Busy Burst Enabled Coordinated Multipoint Network with Decentralized Control

A novel decentralized coordinated multipoint (CoMP) technique facilitated by receiver feedback is proposed. If multiple base stations (BSs) access the same radio resource; downlink transmissions from one BS cause co-channel interference (CCI) towards towards users served by neighboring BSs. To mitigate CCI in a multiple-input-multiple-output (MIMO) network, the mobile station (MS) scheduled in a tagged cell (i.e. the active user) emits a busy burst (BB) on a time-multiplexed feedback slot, applying the precoder used earlier for receiving data. Prior to transmission a neighboring BS must scan the feedback slot using the spatial precoder(s) intended for data transmission. Consequently, in a time division duplex (TDD) system the channels of the data and the feedback slots become reciprocal. Therefore, by listening to the feedback slot, a neighboring BS can predetermine the CCI potentially imposed towards the active user for each of its available precoders. This information enables the BS to select spatial precoders autonomously so that CCI is limited to a predetermined threshold. Simulation results demonstrate that the proposed technique achieves 20% increase in spectral efficiency, 6-fold increase in cell-edge user throughput, and 40% reduction in transmitted energy, compared to transmit beamforming without interference coordination.