JPH06244862A - Satellite communication system - Google Patents

Abstract

PURPOSE:To provide a satellite communication system improved in line use efficiency while guaranteeing maximum cell delay. CONSTITUTION:This system has a transmission earth station 100 classifying inputted cells every VPI or VCI in a header, composing a TDMA burst by collecting plural cells every classified cell group and transmitting them to a communication satellite 200 and a recepion earth station 400 taking out the only cells addressed to it own station from the received TDMA burst based on VPI or VCI and transferring them to an ATM network. The transmission earth station includes a means measuring the number of inputted cells every cell group and transferring them to a line control station 300. The line control station includes a means predicting the band of a necessary satellite line from the number of cells every received cell group and a means performing a satellite line allocation or a TDMA burst allocation based on this and transferring the changed allocation information to the transmission earth station.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a communication system capable of flexibly connecting a satellite TDMA communication network and a terrestrial ATM communication network while guaranteeing a maximum cell delay and improving the line utilization efficiency.

[0002]

2. Description of the Related Art Transmission speed of high-speed data communication, etc. Mb /
s to several tens of Mb / s and higher speed networks with a focus on broadband ISDN (B-IS
Broadband ISDN (DN) is under consideration. This B-ISDN transfer mode is the asynchronous transfer mode (A
TM; Asynchronous Transfer Mode) is a fixed length cell (5
By changing the number of transfers per unit time of 3 bytes (hereinafter called cell), it is possible to support arbitrary and variable transmission rates, and is suitable for multimedia communication in which voice, video and data signals are integrated. . The characteristic of high-speed data communication traffic is that the required maximum transmission rate is high and the hold time is short (that is, ON / OFF is repeated at high speed), so the ratio of the average transmission rate to the maximum transmission rate is several%.
It is very bursty with the following. In order to apply satellite communication to this high-speed data communication, it is necessary to guarantee the maximum cell delay, and to realize a system that does not require retransmission control in order to increase the effective use efficiency of the satellite line. is important.

The conventional line control systems used for satellite communication include a random access system, a fixed allocation system, a reservation allocation system (reserved TDMA system, etc.), and a call allocation system (demand assign TDMA system, etc.). Considering application to high-speed data communication, the random access method requires each transmission earth station to packetize and transmit when traffic occurs or changes, so retransmission control due to collision of data bursts is required, and maximum cell delay cannot be guaranteed. Alternatively, there is a problem that only very low line usage efficiency can be achieved. In the case of the fixed allocation method, the line needs to be stretched in a mesh to the specific ground beforehand, so it is necessary to always allocate the maximum bandwidth required to guarantee the maximum cell delay. There is a problem that the average usage efficiency of the line is greatly reduced. In the case of the reserved access method, it is not possible to follow the traffic that is repeatedly turned on and off at high speed due to the control delay for capturing the line by reservation, and as a result, the average line usage efficiency is the same as in the fixed allocation method. There is a problem that it decreases. In the call-by-call allocation method, the line control station allocates the line when the call occurs. Therefore, similar to the reservation allocation method, the traffic is switched on and off at high speed due to the control delay for the line allocation. There is a problem that it is not possible to follow up, and as a result, the average line use efficiency decreases as in the fixed allocation method.

[0004]

SUMMARY OF THE INVENTION The present invention provides a satellite communication system capable of improving line utilization efficiency while guaranteeing maximum cell delay for high-speed data communication having a large maximum traffic value and extremely high burstiness. The purpose is to provide.

