Dynamic Cooperation Link Selection for Network MIMO Systems with Limited Backhaul Capacity

Base-station (BS) cooperation in wireless cellular networks offers a promising approach for interference mitigation. However, the implementation of practical network multi-input multi-output (MIMO) system also faces the challenge of high capacity cost for sharing the user data over the backhaul connections. This paper considers a downlink multi-cell orthogonal frequency-division multiple-access (OFDMA) network where the capacities of the backhaul links between the BSs are limited, and extends the single-antenna BS multi-cell system model considered in our previous work to the multiple-antenna BS case. The BSs use zero-forcing precoding to spatially multiplex multiple users within each cell and to pre-subtract the interference from cooperating BSs that share user data with them. An iterative algorithm that maximizes the downlink network utility is proposed. The algorithm iteratively selects the cooperation links, schedules the users, and optimizes the precoding coefficients and the power spectra for each frequency tone. Numerical results suggest that the use of dynamic cooperation link selection can provide a better trade-off between the downlink sum-rate gain and the backhaul capacity than the earlier fixed link-selection algorithm.