JPH06112874A - Satellite communication system - Google Patents

Abstract

PURPOSE:To communicate high quality data by measuring a transmission error rate equivalent to a bit error rate, deciding number of consecutive transmission of a packet and user data length in response to the line quality and adding the information to a header part and sending the resulting data. CONSTITUTION:A packet UD is added to a base band signal 201 at a packet generation control circuit 211 and the result is transferred to a transmission circuit 212 according to a packet timing generated by the timing signal generator 211. In this case, the packet size or the length of the user data is controlled according to transmission error rate information 204 measured by a reception circuit 213. The circuit 212 converts the signal into an intermediate frequency signal and the signal is sent to a satellite via a high frequency section 216. The circuit 213 converts the signal into a base band signal 205 and the signal is transferred to a packet decomposition composition circuit 214. The circuit 214 eliminates a header and a footer part from the packet received and composes the original user data to the result and transfers it to a data buffer 215. A host terminal of a center station C receives the data via a buffer 215.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a satellite communication system in which at least one transmitting station and a plurality of small reception dedicated stations are connected via a satellite line.

[0002]

2. Description of the Related Art Conventionally, in a one-way communication system using a satellite communication system, when performing data transmission, there is no means for notifying the sender that the received data is erroneous. Redundant bits are added and transmitted, and the receiving side corrects the error. Further, the same information is repeatedly transmitted, and the received data is compared and selected so that only normal data is used.

[0003]

However, when data transmission is performed in a satellite communication system, the bit error rate is used as a measure for evaluating the line quality. However, when the line quality deteriorates and the bit error rate increases, Even if such an error correction method as described above is used, there is a problem in that it cannot be reproduced.

Another feature of satellite communication is that a burst error occurs. When this burst error causes continuous bit errors, it is possible to prevent information loss due to the burst error by transmitting the same data several times. However, when packets are similarly sent continuously even when the line quality is high, the satellite line is unnecessarily used, and there is a problem that the communication efficiency decreases.

An object of the present invention is to provide a satellite communication system capable of efficiently using a satellite line and communicating high quality data according to the line quality.

[0006]

In order to achieve the above object, the satellite communication system of the present invention is a satellite communication system in which at least one transmitting station and a plurality of small reception dedicated stations are connected via a satellite line. In the transmitting station, when performing one-way communication to a receiving means equipped with a circuit for measuring a transmission error rate by receiving a signal from a satellite repeater used by the transmitting station, and performing one-way communication to a small dedicated reception station. A circuit for changing the number of consecutive transmissions of the packet and the user data length according to the information of the transmission error rate measured by the receiving means and adding the number of consecutive transmissions of the packet and the user data length to the header portion of the packet. The small dedicated reception station is provided with a receiving means having a circuit for extracting the number of continuous packet transmissions and the user data length from the header portion of the received packet.

[0007]

According to the above means, when transmitting a packet, the transmitting station receives the signal from the satellite repeater (transponder) used by the transmitting station, measures the transmission error rate equivalent to the bit error rate, and determines the line quality. The number of continuous packet transmissions and the user data length are determined according to the above. Then, the information on the number of continuous packet transmissions and the user data length is added to the header portion of the packet and transmitted.

On the receiving side, the header portion of the packet is analyzed and the number of continuous transmissions of the packet and the user data length are known to compare and select the packet and only normal data is received.

As a result, the satellite line can be used efficiently and high quality data can be communicated.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to illustrated embodiments.

FIG. 1 is an overall configuration diagram showing an embodiment of a satellite communication system according to the present invention. In the figure, C is a central station, to which a host terminal (not shown) is connected.
R1 to Rn are small receiving stations. A user terminal (not shown) is connected to these R1 to Rn. S is a satellite.

The central station C and the small reception dedicated station R communicate with each other via a satellite S. Reference numeral 101 is an outbound line from the central station C to the small reception dedicated station R.

