Call admission control in mobile cellular CDMA systems using fuzzy associative memory

In a mobile cellular system quality of service (QoS) to mobile terminals (MTs) is measured by the probability of forced termination P_ft and/or probability of new call blocking (P_b). Since, both cannot be reduced simultaneously, usually keeping the P_ft below a designated level DP_ft is considered as QoS guarantee to the users of the system. However, P_ft is related to system parameters namely, maximum capacity of the cell C, the average new call arrival rate λ, the average call holding time 1/μ, and the average cell dwell time 1/η by complex nonlinear equations. Therefore, call admission control (CAC) for maintaining P_ft at DP_ft is a very challenging task. A fuzzy controller is proposed to dynamically maintain P_ft at DP_ft with changes in system parameters. Also, current cellular networks are employing CDMA as the multiple access technique since it provides much more capacity than other techniques. Interference received at the base station (BS) of a cell is considered in the decision making process of whether to admit a call or not. We describe the CAC criteria used in CDMA cellular networks in this paper. Also, through simulation we show that fuzzy controller can be integrated with other CAC schemes to guarantee QoS to the users.