THE PERFORMANCE ANALYSIS OF HIGH DIMENSIONAL TRELLIS-CODED MODULATION FOR SPREAD SPECTRUM COMMUNICATIONS

The performance analysis of a new coding and modulation scheme, called high dimensional trellis-coded modulation (HDTCM), for spread spectrum communications is presented.

Coding and modulation are two indispensable parts in any digital communications system. In the conventional digital communications systems, coding and modulation are two separate, sequential processes. The coding gain is achieved with the sacrifice of bandwidth expansion.

Conventional trellis-coded modulation (TCM) is to combine modulation and coding as one single process so that coding gain can be achieved without bandwidth expansion. Instead, the coding gain is achieved at the expense of decoder complexity.

The proposed HDTCM integrates a block code, instead of convolutional codes, and a expanded bi-orthogonal signaling set by using a state-constrained trellis structure. The HDTCM scheme is an integration of not only coding, modulation, but also the signal spreading as one single entity.

The properties of the HDTCM scheme is investigated. First, the uniformity property of Euclidean distance is shown. Next, the theoretical performance of HDTCM is analyzed by giving the analytical expressions of lower bound and upper bound. Then the asymptotic upper bound is discussed. Finally, the coding gain over the uncoded conventional spread spectrum systems is given.