Cognitive Resource Allocation with Beamforming

Abstract

As we discussed in depth in the previous Chapters, the dense deployment of cells in HetNets means that the inter-layer interference in these networks must be handled appropriately to realize the actual benefits of HetNets. In particular, it becomes very challenging when there is zero or limited coordination among the cells, and cognitive capabilities and opportunistic use of the available resources are thus required. With that background, this Chapter describes potential cognitive approaches to both reduce the co-channel interference that arises from the coexistence of heterogeneous cells and increase the small cell capacity. The approaches described here consider the use of multiple antenna technology to use the angular dimension as a new spectrum opportunity. The small cell models its transmissions by placing nulls in the directions of the MUEs, thus protecting the macrocell DL transmissions. In addition, the small cell performs an appropriate resource allocation process for its UE to increase its communication capacity. The MuSiC algorithm is used to estimate the DoAs of the UE signal replicas in an indoor environment, assuming a variable number of multipath components that are characterized by a very large angle spread. The quality of the solutions described in this chapter is shown by providing a performance comparison with other benchmark methods in terms of both small cell capacity and the BER of the macrocell DL.