On the Complexity of Radio Resources Allocation in WCDMA Systems

Recent attention to resource allocation algorithms for multiservice CDMA networks has focused on algorithms optimizing the aggregate throughputs (sum of all individual throughputs) on the uplink and on the downlink. Unfortunately, for a given set of real time (RT) and non real-time (NRT) communications services, such optimal algorithms involve non-integer spreading factors that do not belong to a finite set of spreading length as used in 3G systems. In this paper, we propose four algorithms for power and spreading allocation to RT and NRT services implementable in a real CDMA network like UMTS in the Frequency Division Duplexing (FDD) mode. On the downlink, two algorithms are presented; the first one maximises the aggregate downlink NRT throughput whereas the second one maximises the number of simultaneously transmitted NRT services. On the uplink, an algorithm that maximises the aggregate uplink NRT throughput and a suboptimal one, more easy to implement, are presented. Thanks to power control, both algorithms allow more simultaneous transmitting terminals than the optimal one. In both directions, the resulting aggregate NRT throughputs are very close to the ones obtained by the optimal algorithms. The small difference is the price paid for obtaining truly assignable spreading factors.