The DoF of Network MIMO With Backhaul Delays
The authors consider the problem of downlink precoding for Network (multi-cell) MIMO networks where Transmitters (TXs) are provided with imperfect Channel State Information (CSI). Specifically, each TX receives a delayed channel estimate with the delay being specific to each channel component. This model is particularly adapted to the scenarios where a user feeds back its CSI to its serving base only as it is envisioned in future LTE networks. They analyze the impact of the delay during the backhaul-based CSI exchange on the rate performance achieved by Network MIMO. They highlight how delay can dramatically degrade system performance if existing precoding methods are to be used.