Improving the accuracy of SINR threshold lower bound for SINR-based call admission control in CDMA networks

Call admission control (CAC) is used in CDMA networks to guarantee the signal quality in terms of the signal-to-interference-and-noise ratio (SINR). SINR is employed as the criterion for user admission by comparing the SINR with a threshold value (SINR_th). A small threshold level is desirable to reduce the blocking rate. However, a lower bound of SINR_th is essential to keep the outage probability (P_out) below a maximum value. A lower bound of SINR_th (SINR_th-lb) has been derived in M.H. Ahmed and H. Yanikomeroglu, (2005) by finding the relationship between P_out and SINR_th. Then, SINR_th-lb is determined as the lowest SINR_th that keeps P_out below a certain P_{out_max}. In this paper, we improve the accuracy of SINR_th-lb by modeling the admitted traffic using a Markov model (instead of the inaccurate Poisson model used in M.H. Ahmed and H. Yanikomeroglu, (2005)). In addition, we improve the accuracy by choosing the transition value of the step function that approximates the conditional outage probability distribution using the minimum mean square error criterion