A new CAC scheme based on adaptive SINR threshold using fuzzy logic for CDMA system

Signal to interference plus noise ratio (SINR) based call admission control (CAC) scheme admits incoming calls as long as the measured SINR is higher than threshold value (SINR_th). If a high value of SINR_th is chosen, the signal quality will improve but this will increase the blocking probability (p_b), and as a result, will decrease the network utilization. On the other hand, a low value of SINR_th will reduce p_b, however degrades the signal quality and increases outage probability (p_out). Hence, how to choose appropriate SINR_th is very important. In this paper, we focus on the following aspects. Firstly, an accurate upper bound of SINR_th is derived. Secondly, based on the upper bound of SINR_th and a lower bound from other literature, we design a fuzzy logic controller (FLC), which can adaptively adjust SINR_th according to the number of active users (AUs) in a cell and average arriving traffic intensity (AATI) in Erlang per cell. Finally, network performance based on FLC is compared with that based on optimal fixed SINR_th. Numerical results show that the proposed scheme based on FLC has better performance than the optimal fixed threshold CAC scheme.