage adjacent reservation information shown in FIG. 10 can be obtained. This is information on a free time zone in each communication channel of Sta1.

Furthermore, as a result of superimposing the NBOI of Sta2 as the transmission destination by the reserved communication on this result, the result shown in the lowermost stage of FIG. 10 can be obtained. This shows the information of the free time zone in which communication reservation from Sta1 to Sta2 is possible for each communication channel. Based on this result, Sta1 selects a time zone and a communication channel in which a reservation of a desired length can be secured. In the example shown in the figure, if it is desired to secure a time slot that is continuous for two slots, only CH3 is applicable, so the last two slots of CH3 are set as the communication reservation time zone from Sta1 to Sta2. As a reference for selecting a reservation communication channel, it is also possible to consider interference information for each channel. And Sta1 describes in the NBOI which alert | reports the information regarding reservation communication in a beacon.

With the above operation, Sta1 can know the reservation information of Sta3 of the hidden terminal by using the NBOI of Sta2, and in the time zone and communication channel that do not overlap even in the autonomous distributed wireless communication system, It is possible to make a communication reservation with Sta2.

  FIG. 11 is a flowchart showing a series of steps when a new entry terminal determines a transmission time of a beacon signal transmitted by itself and a communication channel to be used when a communication station is allowed to perform reservation communication. It is shown in the form of

  First, the communication station superimposes the communication scheduled time zone information of beacons received from adjacent terminals for each channel (step S11). As a result, information on the free time zone in each communication channel is obtained.

  Further, the scheduled communication time zone information in all communication channels of the communication reservation partner terminal is superimposed on the above-mentioned idle time zone information for each channel (step S12). As a result, it is possible to obtain, for each communication channel, information on a free time zone in which a communication reservation with a communication reservation partner terminal can be made.

  Then, the time zone in which the empty slot interval is maximized and the communication channel are selected as the time zone and communication channel for performing reservation communication with the communication reservation partner terminal (step S13).

  By determining the reservation communication time zone and communication channel for the communication reservation partner terminal by such a procedure, the communication station makes a communication reservation in a time zone and communication channel that do not overlap even in an autonomous distributed wireless communication system. Is possible.

  Next, the operation in which the communication station transmits / receives data between the terminals that have determined the relative time for transmitting the beacon signal of the local station and the communication channel to be used will be described.

  Each terminal knows the relative time at which the other terminal transmits the beacon signal and the frequency of the communication channel. Therefore, when that time comes, the terminal switches the communication channel and receives the transmitted beacon signal. In the communication system, as shown in FIG. 4 and FIG. 5 above, since the predetermined time after the transmission of the beacon signal is the priority period, the preferential data between the terminals designated by the beacon signal is transmitted. Transmission and reception are possible.

  In a communication system, basically, each terminal starts access by following a procedure compliant with the CSMA method. However, a terminal to which a priority period is assigned (hereinafter referred to as a priority terminal) performs carrier sense. The priority is given to the priority terminal by shortening (IFS: Inter Frame Space). On the other hand, the terminal that has not been given priority attempts to access the terminal that transmitted the beacon signal by using the carrier sense over the normal time IFS.

  In a communication system, a terminal that cannot receive a beacon signal of a communication channel used by a priority terminal at the same time, or a terminal that does not intentionally receive a beacon signal because there is no need for access, Communication using carrier sense over the normal time IFS can be performed. That is, for other communication channels different from the communication channel used by the priority terminal, a terminal having a low priority can be used by using a normal carrier sense over a long time. As a result, it is possible to construct a situation in which a plurality of spatially overlapping communication channels are used simultaneously.

  In the communication system, each terminal needs to confirm that other terminals are not receiving the beacon signal at the time of transmission and the frequency of the communication channel to be used. Therefore, each terminal grasps the time at which transmission / reception of the beacon signal is scheduled, using only the information of the communication channel for transmission based on the transmission / reception time information and communication channel information of the beacon signal held by the other terminals. . Furthermore, each terminal grasps the time at which the frequency of the communication channel used by the destination terminal is switched based on the transmission / reception time information of the beacon signal of the destination terminal. Thereby, each terminal can try transmission until the free time obtained as a result.

