JP2005303762A - Ad hoc network system and radio terminal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ad hoc network system for efficiently selecting a master for transmitting an synchronization frame. <P>SOLUTION: Each radio terminal for composing the ad hoc network system participates in competition for acquiring a synchronization frame transmission right when an own terminal is in a transmission wait state, where a transmission wait frame is held, or it cannot be confirmed that the state of the master is in the transmission wait state at the last synchronization timing at synchronization timing of a fixed period. And the radio terminal winning the competition for acquiring the synchronization frame transmission tight operates as the master until the next synchronization timing. For the radio terminal that is not in the transmission wait state, an opportunity for participating in the competition for acquiring the synchronization frame transmission right is reduced, and power consumption by synchronization frame transmission preparation, synchronization frame transmission, and the like is suppressed. And the radio terminal for participating in the competition for acquiring the synchronization frame transmission right is restricted, thus reducing the possibility of collision in the synchronization frame. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an ad hoc network system that is composed of a plurality of wireless terminals that can be either a parent device or a child device, and that efficiently selects a parent device that transmits a synchronization frame.

  As a method of selecting a base unit in a conventional ad hoc network, the reception field strength data from all wireless terminals is collected by a plurality of base units, and even when the number of wireless terminals increases, the wireless terminal at the optimal communication position is selected. There was one that was selected as an optimal parent device in a short time (see, for example, Patent Document 1).

Further, in the ad hoc network described in IEEE Std 802.11-1999, all wireless terminals in the ad hoc network determine a waiting time within a specific range by using a random number for each synchronization timing. Then, the wireless terminal with the shortest waiting time among all the wireless terminals transmits a synchronization frame, operates as a master unit until the next synchronization timing, and responds to a probe request from a wireless terminal newly joining the ad hoc network. ing.
Japanese Patent Laid-Open No. 10-155184

  However, in the conventional configuration, a wireless terminal that does not transmit a frame is given an opportunity to operate as a base unit, and wasteful power is consumed by participating in an ad hoc network even if the frame is not transmitted. It had the problem of end.

  In addition, in the ad hoc network described in IEEE Std 802.11-1999, all wireless terminals participate in the competition for acquiring the right to transmit synchronization frames. Therefore, if the scale of the ad hoc network increases, the synchronization frames may collide. It also had the problem of becoming higher.

  The present invention solves the above-described conventional problems, and provides an ad hoc network system that suppresses useless power consumption of a wireless terminal that does not hold a transmission waiting frame and further suppresses the possibility of loss of a synchronization frame. With the goal.

  In order to solve the conventional problem, in the ad hoc network system of the present invention, each wireless terminal constituting the ad hoc network system is in a transmission waiting state in which the self terminal holds a transmission waiting frame at a certain period of synchronization timing. Or if it cannot be confirmed that the state of the master unit at the previous synchronization timing is in a transmission waiting state, it participates in a competition for acquiring a synchronization frame transmission right. Further, the wireless terminal that wins the competition for acquiring the synchronization frame transmission right and transmits the synchronization frame operates as a master unit until the next synchronization timing and acquires the priority transmission right of the frame. Other wireless terminals operate as slave units until the next synchronization timing.

  With this configuration, it is possible to reduce the chances of participation in the competition for acquiring the right to transmit a synchronization frame by a wireless terminal that does not hold a transmission waiting frame.

  According to the ad hoc network system of the present invention, a wireless terminal that is not in a transmission waiting state has fewer opportunities to transmit a synchronization frame, and has fewer opportunities to operate as a parent device, thereby suppressing wasteful power consumption.

  In addition, since the wireless terminals participating in the synchronization frame transmission right acquisition competition are limited, the possibility of synchronization frame collision is reduced, and the frame transmission right acquisition competition after the synchronization frame can be avoided. Can be increased.

  Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1)
FIG. 1 is a block diagram showing a functional configuration of each wireless terminal of the ad hoc network system according to Embodiment 1 of the present invention. The functional configuration of each wireless terminal constituting the ad hoc network system is common.

