JP2006066948A - Communication method, base station, and wireless terminal using automatic retransmission control in multi-hop communication - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an automatic retransmission method, a base station, and a wireless terminal which can decrease a delay due to automatic retransmission control in multi-hop communication so as to reduce influence on a host application. <P>SOLUTION: In a communication method of a network system including the base station and a plurality of the wireless terminals and having a multi-hop communication function wherein traffic between the base station and the wireless terminals is transceived by using a traffic channel by way of one or more of other wireless terminals, the base station transceives a control signal by using a control channel provided respectively and directly to each wireless terminal included in the multi-hop communication. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a communication method using automatic retransmission control (ARQ), a base station and a wireless terminal used in the communication method in a wireless system having a multi-hop communication function.

  In a system in which one or more wireless terminals communicate wirelessly, such as a mobile communication system, a wireless LAN system, or a wireless access system, there is a method in which a wireless terminal performs communication by relaying traffic for another wireless terminal. The communication is called a multi-hop communication function, and a network having a multi-hop communication function is called a multi-hop network.

  FIG. 17 is a diagram illustrating a configuration example of a multi-hop network according to a conventional technique. According to FIG. 17, the multi-hop network has a base station 1 and one or more wireless terminals (21, 22, 31 to 33 in the example of FIG. 17). In addition, although the base station 1 is also called an access point depending on the system, a “base station” is used below. A wireless terminal that relays traffic for another wireless terminal is hereinafter referred to as a relay terminal, and the wireless terminal that is the destination of the traffic is referred to as a destination terminal. The relay terminal / destination terminal is used only for the purpose of distinguishing the operation status of the current wireless terminal, and does not mean that it is a different wireless terminal. Each wireless terminal can receive traffic addressed to itself while relaying traffic for other wireless terminals, that is, can simultaneously operate as a relay terminal and a destination terminal. The traffic means a general term for voice / data transmitted / received by the destination terminal.

  According to FIG. 17, the destination terminal 32 existing in the communication area of the base station communicates directly with the base station and transmits traffic. In addition, since the destination terminal 31 existing outside the communication area of the base station cannot communicate directly with the base station, it communicates with the base station via the relay terminal 21 existing within the communication area of the base station. ing. A form that communicates directly with the base station like the destination terminal 32 is called single-hop communication, and a form that communicates with the base station via the relay terminal 21 like the destination terminal 31 is called multi-hop communication. Multi-hop communication is described in Non-Patent Document 1.

  Furthermore, even when the mobile station exists in the communication area of the base station 1 like the destination terminal 33, multi-hop communication may be performed. Although single-hop communication is possible, by reducing the communication distance between the wireless terminals, the propagation loss is reduced, and as a result, the reception power at the receiving wireless terminal is increased. Therefore, Eb / N0 (per bit) There is an advantage that high-speed transmission is possible.

  FIG. 18 is a sequence diagram of traffic transmission in multi-hop communication according to a conventional technique. Traffic is transmitted from the base station in the form of data packets. The relay terminal once receives the data packet and then transmits it to the destination terminal. Further, the relay terminal transmits an ACK (Acknowledgement) packet to the base station for confirmation of data packet reception. Similarly, the destination terminal transmits an ACK packet to the relay terminal.

  There are a plurality of methods for notifying the base station and / or the wireless terminal that transmitted the data packet from the wireless terminal that the reception was successful. In the above, the procedure of transmitting one ACK packet for each data section with respect to one data packet is shown. In addition to this, a method of transmitting one ACK packet for a plurality of data packets, or a NAK (Negative Acknowledgment) packet that requests retransmission of a lost packet when a specific packet is lost instead of an ACK packet. There is a method of transmitting.

  The ACK packet and NAK packet are called control signals and are signals closed to the wireless system. In multi-hop communication according to the prior art, as shown in FIG. 17, traffic and control signals are transmitted through the same route.

CK. Toh, "Ad Hoc Mobile Wireless Network", Translated by Structural Planning Laboratory, Kyoritsu Shuppan, 2003

  In the multi-hop communication according to the conventional technique, when packet loss does not occur, communication is possible without any problem as shown in FIG. However, when the quality of the wireless line is poor and packet loss occurs, there are a plurality of hops, so packet loss in each section and accompanying packet retransmission occur, and the delay time increases significantly. For this reason, compared with single hop communication, the influence on the characteristic of a high-order application by delay becomes large. This will be described below.

