Performance of SIMO System under Time Varying Wireless Channel using Partial CSI

Abstract

Coherent detection schemes require full Channel State Information (CSI) at the receiver for Single Input Single Output (SIMO) system. It is difficult to have full CSI at the receiver end in time varying channel due to large transmit overheads and the need for continuous channel estimation at the receiver for each symbol and channel. In this paper, receiver assumes the perfect channel knowledge of only a preable of two symbols is available. The subsequent received symbols of a frame of size $N$ are detected using the known preamble. The available CSI for two symbols is called as Partial CSI. A simple channel prediction technique to detect data in a time varying channel given partial CSI is proposed for 1xL SIMO system. Use of partial CSI will reduce the complexity at receiver end. A flat fading channel is modelled by a second order autoregressive (AR2) process which has higher correlation to Jakes model. Exact closed form generalized expression of probability of error for M-PSK modulation under partial CSI for 1 × $L$ SIMO system using maximum ratio combining (MRC) scheme is derived. Generalized expression of lower bound of probability of error for $M$ -PSK modulation under partial CSI for 1 × $L$ SIMO system using selection combining (SC) scheme is also derived. Further, these expressions are reduced for some special cases and compared them with prevailing results in the literature. Simulation results are presented for different modulation schemes and time-varying channel conditions for MRC and SC using proposed scheme which are closely matching with derived analytical expressions. Simulation results shows negligible degradation in performance under medium scale fast fading channel and approx. 2 dB degradation at 10–3 order BER under large scale fast fading channel using partial CSI.