Survey on diversity‐combining techniques for interference suppression in fast frequency hopping systems

Abstract

Over the past few decades, frequency hopping (FH) techniques have attracted considerable interest in both military and commercial communications. However, fading and interference can significantly degrade the performance of an FH system. One method commonly employed to overcome the degradation in performance because of the fading is the use of diversity. Furthermore, fast FH (FFH) systems can enjoy both time and frequency diversity and hence FFH systems employed in conjunction with diversity-combining techniques are effective for combating fading and interference effects. In this study, the authors provide a comprehensive survey on the past and current research work on diversity-combining techniques for suppressing different types of interference in FFH M-ary frequency-shiftkeying systems over various fading channels. Some commonly used theoretical approaches for analysing performance of FFH systems are also presented. In addition to the survey, they will also discuss some interesting areas of future work in this research topic.

Keystone Transform-Based Parameter Search for Wide-Band Hybrid DS/FH Systems

“…The 2-D grid search scheme performs a joint search in the velocity and delay space [7]- [9]. Under each velocity search cell, the received signal needs to be mixed with a local regenerated carrier, and then, the cross-correlation value between the mixed signal and local PN code in all delay cells are computed as the detection variable.…”

“…Then, the velocity can be searched without considering the PN code modulation. To improve the detection performance in low SNR scenarios, [7]- [9] use the serial Doppler frequency compensation method for signal energy accumulation in velocity cell. Although the DFD can be eliminated, this method requires considerable calculations.…”

Low‐cost message‐driven frequency‐hopping scheme based on slow frequency‐hopping

“…As a well‐known spread‐spectrum technique, frequency‐hopping (FH) is widely used in a variety of military and civilian applications [1]. FH systems can provide secure communication links in the presence of jammings and eavesdroppers since they ramdomly switch their channels based on FH sequences (FHS) [2].…”

Research on Narrowband Interference Suppression and Diversity Characteristics in Fast Frequency-Hopping Communication Systems

“…Frequency-hopping (FH) communication can reach a fairly wide bandwidth and possess the performance of anti-interference, but when the intensity of interference signals far exceeds the anti-interference ability of FH communication system itself, the receiver will fail to receive data precisely, and decrease the anti-interference performance of frequency-hopping system. Therefore, scientists have proposed the interference suppression method to further enhance the anti-interference ability of frequency-hopping system [1][2][3][4].…”