Over-the-Air Implementation of NOMA: New Experiments and Future Directions

Abstract

Non-orthogonal multiple access (NOMA) is widely recognized to increase the number of users and enhance the spectral efficiency in fifth-generation (5G) wireless networks and beyond. NOMA is still in the theoretical analysis and simulation phases and fewer experimental works are reported to date. In this paper, we design and implement NOMA in software-defined radio, and evaluate its performance. This includes the real-time realization of the key components of NOMA, i.e., superposition and successive interference cancellation. The main novelty of this paper is to introduce constructing superimposed signals with varying symbol rates to enlarge the achievable rate region of the experimented NOMA. By applying varying symbol rates, the set of possible transmission rate pairs enlarges and we can reach higher data rates compared to existing modulation and coding schemes (MCS). We also propose an algorithm to efficiently find the rate pairs. Simulations and experiments demonstrate that NOMA with a varying symbol rate not only can reach higher data rates than orthogonal schemes such as time division multiple access, but it can also outperform existing MCS-based methods which have a fixed symbol rate. The experiments also show that there is a noticeable gap between NOMA in theory and practice. In addition to the new NOMA experiments, we review the state-of-the-art in experimental NOMA. We also discuss several directions for future experiments that can help bridge the gap between theory and practice and bring NOMA to practical communication systems.

Bit-Interleaved Multiple Access: Improved Fairness, Reliability, and Latency for Massive IoT Networks

“…Therefore, the practical systems take their values from finite alphabet inputs such as a M-level quadrature-amplitude modulation (M-QAM) constellation. In this regard, once a baseband transceiver is implemented, it has been shown that the imperfect SIC cannot be modeled only by a coefficient, and NOMA networks have a degradation of error performance (bit error rate, BER) for both downlink [26], [27] and uplink [27], [28] scenarios. These studies led other researchers to investigate the BER performance of NOMA systems with finite alphabet inputs to reflect their practical implementations.…”

“…By substituting the PDF of the ith maximum ( 16) into (54), the MGF of γ i is given as Finally, as defined in (26), we put s=− g sin 2 θ into MGF (D.3), the bit error probability is derived as (27), so the proof is completed.…”

A Hybrid Energy Harvesting Protocol for Cooperative NOMA: Error Performance Approach

“…At the S, the messages of users are combined in an SC information signal with different power levels according to the users' channel gain 1 and the R receives this information signal in the first phase. Thus, the received information signal by the R node is given as…”

“…Non-orthogonal multiple access (NOMA) is widely renowned for increasing the number of users and improving spectral efficiency in next-generation wireless networks [1]. Besides, NOMA can be easily integrated with other physical layer schemes.…”

Performance evaluation of Non‐Orthogonal multiple access system based on outage probability and power consumption

“…The primary methods for SISO‐NOMA are successive interference cancelation (SIC) at the receiver and SC at the transmitter 7 . NOMA faces several challenges that must be addressed for its practical implementation and deployment in wireless communication systems.…”