JP4760306B2 - Communication device and data deletion method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To avoid collisions of access to a memory buffer and delete unnecessary packets at appropriate timings. <P>SOLUTION: In wireless communications in which management between nodes is performed using control packets, a communication apparatus 200 which transmits data to specified target nodes has a memory buffer part 212 which temporarily stores transmission packets, a packet transmission part which transmits transmission packets transmitted from the memory buffer part to the target nodes, a transmission and receiving controller 216 which controls transmitting and receiving timings for the control packets, and a packet deletion part 228 which deletes transmission packets to be deleted from the memory buffer part during transmitting or receiving the control packets if there are any transmission packets to be deleted. <P>COPYRIGHT: (C)2007,JPO&amp;INPIT

Description

  The present invention relates to a communication device and a data deletion method, for example, a communication device and a data deletion method capable of wireless communication between a plurality of nodes.

  As an example of a standard regarding a wireless network, the Institute of Electronic Engineers (IEEE) (Electrical and Electronics Engineers) 802.11, HiperLAN / 2, IEEE 802.15.3, Bluetooth, and the like can be given. The IEEE802.11 standard includes various wireless communication protocols such as the IEEE802.11a standard and the IEEE802.11b standard depending on the wireless communication method and the frequency band to be used.

  In such a known wireless communication protocol, when communication is performed between arbitrary nodes (nodes: communication terminals), it is necessary to pass through a coordinator. For example, in IEEE 802.15.3, the time allocated to each node is strictly managed by the coordinator, and data can be transmitted and received only at the timing specified by the coordinator.

  As an application of such wireless communication, ad-hoc communication that allows direct communication between nodes without using an access point (AP) has been devised. In such ad hoc communication, each node can directly and asynchronously perform wireless communication, and a group can be formed by a plurality of nodes in a communicable area.

  In the ad hoc communication, as described above, data is exchanged between nodes without using an access point. In most cases, the memory buffer used in data communication is different from the main memory of the communication terminal (or even in the same memory, in a different area), and the transmission packet is thus separated from the communication memory buffer. Are temporarily stored, and transmission processing of transmission packets from the memory buffer is sequentially performed. However, when a transmission error occurs in data for a specific node or a specific packet in the data, the data is retransmitted repeatedly, and the packet is stagnated in the memory buffer. In addition, for data that requires real-time performance, a failure due to a data transmission delay also occurs.

  In order to avoid such a problem, a technique is known in which the time for data retransmission processing is counted, a packet exceeding the retransmission processing time is discarded, and retransmission of the packet is stopped (Patent Document 1). According to such a technique, the retransmission process of a packet in which a transmission error repeatedly occurs is aborted and the process proceeds to the next packet transmission process at an early stage. Therefore, it is possible to avoid a delay caused by repeating the retransmission process indefinitely and to ensure real-time performance. It becomes possible.

JP 11-33261 A

  However, when a packet in a memory buffer is simply deleted, an access conflict may occur because the access state to the memory buffer is unknown. For example, when accessing a memory buffer to perform packet transmission processing or reception processing, interrupting and performing packet deletion processing complicates processing, such as having to wait for previous access.

  In addition, in the case of wireless communication, the radio wave propagation environment changes from moment to moment, so it is difficult to assume in advance the packet error rate as in the case of wired communication. Under these circumstances, the wireless communication system has been increasing in speed year by year. Therefore, unless the efficiency of memory buffer management is improved, a large-capacity memory is required.

  At this time, even if the memory buffer is increased in capacity so that retransmission to the destination node that cannot temporarily communicate can be repeated, packets written to the memory buffer occupy the buffer memory under the above high-speed transmission, In a system that performs ad hoc communication with a plurality of destinations, the memory utilization efficiency deteriorates. Due to this deterioration in utilization efficiency, the size of the buffer memory that can be used by a destination node with a good communication line is reduced, which may affect the communication to that destination node.

  Also, for MAC control in wireless communication, the Time Division Multiple Access (TDMA) method has been the mainstream, but the CSMA / CA (Collision Multiple Access Avidity Aidance) method is the mainstream as represented by wireless LANs these days. It is becoming. The CSMA / CA method is very effective in an autonomous distributed network because other nodes recognize packet transmission / reception and packet transmission / reception is performed.

  Thus, a transmission / reception control method such as CSMA (Collision Multiple Access) represented by Ethernet (registered trademark) is becoming mainstream in wireless communication, and this method does not schedule transmission / reception timing in advance. It can be said that this method is suitable for ad hoc communication. However, this method is not suitable for memory buffer management because it does not know when transmission / reception timing starts.

  The present invention has been made in view of the above-described problems of conventional wireless communication systems, and an object of the present invention is to avoid collision of access to a memory buffer and to delete unnecessary packets at an appropriate timing. A new and improved communication device and data deletion method are provided.

  In order to solve the above-described problem, according to an aspect of the present invention, in wireless communication in which management between nodes is performed using a control packet, a communication apparatus that transmits data to a specific destination node: A memory buffer unit for holding the packet; a packet transmission unit for transmitting a transmission packet from the memory buffer unit to the destination node; a transmission / reception control unit for controlling transmission timing of the transmission packet and transmission / reception timing of the control packet; A communication unit comprising: a packet deletion unit that deletes the transmission packet to be deleted from the memory buffer unit during transmission or reception of the control packet when there is a transmission packet to be deleted; Provided. The wireless communication may be ad hoc communication in which each node directly communicates without passing through an access point, or may be communication in which an access point performs network control between nodes.

  The control packet may be a beacon signal, RTS (Request To Send) control signal, CTS (Clear To Send) control signal, ACK (transmission complete) control signal, NACK (transmission failure) control signal, data It may be a packet that reserves a communication band. The transmission / reception control unit may be controlled by CSMA or PSMA.

  Transmission or reception of the control packet is performed by a packet transmission unit, a packet reception unit that receives a received packet from another node, and a transmission / reception control unit, and processing is separated from the memory buffer unit. Therefore, access to the memory buffer unit is not performed during transmission or reception of the control packet. According to the present invention, since the transmission packet that needs to be deleted is deleted at the above timing when the memory buffer becomes free, the access collision to the memory buffer unit can be avoided.

  The packet deletion unit has a transmission / reception table that associates a transmission packet held in the memory buffer with a destination node of the transmission packet, and deletes all transmission packets having the same destination node as the transmission packet to be deleted. You may do that.

  A transmission packet scheduled to be transmitted to the same destination node as a transmission packet that needs to be deleted due to a transmission error or the like is likely to cause a transmission error again. This is because, if a transmission error occurs due to a change in communication status such as a change in distance to the destination node, it is predicted that the same transmission error will be repeated for the time being. Therefore, the packet deletion unit can secure the free space of the memory buffer unit more quickly by deleting not only such transmission packets but also transmission packet groups having the same transmission packet and destination node.

  The transmission packet to be deleted may be a transmission packet that has not been received (timed out) by the destination node within a predetermined time.

  The packet transmission unit repeats transmission of the transmission packet until there is a response from the destination node that the transmission packet has been received (ACK). However, even if communication becomes impossible due to a change in the communication status such as a change in the distance to the destination node, it is inefficient to attempt retransmission. Therefore, it is possible to cancel the retransmission of the transmission packet of the destination node that does not respond to reception completion (ACK) within a predetermined time.

