Multiuser MIMO BC Scheduling with Channel Quantization
摘要
Multiple-Input Multiple-Output (MIMO) systems transmit independent and separately encoded data streams to multiple users terminals (UT). We select a subset of UTs with the best channel quality to whom the base-station (BS) antennas transmit during a time slot. The channel information is needed to determine the list of scheduled users, which significantly increases the overhead associated with feedback. For a multiuser system, obtaining full channel state information (CSI) from all users may not be feasible. In this article, we present two sub-optimal scheduling methods in a Multiuser MIMO (MU-MIMO) broadcast channel (BC channels). Transmit zero forcing (ZF) beamforming along with user selection is used. In the first method, each of the antenna at the UTs is considered as a virtual user with single antenna and from these virtual users a set of users are selected to whom the base station antennas transmit independent stream of data. In the second method, we introduced fairness by which one antenna per user can only be selected.This provides equal opportunities to all UTs to participate in the scheduling process. From the achieved sum rate capacity of both the methods, it is observed that the second method is found to perform better at low signal-to-noise ratios (SNRs), while the first method outperforms the second method at higher SNRs. We take the quantized channel into consideration to minimize the amount of feedback information delivered. We are delivering the codebook index, which is the quantized channel, rather than the entire CSI. A comparison is made for the achieved sum rate capacity using the scheduling methods,with and without quantization. The cumulative rate capacities are found to be almost comparable. However, the sum rate capacity decreases somewhat as a result of the decreased amount of feedback data sent.