JP2008054095A - Tdma communication method, tdma transmitter, and tdma communication system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a TDMA communication method, a TDMA transmitter, and a TDMA communication system, which reduces a round-trip delay time in TCP communication in a demand assignment type TDMA communication system in which a transmission band is dynamically assigned. <P>SOLUTION: The demand assignment type TDMA communication method is composed so that a demand signal is controlled in order to prevent the signal from being discarded because of collision and a time slot is dynamically reserved and assigned. Specific data are separated from inputted data to be transmitted so as to transmit the separated specific data while including them in the demand signal before assignment. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a demand assignment type TDMA (Time Division Multiple Access) communication method, a TDMA transmission apparatus, and a TDMA communication system that dynamically reserve and assign time slots.

  In a packet-switched point-to-multipoint wireless access network in which single-station-to-multipoint communication is performed between a base station and a plurality of subscriber stations, a demand assignment type TDMA method is widely used. (For example, Non-Patent Document 1).

  TDMA is used for uplink communication from the subscriber station to the base station, and TDM (Time Division Multiplex) is used for downlink communication from the base station to the subscriber. For transmission / reception separation, TDD (Time Division Duplex, Time Division Duplex) or FDD (Frequency Division Duplex, Frequency Division Duplex) is used. As a circuit allocation method, a system that dynamically allocates a transmission band according to the amount of data by packet switching is used instead of a system that allocates a fixed band of a circuit switching type.

  Each station requests a bandwidth by a demand signal, the base station aggregates the demand signal, assigns a time slot to each subscriber station, sends the information to each subscriber station by an assign signal, and each subscriber station assigns Data is transmitted only for the designated time slot. In this case, in order to ensure fairness among subscriber stations and to reduce transmission delay, it is effective to perform control so that demand signals are not discarded due to collision.

  Recently, triple play services that include voice, video traffic, and best-effort Internet traffic that require QoS (Quality of Service) control have become widespread. Since it is difficult to ensure QoS in a situation where traffic requiring QoS control and best effort traffic are mixed, it is common to implement priority control technology in access network devices.

  When considering user satisfaction regarding a network service such as a triple play service, the stability of audio and video is naturally an important index, but the throughput value in FTP (File Transfer Protocol) is also an important index. Since FTP generally uses TCP (Transmission Control Protocol), the round-trip delay time during transmission affects the throughput value.

  FIG. 1 shows a communication flow after establishing a TCP connection in FTP.

  The server sends a certain amount of data. The maximum value of the amount of data that the server can transmit at one time is defined by the maximum window size (Rwin), and is usually 64 kbytes. After receiving a certain amount of data from the server, the client returns an ACK (Acknowledgement) when normally received, and returns a NACK (Unknown segment) when requesting retransmission. The server transmits the next data after receiving the ACK / NACK. For this reason, the maximum throughput increases as the round-trip delay time from when the server transmits data until it receives ACK is shorter.

  FIG. 2 shows the relationship between the round trip delay time and the maximum throughput.

  In particular, at the time of high throughput, an increase in round trip delay time leads to a decrease in maximum throughput. For this reason, it is desirable to minimize the transmission delay when designing the system.

Yasui, Mizumoto, Kuwahara, “Wireless IP Access System Signal Processing Technology”, NTT R & D, Vol. 51, no. 11, pp 928-937, 2002

  FIG. 3 shows a communication flow after establishing a TCP connection in the conventional demand assignment type TDMA system.

  In the ACK / NACK reply from the client, since transmission is performed after waiting for bandwidth allocation by the demand signal and the assignment signal, an ACK / NACK transmission delay occurs and the round-trip delay time increases. Decreases. Although there is a method using a pre-assignment method to reduce the delay time, the frequency utilization efficiency of the entire system decreases as the number of subscriber stations increases because a fixed transmission band is secured. The maximum transmission speed per station will be reduced.

  Accordingly, an object of the present invention is to provide a TDMA communication method, a TDMA transmission apparatus, and a TDMA communication system capable of reducing the round trip delay time in TCP communication in a demand assignment type TDMA communication system that dynamically allocates a transmission band. It is in.

  According to the present invention, the demand signal is controlled so as not to be discarded due to a collision, and is a demand assignment type TDMA communication method that dynamically reserves and allocates time slots, and is specified from input data to be transmitted. A TDMA communication method for separating data and transmitting the separated specific data in a demand signal before assignment is provided.

  The specific data is preferably ACK / NACK in TCP.

  When separating specific data, it is also preferable to use at least one of a frame length, a TCP header included in the frame, and a TCI (Tag Control Information) field of a VLAN (Virtual LAN) tag as an identifier.

