Mlse Based Equalization and Fading Channel Modeling for Gsm

This paper presents an outline on the need of equalization in case of GSM systems. The modulation scheme employed in GSM systems is GMSK, which is both power and spectrum efficient, but at the cost of increased intersymbol interference. The effect of inter-symbol interference is more severe in case of multipath fading channel. This obviates the need of near optimum equalization. In this paper fading channel modeling and trained equalization technique has been discussed, which includes the channel estimation and timing synchronization, followed by a trellis based equalizer (Maximum likelihood sequence estimation) using Viterbi Algorithm for estimating the transmitted bits from the received signal and estimated channel response. The paper concludes with some of the BER results in different channel conditions as per the GSM recommendations. Index Terms – GSM, GMSK, Equalization, MLSE, trained equalizer, demodulation, Viterbi Equalization, channel estimation.