Evaluation of the Effects of Co-Channel Interference on the Bit Error Rate for QPSK and M-QAM Modulations

In this paper, a performance analysis for QPSK, 16- QAM and 64-QAM, modulations in the presence of co-channel interference is made. At first, an expression of the bit error rate (BER) for M-PAM as a function of the Eb=N0 ratio in the presence of K interferers is obtained. The formula from the BER gotten earlier is used to derive a simplified expression for the BER of M-QAM modulations. For each modulation scheme, it is shown that there is a minimum signal to interference ratio (SIR) for the system does not present a BER floor. The results obtained show that modulations with higher order alphabets need high SIR in order to maintain the BER at satisfactory levels. This analysis can be applied in the performance evaluation of cellular radio networks, as WiMAX and LTE.