  In order to specifically explain such an operation, as shown in FIG. 12, consider a situation in which there are four terminals STA1, STA2, STA3, and STA4 configured to reach radio waves to terminals adjacent to each other. . That is, terminal STA1 can transmit / receive data to / from terminals STA2 and STA3, terminal STA2 can transmit / receive data to / from terminal STA1, and terminal STA3 transmits / receives data to / from terminals STA1 and STA4. The terminal STA4 can transmit / receive data to / from the terminal STA3.

Under such circumstances, as shown in FIG. 13, at time T1, the terminal STA2 transmits data to the terminal STA1 using the communication channel CH1, and the terminal STA1 receives the data. at time T2, transmits the data to the terminal STA4 terminal STA3 is using the communication channel CH 2, consider a situation as to receive the terminal STA4 this. In the figure, the portion indicated by “B” indicates the time when the beacon signal is transmitted and received, and among these, the beacon signal indicated by the hatched portion indicates the transmitting side. Furthermore, in the figure, the part indicated by “Tx” indicates that data is being transmitted, and the part indicated by “Rx” indicates that data is being received.

  Further, each terminal is assumed to grasp information as shown in FIG. 14 as the transmission / reception time information and communication channel information of the beacon signal. That is, terminal STA2 uses communication channel CH1 at time T1, as shown in FIG. 5A, and terminal STA1 uses communication channel CH1 at time T1, as shown in FIG. At time T2, the channel is switched to the communication channel CH2. Terminal STA3 uses communication channel CH2 at time T2, and terminal STA4 uses communication channel CH2 at time T2.

  Here, attention is focused on the terminal STA2. When the terminal STA2 retains the information shown in FIG. 5A as the transmission / reception time information and communication channel information of the beacon signal related to itself, the terminal STA2 will continue to transmit data, and wastes the bandwidth. It will end up.

  Therefore, the terminal STA2 takes out the information of the communication channel used by itself from the time information and communication channel information of the beacon signal related to the other terminal acquired at the time of new entry into the network, and performs a logical sum, and further, the destination terminal The logical sum is also taken for the time information on the other communication channels of STA1. Thereby, terminal STA2 can obtain information as shown in FIG. That is, terminal STA2 can avoid a situation in which data transmission to terminal STA1 is unnecessarily continued by grasping that terminal STA1 switches the communication channel from CH1 to CH2 at time T2.

  Similarly, paying attention to the terminal STA3, the terminal STA3 can obtain information as shown in FIG. 5B by using information on the terminals STA1 and STA4. In the period from time T1 to time T2, It can be understood that communication may be performed with the terminal STA4 using the communication channel CH2.

  As described above, in the communication system, each terminal transmits and receives the beacon signal transmission / reception time information of the peripheral terminal on the communication channel scheduled to be transmitted and the beacon signal transmission / reception time information on the other communication channel of the transmission destination terminal. Based on this, by grasping the time at which the frequency of the communication channel used by the destination terminal is switched, it grasps the maximum transmittable time, which is the maximum time during which data can be transmitted, and then attempts to transmit data . Thereby, each terminal can try transmission until the obtained free time, and can use the communication channel to the maximum.

  Finally, a countermeasure for avoiding an interference channel in a communication system that transmits and receives such data will be described.

  In a communication system, when there are many errors, or when the signal cannot be demodulated but the received signal level is high, the communication channel used at that time is considered to be interfered and used by its own terminal and other terminals. Change the frequency of the communication channel.

  Here, in the communication system, the presence of another system using the same frequency band is detected as follows.

  As described above with reference to FIG. 2 and FIG. 3, a preamble is provided at the head of a packet transmitted / received in a wireless LAN such as the IEEE 802.11 system. In the present embodiment, the preamble used in the own system is shared with the preamble used in other systems. In this case, if the information after the preamble is incorrect although the occurrence of the packet can be detected by the preamble, each terminal determines that the information is a packet of another system. be able to.

  In this way, each terminal measures the number of packet occurrences of other systems and detects the frequency.

