In wireless communication system, the multipath fading affects the performance of the system. Diversity-combining scheme is one of the powerful tools to mitigate the effect of fading. The multiple antennas provide an improvement in the capacity and reliability of the system. The performance of four combining schemes - Selection Combining (SC), Maximum Ratio Combining (MRC), Equal Gain Combining (EGC), and Generalised Selection combining (GSC)- in the presence of both the perfect and an imperfect channel state information (CSI) at the receiver is studied in this contribution by Monte Carlo simulations in the MATLAB environment, when communicating over Rayleigh fading channels. Our results show that the presence of the complex noise in the channel degrades the performance of the system in all four combining schemes, but the degradation in performance is found to be maximum in MRC and minimum in SC. Performance of EGC lies in between the performance of MRC and SC, whereas the performance of GSC depends upon the number of antennas being selected and it is upper bounded by the MRC and lower bounded by the SC. Also, the results show that as the value of SNR is increased the average received SNR increases in both the channels.