Adaptive Call Admission Control in Tdd-cdma Cellular Wireless Networks

The Code Division Multiple Access system with Time Division Duplex mode (TDD-CDMA), adopting unbalanced slot allocation between uplink and downlink, can meet the asymmetric traffic requirement of multimedia services. Here a call admission control policy is proposed to support different multimedia applications. The scheme operates at the connection-level where the CDMA code of ongoing call can be dynamically changed to provide an acceptable trade off level between connection blocking and dropping probabilities for different traffic class. Although Orthogonal Variable Spreading Factor (OVSF) code is used in simulation here, the paramount interest is on algorithm that allows optimum use of the TDD-CDMA resources i.e. code and time slots. Simulation results shows that on the expense of resource allocated to non real-time services, the call dropping and blocking rate for high priority (real-time) services can be minimized.