 between the feedback rates of zero-forcing precoding with perfect feedback and with limited feedback is required to satisfy the following constraint AR(p) = RPF-ZF(p) - RLF-ZF(p) < log2b. In order to maintain a rate offset less than log2b (per user) between zero-forcing with perfect CSI and with finite-rate feedback (i.e., AR(p) < log2b, Ap), it is sufficient to scale the number of feedback bits per mobile according to B = PdB(Nt - 1)/3 (N 1)log2(b - 1). The rate offset of log2b (per user) is translated into a power offset, which is a more useful metric from the design perspective. Since a multiplexing gain of N is achieved with zero-forcing, the zero-forcing curve has a slope of N bps/Hz/3 dB at asymptotically high SNR. Therefore, a rate offset of log2b bps/Hz per user corresponds to a power offset of 3log2b decibels. To feedback B bits through uplink channel, the throughput of the uplink feedback channel should be larger than or equal to B, i.e., WFBlog2(1 + PFB) B 10.4 Multi-antenna transmission schemes where PFB denotes the SNR of the feedback channel. Thus, the required feedback resource to satisfy the constraint AR(p) < log2b can be shown to be given as follows WFB > [PdB(N t - 1)/3 - (N t log2(b - 1)]/log2(1 + PFB), i.e., the required feedback resource is a function of both downlink and uplink channel conditions. We defined precoding as adaptive or non-adaptive weighting of the spatial streams prior to transmission from each antenna port (in a multi-antenna configuration) using a precoding matrix to improve reception or separation of the spatial streams at the receiver. Both feed-back and feed-forward precoder matrix selection schemes can be used in order to select the optimal weights. Feed-back precoding matrix selection techniques do not rely on channel reciprocity, rather they use feedback channels, provided that the feedback latency is less than the channel coherence time. In feed-forward approaches, the necessary CSI can be theoretically obtained through direct channel feedback where the CSI is expli