Optimal Policies for Multi-Media Integration in CDMA Networks

Abstract

In this paper we describe two policies for efficient use of the spectrum by multi-media users in direct-sequence code-division multiple-access (DS/CDMA) networks. The first policy pertains to CDMA networks with voice traffic and lower priority data traffic; voice and data have different bit error rate (BER) requirements. In this scheme, data traffic can only use the capacity of the CDMA system that is left unused by voice users and gets buffered whenever there are insufficient resources (CDMA codes). The second policy pertains to CDMA networks with voice traffic and two types of data traffic: high priority data traffic with the same priority as voice traffic that requires real-time delivery and lower priority data traffic that can tolerate delay and thus can be queued. In this scheme a movable boundary policy in the CDMA code domain is used for the voice and high priority data, whereas a small number of CDMA codes are reserved for the lower priority data which also utilizes any CDMA codes left unused by the other two traffic types.

Optimal policies for the two above formulations are obtained by minimizing cost functions consisting of the rejection rate of voice traffic for the former case and of the weighted sum of the rejection rates of voice and high priority data traffic for the latter case, subject to performance requirements on the BERs of all traffic types. The queueing delay of the lower priority data traffic is also evaluated. A semi-Markov decision process (SMDP) with guaranteed BERs for voice and data traffic is used for formulating the dynamic code assignment problem. Value-iteration algorithms are applied to this SMDP to derive the optimal policies.