Abstract
Capability to combat channel fading and easy implementation have made the pilot symbol assisted modulation (PSAM) of practical interest in mobile communications. However, the operation in burst mode for multiple access purpose has still been a missing part from previous research. This work first examines the burst design problem associated with pilot symbol allocation in a frequency flat fading environment. Explicit relationship between error performance and the design parameters including pilot distribution, frequency offset, Doppler spread, and modulation scheme is exploreti. A new unequal spacing pilot insertion burst architecture is proposed to achieve better error performance. Frequency offset compensation in PSAM is another major investigation in this work. In a mobile fading environment, conventional frequency tracking loops suffer lost track or false lock frequently. Recent research has tried on using the consistent phase error in the correlations of pilots to estimate the frequency offset. However, the optimal frequency offset estimation in mobile fading channels is still absent from previous reports and is a major focus of this work. Frequency offset estimators with high performance and reduced complexity are studied. This work also focuses on the performance improvement of a frequency offset estimator and a Doppler spread estimator. The performance degradation investigated can be used to determine the specification of the frequency offset estimator and Doppler spread estimator used in PSAM. Implementing a high performance frequency offset estimator in a fading-channel receiver can significantly relieve the specification of the local oscillator and significantly improve the error performance and throughput rate.
Date of this Version
May 1994