Pulse or digital communications – Systems using alternating or pulsating current – Plural channels for transmission of a single pulse train
Reexamination Certificate
1999-01-20
2001-03-13
Ghebretinsae, Temesghen (Department: 2631)
Pulse or digital communications
Systems using alternating or pulsating current
Plural channels for transmission of a single pulse train
Reexamination Certificate
active
06201836
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method and apparatus for combining a Trellis coding scheme with a pre-coding scheme for data signals.
BACKGROUND OF THE INVENTION
FIG. 1
illustrates how V.34 modems combine a pre-coding scheme with a four-dimensional Trellis coding scheme. As shown in
FIG. 1
, only the signal y(n), not u(n), must have Trellis code properties (i.e., y(n) should be Trellis code sequence) since it is the signal received by the receiver and decoded by the Trellis decoder. V.34 modems make y(n) to be a Trellis code sequence by making sure that u(n) is a Trellis sequence and u(n) (precoder input) and y(n) (precoder output) is in the same four-dimensional (4D) family as defined in L. F. Wei, “
Trellis
-
Coded modulation with Multidimensional Constellations
,” IEEE Trans. on Information Theory, vol. 33, no. 4, July 1987. As long as u(n) and y(n) are in the same four-dimensional family, making u(n) a Trellis sequence guarantees that y(n) is also a trellis sequence.
Current state-of-the-art V.90 modems use a faster (56 kbps) pulse code modulation (PCM) coding scheme for downstream transmission and the slower (33.6 kbps) V.34 coding scheme for upstream transmissions. Upstream PCM transmission would employ a different pre-coding scheme, and therefore the technique used for V.34 can no longer be used.
Thus, a need exists for a method and apparatus for combining a Trellis coding scheme with a pulse code modulation transmission for lower error probability at a given upstream transmission rate.
REFERENCES:
patent: 5199046 (1993-03-01), Ling
patent: 5488633 (1996-01-01), Laroia
L.F. Wei; “Trellis-Coded Modulation with Multidimensional Constellations” IEEE Trans. On Information Theory, vol. 33, No. 4, Jul. 1987.
N. Al-Dhahir, et al. “Efficient Computation of the Delay Optimized Finite Length MMSE-DFE” IEEE Transactions on Signal Processing; vol. 44, No. 5, May 1996, pp. 1288-1292.
ITU-T Blue Book; “Pulse Code Modulation (PCM) of Voice Frequencies”; ITU-T Recommendation G.711; 1993.
V.34 Standard.
R. Laroia, “Coding for Intersymbol Interference Channels—Combined Coding and Precoding”, IEEE Trans. on Information Theory, vol. 42, No. 4, Jul. 1996, pp. 1053-1061.
Ghebretinsae Temesghen
Motorola Inc.
Pappas Joanne N.
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