Multi-BS Cooperative Interference Control for LTE Systems

Inter-Cell Interference Coordination (ICIC) is attracting attention recently. In ICIC, cell-edge throughput can be improved by preventing BSs from transmitting signals (hereafter, muting BSs), and the information exchange among BSs is little because each UE is only served by a BS at any instant. However, when a BS is muted, no radio resource is allocated to UEs belonging to the muted BS while UEs belonging to other BSs enjoy high cell-edge throughput. Therefore, there is a possibility that overall cell performance may degrade. To prevent this, we propose a multi-BS cooperative interference control method. The basic concept of the proposed method is that the muting is triggered only when the total throughput of the cooperation area is increased by the muting compared to the total throughput possible without muting. The proposed method makes it possible to increase cell-edge throughput without degrading overall cell performance. We also propose a way to realize this interference control on practical systems. First, we propose a way to realized it on 3GPP Release 8 LTE systems. In the proposed interference control, it is important to estimate throughput (SINR) values with and without muting appropriately. We propose to utilize feedback signals defined in LTE such as Channel Quality Indicator (CQI) and Received Signal Received Power (RSRP) to achieve the accurate throughput estimation. Furthermore, we propose to realize the proposed interference control on a distributed sector configuration using optical fiber systems such as Radio over Fiber (RoF) or Remote Radio Head (RRH). With this configuration, it is possible to achieve ICIC with less burden of information exchange. Especially with three sector configuration, it is possible to achieve "inter-cell" cooperation with "inter-sector" cooperation, which can be easily implemented.