Error detection/correction and fault detection/recovery – Pulse or data error handling – Digital data error correction
Patent
1998-02-13
2000-04-18
Baker, Stephen M.
Error detection/correction and fault detection/recovery
Pulse or data error handling
Digital data error correction
375265, H03M 1312
Patent
active
060528214
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to a selective protection digital transmission system comprising a transmitter and a receiver, the transmitter including first convolutional coding means for coding data, second coding means for applying a coding by puncturing and means for allocating the coded data to digitally modulated symbols.
The invention likewise relates to a transmitter and a receiver used in such a system and to a selective protection method. The system may be used for digital transmission for cable television, satellite television or others.
BACKGROUND OF THE INVENTION
Such a system comprises sources which produce various bit streams which it is to protect differently against the errors due to imperfections of the transmission channel. The tolerated error rate depends on each bit stream. For example, a source may produce three bit streams which it is to transmit with the respective maximum error rates of 10.sup.-4, 10.sup.-7 and 10.sup.-11.
A customary method for having a selective protection comprises utilizing different codes for each bit stream. The transmitted signal is then obtained by a time-division multiplexing of the various coded signals coming from various bit streams. For example, error correction codes may be used whose correction capacity is adjusted as a function of the required error rate. This approach has two drawbacks: much hardware complexity; optimum performance in terms of error rate as a function of the signal-to-noise ratio. For an error rate and a fixed rate, the signal-to-noise ratio is not minimized.
The first drawback has been suppressed in the systems utilizing the punctured codes described in the article: "Rate-compatible punctured convolutional codes (RCPC codes) and their applications", IEEE Transactions on Communications, J. Hagenauer, vol. 36, No. 4, April 1988, pp. 389-399. The principle consists of utilizing a single convolutional code (called mother code) having a 1/2 rate or 1/3 rate, the same for all the bit streams, and of applying a different punctured coding for each stream. The punctured coding consists in this article of periodically prohibiting the transmission of certain bits as a function of a matrix, called puncturing matrix. Thus, the rate of the punctured coding becomes higher than that of the non-punctured coding. This document relates to PSK2 or PSK4 phase modulations.
At the receiving end, the decoding is performed by computing metrics of the symbols received in the baseband coming from each bit stream. The computation of the metrics depends on the puncturing matrix, thus on the bit stream. The transmitted bits are estimated by a Viterbi decoder shared for the processing of all the signals that correspond to the various bit streams.
The drawback of the codes having a 1/2 rate is that they are only adapted to low-efficiency spectral modulations (less than or equal to two bits/s/Hz) as PSK2 and PSK4 phase modulations. Corresponding to these modulations is a bit rate equal to the maximum of twice the band used. For increasing the rate for a fixed seized band, one could seek to utilize high-efficiency spectral modulations of the QAM type (Quadrature Amplitude Modulation). But the use of the punctured convolutional codes having a 1/2 rate described by J. Hagenauer placed side by side with QAM modulations does not yield optimum performance, because these codes have been devised independently of the modulation.
SUMMARY OF THE INVENTION
It is thus an object of the invention to enhance the performance of such a transmission system by guaranteeing a correct operation of the system with a minimum signal-to-noise ratio by improving the spectral efficiency of the system.
This object is achieved with a system in which the first coding means provide a convolutional trellis coding having an N/2N rate, where N is an integer greater than 1, while the convolutional coding is combined with a 2.sup.2N -state quadrature amplitude modulation and the puncturing coding is applied to the symbols.
The invention likewise relates to a transmitter and a re
REFERENCES:
patent: 5408502 (1995-04-01), How
patent: 5555547 (1996-09-01), Lemaitre et al.
Viterbi et al., "A Pragmatic Approach to Trellis-Coded Modulation", IEEE Communications Magazine, Jul. 1989, pp. 11-19.
Wolf et al., "P2 Codes: Pragmatic Trellis Codes Utilizing Punctured Convolutional Codes", IEEE Communications Magazine, Feb. 1995, pp. 94-99.
PCT International Search Report, PCT/IB97/00756, Sep. 1997.
Eroz et al., "A Multiple Trellis-Coded Hybrid ARQ Scheme for Land-Mobile Communication Channels", Proc. MILCOM Nov. 1995, pp. 496-500.
Kim et al., "On Puncture Trellis-Coded Modulation", Proc. ICC, Jun. 1995, pp. 678-682.
Cremonesi et al., "An Adjustable-Rate Multilevel Coded Modulation System: Analysis and Implementation", European Transactions on Telecommunications and Related Technologies, vol. 4, No. 3, May 1993, pp. 277-283.
Jung-Fu et al., "Complexity-Reduced Multilevel Coding with Rate-Compatible Punctured Convolutional Codes", Proc. GLOBECOM, Nov. 1993, pp. 814-818.
"Rate-compatible punctured convolutional codes (RPC codes) and their applications", IEEE Transactions on Communications, J. Hagenauer, vol. 36, No. 4, Apr. 1998, pp. 389-399.
Brajal Americo
Chouly Antoine
Gianella David
Baker Stephen M.
Eason Leroy
U.S. Philips Corporation
LandOfFree
Trellis coded QAM using rate compatible, punctured, convolutiona does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Trellis coded QAM using rate compatible, punctured, convolutiona, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Trellis coded QAM using rate compatible, punctured, convolutiona will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2345947