Transmission Cooperative Strategies for MIMO-OFDM Heterogeneous Networks

Abstract

Mobile traffic in cellular networks is increasing exponentially, mainly due to the use of data intensive ser- vices like video. One way to cope with these demands is to reduce the cell-size by deploying small-cells along the coverage area of the current macro-cell system. The de- ployment of small-cells significantly improves indoor cov- erage. Nevertheless, as additional spectrum licenses are difficult and expensive to acquire it is expected that the macro and small-cells will coexist under the same spec- trum. The coexistence of the two systems results in cross- tier/inter-system interference. In this context, we design several interference alignment based techniques for the downlink of heterogeneous networks, in order to cancel the interference generated from macro-cell at small-cell user terminals. More specifically, in this contribution we design interference alignment methods under different levels of inter-system coordination and the constraint that the per- formance of macro-cell system is kept close to the case where small-cell system is switched-off. Numerical results demonstrate that the proposed methods achieve close to the optimal performance with low overhead.