JP2010041694A - Communication device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve communication performance by suppressing collision of packets without using various kinds of packets. <P>SOLUTION: A communication device includes: a transmitting circuit 19 that periodically transmits a data packet in timing other than a non-transmission period in a basic term and transmits a collision detection packet when data other than one data packet are received in prescribed timing during the basic term; a receiving circuit 12 for receiving a data packet from another terminal; and a non-transmission period setting section 15 for canceling the non-transmission period when data other than one data packet are received in prescribed timing during the basic term. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a communication device.

  2. Description of the Related Art Conventionally, there has been proposed a wireless system that transmits information by broadcasting (broadcasting) individual wireless terminal devices to surrounding wireless terminal devices without using a control station such as a base station. As an example of realizing such a communication form, in a CSMA (Carrier Sense Multiple Access) method, which is one of communication methods used in a wireless LAN, a terminal (node) that wants to transmit data is a packet of another terminal. The communication status is monitored (carrier sense), and transmission is started when the channel is free.

  In such a wireless system, for example, a predetermined terminal monitors the communication status of a terminal existing within a range where radio waves around it reach by carrier sense.

  For this reason, when there are many other terminals in the vicinity, there is a case where the timing for transmitting own data cannot be obtained and the data transmission is greatly delayed. For this reason, there is a problem that reliability cannot be guaranteed when the number of terminals and communication traffic increase.

  Furthermore, when there are many other terminals in a place where direct carrier sense outside the range where radio waves reach cannot be detected, the communication status of those terminals cannot be detected, and other data is transmitted when the predetermined terminal itself transmits data. When colliding with terminal communication (so-called hidden terminal problem) occurs. The wireless LAN has means for avoiding this communication collision using a method called RTS / CTS (Request To Send / Clear To Send). Although this method is effective when it is desired to communicate with a specific terminal, it cannot be applied in the case of broadcast communication, and thus there is a problem that it is impossible to avoid the collision of the packet communication.

  Therefore, in order to solve the above problem, a method of accessing a frame by dividing it into n slots in time is proposed (see Patent Document 1). The wireless terminal device described in Patent Document 1 monitors slot occupancy information in units of frames, and exchanges information with other terminals by embedding slot occupancy information in a transmission packet in addition to transmission data of the terminal itself. To do. The frame is composed of, for example, 100 ms, and each slot is occupied by a different terminal.

Also, with respect to the so-called hidden terminal problem, the technique of Patent Document 1 embeds frame information indicating various occupation states of slots in a packet, and based on the reception status of the packet and the frame information of the packet, Packet collision is avoided in consideration of existence.
JP 2007-28550 A

  However, since the technique of Patent Document 1 is based on the premise that frame information exists in a packet, there is a problem that packet collision cannot be avoided for a packet that does not include frame information.

  Furthermore, since the technique of Patent Document 1 needs to embed frame information indicating various occupation states of slots in a packet, the frame information included in one packet increases. As a result, there are problems that the types of packets increase and the transmission target data in one packet cannot be increased.

  The present invention has been proposed to solve the above-described problems, and provides a communication device capable of improving communication performance by suppressing packet collision without using various types of packets. With the goal.

  A communication apparatus according to the present invention includes a data packet transmitting unit that periodically transmits a data packet at a timing other than a transmission prohibition period of a basic cycle, a packet receiving unit that receives a data packet from another terminal, and the packet receiving unit When data other than one data packet is received at a predetermined timing of the basic period, a collision detection packet transmitting means for transmitting a collision detection packet and one data at a predetermined timing of the basic period are transmitted by the packet receiving means. Transmission prohibition period setting means for canceling the transmission prohibition period when data other than packets is received.

  Here, the transmission prohibition period control means, when one data packet is received at the predetermined timing of the basic period by the packet receiving means, a period including the reception timing of the data packet of the basic period is transmitted. It may be set to a prohibited period.

  The invention according to the present invention includes a data packet transmitting means for periodically transmitting data packets at a timing other than a transmission prohibition period of a basic period, a packet receiving means for receiving a collision detection packet from another terminal, and the packet receiving means Transmission prohibition period setting means for setting the transmission prohibition period according to the reception timing of the collision detection packet.

