Circular trellis-coded modulation in spread spectrum communications

This dissertation presents a novel trellis-coded modulation scheme named Circular Trellis-Coded Modulation (CTCM). This system is constructed by using permuted states which can be derived by using the permutation concept and Zech's logarithm. Instead of starting from the all-zero state, the trellis transmits fixed length blocks with a particular initial state which corresponds to its corresponding input sequence. CTCM transmits information more efficiently and the problem of trellis termination is solved. The butterfly structure is also investigated and the parallel transition property is exploited. The transmission symbol design is combined with the butterfly structure to achieve optimal distance.;In order to increase the Euclidean distance and avoid symbol reuse, high dimensional bi-orthogonal signal sets are employed. A new signal set called bi-pulse or 2-out-of-n is also introduced. This signal set achieves good distance distribution with moderate bandwidth expansion. The high dimensional signal set is useful in spread-spectrum applications.;With an unknown starting state, conventional Viterbi is not suitable for CTCM. The anchor symbol decoding algorithm measures the reliability of received symbols in order to speed up the search. By using highly reliable anchor symbols, tentative decoding paths formed and the most reliable path can be identified quickly. The anchor symbol decoder functions like an iterative decoder. Its low computational complexity in a high signal-to-noise ratio environment depends only on the length of the transmission block, without considering the sorting overhead. Therefore, it can be implemented in real-time.