  The predetermined time may be defined by the number of transmissions or receptions of the control packet.

  The control packet is transmitted to neighboring nodes periodically, for example, once every 100 msec, and is received from other nodes. Therefore, the control packet is used not only as a transmission packet deletion timing but also as a timeout trigger.

  In the transmission / reception table, the transmission packet is further associated with the number of transmissions or receptions of the control packet, and the packet deletion unit counts the number of transmissions or receptions of the control packet for each transmission packet of the transmission / reception table, and the predetermined number of times. When reaching the above, the transmission packet may be deleted.

  The packet deletion unit counts the number of transmissions or receptions of control packets associated with each transmission packet in the transmission / reception table by counting up or counting down, and the transmission packet that reaches the predetermined number of times and the transmission packet and the destination node are the same Delete all outgoing packets. With this configuration, all transmission packets in the memory buffer unit can be managed in an integrated manner.

  The predetermined time may be defined by the number of reception error signals from the destination node.

  The packet deletion unit converts the timeout based on the reception error signal (NACK) of the destination node. With this configuration, the number of retransmissions of the transmission packet can be given uniformly to each node.

  In the transmission / reception table, the number of times of the reception error signal is further associated with the transmission packet, and the packet deletion unit counts the number of reception error signals for each transmission packet of the transmission / reception table and reaches a predetermined number of times. The transmission packet may be deleted.

  The packet deletion unit counts the number of reception error signals of the destination node associated with each transmission packet in the transmission / reception table by counting up or counting down, and the transmission packet that reaches the predetermined number of times and the transmission packet and the destination node are the same Delete all outgoing packets. With this configuration, all transmission packets in the memory buffer unit can be managed in an integrated manner.

  A class may be defined for the transmission packet, and the packet deletion unit may determine whether to delete all transmission packets having the same destination packet as the transmission packet to be deleted according to the class.

  For example, when the transmission packet is a part of data that requires real-time property, it is not necessary to transmit the transmission packet until the real-time property is sacrificed. On the other hand, there are also transmission packets that need to reach the destination node reliably even at the expense of real-time performance. The attribute of the transmission packet is defined as a class, and the range of transmission packet deletion is determined according to the definition.

  A network management unit for managing transmission packets, wherein the packet deletion unit notifies the network management unit that the transmission packet has been deleted, and the network management unit manages the transmission packet separately from the memory buffer unit; It is also possible to delete all transmission packets of the same destination node as the transmission packet to be deleted and request the packet deletion unit to delete the transmission packet again.

  A transmission packet transmitted to the same destination node as a transmission packet that no longer needs to be transmitted due to a timeout should be deleted in the upper layer, for example, the application layer. Therefore, the packet deletion unit prompts the network management unit to delete the transmission packet. However, due to the transmission delay of the deletion command, the network management unit may transmit the transmission packet to the memory buffer immediately before deleting the transmission packet. With this second deletion command, it is possible to completely delete a transmission packet that is highly likely to cause a transmission error.

  The packet deletion unit forcibly deletes the transmission packet during transmission or reception of the next control packet, regardless of the number of transmissions or receptions of the control packet, after receiving the deletion command from the network control unit It is also good. Such deletion may be performed by setting the number of transmissions or receptions to a value immediately before the predetermined number of times.

  When it becomes necessary to forcibly delete a transmission packet in the communication device, such as resetting transmission data, the packet deletion unit forcibly changes the count value of the transmission / reception table. With this configuration, the transmission packet is surely deleted at the next transmission of the control packet, and the collision of access to the memory buffer unit can be avoided.

  The memory buffer unit may be used for both transmission and reception packets. By forming the memory buffer unit as a single buffer, it is possible to effectively use the storage capacity even when the capacity of the transmitted packet and the received packet is biased with respect to each other.

  In order to solve the above problem, according to another aspect of the present invention, there is provided a communication device that transmits data to a specific destination node in wireless communication in which management between nodes is performed using a control packet: A memory buffer unit that temporarily holds a packet; a packet transmission unit that sequentially assigns a sequence number to the transmission packet from the memory buffer unit and transmits the packet to the destination node; a transmission timing of the transmission packet, and the control packet A transmission / reception control unit that controls the transmission / reception timing of the packet; a packet reception unit that receives a received packet from the destination node and determines whether the sequence number is synchronized; and the control when the sequence number is not synchronized During transmission or reception of a packet, a transmission packet related to the destination node is transferred to the memory back. A packet deletion unit for deleting from § portion; characterized in that it comprises a communication device is provided.

  The packet transmission unit assigns a sequence number, and the packet reception unit confirms the sequence number, thereby confirming whether the transmission packet is synchronized. When the synchronization is lost, the communication device resets the transmission data and forcibly deletes the transmission packet.

  In order to solve the above-described problem, according to another aspect of the present invention, a data deletion method for deleting data to be transmitted to a specific destination node is also provided as the communication device described above.

  With this configuration, unnecessary packets can be deleted at an appropriate timing without colliding access to the memory buffer unit at the transmission packet deletion timing.

  As described above, according to the communication device and the data deletion method of the present invention, it is possible to avoid collision of access to the memory buffer, delete unnecessary packets at an appropriate timing, and effectively use the storage area. Is possible.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the present specification and drawings, components having substantially the same functional configuration are denoted by the same reference numerals, and redundant description is omitted.

(First embodiment: wireless communication network)
In recent years, a wireless communication network that connects a communication device connected to a communication network such as the Internet and a communication device such as a mobile personal computer by wireless communication is becoming common. An example of a standard regarding a wireless network is the American Institute of Electronics Engineers IEEE 802.11, HiperLAN / 2, IEEE 802.15.3, Bluetooth, and the like. The IEEE802.11 standard includes various wireless communication protocols such as the IEEE802.11a standard and the IEEE802.11b standard depending on the wireless communication method and the frequency band to be used.

  The configuration of such a wireless communication network will be described in detail by taking the IEEE 802.11 as an example. In networking according to IEEE 802.11, the concept of BSS (Basic Service Set) is used. Here, a BSS defined in an infrastructure mode in which a master control station called an access point exists, and an IBSS (Independent BSS) defined in an ad hoc (Ad-hoc) mode configured only by a plurality of MTs (Mobile Terminals). And are defined. The access point is, for example, a coordinator, and MT is, for example, a node (communication terminal).

  In the BSS in the infrastructure mode, an access point for performing coordination is essential in the wireless communication network. This access point collects MTs existing in a communicable range around the access point as a BSS, and constitutes a cell in a so-called cellular system.

  The MT existing in the vicinity of the access point is accommodated in the access point, and enters the wireless communication network as one member of the BSS by the access point. The access point transmits a control signal including network management information called a beacon signal at an appropriate time interval. The MT that can receive this beacon signal recognizes that an access point exists in the vicinity, and further establishes a connection with the access point.