  Here, when the collision detection packet is received by the packet reception unit within a predetermined period after the transmission of the data packet by the data packet transmission unit, the transmission prohibition period setting unit is configured to store the data packet of the basic period. When the next transmission timing is set to a transmission prohibition period, and the collision detection packet is not received by the packet reception means within a predetermined period after the transmission of the data packet by the data packet transmission means, after the transmission of the data packet A period until the end of the basic period may be set as a transmission prohibition period.

  The communication apparatus according to the present invention transmits a collision detection packet when data other than one data packet is received at a predetermined timing of the basic cycle, and sets a transmission prohibition period of the basic cycle to periodically transmit the data packet. By releasing, it is notified that there is a data packet collision, and the transmission opportunities are increased.

  The communication apparatus according to the present invention transmits a data packet so that the data packet does not collide by setting a transmission prohibition period of a basic period for periodically transmitting the data packet according to the reception timing of the collision detection packet. be able to.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a block diagram showing a configuration of a communication device of a wireless communication network according to an embodiment of the present invention. The wireless communication network is dynamically configured by each communication apparatus broadcasting a packet periodically (every basic period). Here, the basic period is divided into a plurality of slots, and each communication apparatus occupies one of the slots and transmits a data packet. Hereinafter, as necessary, a communication device to be described is referred to as an own terminal, and a communication device around the own terminal is referred to as a peripheral terminal or another terminal.

  The communication device receives a packet transmitted from another wireless terminal device via the reception antenna 11, and a packet that detects a received packet and detects at which slot (at which timing) the received packet is transmitted. A detection unit 13, a packet demodulation unit 14 that demodulates data transmitted from the detected packet to generate reception information, and a transmission prohibition period setting that sets a transmission prohibition period based on timing information of the detected packet Part 15.

  Further, the communication apparatus includes a packet generation unit 16 that generates a packet based on transmission information, a collision detection packet generation unit 17 that generates a collision detection packet when a packet collision is detected based on a demodulated packet, and a transmission A transmission timing control unit 18 that controls the timing, a transmission circuit 19 that transmits the generated packet via the antenna 20, and a control circuit 30 that controls the overall operation are provided.

  The collision detection packet generation unit 17 is based on the demodulation result of the packet demodulation unit 14, for example, at a predetermined timing, although data other than one packet (for example, there are two or more packets or a certain amount of received power). When data that could not be demodulated) is obtained, a collision detection packet indicating that the packet collided in that slot is generated.

  The transmission timing control unit 18 controls the transmission circuit 19 for the transmission timing of the data packet generated by the packet generation unit 16 and the collision detection packet generated by the collision detection packet generation unit 17.

  FIG. 2 is a diagram illustrating a configuration of a basic period transmitted and received by n communication apparatuses. A data packet and a collision detection packet indicate one transmission / reception combination. That is, in this embodiment, there are only two types of packets. One basic period is set to, for example, 100 msec, and n data packets exist.

  FIG. 3 is a state transition diagram of the communication apparatus. The communication apparatus transits the states of “reception standby state”, “data packet transmission process”, “collision detection packet reception process for data of own terminal”, “signal reception process”, and “collision detection packet transmission process”. .

  Specifically, in a reception standby state, the communication apparatus shifts to a data packet transmission process when there is no reception signal and there is data to be transmitted, and shifts to a signal reception process when a reception signal is detected.

  When the data packet cannot be transmitted in the data packet transmission process, the communication apparatus shifts to a reception standby state. When the data packet transmission process is completed, the communication apparatus shifts to a collision detection packet reception process for the data of the terminal itself. Then, in the collision detection packet reception process for the data of the terminal itself, the communication apparatus shifts to a reception standby state when the process is completed or when a predetermined period has elapsed.

  On the other hand, in the signal reception process, the communication apparatus shifts to a reception standby state when the process is completed, and shifts to a collision detection packet transmission process when the process is completed and a reply is necessary. Then, in the collision detection packet transmission process, the communication apparatus shifts to a reception standby state when the process is completed. Hereinafter, the data packet transmission process, the data packet transmission process of the own terminal, the signal reception process, and the collision detection packet transmission process will be described.

