Non-orthogonal multiple access (NOMA) is a novel multi-user multiplexing scheme that improves spectral efficiency for LTE enhancements and 5G. By overlapping radio resources (e.g., time/frequency/code), but assigning different powers to the multiplexed users, NOMA is able to improve the system performance and fairness. In this paper, we review the concept of combining downlink NOMA with MIMO. Then, we introduce our experiment trials conducted to assess the performance of downlink NOMA combined with MIMO under realistic conditions. The sets of experimental trials are conducted in outdoor environments, one using NOMA combined with open-loop 2×2 MIMO and another using NOMA combined with closed-loop 4×2 MIMO.

Combination of NOMA and MIMO: Concept and Experimental Trials

Non-orthogonal multiple access (NOMA) is a novel multi-user multiplexing scheme that improves spectral efficiency for LTE enhancements and 5G. By overlapping radio resources (e.g., time/frequency/code), but assigning different powers to the multiplexed users, NOMA is able to improve the system performance and fairness. To assess the performance of downlink NOMA under realistic conditions and confirm its feasibility with real hardware, we conducted experimental trials in outdoor environments using smartphone-sized NOMA chipset-embedded devices. This paper introduces our trial setup and trial results of NOMA combined with closed-loop 4x2 SU-MIMO.

Outdoor Experimental Trials of Advanced Downlink NOMA Using Smartphone-Sized Devices

Non-orthogonal multiple access (NOMA) is a novel multi-user multiplexing scheme, which overlaps the radio resources of multiple users in an non-orthogonal manner in order to improve spectral efficiency. NOMA is able to contribute to the improvement of the trade-off between system capacity and user fairness by assigning different power ratios to the multiplexed users depending on their relative channel quality. In this chapter, we focus on downlink NOMA and its combination with open-loop SU-MIMO and assess its performance under realistic conditions. In particular, we introduce the results of the experimental trials we conducted in both indoor and outdoor environments using two users served by 2 \(\times \) 2 open-loop single-user (SU)-MIMO.

Experimental Trials on Non-Orthogonal Multiple Access

The application of compressed sensing (CS) theory to non-orthogonal multiple access (NOMA) systems has been investigated recently. As described in this paper, we propose a quality-of-service (QoS)-aware, low-complexity, CS-based user selection and power allocation scheme with adaptive resource block selection for downlink NOMA systems, where the tolerable interference threshold is designed mathematically to achieve a given QoS requirement by being relaxed to a constrained l1 norm optimization problem. The proposed scheme adopts two adaptive resource block (RB) selection algorithms that assign proper RB to user pairs, i.e. max-min channel assignment and two-step opportunistic channel assignment. Simulation results show that the proposed scheme is more effective at improving the user rate than other reference schemes while reducing the required complexity. The QoS requirement is approximately satisfied as long as the required QoS value is feasible. 

Xu Zhang

Papers

Investigation on Non-Orthogonal Multiple Access with Reduced Complexity Maximum Likelihood Receiver and Dynamic Resource Allocation