JP2006020142A - Transmission controller, radio communication apparatus, and radio communication system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a transmission controller, a radio communication apparatus, and a radio communication system for avoiding packet collision at a transmission path shared by uplink and downlink directions, capable of improving throughput and reducing delay fluctuation. <P>SOLUTION: The transmission controller controls a transmission timing for an uplink direction packet or a downlink direction packet traveling in radio communication on half double transmission path. The apparatus comprises a packet type determining means for determining whether an arrived packet is a packet serviced by two-way communication or not based on a packet information of the arrived packet, and a transmission control means for transmitting either of an uplink direction packet or a downlink direction packet after holding it temporarily if the arrived packet is the packet serviced by two-way communication. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a transmission control device, a wireless communication device, and a wireless communication system, for example, a wireless communication system capable of bidirectional communication in a network using a half-duplex communication transmission path such as a wireless LAN, and the wireless communication system. It can be applied as a device that constitutes.

  In recent years, for example, as a technique for constructing the Internet or an intranet, not only conventional wired media such as copper wires and optical fibers but also construction of IP networks using wireless media has attracted attention.

  As a typical technique for constructing a wireless IP network, for example, there is a wireless LAN that realizes a communication speed of 11 Mbps to 54 Mbps using a frequency band of 2.4 GHz band or 5 GHz band.

  As a communication control method for performing packet transmission in this wireless LAN, CSMA / CA (Carrier Sense Multiple Access Collision Aviation) is widely used, and this CSMA / CA method is adopted as a MAC protocol of the IEEE 802.11 standard. ing.

  In the CSMA / CA method, before a wireless station transmits a packet, the usage status of the wireless channel (communication transmission path) is observed (carrier sense), and it is confirmed that the wireless channel is not used (not busy). This is a communication control method for transmitting packets after the transmission.

  When a wireless IP network adopting the CSMA / CA scheme is constructed, if packets are frequently transmitted and received using the same wireless channel between a wireless station and a plurality of wireless terminals, transmission packets from the plurality of wireless terminals are mutually connected. There is a characteristic that the possibility of collision increases and the throughput of the wireless channel decreases.

  In this case, the collided packet is transmitted to the radio channel again after a random waiting time elapses in the radio station or radio terminal.

  Therefore, when the wireless IP network is used for voice communication adopting VoIP (Voice Over IP), when the collided packet is a voice packet, the arrival interval at the transmission destination is not constant due to the retransmission of the voice packet. Delay fluctuation may occur, which may adversely affect the voice communication quality required for real-time communication.

Conventionally, in order to solve such a problem, as shown in Patent Document 1, a voice call is detected by detecting a load state of a wireless channel and transmitting a voice packet with higher priority than a data packet in a congested state. There is a technology to reduce the quality degradation.
JP 2004-15290 A

  However, in a wireless IP network that employs the CSMA / CA scheme, voice packet collisions occur not only with data packets transmitted by other wireless terminals as described above, but also with uplinks transmitted by the wireless terminals to wireless stations. It may also occur when the transmission timing overlaps between the direction packet and the downlink packet transmitted from the wireless station to the wireless terminal.

  In particular, when performing bi-directional communication such as VoIP and TV phone, the packet generation interval in the upstream and downstream directions is the same cycle, so once the packet transmission timing in the upstream and downstream directions overlap and a collision occurs, There was a problem that the possibility that the subsequent packets collide continuously increases.

  Therefore, the throughput of an unrelated channel due to packet collision, the occurrence of delay fluctuation in voice communication, and the deterioration of speech quality can occur.

  Therefore, in a half-duplex wireless communication system that shares a communication transmission path in the uplink direction and the downlink direction, a transmission control device, a wireless communication device, and a wireless communication that can avoid collision between the uplink packet and the downlink packet A system is needed.

  In order to solve such a problem, a transmission control apparatus according to a first aspect of the present invention provides a transmission control apparatus that controls the transmission timing of an uplink packet or a downlink packet that wirelessly communicates on a half-duplex communication transmission path. A packet type determining means for determining whether the arrival packet is a packet compatible with bidirectional communication based on packet information of the arrived packet; and (2) when the arrival packet is a packet compatible with bidirectional communication, Transmission control means for transmitting after temporarily holding either an upstream packet or a downstream packet.

  A wireless communication apparatus according to a second aspect of the present invention is a wireless communication apparatus that performs wireless communication using a half-duplex communication transmission line and controls transmission timing of an uplink packet to be transmitted. Wireless communication means for transmitting and receiving packets according to a predetermined communication control method, (2) transmission packet means for generating transmission packets, (3) generation time of transmission packets, arrival times of reception packets, and arrival intervals of reception packets And a transmission control means for controlling the transmission timing of the transmission packet.

