Performance Analysis of EGC and MRC Receivers over Fading Channels with Phase Estimation Error and Co-channel Interference

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Signals transmitted through wireless medium undergo several distortion due to various atmospheric effects. As a result, received several copies of the original signal with random attenuation and phases causes the net received signal strength to fluctuate with time causing fading. Fading causes degradation in the performance of communication systems relative to the performance in additive white Gaussian (AWGN) channels. As the fading environment experienced by a mobile user keeps on changing, the channel experienced by the user can be characterized by multipath fading, shadow fading, or a mixture of the both. Some known fading models are Hoyt, Nakagami-m, Nakagami-q, Generalized Gamma (GG), Generalized-K (KG), and fading channels. Effect of fading can be reduced by implementing diversity combining techniques in receivers in which received copies of the original signal, are processed together to generate a resultant signal whose rate of fluctuation becomes less compared to that of individual signal copies. Known basic diversity combining techniques are selection combining (SC), maximal ratio combining (MRC) and equal gain combining (EGC). To obtain best performance from diversity combiners it is required to accurately estimate the instantaneous amplitude and phase of each signal copy. Under ideal conditions, the performance improvement obtained through MRC is better than that of EGC which is better than that of SC, compared to systems without diversity combining. In practice, the received carrier phase is estimated using a first order phase locked loop (PLL). Due to the presence of thermal noise in the phase estimation circuit the estimated parameters may not be accurate and hence degradation in the receiver performance is obvious. To maximize system capacity, mobile communication systems reuse frequency in cell clusters which causes co-channel interference (CCI) resulting in further degradation in receiver performance. Thus, phase estimation error and CCI are two issues of practical importance in mobile communications. Hence, an investigation on the performance of mobile communication systems using diversity combining is necessary to know the amount of performance the practical systems can provide in the presence of both phase estimation error and CCI.
Supervisor: Pravas Ranjan Sahu