Design and implementation of scalable space-time trellis codes

Abstract

This thesis introduces a new approach to design space time trellis codes (STTCs) with large constellation size in wireless communication systems with any number of transmit antennas. Our design procedure is based on utilizing QPSK STTCs as component codes and consequently, unlike existing techniques, the search space does not grow exponentially with the constellation size. Our approach is further based on the fact that an n × m multiple-input multiple-output (MIMO) system is equivalent to n distinct 1 × m systems. By employing a common design for each individual 1 × m system, we arrive at an approach whose complexity does not grow with the number of transmit antennas. To describe our approach, we first demonstrate that a system employing a STTC can be implemented with only a single transmit antenna when there are multiple receive antennas. The idea is to transmit more than one symbol from a single transmit antenna during a symbol period by superimposing the encoded symbols on top of each other. This objective is achieved by inducing randomness into the system, that creates additional channel paths, called virtual paths. The design of the distributions of the induced random variables is studied for slow Rayleigh and Rician fading channels by utilizing an upper bound on the pairwise block error probability. Furthermore, we propose practical approaches to reduce the computational complexity of our proposed scheme. we introduce two techniques, namely, a new flexible mapping that can reduce the complexity and a new soft decoding Viterbi algorithm based interference suppression concept. Simulation results demonstrate the frame error rate (FER) performance improvement of our approach compared to space-time block code (STBC) combined with trellis code modulation (TCM) for the case of two transmit antennas and several different number of receive antennas, a spectral efficiency of 4 bits/s/Hz, and in slow Rayleigh fading channels. Our proposed scheme requires similar o...