  The wireless terminal 10 in FIG. 1 operates as a parent device or a child device, and transmits a wireless transmission unit 101 and a wireless reception unit 102 for wirelessly transmitting and receiving data through a wireless line, a scanning unit 103 that scans a wireless channel, and wireless transmission and reception The antenna 104 is provided.

  In addition, a parent device control unit 105 that performs control for the self terminal to operate as a parent device, a child device control unit 106 that performs control for the self terminal to operate as a child device, a parent device operation and a child device operation. An operation switching control unit 107 that performs control for switching is provided. And it has the power supply control part 108 which performs the power supply control to each part.

  Furthermore, the storage unit 109 that temporarily stores the base unit state information, the transmission waiting frame, and the like, the determination unit 110 that determines whether or not to participate in the synchronization frame transmission right acquisition competition at the synchronization timing, and the synchronization timing are counted. The timer unit 111 that corrects the synchronization timing every time the synchronization frame is received and counts various other timings is provided.

  FIG. 2 shows a configuration example of the synchronization frame. In FIG. 2, a synchronization frame includes a header including the frame type, frame length, destination / source terminal information, management information including an ad hoc network identifier, synchronization timing period information, and the like. It consists of base unit status information indicating whether or not and a CRC code for frame error detection. Here, the parent device state information is set to “1” when the parent device is in a transmission waiting state, and is set to “0” otherwise.

  FIG. 3 shows a configuration example of a transmission waiting frame. The transmission waiting frame includes a header including the frame type, frame length, destination / source terminal information, and the like, data, and a CRC code for detecting a frame error.

  Next, the operation procedure of the wireless terminal 10 will be described using the flowchart shown in FIG. First, after the power is turned on (S400), the wireless terminal 10 scans the wireless channel by the scanning unit 103 to check whether an ad hoc network has already been established (step S401). The scanning unit 103 performs the determination in step S401 based on whether or not a synchronization frame is detected or whether or not there is a response to a probe request for the ad hoc network.

  When the ad hoc network is not established, the wireless terminal 10 switches the operation to the parent device operation by the operation switching control unit 107, notifies the synchronization frame, establishes the ad hoc network, and operates as the parent device until the next synchronization timing. (Step S402). The period Ta of the synchronization timing is determined by the wireless terminal that has established the ad hoc network. When a wireless terminal newly participating in the ad hoc network transmits a probe request frame, the parent device transmits a probe response frame. The probe response frame includes synchronization timing period information.

  If the ad hoc network has already been established, the wireless terminal 10 switches the operation to the slave unit operation by the operation switching control unit 107, synchronizes with the synchronization frame, performs an authentication procedure with the master unit, and the like. Joins the network and operates as a slave until the next synchronization timing (step S403). When receiving the synchronization frame, the wireless terminal 10 grasps the state of the parent device from the parent device state information in the synchronization frame, and updates the parent device state information in the storage unit 109.

  The wireless terminal 10 transmits / receives a frame based on distributed control by a CSMA / CA (Carrier Sense Multiple Access Collision Avoidance) method until the next synchronization timing (steps S404 and S405). The synchronization timing is grasped by the timer unit 111.

  When the synchronization timing comes, the wireless terminal 10 confirms whether or not the own terminal holds a transmission waiting frame in the storage unit 109 by the determination unit 110 (step S406), and waits for transmission holding the transmission waiting frame. In the case of the state, it participates in the synchronization frame transmission right acquisition competition (step S408).

  When the self terminal is not in a transmission waiting state, the determination unit 110 of the wireless terminal 10 determines whether the state of the parent device at the previous synchronization timing is a transmission waiting state based on the parent device state information in the storage unit 109. (Step S407). When it is determined that the parent device is not in a transmission waiting state, it participates in a synchronization frame transmission right acquisition competition (step S408).

  When the wireless terminal 10 participates in the synchronization frame transmission right acquisition competition, the operation switching control unit 107 switches the operation to the parent device operation and prepares for transmission of the synchronization frame.