  FIG. 19 is a sequence diagram in the case where sequence number management is not performed in the relay terminal in the multi-hop communication according to the conventional technique. The destination terminal includes a wireless data processing unit that transmits and receives wireless packets and a user data processing unit (destination terminal upper layer in FIG. 19) that transmits and receives higher-level protocol (for example, TCP / IP) packets.

  A data packet (hereinafter simply referred to as data) 4 is lost between the relay terminal c and the destination terminal. The destination terminal detects the loss of data 4 by receiving data 5 and transmits NAK 4 to the base station. Data 4 is normally transmitted from the base station to the relay terminal 3, but is transmitted again from the base station. This is because each relay terminal does not perform sequence number management. In this way, in a configuration in which the relay terminal does not perform sequence number management, unnecessary packet retransmission occurs. In particular, when a packet is lost in a section where the number of hops from the base station is large, the delay time increases, which affects the characteristics of the host application.

  In order to avoid the increase in delay time described above, there is a configuration in which each wireless terminal performs sequence number management. FIG. 20 is a sequence diagram in the case where packet loss occurs between the base station and the relay terminal by performing sequence number management in the base station and the wireless terminal in the multi-hop communication according to the conventional technique. Here, a case where the destination terminal communicates with a fixed terminal connected to the wired system via a relay terminal and a base station is shown. As shown in FIG. 20, in communication between a fixed terminal and a destination terminal, data link control (automatic retransmission control) in the wireless system and data control (automatic retransmission control) in the upper layer operate in parallel. . Note that a NAK packet is used as the reception confirmation method of the wireless system.

  Data 1 transmitted from the fixed terminal is received by the destination terminal via the base station and the relay terminal. When data 1 is passed to the upper layer within the destination terminal, ACK1 is transmitted on the reverse path for reception confirmation (this ACK is an ACK of the upper layer). Data 2 is lost between the base station and the relay terminal. Since the data 3 has normally reached the relay terminal, at this point, the relay terminal detects the loss of the data 2 and transmits NAK2.

  The base station gives priority to retransmission of data 2 upon receipt of NAK2. In FIG. 20, this packet is lost again.

  When the data 4 reaches the relay terminal, the relay terminal transmits NAK2 again. The data 2 transmitted again by the base station has normally reached the relay terminal. Until data 2 is received, the relay terminal suspends transmission of data 3 and data 4 to the destination terminal in order to keep the data transmission order, and after data 2 is received, data 2 to data 4 are transmitted. .

  Thereafter, ACK2-4 is transmitted from the upper layer of the destination terminal. However, in the upper layer of the fixed terminal, the timer for data 2 has expired and data 2 is being retransmitted. When the data 2 reaches the destination terminal, the data 2 arrives in duplicate, which adversely affects the application. In particular, when an ACK packet is retransmitted from an upper layer, data retransmission of the upper layer is induced, causing a reduction in communication characteristics such as throughput.

  FIG. 21 is a sequence diagram in the case where packet loss occurs between a base station and a relay terminal and between a relay terminal and a destination terminal by performing sequence number management between the base station and the wireless terminal in multi-hop communication according to a conventional technique. . In FIG. 20, the same packet is lost several times in the same section. However, even if the same packet is lost in another section, the same result is obtained, and this problem is more likely to occur as the number of hops increases.

  As described above, even in the configuration in which the base station and the wireless terminal perform sequence number management, there is a mismatch between the data link control in the wireless system and the data control in the higher layer as a result of delay due to retransmission control due to packet loss. Wakes up and affects the higher level application. Furthermore, since sequence numbers are managed in each wireless terminal, the processing load on each wireless terminal increases, and the configuration becomes complicated, resulting in other problems such as increased power consumption and high cost. .

  In a configuration in which a control signal such as NAK is also transmitted and received through the same channel as traffic, transmission of the control signal may be delayed due to a large amount of data transmission. Here, the configuration in which transmission / reception is performed through the same channel is a configuration in which, as a wireless LAN system, as a result of sharing one transmission path, another wireless terminal cannot transmit another signal while transmitting a signal. means.

