CSI Distribution for Joint Processing in Cooperative Cellular Networks

Abstract

Interference mitigation by applying Joint Processing (JP) in cooperative cellular networks boasts cell-edge performance compared to non-cooperative systems. However, downlink JP requires knowledge of Channel State Information (CSI) at all collaborating Base Stations (BSs), where interference received at the User Equipments (UEs) is markedly affected by the level of CSI quality influenced amongst others by the method of distributing CSI to the BSs. In this contribution, we compare CSI Distribution over the Air (CD-A) with CSI Distribution over the Backhaul (CD-B) considering a Frequency Devision Duplex (FDD) system. For CD-A, CSI is directly fed back from the UEs to the collaborating BSs via the uplink channel (assuming link adaptation is performed according to one master BS to which a UE has been assigned). Adopting CD-B, CSI is foremost transmitted only to the master BS and then forwarded to the other BSs using backhaul connections. This method typically introduces additional latency due to routing issues. In this contribution, we show that CD-A outperforms CD-B in the largestpart of the cooperation area, even when pedestrian user velocities and small backhaul latencies are considered.

On the impact of control channel reliability on coordinated multi-point transmission

“…The fully distributed architecture, introduced in [25] and [31], is depicted in Figure 4. This architecture differs from the semi-distributed architecture (Section 3.3) in the way TN n acquires the full CSI matrixĤ n .…”

On the Evolution of Coordinated Multi-Point (CoMP) Transmission in LTE-Advanced

“…Unlike the other two architectures, in fully-distributed CoMP architecture [43], every UE broadcasts their CSI reports to their all cooperated BSs via radio access link. Based on the gathered CSI each BS independently constructs the precoding matrix for JT-CoMP scheme or designs scheduling decisions for the CS-CoMP scheme.…”

Egoistic vs. altruistic beamforming in multi-cell systems with feedback and back-haul delays

“…While joint precoding, which requires CSI and user data sharing, provides the highest sum rate in an ideal CSI setting, it comes at a cost of large back-haul load and high overhead and complexity [7]. These factors, specially the capacity of the back-haul link, determine the level of cooperation and http://jwcn.eurasipjournals.com/content/2013/1/253 which exchange CSI over the back-haul network suffer the most since an extra back-haul latency can cause significant CSI outdating [15,16]. In frequency division duplex (FDD) systems, channel state information can only be delivered to the transmitter using limited feedback which further contributes to CSI inaccuracy [17,18].…”