Performance Analysis of TCM Waveforms Transmitted over a Channel with Pulse-Noise Interference

Trellis-coded modulation (TCM) is a technique that introduces forward error correction coding without increasing the bandwidth of the channel signal. TCM combines binary convolutional codes with M-ary modulation in one operation. The waveform is assumed to be transmitted over a channel with both additive white Gaussian noise (AWGN) and pulse-noise interference (PNI). In addition to a TCM waveform consisting of a rate r = 2/3 convolutional code with 8-phase-shift keying (8-PSK) modulation (analogous to the IEEE 802.11g TCM mode) and a TCM system consisting of two rate r = 1/2 convolutional codes encoding data that is modulated on the inphase and quadrature channels, respectively, with 4-pulse amplitude modulation (4-PAM) is examined. As compared to an r = 2/3, 8-PSK TCM system, the decoding complexity of the r = 1/2, 4-PAM TCM system is significantly less when the number of encoder memory elements is large. For both TCM systems, the effect of varying the number of encoder memory elements when PNI is present is examined. It is found that as the number of encoder memory elements increases the negative effect of PNI decreases. When the total number of memory elements in the r = 1/2, 4-PAM TCM system is twice that of the r = 2/3, 8-PSK TCM system (each r = 1/2 encoder has the same number of memory elements as the r = 2/3 encoder), the r = 1/2, 4-PAM TCM system has better immunity to PNI than the r = 2/3, 8-PSK TCM system.