Determining backhaul bandwidth requirements for network MIMO

In systems employing coordinated base station transmission and reception (also known as network MIMO), information needs to be shared among clusters of coordinated bases. This information includes coherent channel state information, user data, and baseband received signals. The cost of leasing and maintaining a reliable backhaul to share this information will be the dominant operational expense for cellular systems with network MIMO. In this paper we analyze the bandwidth requirements for sharing information among coordinated bases for network MIMO as a function of the coordination cluster size and channel characteristics. We find that for moderate Doppler speeds, the channel state information is a negligible fraction of the overall backhaul bandwidth. We also show that sending linearly quantized baseband signals over the backhaul achieves a significant fraction of ideal unquantized sum rate performance for uplink network MIMO based on zero-forcing.