JP2008227722A - Radio communication management unit, radio communication unit, radio network system, and carrier sense multiple access method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To increase frame transmission efficiency while achieving collision avoidance in frame transmission, when there are a small number of radio communication units belonging to a radio communication network system. <P>SOLUTION: The radio communication network system includes a radio communication management unit and radio communication units. The radio communication management unit obtains the number of radio communication units belonging to the system concerned. Each radio communication unit operates by selecting an operation mode corresponding to the number of units obtained by the radio communication management unit, among a plurality of selectable operation modes. A method for avoiding a collision and a method for controlling hidden terminals are specified in the operation mode, which can be switched. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a radio communication management device, a radio communication device, a radio network system, and a carrier sensing multiple access method, and can be applied to, for example, an ad hoc communication system to which CSMA / CA (Carrier Sense Multiple Access Collision Aidance) is applied. Is.

In a wireless network system (for example, an ad hoc communication system) using CSMA / CA, backoff control is performed to reduce the probability of frame transmission collision (see Non-Patent Document 1). In a network where a hidden terminal problem may occur, the influence of the hidden terminal problem is reduced by RTS (Request to Send) / CTS (Clear to Send) processing (see Non-Patent Document 1).
Supervised by Masahiro Morikura and Shuji Kubota, “Revised 802.11 High-Speed Wireless LAN Textbook”, published by Impress Inc., January 2005

  However, back-off control, RTS / CTS processing, and the like are based on the assumption that the number of terminals belonging to the wireless network system is unknown. Therefore, generally, even when the number of terminals is quite large, the back-off control and the RTS / CTS process have a large margin so that frame transmission collision can be avoided, and the number of terminals is relatively small. When the frame transmission request collision is small and stable, the overhead is excessive.

  The present invention has been made in view of the above points. When the number of wireless communication apparatuses belonging to a wireless network system is small, an apparatus capable of improving frame transmission efficiency while achieving collision avoidance of frame transmission, A method is desired.

  According to a first aspect of the present invention, there is provided a carrier sensing multiple access method in which a wireless communication apparatus to transmit data grasps data transmission timing based on whether or not a carrier signal is detected. Capturing the number of devices and operating each wireless communication device by selecting an operation mode according to the number of wireless communication devices captured by the wireless communication management device from a plurality of selectable operation modes. Features.

  According to a second aspect of the present invention, there is provided a wireless communication management device comprising: a device number grasping means for capturing the number of wireless communication devices belonging to a wireless network system to which a carrier sensing multiple access method is applied; An operation mode instructing unit that directly or indirectly instructs each wireless communication device belonging to the wireless network system from among the operation modes.

  A wireless communication apparatus according to a third aspect of the present invention is a mode instruction for recognizing an operation mode directly or indirectly instructed from a wireless communication management apparatus of a wireless network system to which the carrier sensing multiple access method belongs. It has a receiving means and an operation mode switching means for executing an operation in an instructed operation mode among a plurality of operation modes.

  A wireless network system according to a fourth aspect of the present invention includes the wireless communication management apparatus according to the second aspect of the present invention and a plurality of wireless communication apparatuses according to the third aspect of the present invention.

  According to the present invention, since the operation mode is switched according to the number of wireless communication devices, when the number of wireless communication devices belonging to the wireless network system is small, frame transmission efficiency is improved while achieving frame transmission collision avoidance. Will be able to.

(A) First Embodiment Hereinafter, a first embodiment of a wireless communication management device, a wireless communication device, a wireless network system, and a carrier sensing multiple access method according to the present invention will be described with reference to the drawings.

(A-1) Configuration of First Embodiment FIG. 2 is a block diagram illustrating a schematic configuration of a wireless network system according to the first embodiment. 2, a wireless network system 1 according to the first embodiment includes a wireless communication management device (NC; Network Coordinator) 2 and one or a plurality of wireless communication devices (FIG. 2 shows three cases). DEV: Device) 3-1 to 3-3. The wireless communication management device 2 is a communication terminal for managing a network, and also performs communication as a normal communication terminal, may be fixedly installed, and is movable. May be. The wireless communication devices 3-1 to 3-3 are ordinary communication terminals, which may be fixedly installed or may be movable. The number of wireless communication devices belonging to the wireless network system 1 increases or decreases depending on the entry or withdrawal of the wireless communication device.

