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 (SINRth). If a high value of SINRth is chosen, the signal quality will improve but this will increase the blocking probability (pb), and as a result, will decrease the network utilization. On the other hand, a low value of SINRth will reduce pb, however degrades the signal quality and increases outage probability (pout). Hence, how to choose appropriate SINRth is very important. In this paper, we focus on the following aspects. Firstly, an accurate upper bound of SINRth is derived. Secondly, based on the upper bound of SINRth and a lower bound from other literature, we design a fuzzy logic controller (FLC), which can adaptively adjust SINRth 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 SINRth. Numerical results show that the proposed scheme based on FLC has better performance than the optimal fixed threshold CAC scheme.