Scheduling in Cellular CDMA-TDD Networks

In this paper different scheduling algorithms applied to cellular CDMA (code division multiple access) systems with different duplexing modes are studied. In particular, the performance of cellular CDMA-TDD (time division duplex) with random uplink (UL)/downlink (DL) assignment is compared to cellular CDMA-FDD (frequency division duplex) systems. The random UL/DL assignment in TDD is previously reported as random time slot opposing (RTSO), and it was shown that this technique results in interference diversity when used in a cellular system. It is demonstrated in this paper that scheduling algorithms can effectively exploit this interference diversity to enhance the total spectral efficiency. Throughput, outage and average transmit power are used to compare the performance. First, it can be observed that, despite additional interference sources in TDD, TDD and FDD result in about the same throughput and outage performance for a cellular deployment. However, the stepwise rate removal (SRR) algorithm results in significantly improved outage in TDD. Second, regardless of the duplexing technique the results show that a general improvement in throughput is always at the cost of the number of users served.