Interference suppression using diversity and equalization in digital cellular mobile radio communication.

摘要

In digital cellular mobile radio systems, transmission is subject to two major sources of propagation degradation, namely multipath fading and co-channel interference. Multipath fading may be frequency-selective leading to intersymbol interference for high-rate data transmission. Co-channel interference is the dominant interfering source, due to the reuse of the frequencies for increasing the spectrum efficiency and system capacity. This dissertation analyzes the performance of space diversity-combining and equalization in a mobile radio environment with QAM transmission, intersymbol interference, Gaussian noise and co-channel interference. Optimum diversity combining receivers using selection-diversity and combining-diversity structures, operating in the two-path channel with equal and unequal mean power received on each diversity branch, are investigated. Both linear and decision-feedback equalization techniques with infinite and finite taps are considered. The application of neural networks to channel equalization is also considered. Since interference undergoes similar multipath phenomenon as signal where thermal noise does not, the statistical properties of interference and additive noise can be quite different. The modeling of interference is crucial for evaluating the performance of digital radios. We derive a new wide-sense stationary co-channel interference model, and then develop an optimal diversity receiver filter when additive gaussian noise and co-channel interference are present. New mathematical methods and realistic interference models have been developed for the simulation and analysis of diversity combining and equalization techniques.