LIKELIHOOD RECEIVER FOR FH-MFSK MOBILE RADIO*

Abstract

We investigate the performance of a likelihood receiver for the detection of frequency hopped multilevel frequency shift keyed signals (FH-MFSK) to a mobile user operating in a multi user environment. The analysis assumes synchronous transmission from base to mobiles operating in an isolated cell-cellular system and a simplified mobile radio channel. The likelihood receiver attempts to discriminate spurious rows of the decoded matrix of a user, which consists of samples from an exponential-mixture, from the correct row, which consists of samples from a simple exponential density, by computing the log-likelihood statistic for each row. It declares the row possessing the minimum value as the correct row, corresponding to the word transmitted to the user. An approximate analysis of the probability of bit error of this receiver by three means, viz. (i) large sample approximation (ii) simple Chernoff bound and (iii) Chernoff bound with central limit theorem, reveals that the likelihood receiver is only marginally superior to a hard limited combining receiver.