Resource allocation algorithms for OFDM based wireless systems

Carrier Aggregation (CA) is a key functionality for next generation wireless communication systems that enables operators to create larger virtual carrier bandwidths for data hungry applications by aggregating available Component Carriers (CCs). In this paper, the Resource Allocation (RA) optimisation problem in Orthogonal Frequency Division Multiplexing (OFDM) based wireless systems is studied with CA. We show that RA with CA can be formulated as a complex mixed integer programming optimisation problem under the practical constraints of transmit power and limited number of CCs available for each user. A two-step solution is proposed, Step 1: CC allocation is performed to satisfy users CA constraints and remove the intractable integer constraints of the optimisation problem, Step 2: power and SubCarrier (SC) allocation algorithm assigns resources among users sub-optimally. We propose two efficient methods based on our two-step solution with reasonably low complexity refer as Two-Step RA Algorithm (TSRAA) and Efficient RA Algorithm (ERAA). The performance of TSRAA and ERAA are compared with the highly complex Combinatorial Algorithm (COA) introduced as an optimal solution. Simulation results verify that TSRAA reaches to optimum solution and exploits the multi-CC diversity of wireless systems. Furthermore, numerical results show that ERAA achieves satisfying performance with very low complexity.