  FIG. 1 is an explanatory diagram for explaining the BSS defined in the infrastructure mode, and FIG. 2 is a timing chart showing the timing of the beacon signal in the BSS. In FIG. 1, the communication station STA0 is defined as an access point, and STA1 and STA2 within the communication range 100 from the STA0 are defined as MT. The STA0 transmits beacon signals at regular time intervals as shown in FIG. The next beacon signal transmission time is notified by a parameter called Target Beacon Transmit Time (TBTT) in the beacon signal, and when the time reaches the TBTT, the access point performs a beacon signal transmission procedure.

  Further, MTs (STA1 and STA2 in FIG. 1) existing in the vicinity receive the beacon signal transmitted from the access point, and decode the TBTT field written in the beacon signal to determine the next beacon transmission time. recognize. Therefore, depending on the communication situation such as when there is no need for reception, it is possible to turn off the power of the receiver and enter the sleep state next time or until the next TBTT. In this way, in the network where the coordinator exists, only the coordinator transmits a beacon, and therefore the MT in the wireless communication network also allows the TBTT from the access point to be temporarily delayed.

  Next, the operation of IEEE 802.11 in the other ad hoc mode will be described. In such ad hoc communication, communication devices (nodes) can directly and asynchronously communicate with each other under the management of the CSMA protocol. In addition, in UWB (Ultra Wide Band) communication in IEEE 802.15.3, network management is performed via an access point, and the above ad hoc communication (or mesh communication) is performed using a packet-structured data communication method using a preamble. ) Is realized.

  FIG. 3 is an explanatory diagram for explaining the IBSS defined in the ad hoc mode, and FIG. 4 is a timing chart showing the timing of the beacon signal in the IBSS. In the IBSS in the ad-hoc mode, the MTs represented by STA1 and STA2 negotiate with a plurality of MTs within its own communication range 102 and autonomously define the IBSS in each MT. This MT group defines TBTT at regular intervals shown in FIG. 3 after IBSS is defined and negotiated. When each MT recognizes that the time has reached TBTT by referring to the clock in its own station, after the random time delay (Random Backoff), other MTs in the IBSS are not transmitting a beacon signal. Confirm and transmit a beacon signal to another MT.

  In the above example, any MT belonging to the IBSS transmits a beacon signal every time the TBTT is visited. Therefore, beacon signals may collide with each other.

  Further, when all of STA0, STA1, and STA2 in FIG. 1 are defined as MTs, for example, when STA1 attempts to transmit data to STA0, STA2 exists in the vicinity of STA0, and STA2 is in one communication It is a so-called hidden terminal that can communicate with the device (STA0) but cannot communicate with the other communication device (STA1). In order to avoid the data communication being hindered by such a hidden terminal, the communication device (STA1) and the communication device (STA0) specify the transmission terminal and the reception terminal using the RTS / CTS control signal.

  FIG. 5 is a timing chart for explaining the control by the RTS / CTS control signal. Here, it is assumed that STA0, STA1, and STA2 are arranged in the positional relationship shown in FIG. At this time, when STA1 and STA2 transmit a data frame to STA0, they cannot carrier sense each other's radio waves. Therefore, there is a possibility that a data frame transmitted by one side collides. In order to avoid such a data frame collision, in the conventional MAC layer of wireless networking, as described above, an access method via the RTS control signal and the CTS control signal is provided.

  For example, referring to FIG. 5, when data is to be transmitted from STA1 to STA0, first, STA1 transmits an RTS control signal 110. The RTS control signal 110 is received by STA0 but does not reach STA2. However, when STA0 returns a CTS control signal 112 corresponding to the RTS control signal 110 to STA1, STA2 can receive the CTS control signal 112, and STA0 communicates with another station (here, STA1). Recognize that you are starting. When the STA 2 recognizes the communication of the STA 0, the STA 2 prohibits data transmission from itself for a certain period of time (NAV: Network Allocation Vector: non-transmission section) 114 in order to avoid a communication collision with the STA 0. In this way, STA1 for which the communication path is secured transmits Data 116 to STA0, and STA0 returns an ACK control signal 118 accordingly. When STA2 attempts transmission to STA0, transmission of STA1 is prohibited 120 for a certain period of time as described above. In this way, the above hidden terminal problem is solved.

  In addition to the hidden terminal problem, there is a problem that a data transmission error occurs due to an environmental change between nodes. The following is a detailed description of how to handle transmission errors.

  FIG. 6 is a timing chart showing transmission / reception timing of each node in the TDMA system. Conventionally, the TDMA system has been the mainstream as a wireless MAC (Medium Access Control) control system. In such a TDMA system, nodes (STA1, STA2) that communicate with the base station are allocated for each frame 150, and data transmission / reception between each node (STA1, STA2) and the base station is performed only within the allocated time. Is done.

  In the TDMA system, data transmission (Uplink) and reception (Downlink) to a base station are often managed by different time divisions called TDMA slots, so that data transmission and reception are performed separately. Scheduled. Therefore, it is possible to easily delete a transmission packet during data reception.

  Here, the transmission packet is deleted when a transmission error occurs in the data for a specific node or in a specific packet in the data, the data is retransmitted repeatedly, and the packet is stagnated in the memory buffer. This is to avoid that.

  For example, if the node (STA1) in FIG. 6 holds data to be transmitted to the base station and a transmission error occurs for some reason, the node (STA1) counts the time for data retransmission processing. , Abandon a transmission packet that has exceeded the retransmission processing time, and cancel retransmission of the packet. Because of such a timeout, it is possible to abort the retransmission process for a packet that repeatedly causes a transmission error and to proceed to the next packet transmission process at an early stage. Therefore, it is possible to avoid a delay caused by repeating the retransmission process indefinitely and to ensure real-time performance. It becomes possible.

  On the other hand, in the CSMA system, scheduling of transmission and reception is difficult. Therefore, as described above, the communication timing of each node is synchronized and the communication is stabilized by a beacon signal or a polling packet.

  FIG. 7 is a timing chart showing the transmission / reception timing of each node in the CSMA system. As shown in FIG. 7, in the CSMA system, nodes are synchronized with each other by a beacon signal, and a data transfer sequence is performed within the synchronization frame 152.

  Unlike the TDMA method described above, in the CSMA method, the data transmission / reception timing depends on the beacon signal timing and the RTS / CTS control signal, and it is difficult to grasp the access timing to its own memory buffer during packet transmission / reception. It is. Therefore, even when a transmission error is detected and the transmission packet stored in the memory buffer needs to be deleted, the transmission packet cannot be easily deleted because the access state to the own memory buffer is unknown.

  In wired high-speed communication such as Ethernet (registered trademark), since transmission errors are relatively small, retransmission control of transmission packets can be performed in an upper layer, for example, the TCP layer. However, in a wireless environment such as the CSMA system, the communication environment is unstable compared to wired communication, so there is a high possibility that a transmission error will occur. Even in the CSMA scheme, if high-speed communication is to be realized, it is necessary to perform packet retransmission control and deletion control in the MAC layer, for example, in terms of transmission efficiency. By overcoming such problems, not only the current communication of about 100 Mbps but also high-speed communication such as UWB and IEEE802.11n having a transfer rate of 300 Mbps to 1 Gbps, which is expected to become mainstream in the future, can be supported. Become.

