Subcarrier allocation and power control with LTE-A carrier aggregation

We consider the sum power minimization problem with user specific rate constraint in the context of uplink LTE-A type system with carrier aggregation (CA), more precisely, inter-band CA. The increased bandwidth in LTE-A system allows orthogonal allocation of subcarriers among users. If time sharing or non-linear receivers are assumed, the problem becomes convex and can be optimally solved by standard solvers. We adopt a Lagrangian dual decomposition method in the conventional single band LTE type system to solve the subcarrier allocation problem. We further propose a subcarrier allocation and power control algorithm for the wideband CA. Because of the non-convex nature of the orthogonal subcarrier allocation, the optimal solution is not guaranteed. However, it is shown in the simulation results, that when there are sufficient available bandwidth, the performance gap between the optimal solution is small. The simulation results show with the proposed fast algorithms, the CA performs better than the conventional single band system. The gains become larger as the frequency selectivity increases.