Efficient Bit Loading Algorithm for OFDM-NOMA Systems with BER Constraints

Abstract

This paper considers applying bit loading to multicarrier non-othogonal multiple access (NOMA) systems. The objective is to maximize the system total throughput while satisfying the users' individual quality of service (QoS) constraints. Although bit loading is generally an NP-hard problem, even for orthogonal multiple access (OMA), the mutual interference between the users and the dependence of power coefficients and modulation orders are additional challenges that add substantial complexity to the optimization problem. Therefore, we propose in this paper an efficient bit loading algorithm for multicarrier NOMA systems and compares the complexity and throughput with OMA. The obtained results show that NOMA has virtual cognition and hybrid modes of operation, NOMA/OMA, that enables NOMA to outperform OMA by 100% for the two-user scenario. The complexity of the loading process for NOMA is noticeably higher than OMA, which is due to the high computational complexity of bit error rate (BER) computation for NOMA. The obtained results show that the NOMA throughput depends on which user is loaded first, and on the initially loaded bits.

Error Rate Analysis of NOMA: Principles, Survey and Future Directions

“…1) Maximum Throughput Design: For instance, references [69]- [71] study resource allocation of two-user DL NOMA system to maximize the sum rate using practical modulation schemes such as M n -QAM while satisfying BER constraints. Unlike single carrier systems [71], maximizing the sum rate in multicarrier systems is non-deterministic polynomial-time hard problem which requires highly complex exhaustive search [69], [70]. Therefore, it is important to design efficient algorithms.…”

“…Assaf et al [70] design an efficient iterative greedy algorithm to maximize the system's throughput while satisfying the users BER constraints. Adaptive modulation, fixed power allocation and hybrid OMA/NOMA are utilized by the design.…”

Design and Analysis of NOMA With Adaptive Modulation and Power Under BLER Constraints

“…Similar to the link-level simulator approach, [4] designs an algorithm aiming at maximizing the minimum user rate while achieving user fairness. The authors of [5] consider a two-user DL multicarrier NOMA and propose an efficient adaptive modulation algorithm to maximize the throughput while satisfying individual users' bit error rate (BER) constraints. However, the throughput is evaluated only using simulation and the system adopts fixed power assignment (FPA).…”