  Note that, when the wireless communication management device 2 is operated as a communication terminal, the description will be made using “3-0” instead of “2” as a code.

  FIG. 1 is a block diagram showing a functional schematic configuration of the wireless communication management device 2. The wireless communication management device 2 includes a transmission / reception shared antenna 21, a transmission unit 22, a reception unit 23, a management communication control unit 24, a management storage unit 25, a communication control unit 26, and a storage unit 27.

  The transmission / reception shared antenna 21 exchanges radio signals with a radio space. The form of the antenna is not limited, and the transmitting antenna and the receiving antenna may be separated. Moreover, regarding the reception, diversity processing may be applied.

  The transmission unit 22 digitally modulates a transmission frame (for example, a beacon frame described later) provided from the management communication control unit 24 or the communication control unit 26 (the digital modulation method is not limited), The antenna is radiated from the shared antenna 21 to the radio space. The transmitter 22 appropriately includes a filter, a power amplifier, and the like that limit the band of the radio signal.

  The receiving unit 23 digitally demodulates a radio signal captured by the shared antenna 21 and converted into an electric signal, and gives the obtained frame to the management communication control unit 24 and the communication control unit 26. The receiving unit 23 appropriately includes an amplifier that amplifies the received radio signal, a filter that removes out-of-band noise, and the like.

  The management communication control unit 24 and the communication control unit 26, for example, realize a predetermined function by the same CPU executing a predetermined program. Functionally, as shown in FIG. The management communication control unit 24 and the communication control unit 26 can be divided. Similarly, even if the management storage unit 25 and the storage unit 27 are used by sharing all or a part of the storage medium (semiconductor memory, hard disk, etc.), as shown in FIG. The management storage unit 25 and the storage unit 27 can be divided.

  The management communication control unit 24 executes communication control when the wireless communication management device 2 communicates as a communication terminal that manages a network. Programs, data, and the like are stored in the management storage unit 25. ing. For example, a program P25 for executing processing shown in the flowchart of FIG. 5 to be described later and beacon frame configuration data shown in FIG. 6 are stored in the management storage unit 25. The management communication control unit 24 includes a hard timer or a soft timer.

  The communication control unit 26 performs communication control when the wireless communication management device 2 communicates as a general communication terminal 3-0 of the network, and programs, data, and the like for this are stored in the storage unit 27. ing. For example, the program P27 for executing the processing shown in the flowchart of FIG. 7 described later and the data of the operation mode correspondence table TBL shown in FIG.

  As shown in FIG. 3, one record of the operation mode correspondence table TBL includes the number or range of the wireless communication devices (communication terminals) 3 belonging to the wireless network system 1 and the operation mode identification code (in the first embodiment, May be omitted), and includes information such as an identification code for the collision avoidance method and an identification code for the collision avoidance method. For example, in the record in the first row, when the number of terminals is 2, the operation mode is “1”, the method of the identification code “C1” is applied as the collision avoidance method, and the identification code “C1” is used as the hidden terminal control method. It is described that the method of “H1” is applied.

  Here, the storage unit 27 also stores programs and data for realizing the collision avoidance methods for the identification codes C1 to C3, respectively, and for realizing the hidden terminal control method for the identification codes H1 to H3, respectively. Programs and data are also stored. In other words, the execution of the hidden terminal control method by the CPU means that there is a hidden terminal control means, and the execution of the collision avoidance method by the CPU means that the collision avoidance means exists. Represents.

  As a collision avoidance method, for example, there is a method based on back-off control, which includes a back-off window size allocation method and a size change method (change of random number generation range, etc.). Considering such variations, there are a plurality of collision avoidance methods. An optimal collision avoidance method is detected in advance for each number of terminals by simulation or the like, and is described in the operation mode correspondence table TBL accordingly.

  An example of the hidden terminal control method is RTS / CTS. For example, there are multiple hidden terminal control methods by changing the short frame interval SIFS and distributed control frame interval DIFS related to RTS / CTS, or by combining fragments (frame division methods) with RTS / CTS. To do. An optimal hidden terminal control method is detected for each number of terminals in advance by simulation or the like, and is described in the operation mode correspondence table TBL accordingly.

  FIG. 4 is a block diagram illustrating a functional schematic configuration of the wireless communication device 3 (3-1 to 3-3). The wireless communication device 3 includes a transmission / reception shared antenna 31, a transmission unit 32, a reception unit 33, a communication control unit 34, and a storage unit 35.

