Dual-Timescale Spectrum Management in Wireless Heterogeneous Networks

To attain the targeted data rates of next generation (5G) cellular networks requires dense deployment of small cells in addition to macro cells which provide wide coverage. Dynamic radio resource management (RRM) is crucial to the success of such heterogeneous networks due to much more pronounced traffic and interference variations in small cells. This work proposes a framework for spectrum management organized according to two timescales, which includes 1) centralized optimization on a second/minute timescale corresponding to typical durations of user sessions, and 2) distributed spectrum allocation on a millisecond timescale corresponding to typical latency requirements. The dualtimescale allocation is formulated as an optimization problem in the slower timescale with consideration of (distributed) opportunistic scheduling on the faster timescale. We consider both fixed and fully flexible user association. Iterative algorithms are developed to solve these optimization problems efficiently for a small cluster of cells. Simulation results demonstrate advantages of the dual-timescale RRM framework.