  In addition, since the reception time in each communication channel is not uniform, each terminal, for example, as shown in FIG. 16, receives the reception time (standby in each communication channel) together with the packet generation count (data error count) of other systems. Time) is also recorded. Then, when the reception time exceeds a predetermined time, each terminal uses the number of data errors at that time as an effective value used for determining the change of the communication channel. In the figure, the number of valid data errors is set when the standby time is "100".

  More specifically, each terminal detects the presence of another system based on the number of data errors and the reception time through a series of steps shown in FIG.

  First, as shown in the figure, each terminal counts the number of data errors and the reception time in each communication channel in step S21, and determines in step S22 whether or not it has been received for a predetermined time.

  Here, if each terminal determines that it has not received for a predetermined time, it repeats the processing from step S21. On the other hand, if it is determined that the data has been received for a predetermined time, the number of data errors in the corresponding communication channel is updated and recorded as an effective value in step S23.

  In step S24, each terminal resets a counter that records the number of data errors and the reception time in the corresponding communication channel, and repeats the processing from step S21 again.

  Through such a series of steps, each terminal can compare the number of data errors and the reception time at the same measurement time and update at regular intervals to detect the presence of other systems. be able to.

  When each terminal determines that some kind of interference, including interference from other systems detected, is large, the terminal changes the communication channel being used.

  Here, when interference is detected on the receiving side, the receiving terminal changes the communication channel to the transmitting terminal that transmits data using the communication channel in which the interference occurs. Send a request message to Then, when receiving the request message, the transmitting terminal stops using the current transmission time of the beacon signal and the communication channel, and performs the procedure at the time of new entry into the network similar to that already described with reference to FIG. By stepping on, the transmission time of the beacon signal is changed to another communication channel.

  Specifically, in the communication system, the transmission time of the beacon signal and the communication channel to be used are changed by cooperatively performing a series of steps as shown in FIG. 18 between the reception terminal and the transmission terminal.

  First, as shown in the figure, the receiving terminal determines whether or not interference has occurred by determining whether or not the number of data errors exceeds a predetermined threshold in step S31.

  Here, if it is determined that no interference has occurred, the receiving terminal continues the measurement. On the other hand, if it is determined that interference has occurred, the request message described above is transmitted to the transmitting terminal.

  In response to this, when receiving the request message, the transmitting terminal selects a free transmission time and a communication channel capable of transmitting the beacon signal in step S32. This processing may be performed according to the processing procedure shown in FIG.

  Subsequently, the transmitting terminal determines whether or not the selected communication channel is the same communication channel as the currently used communication channel in step S33.

  Here, if the transmitting terminal determines that the selected communication channel is not the same communication channel, the transmitting terminal changes the beacon signal transmission time and the communication channel to be used, and changes until there is a request message from the receiving terminal. The communication using the transmitted time and communication channel is continued.

  On the other hand, if the transmitting terminal determines that the selected communication channel is the same communication channel, in step S34 the beacon signal at the selected transmission time is excluded and the beacon signal transmission time and the communication to be used are excluded. Without changing the channel, the process proceeds to step S32 again to select a new transmission time and communication channel.

  In the communication system, when the receiving terminal detects interference, the transmission time of the beacon signal and the communication channel to be used are changed by performing such a series of steps between the receiving terminal and the transmitting terminal. Interference can be avoided.

  In a communication system, it is conceivable to detect interference on the transmission side separately from such a method. In this case, the transmitting terminal changes the communication channel based on the presence / absence of a response from the receiving terminal.

  In a wireless LAN such as the IEEE 802.11 system, there is a control using a so-called RTS (Request To Send) signal and a CTS (Clear To Send) signal in order to solve the so-called hidden terminal problem, and data reception is also performed. The received terminal returns an ACK (Acknowledgement) signal. That is, in a wireless LAN such as the IEEE 802.11 system, there is a response using a CTS signal or an ACK signal in response to transmission of an RTS signal or data.

  However, in wireless LANs such as the IEEE802.11 scheme, when there is interference in the communication channel to be used and the communication quality is poor, a situation occurs in which these responses do not reach the transmission side.

  Therefore, the transmitting terminal measures the number of times such a response is not received and detects the frequency. Then, when the frequency exceeds a predetermined value, the transmitting terminal performs the procedure for transmitting the beacon signal and using it by following the same procedure for new entry into the network as already described with reference to FIG. Change the communication channel.