  FIG. 22 is a sequence diagram in the case where packet loss occurs during high traffic in a configuration in which a control signal is transmitted and received through the same channel as traffic. In FIG. 22, although the destination terminal detects the discontinuity of the sequence number by the reception of data 3, since the data is continuously transmitted, NAK2 cannot be transmitted, and NAK2 is transmitted after data 7 is received. Yes. In multi-hop communication, this state may occur in each radio section, delay time increases, and as a result, higher-order applications are affected.

  In the description of FIGS. 19 to 22, for the sake of simplicity, the packet addressed to the destination terminal from the fixed terminal is shown as an example in the wireless system. In a system such as a wireless LAN, since the maximum packet size in the wired system and the wireless system is the same, the packet can be transmitted as it is. On the other hand, in the case of a mobile communication system, the packet size in the wireless system is smaller than the packet size of the wired system, so it is necessary to divide the packet from the wired system into a plurality of small packets and transmit them in the wireless system There is. For this reason, the number of packets transmitted and received in the wireless system is greatly increased, and the above-described problem becomes more remarkable.

  Further, although the upper layer control signal (ACK or the like) is handled as data by the wireless system, the upper layer control signal delay naturally affects the upper application.

  Considering packet loss in multi-hop communication, a method of performing data transmission through a plurality of routes has been considered. However, the route with the highest quality is usually selected as the route between the base station and the destination terminal, and other routes are selected such that the number of hops is large and the delay time is large or the communication speed is low. It is not always possible to obtain communication quality equivalent to that of the route. In this way, the method using a plurality of paths is intended to eliminate data loss, and the above-described problem is not always solved.

  Therefore, an object of the present invention is to provide a communication method, a base station, and a wireless terminal that reduce delay due to automatic retransmission control in multi-hop communication and reduce the influence on a host application.

  Another object of the present invention is to prevent the retransmission packet from being lost again as much as possible and to reduce the influence of the delay caused by the re-erasing on the upper application.

  It is another object of the present invention to achieve the above object without increasing the processing load on the wireless terminal.

  It is another object of the present invention to provide a communication method, a base station, and a wireless terminal that reduce the delay of the control signal of the upper layer and reduce the influence on the upper application.

According to the communication method of the present invention,
Communication of a network system having a base station and a plurality of wireless terminals, and having a multi-hop communication function for transmitting and receiving traffic between the base station and the wireless terminals using a traffic channel passing through one or more other wireless terminals In the method, the base station transmits / receives a control signal to / from each wireless terminal included in the multi-hop communication using a control channel directly provided.

According to another embodiment of the communication method of the present invention,
Among at least one wireless terminal that relays traffic and a wireless terminal that is a traffic destination, at least a wireless terminal that is a traffic destination, a first step that monitors packet loss, and a first step, The wireless terminal that detected the packet loss uses the control channel to make a second step of requesting retransmission of the packet to the base station, and the base station that has received the packet retransmission request sends the packet requested for retransmission to the traffic channel and And / or a third step of retransmitting using the control channel.

According to another embodiment of the communication method of the present invention,
In the first step, the wireless terminal relaying the traffic transmits a reception confirmation of the packet to be relayed to the base station using the control channel, and the base station receiving the packet retransmission request receives the traffic. From the reception confirmation from the wireless terminal relaying the packet, the lost period of the packet requested for retransmission is identified, and instead of the retransmission of the packet using the traffic channel from the base station in the third step, the base station It is also preferable that the station transmits a retransmission request to the wireless terminal on the transmission side in the erasure section using a control channel, and the transmission side wireless terminal retransmits the erasure packet using a traffic channel.

Furthermore, according to another embodiment of the communication method of the present invention,
Each wireless terminal transmits a reception confirmation of the received packet to the base station using the control channel, and the base station identifies the lost packet detection and the lost section of the lost packet from the reception confirmation from each wireless terminal, Retransmission of the lost packet using a control channel and / or transmission of a retransmission request to the wireless terminal on the transmission side of the lost period using the control channel, and the transmitting wireless terminal receiving the retransmission request transmits a traffic channel. And the lost packet is retransmitted.

Furthermore, according to another embodiment of the communication method of the present invention,
It is also preferable to transmit and receive higher layer control signals using the control channel.

According to the base station in the present invention,
In a base station having a multi-hop communication function that transmits and receives traffic with a wireless terminal using a traffic channel that passes through one or more other wireless terminals, a control channel that transmits and receives control signals is included in each multi-hop communication. It has a function of being provided directly with each wireless terminal.

