User-Pair Scheduling and Mode Selection in Asymmetric Full-Duplex Systems With Limited Feedback: Algorithm and Scaling Laws

摘要

Determining which users to simultaneously schedule on the uplink and the downlink in a full-duplex (FD) system is crucial to control the inter-user interference between them and achieve a high spectral efficiency. The user-pair scheduling algorithm and the efficacy of FD is, thus, closely linked to the availability of channel state information and the feedback scheme that conveys it to the base station (BS). We consider a reduced feedback scheme in which a user that is scheduled feeds back only a limited number of quantized inter-user interferences that are below a pre-specified threshold. For it, we propose a novel user-pair scheduling and mode selection algorithm (UPSMA). We analyze the uplink and downlink spectral efficiencies of UPSMA for two channel models that highlight the different influences of small-scale fading and large-scale shadowing. We derive insightful asymptotic scaling laws that quantify the dependence of the threshold and the uplink and downlink spectral efficiencies on the number of users. UPSMA with limited feedback achieves a higher sum spectral efficiency than a half-duplex system and conventional FD resource allocation algorithms. Its performance is close to the exhaustive search algorithm in which the BS knows all the inter-user interferences.