The performance of fast frequency-hopping M-ary frequency shift keying modulation ( FFH/MFSK) system with equal gain combing frequency diversity and coded slow frequency-hopping Af-ary frequency shift keying modulation (SFH/MFSK ) system in underwater multipath fading channel is investigated, the bit error rate performance curve of dual, triple frequency diversity FFH/MFSK system and coded SFH/MFSK system using bit interleaved code modulation ( BICM) combined with(2, 1 , 3) , (3 , 1 , 3 ) convolution code respectively is presented, also the comparison the two system is given. Simulation results show that; both of the frequency diversity gain provided by FFH and the time-frequency diversity gain provided by channel coding can combat the underwater acoustic channel's time-frequency double fading effectively, but the BICM combined with soft decision decoding method can provide higher diversity order than FFH under the same coding rate, so have stronger anti-fading capacity.%研究了等增益合并频率分集M进制频移键控快跳频(FFH/MFSK)系统和编码M进制频移键控慢跳频(SFH/MFSK)系统在水声多途衰落信道中的性能,给出了频率2重和3重分集FFH/MFSK系统,以及采用(2,1,3)卷积码与(3,1,3)卷积码联合比特交织编码调制( BICM)的SFH/MFSK系统误比特率性能曲线,并进行了比较分析.仿真结果表明,FFH/MFSK提供的频率分集以及信道编码FH/MFSK所提供的时频隐分集都可以有效抵抗水声信道的时频双选择性衰落.但在相同编码效率下,基于BICM与软判决译码的信道编解码方式比快跳频显分集方式能提供更大的分集阶数,从而具有更优的抗衰落性能.
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