  At the synchronization timing, the power control unit 108 supplies power to the wireless reception unit 102 for receiving the synchronization frame. Further, the power supply control unit 108 supplies power to the wireless transmission unit 101 in preparation for synchronization frame transmission when the wireless terminal 10 participates in the synchronization frame transmission right acquisition competition, and to the wireless transmission unit 101 when not participating. The power is not supplied. In this way, wasteful power consumption is suppressed by controlling the power supply to the wireless transmission unit 10 at the synchronization timing.

  When acquiring the synchronization frame transmission right, the wireless terminal 10 transmits a synchronization frame (step S409). On the other hand, when the synchronization frame is not transmitted, the wireless terminal 10 switches the operation to the slave unit operation by the operation switching control unit 107, receives the synchronization frame, synchronizes with the timer unit 111 (step S410), and until the next synchronization timing. It operates as a slave unit (steps S404 and S405). When receiving the synchronization frame, the wireless terminal 10 grasps the state of the parent device from the parent device state information in the synchronization frame, and updates the parent device state information in the storage unit 109.

  At the synchronization timing, the slave unit updates the master unit status information in the storage unit 109 as “0” when the status of the master unit cannot be grasped because the sync frame collides and cannot receive the sync frame.

  In addition, when the wireless terminal 10 transmits a synchronization frame in a transmission waiting state, the wireless terminal 10 transmits the transmission waiting frame with priority over other terminals (step S411), and operates as a master unit until the next synchronization timing (step S404). , S405). If the parent device is not in the transmission waiting state, step S411 is omitted.

  When the wireless terminal 10 becomes the parent device, the wireless terminal 10 participates in a synchronization frame transmission right acquisition competition at the next synchronization timing. As a result, at least one wireless terminal participates in the synchronization frame transmission right acquisition competition at the next synchronization timing, so that the loss of the synchronization frame does not occur.

  Returning to step S404, the wireless terminal 10 repeats the above operation procedure at each synchronization timing. When the wireless terminal 10 leaves the ad hoc network, the ad hoc network is maintained because any of the remaining wireless terminals transmits a synchronization frame.

  Next, a specific operation example of each wireless terminal at the synchronization timing will be described with reference to FIG. In FIG. 5, the ad hoc network includes three wireless terminals 10, 11, and 12. The synchronization timing period is Ta. At the synchronization timing 500, the wireless terminals 10 and 11 hold the transmission waiting frames 503 and 504, and the wireless terminal 12 does not hold the transmission waiting frame. The wireless terminals 10 and 11 participate in a synchronization frame transmission right acquisition competition at the synchronization timing 500. Then, the wireless terminals 10 and 11 prepare for transmission of a synchronization frame, and the timer unit 111 determines a delay time within a specific range by a random number.

  In FIG. 5, the delay time of the wireless terminal 10 is T1, and the delay time of the wireless terminal 11 is T2. Since T1 is shorter than T2, the wireless terminal 10 transmits a synchronization frame with a delay of T1 from the synchronization timing. In the synchronization frame, the management information includes information related to the delay time T1, and the parent device state information is “1” indicating that the parent device is in a transmission waiting state.

  Since the wireless terminal 11 receives the synchronization frame before the self terminal transmits the synchronization frame, the wireless terminal 11 cancels the transmission of the synchronization frame. The wireless terminals 11 and 12 receive the synchronization frame and synchronize with the timer unit 111 in consideration of the delay time T1. Further, the wireless terminals 11 and 12 determine that the parent device is in a transmission waiting state from the parent device state information in the synchronization frame.

  The radio terminal 10 preferentially transmits a transmission waiting frame 503 after a specific time Tb from the transmission of the synchronization frame. Thereafter, each wireless terminal transmits and receives a frame based on the distributed control or the like until the next synchronization timing 501.

  The transmission-waiting frame 503 is addressed to the wireless terminal 12, and the wireless terminals 11 and 12 detect and receive the transmission-waiting frame 503 after a specific time Tb from the reception of the synchronization frame, so that the wireless terminal 10 serving as the master unit at the synchronization timing 500 It may be determined that the transmission waiting frame 503 is held.

