Hierarchical radio resource optimization for heterogeneous networks with dynamic ABS

Interference is a major performance bottleneck in Heterogeneous Network (HetNet). The LTE-A working groups are actively studying enhanced inter-cell interference coordination (eICIC) techniques such as almost blank subframes (ABS). We propose a two timescale hierarchical radio resource management (RRM) scheme for HetNet with dynamic ABS control. The long term controls, such as dynamic ABS, are adaptive to the large scale fading at a RRM server for interference control. The short term control (user scheduling) is adaptive to the local channel state information (CSI) within each BS to exploit the multi-user diversity. Such hierarchical RRM has low signaling overhead, good scalability, and robustness w.r.t. latency of the backhaul signaling. The two timescale optimization problem is challenging due to the exponentially large solution space. We exploit the sparsity in the HetNet interference graph and derive structural properties for the optimal ABS control. Based on that, we propose a two timescale alternative optimization solution which has low complexity and is asymptotically optimal at high SNR.