Multi-BS Cooperative Interference Control for LTE Systems

Abstract

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.

Comprehensive Analysis of Heterogeneous Networks with Pico Cells in LTE-Advanced Systems

“…In addition, several other functions, such as timing synchronization with the BS and the UE, as well as radio resource coordination between the link from the Relay to the UE and the link from the BSs to the Relay [11]. According to [12], the transmission power is assumed from 0.1 W (or 20 dBm) to 5 W (or 37 dBm) as for evaluation purposes.…”

“…The transmission power of an RRH can be identical to that of various BSs such as the Macro-BS and Pico-BS. On the other hand, an RRH has an advantage over a Pico-BS from the viewpoint of easy adoption of functions requiring coordination and cooperation among multiple BSs, such as coordinated multiple transmission and reception points (CoMP), since all BBUs connected to RRHs and radio resource management functions for them are generally co-located [12].…”

“…Figure 9 shows the throughput performances when the CRE bias value changes. Since a non-full buffer traffic model is used, a metric named "user-perceived throughput (UPT)" is applied [12]. The UPT is defined as the total number of bits successfully transmitted for the UE divided by the length of time when data is queued at the transmission buffer for the UE.…”

Analytic estimation for uplink capacity reduction due to co-channel interference in LTE networks

“…Most studies focused on the fractional frequency reuse (FFR) technique to mitigate the intercell interference. Ogata et al [11] indicated that intercell interference would severely impact cell-edge user performance and overall system throughput. As we know, the intercell interference comes mainly from co-channel signals.…”

Multiple-CSI selection methods for CoMP downlink

“…An eNodeB configures its UEs to measure the signal strength from serving TP and the Example of different CoMP schemes interference outside the serving TP to obtain the CSI. However, in order to support CoMP operation, multiple types of CSI, which are also referred to as CSI processes [4], from each cooperating TP assuming different interference hypotheses are needed [5], [6]. For CoMP transmission, a CSI process is defined as a combination of a signal measurement resource (SMR) and an interference measurement resource (IMR) [7].…”