EM algorithm estimation of TCM scheme over multipath fading

Abstract

The performance of Trellis Coded Modulation scheme via Expectation-Maximization algorithm utilizing a Kalman filter over multipath fading is presented. EM algorithm offers an easier computation than the classical ML estimation does. To get a better prediction of the communication performance, a fading channel model whose characteristics match with the real fading is implemented in the simulation. In the study a multipath fading channel model is considered. Multipath fading channel is applied to a communication system where the direct line-of-sight signal is blocked. A Trellis coding scheme is used to increase the system performance in this type of fading channel which is found to be a burst error channel and/or a random error channel. To further combat the burst error a block interleaver is incorporated in the system. Simulation results are presented for various normalized fading bandwidth which correspond normal vehicle speed at 2400 baud rate for an L-band carrier frequency. The gain between a receiver with perfect channel information and a receiver employing EM algorithm is 3-4 db for heavy and light fading over a range BTs of 0.01-0.1.