  FIG. 4 is a diagram showing an arrangement relationship of terminals A to F configured as shown in FIG. Here, the ellipse indicates an area where the packet reaches. For example, terminal C transmits a packet only to terminals B, D, and F, but terminal B transmits a packet only to terminals A and C.

  FIG. 5 is a timing chart showing packet transmission / reception timings of the terminals A to F when the data packets of the terminals B and D collide at the terminal C. Here, “DATA” is a data packet, “COL” is a collision detection packet, “NAV period” is a transmission prohibition period, “Set NAV” is a transmission prohibition period setting, and “NOT Set NAV” is a transmission prohibition period setting release. Is shown.

(Data packet transmission processing)
When there is no reception signal and there is data to be transmitted in the reception standby state, the communication apparatus shifts to a data packet transmission process and executes the next process.

  FIG. 6 is a flowchart showing a processing routine of “data packet transmission processing”. In step S1, the transmission timing control unit 18 determines whether or not the current timing is the transmission prohibition period set by the transmission prohibition period setting unit 15. If the determination is affirmative, the transmission timing control unit 18 is in a state of “there is data to be transmitted”. If the determination is negative, the process proceeds to step S2.

  In step S2, the transmission timing control unit 18 measures the reception sensitivity of each slot based on the detection result of the reception circuit 12 or the packet detection unit 13 to determine whether or not a carrier has been detected. Shifts to the reception standby state in the state of “data to be transmitted”, and shifts to step S3 when a negative determination is made.

  In step S3, the transmission timing control unit 18 controls the transmission circuit 19 to transmit the data packet generated by the packet generation unit, and ends this routine. Thereby, the data packet is transmitted to each terminal via the antenna 20. And it transfers to the collision detection packet reception process with respect to the data of the own terminal.

  In addition, when it is not a transmission prohibition period (determination determination of step S1) and the condition of carrier non-detection (determination determination of step S2) is not satisfied, there is “data to be transmitted”, but “reception standby state” and “ It goes back and forth between “data packet transmission processing”. In this case, when it is time to transmit the next data packet, processing for discarding the previous data to be transmitted and transmitting new data is performed.

(Collision detection packet reception processing)
FIG. 7 is a flowchart showing a processing routine of “collision detection packet reception processing for data of own terminal”. In step S11, the transmission timing control unit 18 determines whether a predetermined period (T _collect ) has elapsed since the data packet transmission in step S3 described above. If the determination is affirmative, the process proceeds to step S14. The process proceeds to step S12.

In step S12, the packet receiving unit 13 determines whether a collision detection packet for the data of the terminal itself has been received from the peripheral terminal. If the determination is affirmative, the process proceeds to step S13. If the determination is negative, the process returns to step S11. When the collision detection packet is received within a predetermined period (T _collect ) after transmission of the data packet of the own terminal, the collision detection packet is regarded as a collision detection packet for the own terminal, and is received during the other period. If it is, it is regarded as a collision detection packet for the hidden terminal.

  In step S13, since the packet collision with the hidden terminal is detected, the transmission prohibition period setting unit 15 is one basic cycle after the previous data packet transmission timing to change the data packet transmission timing of the next terminal. Is set to the transmission prohibited period.

  For example, as shown in FIG. 5, when the terminal D receives the collision detection packet, the terminal D sets a transmission prohibition period one basic period after the transmission timing of the immediately preceding data packet. Thereby, the data packet transmission timing is changed. Then, this routine is finished, and a transition is made to a reception standby state.

On the other hand, in step S14, the transmission prohibition period setting unit 15 sets a transmission prohibition period to reserve the next transmission timing. Specifically, the transmission prohibition period setting unit 15 sets the transmission prohibition period from the time when a predetermined period ( _Tcollect ) after transmission of the data packet of the terminal itself has elapsed to the end of the basic period.

For example, as shown in FIG. 5, since the collision detection packet has not been received within a predetermined period (T _collect ) after the transmission of the data packet, the terminal B receives a predetermined period (T _collect after the transmission of the data packet of its own terminal. ) Until the end of the basic period is set as the transmission prohibition period. Thereby, the transmission timing of the data packet of the terminal B is set to the same timing as the previous time. Then, this routine is finished, and a transition is made to a reception standby state.

