SCTAC: A novel MAC protocol for a multiCode-CDMA network

Abstract

Existing MultiCode-CDMA MAC protocols perform only single dimensional access control either in the code or time domain. In this paper, we propose a MAC protocol, called SCTAC which can perform simultaneous code-time access control to achieve better system utilization. Also, SCTAC intends to provide service differentiation among different traffic classes. In order to simultaneously control access in both the code and time domain, SCTAC decouples the function of transmission ordering from the function of packing the scheduled transmissions in the resource space. As such, different transmission scheduling algorithms can be adopted without altering the MAC protocol. A water filling approach is used for efficient transmission packing where each of the scheduled transmissions is treated as a rectangular capsule with an arbitrary size and the resource space is viewed as a water container. In addition, SCTAC uses different request sending probabilities with an improved probability update algorithm to achieve service differentiation. Simulation results indicate that SCTAC is capable of providing different performances to different traffic classes. The results also confirm that SCTAC can achieve higher throughput compared to single dimensional access control protocols.Therefore, SCTAC is a better MAC protocol.