  In the embodiment according to the present invention, the transmission packet is deleted at the time of transmission or reception of the control packet including the beacon signal, thereby avoiding such a collision of access to the memory buffer, and unnecessary packets at an appropriate timing. It is possible to delete.

(Second Embodiment: Communication Device)

  FIG. 8 is a block diagram illustrating a schematic configuration of the communication apparatus 200. The communication apparatus 200 includes a network management unit 210, a memory buffer unit 212, a transmission data generation unit 214, a transmission / reception control unit 216, a physical layer Tx unit 218, an antenna 220, a physical layer Rx unit 222, A layer control unit 224, a reception data control unit 226, and a packet deletion unit 228 are included.

  The network management unit 210 is an upper layer (upper layer), for example, divides transmission data generated in the application layer into transmission packets, and transfers the generated transmission packets to the memory buffer unit 212. Further, the network management unit 210 receives a received packet from the memory buffer unit 212. In addition, the network management unit 210 receives a throughput request from the application layer and performs communication line reservation and wireless channel control by QoS (Quality Of Service). The network management unit 210 may perform P2P control with the application of the destination node.

  In the throughput management based on the QoS, it is also determined how many transmission packets are transmitted per unit time, and the transmission of data is forcibly terminated to a node that is determined to be no longer communicating. You can also.

  The memory buffer unit 212 is formed of a storage medium capable of temporarily holding data, for example, SRAM, DRAM, SDRAM, DDR, SDRAM, Rambus DRAM, EEPROM, FLASH, or the like. And the transmission packet from the network management part 210 is temporarily hold | maintained according to routing information. In addition, the memory buffer unit 212 temporarily holds the received packet from the received data control unit 226 until the network management unit 210 is ready to capture it.

  It is possible to use a DPRAM (Dual port RAM) as such a storage medium, and to separate transmission / reception paths (independently equipped with a transmission / reception memory). Use a single buffer that locates in a shared address space. Therefore, a transmission packet cannot be written when a reception packet is written into a single buffer storage medium, and a reception packet cannot be input when a transmission packet is written. The storage capacity of the buffer is not particularly limited. By forming the memory buffer unit 212 as a single buffer, it is possible to effectively use the storage capacity even when there is a bias in the capacity of transmission packets and reception packets. For example, when the transmission packet uses only 30% of the storage capacity, the reception packet can use the storage capacity of up to 70%.

  The transmission data generation unit 214 obtains information such as a transmission rate from the transmission / reception control unit 216 and generates a transmission packet. The wireless system of the transmission data generation unit 214 and the reception data control unit 226 described later is not limited to the above-described system, and may be infrared, OFDM, DS-SS, FH-SS, monopulse, or the like. The transmission data generation unit 214, the physical layer Tx unit 218, and the physical layer control unit 224 form the packet transmission unit (not shown) described above. The transmission data generation unit 214 may sequentially assign sequence numbers for synchronizing transmission packets. Such a sequence number is a numerical value provided in common for managing duplicate reception of packets between the communication apparatus 200 and other nodes, and this sequence number may be used in the transmission packet transmission order.

  The transmission / reception control unit 216 controls TDMA and CSMA MAC protocols and provides the transmission data generation unit 214 with information such as a transmission rate. Further, the transmission timing of the transmission packet from the transmission data generation unit 214 and the transmission / reception timing of the control packet for controlling the communication time (timing) in the ad hoc communication are controlled, and the control timing is transmitted to the memory buffer unit 212. Further, such a control method is similar to CSMA, and may include media access control called PSMA for identifying packets by correlation of preamble instead of carrier.

  The control packet may be a beacon, an RTS control signal, a CTS control signal, an ACK (transmission completion) control signal, a NACK (transmission failure) control signal, or a packet that reserves a data communication band. .

  The physical layer Tx unit 218 receives an instruction from the physical layer control unit 224, starts operation, and outputs data from the transmission data generation unit 214 to the air via the antenna 220.

  The physical layer Rx unit 222 receives an instruction from the physical layer control unit 224, starts operation, and receives reply data (packet) from the destination node for the transmission data output from the physical layer Tx unit 218. Thereafter, the data is transferred to the reception data control unit 226. The packet receiving unit (not shown) described above is formed by the physical layer Rx unit 222, the physical layer control unit 224, and the reception data control unit 226.

  The physical layer control unit 224 receives a data transmission command from the transmission / reception control unit 216 or the transmission data generation unit 214, controls data transmission in the physical layer, and receives data from other nodes as reception data control. The data is transferred to the unit 226. Further, the physical layer Tx unit 218 is controlled for transmission, and the physical layer Rx unit 222 is controlled for reception.

  The reception data control unit 226 analyzes the reception data (packet) and recognizes information specifying the type of the received data and the distance measuring device. Further, when the transmission data generation unit 214 assigns a sequence number to each transmission packet, the reception data control unit 226 may determine whether the sequence number is synchronized. Here, when the sequence numbers are not synchronized, it is possible to request the packet deletion unit 228 described later to forcibly delete the transmission packet.

  When there is a transmission packet to be deleted, the packet deletion unit 228 detects transmission or reception of the control packet during transmission or reception of the control packet described above, and sends the transmission packet to be deleted from the memory buffer unit 212. delete. Here, the communication apparatus 200 may be able to perform only transmission or only reception regarding the control packet. A mode for performing only such transmission or reception may be provided. With this configuration, it is possible to reduce power consumption. Further, such deletion processing may be performed directly by the packet deletion unit 228 or may be performed by the memory buffer unit 212 according to an instruction from the packet deletion unit 228.

  The transmission or reception of the control packet is performed by the transmission data generation unit 214, the reception data control unit 226, and the transmission / reception control unit 216. The memory buffer unit 212 performs processing for a certain period (for example, 20 μsec in the case of a beacon). Disconnected. Therefore, access to the memory buffer unit 212 is not performed during transmission or reception of the control packet. In this embodiment, since the transmission packet to be deleted is deleted at the above timing, an access collision to the memory buffer unit 212 can be avoided. Here, the time interval by the control packet, especially the beacon is set to 20 μsec. However, this is not limited to such a case, and the time interval varies depending on the system and also in the same system depending on the operation status. Can take.

  In addition to the beacon signal, as described above, the RTS control signal, the CTS control signal, the ACK (transmission completion) control signal, the NACK (transmission failure) control signal, and the packet that reserves the data communication band are applied to the control packet. can do. Here, when the memory buffer unit 212 manages transmission and reception independently, the packet deletion unit 228 detects that a packet is received, and transmits a packet to be deleted during reception of the packet. May be deleted.

  A class may be defined for the transmission packet, and the packet deletion unit 228 may determine whether to delete all transmission packets having the same destination packet as the transmission packet to be deleted, according to the class. When the transmission packet is a part of data that requires real-time property (for example, a packet for QoS), it is not necessary to transmit the transmission packet until the real-time property is sacrificed. On the other hand, there are also transmission packets that need to reach the destination node reliably even at the expense of real-time performance. The attribute of the transmission packet is defined as a class, and the range of transmission packet deletion is determined according to the definition. With this configuration, it is possible to define an optimum deletion range according to the content of the transmission packet.

