The University of British Columbia

Previous work on code division multiple access (CDMA) often considers the bit error ratio (BER) at the physical layer and the frame drop ratio (FDR) at the medium access control (MAC) layer separately. However, better system performance (e.g., lower overall packet loss ratio (PLR)) can be achieved if BER and FDR are jointly optimized. This paper, the authors first set up a Markov chain model to evaluate the performance of transporting multimedia traffic over a multi-code CDMA network. Then, the authors propose two novel cross-layer optimization methods that dynamically adjust the maximum number of simultaneous transmissions according to the traffic arrival rate and the queue status, respectively. Simulation and analytical results show that these two methods can significantly reduce PLR and increase the system throughput.