  These shared antenna 31, transmitting unit 32, receiving unit 33, communication control unit 34 and storage unit 35 correspond to the corresponding transmitting / receiving shared antenna 21, transmitting unit 22, receiving unit 23, communication control unit in the wireless communication management device 2, respectively. 26 and the storage unit 27. Some differences will be clarified in the description of operations described later.

  The storage unit 35 of the wireless communication device 3 also describes the operation mode correspondence table TBL shown in FIG. 3, a plurality of collision avoidance methods, and a plurality of hidden terminal control methods, and FIG. 8 for receiving a beacon frame. The processing program P35 shown in FIG.

(A-2) Operation of First Embodiment Next, a characteristic operation in the wireless network system 1 of the first embodiment will be described.

  The wireless network system 1 is initially started up by the wireless communication management device 2. At the time of start-up, only the wireless communication management device 2 (wireless communication device 3-0) belongs to the wireless network system 1.

  After the start-up, the wireless communication management device 2 performs communication for network management by broadcast (broadcast communication). Among network management communications, beacon frames are transmitted periodically. By transmitting the beacon frame, the management information of the entire network is notified to all the other wireless communication devices 3-1 to 3-3, and the wireless communication devices 3-0 to 3-3 are synchronized with each other.

  When receiving a beacon frame from the wireless communication management device 2, the wireless communication device 3-i trying to newly enter the wireless network system 1 issues an entry request to the wireless communication management device 2. Information necessary for communication in the network system 1 such as the permission of the network and the identification number in the network system. The wireless communication device 3-j that is about to leave the wireless network system 1 also performs communication with the wireless communication management device 2 according to a predetermined procedure for leaving. An existing procedure can be applied as a communication procedure when entering or leaving.

  With the communication at the time of entry with the wireless communication device 3-i and the communication at the time of leaving with the wireless communication device 3-j, the wireless communication management device 2 always has how many wireless communication devices 3 are in the network. It can be known whether it exists in the system 1. The management communication control unit 24 of the wireless communication management device 2 holds the number of such wireless communication devices 3 (number of terminals) at that time in the management storage unit 25.

  The management communication control unit 24 of the wireless communication management device 2 starts the process (program P25) shown in FIG. 5 when the wireless communication device 3 enters / leaves.

  When the processing shown in FIG. 5 is started, the management communication control unit 24 updates the number of terminals held in the management storage unit 25 according to entry / exit (step S1).

  And after giving the data of the updated terminal number to the communication control part 26 (step S2), it waits for the transmission timing of a beacon frame (step S3). At the beacon frame transmission timing, as shown in FIG. 6, data of the number of terminals held at a predetermined position of the beacon frame is inserted and the beacon frame is transmitted (broadcast) from the transmission unit 22 ( Step S4). In addition, when transmitting beacon frames that are periodically executed, meaningless data is inserted into the field for the number of terminals. Also, the number of terminals that have already been transmitted may be inserted again.

  The communication control unit 26 given the updated number of terminals from the management communication control unit 24 starts the processing (program P27) shown in FIG. 7, and supports the operation mode shown in FIG. 3 using the given number of terminals as a key. The corresponding record in the table TBL is searched (step S11), the identification code of the collision avoidance method and the identification code of the hidden terminal control method of the searched corresponding record are extracted (step S12), and the collision avoidance method specified by these identification codes And it resets as a method of performing a hidden terminal control method (step S13).

  When receiving the beacon frame, the communication control unit 34 of each wireless communication device 3 starts the process (program P35) shown in FIG. First, it is determined whether or not the number of terminals is inserted in the received beacon frame (step S21). When the number of terminals is inserted, the communication control unit 34 searches the corresponding record in the operation mode correspondence table TBL shown in FIG. 3 stored in the storage unit 35 using the number of inserted terminals as a key. (Step S22), the identification code of the collision avoidance method and the identification code of the hidden terminal control method of the searched corresponding record are extracted (Step S23), and the collision avoidance method and the hidden terminal control method specified by these identification codes are executed. The method is set again (step S24).

  When the number of terminals is not inserted in the received beacon frame, or when the number of terminals is inserted and the process of step S24 is executed, the same general process as before when a beacon frame is received is executed. (Step S25).

