Uplink multi-BS MIMO with limited backhaul bandwidth1

Uplink collaborative multiple-input-multiple-output (MIMO) processing among multiple base stations (BSs), also known as uplink multi-BS MIMO, is an effective way to solve the inter-cell interference in cellular systems. However, the significantly increased overhead on the backhaul network due to inter-BS information exchange has seriously restricted its application in practical systems with limited backhaul bandwidth. In this paper, we propose a three-stage technique for inter-BS information exchange in uplink multi-BS MIMO. A sub-optimal coordinated detection algorithm based on soft combining is considered to compromise between the performance and overhead. The major improvement over the existing solutions is that the proposed technique utilizes one property of soft combining to reduce the backhaul overhead: soft information combination is only needed for a very small part of the information bits that have mismatched local decoding results in different BSs. A three-stage information exchange technique is proposed to utilize this property, which allows the BSs to first locate the bits that need soft information combination and then exchange soft information for these bits only. By doing so, the backhaul overhead can be greatly reduced without performance degradation. Both simulation results and overhead analysis are used to demonstrate the benefit of the proposed technique. Comparisons with other coordinated detection algorithms like optimal joint detection and distributed interference cancellation show that it can provide a better tradeoff between the performance and overhead.