  A wireless communication system according to a third aspect of the present invention is a half-duplex wireless communication system that shares a communication transmission path in the uplink direction and the downlink direction, and (1) one or more wireless communication apparatuses according to the second aspect of the present invention (2) One or a plurality of wireless station devices that wirelessly communicate with the wireless communication device; and (3) Control transmission timing of uplink packets and downlink packets that are wirelessly communicated between the wireless communication device and the wireless station device. And a transmission control device according to the first aspect of the present invention.

  According to the present invention, it is possible to reduce the packet collision probability between the uplink direction and the downlink direction in the radio section, so it is possible to improve the throughput of the communication transmission path (radio channel), and to improve the call quality in voice communication. Can be improved.

  The best mode for carrying out a transmission control apparatus according to the present invention will be described below with reference to the drawings.

(A) First Embodiment In the first embodiment, a voice communication network including a wireless communication network will be described. The wireless communication network in the first embodiment is a network that employs the CSMA / CA scheme.

(A-1) Configuration of First Embodiment FIG. 1 is a diagram illustrating a main overall configuration of a voice communication network according to the first embodiment.

  In FIG. 1, the voice communication network 1 of the present embodiment includes wireless terminals 101 and 102, a wireless station 103, a packet transmission control device 104, a router 105, an IP network 106, a media gateway 107, a public line network 108, a telephone terminal 109, A router 110, an IP telephone terminal 111, and a gatekeeper 112 are provided.

  The wireless terminals 101 and 102 packetize a voice signal, and implement a communication control function and a transmission control function for realizing voice communication, moving picture communication, and the like on an IP network according to a control protocol (for example, ITU-H.323, SIP, etc.) (In this embodiment, the CSMA / CA method is adopted). The wireless terminals 101 and 102 correspond to, for example, a mobile communication device (for example, a mobile phone) or a personal computer equipped with a wireless communication device (for example, a LAN card).

  A radio station (access point) 103 performs transmission control according to the CSMA / CA scheme and performs radio communication with the radio terminals 101 and 102. The wireless station 103 gives packets (uplink packets) received from the wireless terminals 101 and 102 to the packet transmission control device 104. The radio station 103 gives the packet (downlink packet) given from the packet transmission control device 104 to the radio terminals 101 and 102 via the radio channel.

  The packet transmission control device 104 changes the transmission timing of the transmission packet. When the arrived packet is a bidirectional communication-compatible packet, the packet transmission control apparatus 104 transmits the downstream packet transmission timing so that the transmission timing of the upstream packet and the downstream packet wirelessly communicate with each other does not overlap. Is to adjust. The packet transmission control device 104 may be mounted on a relay device such as the wireless station 103 or the router 105, for example. The detailed functional configuration of the packet transmission control device 104 will be described later.

  The router 105 is a relay device that connects to the IP network 106 and relays received packets toward a destination.

  The IP network 106 is a communication network according to IP (Internet Protocol). The IP network 106 can be applied to a dedicated network, a public network, a mobile communication network, or a network in which these communication networks are combined. Examples of the IP network 106 include the Internet and an intranet.

  The media gateway 107 relays received packets between the IP network 106 and the public line network 108. The media gateway 107 performs received packet relay processing by performing control protocol conversion processing, format conversion processing, and the like of received packets.

  The public line network 108 is a telephone line network that accommodates a conventional telephone terminal 109.

  The telephone terminal 109 is a conventional telephone terminal that can be connected to the public line network 108.

  The router 110 is a relay device that relays received packets between the IP network 106 and the IP telephone terminal 111.

  The IP telephone terminal 111 is a device capable of voice communication by a communication control function that enables communication according to a predetermined control protocol (for example, ITU-H.323, SIP, etc.).

  The gatekeeper 112 is connectable to the IP network 106 and performs call control related to voice communication according to a predetermined protocol.

  Next, a functional configuration included in the packet transmission control apparatus 104 will be described with reference to FIG. FIG. 2 is a functional block diagram of the packet transmission control device 104.

  As illustrated in FIG. 2, the packet transmission control apparatus 104 includes a packet analysis unit 201, a packet buffer 202, a packet measurement unit 203, a transmission determination unit 204, and a packet transmission unit 205.

  Each function of the packet transmission control device 104 is realized by a control unit (not shown) (for example, a CPU) executing a predetermined program.

  The packet analysis unit 201 analyzes the packet header, field information, and the like of the arrived packet, and determines whether the arrival packet is a bidirectional communication compatible packet and whether it is an uplink or downlink packet. Judgment.

  The packet buffer 202 temporarily holds an arrival packet (downlink packet) when the packet analysis unit 201 determines that the packet is compatible with bidirectional communication and is a downlink packet. In addition, the packet buffer 202 gives the held downlink packet to the packet transmission unit 205 in response to an instruction from the packet transmission unit 205.

  The packet measuring unit 203 measures the arrival time of the arrived packet when the packet analyzing unit 201 determines that it is compatible with bidirectional communication. That is, the packet measuring unit 203 measures the arrival time for both the uplink packet and the downlink packet if the arrival packet is compatible with bidirectional communication. Further, the packet measuring unit 203 measures the arrival interval time (average arrival interval time) of the uplink packet by measuring the arrival time of the arriving uplink packet. This is because the upstream packet has a feature that the occurrence interval of the incoming upstream packet is constant, and the interval time can be measured by sequentially measuring the incoming upstream packet.

