multiplexing gain of NTX antennas [76]. In addition, the scaling of Nfeedback guaran- tees that the throughput loss relative to zero-forcing (ZF) precoding with perfect CSI knowl- edge at the transmitter is upper bounded by NTX bps/Hz, which corresponds to approximately 3 dB power offset. The throughput of a feedback-based ZF system is bounded, if the SNR approaches infinity and the number of feedback bits per user is fixed. Reducing the number of feedback bits according to Nfeedback = clog2 Y for any a NTX - 1 results in a strictly inferior multiplexing gain of NTx[a/(NTX - 1)] where NTX is the number of transmit antennas and V is the SNR of the downlink channel. In order to calculate the amount of feedback required to maintain certain throughput, the difference between the feedback rates of ZF precoding with perfect feedback RPF-ZF(Y) and with limited feedback RLF-ZF(Y) is required to satisfy the following constraint AR(y) = Rpf-zf(Y) - RLF-ZF(Y) < log2b. In order to maintain a rate offset less than log2b (per user) between ZF with perfect CSI and with finite-rate feedback (i.e., AR(Y) VI log2b, , it is sufficient to scale the number of feedback bits per user according to Nfeedback - - 1)log2(b - 1). The rate offset of log2b (per user) is New Radio Access Physical Layer Aspects (Part 2) 571 translated into a power offset, which is a more useful metric from the design perspective. Since a multiplexing gain of NTX is achieved with ZF, the ZF curve has a slope of NTX bps/Hz/3 dB at asymptotically high SNR. Therefore, a rate offset of log2b bps/Hz per user corresponds to a power offset of 3 log2b decibels. To feedback Nfeedback bits through uplink channel, the throughput of the uplink feedback channel should be larger than or equal to Nfeedback, that is, WFBlog2(1 ^FB) Nfeedback where YFB denotes the SNR of the feedback channel. Thus the required feedback resource to satisfy the constraint AR(y) < log2b can be shown to be given as follows (NTX - 1)log2(b - log2(1+YFB), that is, the required feedback resource is a f