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Trellis-Coded Modulation

Trellis-coded modulation (TCM) is a baseband modulation technique in which the message modulates the phase of a constant amplitude signal. The transmitted signal is created by convolutionally encoding the binary input signal and mapping the result to a signal constellation. At the receiver, the modulated signal uses the Viterbi algorithm to decode TCM modulated signals.

Communications Toolbox™ software includes these modulation and demodulation System objects and blocks to model general TCM, M-PSK TCM, and rectangular QAM TCM.

General QAM TCM

The general TCM method convolutionally encodes the binary input signal and maps the result to an arbitrary signal constellation. The signal constellation parameter lists the signal constellation points in a set-partitioned order complex vector with a length, M, equal to the number of possible output symbols from the convolutional encoder. For a rate k/n convolutional code, n is equal to log2(M).

PSK TCM

The PSK TCM method convolutionally encodes the binary input signal and maps the result to an PSK signal constellation. The modulation order (or M-ary number), M, is the number of possible output symbols from the convolutional encoder. For a rate k/n convolutional code, n is equal to log2(M).

Rectangular QAM TCM

The rectangular QAM TCM method convolutionally encodes the binary input signal and maps the result to an QAM signal constellation. The modulation order (or M-ary number), M, is the number of possible output symbols from the convolutional encoder. For a rate k/n convolutional code, n is equal to log2(M).

References

[1] Biglieri, E., D. Divsalar, P.J. McLane, and M.K. Simon, Introduction to Trellis-Coded Modulation with Applications, New York, Macmillan, 1991.

[2] Proakis, John G. Digital Communications. 5th ed. New York: McGraw Hill, 2007.

[3] Ungerboeck, G., “Channel Coding with Multilevel/Phase Signals”, IEEE Trans. on Information Theory, Vol IT28, Jan. 1982, pp. 55–67.

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