  The transmission determination unit 204 receives the measurement result from the packet measurement unit 203 and obtains a buffer retention time for holding the downlink packet in the packet buffer 202 based on the measurement result. The transmission determination unit 204 manages the transmission timing of the downlink packet held in the packet buffer 202 based on the buffer retention time. That is, the transmission determination unit 204 gives a transmission instruction to the packet transmission unit 205 when the buffer retention time is reached, and transmits the downlink packet held in the packet buffer 202.

  In this way, the downlink packet is held in the packet buffer 202 for the buffer retention time obtained by the transmission determination unit 204, thereby avoiding the collision between the uplink packet and the downlink packet in the wireless section (wireless channel). be able to.

  Here, a method for calculating the buffer stop time by the transmission determination unit 204 will be described.

  The transmission determination unit 204 receives the arrival time Tup of the uplink packet, the arrival time Tdown of the downlink packet, and the arrival interval time (average arrival interval time) Tint of the uplink packet from the packet measurement unit 203.

  Then, the transmission determination unit 204 obtains the downlink packet holding time Tbuff according to the following equation (1).

Tbuff = Tint / 2− | Tup−Tdown | (1)
As shown in the above equation (1), the buffer holding time Tbuff is the absolute difference between the upstream packet arrival time Tup and the downstream packet arrival time Tdown from the half of the upstream packet arrival interval time Tint. The point in time when the difference between the values is matched is shown.

  The packet transmission unit 205 is a communication unit that transmits an arrived packet. When the arrival packet is not a bidirectional communication compatible packet, the packet transmission unit 205 transmits the packet to the wireless station 103 or the router 105. In addition, when the arrival packet is compatible with bidirectional communication and is a downlink packet, the packet transmission unit 205 receives a transmission instruction from the transmission determination unit 204, reads the downlink packet from the packet buffer 202, and reads the read downlink packet. A direction packet is transmitted to the radio station 103. Further, the packet transmission unit 205 transmits the uplink packet to the router 105 after the arrival time of the packet is measured when the arrival packet is compatible with bidirectional communication and is an uplink packet.

(A-2) Operation of the First Embodiment Next, the operation of the voice communication network 1 including the packet transmission control device 104 of the first embodiment will be described with reference to the drawings.

  In the following, a case where voice communication is performed between the wireless terminal 101 and the IP telephone terminal 111 in the voice communication network 1 shown in FIG. 1 will be described as an example.

  Voice communication between the wireless terminal 101 and the IP telephone terminal 111 is performed according to a predetermined communication control protocol (for example, ITU-H.323 or SIP). In addition, the wireless terminal 101 performs a session with the IP telephone terminal 111 that is the counterpart through predetermined call processing by the gatekeeper 112, but details of the connection sequence at this time are omitted.

  When the wireless terminal 101 starts a session with the IP telephone terminal 111, packet transmission / reception is performed between the wireless terminal 101 and the wireless station 103 by wireless communication. The wireless terminal 101 performs access control with the wireless station 103 by the CSMA / CA method.

  The relationship of the transmission interval between the uplink packet and the downlink packet transmitted / received between the wireless station 103 and the wireless terminal 101 at this time will be described with reference to FIG.

  FIG. 3 shows a case where the packet transmission control device 104 has not changed the transmission timing of the downlink packet.

  As shown in FIG. 3, access control is performed between the radio station 103 and the radio terminal 101 by the CSMA / CA scheme, but the transmission timings of the uplink packet and the downlink packet may overlap.

  This is a scheme in which the CSMA / CA scheme avoids collision with other packets by transmitting packets after a random time called back-off after observing the usage status of the radio channel, but the random selected If the times are the same, packet collisions may not be avoided. That is, the state in which the transmission timings overlap indicates that the collision probability between the uplink packet and the downlink packet is high.

  Thus, in the present embodiment, the packet transmission control device 104 changes the transmission timing of the downlink packet, and the downlink packet with the changed transmission timing is given to the wireless station 103 to perform wireless communication, thereby reducing this collision probability. I tried to do it.

  FIG. 4 is a flowchart showing the operation of the packet transmission control device 104.

  When a packet arrives at the packet transmission control device 104, the received packet is given to the packet analysis unit 201. The packet analysis unit 201 analyzes the packet header, field information, and the like of the received packet, and determines the packet type (S401).

  If the packet analysis unit 201 determines that the received packet is not a bidirectional communication compatible packet, the received packet is transmitted to the wireless station 103 or the router 105 as it is (S402, S409).

  On the other hand, when the packet analysis unit 201 determines that the received packet is a packet compatible with bidirectional communication, it is determined whether the received packet is an uplink packet or a downlink packet (S403).