  Normal data communication is directly performed by the transmitting wireless communication device 3-d and the receiving wireless communication device 3-r. The transmitting wireless communication device 3-d attempting to transmit data recognizes the transmission timing while applying the set collision avoidance method. In addition, the transmission wireless communication device 3-d, the reception wireless communication device 3-r, and the other wireless communication device 3-p execute an operation according to the set hidden terminal control method.

(A-3) Effect of the First Embodiment According to the first embodiment, the operation according to the optimum collision avoidance method or hidden terminal control method according to the number of terminals in the network system is performed in the network system. It can be executed in synchronization with the wireless communication device.

  Further, according to the first embodiment, since the operation mode correspondence table is provided for each wireless communication device, the operation according to the individual characteristics of the wireless communication device 3 is described in the operation mode correspondence table. The operation according to the individual characteristics can be executed.

(B) Second Embodiment Next, the second embodiment of the wireless communication management device, the wireless communication device, the wireless network system, and the carrier sensing multiple access method according to the present invention is different from the first embodiment. The explanation will focus on the points.

  Note that the overall configuration of the wireless network system of the second embodiment is as shown in FIG. 2 described above, and the detailed configuration of the wireless communication management device 2 is as shown in FIG. The detailed configuration of the communication device 3 is as shown in FIG. 4 described above. In the following description, each component is specified using the reference numerals of these drawings.

  In the case of the first embodiment described above, the operation mode correspondence table TBL held in the storage units 27 and 35 of the wireless communication devices 3-0 to 3-3 is as shown in FIG.

  In the case of the second embodiment, the operation mode correspondence table TBL1 held in the storage units 27 and 35 of the wireless communication devices 3-0 to 3-3 is as shown in FIG. In the case of the second embodiment, the management storage unit 25 of the wireless communication management device 2 stores an operation mode correspondence table TBL2 as shown in FIG.

  As shown in FIG. 9, one record of the operation mode correspondence table TBL1 includes information such as an operation mode identification code, a collision avoidance method identification code, and a collision avoidance method identification code. On the other hand, as shown in FIG. 10, one record of the operation mode correspondence table TBL2 includes information on the number or range of the wireless communication devices (communication terminals) 3 belonging to the wireless network system 1 and the identification code of the operation mode.

  Although illustration of a flowchart is abbreviate | omitted, in 2nd Embodiment, each apparatus operate | moves as follows.

  The management communication control unit 24 of the wireless communication management device 2 determines the number of wireless communication devices 3 (number of terminals) belonging to the network system 1 when the wireless communication device 3 enters / leaves the network system 1. The operation mode identification code corresponding to the number of terminals is obtained from the operation mode correspondence table TBL2 shown in FIG.

  The management communication control unit 24 gives the obtained operation mode identification code to the communication control unit 26 of the wireless communication management device 2, and at this time, the communication control unit 26 gives the given operation mode identification code. The corresponding record in the operation mode correspondence table TBL1 shown in FIG. 9 is retrieved as a key, the identification code of the collision avoidance method and the identification code of the hidden terminal control method of the retrieved corresponding record are extracted, and the collision avoidance specified by these identification codes The method and the hidden terminal control method are reset as a method for executing.

  When the management communication control unit 24 obtains the operation mode identification code, the management communication control unit 24 waits for the beacon frame transmission timing. When the beacon frame transmission timing is reached, the management communication control unit 24 determines the beacon frame in advance as shown in FIG. The identification code of the operation mode obtained at the position is inserted, and the beacon frame is transmitted (broadcast) from the transmitter 22. When transmitting beacon frames that are periodically executed other than this, meaningless data is inserted into the field of the identification code of the operation mode. Further, the operation mode that has already been transmitted may be inserted again.

  When receiving the beacon frame, the communication control unit 34 of each wireless communication device 3 determines whether or not the operation mode identification code is inserted in the received beacon frame. The corresponding record in the operation mode correspondence table TBL1 shown in FIG. 9 stored in the storage unit 35 is searched using the number of terminals as a key, and the identification code of the collision avoidance method of the searched corresponding record and the identification of the hidden terminal control method The codes are taken out and reset as a method for executing the collision avoidance method and the hidden terminal control method specified by the identification codes.

  Also according to the second embodiment, the operation according to the optimum collision avoidance method or hidden terminal control method according to the number of terminals in the network system can be executed in synchronization with all the wireless communication devices in the network system. .