  According to the present invention, the data separation means for extracting the specific data from the input data to be transmitted based on a predetermined extraction criterion, the first queue structure accumulation unit for storing the extracted specific data, and the specific Storage means having a second queue structure storage unit for storing input data excluding data, the extracted specific data is read from the first queue structure storage unit, assigned to the area of the demand signal, and multiplexed with the demand signal Demand multiplexing means for generating a multiple demand signal, and the multiple demand signal from the demand multiplexing means are transmitted to the TDMA receiver via the communication network, and read from the second queue structure accumulating unit after assignment based on the demand signal Transmission means for transmitting input data excluding specific data and other control signals to the TDMA receiver via the communication network TDMA transmission device is provided.

  The data separation means is preferably means for extracting ACK / NACK in TCP as the specific data.

  The data separation means is preferably means for separating specific data using at least one of the frame length, the TCP header included in the frame, and the TCI field of the VLAN tag as an identifier.

  According to the present invention, there is further provided a TDMA communication system comprising the above-described TDMA transmission apparatus, a communication network, and a TDMA reception apparatus connectable to the TDMA transmission apparatus via the communication network. Receiving means for receiving a signal from a TDMA transmitter and extracting multiple demand signals, data and other control signals; and demand separating means for separating specific data from the multiple demand signals based on a predetermined extraction criterion; A first queue structure storage unit for storing the specified data, a storage unit having a second queue structure storage unit for storing data excluding the specific data, the specific data read from the first queue structure storage unit, and TDMA communication comprising output means for combining and outputting data excluding the specific data read from the second queue structure storage unit Stem is provided.

  It is preferable that the communication network is a packet-switched point-to-multipoint wireless access network and uses a demand assignment type TDMA system in which demand signals are controlled so as not to be discarded due to collision.

  According to the present invention, it is possible to reduce the round-trip delay time in TCP communication in the TDMA communication method that dynamically allocates the transmission band by the demand assignment method, so that the TCP throughput can be improved.

  FIG. 4 is a block diagram schematically showing the configuration of the TDMA communication system in one embodiment of the present invention.

  The TDMA communication system in this embodiment is a system that dynamically allocates a transmission band by a demand assignment system. As shown in the figure, a TDMA transmission apparatus 100, a TDMA reception apparatus 110, and a communication network 120 that connects them. And. In the present embodiment, the TDMA transmitting apparatus 100 is a transmitting apparatus on one subscriber station side, the TDMA receiving apparatus 110 is a receiving apparatus on the base station side, and the subscriber station and the base station connect the communication network 120. Connected through.

  The TDMA transmission apparatus 100 includes a data separation unit 101, a frame storage unit 102, a demand multiplexing unit 103, and a transmission unit 104.

  The TDMA receiving apparatus 110 includes a receiving unit 111, a demand separating unit 112, a frame storage unit 113, and a data output unit 114.

  The data separation unit 101 in the TDMA transmission apparatus 100 extracts specific data from the data input to the TDMA transmission apparatus 100 based on a predetermined extraction criterion. That is, it is separated into specific data and other input data. The specific data can be ACK / NACK in TCP, and in extracting the specific data, at least one of the frame length, the TCP header included in the frame, and the TCI field of the VLAN tag is used as the identifier. Use one.

  The specific data separated by the data separation unit 101 and the input data excluding the specific data are the first queue structure storage unit for specific data (specific data queue) and the second queue for input data excluding the specific data. The frame storage unit 102 having a structure storage unit (other data queue) is input, the specific data is stored in the first queue structure storage unit, and the input data excluding the specific data is stored in the second queue structure storage unit. Stored.

  The demand multiplexing unit 103 reads the specific data stored in the first queue structure storage unit of the frame storage unit 102, assigns it to the demand signal area, multiplexes it with the demand signal, generates a multiple demand signal, To 104.

  The transmitting unit 104 transmits a multiple demand signal to the TDMA receiving apparatus 110 side on the base station side via the communication network 120 in order to request a band. Thus, the specific data is transmitted together with the demand signal, that is, before the time slot is allocated.

  The base station aggregates the demand signals multiplexed into the multiple demand signals sent from each subscriber station, assigns a time slot to each subscriber station, and sends the information to the subscriber station by an assign signal.

  The transmitter 104 in the TDMA transmitter 100 of the subscriber station, after such assignment, only for the assigned time slot, the input data excluding the specific data read from the second queue structure storage unit in the frame storage unit 102, And other control signals are transmitted to the TDMA receiving apparatus 110 side on the base station side via the communication network 120.

  In this embodiment, the communication network 120 is a packet-switched point-to-multipoint wireless access network, and uses a demand assignment type TDMA system in which demand signals are controlled not to be discarded due to collision. Yes.

  The TDMA receiving apparatus 110 on the base station side receives data from the TDMA transmitting apparatus 100 on the subscriber station side via the communication network 120.

