Permutation coding and MFSK modulation for frequency selective channel

In frequency selective channels, some frequencies may be in deep fade. Inherent frequency diversity in multilevel frequency shift keying is exploited by a coding technique called permutation code, which ensures that the frequencies occur equally often. Information bits are uniformly spread over the frequency band. The performance of permutation codes and 4FSK in terms of bit error rate is compared with convolutional codes over 50 ns and 100 ns delay spread channel.