Abstract
Backscatter communication (BackCom) is a promising technique for
achieving high spectrum efficiency and power efficiency in the future
Internet of Things systems. The capacity of BackCom networks can be
maximized by optimizing the backscatter time and the reflection
coefficient (RC). However, system energy efficiency (EE) cannot be
guaranteed usually. In this paper, we investigate the energy-efficient
resource allocation problem of a non-orthogonal multiple access
(NOMA)-based BackCom. Particularly, the base station (BS) transmits
signals to two cellular users based on the NOMA protocol, meanwhile, a
backscatter device backscatters the signals to users using the passive
radio technology. The total EE of the considered system is maximized by
jointly optimizing power allocation for each NOMA user and the RC of
backscatter device where the decoding order and the quality of service
(QoS) of each user are guaranteed. To solve such a non-convex problem,
we develop an efficient iterative algorithm to obtain the optimal
solutions by using Dinkelbach’s method and the quadratic transformation
approach. Numerical results show that the proposed algorithm can
significantly improve the system EE compared with the orthogonal
multiple access (OMA) scheme and the NOMA system without backscatter
devices.