Coordinated Radio Resource Management for the LTE Downlink: The Two-Sector Case

We consider the downlink of an Orthogonal Frequency Division Multiple Access (OFDMA) network. OFDMA transmission technology will be used in the next generation of wireless networks such as the LTE (Long Term Evolution) and WiMAX wireless standards. In such a channel, multiple User Equipments (UE) may each be allocated multiple Resource Blocks (RBs) in each frame. A RB is a collection of subcarriers spanned over all symbols that are available for data transmission. We are concerned with the optimal allocation of power and bandwidth (number of subcarriers) with the objective of maximizing the sector-wide throughput. Note that since we are considering multi-sector performance then the influence of intersector interference is also taken into account. In general, this problem is intractable and so we focus on the two sector case to gain intuition that can then be applied to more general algorithms. We determine the regions within which (a) a frequency reuse factor of unity is optimal, (b) orthogonal frequency allocations is optimal and (c) joint processing of signals from both sectors is optimal. We also show that it is never optimal to combine two or more of these solutions for a given scenario.