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Entropy 2018, 20(3), 160; https://doi.org/10.3390/e20030160

Revisiting Degrees of Freedom of Full-Duplex Systems with Opportunistic Transmission: An Improved User Scaling Law

1
Affiliated Institute of ETRI, Daejeon 305-390, Korea
2
Department of Electronics Engineering, Sookmyung Women’s University, Seoul 04310, Korea
3
ICT Convergence Research Team, Korea Railroad Research Institute, Eiwang 437-757, Korea
4
Department of Computer Science and Engineering, Dankook University, Yongin 16890, Korea
*
Author to whom correspondence should be addressed.
Received: 5 January 2018 / Revised: 7 February 2018 / Accepted: 1 March 2018 / Published: 2 March 2018
(This article belongs to the Special Issue Information Theory and 5G Technologies)
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Abstract

It was recently studied how to achieve the optimal degrees of freedom (DoF) in a multi-antenna full-duplex system with partial channel state information (CSI). In this paper, we revisit the DoF of a multiple-antenna full-duplex system using opportunistic transmission under the partial CSI, in which a full-duplex base station having M transmit antennas and M receive antennas supports a set of half-duplex mobile stations (MSs) having a single antenna each. Assuming no self-interference, we present a new hybrid opportunistic scheduling method that achieves the optimal sum DoF under an improved user scaling law. Unlike the state-of-the-art scheduling method, our method is designed in the sense that the scheduling role between downlink MSs and uplink MSs is well-balanced. It is shown that the optimal sum DoF of 2 M is asymptotically achievable provided that the number of MSs scales faster than SNR M , where SNR denotes the signal-to-noise ratio. This result reveals that, in our full-duplex system, better performance on the user scaling law can be obtained without extra CSI, compared to the prior work that showed the required user scaling condition (i.e., the minimum number of MSs for guaranteeing the optimal DoF) of SNR 2 M 1 . Moreover, the average interference decaying rate is analyzed. Numerical evaluation is performed to not only validate our analysis but also show superiority of the proposed method over the state-of-the-art method. View Full-Text
Keywords: degrees of freedom (DoF); full-duplex systems; hybrid opportunistic scheduling; partial channel state information (CSI); user scaling law degrees of freedom (DoF); full-duplex systems; hybrid opportunistic scheduling; partial channel state information (CSI); user scaling law
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Kim, H.; Kim, J.; Choi, S.W.; Shin, W.-Y. Revisiting Degrees of Freedom of Full-Duplex Systems with Opportunistic Transmission: An Improved User Scaling Law. Entropy 2018, 20, 160.

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