Feedback of channel state information using the digital reverse link

In this paper, we focus on a cellular system with M transmit antennas at the base station (BTS) and one receive antenna at the mobile (i.e. an M-input/single-output (MISO) channel), where the BTS commands each mobile to transmit its channel state information back to the BTS. Our main result is a specific method for each mobile to use the uplink channel to inform the BTS of the state of its M downlink channels. This feedback method is particularly well-suited for wireless packet data cellular systems on the downlink where the entire downlink channel is allocated to one downlink user at a time (e.g. a cellular packet data system employing proportional fairness type scheduling on the downlink). We show that with a small portion of uplink channel resources devoted to feedback of channel state information per site, our feedback method results in a performance very close (within 1dB) to the performance that can be obtained with perfect channel knowledge at the BTS.