According to another embodiment of the base station of the present invention,
When a packet retransmission request is received from the wireless terminal through the control channel, it is preferable to have a function of retransmitting the packet requested for retransmission using the traffic channel and / or the control channel.

Further, according to another embodiment of the base station of the present invention,
A function for identifying a packet loss period based on reception confirmation of a packet notified from a wireless terminal using a control channel, and transmission of the loss period using a control channel instead of retransmission of a packet using the traffic channel It is also preferable to have a function of transmitting a retransmission request to the wireless terminal on the side, and causing the transmitting wireless terminal to retransmit the lost packet using a traffic channel.

Furthermore, according to another embodiment of the base station of the present invention,
It is also preferable to determine a retransmission route of the packet requested to be retransmitted based on a radio channel quality from the base station to the radio terminal.

Furthermore, according to another embodiment of the base station of the present invention,
It is also preferable to use a route including a traffic channel as a retransmission route of the packet requested to be retransmitted, and perform retransmission using the control channel only when retransmission by the route including the traffic channel exceeds a preset threshold. .

According to the wireless terminal of the present invention,
Even in a wireless terminal having a multi-hop communication function for transmitting and receiving traffic with a base station using a traffic channel passing through one or more other wireless terminals, even when a traffic channel is not provided directly with the base station by multi-hop communication. The control channel for transmitting / receiving control signals has a function of directly providing the control channel with the base station.

  It is also preferable that the base station and the radio terminal have radio interfaces of two or more different radio systems, and a control channel and a traffic channel between the base station and the radio terminal are provided by radio interfaces of different radio systems.

  By adopting a configuration in which the control channel is directly provided between the base station and the wireless terminal, the delay due to the automatic retransmission control can be reduced.

  By transmitting the retransmission packet directly from the base station to the destination terminal using the control channel, and by using both the control channel and the traffic channel, the increase of the delay due to the retransmission control is suppressed, and the retransmission packet is transmitted. Re-disappearance can be prevented as much as possible.

  As a result of reducing the delay, inconsistency with the host application can be resolved, and communication characteristics such as throughput can be improved.

  Only the base station collectively manages the sequence numbers, so that the processing load on the wireless terminal can be reduced, and the apparatus configuration can be simplified and the cost can be reduced.

  Even when only the base station performs sequence number management, the base station can identify the packet loss occurrence section, and retransmit the packet from the transmitting side of the lost wireless section, so that the packet is already transmitted normally again. It is possible to prevent transmission of the same packet, that is, retransmission of a packet to an unnecessary section, and to realize retransmission control with little delay.

  With respect to data addressed not only to the base station but also to the terminal itself, the wireless terminal performs sequence number management, whereby the number of control packets can be reduced while performing retransmission control with little delay.

  By transmitting the upper layer control signal directly to the base station using the control channel, an increase in the delay time of the upper layer control signal can be prevented.

  By using multiple systems in combination, it is possible to construct a flexible and efficient system.

  The best mode for carrying out the present invention will be described in detail below with reference to the drawings. In the following description, a mobile communication system is taken as an example, but the present invention is not limited to a mobile communication system, and can be applied to all systems having a multi-hop communication function. In a mobile communication system, there are a traffic channel for transmitting traffic of a higher-level application and a control channel for transmitting a control signal. These two channels are often logically separated, but can also be separated physically (eg, different frequencies). In the following description, for simplicity, it is assumed that a packet from a fixed terminal is transmitted through the wireless system without being divided.

  FIG. 1 is a protocol stack diagram of a multi-hop network according to the present invention, and FIG. 2 is a network configuration example. As shown in FIG. 2, the relay terminal 2 and the destination terminal 3 exist in the communication area of the base station 1. As already described, the relay terminal and the destination terminal are the same wireless terminal, and are used properly in order to distinguish the operation state. The term “wireless terminal” means both a destination terminal and a relay terminal.

  As shown in FIG. 1, a protocol for performing data link layer control in a wireless communication system is called a radio link protocol (RLP), and performs data transmission / reception, sequence number management, retransmission control, and the like. In the multihop communication according to the present invention, as shown in FIG. 2, a traffic channel for transmitting traffic is provided between the base station 1 and the relay terminal 2 and between the relay terminal 2 and the destination terminal 3. As a result, traffic between the base station and the destination terminal 3 is transmitted via the relay terminal 2. On the other hand, a control channel for transmitting a control signal is directly provided between each wireless terminal (relay terminal 2 and destination terminal 3) included in the multihop communication and the base station. As a result, a control signal such as NAK for the traffic received by the destination terminal 3 is transmitted directly to the base station 1 without passing through the relay terminal 2.

