Detection Schemes for Multi-Antenna FH/MFSK Systems in the Presence of Multiple Follower Jamming

Abstract

This dissertation focuses on the performance of the frequency hopping spread spectrum (FHSS) M-ary frequency shift keying (MFSK) systems in the presence of follower partial band jamming noise (PBJN) over flat fading channels. The thermal and other wideband Gaussian noises are modeled as additive white Gaussian noise (AWGN) at the receiver.

Follower partial band jamming is recognized as an efficient strategy to degrade the performance of FH/MFSK modulation. In this dissertation, three anti-jamming algorithms, based on maximum likelihood-based beamforming (MLBB), an area-based vector similarity metric (VSM), and a volumetric-based algorithm, are proposed to reject follower jamming and carry out symbol detection in slow FH/MFSK systems over quasi-static flat fading channels. In addition, theoretical analysis is derived under a jamming dominant scenario.

The MLBB algorithm which consists of a two-element array first uses an ML-based approach to obtain an ML estimate of the ratio of the jamming fading gains. Based on this ML estimate, a simple beamforming structure is employed to place a null toward the follower jamming source, and symbol detection is then performed by the ML technique. Theoretical and simulated results show the effectiveness of the proposed algorithm in combating follower jamming.

Using the principle of vector similarity, an area-based VSM algorithm is formulated to give an estimate of the unknown spatial correlation of the received jamming components at the two receiver antennas. The jamming signal can then be removed in the symbol detection process. The improved performance of the VSM algorithm is verified by analysis under a jamming dominant environment as well as using simulated bit error rate (BER) results.

The volumetric-based algorithm uses a multi-element array, and is proposed to reject multiple follower jamming signals and to carry out symbol detection in slow FH/MFSK systems over quasi-static flat fading channels. Specifically, with the use of the proposed algorithm, which can provide an estimate of the unknown spatial correlation of the received multiple jamming components at the receiver antennas, jamming can be removed in the symbol detection process. The jamming rejection capability of this algorithm is verified by analysis under a jamming dominant environment as well as by the much improved BER obtained in simulation studies.

In summary, the MLBB and VSM methods can reject a single jammer by using a two-element antenna. The volumetric algorithm can reject multiple jammers by using a multi-elements antenna. Finally, these three proposed algorithms can attain highly reliable bit detection with low BER values over a wide range of signal and jamming power ratios.