[0005]

A feature of the present invention is that a plurality of cells, which are transfer units of asynchronous transfer mode, ATM, are grouped together to form a fixed length TDMA burst.
In a satellite communication system that realizes an arbitrary transmission rate by making the number of transmissions of MA burst per frame variable according to the transmission rate, a transmitting earth station connects a cell transferred from a terrestrial ATM communication network to a line. VPI / VCI indicating the destination of communication in the header of the cell designated in advance by the control station
Means for accommodating into the transmission buffer, accommodating in at least one TDMA burst designated by the line control station for each classified cell group, and transmitting to a communication satellite, and the number of input cells per cell group And a means for measuring the queue length, and means for transferring the measured number of input cells and the queue length to the line control station, and the receiving earth station receives the TDMA burst from the communication satellite, Based on the VPI / VCI in the header of the cell designated in advance by the control station, only the cell addressed to the own station is taken out and has means for transferring to the terrestrial ATM network. Necessary from means for transferring information for classifying by VPI or VCI in the header, means for receiving the number of input cells for each cell group from the transmitting earth station, and number of input cells for each received cell group. satellite A means for predicting the bandwidth of the line, a means for allocating satellite channels based on the means, and a means for transferring the changed satellite channel allocation information to the transmitting earth station, and a VPI / VCI in the header of the cell to be taken out by the receiving earth station. The satellite communication system has means for transferring information to the receiving earth station.

[0006]

FIG. 1 shows an embodiment of the present invention. In FIG. 1, 100 is a transmitting earth station, 200 is a communication satellite, 300 is a line control station, and 400 is a receiving earth station. The transmitting earth station 100 sends the cell input from the terrestrial ATM communication network to the V in the header of the cell designated in advance by the line control station 300.
A function of classifying each PI or VCI and accommodating it in a transmission buffer, and a function of accommodating each classified cell group in one or a plurality of TDMA bursts designated by the line control station 300 and transmitting it to the communication satellite 200. And a function of measuring the number of input cells for each cell group, and a function of transferring the measured number of input cells and the queue length to the line control station, and the receiving earth station 400 receives from the communication satellite 200. It has a function of receiving a TDMA burst, extracting only the cell addressed to itself from the line control station 300 based on the VPI or VCI in the header of the cell designated in advance, and transferring it to the terrestrial ATM network. Reference numeral 300 denotes a function of transferring information for classifying each VPI or VCI in a header of a cell in the transmitting earth station 100, and an input for each cell group from the transmitting earth station 100. The function of receiving the number of channels, the function of predicting the required bandwidth of the satellite channel from the number of input cells for each received cell group, satellite channel allocation based on this, and the changed satellite channel allocation information The function of transferring to the station 100 and the VPI or VCI information in the header of the cell extracted by the receiving earth station 400 are received by the receiving earth station 40.
It has the function of transferring to 0.

FIG. 2 shows the transmitting earth station 1 shown in FIG.
00 is a detailed configuration. In FIG. 2, the cell input to the transmitting earth station 100 from the terrestrial ATM communication network reads the VPI or VCI portion in which the cell destination information included in the cell header portion is recorded by the switch unit 101 and
The I / VCI table 102 is referred to, and each VPI group or VCI group is separated. This VPI group or VC
The cells separated for each I group are measured by the cell number counter 103, and the input cell number information is collectively output as the input traffic variation information in the cell number information creating circuit 110. On the other hand, the information cell is temporarily stored in the buffer memory 10
4, the selector 105 is switched by the TDMA burst configuration map 111 that manages the burst configuration in the TDMA frame, and the synthesis / separation circuit 106 and the TDMA circuit 10 are switched from the buffer memory for each TDMA burst.
7, the RF circuit 108, and the antenna 109 to transmit to the communication satellite 200 of FIG. The synthesis / separation circuit 1
Reference numeral 06 denotes the line control station 300 via the communication satellite 200.
The TDMA burst configuration map 11 transmitted from
1, rewrite information of the VPI / VCI table 102 is separated from the signal from the TDMA circuit 107,
It has a function of inputting to the burst configuration map 111 and the VPI / VCI table 102. The TDMA burst configuration map 111 and the VPI / VCI table 102 have a function of rewriting the map or the table based on these information. Also, the cell number information creation circuit 110
The input cell number information from the TD is combined with the communication signal from the selector 105 by the combining / separating circuit 106, and the TD
MA device 107, RF circuit 108, antenna 10
9. Transmitted to the line control station 300 via the communication satellite 200.