(Signal reception processing)
Further, when the communication apparatus detects a reception signal in the “reception standby state”, the communication apparatus shifts to “signal reception process” and executes the next process.

  FIG. 8 is a flowchart showing the processing routine of “signal reception processing”. In step S21, the receiving circuit 12 shown in FIG. 1 receives a packet of another terminal (peripheral terminal), the packet detection unit 13 detects the packet, and the process proceeds to step S22.

  In step S22, the transmission prohibition period setting unit 15 determines the type of the packet detected by the packet detection unit 13, and proceeds to step S23 if it is a data packet, and proceeds to step S24 if it is a collision detection packet.

  In step S23, the transmission prohibition period setting unit 15 waits for a predetermined period, ends this routine, and proceeds to a collision detection packet transmission process. For example, as shown in FIG. 5, terminals A and C receive a data packet from terminal B, and terminal E receives a data packet from terminal D.

  On the other hand, in step S24, since the collision detection packet with respect to the data packet of the own terminal has been detected, a collision of the data packet has occurred between the own terminal and another terminal. However, since the other terminal is scheduled to change the data packet transmission timing, the transmission prohibition period setting unit 15 cancels the transmission prohibition period in consideration that the other terminal changes the data packet transmission timing.

  That is, while the other terminal changes the data packet transmission timing, the own terminal maintains the data packet transmission timing, thereby avoiding the collision of the data packet between the own terminal and the other terminal. For example, as illustrated in FIG. 5, when the terminal F detects a collision detection packet in the “signal reception process” state, the terminal F cancels the setting of the transmission prohibition period. Then, this routine is finished, and a transition is made to a reception standby state.

(Collision detection packet transmission processing)
FIG. 9 is a flowchart showing a processing routine of “collision detection packet transmission processing”. In step S31, the transmission prohibition period setting unit 15 determines based on the detection result of the packet detection unit 13 whether the reception of the data packet of another terminal is successful. Here, “successfully receiving a data packet” means a state in which one data packet is detected at a predetermined timing. If the determination is affirmative, the process proceeds to step S32. If the determination is negative, the process proceeds to step S33.

  In step S32, the transmission prohibition period setting unit 15 sets the transmission schedule timing of the next data packet of the other terminal to the transmission prohibition period. Thereby, it is possible to prevent the own terminal from transmitting at the scheduled transmission timing of the next data packet of the other terminal.

  For example, as shown in FIG. 5, when the terminals A and E succeed in receiving the data packet of the other terminals, the terminals A and E set the received timing to the transmission prohibited period. Thereby, since the terminals A and E are set not to transmit the data packet of the own terminal at the reception timing of the data packet of the other terminal, collision of the data packet can be avoided.

  On the other hand, in step S33, the collision detection packet generator 17 generates a collision detection packet, the transmission circuit 19 transmits the generated collision detection packet to each terminal, and the process proceeds to step S34. For example, as illustrated in FIG. 5, the terminal C generates a collision detection packet and transmits the collision detection packet to the terminals B, D, and F.

  In step S34, the transmission prohibition period setting unit 15 cancels the setting of the transmission prohibition period. Here, since it is considered that another terminal changes the data packet transmission timing, only the setting of the transmission prohibition period of its own terminal is canceled. When this routine ends, the process shifts to a reception standby state.

As described above, according to FIG. 5, when the data packets transmitted from the terminals B and D collide at the terminal C, only the terminal C transmits the collision detection packet to the terminals B, D, and F. The collision detection packet is received by terminals B and D. However, since the terminal B has not received the collision detection packet within a predetermined period ( _Tcollect ) after the transmission of the data packet, the terminal B sets the transmission prohibition period until the timing after the basic period.

On the other hand, since the terminal D has received the collision detection packet within a predetermined period ( _Tcollect ) after the transmission of the data packet, the terminal D sets the transmission prohibition period to change the next transmission timing after the basic period. As a result, the transmission timings of the next data packets of the terminals B and D become different, and it is avoided that data packets collide continuously.

