Performance analysis of time-multiplexed services for UMTS W-CDMA reverse link

Abstract

In UMTS W-CDMA systems, it is possible to offer multiplexed services such as voice, data, and video simultaneously on one physical connection. Several issues such as the QoS requirement for each service, algorithmic complexity, hardware limitations, and performance of the overall system must be considered. In this paper, we investigate some of these issues and present link-level performance for multiplexed services on the reverse-link of an UMTS W-CDMA system. We show that because of an increase in the peak-to-average power ratio when different services are code-multiplexed onto the same physical channel, multiplexed services for UMTS may have to be offered via the time-multiplexing approach. Next, we illustrate how rate matching can be used to satisfy the quality of service requirements for all services. In our results, we illustrate how the rate matching attributes can be selected to satisfy the QoS requirements of 1% speech frame error rate, 10% data frame error rate, and 0.1% video frame error rate. The selection of good rate matching attributes, however, is dependent on many factors such as service rates, channel conditions, and desired error rates. As a result, under some circumstances, excessive transmission power may be required in order to meet the minimum QoS requirements. Next, the performance of the system under compressed mode, where certain frames are compressed in time to allow inter-frequency measurements or handover to other systems, is considered. It is shown that the degradation due to compressed mode is minimal (less than 0.5 dB), and hence compressed mode can safely be used in conjunction with multiplexed services.