Mobile User Pairing Scheme in NOMA-Enabled Backscatter Communication Networks

In this paper, we study the problem of mobile user pairing in non-orthogonal multi-access (NOMA) backscatter communication networks, in which re-pairing users after a change in the communication link can bring significant computational overhead. Firstly, We propose a user pairing scheme that employs the Kuhn-Munkres (KM) algorithm for the uplink of the monostatic backscatter communication network, which can effectively avoid the problem of frequent sorting mobile users. Secondly, to address the NOMA principle violations problem (NPVP) caused by mobile users, we propose a modified role switching (RS) technique based on the difference of user channel gain in which paired users switch their roles based on the magnitude of their channel gain after moving. Finally, we propose a dynamic power allocation scheme for mobile users to maximize the system throughput after pairing. In backscatter communication, the difference in power levels between paired users is achieved by setting different reflection coefficients. At the same time, it is necessary to consider the balance between data transmission and energy harvesting, and the reflection coefficient must not exceed the predetermined upper limit. Simulation results indicate that our proposed user pairing scheme outperforms conventional schemes in terms of the number of decoded users and system throughput.