FIG. 2 is a block diagram showing the configuration of the central station C, 201 is a baseband signal from the host terminal,
210 is a timing signal generator, 211 is a packet generation control circuit, 212 is a transmission circuit, 213 is a reception circuit, 21
4 is a packet disassembling / combining circuit, 215 is a data buffer, and 216 is a high frequency unit.

The timing signal generator 210 supplies a timing signal for transmitting the packet UD shown in FIG. 3 to the packet generation control circuit 211.

The packet generation control circuit 211 uses the data DATA input from the host terminal side as the baseband signal 201 to generate a flag sequence F indicating the beginning of the packet UD shown in FIG. 3, an address portion ADR, a control portion CTR, and a packet number. PN, continuous transmission number RN, user data size SIZE, frame check sequence FC
S, a flag sequence F indicating the end of the packet is added and transferred to the transmission circuit 212 in accordance with the packet timing generated by the timing signal generator 210.

At this time, the packet size or the length of the user data is controlled according to the transmission error rate information 204 measured by the receiving circuit 213.

Further, according to the frame timing shown in FIG. 3, a packet FTC for performing frame timing and control is transmitted to the head of the frame.

The transmission circuit 212 is a packet generation control circuit 2
The baseband signal from 11 is converted into the intermediate frequency band signal 20
It is converted into 2 and supplied to the high frequency section 216.

The high frequency section 216 is provided with the intermediate frequency band signal 202.
Is converted into a high frequency band signal and transmitted to the satellite S. Further, the high frequency unit 216 receives a signal from the satellite S, converts the signal into the intermediate frequency band signal 203, and supplies the intermediate frequency band signal 203 to the reception circuit 213.

The receiving circuit 213 converts the intermediate frequency band signal 203 from the high frequency section 216 into a base band signal 205 and transfers it to the packet disassembling / combining circuit 214. Also,
The reception circuit 213 statistically measures the transmission error rate of the frequency, and supplies the transmission error rate information 204 that is the measurement result to the packet generation control circuit 211.

The packet disassembling / combining circuit 214 removes the header part and the footer part from the received packet, combines the original user data, and transfers it to the data buffer 215.

The host terminal of the central station C is the data buffer 2
Data is received via 15.

FIG. 3 is a frame structure and packet structure diagram, and one frame is composed of n packets UD and FTC packets. The FTC packet is a packet used for frame timing and control, and is placed at the beginning of the frame. Packet UD has flag sequence F
It is represented by a bit string surrounded by.

The structure of the packet UD is ADR, CTR, P
It consists of N, RN, SIZE, DATA and FCS. AD
R is an address part, CTR is a packet control part, and PN is a packet number. The PN is constant while continuously transmitting DATA having the same content. RN indicates the number of times of continuously transmitting DATA having the same content. SIZE indicates the size of user data. DATA is user data. FCS is a frame check sequence.

FIG. 4 shows the packet arrangement on the frame when the packet size length and the user data size length are changed according to the transmission error information.

The line quality is classified into phase 1, phase 2, phase 3 and phase 4. The line quality is measured by measuring the transmission error rate by the receiving circuit 213, and the phase number increases as the transmission error rate increases.

In phase 1, one user data is transmitted in one packet. Phase 1 is the most efficient way to send user data.

In phase 2, the user data is divided into m packets UD1 to UDm, multiplexed on one frame and transmitted.

In phase 3, k frames having the same contents as in phase 2 are continuously transmitted. Here, k corresponds to the number of continuous packet transmissions.

In phase 4, the packet of phase 3 is further divided into n packets. Phase 4 has the lowest transmission efficiency, but the packet length is short and arrival probability is high when the transmission error rate is low.

FIG. 5 is a block diagram showing a configuration of the small reception dedicated station R. The reception circuit 510 and the packet selection circuit 5 are shown in FIG.
11, a packet buffer 512, a packet disassembling / combining circuit 513, and a data buffer 514.