  As described above, even when the transmission terminal detects interference, the transmission time of the beacon signal and the communication channel to be used can be changed to avoid the interference.

  As described above, in the communication system shown as the embodiment of the present invention, when a plurality of terminals operate in an autonomous distributed control manner, each terminal uses a communication channel to be used with time information related to transmission / reception times of beacon signals. The communication channel information is stored and the beacon signal is periodically transmitted at a predetermined time interval based on the information, so that multiple communication channels can be used simultaneously while performing access control by carrier sense. Therefore, it is possible to easily construct a network that can greatly increase the communication capacity at low cost.

  At this time, the beacon signal describes time information and frequency information known by the terminal that transmits the beacon signal. Then, based on the time information and frequency information described in the beacon signal received from the other terminal, the new entry terminal grasps the time information of the receivable beacon signal and the communication channel through which the beacon signal is transmitted. Therefore, it is possible to appropriately grasp the status of other terminals.

  In this communication system, a new entry terminal determines the transmission time of the beacon signal transmitted by itself and the frequency of the communication channel to be used based on the grasped time information and communication channel information. Can avoid a situation in which the beacon signal is transmitted at the time when the beacon signal is received and the communication channel.

Further, in this communication system, a new beaconing terminal generates a beacon signal based on peripheral station usage time zone information created by superimposing all time information and frequency information described in a beacon signal received from another terminal. the time interval that is transmitted and received is the largest, self splits with selected as the transmission time for transmitting a beacon signal, the peripheral stations use time period information created around station use time zone information for each communication channel, selected Beacon signal transmission time is evaluated for each communication channel, and each terminal transmits and receives beacon signals by selecting the communication channel with the maximum interval for transmitting and receiving beacon signals as the communication channel for transmitting beacon signals. Can be dispersed as much as possible, and the time until the next beacon signal can be maximized to each other. . Therefore, in this communication system, it is possible to divide the communication time fairly for each terminal, and to allocate a communication channel with the largest communication capacity.

  Further, in this communication system, time information related to the transmission / reception time of the beacon signal of the other terminal in the communication channel scheduled for transmission by each terminal, and time information related to the transmission / reception time of the beacon signal in the other communication channel of the destination terminal Based on the above, it is possible to grasp the free time of the communication channel that is scheduled to be transmitted because it tries to send data after grasping the maximum transmission time that is the maximum time that data can be transmitted. Therefore, it is possible to try transmission until a vacant time, and the communication channel can be used to the maximum extent.

  Furthermore, in this communication system, a preamble provided in a packet to be transmitted / received is shared with a preamble used in another system, and each terminal detects that a packet of the other system is generated due to an error in information after the preamble. By changing the communication channel used based on the frequency of occurrence of packets in other systems, it is possible to detect interference from other systems and avoid other communication channels with less interference . Therefore, in this communication system, data collision is reduced and throughput can be improved.

  Also, in this communication system, each terminal records the reception time in each communication channel together with the frequency of occurrence of packets of other systems, and when the reception time exceeds a predetermined time, By updating the number of errors as an effective value used to determine the change of the communication channel, it becomes possible to compare the interference status of other systems fairly between the communication channels, and update the material used to determine the change of the communication channel. Since it is continuously performed, it is possible to appropriately consider changes in the interference state.

  Furthermore, in this communication system, when interference is detected on the receiving side, the transmission time of the beacon signal and the transmission terminal that uses the communication channel in which the interference has occurred are transmitted to the transmitting terminal. It is possible to request a change in the communication channel, avoid using a communication channel with a poor reception condition, and appropriately change to a better communication channel.

  Furthermore, in this communication system, when interference is detected on the transmission side, the number of times of no response from the receiving terminal receiving data is measured, and when the frequency exceeds a predetermined value, a beacon signal is measured. By changing the transmission time and the communication channel to be used, it is possible to recognize the deterioration of the reception status of the transmission destination on the transmission side, and it is possible to change the communication channel appropriately on its own judgment.

  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.

