A COMPARISON OF 2 COMBINING TECHNIQUES FOR EQUAL GAIN, TRELLIS-CODED DIVERSITY RECEIVERS

Trellis coded modulation is widely used for digital transmission over fading channels, Classical diversity techniques are also frequently em ployed to combat fading, In this paper two different strategies for eq ual gain combining are compared. One scheme is based on an interleaved code combining technique, The alternative scheme is based on averaged diversity combining, The well known transfer function bounding techni que for trellis codes is used to obtain expressions for the bit error rate performance of the two trellis coded diversity receivers over a s lowly fading Rayleigh channel, The analysis of interleaved code combin ing is a straightforward modification of the analysis for multiple tre llis coded modulation. The analysis of averaged diversity combining is accommodated through a more involved, novel modification of the branc h labeling of the error state diagram. The analytic techniques present ed in this paper are supported by simulation results using a TCM schem e based on QPSK modulation and a rate-1/2 linear convolution code.