  When the received packet is an uplink packet, the arrival time of the received packet is measured by the packet measuring unit 203 (S404).

  Further, due to the feature that the packet occurrence interval is constant for the voice packet, the packet measurement unit 203 measures the arrival interval time of the uplink packet from the arrival time of the continuously received uplink packet (S405).

  When the arrival time and arrival interval time of the uplink packet are measured, the uplink packet is transmitted to the router 105 (S409).

  When the received packet is a downlink packet, the arrival time of the received packet is measured by the packet measuring unit 203 (S406).

  When the arrival time of the downlink packet is measured, the downlink packet is held by the packet buffer 202 (S407).

  The measurement result measured by the packet measuring unit 203 is given to the transmission determining unit 204. The transmission determining unit 204 obtains the buffer retention time Tbuff, and whether or not the current time is a time corresponding to the buffer retention time Tbuff. Is determined (S408).

When the transmission determination unit 204 determines that the current time is a time corresponding to the buffer stop time, a transmission instruction is given to the packet transmission unit 205. Upon receiving the transmission instruction, the packet transmission unit 205 reads the downlink packet from the packet buffer 202 and transmits the packet to the wireless station 103 (S409).
If it is determined that the current time is not the time corresponding to the buffer stop time, the downlink packet is held in the packet buffer 202 until the transmission timing comes (S408).

  Thus, the downlink packet whose transmission timing is adjusted by the packet transmission control device 104 is given to the wireless station 103 and given to the wireless terminal 101 by wireless communication.

  At this time, the relationship of the transmission interval between the uplink packet and the downlink packet is shown in FIG. As shown in FIG. 5, since the downlink packet given from the radio station 103 to the radio terminal 101 is delayed by the buffer transmission time Tbuff by the packet transmission control device 104, collision with the uplink packet is avoided.

(A-3) Effect of First Embodiment As described above, according to the present embodiment, the packet transmission control apparatus 104 sets the transmission timing of the downlink packet transmitted in the radio section to half of the uplink packet arrival period. By changing, it becomes possible to reduce the packet collision probability in the radio section, and it is possible to improve the throughput.

  Further, according to the present embodiment, even when another data packet is transmitted in the wireless section, by changing the transmission timing of the downstream packet, both the upstream and downstream packets are simultaneously transmitted. Since the probability of waiting can be reduced, delay fluctuation due to waiting can be minimized.

(B) Second Embodiment The second embodiment is also applied to the voice communication network of FIG. 1 described in the first embodiment.

  In the second embodiment, when a plurality of wireless terminals transmit an uplink packet to a wireless station, each wireless terminal controls the transmission timing of the uplink packet, and the packet transmission control device transmits the downlink packet. Application in the case of controlling timing will be described.

(B-1) Configuration of Second Embodiment The configuration of the voice communication network of the second embodiment corresponds to the network configuration described in FIG. The second embodiment differs from the first embodiment in the functions of the wireless terminals 101 and 102 and the function of the packet transmission control device 104. Therefore, in the following, functions different from the first embodiment will be described in detail.

  FIG. 6 is a functional block diagram illustrating the internal functions of the wireless terminals 101 and 102. As illustrated in FIG. 6, the wireless terminal includes an antenna 601, a wireless reception unit 602, a packet measurement unit 603, a speech decoding unit 604, a speaker 605, a microphone 606, a speech encoding unit 607, a packet buffer 608, a transmission determination unit 609, A wireless transmission unit 610 is provided.

  The antenna 601 captures a radio signal and gives it to the radio reception unit 602. The antenna 601 transmits a radio signal from the radio transmission unit 610.

  The wireless receiving unit 602 receives a wireless signal from the antenna 601, extracts a voice packet, and gives it to the packet measuring unit 603.

  The packet measurement unit 603 receives a radio signal from the radio reception unit 603 and measures the arrival time of the radio signal. The packet measuring unit 603 obtains the number of sessions performed through the gatekeeper 112 and the average transmission interval time of the reference session from the packet header of the received packet. Further, the packet measuring unit 603 gives the transmission determining unit 609 the measured arrival time of the received packet, the acquired number of sessions, and the average transmission interval time of the reference session. Here, the reference number of sessions refers to one determined session among a plurality of sessions.

  The voice decoding unit 604 receives the received packet measured by the packet measuring unit 603 and decodes the received packet according to a predetermined encoding / decoding method. The audio signal encoding / decoding method is not particularly limited and can be widely applied.

  The speaker 605 receives the audio signal decoded by the audio decoding unit 604 and outputs it as audio.

  The microphone 606 captures the voice uttered by the user and gives it to the voice encoding unit 607 as a voice signal.

  The audio encoding unit 607 receives an audio signal from the microphone 606, encodes the audio signal according to a predetermined encoding / decoding method, and packetizes the audio signal. The voice encoding unit 607 gives the generated packet to the packet buffer 608. Here, the packet generation time Tsnd is defined as the packet generation time generated by the speech encoding unit 607.

