Channel allocation algorithms for multi-carrier multiple-antenna systems

Abstract

Dynamic channel resource allocation (DCA) exploiting wideband multiuser diversity can provide data transmission with very high spectral efficiency by scheduling at each dimension (time, frequency, space) the user with the best channel conditions. The main issue arising from this allocation is fairness. Base station or users have to wait until their channel is most favorable to transmit. It is commonly considered that fairness comes at the cost of a significant system capacity penalty. In this paper we show that multiuser diversity, and thus an increase of aggregate data rates with the size of the user population, can still be successfully achieved even with deterministic channel use and that even under a hard fairness constraint we can achieve performance which comes close to those of the optimal unfair policy for K-user systems with K parallel sub-channels. We propose and compare different algorithms which perform channel allocation yielding variable-rate/constant-power (Max–Min allocation and maximum total rate allocation) and fixed-rate/variable-power (fixed rate allocation). We show the effect of system bandwidth (and thus sub-channel correlation) on wideband multiuser diversity. This paper also investigates the performance of combined orthogonal channel and antenna allocation algorithms in multiple-antenna multi-channel systems. We extend the proposed Max-Min allocation algorithm to the multiple-antenna systems and compare its performance in two different transmission scenarios (spatial multiplexing and space time coding). An extension of the Max–Min allocation algorithm to the general case of an arbitrary number of users is also given. The proposed techniques are applicable, for instance, in orthogonal frequency division multiple-access (OFDMA) systems with dynamic sub-carrier allocation.