The downlink call admission control (CAC) scheme we call the combined CAC scheme is proposed to improve the call blocking for the 3rd (3G) generation W-CDMA system. The blocking probability of attempted calls would increase if a large number of users tries to place calls in a hot spot area. In this situation, the proposed scheme can mitigate the degradation of the GoS (grade of service) of multiple services by using the available radio channels of the neighboring cells and enhance the channel capacity by about 20% for the blocking probability of 1% under the given example condition of voice service.

In this letter, we propose an Adaptive Modulation and Coding (AMC) scheme with relay protocols, such as Amplify-and-Forward (AF), Decode-and-Forward (DF) and De-Modulate-and-Forward (DMF). We perform simulations based on 3GPP Long Term Evolution-Advanced (LTE-A) parameters to compare the performance of an adaptive Modulation and Coding Scheme (MCS) using relay protocols of AF, DF, and DMF with non-adaptive MCS, with the same relay protocols. We analyze the performance of the proposed scheme and observe how the proposed AMC scheme with DMF performs at various Signal to Noise Ratio (SNR) regions. The simulation results have shown that the performance of the proposed AMC scheme with relay protocols of DMF is much better at lower and a higher SNR regions and also provides higher average throughput.