  The packet buffer 608 temporarily holds the packet received from the audio encoding unit 607. Further, the packet held in the packet buffer 608 is read by the transmission determination unit 609.

  The transmission determination unit 609 receives the arrival time of the received packet, the average transmission interval time of the reference session, and the number of sessions from the packet measurement unit 603, receives the packet generation time of the packet generated by the speech encoding unit 607, It is for seeking time. The transmission determination unit 609 manages the transmission timing of the uplink packet held in the packet buffer 608 based on the buffer stop time. That is, the transmission determination unit 609 reads the uplink packet from the packet buffer 608 when the buffer retention time is reached, and gives the read uplink packet to the wireless transmission unit 610.

  Here, a method for calculating the buffer stop time of the uplink packet by the transmission determination unit 609 will be described.

  The transmission determination unit 609 receives the arrival time Trcv of the received packet, the average transmission interval time Tint of the reference session, and the number of sessions m from the packet measurement unit 603. Also, the transmission determination unit 609 receives the packet generation time Tsnd of the packet generated by the speech encoding unit 607.

  Then, the transmission determination unit 609 obtains the uplink packet holding time Tbuff according to the following equation (2).

Tbuff = Tint / 2m- (Trcv-Tsnd) (2)
The wireless transmission unit 610 receives a transmission packet (uplink packet) from the transmission determination unit 609 and transmits the transmission packet via an antenna.

(B-2) Operation of Second Embodiment Next, the operation of the transmission control apparatus according to the second embodiment will be described with reference to the drawings.

  In the following, in FIG. 1, the wireless terminal 101 starts a voice call session with the IP telephone terminal 111 via the call processing of the gatekeeper 102, and the wireless terminal 102 receives the telephone terminal via the call processing of the gatekeeper 102. The operation when starting a voice call session with 109 will be described.

  FIG. 7 is a diagram illustrating the state of the transmission packet interval between the wireless station 103 and the wireless terminals 101 and 102. It is assumed that the voice call of the wireless terminal 101 is session # 0 and the voice call of the wireless terminal 102 is session # 1.

  In FIG. 7, the transmission timings of the uplink packet and the downlink packet between the wireless station 103 and the wireless terminals 101 and 102 are overlapped, and the state where the probability of packet collision is increased is shown.

  Therefore, in this embodiment, the packet transmission control apparatus 104 reduces the collision probability by changing the packet transmission timing in the downlink direction.

  First, the operation of the packet transmission control apparatus 104 will be described using the flow of FIG.

Steps S801 to S803 are the same as in the first embodiment (S401 to S403 in FIG. 4), and only downstream packets are detected from the arrived packets.

The number of voice call sessions currently used is calculated from the downstream packet detected in S803. Here, the detected number of sessions is m. (S804)
At this time, the reference session # 0 is determined from the m sessions. Here, the voice packet of the wireless terminal 101 is assumed to be session # 0.

  Next, it is determined whether or not the arrived downlink packet belongs to session # 0. If it is session # 0, arrival time T0 is measured (S805 and S806).

By measuring the arrival times of a plurality of packets of session # 0, the average arrival interval time Tint of the packets of session # 0 can be measured. (S807)
The packet of session # 0 in the downlink direction for which measurement has been completed is transmitted to radio station 103 as it is.

On the other hand, for packets other than the reference session # 0, the arrival time Tn is measured for each session. (S808)
The measured packet is temporarily held in the packet buffer 202, and the transmission determination unit 204 determines the timing of reading from the buffer. (S809)
The timing of reading from this buffer is determined by the following equation (3): Tbuff = Tint / m * n− (T0−Tn) (3)
Here, when the number of sessions is m = 2 and the arrival time Tn is session # 1 (n = 1) of the wireless terminal 102, the packet of session # 0 is transmitted at the timing when the packet of session # 1 is transmitted. After a time of Tint / 2 has passed.

  With the above operation, the packet transmission control apparatus 104 can make the transmission intervals of the downlink voice packets of a plurality of sessions constant.

  Next, operations in the wireless terminals 101 and 102 will be described with reference to FIG. FIG. 9 is a flowchart showing the operation of the wireless terminal.

  In FIG. 9, the downlink packet from the radio station 103 is given to the radio reception unit 602 via the antenna 601 (S901).

  The received packet received by the wireless reception unit 602 is given to the packet measurement unit 603, and the arrival time Trcv is measured by the packet measurement unit 603 (S902).

  At this time, the packet measurement unit 603 detects the number m of sessions of the current voice call and the average transmission interval time Tint for the session # 0 (reference session) from the control packet from the wireless station 103 (S903). ).

  The downlink packet whose arrival time is measured is given to the voice decoding unit 604 and decoded by the voice decoding unit 604. The decoded sound is reproduced by the speaker 605 (S904).

  On the other hand, the voice input from the microphone 606 is given to the voice encoding unit 607 and is voiced by the voice encoding unit 607. At this time, the generation time Tsnd of the packet generated by the speech encoding unit 607 is measured (S905, S906).

