Downlink call admission control in mixed service CDMA cellular networks.
Since the ascendance of CDMA (Code Division Multiple Access) as the generally accepted multiple access technology of choice for next generation networks, the rate of development of the wireless cellular communication industry has been phenomenal. Next generation wireless cellular networks offer a myriad of voice, video, data and text based information services for the future multimedia and information society. This mixed service scenario implies that the same [mite resource i.e. the air interface must be shared amongst different classes of user, each with a specific quality of service. With multiple services competing for the same resource and with the inherent soft capacity nature of CDMA, call admission control becomes a formidable task. The problem is further compounded by the introduction of priorities between classes. Call admission control is an essential component of these next generation networks and the open nature of the current standards, such as UMTS (Universal Mobile Telecommunication System) allow for vendor implementation of different call admission control policies. The main area of focus in this dissertation is on a proposed downlink, load-based, mixed service call admission policy. In a CDMA environment with symmetrical service and equal bandwidths in each direction, the uplink is commonly considered to be the bottleneck. Based on the asymmetric nature of the expected traffic in next generation networks the downlink is envisaged as the future bottleneck. Some of the more common choices for downlink call admission control include number based as well as power based call admission policies. A load-based call admission policy has been chosen as the maximum load threshold that can be supported varies with the state of the system and thus effectively models the behaviour of a soft capacity CDMA network. This dissertation presents a teletraffic performance analysis model of a load-based call admission control policy for downlink mixed service CDMA cellular networks. The performance analysis yields customer oriented grade-of-service parameters such as call blocking probability which is essential for network planning. In our analysis we incorporate a Birth-Death Markov queuing model. This mathematical model is verified though computer simulation.