The receiving circuit 510 receives the intermediate frequency band signal 501.
Is converted into a baseband signal 502 and supplied to the packet buffer 512. The packet buffer 512 supplies the packet normally received under the control of the packet selection circuit 511 to the packet disassembly / combination circuit 513.

The packet disassembling / combining circuit 513 removes the header and footer parts of the packet received from the packet buffer 512, combines the original user data, and supplies it to the data buffer 514. The user terminal receives data via the data buffer 514.

The packet selection circuit 511 compares the packet number PN of the packet arriving at the packet buffer 512, the number of consecutive transmissions RN, the user data size SIZE, the user data DATA, and the frame check sequence FCS to control the selection of the received packet. The packet buffer 51 outputs a packet selection control signal 503 for supplying only normal packets to the packet disassembly / combination circuit 513.
Notify 2.

As a result, only normal packets are transferred to the user terminal.

Although the above embodiment has described the case of performing communication between one central station and a plurality of small dedicated reception stations, the present invention is not limited to this, and one or more of them may be used. The same can be applied to the case where communication is performed between the transmitting station and the small reception-only station, or to a system where bidirectional communication is performed via the satellite S.

[0037]

As described above, according to the present invention, when the transmitting station transmits a data packet, the transmission error rate is measured by receiving the signal of the transponder, and the number of consecutive packet transmissions, the user The data length is changed and transmitted, and the receiving side selects and receives a normal packet without making a retransmission request, so at low transmission error rates, continuous transmission and packet division are used to increase the probability of arrival. , High quality communication is possible. When the line quality is high, one user data is transmitted in one packet, so that the line can be effectively used.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram showing an embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of a central station C in FIG.

FIG. 3 is a frame configuration diagram and a packet configuration diagram in FIG. 1.

FIG. 4 is an explanatory diagram showing a packet arrangement on a frame when the packet size length and the user data size length are changed according to the transmission error rate.

5 is a block diagram showing a configuration of a small reception dedicated station R in FIG.

[Explanation of symbols]

C ... Central station, S ... Satellite, R1 to Rn ... Small reception dedicated station,
101 ... Outbound line, 201, 205 ... Baseband signal, 202, 203 ... Intermediate frequency band signal, 20
4 ... Transmission error rate information, 210 ... Timing signal generator,
211 ... Packet generation control circuit, 212 ... Transmission circuit, 2
13 ... Receiving circuit, 214 ... Packet decomposing / combining circuit, 2
15 ... Data buffer, 216 ... High frequency section, FTC ... Frame timing and control section, F ... Flag sequence, A
DR ... Address part, CTR ... Control part, PN ... Packet number, RN ... Number of consecutive times, SIZE ... User data size, DATA ... User data, FCS ... Frame check sequence, 501 ... Intermediate frequency band signal, 50
2 ... Baseband signal, 503 ... Packet selection control signal, 510 ... Reception circuit, 511 ... Packet selection circuit, 5
12 ... Packet buffer, 513 ... Packet disassembling / combining circuit, 514 ... Data buffer.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shinsaku Okamura 1-26-5 Toranomon, Minato-ku, Tokyo NTT Data Communications Corporation

Claims (1)

[Claims] 1. A satellite communication system in which at least one transmitting station and a plurality of small dedicated reception stations are connected via a satellite line, wherein the transmitting station is a signal of a satellite repeater used by itself. Receiving means provided with a circuit for measuring the transmission error rate in response to the received data and the one-way communication to the small dedicated reception station, based on the information of the transmission error rate measured by the receiving means, the number of consecutive packet transmissions and the user. And a transmitting means provided with a circuit for changing the data length and adding the number of continuous transmissions of the packet and the user data length to the header portion of the packet, wherein the small dedicated reception station includes the header portion of the received packet. A satellite communication system characterized by further comprising receiving means provided with a circuit for extracting only normal packets by referring to the number of continuous packet transmissions and the user data length.