  Note that the traffic channel and control channel between the base station and the relay terminal can be physically separated or logically separated. On the other hand, the traffic channel between the relay terminal and the destination terminal and the control channel between the base station and the destination terminal are physically separated. Regardless of physical separation or logical separation, in the following description, first, the case where the mobile communication system is closed to the same mobile communication system will be described.

  (First Embodiment) In this embodiment, packet loss is monitored at each wireless terminal (relay terminal and destination terminal), and when packet loss is detected at the wireless terminal, a NAK is transmitted to the base station.

  FIG. 3 is a sequence diagram when packet loss occurs between the relay terminal and the destination terminal and retransmission is performed on the traffic channel in the first embodiment. Of the vertical lines of the base station, relay terminal, and destination terminal in the figure, the solid line represents the traffic channel, and the broken line represents the control channel (the same applies to the other figures). Data transfer between the traffic channel and the control channel is possible within the same base station or wireless terminal. In addition, each wireless terminal manages the sequence number of a packet, and the automatic retransmission request is made by the NAK method in which a retransmission request is made only when a packet dropout occurs. In preparation for packet retransmission, the base station stores transmitted packets.

  In FIG. 3, data 1 is normally received and sent to the upper layer of the destination terminal. Data 2 is lost between the relay terminal and the destination terminal, and the destination terminal detects the loss of data 2 when data 3 arrives. The destination terminal transmits NAK2 directly to the base station using the control channel, and the base station transmits data 2 with a retransmission flag to the destination terminal using the traffic channel. The already received data 2 arrives again at the relay terminal, but since it is data with a retransmission flag, it is transferred to the destination terminal. The destination terminal transfers the data to the upper layer with the sequence numbers aligned. This is because retransmission control by the upper layer operates when data is delivered to the upper layer in a state where the sequence numbers are discontinuous. By transmitting the control signal directly to the base station instead of transmitting it to the base station via the relay terminal, the delay due to the automatic retransmission control can be reduced.

  FIG. 4 is a sequence diagram when packet loss occurs between the relay terminal and the destination terminal in the first embodiment, and retransmission is performed on the control channel. The base station transmits data 2 directly to the destination terminal through the control channel, not the traffic channel. By setting the retransmission packet as a control channel instead of a traffic channel passing through the relay terminal, it is possible to reduce delay and reduce the possibility of the retransmission packet being lost again.

  FIG. 5 is a sequence diagram when packet loss occurs between the relay terminal and the destination terminal in the first embodiment, and retransmission is performed on the traffic channel and the control channel. If the retransmission packet of either route is transmitted normally, the destination terminal will receive the same packet, but the destination terminal manages the sequence number, so adopts the retransmission packet that arrived first, Discard retransmission packets that arrive later. While suppressing an increase in delay and using a plurality of paths even when the quality of each wireless channel is deteriorated, it is possible to reduce the packet loss rate and prevent the overall deterioration of the channel quality.

  Further, the wireless channel quality from the base station to the wireless terminal is calculated, for example, a single hop route or a multi-hop route is selected with a short delay time, and the packet is retransmitted using the selected route. Is possible.

  Also, there is an advantage that packet retransmission is usually performed using a traffic channel, and packet retransmission is performed using a control channel when packet retransmission on the traffic channel exceeds a preset threshold. This is because the control channel often has a lower communication speed than the traffic channel and cannot process a large amount of data. By reducing the frequency of using the control channel and using the control channel complementarily in a certain case, there is an effect of improving the characteristics of the entire system.

  FIG. 6 is a sequence diagram when a plurality of destination terminals are connected to the relay terminal in the first embodiment.

  In order for the relay terminal to correctly transmit a packet to a plurality of destination terminals, an identifier is required for the packet. One such identifier is an address header. An example of a frame having an address header is shown in FIG. The base station sets a route to the destination terminal, and describes the set route in the destination header. In the frame of FIG. 7A, the transmission source (base station), the relay terminal, and the destination terminal a are described. However, as shown in FIG. The address of the relay terminal (relay terminal a, relay terminal b) is added. The relay terminal looks at these address headers and identifies the wireless terminal to be transferred next.