  Further, according to the second embodiment, since the wireless communication management device determines the operation mode and notifies all wireless communication devices, unified operation is possible.

(C) Other Embodiments In each of the above embodiments, the operation mode is determined based on the number of terminals existing in the network system. However, there is a possibility that a terminal (wireless communication apparatus) in the sleep mode or the like communicates. The operation mode may be determined using the number of active terminals excluding terminals with no terminal.

  In the above embodiments, the number of terminals or the operation mode is included in the beacon frame and notified to the wireless communication apparatus. However, the number of terminals or the operation mode is notified to the wireless communication apparatus by other methods. May be. For example, the notification may be made with a command addressed to all the wireless communication apparatuses in operation.

  Further, in each of the above-described embodiments, the wireless communication management device functions as a wireless communication device, but may be a device that executes only the management function.

  Furthermore, in the description of each of the embodiments described above, the switching between the collision avoidance method (means) and the hidden terminal control method (means) is shown according to the number of terminals, but the switching target is not limited to this. For example, a system that switches only the collision avoidance method (means) or a system that switches only the hidden terminal control method (means) may be used. The item to be switched may be other than the collision avoidance method (means) and the hidden terminal control method (means). For example, the length of one segment in segmentation may be switched.

It is a block diagram which shows the detailed structure of the radio | wireless communication management apparatus which concerns on 1st Embodiment. 1 is a block diagram illustrating a schematic configuration of a wireless network system according to a first embodiment. It is explanatory drawing which shows the operation mode correspondence table which concerns on 1st Embodiment. It is a block diagram which shows the detailed structure of the radio | wireless communication apparatus which concerns on 1st Embodiment. It is a flowchart which shows the operation | movement performed when the communication control part for management of the radio | wireless communication management apparatus which concerns on 1st Embodiment has entered / leaved the radio | wireless communication apparatus. It is explanatory drawing which shows the structure of the beacon frame which concerns on 1st Embodiment. It is a flowchart which shows the switching operation of the operation mode of the radio | wireless communication management apparatus which concerns on 1st Embodiment. 4 is a flowchart illustrating an operation mode switching operation of the wireless communication apparatus according to the first embodiment. It is explanatory drawing which shows the operation mode correspondence table | surface (the 1) which concerns on 2nd Embodiment. It is explanatory drawing which shows the operation mode correspondence table | surface (the 2) based on 2nd Embodiment. It is explanatory drawing which shows the structure of the beacon frame which concerns on 2nd Embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Wireless network system, 2 ... Wireless communication management apparatus, 3-1 to 3-3 ... Wireless communication apparatus, 21 ... Transmission / reception shared antenna, 22 ... Transmission part, 23 ... Reception part, 24 ... Management communication control part, 25 ... Management storage unit 26 ... Communication control unit 27 ... Storage unit 31 ... Transmission / reception shared antenna 32 ... Transmission unit 33 ... Reception unit 34 ... Communication control unit 35 ... Storage unit

Claims (6)

In a carrier-sensitive multiple access method in which a wireless communication device that intends to transmit data grasps the transmission timing of data depending on whether or not a carrier signal is sensed,
The wireless communication management device captures the number of wireless communication devices belonging to the wireless network system, and each wireless communication device determines the number of wireless communication devices captured by the wireless communication management device from a plurality of selectable operation modes. A carrier-sensing multiple access method characterized in that an operation mode is selected according to the operation.   The carrier sensing multiple access method according to claim 1, wherein the operation mode defines a collision avoidance method.   3. The carrier sensing multiple access method according to claim 1, wherein the operation mode defines a hidden terminal control method. A device number grasping means for capturing the number of wireless communication devices belonging to a wireless network system to which the carrier sensing multiple access method is applied;
An operation mode instruction means for directly or indirectly instructing each wireless communication device belonging to the wireless network system among the plurality of operation modes that can be executed by each wireless communication device. A wireless communication management device comprising: A mode instruction receiving means for recognizing an operation mode directly or indirectly instructed from a wireless communication management device of a wireless network system to which the carrier sensing multiple access method belongs;
A wireless communication device comprising: an operation mode switching unit that executes an operation in an instructed operation mode among a plurality of operation modes.   A wireless network system comprising the wireless communication management device according to claim 4 and the plurality of wireless communication devices according to claim 5.

Images