Multiplex communications – Data flow congestion prevention or control – Control of data admission to the network
Patent
1996-07-18
1999-05-11
Olms, Douglas W.
Multiplex communications
Data flow congestion prevention or control
Control of data admission to the network
370235, 375262, 375265, 371 431, H04J3/22
Patent
active
059035463
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a signal transmitting apparatus, a signal receiving apparatus, and a method for the same used for transmitting data of a digital format via a transmission channel such as a wireless line.
BACKGROUND ART
Where data of a digital format is transmitted via a communication channel (transmission channel) in which data error (transmission error) is liable to occur, in general, a method of transmitting the data after performing a predetermined encoding on the data to be transmitted.
For example, where data is transmitted via a wireless channel, particularly, where data is transmitted via a satellite communication channel, the strength of the received signal (signal level) at the reception side becomes very low, so data error is liable to occur. Further, even in a case where data is transmitted via a communication channel using a ground wave (ground wave communication channel), the reception level becomes low at the region at the end of the service range, so data error becomes liable to occur.
Accordingly, where the data to be transmitted is encoded with a high compression rate by the high-efficient coding method, it is necessary to take strict countermeasures against data error at the step of decoding on the reception side.
For example, in the decoding on the reception side, there is a case where data other than the data in which the data error occurs is affected (data error is propagated). In such a case, it is particularly necessary to take strict countermeasures against data error.
Due to the above situation, when transmitting data via a satellite communication channel, since the carrier-to-noise ratio (C/N ratio) of the reception signal becomes small, in general, after the data of the digital format to be transmitted is encoded using a block code such as a Reed-Solomon code, it is further encoded for correction of transmission line error by convolutional coding to generate a transmission line code.
The method has been adopted of transmitting the transmission line code subjected to countermeasures against data error in this way via the communication line after modulation by QPSK modulation method etc.
On the other hand, in a ground wave communication line in which a C/N ratio of the reception signal better than that of a satellite communication line is obtained, to raise the transmission efficiency, data is frequently transmitted by modulating the transmission code by a multi-value modulation method such as a 16-QAM or 32-QAM method.
Further, recently, as a transmission line coding system combining error correction technology and modulation technology, code modulation systems are now being used. Among the code modulation systems, one using a Trellis code as the error correction code is referred to as the Trellis code modulation (TCM) system.
In general, a method using an error correction code for the transmission of data has the characteristic that when the encoding rate is made small, that is, when the ratio between the amount of information to be transmitted and the amount of information actually transmitted on the communication line is made small, the error correction capability becomes high, but the transmission efficiency (throughput) of the digital information to be transmitted is lowered, and conversely when the encoding rate is made large, the throughput becomes large, but the error correction capability becomes low.
On the other hand, transmission of data via a satellite communication line has the characteristic that the level of reception fluctuates greatly according to the gain of the reception antenna or the weather conditions.
Further, transmission of data via a ground wave communication line has the characteristic that the level of reception fluctuates according to the positional relationship between the transmission side and the reception side. That is, where the reception side is at an area near the transmission side, the level of reception becomes high, but when the reception side is at an area distant from the transmission side, the level of
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patent: 4881241 (1989-11-01), Pommier et al.
patent: 5258987 (1993-11-01), Wei
patent: 5278826 (1994-01-01), Murphy et al.
patent: 5673291 (1997-09-01), Dent
Ikeda Tamotsu
Ikeda Yasunari
Okada Takahiro
Frommer William S.
Hom Shick
Olms Douglas W.
Sony Corporation
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