Max–Min Fairness Optimization for D2D Communications Coexisting with Cellular Networks
Faculty of Electronics Telecommunication & Information Technology, Hanoi Open University, Hanoi 100000, Vietnam
School of Electronics and Telecommunications, Hanoi University of Science and Technology, Hanoi 100000, Vietnam
Department of Information and Communication, Kongju National University, Cheonan 31080, Korea
Author to whom correspondence should be addressed.
Electronics 2020, 9(9), 1422; https://doi.org/10.3390/electronics9091422
Received: 30 July 2020 / Revised: 28 August 2020 / Accepted: 29 August 2020 / Published: 2 September 2020
(This article belongs to the Special Issue Access Technology in 5G and Mobile Communication Networks)
This paper considers a system consisting of a nonorthogonal multiple access (NOMA)-based device-to-device (D2D) communication system within a cellular network, in which the time and frequency resources are shared by everyone. In particular, D2D groups that constitute different pairs are assigned to the subchannels that the cellular users occupy. A max–min fairness optimization problem with power budget constraints is formulated and solved in this paper to reduce the mutual interference between the cellular users and D2D devices that substantially impacts that with the worst channel condition. For a low computational complexity solution, we propose the use of the bisection method together with the solution of a system of linear equalities. The proposed algorithm can provide uniformly good service to all of the cellular users and D2D devices in the coverage area by utilizing the minimal total transmit power. The simulation results indicate the effectiveness of the proposed algorithm in the improvement of the spectral efficiency of the worst user under the different widely used subchannel assignments and pairing techniques.