  On the other hand, when the terminals A and E normally receive the data packet, the terminals A and E set the timing after one basic period from the time of reception as the transmission prohibited period.

  In addition, since the terminal C has received the collision detection packet, the transmission prohibition period is canceled in order to increase the transmission opportunity, considering that the transmission timing of the data packet is changed. Since the terminal F can communicate with only the terminal C, the terminal F receives only the collision detection packet. In this case, like the terminal C, the terminal F cancels the transmission prohibition period in order to increase the transmission opportunity in consideration of the change in the transmission timing of the data packet.

  As described above, when the communication apparatus according to the embodiment of the present invention detects a collision of data packets between other terminals, the communication apparatus transmits the collision detection packet to the other terminal and cancels the transmission prohibition period of the own terminal. . Thereby, the communication apparatus can increase the transmission opportunity of the own terminal considering that the transmission timing of the data packet of the other terminal is changed. In addition, when the communication device normally receives the data packet, the communication device sets the timing to the transmission prohibition period and maintains the reception of the data packet.

  Further, when the collision detection packet is received, the communication device changes the setting timing of the transmission prohibition period of the data packet according to the reception timing of the collision detection packet. As a result, the communication device can avoid data packet collision since the transmission timing of the data packet is different when the reception timing of the collision detection packet is different.

  In this way, the communication device controls the transmission timing of the data packet of its own terminal by changing or canceling the transmission prohibition period regardless of whether or not there is a hidden terminal. Collisions can be suppressed.

  It should be noted that the present invention is not limited to the above-described embodiment, and it is needless to say that the present invention can also be applied to a design modified within the scope described in the claims.

It is a block diagram which shows the structure of the communication apparatus of the radio | wireless communication network which concerns on embodiment of this invention. It is a figure which shows the structure of the fundamental period transmitted / received by n communication apparatuses. It is a state transition diagram of this communication apparatus. It is a figure which shows the arrangement | positioning relationship of terminal AF. 7 is a timing chart showing packet transmission / reception timings of terminals A to F when data packets of terminal B and terminal D collide at terminal C. FIG. It is a flowchart which shows the process routine of a "data packet transmission process". It is a flowchart which shows the processing routine of "the collision detection packet reception process with respect to the data of the own terminal." It is a flowchart which shows the processing routine of a "signal reception process". It is a flowchart which shows the process routine of "a collision detection packet transmission process."

Explanation of symbols

12 reception circuit 13 packet detection unit 14 packet demodulation unit 15 transmission prohibition period setting unit 16 packet generation unit 17 collision detection packet generation unit 18 transmission timing control unit 19 transmission circuit

Claims (4)

A data packet transmission means for periodically transmitting data packets at a timing other than the basic transmission prohibition period;
Packet receiving means for receiving data packets from other terminals;
A collision detection packet transmission means for transmitting a collision detection packet when data other than one data packet is received by the packet reception means at a predetermined timing of the basic period;
A transmission prohibition period setting means for canceling the transmission prohibition period when data other than one data packet is received by the packet reception means at a predetermined timing of the basic period;
A communication device comprising: The transmission prohibition period control means sets a period including the reception timing of the data packet of the basic period as the transmission prohibition period when one data packet is received by the packet reception means at a predetermined timing of the basic period. The communication device according to claim 1 to set. A data packet transmission means for periodically transmitting data packets at a timing other than the basic transmission prohibition period;
A packet receiving means for receiving a collision detection packet from another terminal;
A transmission prohibition period setting means for setting the transmission prohibition period according to the reception timing of the collision detection packet by the packet reception means;
A communication device comprising: When the collision detection packet is received by the packet receiving unit within a predetermined period after the data packet is transmitted by the data packet transmitting unit, the transmission prohibition period setting unit is configured to transmit the data packet next to the basic period. When the timing is set to a transmission prohibition period and the collision detection packet is not received by the packet reception unit within a predetermined period after the transmission of the data packet by the data packet transmission unit, the basic period from the transmission of the data packet The communication apparatus according to claim 3, wherein a period until the end of the transmission is set as a transmission prohibition period.

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