In the above-described embodiment, the case where the present invention is applied to a wireless LAN similar to the IEEE 802.11 system has been described. However, the gist of the present invention is not limited to this, and wireless communication adopting an autonomous distributed control system. if the system, be any one can be applied the present invention as well.

  Further, in the present specification, in an autonomous distributed wireless network, each communication station performs access control to a medium while avoiding a collision according to detection of a transmission signal from another communication station, and reservation communication or Although the case where media access is performed by priority communication has been described as the main embodiment, the gist of the present invention is not limited to this, and the same applies to communication systems employing other media access methods. The present invention can be applied.

Further, in the present specification, the embodiment in which the present invention is applied to an autonomous distributed wireless network has been mainly described. Of course, the present invention is similarly applied to a network other than an autonomous distributed network. be able to.

  In short, the present invention has been disclosed in the form of exemplification, and the description of 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 block diagram illustrating a configuration of a terminal included in a communication system shown as an embodiment of the present invention. FIG. 2 is a diagram for explaining a format of a packet transmitted and received in the communication system. FIG. 3 is a diagram for explaining the format of a beacon signal transmitted and received in the communication system. FIG. 4 is a diagram for explaining a priority period assigned to each terminal that has transmitted a beacon signal. FIG. 5 is a diagram illustrating a state in which beacon signals are sequentially transmitted from a plurality of terminals and a priority period is assigned. FIG. 6 is a diagram for explaining the contents of the beacon signal. FIG. 6A shows the relative time information regarding the transmission / reception time of the receivable beacon signal grasped by each terminal and the communication in which the beacon signal is transmitted. An example of channel frequency information is shown, and FIG. 5B is a diagram showing an example of contents held by each terminal as information described in an NBOI field in a beacon signal. FIG. 7 is a flowchart for explaining a series of steps when a new entry terminal determines a transmission time of a beacon signal transmitted by itself and a communication channel to be used. FIG. 8 is a diagram illustrating an example of peripheral station usage time zone information created by a new entry terminal based on a beacon signal from another terminal. FIG. 8A illustrates a beacon signal that is understood by the other terminal. 1 shows an example of peripheral station use time zone information consisting of logical sum created by superimposing all the relative time information for transmitting and receiving and the frequency information of the communication channel, and FIG. Based on the peripheral station use time zone information, the position where the interval at which the beacon signal is transmitted and received is selected is shown. FIG. 10C shows the peripheral station use time zone information shown in FIG. It is a figure which shows a mode that it divided | segmented for every communication channel and selected the communication channel with the largest space | interval which a beacon signal is transmitted / received. FIG. 9 is a diagram illustrating a configuration example of a multi-hop link. FIG. 10 is a diagram for explaining an operation procedure for the communication station Sta1 to search for a time zone in which reserved communication is performed based on the NBOI described in the beacon signal received from the adjacent terminals a, b, and c. is there. FIG. 11 shows a series of steps when a new entry terminal determines a transmission time of a beacon signal transmitted by itself and a communication channel to be used when a communication station is allowed to perform reserved communication. It is a flowchart. FIG. 12 is a diagram illustrating a situation in which there are four terminals configured to allow radio waves to reach adjacent terminals as a specific example of the communication system. FIG. 13 is a timing chart for explaining how each terminal transmits and receives beacon signals and data under the situation shown in FIG. FIG. 14 is a diagram showing an example of beacon signal transmission / reception time information and communication channel frequency information known by each terminal shown in FIG. 12, and FIG. 14 (A) is understood by the terminal STA2. An example of the information is shown, FIG. 5B shows an example of the information grasped by the terminal STA1, FIG. 8C shows an example of the information grasped by the terminal STA3, and FIG. ) Is a diagram illustrating an example of information grasped by the terminal STA4. FIG. 15 shows the logical sum of the information on the communication channel used by the terminals STA2 and STA3 shown in FIG. 12 from the time information and communication channel information of the beacon signal acquired when newly entering the network. Furthermore, it is a figure which shows an example of the information obtained as a result of ORing also about the time information in the other communication channel of the terminal STA1 of the transmission destination, and the same figure (A) is obtained by the terminal STA2. An example of information is shown, and FIG. 5B is a diagram showing an example of information obtained by the terminal STA3. FIG. 16 is a diagram for explaining how each terminal records the number of packet generations (number of data errors) in other systems and the reception time in each communication channel in order to detect the presence of other systems. FIG. 17 is a flowchart for explaining a series of steps when each terminal detects the presence of another system based on the number of data errors and the reception time. FIG. 18 is a flowchart for explaining a series of steps when changing the transmission time of the beacon signal and the communication channel to be used when the reception terminal detects interference. FIG. 19 is a diagram illustrating a configuration example in the infrastructure mode of an IEEE 802.11 wireless LAN and a state in which a beacon signal is transmitted. FIG. 20 is a diagram for explaining a configuration example in an ad hoc mode of a wireless LAN of the IEEE 802.11 system and a state in which a beacon signal is transmitted. FIG. 21 is a diagram for explaining a state of a signal transmission / reception procedure between a plurality of terminals in an ad hoc mode of an IEEE 802.11 wireless LAN.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 ... Antenna 12 ... Duplexer 13 ... Reception processing part 14 ... Transmission processing part 15 ... Baseband part 16 ... Interface part 17 ... MAC part 18 ... DLC part STA0, STA1, STA2, STA3, STA4 ... Terminal