  Further, the packet deletion unit 228 notifies the network management unit 210 that the transmission packet has been deleted. The network management unit 210 is different from the memory buffer unit 212, for example, in the application layer. It is also possible to delete all transmission packets of the same destination node as the transmission packet to be transmitted, and request the packet deletion unit 228 to delete the transmission packet again.

  A transmission packet transmitted to the same destination node as a transmission packet that no longer needs to be transmitted due to a timeout should be deleted in the upper layer, for example, the application layer. Accordingly, the packet deletion unit 228 prompts the network management unit 210 to delete the transmission packet. However, due to the transmission delay of the deletion command, the transmission packet may be transmitted to the memory buffer unit 212 immediately before the network management unit 210 deletes the transmission packet. With this re-delete command, a transmission packet that causes a transmission error can be completely deleted.

  A specific operation for deleting the transmission packet held in the memory buffer unit 212 using the communication device 200 described above will be described below.

  The packet deletion unit 228 deletes, from the memory buffer unit 212, a transmission packet whose destination node has not completed reception within a predetermined time as a transmission packet that has timed out.

  The packet transmission unit (transmission data generation unit 214, physical layer Tx unit 218, physical layer control unit 224) repeats transmission of the transmission packet until there is a response of reception completion (ACK) of the transmission packet from the destination node. However, even if communication becomes impossible due to a change in the communication status such as a change in the distance to the destination node, it is inefficient to attempt retransmission. Therefore, retransmission of the transmission packet of the destination node that does not receive a reception completion (ACK) response within a predetermined time is stopped.

  In the present embodiment, the predetermined time may be defined by the number of transmissions or receptions of the control packet. The control packet is transmitted to neighboring nodes periodically, for example, once every 100 msec, and is received from other nodes. Therefore, the control packet is used not only as a transmission packet deletion timing but also as a timeout trigger.

  Further, the packet deletion unit 228 comprehensively manages the timeout, so that the transmission packet held in the memory buffer unit 212, the bucket length of the transmission packet, the destination node of the transmission packet, the control packet Has a transmission / reception table that associates the number of transmissions or receptions. Each of the above parameters may be stored in the buffer memory unit 212 in the same manner as the transmission packet, or may be stored in another storage area. It is also possible to manage the sequence numbers of transmitted packets and received packets.

  The packet deletion unit 228 counts the number of transmissions or receptions of the control packet associated with each transmission packet in the transmission / reception table by counting up or counting down, and the transmission packet that reaches the predetermined number and the transmission packet and the destination node are the same Can be deleted. With this configuration, all transmission packets in the memory buffer unit can be managed in an integrated manner. Hereinafter, the transmission packet deletion operation will be described in detail.

  FIG. 9 is an explanatory diagram schematically showing the data structure of the transmission / reception table 300. In this case, transmission packets and reception packets are mixedly stored in addresses 1 to 5 of the memory buffer unit 212, and the transmission / reception table 300 is associated with various pieces of information regarding transmission packets in particular. First, the address 302 indicates a physical or logical address of the memory buffer unit 212. The address 302 is not limited to the address of the memory buffer unit 212 but may be a management number for managing transmission packets. The type of the packet stored at the address 302 is shown in the packet 304. For example, “transmission packet 1” is stored in address 1. “Transmission packet” and “reception packet” shown in the packet 304 indicate the direction of the packet, and the numerical value at the end indicates a sequence number necessary for retransmission management.

  The contents and storage method of the transmission / reception table 300 described above are not limited, and may be managed as a single file or may be managed by being divided into predetermined file units.

  The priority order of transmission packets is set according to the access method. For example, it is possible to adapt the round robin method or to increase the total length. In the example of FIG. 9 above, when the transmission right is given to the node 2, “transmission packet 1” is first permitted to be transmitted, and when transmission is assigned to the node 3, “transmission packet 3” is the first. Is allowed to send.

  The packet length 306 indicates the length of each transmission packet in bytes, and the destination node 308 indicates the destination node name. In the present embodiment, the number of times of transmission of the control packet is described in the number of times 310, and the initial value is set to 10 and is counted down one by one for every transmission of the control packet. Of course, the initial value is not limited to 10. In the case of FIG. 9, since the number 310 of “transmission packet 1” at address 1 is 3, it can be understood that the transmission has been completed from the upper layer to the destination node for 100 msec × 7 times. . It is also understood that the remaining 300 msec can be waited.

  FIG. 10 is a timing chart for explaining the flow of control packet transmission and the change in the transmission / reception table at each time point. FIGS. 11A, B, C, and D are time points (2) and (3 in FIG. It is explanatory drawing which showed the transmission / reception table in (4), (5). In the present embodiment, it is assumed that the communication environment with the node 2 among the destination nodes is poor and the communication environment with the node 3 is relatively good.

  At the time (1) in FIG. 10, the transmission / reception table is as shown in FIG. 9, and the memory buffer unit 212 has two transmission packets for node 2, one transmission packet for node 3, and reception packet. Two are held.

  At time (2) in FIG. 10, the received packets 1 and 2 held at the addresses 2 and 3 are read to the network management unit 210, and only the transmission packet 3 to the node 3 held at the address 4 is read. Are successfully transmitted and deleted from the memory buffer unit 212, respectively. Therefore, the addresses 2 to 4 in FIG. 11A are empty. Further, since the transmission packet to the node 2 has not been transmitted due to a transmission error, it remains in the transmission / reception table. Here, since the control packet is transmitted once, the number of times 310 is decremented by one, the number of times 310 of the transmitted packet 1 is “2”, and the number of times 310 of the transmitted packet 2 is “7”. ing.

  Subsequently, at time (3) in FIG. 10, a transmission packet to the node 3 is newly added to the address 2 in response to a packet transmission command from the upper layer. Since all of the transmission packets indicated by the addresses 1, 2, and 5 have failed to be transmitted between time points (2) and (3) in FIG. 10, the count of the control packets is as shown in FIG. 11B. , “1”, “9”, “6”.

  Subsequently, the received packet 3 is added to the address 4 at time (4) in FIG. However, from the time point (3) to (4) in FIG. 10, the transmission packets indicated by the addresses 1, 2, and 5 have not been transmitted, and the count of the control packets is “ It is reduced to “0”, “8”, “5”. Here, the packet deletion unit 228 receives that the number 310 of transmission packets 1 has become “0” (has reached the predetermined number of times 10), and that the transmission packet addressed to the node 2 is stagnant. Determination is made and the transmission packet 1 is deleted. Since the destination node of the transmission packet 1 to be deleted is “node 2”, the transmission packet 2 that is the destination node is also deleted at the same time regardless of the number of times 310 (standby time). Thus, at time point (5) immediately after time point (4), as shown in FIG. 11D, addresses 1 and 5 in the transmission / reception table are emptied, and an area for holding the next packet is secured.

  A transmission packet scheduled to be transmitted to the same destination node as a transmission packet that needs to be deleted due to a transmission error or the like is likely to cause a transmission error again. This is because, if a transmission error occurs due to a change in communication status such as a change in distance to the destination node, it is predicted that the same transmission error will be repeated for the time being. Accordingly, the packet deletion unit 228 deletes not only the transmission packet that has timed out, but also the transmission packet group having the same destination packet as the transmission packet, thereby ensuring the free space in the memory buffer more quickly.