  The receiving unit 111 in the TDMA receiving apparatus 110 on the base station side extracts multiple demand signals, data, and other control signals, and the demand separating unit 112 extracts specific data from the extracted multiple demand signals, for example, ACK / NACK in TCP, Are separated based on a predetermined extraction criterion.

  The frame storage unit 113 includes a first queue structure storage unit (specific data queue) for specific data and a second queue structure storage unit (other data queues) for input data excluding the specific data. The separated specific data from the demand separation unit 112 is input to and accumulated in the first queue structure storage unit, and the data excluding the specific data from the reception unit 111 is stored in the second queue structure storage unit. Input and accumulate.

  The data output unit 114 combines and outputs the specific data read from the first queue structure storage unit and the second queue structure storage unit of the frame storage unit 113 and data excluding the specific data, respectively.

  As data handled in the present invention, specifically, an Ethernet frame can be assumed. In this case, the ACK / NACK data can be handled as an ACK / NACK frame, and the frame output is not basically changed before and after the data transmission. The output frames may be output in the order of input by FIFO (First In First Out) or round robin. That is, in this case, processing for analyzing and combining the inside of the frame is not performed.

  FIG. 5 shows a communication flow after the TCP connection is established in the demand assignment type TDMA system in this embodiment.

  As is clear from the above description and the figure, the ACK / NACK response from the client can be transmitted without waiting for bandwidth allocation by demand assignment by using multiple demand signals. Since the delay is shortened and the round-trip delay time does not increase, the throughput in TCP communication can be improved.

  All the embodiments described above are illustrative of the present invention and are not intended to be limiting, and the present invention can be implemented in other various modifications and changes. Therefore, the scope of the present invention is defined only by the claims and their equivalents.

It is a figure explaining the flow of communication after TCP connection establishment in FTP. It is a figure which shows the relationship between a round-trip delay time and a maximum throughput. It is a figure which shows the flow of communication after TCP connection establishment in the conventional demand assignment type TDMA system. It is a block diagram which shows the structure of the TDMA communication system in one Embodiment of this invention. It is a figure which shows the flow of communication after TCP connection establishment in the demand assignment type TDMA system in this embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 TDMA transmitter 101 Data separation part 102, 113 Frame storage part 103 Demand multiplexing part 104 Transmission part 110 TDMA receiver 111 Reception part 112 Demand separation part 114 Data output part

Claims (8)

  A demand assignment type TDMA communication method that is controlled so that a demand signal is not discarded due to a collision and dynamically reserves and assigns a time slot, and separates specific data from input data to be transmitted, A TDMA communication method, wherein the separated specific data is transmitted by being included in a demand signal before assignment.   The TDMA communication method according to claim 1, wherein the specific data is ACK / NACK in TCP.   3. The TDMA communication method according to claim 1, wherein when separating the specific data, at least one of a frame length, a TCP header included in the frame, and a TCI field of a VLAN tag is used as an identifier. . Data separating means for extracting specific data from input data to be transmitted based on a predetermined extraction criterion;
A storage unit having a first queue structure storage unit for storing the extracted specific data, and a second queue structure storage unit for storing input data excluding the specific data;
Demand multiplexing means for reading the extracted specific data from the first queue structure storage unit, allocating it to an area of a demand signal, and multiplexing the demand signal to generate a multiple demand signal;
A multi-demand signal from the demand multiplexing means is transmitted to a TDMA receiver via a communication network, and input data excluding the specific data read from the second queue structure storage unit after assignment based on the demand signal; and Transmitting means for transmitting other control signals to the TDMA receiver via the communication network;
A TDMA transmitter characterized by comprising:   5. The TDMA transmission apparatus according to claim 4, wherein the data separation means is means for extracting ACK / NACK in TCP as the specific data.   6. The data separation means is means for separating the specific data using at least one of a frame length, a TCP header included in the frame, and a TCI field of a VLAN tag as an identifier. The TDMA transmission apparatus described in 1. A TDMA communication system comprising the TDMA transmission apparatus according to any one of claims 4 to 6, a communication network, and the TDMA reception apparatus connectable to the TDMA transmission apparatus via the communication network,
The TDMA receiver is
Receiving means for receiving a signal from the TDMA transmitter and extracting the multiple demand signal, data, and other control signals;
Demand separating means for separating the specific data from the multiple demand signal based on a predetermined extraction criterion;
A storage unit having a first queue structure storage unit for storing the separated specific data, and a second queue structure storage unit for storing data excluding the specific data;
Output means for combining and outputting the specific data read from the first queue structure storage unit and the data excluding the specific data read from the second queue structure storage unit;
A TDMA communication system comprising:   The communication network is a packet-switched point-to-multipoint wireless access network, and uses a demand assignment type TDMA system in which demand signals are controlled so as not to be discarded due to a collision. The TDMA communication system according to claim 7.

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