Contention-TDMA protocol: performance evaluation

A hybrid access protocol known, as contention time-division multiple access (C-TDMA), is presented and analyzed in a radio cellular multiuser system scenario. C-TDMA shows some features of contention-based (slotted-ALOHA) and reservation-based (packet reservation multiple access, PRMA) protocols. It has been recommended for use in the uplink of future European multimedia distribution systems. A simple Markov model is proposed to describe C-TDMA behavior. A complete statistical analysis of the model has been made in order to evaluate the performance of the protocol. However, due to the long computation time required in the presence of a large number of users, a simpler approach known as equilibrium point analysis (EPA) is used. Moreover, on the basis of the EPA analysis and the C-TDMA design parameters, a fast algorithm has been developed to improve the achievable throughput of C-TDMA. Results in terms of throughput and delay under variable traffic conditions indicate that C-TDMA is able to grant optimum throughput/delay figures for typical multiuser systems. Moreover, for a digital speech scenario, a performance comparison with PRMA demonstrates that C-TDMA yields equivalent performance to PRMA in terms of number of users supported by the system with a limited packet dropping rate.