  In the above description, the number of times 310 is counted down and the predetermined time is counted, but the predetermined time can also be counted by counting up. In this case, the initial value is set to 0, and transmission packets that have reached the predetermined number of times 10 (threshold) are deleted. Here, the predetermined time is measured by counting a predetermined number of times, but if it is unified in advance as a system, it can be handled as time and can be handled as the number of transmissions and receptions. The number of times 310 substantially means time, but is defined as the number of times for simplicity of explanation. In addition, the order of countdown or countdown and deletion processing is not limited.

  In addition, here, the description has been made with only five addresses for easy understanding, but the address is not limited to this range, and more addresses can be associated according to the storage capacity of the memory buffer unit 212. Further, the present embodiment is not limited to the numerical values described above, and can take various numerical values.

  Furthermore, in this embodiment, it is also possible to forcibly instruct the packet deletion unit 228 to delete the transmission packet from the network management unit 210 which is an upper layer. When the network management unit 210 forcibly issues a deletion command to the packet deletion unit 228, the packet deletion unit 228 causes the network management unit 210 to forcibly set the number 310 of transmission packets in the transmission / reception table 300 to 1, The transmission packet is deleted. This process ensures that this transmission packet is deleted at the next control packet transmission.

(Third Embodiment: Data Deletion Method)
Subsequently, in ad hoc communication in which each communication device directly communicates without going through an access point, the detailed operation of the data deletion method for deleting data to be transmitted to a specific destination node using the communication device 200 described above is performed. explain.

  FIG. 12 is a flowchart showing the flow of the data deletion method according to the third embodiment. In this embodiment, during transmission or reception of a control packet, a transmission packet remaining in the memory buffer is deleted, and an access collision to the memory buffer unit is avoided.

  The communication device 200 transmits a beacon signal as a control packet to the transmission / reception control unit 216 in order to communicate with nodes around the communication device 200. Other nodes receive the beacon signal and exchange data between the nodes according to the signal band assigned by the beacon signal.

  The transmission / reception control unit 216 of the communication device 200 notifies the packet deletion unit 228 that the beacon signal has been asserted, and the packet deletion unit 228 can know that the beacon signal is being transmitted (S400). ). If assertion of the beacon signal is not detected, the process continues in a standby state. When the beacon signal is asserted, the transmission / reception control unit 216 transmits the beacon signal separately from the memory buffer unit 212, so that the packet deletion unit 228 can access the memory buffer unit 212 independently. . Further, although transmission of a beacon signal is mentioned here, the present invention can also be applied to a communication device that receives a beacon signal.

  When the beacon signal is asserted, the packet deletion unit 228 counts the number of control packets for all transmission packets that have not been transmitted yet (S402). In particular, here, the number of times 310 in the transmission / reception table 300 is subtracted by 1 by setting the packet standby permission time (10 control packets) set in advance by the upper layer as an initial value.

  The transmission / reception table 300 is added based on the contents of the packet when the network management unit 210 transmits the transmission packet to the memory buffer unit 212 and when the reception data control unit 226 transmits the reception packet to the memory buffer unit 212. Is done. Usually, since the beacon signal is transmitted periodically (100 msec), the timeout when the initial value is 10 is 1 sec at 100 msec × 10 times.

  Then, as a result of subtracting the number 310 of times in the transmission / reception table 300, it is determined whether there is a transmission packet whose value is 0 (S404). Here, if there is a transmission packet having the count 310 of 0, the destination node 308 of the transmission packet is extracted (S406). Then, the transmission packet and all transmission packets having the same destination node as the transmission packet are deleted (S408).

  In this step (S408), the transmission packet is deleted. However, the present invention is not limited to this. The transmission packet deletion information is transmitted to the network management unit 210, and the network management unit 210 subsequently transmits the transmission packet to be enqueued. It is also possible to limit the amount.

  Next, the packet deletion unit 228 notifies the network management unit 210 that the transmission packet has been deleted, and the network management unit 210 transmits the transmission packet of the same destination node as the transmission packet to be deleted managed in the application layer, for example. Are all deleted (S410). Then, the network management unit 210 requests the packet deletion unit 228 to delete the transmission packet again, and accordingly, the packet deletion unit 228 again deletes the transmission packet having the same destination node (S412). By such re-deletion processing, a transmission packet that causes a transmission error can be completely deleted.

  In such a configuration, access to the memory buffer unit does not collide at the transmission packet deletion timing, and unnecessary packets can be deleted at an appropriate timing.

  FIG. 13 is a flowchart illustrating in detail the carrier sense when the beacon signal is asserted (S400). First, the transmission / reception control unit 216 counts 100 msec for a certain period, and when the scheduled transmission time of the beacon signal arrives (S450), whether a packet exists on the air, that is, a node that forms the ad hoc communication It is confirmed whether data exchange is performed between them (S452). As a packet detection method at this time, a carrier sense or a preamble sense that grasps the existence of a packet by correlation with a known pattern can be considered.

  FIG. 14 is an explanatory diagram showing the Frame format. As described above, the Frame includes a preamble part, a heading part, and a payload part, and a known symbol pattern is defined in the preamble part according to the standard. The heading section includes such a frame type (for example, RTS control signal), a group identifier for specifying a network group for communication, an address indicating a delivery destination, an address indicating a transmission source (own address), control information, and the like. The payload part consists of network synchronization information, unique information elements such as device attributes and capabilities, time information used by itself for communication, data used in the application layer, etc. It is comprised including.

  For example, as described above, a packet in wireless communication is formed of a preamble part, a heading part, and a payload part, and detects the presence of the packet by detecting the preamble part. The preamble and header may be generated by the transmission data generation unit 214 or the physical layer Tx unit 218.

  If it is determined in the packet existence confirmation (S452) that the packet exists on the air, the data transmission is stopped for a certain period of time (during the above-mentioned NAV) and the process waits (S454). If the packet does not exist on the air, a beacon signal is asserted and transmitted to the packet deletion unit 228 to that effect (S456).

(Fourth embodiment: forced deletion of transmission packet)
Further, the communication device 200 can forcibly delete the transmission packet in order to clear the current transmission packet in accordance with the mismatch of the sequence number of the transmission packet in communication with other nodes.

  For example, it is assumed that data communication is performed between the own communication device 200 and another node (destination node) in an autonomous distributed network where no coordinator exists. At this time, in order to manage duplicate reception of packets, the transmission data generation unit 214 sequentially assigns a sequence number to each transmission packet.

  The transmission packets to which the sequence numbers are assigned in this way are normally transmitted in the order of the sequence numbers. Therefore, the destination node as the destination can detect the transmission error only by determining the continuity of the sequence numbers. For example, if some trouble occurs in wireless communication between both communication devices, the sequence numbers may not be synchronized. Since the destination node always detects the presence of duplicate packets, if it detects a discontinuous sequence number, it transmits a transmission error to the destination communication device.

