Improving fairness by carrier load balancing in relay enhanced systems

In this paper we consider joint utilization of two techniques proposed for the next generation of wireless communication systems, i.e. relaying and multi-carrier operation. Resource partitioning between user and relay links, as well as configuration of relay cells is discussed. The problem of optimum allocation of resources from the available component carriers is analyzed from the end user performance point of view. In this paper the centralized network configuration scheme is utilized, i.e. the macro station controls resource assignment for all types of stations and links within its coverage area. For this scheme several carrier load balancing methods are investigated. The methods differ in criteria included in the decision process, starting from a purely random allocation and extending to a joint signal quality and load oriented approach. The methods are evaluated first by means of theoretical estimations, and later by system level simulations. The evaluations are done in the direction of two performance metrics, namely mean user throughput and uniformity of user throughputs across network. The conclusion from the conducted analysis is that most of the advanced balancing methods (i.e. not blind random) can provided significant performance uniformity improvements in the order of 10%, as well as mean performance gains of 2%. We note that in practical implementation, the selection of a specific method should also be based on the availability of required measurements.