  Although the description has been given with the frame having the address header, the present invention is not limited to this. For example, the time division multiple access method (TDMA) used in the mobile communication system, code division multiplexing, and the like are used. It is also possible for the relay terminal to perform transfer based on physical layer information in the access method (CDMA), that is, the allocation slot position and the allocation code.

  8 to 10 are sequence diagrams in the case where packet loss occurs between the base station and the relay terminal in the first embodiment, which is the same as FIGS. 3 to 5.

  Second Embodiment In this embodiment, each wireless terminal does not perform sequence number management such as packet loss monitoring, but simply confirms reception of received data, that is, notifies the base station of the sequence number via the control channel. Just do it. The base station collectively manages the sequence numbers based on the notification, and identifies the packet lost due to the notification and its lost section.

  FIG. 11 is a sequence diagram of the second embodiment. Upon receiving data 1, each wireless terminal transmits ACK1 to the base station in order to notify the base station that the data has been received. After receiving ACK1 from all the wireless terminals, the base station sends SYN1 to the destination terminal. Send. The destination terminal passes data 1 to the upper layer upon receiving SYN1. This is to avoid passing discontinuous data to the upper layer. In other words, since the destination terminal does not manage the sequence number, the base station that manages the sequence number confirms the continuity of the sequence number, and after the base station confirms, the destination terminal transfers to the upper layer. By doing so, it is possible to avoid passing discontinuous data to the upper layer.

  Data 2 is normally received between the base station and the relay terminal, but is lost between the relay terminal and the destination terminal. For this reason, ACK2 is not transmitted from the destination terminal to the base station. Data 3 reaches the destination terminal and ACK3 is transmitted. The base station detects the discontinuity of the sequence number by receiving this ACK3. At this time, since the base station has received ACK2 from the relay terminal, it can be determined that the data 2 disappearance section is between the relay terminal and the destination terminal. The base station that has identified the lost packet and the lost section transmits NAK2 using the control channel to retransmit data 2 to the relay terminal, and the relay terminal receives data 2 using the traffic channel by receiving NAK2. Resend to the terminal.

  The relay terminal stores the transmitted packets, but the reception of the NAK request also means that the packet up to the previous one of the NAK request has arrived normally. Can be removed from the buffer. This suppresses an increase in the buffer amount. However, in an environment where the line quality is good and packet loss is unlikely to occur, the frequency of NAK reception is low, and the buffer amount may increase. For this reason, when the value (the number of packets or the data size) set in advance is exceeded, the stored packet is deleted from the buffer.

  As described above, since all the wireless terminals can directly communicate with the base station through the control channel, it is possible to perform packet processing under the control of the base station. As described above, the base station controls packet transmission of all the wireless terminals, so that the sequence number management in each wireless terminal becomes unnecessary, and the processing load on the wireless terminals can be reduced. In addition, the base station collectively controls packet transmission, thereby preventing retransmission packets from being transmitted to unnecessary sections.

  Further, in the above description, the retransmission packet is transmitted only from the transmission side wireless terminal in the packet loss period through the traffic channel. However, it is possible to transmit the retransmission packet directly from the base station through the control channel or to use them together.

  (Third Embodiment) In the present embodiment, the destination terminal monitors packet loss, and if a loss is detected, makes a retransmission request to the base station. Each relay terminal transmits reception confirmation of data to be relayed to the base station, but does not monitor packet loss for the data to be relayed.

  FIG. 12 is a sequence diagram when one destination terminal is connected to a relay terminal in the third embodiment. Since the destination terminal manages the sequence number of the data addressed to itself, when the packet loss is detected, the destination terminal directly transmits a NAK request to the base station using the control channel. In FIG. 12, the loss of data 2 is detected, and NAK2 is transmitted to the base station. Next, the base station specifies the lost section of the requested packet by the reception confirmation (ACK) from the relay terminal, and transmits the NAK to the transmitting side wireless terminal in the lost section to perform retransmission.

  In FIG. 12, the retransmitted packet is transmitted from the transmitting wireless terminal in the packet loss period using the traffic channel. However, it is possible to directly transmit the retransmitted packet from the base station through the control channel or to use them together. .