  The generated uplink packet (transmission packet) is given to the packet buffer 608 and temporarily held (S907). The uplink packet held in the packet buffer 608 is held in the packet buffer 608 until it is read from the transmission determination unit 609.

  The transmission determination unit 609 substitutes the arrival time Trcv of the downlink packet (reception packet), the average transmission interval time Tint of the reference session, the number of sessions m, and the generation time Tsnd of the uplink packet (transmission packet) into the above equation (2). By doing so, the buffer stop time Tbuff is calculated.

  Here, when the number of sessions is m = 2, the packet transmission timing is after the time Tint / 4 has elapsed from the time Trcv when the downstream packet arrived.

  At this time, the relationship between the transmission intervals of the uplink packet and the downlink packet is shown in FIG. As shown in FIG. 10, in the wireless terminals 101 and 102, the uplink packets are transmitted with a period of ¼ period shifted from the arrival interval time of the downlink packets, so the collision between the uplink packets and the downlink packets occurs. Is avoided.

(B-3) Effect of Second Embodiment As described above, according to the present embodiment, when a plurality of wireless terminals perform wireless communication, the packet transmission control device 104 is based on the packet occurrence interval of the reference session. Thus, by changing the packet transmission timing in the downlink direction for a plurality of sessions, the packet collision probability in the downlink radio section can be reduced.

  In addition, according to the present embodiment, since the wireless terminal changes the packet transmission timing in the uplink direction following the packet arrival timing in the downlink direction, the interval at which packets are transmitted in the wireless section is smoothed In addition, it is possible to reduce the packet collision probability in the wireless section, and to improve the wireless channel throughput.

(C) Third Embodiment The third embodiment is composed of a plurality of radio stations, and relays packets between adjacent radio stations, thereby enabling communication between radio stations and radio terminals that do not reach radio waves directly. A case where the present invention is applied to a realized multi-hop network will be described.

  Note that the voice communication network of FIG. 1 may include a multi-hop network.

(C-1) Configuration of Third Embodiment FIG. 11 is a configuration diagram showing a configuration image of a multihop network of the third embodiment.

  In FIG. 11, the multi-hop network according to the present embodiment includes wireless terminals 1101 and 1102, wireless stations 1103 to 1105, and a packet transmission control device 1106.

  Since the wireless terminals 1101 and 1102 correspond to the wireless terminals 101 and 102 described in the first embodiment, detailed description thereof is omitted.

  The wireless stations 1103 to 1105 are wireless network devices having a wireless LAN control function, and for example, devices (for example, access points) that can be installed in structures such as buildings and utility poles can be applied. Further, the wireless terminals 1103 to 1105 can be applied to a mobile communication terminal such as a mobile phone or a wireless communication terminal such as a personal computer as long as it has a wireless LAN control function.

  The wireless stations 1103 to 1105 may have a topology analysis function for wirelessly communicating information with peripheral wireless stations and analyzing a network configuration, a route search function, a relay function, and the like.

  The wireless station 1105 can be connected to the IP network 106 via the packet transmission control device 1106.

  The packet transmission control device 1106 changes the transmission timing of the downlink packet.

  FIG. 15 is a functional block diagram illustrating the internal functions of the packet transmission control apparatus 1106. As illustrated in FIG. 15, the packet transmission control apparatus 1106 includes a packet analysis unit 1501, a packet buffer 1502, a transmission determination unit 1503, and a packet transmission unit 1504.

  The packet analysis unit 1501, the packet buffer 1502, and the packet transmission unit 1504 correspond to the functional configuration described in the first embodiment.

  The transmission determination unit 1503 receives the analysis result from the packet analysis unit 1501 and determines the transmission timing of the downlink packet held in the packet buffer 1502.

  That is, after confirming that the uplink packet has arrived, the transmission determination unit 1503 gives a transmission instruction to the packet transmission unit 1504 to transmit the downlink packet held in the packet buffer 1502.

  In this embodiment, the packet transmission control apparatus 1106 may have the functional configuration described in the first embodiment (see FIG. 2). In this case, the packet transmission control apparatus 1106 may set the downlink packet transmission timing to half of the uplink packet arrival period. In this case, if the sum of the relay delay times Tdel at the respective radio stations is larger than half of the uplink packet arrival period, it collides with the uplink voice packet transmitted at the next timing in the radio section. there is a possibility.

(C-2) Operation of Third Embodiment FIG. 12 shows a state in which multihop communication is performed between the wireless stations 1103 to 1105 and the wireless terminal 1101.

  FIG. 12A shows a state in which an uplink packet transmitted from the wireless terminal 1101 is relayed from the wireless station 1103 to the wireless station 1104 to the wireless station 1105, and FIG. The transmitted packet in the downstream direction is relayed from the wireless station 1104 to the wireless station 1103 to the wireless terminal 1101.

  As shown in FIG. 12A, when an uplink packet passes through each of the radio stations 1103 to 1105, a relay delay Tdel due to packet buffering or carrier sense time occurs.