FIG. 3 shows the receiving earth station 4 shown in FIG.
00 is a detailed configuration. In FIG. 3, the receiving earth station 4
00, the TDMA burst received via the communication satellite 200 is received by the receiving antenna 407 and the RF circuit 40.
6, input to the switch unit 403 via the TDMA circuit 405 and the combining / separating circuit 404. The switch unit 403 reads the VPI or VCI portion in which the destination information of the cell included in the header portion of the input cell is recorded, and VPI /
By referring to the VCI table 402, only the cell having the VPI or VCI addressed to itself is output to the terrestrial ATM communication network via the buffer memory 401. The synthesizing / separating circuit 404 described above uses the line control station 3 via the communication satellite 200.
00 has a function of separating the rewrite information of the VPI / VCI table 402 from the output signal of the TDMA circuit 405 and inputting it to the VPI / VCI table 402. The VPI / VCI table 402 has a function of rewriting the table based on this information.

FIG. 4 is a circuit control station 3 shown in FIG.
00 is a detailed configuration. In FIG. 4, the line control device 300 includes the communication satellite 200, an antenna 308, an RF circuit 307, a TDMA circuit 306, a combining / separating circuit 305.
A cell number information management table 304 for managing the input cell number information from the above-mentioned transmitting earth station 100 received via
It has a VPI / VCI table 302 for managing the VPI and VCI assigned to the transmitting earth station and the receiving earth station, and a band management table 303 for managing the satellite channel assignment information assigned to each transmitting earth station. The bandwidth control circuit 301 uses the input cell number information of the cell number information management table 304 and the bandwidth management information of the satellite line allocated to each transmission earth station of the bandwidth management table 303 to determine the queue in the buffer of each transmission earth station. It has a function of calculating the length and obtaining a satellite line to be allocated to each transmitting earth station by the band control algorithm shown in FIG. Here, as shown in FIG. 5, the information on the number of input cells from the transmitting earth station is transmitted once per frame (usually about 20 ms) per transmitting earth station, or about several times by parallel transmission considering the bit error of the satellite line. Be received. On the other hand, the control interval T _d of the satellite line is controlled once every several hundred ms in consideration of the propagation delay between the line control station-satellite-transmitting earth station.

The control algorithm shown in FIG. 6 will be described below by taking the satellite channel allocation control at time T ₁ ′ in FIG. 5 as an example. In FIG. 6, the band control circuit 301 uses the input cell number information W _in from the transmitting earth station 100 and the satellite channel information W _s assigned to the transmitting earth station 100 from the band management table 303 to transmit according to equation (1). Earth station 10
From the time T _{0 when the} number of input cells of 0 is measured to T ₁ (however, T
Queue length QL (T ₀ , T generated until ₀ <T ₁ ).
₁ ) is calculated (500).

[0011]

[Equation 1]

When the queue length QL (T ₀ , T ₁ ) is 0 and (W _in (T ₁ ) −W _s (T ₁ )) at time T ₀ is 0 or less (504), satellite line allocation is performed. Is not changed (510). This queue length QL (T ₀ , T ₁ ) is the prediction error of the required satellite channel allocation band at time T ₀ ′. On the other hand, the queue length _{QL (T 0, T 1)} ( in greater than or when the time T _{0 0} W _in (T
_{If 1} ) −W _s (T ₁ )) is greater than 0, the satellite channel allocation is changed according to the equation (2) (506).

[0013]

[Equation 2]

In the equation (2), the first term on the right side is the satellite line necessary for outputting the cells accumulated in the buffer memory 104 of the transmitting earth station between time T ₀ and T ₁ within the time T _c1 . a capacitor, the second term of the right side is a satellite link capacity required for outputting a cell that is expected to accumulate in between time T _2, after the control delay T _d from the time T ₁ within the time T _c2 . Therefore, the maximum cell delay can be controlled by appropriately selecting the times T _c1 and T _c2 . Here, in the formula (2), linear prediction based on the input cell number information at time T ₁ is used, but it is naturally possible to perform prediction using a plurality of input cell number information measured before. Is. The control algorithm of FIG. 6 is configured so that the minimum allocated bandwidth can be set in order to cope with the sudden increase in the number of input cells (508, 512, 514).