  FIG. 13 is a sequence diagram when a plurality of destination terminals are connected to the relay terminal in the third embodiment. If there are a plurality of destination terminals and all retransmission packets are transmitted from the base station, a lot of traffic flows in the base station-relay terminal section, which is a common radio section. In particular, since the packet is normally transmitted between the base station and the relay terminal, unnecessary packet retransmission occurs and communication efficiency deteriorates. On the other hand, as shown in FIG. 13, by performing packet retransmission from a relay terminal in a section in which packet loss has occurred, unnecessary traffic is prevented and retransmission packets are transmitted in unnecessary sections. Prevent data packet delays.

  In this way, in the destination terminal, only with respect to the data addressed to the own terminal, by performing the sequence number management, retransmission control by the NAK request becomes possible, and compared with the configuration in which the sequence number management is performed only by the base station, In particular, ACK packet reduction is possible. Note that the relay terminal stores the transmitted packets, but receiving a NAK request means that the packets up to the previous one of the NAK request have arrived normally, so these packets are deleted from the buffer. .

  FIG. 14 is a sequence diagram when the base station and the destination terminal manage sequence numbers and there are a plurality of relay terminals in the third embodiment. FIG. 14 shows an example in which each wireless terminal transmits one control signal for a plurality of data without transmitting a control signal (ACK / NAK) for each data. For example, the relay terminal a transmits ACK1-4 after receiving data 1-4. In this way, the delay associated with retransmission control can be reduced by a configuration in which one control signal is returned for a plurality of data.

  Also, higher layer control signals can be transmitted directly from the destination terminal to the base station via the control channel, so that the delay can be reduced compared to the transmission on the traffic channel via the relay terminal. The influence on the host application due to the delay of the control signal can be reduced. FIG. 15 is a sequence diagram in the case of transmitting an upper layer control signal through a control channel.

  In the above-described embodiment, the case where the communication system is closed to the same communication system has been described as an example. However, the present invention does not have to be closed to the same communication system, and a plurality of different communication systems can be used together. FIG. 16 is a diagram showing a configuration in which a plurality of systems are used together in multi-hop communication according to the present invention.

  According to FIG. 16, the base station and the radio terminal have radio interfaces of system A and system B, which are different radio systems. The traffic channel is composed of the system A radio interface, and the control channel is composed of the system B radio interface. For example, system A is a mobile communication system, and system B is a wireless LAN. By using different systems in this way, a flexible configuration is possible. In addition, it is possible to construct an economical system by effectively utilizing an existing system and then introducing a new system.

Protocol stack diagram of a multi-hop network according to the present invention 1 is a network configuration example according to the present invention. FIG. 6 is a sequence diagram when packet loss occurs between a relay terminal and a destination terminal in the first embodiment, and retransmission is performed using a traffic channel. FIG. 5 is a sequence diagram when packet loss occurs between a relay terminal and a destination terminal in the first embodiment and retransmission is performed using a control channel. FIG. 5 is a sequence diagram when packet loss occurs between a relay terminal and a destination terminal in the first embodiment, and retransmission is performed using a traffic channel and a control channel. In 1st Embodiment, it is a sequence diagram in case the some destination terminal is connected to the relay terminal. It is a figure which shows the example of the flame | frame which has an address header. In 1st Embodiment, it is a sequence diagram in case packet loss generate | occur | produces between a base station and a relay terminal, and it retransmits with a traffic channel. In 1st Embodiment, it is a sequence diagram in case packet loss generate | occur | produces between a base station and a relay terminal, and it resends by a control channel. In 1st Embodiment, it is a sequence diagram in case packet loss generate | occur | produces between a base station and a relay terminal, and it resends with a traffic channel and a control channel. It is a sequence diagram of a second embodiment. In 3rd Embodiment, it is a sequence diagram in case one destination terminal is connected to the relay terminal. FIG. 10 is a sequence diagram when a plurality of destination terminals are connected to a relay terminal in the third embodiment. In 3rd Embodiment, it is a sequence diagram in case a base station and a destination destination terminal manage a sequence number, and there exist several relay terminals. It is a sequence diagram in the case of transmitting the control signal of an upper layer with a control channel. It is a figure which shows the structure which used multiple systems together in the multihop communication by this invention. It is a figure which shows the structural example of the multihop network by a prior art. It is a sequence diagram of traffic transmission in multi-hop communication according to a conventional technique. It is a sequence diagram when sequence number management is not performed in a relay terminal in multi-hop communication according to the conventional technology. FIG. 10 is a sequence diagram when packet loss occurs between a base station and a relay terminal by performing sequence number management in a base station and a wireless terminal in multi-hop communication according to a conventional technique. FIG. 10 is a sequence diagram in the case where packet loss occurs between a base station and a relay terminal, and between a relay terminal and a destination terminal by performing sequence number management between the base station and the wireless terminal in multi-hop communication according to a conventional technique. FIG. 11 is a sequence diagram when packet loss occurs during high traffic in a configuration in which a control signal is transmitted and received through the same channel as traffic.

