Inter-cell scheduling in wireless data networks

Over the past few years, the design and performance of channel-aware scheduling strategies have attracted huge interest. In the present paper we examine a somewhat different notion of scheduling, namely coordination of transmissions among base stations, which has received little attention so far. The inter-cell coordination comprises two key elements: (i) interference avoidance; and (ii) load balancing. The interference avoidance involves coordinating the activity phases of interfering base stations so as to increase transmission rates. The load balancing aims at diverting traffic from heavily-loaded cells to lightly-loaded cells. We consider a dynamic scenario where users come and go over time as governed by the arrival and completion of random data transfers, and evaluate the potential capacity gains from inter-cell coordination in terms of the maximum amount of traffic that can be supported for a given spatial traffic pattern. We also show that simple adaptive strategies achieve the maximum capacity without the need for any explicit knowledge of the traffic characteristics. Numerical experiments demonstrate that inter-cell scheduling may provide significant capacity gains, the relative contribution from interference avoidance vs. load balancing depending on the configuration and the degree of load imbalance in the network.