  FIG. 15 is a flowchart showing a flow of data communication between the communication device and the destination node. First, the communication apparatus 200 generates a transmission packet with a sequence number “10” and transmits the transmission packet together with the sequence number to the destination node (S500). When receiving the transmission packet, the destination node transmits a reception completion signal (ACK) together with the sequence number “10” to the communication apparatus 200 (S502). In response to the ACK control signal, the communication apparatus 200 recognizes that transmission of the transmission packet up to the sequence number “10” is completed, and deletes the transmission packet of the sequence number “10” in the memory buffer unit 212 ( S504).

  Next, the communication apparatus 200 starts preparation for transmission of the transmission packet with the sequence number “11”. The communication device 200 transmits the transmission packet with the sequence number “11” to the destination node (S506). However, it is assumed that the transmission packet with the sequence number “15” has reached the destination node due to some trouble. In response to the fact that the sequence number of the packet to be received is not “11” but “15”, the destination node notifies the communication device 200 that reception has failed (NACK). A command to reset is transmitted (S508).

  The communication device 200 recognizes that the sequence number is out of synchronization upon receiving a reception failure from the destination node, and resets the sequence number (S510). At this time, the packet deletion unit 228 wipes out the transmission packet scheduled to be transmitted with respect to the destination node from the memory buffer unit 212. This can be performed by the network management unit 210 forcibly setting the number 310 of corresponding transmission packets in the transmission / reception table of the packet deletion unit 228 to “1”. This is because the number of times 310 is subtracted to “0” at the next transmission of the control packet. In addition, the transmission packet may be forcibly deleted regardless of the number of times 310.

  Even when a sequence number synchronization error occurs due to such deletion processing, the network management unit 210 and the transmission / reception control unit 216 can be linked and efficient packet deletion can be realized.

  In the present embodiment, this is realized by an immediate ACK (Immediate ACK) in which the destination node returns a transmission completion (ACK) for each transmission packet. However, the present invention is not limited to this case. Thus, the present invention can also be applied to a system that improves the efficiency of packet transmission.

(Fifth embodiment: transmission packet deletion by NACK)
The packet deletion unit 228 deletes a transmission packet that has been delayed for a predetermined time in the memory buffer unit 212. The predetermined time may be defined by the number of reception error (NACK) signals from the destination node. Therefore, the packet deletion unit 228 converts the timeout based on the reception error signal (NACK) of the destination node. The packet deletion unit 228 stores the number of reception error signals instead of the number of control packets in the transmission / reception table, and converts the timeout by the count. With this configuration, the number of retransmissions of the transmission packet can be given uniformly to each node.

  Here, an ARQ (Automatic Repeat reQuest) function is added to the communication apparatus 200, and transmission packet deletion management is performed from two directions of timeout due to the number of ARQ and timeout due to packet waiting time.

  FIG. 16 is a flowchart showing a flow of data communication between the communication device and the destination node. First, the communication apparatus 200 generates a transmission packet with a sequence number “10” and transmits the transmission packet together with the sequence number (S600). When receiving the transmission packet, the destination node transmits a reception completion signal (ACK) together with the sequence number “10” to the communication apparatus 200 (S602). In response to the ACK control signal, the communication apparatus 200 recognizes that transmission of the transmission packet up to the sequence number “10” is completed, and deletes the transmission packet of the sequence number “10” in the memory buffer unit 212 ( S604).

  Next, the communication apparatus 200 starts preparation for transmission of the transmission packet with the sequence number “11”. Then, the communication device 200 transmits the transmission packet with the sequence number “11” to the destination node (S606). However, if the transmission of the transmission packet is not completed due to some problem, the destination node returns a NACK to the communication device 200 (S608).

  The communication device 200 retransmits the transmission packet (S610). However, if the transmission packet is not transmitted to the destination node, the destination node transmits a similar NACK (S612).

  When the number of NACKs from the destination node reaches the specified number, here two times, the communication apparatus 200 resets the sequence number and transmits the transmission packet scheduled to be transmitted with respect to the destination node to the memory buffer unit 212. (S614). This can be implemented by the network management unit 210 forcibly setting all the transmission packet counts 310 in the transmission / reception table of the packet deletion unit 228 to “1”. In addition, the transmission packet may be forcibly deleted regardless of the number of times 310. Even when a sequence number synchronization error occurs due to such deletion processing, the network management unit 210 and the transmission / reception control unit 216 can be linked and efficient packet deletion can be realized.

  Then, the communication apparatus 200 transmits the transmission packet with the new sequence number “0” to the destination node again (S620). Again, when a NACK is returned from the destination node (S622), the communication device 200 recognizes that communication with the destination node is no longer possible. The communication device 200 measures the time that the transmission packet is waiting in the memory buffer unit 212, and deletes the transmission packet whose standby time exceeds a predetermined time and all transmission packets having the same destination node as the transmission packet. (S624). Here, the period 630 indicates a timeout due to the number of ARQs, and the period 632 is a timeout due to a packet waiting time.

  In this embodiment, an example is given in which one sequence number is assigned to each packet. However, the present invention is not limited to this, and a sequence number is assigned to each MSDU (MAC Service Date Unit), and a plurality of packets are assigned to one packet. May be associated with each other. The destination node may send back a NACK based on the CRC error information added for each MSDU, or can send back a NACK when there is a problem in packet decoding.

  In the present embodiment, the destination node is realized by an immediate ACK in which transmission completion (ACK) is returned for each transmission packet. However, the present invention is not limited to this, and for example, a delayed ACK (Delayed ACK) can be used. In this case, the period 630 may become long. In addition, when the delayed ACK is used, the transmission / reception sequences may cross each other, but it can also be solved by arbitration.

  In the present embodiment, when the number of NACKs exceeds a predetermined number, the transmission / reception control unit 216 confirms each time. It is also possible to consider the design so that the process ends.

  The transmission packet may be deleted by deleting all transmission packets of the same destination node as the transmission packet, or may be deleted based on the target class.

  With the configuration that counts the number of NACKs, all transmission packets in the memory buffer unit can be managed in an integrated manner.

  According to the various embodiments described above, packet management for supporting high-speed data communication can be realized even in a system such as CSMA or PSMA in which transmission and reception times are not determined in advance. In addition, it is possible to realize processing for processing the sequence number out of sync, processing when the terminal managed by the terminal management of the network becomes invisible, packet management related to the decoding function with retransmission management by ARQ, and the like.

  As mentioned above, although preferred embodiment of this invention was described referring an accompanying drawing, it cannot be overemphasized that this invention is not limited to the example which concerns. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the claims, and these are naturally within the technical scope of the present invention. Understood.

  For example, in the above embodiment, a beacon signal is used as a control packet, and a transmission packet is deleted from the beacon signal. However, the present invention is not limited to this. For example, only an access point transmits a beacon signal as in 802.11. The transmission packet may be deleted by estimating the reception timing of the beacon signal in the network.

  In addition to the beacon signal, the transmission packet may be deleted when transmitting or receiving a control packet such as RTS, CTS, or ACK. Even in the transmission / reception of control packets in such a network, access to the memory buffer unit is disconnected, so that access collision to the memory buffer unit does not occur.

