Performance study of differential frequency hopping systems over a Rayleigh-faded channel in the presence of jamming

Abstract

Differential frequency hopping (DFH) is a novel technique employed by the

correlated hopping enhanced spread spectrum (CHESS) radio, developed by the

Sanders Company. The core of the DFH technique is in its frequency transition

function (FTF), which generates a sequence of correlated frequency hops

corresponding to the input information sequence. As a result, DFH systems are able

to reconstruct missed hops in the detection process.

This Final Year Project (FYP) report documents the investigations of the bit-error

performance of DFH systems in Rayleigh-fading channels in the presence of partialband

noise jamming (PBNJ). The bit-error performance of fast frequency-hopped

(FFH) systems employing binary frequency-shift keying (BFSK) corrupted by the

worst-case PBNJ, additive white Gaussian noise (AWGN) and Rayleigh-fading

channels is also investigated and acts as supplementary materials for the

investigation of DFH systems. Four different designs of FTF encoders for DFH

systems are investigated in this FYP.

Simulation results obtained show that DFH systems outperform conventional

FFH/BFSK systems when corrupted by the worst-case PBNJ and AWGN. The

improved performance is due to the error correcting characteristic of DFH systems.

When operating in Rayleigh-fading channels corrupted with the worst-case PBNJ,

DFH systems, depending on the type of FTF encoder employed, exhibits better

performance as compared to FFH/BFSK systems with a diversity level of one.

However, it is observed that the performance of DFH systems vary with the four

different encoder types. Therefore, it can be concluded that the design of the FTF

plays a key role in dictating the performance for DFH systems.