  Next, it is assumed that the wireless terminal 11 holds the transmission waiting frame 504 at the synchronization timing 501. At the synchronization timing 501, the wireless terminal 10 that is the parent device until immediately before and the wireless terminal 11 that holds the transmission waiting frame 504 participate in the competition for acquiring the synchronization frame transmission right.

  At the synchronization timing 501, the delay time of the wireless terminal 10 is T3, and the delay time of the wireless terminal 11 is T4. Since T4 is shorter than T3, the wireless terminal 11 transmits a synchronization frame with a delay of T4 from the synchronization timing 501, and preferentially transmits a transmission waiting frame 504 after a specific time Tb from the transmission. Also after the synchronization timing 502, each of the wireless terminals 10, 11, and 12 repeats the operation procedure based on the flowchart of FIG.

  According to such a configuration, a wireless terminal that is not in a transmission waiting state has fewer opportunities to participate in the synchronization frame transmission right acquisition competition, and the opportunity to operate as a master unit also decreases. Power consumption due to can be suppressed.

  In addition, since the number of terminals participating in the synchronization frame transmission right acquisition competition decreases, the possibility of synchronization frame collision is reduced and the ad hoc network is stabilized. Furthermore, since competition for frame transmission rights after receiving the synchronization frame can be avoided, useless blank time after receiving the synchronization frame can be reduced, and the transmission efficiency of the ad hoc network can be improved.

  In the first embodiment, the parent device sets a specific time Tb until transmission of a transmission waiting frame after transmission of a synchronization frame in accordance with the priority of the transmission waiting frame, and the child device transmits high priority. When waiting frames are held, set the time interval until the transmission waiting frame is sent after receiving the synchronization frame according to the priority of the transmission waiting frame, and the slave unit waits for transmission with a higher priority than the parent unit. When the frame is held, the slave unit may be able to transmit the transmission waiting frame preferentially.

  Further, the synchronization frame may be preferentially transmitted to the wireless terminal in the transmission waiting state by making the delay time generation range of the wireless terminal in the transmission waiting state narrower than the delay time generation range of the wireless terminal not in the transmission waiting state. .

(Embodiment 2)
In the second embodiment, when the master unit holds a transmission waiting frame in the first embodiment, the synchronization frame includes data in the transmission waiting frame for transmission.

  The functional configuration of each wireless terminal of the ad hoc network system in the second embodiment is as shown in FIG. 1 and is the same as that in the first embodiment. Each wireless terminal operates based on the flowchart shown in FIG. 4 excluding step S411.

  FIG. 6 shows a configuration example of a synchronization frame when the base unit in the second embodiment holds a transmission waiting frame. In FIG. 6, the synchronization frame includes a header including frame type, frame length, destination / source terminal information, management information including an ad hoc network identifier and synchronization timing period information, and data in a transmission waiting frame. And a CRC code for frame error detection.

  Further, the configuration example of the synchronization frame when the parent device is not in the transmission waiting state is the same as that of the first embodiment. Therefore, the slave unit determines the status of the master unit depending on whether or not the data part is included in the synchronization frame at the synchronization timing.

  According to such a configuration, the synchronization frame and the transmission waiting frame can be transmitted together, so that the transmission efficiency of the ad hoc network system can be increased.

  The ad hoc network system according to the present invention has a feature that the power consumption reduction effect of the wireless terminal increases as the scale increases, and is useful as a large-scale ad hoc network system.

The block diagram which shows the function structure of each radio | wireless terminal of the ad hoc network system in Embodiment 1, 2 of this invention The figure which shows the structural example of the synchronous frame in Embodiment 1 of this invention. The figure which shows the structural example of the transmission waiting frame in Embodiment 1 of this invention. The flowchart which shows the operation | movement procedure of each radio | wireless terminal in Embodiment 1 of this invention. The figure which shows the specific operation example of each radio | wireless terminal in the synchronous timing in Embodiment 1 of this invention. The figure which shows the structural example of the synchronous frame in case the main | base station in Embodiment 2 of this invention hold | maintains the transmission waiting frame.

