Forward Error Correction is an efficient technique to correct, preferably burst errors, caused over several blocks of  transmitted data. Besides this, narrowband interference (NBI) is an unavoidable major cause for transmission errors in wireless communication, which is much severe in unlicensed band like ISM band. It is needed to spread the encoded data before being modulated to overcome both burst errors and interference. Direct Sequence Spread Spectrum (DSSS) is a good support for wireless networks with nodes preferred to consume less power due to its less implementation complexity. This paper is the simulated comparative analysis of BER performance of FEC coded coherent and non-coherent M-ary FSK under the impact of both Rayleigh and Rician fading channels. BCH, RS, Cyclic and Linear Block codes are used in this simulation. Simulation results show that, RS Encoder – Decoder pair gives good BER performance over Rayleigh fading channel,  especially with integer inputs and its performance should be enhanced for Rician fading channel.