Enhanced uplink non-orthogonal multiple access for 5G and beyond systems  

面向5G及未来系统的增强上行非正交多址技术研究（英文）

作　　者：Wen-jia LIU Xiao-lin HOU Lan CHEN 

机构地区：[1]DOCOMO Beijing Communications Laboratories Co., Ltd.

出　　处：《Frontiers of Information Technology & Electronic Engineering》2018年第3期340-356,共17页信息与电子工程前沿（英文版）

摘　　要：Uplink non-orthogonM multiple access （NOMA） is a promising technique to meet the requirements of the fifth generation （5G） and beyond systems. Various NOMA schemes have been proposed in both academia and industry. However, most existing schemes assume equal average received power, which limits the performance. We propose three enhancements of uplink NOMA to achieve the requirements of massive connectivity and high reliability in 5G, where unequal average received power is exploited as part of the multiple access signature. First, the optimal sequences targeting to generalized Welch-bound equality （GWBE） are obtained for unequal average received power. Then user grouping with multi-level received powers is proposed for better successive interference cancellation （SIC） at the receiver. Finally, sequence grouping based on the cross-correlation properties of sequences is proposed to reduce inter-and intra-group interference. Simulation results show that by incorporating multi-level received powers and sequence grouping into existing NOMA schemes, for an NOMA system with 400% overloading and fixed signature allocation, 3 dB and 10 dB signal-to-noise ratio （SNR） gains at 0.1 block error rate （BLER） target can be achieved compared with existing NOMA schemes and orthogonal multiple access （OMA）, respectively. Besides, 0.01 BLER target can be achieved while an error floor exists in existing NOMA schemes. Under random sequence selection, collision probability is reduced by multi-level powers. In addition, GWBE sequences achieve lower BLER than existing sequences and the gain is large especially for low BLER requirements. This shows that the proposed scheme can support larger connectivity and higher reliability.上行非正交多址(NOMA)是一项满足第五代(5G)及未来系统需求的有前景的技术。学术界和工业界提出了各种各样的NOMA方案,然而大部分方案均假设相等平均接收功率,该假设会限制性能。为满足5G系统海量连接与高可靠性需求,本文将不等接收功率看作多址签名的一部分,为上行NOMA系统提出3项增强方案。首先,提出将不等平均接收功率时满足generalized Welch界等式(GWBE)的最优序列,用于上行NOMA。其次,为了在接收端获得更好的串行干扰删除(SIC)性能,提出基于多级平均接收功率的用户分组。最后,为减少组内和组间干扰,提出基于序列互相关性能的序列分组。仿真结果表明,在400%超载因子、固定签名分配的上行NOMA系统中,在0.1块差错率(BLER)时,与现有NOMA方案和正交多址(OMA)相比,结合多级平均接收功率和序列分组的现有NOMA方案可以分别获得3 dB和10 dB的信噪比(SNR)增益;在0.01块差错率时,现有NOMA方案存在错误平台,无法达到该需求,而增强方案可以达到。在随机选择多址签名条件下,多级功率会减小碰撞概率进而提升性能。此外,GWBE序列可以达到比现有序列更低的BLER,且SNR增益在低BLER需求时更加明显。以上结果表明提出的增强方案可以支持更大连接数,达到更高可靠性。

关 键 词：Uplink non-orthogonal multiple access Generalized Welch-bound equality Multi-level received powers Sequence grouping 

分 类 号：TN929.5[电子电信—通信与信息系统]