Performance of Cooperative Multi-Cell Downlink Communication Aided by Polarization-Multiplexing Under Limited Feedback Constraints

In this correspondence, we investigate the performance of a multi-cell multiple-input multiple-output downlink (DL) system aided by base station (BS) cooperation, relay cooperation, and polarization-multiplexing (PM). Triply-polarized antennas that are employed at the BSs, relays, and mobile stations (MSs) to conceive PM serve as an replacement for multiple uni-polarized antennas that inflict space limitation. In a multi-user multi-cell relay-aided scenario, MSs and relays conflict multi-user interference (MUI) as well as inter-cell or co-channel interference (CCI). Furthermore, the MSs experience intra-relay interference and inter-relay interference. In this paper, both the MUI and CCI at the relays are completely removed by the combined preprocessing operated at the BS. Similarly, the intra-relay and inter-relay interference are eliminated with the aid of the joint preprocessing operated at the relays. Specifically, in this contribution, the performance of the considered system is investigated when the channel state information (CSI) required at the BSs to implement the joint preprocessing suffers from feedback and back-haul delays. In our contribution, feedback channels that convey the CSI to the BSs endure noise and fading as well. Our simulation study demonstrates that the use of triply polarized antennas in combination with joint preprocessing at the BSs and relays can be regarded as an efficient technique for the cooperative multi-cell DL system to deal with the space constraints and the aforementioned interferences. Furthermore, the considered preprocessing results in superior symbol-error-rate performance compared with other preprocessing approaches.