Abstract
We introduce an efficient multiuser scheduling method using amplify-and-forward relaying in relay-aided downlink systems, consisting of one base station (BS), one relay station, and multiple mobile stations (MSs). In our scheme, the BS opportunistically selects both the transmission mode, that is, either one- or two-hop transmission, and the desired user (i.e., the desired MS). Closed-form expressions for the average achievable rates are derived for the two transmission modes with multiuser scheduling, and its asymptotic solutions are also analyzed in the limit of large number of MSs. Based on the analysis, we propose a feedback-efficient two-step multiuser scheduling algorithm: the transmission mode selection followed by the user selection that only needs a partial feedback for instantaneous signal-to-noise ratios (SNRs) to the BS. We also analyze the average SNR condition such that the multiuser diversity gain is fully exploited for two-hop transmission. The proposed two-step scheduling algorithm exhibits the quite comparable achievable rates to those of the optimal one using full feedback information, while its required feedback information is reduced by half of the optimal one.
Highlights
Cooperative relaying transmission techniques have widely been studied owing to the advantages of both enhancing the end-to-end link quality in terms of system capacity and extending the coverage [1]
There have been intensive prior studies on considering half-duplex two-hop relay cooperation strategies, which include a variety of novel techniques such as distributed space-time coding [3, 4] and relay station (RS) selection [5], where one base station (BS), one mobile stations (MSs), and multiple RSs are deployed in wireless cooperative systems
The half-duplex two-hop relay schemes in [3,4,5] induce the loss of system capacity up to the pre-log factor 1/2 [6] and cannot always guarantee a better performance on the system capacity compared to the one-hop transmission case
Summary
Cooperative relaying transmission techniques have widely been studied owing to the advantages of both enhancing the end-to-end link quality in terms of system capacity and extending the coverage [1]. Under the relay-aided downlink system with one RS support, when the BS is assumed to serve only one MS, one may design a practical achievable scheme along with user scheduling, which requires no complex multiuser detection and yields an easier implementation. In this case, the best scheduling method is for the BS to simultaneously select both the transmission mode and the desired user (i.e., the desired MS) among all users, based on instantaneous signal-to-noise ratios (SNRs) of one- and two-hop links, including the channel conditions, thereby requiring the huge amount of feedback information. All logarithms are assumed to be to the base 2
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