An Upper Bound on SINR Threshold for Call Admission Control in Multiple-Class CDMA Systems with Imperfect Power-Control

Call admission control (CAC) is essential to guarantee the signal quality in CDMA systems. Signal-to-interference-and-noise ratio (SINR) is used as a criterion for user admission by comparing the SINR with a predefined threshold value (SINR_th). The choice of the SINR_th value is restricted by two opposing factors: the signal quality and the network utilization. Setting SINR_th at high value is desirable to increase the signal quality. However, SINR_th shouldn´t exceed a certain limit to keep the blocking probability (Pb) below a maximum value. In this paper, we derive an upper bound of SINR_th (SINR_th-ub) for multi-class CDMA systems with imperfect power control. SINR_th-ub of class i (SINR_th-ub(i), i=1, 2,...., L) is determined by finding the relationship between the blocking probability of all classes and SINR_th(i). Then, SINR_th-ub(i) is determined as the highest value of SINR_th(i) that keeps the blocking probability of all classes below the corresponding maximum values.