Explanation of symbols

1 Base station 2, 21, 22 Relay terminal 3, 31, 32, 33 Destination terminal

Claims (13)

A base station and a plurality of wireless terminals;
In a communication method of a network system having a multi-hop communication function for transmitting and receiving traffic between a base station and a wireless terminal using a traffic channel passing through one or more other wireless terminals,
A base station transmits / receives a control signal to / from each wireless terminal included in multi-hop communication using a control channel directly provided. A first step of monitoring packet loss in at least a wireless terminal that is a traffic destination among at least one wireless terminal that relays traffic and a wireless terminal that is a traffic destination;
In the first step, the wireless terminal that has detected packet loss uses the control channel to make a packet retransmission request to the base station,
The communication method according to claim 1, wherein the base station that has received the packet retransmission request has a third step of retransmitting the packet requested for retransmission using a traffic channel and / or a control channel. . In the first step, the wireless terminal that is relaying traffic transmits a reception confirmation of the packet to be relayed to the base station using the control channel,
The base station that has received the retransmission request for the packet specifies an erasure section of the packet requested for retransmission based on the reception confirmation from the wireless terminal that relays the traffic,
Instead of retransmitting a packet using a traffic channel from the base station in the third step, the base station uses a control channel to transmit a retransmission request to the wireless terminal on the transmission side in the erasure section,
The communication method according to claim 2, wherein the transmitting-side wireless terminal retransmits the lost packet using a traffic channel. Each wireless terminal transmits a reception confirmation of the received packet to the base station using the control channel,
The base station detects the lost packet from the reception confirmation from each wireless terminal and identifies the lost section of the lost packet,
Retransmit the lost packet using the control channel and / or send a retransmission request to the wireless terminal on the transmission side of the lost interval using the control channel;
The communication method according to claim 1, wherein the transmitting wireless terminal that has received the retransmission request retransmits the lost packet using a traffic channel.   5. The communication method according to claim 1, wherein an upper layer control signal is also transmitted and received using a control channel. In a base station having a multi-hop communication function for transmitting and receiving traffic with a wireless terminal using a traffic channel passing through one or more other wireless terminals,
A base station having a function of directly providing a control channel for transmitting and receiving a control signal with each wireless terminal included in multi-hop communication.   7. The base according to claim 6, wherein when a packet retransmission request is received from a wireless terminal through a control channel, the packet is retransmitted using a traffic channel and / or a control channel. Bureau. From the reception confirmation of the packet notified from the wireless terminal using the control channel, the function of identifying the lost section of the packet,
Instead of retransmitting the packet using the traffic channel, a retransmission request is transmitted to the transmitting-side radio terminal in the erasure interval using a control channel, and the lost packet is retransmitted from the transmitting-side radio terminal using the traffic channel. The base station according to claim 7, further comprising:   The base station according to claim 7 or 8, wherein a retransmission path of the packet requested to be retransmitted is determined based on a radio channel quality from the base station to the radio terminal.   A route including a traffic channel is used as a retransmission route of the packet requested to be retransmitted, and retransmission is performed using the control channel only when retransmission by the route including the traffic channel exceeds a preset threshold. The base station according to claim 7 or 8.   The base station according to claim 6, wherein the base station has two or more radio interfaces of different radio systems, and the control channel and the traffic channel are provided by radio interfaces of different radio systems. In a wireless terminal having a multi-hop communication function for transmitting / receiving traffic with a base station using a traffic channel passing through one or more other wireless terminals,
A wireless terminal having a function of directly providing a control channel for transmitting and receiving control signals with a base station even when a traffic channel is not directly provided with the base station by multi-hop communication.   The wireless terminal according to claim 12, wherein the wireless terminal has two or more wireless interfaces of different wireless systems, and the control channel and the traffic channel are provided by wireless interfaces of different wireless systems.

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