Chapter 10
Iterative Detection of Three-Stage Concatenated Ir VLC FFH-MFSK1
11.1 Introduction
Fast Frequency Hopping (FFH) M-ary Frequency Shift Keying (MFSK) has been shown to efficiently combat Partial Band Noise Jamming (PBNJ) [338]. The source of PBNJ may be intentional, as in the case of military communication systems [339] where enemy jammers try to disrupt the friendly communication. But it may be caused by microwave sources and lighting devices operating adjacent to a Frequency Hopping (FH) network. The military communication systems usually operate using a wide frequency band. Similarly, a number of commercial FH networks utilize the Industrial Scientific Medical band. Thus both types of communication systems are susceptible to partial-band or full-band noise interference imposed by intentional or unintentional jammers. By transmitting every symbol using multiple hops, FFH systems benefit from both time and frequency diversity, which assists in mitigating the detrimental effects of PBNJ. Furthermore, in the FFH-MFSK receiver, a suitable diversity combining method may be invoked to further suppress the effects of PBNJ. We employ clipped combining [338] for this purpose. This is an effective, low-complexity combining scheme dispensing with estimation of channel gains, which would be required in order to invoke maximal ratio combining [340]. Furthermore, ...
