Fast Distributed Multi-Cell Scheduling with Delayed Limited-Capacity Backhaul Links

Both fast scheduling and spatial signal processing have proven to be capacity-increasing methods in wireless communication systems. However, when applied in the downlink of a cellular network, the combination of both leads to non-stationary intercell interference. If the base stations do not cooperate, either they have to encode the data very conservatively to gain robustness or the non-stationary fluctuations of the interference powers lead to frequent outages, both of which strongly impair the average achievable throughput. On the other hand, base station cooperation increases complexity and delays, contradicting the desire for fast scheduling algorithms. In this paper, we propose a scheme that makes average channel state information available to all base stations via low-rate backhaul communication, whereas high-rate inter-base-station communication is limited to B ⌈log2 K⌉-bit integers, K being the number of users in each of the B cells. Simulations show that for slow fading channels, the proposed algorithm preserves most of the per cell sum-rate of other beamforming and dirty-paper coding approaches that have unlimited-capacity backhaul links. Furthermore, when out-of-cell information is outdated the proposed algorithm even outperforms those.