Explanation of symbols

10, 11, 12 Wireless terminal 101 Wireless transmission unit 102 Wireless reception unit 103 Scan unit 104 Antenna 105 Base unit control unit 106 Slave unit control unit 107 Operation switching control unit 108 Power supply control unit 109 Storage unit 110 Judgment unit 111 Timer unit 500, 501, 502 Synchronization timing 503 Transmission waiting frame addressed to wireless terminal 12 504 Transmission waiting frame addressed to wireless terminal 10 Ta Synchronization timing period Tb, T1, T2, T3, T4 Delay time

Claims (9)

It has a plurality of wireless terminals that can be either a master unit or a slave unit,
Of the wireless terminals that participated in the synchronization frame transmission right acquisition competition for each synchronization timing of a certain period, the wireless terminal that acquired the synchronization frame transmission right transmits a synchronization frame and operates as a master unit until the next synchronization timing,
The other wireless terminal is an ad hoc network system that is synchronized by the synchronization frame and operates as a slave unit until the next synchronization timing,
The synchronization timing is determined by the wireless terminal that established the network,
When each wireless terminal is in a transmission waiting state in which the own terminal holds a transmission waiting frame at the synchronization timing, or when it cannot be confirmed that the state of the master unit at the previous synchronization timing is in a transmission waiting state, An ad hoc network system that participates in a competition for acquisition of a synchronization frame transmission right. The base unit participates in the synchronization frame transmission right acquisition competition at the next synchronization timing after transmitting the synchronization frame, so that at least one wireless terminal participates in the synchronization frame transmission right acquisition competition. The ad hoc network system according to claim 1. The master unit acquires the transmission waiting frame priority transmission right after the transmission of the synchronization frame, and when the own terminal is in a transmission waiting state, transmits the transmission waiting frame preferentially,
2. The ad hoc network system according to claim 1, wherein another wireless terminal determines whether or not the base unit is in a transmission waiting state based on whether or not the transmission waiting frame can be detected. The master unit sets the time interval until the transmission waiting frame is transmitted after the transmission of the synchronization frame according to the priority of the transmission waiting frame,
When the slave unit holds a high-priority transmission-waiting frame, it sets the time interval until the transmission-waiting frame is transmitted after receiving the synchronization frame according to the priority of the transmission-waiting frame,
4. The ad hoc network system according to claim 3, wherein when the slave unit holds a transmission wait frame having a higher priority than the master unit, the slave unit preferentially transmits the transmission wait frame. The synchronization frame includes base unit state information indicating whether the base unit is in a transmission waiting state,
The ad hoc network system according to claim 1, wherein the slave unit determines whether the master unit is in a transmission waiting state based on the master unit state information. When the base unit is in the transmission waiting state, the base unit transmits the synchronization frame including the data in the transmission waiting frame,
2. The ad hoc network system according to claim 1, wherein another wireless terminal determines the state of the master unit based on the content of the synchronization frame. Wireless terminals participating in the synchronization frame transmission right acquisition competition prepare for transmission of synchronization frames, determine the delay time within a specific range by random numbers,
A wireless terminal with the shortest delay time among wireless terminals participating in the synchronization frame transmission right acquisition competition transmits a synchronization frame,
2. The ad hoc network system according to claim 1, wherein other wireless terminals receive the synchronization frame without transmitting the synchronization frame. 8. The ad hoc network system according to claim 7, wherein a delay time generation range of a wireless terminal waiting for transmission in the synchronization frame transmission right acquisition competition is narrower than a delay time generation range of a wireless terminal not waiting for transmission. In the ad hoc network system according to claim 1,
Wireless transmission / reception means for performing wireless transmission / reception of frames through a wireless line;
Synchronization processing means for synchronizing with the ad hoc network system;
Storage means for temporarily storing the master unit status information and the transmission waiting frame;
Determination means for determining whether or not to participate in a synchronization frame transmission right acquisition competition based on the information stored in the storage means;
A wireless terminal comprising: control means for performing operation switching control and power supply control on the basis of the judgment by the judgment means, and operating the own terminal as a parent device or a child device.

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