Claims (19)

A communication system in which a plurality of communication stations operate in an autonomous distributed control manner and form a network using a plurality of communication channels,
Each communication station manages at least time information related to the transmission / reception time of the beacon signal and communication channel information related to the communication channel to be used,
Transmitting communication station attempting to transmit the beacon signals or data, switches the communication channel to use based on the time information and the communication channel information, and transmission of a beacon signal or data,
A receiving communication station trying to receive a beacon signal or data switches a communication channel to be used based on the time information and the communication channel information, and receives a beacon signal or data.
A communication system characterized by the above. A communication method in which a plurality of communication stations operate in an autonomous distributed control manner and form a network using a plurality of communication channels,
Each communication station manages at least time information related to transmission / reception times of beacon signals and communication channel information related to communication channels to be used,
A transmission communication station that tries to transmit a beacon signal or data switches a communication channel to be used based on the time information and the communication channel information, transmits a beacon signal or data,
A receiving communication station trying to receive a beacon signal or data switches a communication channel to be used based on the time information and the communication channel information, and receives a beacon signal or data.
A communication method characterized by the above. The communication station is capable of reservation communication or priority communication in a communication channel to be used, and manages transmission / reception time in reservation communication or priority communication as the time information.
The communication method according to claim 2. A communication device that performs network operation autonomously and distributedly in a communication environment in which a plurality of communication channels are prepared,
A communication means for transmitting and receiving wireless data over a communication channel;
Communication control means for setting a communication channel to be used and controlling data transmission / reception in the communication means;
Beacon generating means for generating a beacon signal;
Beacon analysis means for analyzing beacon signals received from peripheral stations,
The communication control means includes
Manage at least time information related to the transmission / reception time of the beacon signal and communication channel information related to the communication channel to be used,
When transmitting a beacon signal or data, switch the communication channel to be used based on the time information and the communication channel information, try to transmit a beacon signal or data,
Upon reception of a beacon signal or data, the communication channel to be used is switched based on the time information and the communication channel information, and a beacon signal or data is received.
A communication device. Reservation communication or priority communication is possible in the communication channel used,
The communication control means manages transmission / reception time in reservation communication or priority communication as the time information.
The communication apparatus according to claim 4. The beacon generating means describes the time information and the communication channel information in a beacon signal,
The communication control means, based on the time information and the communication channel information described in the beacon signal received from another communication station, grasps the time and communication channel at which the other communication station is communicating,
The communication apparatus according to claim 4. The communication control means determines the time at which the communication device transmits a beacon signal, the time at which data communication is performed, and the communication channel to be used based on the time and communication channel at which the other communication station grasps the communication. decide,
The communication apparatus according to claim 6. When the communication control means newly enters the network,
Superimposing the time information and the communication channel information described in the beacon signal received from another communication station to create the peripheral station use time zone information related to the time zone already used in the other communication station,
Based on the use time zone information, determine the transmission time of the beacon signal of the communication device and the communication channel used for transmission of the beacon signal.
The communication apparatus according to claim 6. When the communication control unit newly enters the network, based on the peripheral station usage time zone information, the communication control means determines the time at which the interval with the beacon signal transmission / reception time at the other communication station is maximized. Determine as signal transmission time,
The communication apparatus according to claim 8. When the communication control means newly enters the network,
The peripheral station use time zone information is divided into peripheral station use time zone information for each communication channel,
Communication that evaluates the time at which the interval with the beacon signal transmission / reception time at the other communication station is maximum for each communication channel, and transmits the beacon signal of the communication device through the communication channel with the maximum interval at which the beacon signal is transmitted / received Decide as a channel,
