Beamforming and Reflection Coefficient Control for Multiantenna Backscatter Communication With Nonorthogonal Multiple Access

Abstract

For ultralow-power Internet of Things, we consider a monostatic multiantenna backscatter communication network (MBCN) supporting massive devices through nonorthogonal multiple access (NOMA) over space division multiple access (SDMA). For the network, we optimize the transmit beamforming (BF) for signal excitation of a reader, reflection coefficients of devices for backscattering and energy harvesting, and receive BF for information decoding at the reader toward the maximum fairness in data collection. We first show that the optimization problem for the MBCN without successive interference cancellation (SIC) has a similarity with the problem considered for a wireless power communication network but the conventional algorithm is not applicable to the MBCN with SIC. Thus, we propose a new alternating optimization algorithm that is applicable to both problems with and without SIC at a lower complexity. Simulation results show that the proposed algorithm provides a remarkable gain over the conventional one for the MBCN with SIC while exhibiting a similar performance for the MBCN without SIC. In addition, NOMA/SDMA enhanced by the proposed algorithm increases the minimum system throughput as well as the total energy harvested in the network by utilizing limited resources more effectively for a larger number of devices.

On the Design of NOMA-Enhanced Backscatter Communication Systems

“…Driven by the potential and popularity of the integration of the PD-NOMA scheme and monostatic BackCom, several studies have recently addressed the design and performance evaluation for static NOMA-aided monostatic BackCom systems [22], [23], [24], [25], [26]. Particularly, Jing et al provided the design guideline for the monostatic Back-Com systems using a hybrid time-division multiple-access (TDMA)/PD-NOMA scheme, where the reflection coefficients for the multiplexed BNs from different NOMA groups are set to different values to utilize the PD-NOMA [22].…”

“…In [23], the authors introduced a mechanism to reduce the collisions in NOMA-aided BackCom systems, where a power level threshold for BNs was considered in the backscattering phase. The authors in [24] addressed the performance of NOMA-aided monostatic multiantenna BackCom systems, in which a space division multiple access (SDMA) scheme was employed. In [25], the authors presented a transmitted power-driven channel access scheme, which controls the number of BNs contending the channel by tuning the transmitted power of the illuminator incrementally.…”

“…Such hybrid systems not only exploit different multiplexing domains to improve the system performance but also facilitate the practical implementation of NOMA in massive IoT [29]. Aside from [22] and [24], to the best of our knowledge, there are no other studies addressing the design of hybrid OMA/PD-NOMA for monostatic BackCom systems. More importantly, the design framework for dynamic NOMA-aided monostatic BackCom systems is still not available in the literature.…”

Investigation of Backscatter-Enabled Partial NOMA Systems: Outage Probability and Ergodic Capacity Evaluation

“…In [11], Elsayed et al derived exact and asymptotic closed-form OP solution for symbiotic-radio users, who wish to receive signals from both primary and secondary transmitters, when the system operates in Nakagami-m fading medium. In [13], Sacarelo et al provided a guidance framework on jointly optimizing the transmit beamforming weights and backscattering coefficients to achieve the maximum rate fairness in a monostatic multi-antenna AmBC-enabled NOMA systems. In [14], Le et al showed the advantages of AmBC-enabled NOMA in conjunction with cognitive radio (CR) networks to achieve high spectrum utilization, where a base station cognitively communicates with two secondary users via a relay node capable of collect/decode and backscatter its received signal simultaneously.…”