  12A and 12B, the transmission timing of the uplink packet and the downlink packet overlap in the radio section between the radio station 1103 and the radio station 1104, and therefore there is a possibility of packet collision. I understand that there is.

  Therefore, in this embodiment, the packet transmission control apparatus 1106 reduces this collision probability by changing the packet transmission timing in the downlink direction.

  FIG. 13 is a flowchart showing the operation of the packet transmission control apparatus 1106.

  In FIG. 13, S1301 to S1303 correspond to the operation of the first embodiment, and thus detailed description thereof is omitted.

  When a downstream packet is detected in S1303, the downstream packet is temporarily held in the packet buffer 1502 (S1304).

  Further, when the downlink packet is held in the packet buffer 1502, the transmission determination unit 1503 determines the transmission timing. The timing of reading out from this buffer is whether or not an uplink packet has arrived. When the packet arrives, the downlink packet is immediately transmitted (S1305, S1306).

  At this time, the relationship of the transmission interval between the uplink packet and the downlink packet is shown in FIG. As shown in FIG. 14, since the downlink packet is transmitted after the arrival of the uplink packet, the uplink packet and the downlink packet are relayed without crossing in the wireless section relayed by multihop. Can do.

(C-3) Effects of the Third Embodiment As described above, according to the present embodiment, the packet transmission timing in the downlink direction is controlled and the packet arrives in the uplink direction in the multi-hop network composed of a plurality of radio stations. By immediately transmitting a downlink packet, it is possible to reduce the packet collision probability in a wireless section relayed in multihop.

(D) Fourth Embodiment The network configuration of the fourth embodiment is that of the multihop network described in the third embodiment.

(D-1) Configuration of the Fourth Embodiment FIG. 16 is a functional block diagram showing the internal configuration of the packet transmission control apparatus 1106 of the fourth embodiment.

  As shown in FIG. 16, a packet analysis unit 1601, a packet buffer 1602, a packet measurement unit 1603, a transmission determination unit 1604, a packet transmission unit 1605, and a control packet generation unit 1606 are provided.

  Since the packet analysis unit 1601, the packet buffer 1602, the packet measurement unit 1603, the transmission determination unit 1604, and the packet transmission unit 1605 correspond to the functional configuration described in the first embodiment, detailed description thereof is omitted.

  The control packet generator 1606 generates a control packet for collecting load information for wireless communication with each of the wireless stations 1103 to 1105.

(D-2) Operation of the Fourth Embodiment FIG. 17 is a flowchart showing the operation of the packet transmission control device 1106 of this embodiment.

  In this embodiment, the packet transmission control device 1106 measures the load information of the radio stations 1103 to 1105 and controls the packet transmission timing in the downlink direction, thereby reducing the packet collision probability in the high-load radio station. It is aimed.

  In FIG. 17, S1601 to S1605 correspond to the operation of the second embodiment, and a detailed description thereof will be omitted.

  The packet transmission control device 1106 periodically transmits control packets to each wireless station using the control packet generation unit 1506, so that the relay delay to each wireless station, the packet collision frequency at each wireless station, and the relay packet are transmitted. Load information such as number can be measured.

  When the downlink packet received by the packet transmission control device 1106 is a control packet, the wireless station with the lowest load is detected from the wireless station configuring the multi-hop network from the packet message (S1606). , S1607).

  At this time, the delay time Tdel required for relaying packets from the packet transmission control apparatus 1106 to the low-load radio station is also measured (S1608).

  On the other hand, the time Tn when the packet in the downlink direction arrives at the packet transmission control device 1106 is measured, and is temporarily held in the packet buffer 202 (S1609, S1610).

  The timing for reading from this buffer is determined by the following equation (4).

Tbuff = Tint−Tdel− (T0−Tn) (4)
This value means that the wireless section where the downstream packet and the upstream packet intersect is set as the wireless section of the low-load wireless station. By changing the packet transmission timing in the downlink direction, it is possible to reduce the probability of packet collision caused by the intersection of the uplink and downlink packets in the high load radio station.

  As in the second embodiment, the packet transmission timing in the downlink direction is smoothed in the downlink packet transmission timing of a plurality of sessions, and the uplink packet transmission timing is changed following the downlink packet. Techniques may be applied. In this case, the average collision probability of all multi-hop wireless sections can be reduced.

(D-3) Effect of Fourth Embodiment As described above, according to the present embodiment, a low-load radio is achieved by changing the packet transmission timing in the downlink direction in a multi-hop network composed of a plurality of radio stations. By making the upstream packet and the downstream packet intersect at the station, it is possible to reduce the packet collision probability at the high-load radio station.

  Further, according to the present embodiment, the packet transmission timing in the downlink direction of a plurality of sessions is smoothed, and the packet transmission timing in the uplink direction is changed following the packet in the downlink direction. The average collision probability can be reduced.