The communication apparatus according to claim 9. The communication control means is used for the reservation communication or priority communication, and the reservation communication or priority communication based on the communication time and the communication channel of the other communication stations that have been grasped. Determine the communication channel,
The communication apparatus according to claim 6. When the communication control means tries to perform data communication with a specific communication partner,
Superimposing the time information and the communication channel information described in the beacon signal received from another communication station for each communication channel, creating peripheral station use time zone information for each communication channel,
The time information on all communication channels of the communication partner is superimposed on the peripheral station use time zone information for each communication channel, and the available time zone information relating to the time zone available for communication with the communication partner is set to the communication channel. Every time,
Based on the available time zone information for each communication channel, a communication channel used for communication with the communication partner and a time zone for performing communication are determined.
The communication device according to claim 11. The communication control means is based on time information relating to transmission / reception times of beacon signals of other communication stations and time information relating to transmission / reception times of beacon signals in other communication channels of transmission destinations in communication channels scheduled to be transmitted. Trying to send data after knowing the maximum available time, which is the maximum time that data can be sent,
The communication apparatus according to claim 6. In the communication environment, there are a plurality of communication systems, and in each communication system, each communication station transmits a packet with a preamble signal common to other communication systems,
The communication means, in each communication system, the communication station transmits a packet provided with a common preamble,
The communication control means detects that a packet from another system has occurred due to an error in the information after the preamble of the received packet, and changes the communication channel used based on the frequency of occurrence of the packet from the other system. To
The communication apparatus according to claim 4. The communication control means records the reception time of each communication channel together with the frequency of occurrence of packets from other systems, and uses the number of errors when the reception time exceeds a predetermined time to determine the change of the communication channel. Valid value
The communication device according to claim 14. When the communication control unit detects interference when receiving data, the communication control unit that transmits data using the communication channel in which the interference has occurred changes the transmission time of the beacon signal and the communication channel to be used. Request,
The communication apparatus according to claim 4. The communication control means, when detecting interference when transmitting data, measures the number of times there is no response from the data transmission destination communication station, in response to the frequency of no response exceeding a predetermined value, Request the change of the beacon signal transmission time and the communication channel to be used.
The communication apparatus according to claim 4. A communication control method for performing autonomous distributed network operation in a communication environment in which a plurality of communication channels are prepared,
A beacon generating step for generating a beacon signal;
A beacon analysis step for analyzing a beacon signal received from a peripheral station;
Managing at least time information related to transmission / reception times of beacon signals and communication channel information related to communication channels to be used;
At the time of transmitting a beacon signal or data, switching a communication channel to be used based on the time information and the communication channel information, and attempting to transmit a beacon signal or data;
When receiving a beacon signal or data, switching a communication channel to be used based on the time information and the communication channel information, and receiving a beacon signal or data;
A communication control method comprising: A computer program described in a computer-readable format so as to execute processing for performing autonomous distributed network operation on a computer in a communication environment in which a plurality of communication channels are prepared.
A beacon generation procedure for generating a beacon signal;
A beacon analysis procedure for analyzing a beacon signal received from a peripheral station;
A procedure for managing at least time information related to transmission / reception times of beacon signals and communication channel information related to communication channels to be used;
At the time of transmitting a beacon signal or data, a procedure for switching a communication channel to be used based on the time information and the communication channel information and attempting to transmit a beacon signal or data;
At the time of receiving a beacon signal or data, a procedure for switching a communication channel to be used based on the time information and the communication channel information and receiving a beacon signal or data;
A computer program for executing

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