In the present embodiment, one transmission / reception control station is described as an example for simplification of description, but similar control is performed in parallel even when a plurality of transmission / reception earth stations are included. It is obvious that the bandwidth allocation control can be performed by executing it. In addition, in this embodiment,
Satellite lines are used for TDMA burst configuration map, VPI / VCI table rewriting control, and cell number information transfer, but some or all of these control lines are implemented using the terrestrial communication network. Even in the case, the same effect can be obtained.

[0016]

As described above, the input cell is set to V in the header of the cell designated in advance by the line control station.
The satellites are classified according to PI or VCI, and a plurality of cells are grouped into each classified cell group to form a TDMA burst. At the line control station, satellites required from the number of input cells for each cell group input to the transmitting earth station are required. By predicting the bandwidth of the line and performing TDMA burst allocation based on this, high-speed data communication with a large maximum value of traffic and extremely high burstiness can be used for satellite communication with high line utilization efficiency while guaranteeing the maximum cell delay. Can be accommodated in

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an exemplary embodiment of the present invention.

2 is a block diagram showing a detailed configuration of a transmitting earth station 100 of FIG.

3 is a block diagram showing a detailed configuration of a receiving earth station 400 of FIG.

4 is a block diagram showing a detailed configuration of a line control station 300 of FIG.

5 is a diagram showing an example of exchange of input cell number information and satellite line allocation control information between the transmitting earth station 100 and the line control station 300. FIG.

FIG. 6 is a diagram showing a band control algorithm.

[Explanation of symbols]

 100 transmitting earth station 101 switch section 102 VPI / VCI table 103 cell number counter 104 buffer memory 105 selector 106 combining / separating circuit 107 TDMA circuit 108 RF circuit 109 antenna 110 cell number information creating circuit 111 TDMA burst configuration map 200 communication satellite 300 line Control station 301 Band control circuit 302 VPI / VCI table 303 Band management table 304 Cell number information management table 305 Combining / separating circuit 306 TDMA circuit 307 RF circuit 308 Antenna 400 Reception earth station 401 Buffer memory 402 VPI / VCI table 403 Switch unit 404 Synthesis / separation circuit 405 TDMA circuit 406 RF circuit 407 Receiving antenna

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location 7240-5K H04L 13/00 307C

Claims (1)

[Claims] 1. A fixed-length TDMA burst is formed by collecting a plurality of cells, which are transfer units of asynchronous transfer mode, ATM, and the number of transmissions of this TDMA burst per frame is variable according to the transmission speed. In this way, in the satellite communication system that realizes an arbitrary transmission rate, the transmitting earth station indicates the cell transferred from the terrestrial ATM communication network, and indicates the communication destination in the header of the cell designated in advance by the line control station. Means for classifying into VPI / VCI and accommodating in a transmission buffer; means for accommodating at least one TDMA burst designated by the circuit control station for each classified cell group and transmitting to a communication satellite; and The receiving earth station has means for measuring the number of input cells and the queue length, and means for transferring the measured number of input cells and the queue length to the line control station, The line control station has means for receiving the TDMA burst, extracting only the cell addressed to the own station based on the VPI / VCI in the header of the cell designated in advance from the line control station, and transferring the cell to the terrestrial ATM network. A means for transferring information for classifying by VPI or VCI in a cell header in the transmitting earth station, a means for receiving the number of input cells for each cell group from the transmitting earth station, and a received cell group A means for predicting a required satellite line band from the number of input cells for each, a satellite line allocation based on this, a means for transferring the changed satellite line allocation information to the transmitting earth station, and a receiving earth station A satellite communication system comprising means for transferring VPI / VCI information in the header of a cell to be extracted to the receiving earth station.