Architecture designs for improving performance in fading channel communications

This work is to investigate several important design issues for mobile digital communications. First, the burst design problem associated with pilot symbol allocation in a frequency flat fading environment is examined. The capability to combat channel fading and simple implementation have made the pilot symbol assisted modulation (PSAM) of practical interest but the operation in burst mode for multiple access purpose is still absent. A new unequal spacing pilot insertion burst architecture is proposed to achieve better error performance. Frequency offset compensation in PSAM is another major focus in this work. This work investigates the optimal frequency offset estimation in mobile fading channels and sub-optimal frequency offset estimators with high performance and reduced complexity. Implementing a high performance frequency offset estimator can significantly relieve the accuracy specification of the local oscillator and improve the error performance and throughput rate. Using intentional frequency offset in transmitter diversity to improve performance in fading channel communications is another major investigation of this work. Coded modulation can provide different fading on different code symbols to achieve high performance when combined with proper interleaving. However, in many practical applications, low mobility is a typical feature and hence close-to-ideal interleaving is not feasible. This work shows that proper selection of the intentional frequency offset and interleaving depth can achieve ideal interleaving and significantly improve the performance. The prevalent union bound of bit error probability is found to produce large bounding errors in slow fading cases and an improved union bound is presented to assess the close-to-actual error performance