(E) Other Embodiments (E-1) In the first to fourth embodiments described above, for convenience of explanation, the network configuration as shown in FIG. 1 is used. The network configuration is not particularly limited as long as the overlapping of direction packets can be adjusted.

(E-2) In the first to fourth embodiments described above, the application in the case where both the uplink packet and the downlink packet are voice packets has been described. However, the uplink and downlink packets on the same radio channel are described. The packet type is not particularly limited as long as the collision can be avoided. Therefore, for example, in a data communication network, a packet that is wirelessly communicated can be applied to a data packet.

1 is an overall configuration diagram of a voice communication network according to a first embodiment. It is a functional block diagram which shows the internal function of the packet transmission control apparatus of 1st Embodiment. In 1st Embodiment, it is explanatory drawing explaining the relationship of the transmission interval of an uplink packet and a downlink packet. It is an operation | movement flowchart of the packet transmission control apparatus of 1st Embodiment. In 1st Embodiment, it is explanatory drawing explaining the relationship of the transmission interval of an uplink packet and a downlink packet. It is a functional block diagram which shows the internal function of the radio | wireless terminal of 2nd Embodiment. In 2nd Embodiment, it is explanatory drawing explaining the relationship of the transmission interval of an uplink packet and a downlink packet. It is an operation | movement flowchart of the packet transmission control apparatus of 2nd Embodiment. It is an operation | movement flowchart of the radio | wireless terminal of 2nd Embodiment. In 2nd Embodiment, it is explanatory drawing explaining the relationship of the transmission interval of an uplink packet and a downlink packet. It is a block diagram explaining the structural example of the multihop network of 3rd Embodiment. In 3rd Embodiment, it is explanatory drawing explaining the relationship of the transmission interval of an uplink packet and a downlink packet. It is an operation | movement flowchart of the packet transmission control apparatus of 3rd Embodiment. In 3rd Embodiment, it is explanatory drawing explaining the relationship of the transmission interval of an uplink packet and a downlink packet. It is a functional block diagram which shows the internal function of the packet transmission control apparatus of 3rd Embodiment. It is a functional block diagram which shows the internal function of the packet transmission control apparatus of 4th Embodiment. It is an operation | movement flowchart of the packet transmission control apparatus of 4th Embodiment.

Explanation of symbols

1 ... voice communication network,
101, 102, 1101 and 1102 ... wireless terminals,
103, 1103, 1104 and 1105 ... wireless stations,
104, 1106 ... packet transmission control device,
201, 1501 and 1601 ... Packet analysis unit,
202, 1502 and 1602 ... packet buffers,
203 and 1603 ... packet measuring unit,
204, 1503 and 1604 ... transmission determination unit,
205, 1504 and 1605 ... packet transmission unit,
1606: Control packet generator.

Claims (8)

In a transmission control device that controls the transmission timing of an uplink packet or a downlink packet that wirelessly communicates over a half-duplex communication transmission path,
A packet type determination means for determining whether the arrival packet is a packet compatible with bidirectional communication based on the packet information of the arrived packet;
When the arrival packet is a bidirectional communication compatible packet, a transmission control device comprising: a transmission control means for transmitting after temporarily holding either an uplink packet or a downlink packet.   2. The transmission control apparatus according to claim 1, wherein the transmission control means transmits the downlink packet with a time point within the arrival interval of the uplink packet as transmission timing of the downlink packet.   The transmission control means transmits the time point within the arrival interval of the uplink packet of the reference session selected from the plurality of sessions as the transmission timing of the downlink packet of the reference session, and the downlink packet of each session. The transmission control apparatus according to claim 1, wherein the transmission timing is a predetermined time after the transmission timing of the downlink packet of the reference session.   4. The transmission control apparatus according to claim 1, wherein the transmission control means controls the arrival timing of the downlink packet and changes the transmission timing of the uplink packet.   The transmission control apparatus according to claim 1, wherein the transmission control means transmits the downstream packet to the multihop section after arrival of the upstream packet relayed by multihop.   6. The transmission control apparatus according to claim 5, wherein the transmission control unit includes a control packet generation unit that generates a control packet for providing load information of each wireless station forming the multi-hop network. . A wireless communication device that performs wireless communication using a half-duplex communication transmission path and controls transmission timing of an uplink packet to be transmitted,
Wireless communication means for transmitting and receiving packets according to a predetermined communication control method;
A transmission packet means for generating a transmission packet;
A wireless communication apparatus comprising: a transmission control unit that controls transmission timing of a transmission packet based on a generation time of the transmission packet, an arrival time of the reception packet, and an arrival interval of the reception packet. In a half-duplex wireless communication system that shares a communication transmission path in the upstream and downstream directions,
One or more wireless communication devices according to claim 7;
One or a plurality of wireless station devices that wirelessly communicate with the wireless communication device;
The transmission control apparatus according to any one of claims 1 to 6, which controls transmission timing of an uplink packet and a downlink packet wirelessly communicated between the radio communication apparatus and the radio station apparatus. A wireless communication system.

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