BER Performance Evaluation of GMSK for Fading Mobile Channels

Digital modulation plays a significant role in efficient wireless communication. It allows the transmission of digital data via air on high frequency carrier waves. The worst case communication channel is usually in the urban environment where there are many obstacles. Due to the obstacles and reflectors, the transmitted signal arrives at the receiver from various directions over a multiplicity of paths. Such a phenomenon is called multipath. Mobile radio propagation is characterized by three main aspects: fading, shadowing and path loss. A major concern in a cellular mobile radio system is the co-channel interference. Therefore, the reduction of co-channel interference becomes a main thrust for the system design engineers. GMSK is studied and identified as an effective digital modulation technique suitable for power and band-limited mobile radio. This paper evaluates the BER performance of GMSK system under different channel models i.e. AWGN, Rayleigh and Rician fading channels. Subsequently, a comparative study is carried out to obtain the BER performance for BPSK and QPSK under fading mobile channels. The comparative study showed that BER for BPSK and QPSK are similar and they give the lowest BER under multipath fading. Though BPSK and QPSK give slightly better BER performance than GMSK, the spectral efficiency and hence power efficiency advantages of GMSK make it the preferred choice of modulation in fading mobile channels. Keywords— Digital modulation, GMSK, Co-channel interference, Fading, Spectrum Manipulation, BER.