Radio resource management in multiple-chip-rate DS/CDMA systems supporting multimedia services

Abstract

Third-generation wireless systems, such as the IMT-2000 and the UMTS, are required to accommodate a wide variety of services, including high quality voice, data, facsimile, video, and interactive applications, with information bit rates ranging from a few kbps to 2 Mbps. Code division multiple access (CDMA) is a promising technique that complies with the above requirements. Especially, direct sequence (DS)-CDMA is attractive because of its flexibility in supporting multimedia traffic, as well as its low interference coexistence with other CDMA or narrow-band systems operating in the same frequency band. Two approaches for accommodating multi-rate services generated from multimedia traffic in DS-CDMA systems have been proposed. One is to use either a single-code (SC) or a multi-code (MC) DS-CDMA system in a single RF channel bandwidth. The other is to use a multiple-chip-rate (MCR) DS/CDMA system in multiple RF channel bandwidths. This dissertation is concerned with radio resource management in MCR-DS/CDMA systems accommodating multimedia services with different information rates and quality requirements. First, capacity estimation in MCR-DS/CDMA systems is concerned. Considering both power spectral density (PSD) over a radio frequency (RF) band and the effect of RF input filtering on a receiver, interference factor is introduced in order to account for other user interference in the same frequency band. Criteria for capacity estimation are presented and the minimum value of the received power which causes the least interference for other users while maintaining an acceptable quality-of-service (QoS) requirement is also derived. In addition, given a state of a system, admissible capacity is estimated. Second, characteristics of co-channel interference between subsystems in MCR-DS/CDMA systems are investigated. The results show that system performance is strongly affected by a selected channel assignment strategy. Therefore, it is important to efficiently ass...