  However, in the case of CSMA, since the packet transmission or reception time is not scheduled in advance, if the transmission packet is deleted during packet transmission / reception, the deletion processing may become unstable, and the circuit configuration may be complicated. Need to be made. Therefore, the transmission packet may be deleted during the period indicated by DIFS or SIFS in FIG. However, due to advances in communication circuits provided in communication devices and the like in the near future, the above-mentioned DIFS and SIFS are shortened, and in a large-capacity memory buffer unit used for high-speed data transfer, the amount of transmission packets to be deleted at a time In many cases, the transmission packet may not be deleted during the DIFS or SIFS period. In this case, the use efficiency of the memory buffer unit is reduced, and wasted time is wasted. Therefore, in order to ensure a sufficient transmission packet deletion time, it is effective to use the beacon transmission or reception time as described above.

  In the present embodiment, it is assumed that transmission packets are transmitted to one node with respect to one communication device, but one-to-multiple transmission is also possible. Further, the communication device can be formed exclusively for transmission or reception.

  Note that the steps in the data deletion method of the present specification do not necessarily have to be processed in time series in the order described in the timing chart (flow chart), but are executed in parallel or individually (for example, in parallel). Processing or object processing).

It is explanatory drawing for demonstrating BSS defined by an infrastructure mode. It is the timing chart which showed the timing of the beacon signal in BSS. It is explanatory drawing for demonstrating IBSS defined by ad hoc mode. It is a timing chart which showed the timing of the beacon signal in IBSS. It is a timing chart for demonstrating the control by a RTS / CTS control signal. It is a timing chart which showed the transmission / reception timing of each node in a TDMA system. It is a timing chart which showed the transmission / reception timing of each node in a CSMA system. It is the block diagram which showed the schematic structure of the communication apparatus. It is explanatory drawing which showed schematically the data structure of the transmission / reception table. It is a timing chart for demonstrating the flow of transmission of a control packet, and the change of the transmission / reception table in each time. It is explanatory drawing which showed the transmission / reception table in each time of FIG. It is explanatory drawing which showed the transmission / reception table in each time of FIG. It is explanatory drawing which showed the transmission / reception table in each time of FIG. It is explanatory drawing which showed the transmission / reception table in each time of FIG. It is the flowchart figure which showed the flow of the data deletion method in 3rd Embodiment. It is the flowchart described in detail regarding the carrier sense at the time of assertion determination of a beacon signal. It is explanatory drawing which showed Frame format. It is the flowchart which showed the flow of the data communication of a communication apparatus and a destination node. It is the flowchart which showed the flow of the data communication of a communication apparatus and a destination node.

Explanation of symbols

200 communication device 210 network management unit 212 memory buffer unit 214 transmission data generation unit 216 transmission / reception control unit 218 physical layer Tx unit 222 physical layer Rx unit 224 physical layer control unit 226 reception data control unit 228 packet deletion unit 300 transmission / reception table

Claims (15)

A communication device that transmits data to a specific destination node in wireless communication in which management between nodes is performed using a control packet:
A memory buffer for temporarily holding transmission packets;
A packet transmission unit that transmits a transmission packet from the memory buffer unit to the destination node;
A transmission / reception control unit that controls transmission timing of the transmission packet and transmission / reception timing of the control packet;
A packet deletion unit that deletes the transmission packet to be deleted from the memory buffer unit during transmission or reception of the control packet when there is a transmission packet to be deleted;
A communication device comprising: The packet deletion unit
A transmission / reception table associating a transmission packet held in the memory buffer with a destination node of the transmission packet;
The communication apparatus according to claim 1, wherein all transmission packets having the same destination node as the transmission packet to be deleted are deleted.   The communication apparatus according to claim 2, wherein the transmission packet to be deleted is a transmission packet in which the destination node does not complete reception within a predetermined time.   The communication apparatus according to claim 3, wherein the predetermined time is defined by the number of transmissions or receptions of the control packet. In the transmission / reception table, the transmission packet is further associated with the number of transmissions or receptions of the control packet,
The said packet deletion part counts the frequency | count of transmission or reception of the said control packet for every transmission packet of the said transmission / reception table, and when the predetermined number is reached, deletes the said transmission packet, It is characterized by the above-mentioned. Communication equipment.   The communication apparatus according to claim 3, wherein the predetermined time is defined by the number of reception error signals from the destination node. In the transmission / reception table, the number of times of the reception error signal is further associated with the transmission packet,
The communication according to claim 6, wherein the packet deletion unit counts the number of reception error signals for each transmission packet of the transmission / reception table, and deletes the transmission packet when the predetermined number of times is reached. apparatus. A class is defined for the transmission packet,
The communication apparatus according to claim 2, wherein the packet deletion unit determines whether to delete all transmission packets having the same destination packet as the transmission packet to be deleted, according to the class. A network management unit for managing transmission packets;
The packet deletion unit notifies the network management unit that the transmission packet has been deleted,
The network management unit is managed separately from the memory buffer unit, deletes all transmission packets of the same destination node as the transmission packet to be deleted, and requests the packet deletion unit to delete the transmission packet again. The communication device according to claim 2, wherein:   The packet deletion unit forcibly deletes the transmission packet during transmission or reception of the next control packet, regardless of the number of transmissions or receptions of the control packet, after receiving the deletion command from the network control unit The communication device according to claim 9, wherein:   The communication apparatus according to claim 1, wherein the control packet is a beacon signal.   The communication apparatus according to claim 1, wherein the memory buffer unit is also used as a transmission / reception packet. A communication device that transmits data to a specific destination node in wireless communication in which management between nodes is performed using a control packet:
A memory buffer for temporarily holding transmission packets;
A packet transmission unit that sequentially assigns a sequence number to transmission packets from the memory buffer unit and transmits the packets to the destination node;
A transmission / reception control unit that controls transmission timing of the transmission packet and transmission / reception timing of the control packet;
A packet receiver that receives a received packet from the destination node and determines whether the sequence number is synchronized;
A packet deletion unit that deletes a transmission packet related to the destination node from the memory buffer unit during transmission or reception of the control packet when the sequence numbers are not synchronized;
A communication device comprising: A data deletion method for deleting data to be transmitted to a specific destination node in wireless communication in which management between nodes is performed by a control packet:
A memory buffer step for temporarily holding transmission packets;
A packet transmission step of transmitting the held transmission packet to the destination;
A transmission / reception control step for controlling transmission timing of the transmission packet and transmission / reception timing of the control packet;
A packet deletion step of deleting the transmission packet to be deleted from the memory buffer unit during transmission or reception of the control packet when there is a transmission packet to be deleted;
A method for deleting data, comprising: A data deletion method for deleting data to be transmitted to a specific destination node in wireless communication in which management between nodes is performed by a control packet:
A memory buffer step for temporarily holding transmission packets;
A packet transmission step of sequentially assigning a sequence number to the held transmission packets and transmitting them to the destination node;
A transmission / reception control step for controlling transmission timing of the transmission packet and transmission / reception timing of the control packet;
Receiving a received packet from the destination node and determining whether the sequence number is synchronized;
A packet deletion step of deleting a transmission packet related to the destination node from the memory buffer unit during transmission or reception of the control packet when the sequence numbers are not synchronized;
A method for deleting data, comprising:

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