非理想干扰消除全双工协作NOMA系统性能分析及功率分配

随着非正交多址接入（Non-Orthogonal Multiple Access, NOMA）技术的不断发展,协作NOMA (Cooperative Non-Orthogonal Multiple Access, CNOMA)也受到广泛关注.该文研究了由一个基站（Base Station, BS）、一个远端用户和一个近端用户组成的全双工（Full-Duplex, FD）协作NOMA (FD-CNOMA)系统,其中近端用户作为一个FD解码转发中继以传输远端用户的信号.考虑实际情况中存在基站与远端用户有无直接链路两种情况,以及非理想连续干扰消除（Successive Interference Cancellation, SIC）对系统带来的残留干扰问题,该文提出并解决了在该模型下用户的功率分配问题.最后,该文基于此模型给出了中继用户和远端用户的中断概率闭式表达式和遍历速率的近似闭式表达式.理论分析与仿真结果表明,即便存在非理想SIC和自干扰,相对于半双工（Half-Duplex, HD）协作NOMA(HDCNOMA)和NOMA系统而言,FD-CNOMA系统表现出更好的系统性能.同时,非理想...     

非理想SIC下全双工NOMA系统的安全性能分析

针对存在多个非共谋窃听者,研究了一种基于全双工中继和两阶段中继选择（TSRS）的非正交多址接入（NOMA）物理层安全通信方案。每个通信过程包含一个传输时隙,系统在每个时隙开始由TSRS策略选择最优中继,所选中继在从源节点接收NOMA叠加信号的同时,向两个目的节点转发上一时隙的再编码叠加信号,两个目的节点采用串行干扰消除（SIC）技术从中继叠加信号中解码获取各自的期望信号。推导了非理想SIC下系统安全中断概率的近似表达式,进行了蒙特卡洛（Monte-Carlo）仿真验证,同时分析了各仿真参数（SIC残余干扰系数、目标安全速率、中继规模等）与系统安全中断概率的关系。理论分析与模拟仿真的结果表明,全双工技术与TSRS的结合方案能有效提升系统的安全中断性能。将该方案应用于实际通信系统设计时,选择合适传输信噪比（SNR）、提高串行干扰消除能力或适当增加中继数量均可实现更好的保密性能。     

非完美条件下的非正交多址接入星地融合网络性能分析

随着星地融合网络(ISTNs)的快速发展,大量的传感器和无线设备都有无线服务的接入需求,从而对星地融合网络的频谱效率和服务质量提出了新的挑战。不同于传统的正交多址接入技术,非正交多址接入(NOMA)技术可在相同的频率下传输不同用户的信号,其被认作为提高星地融合网络频谱效率的有效方法,从而被广泛研究。目前,针对NOMA和星地融合网络的研究大多都是在理想条件下进行的,由此该文研究更加实际的情况,即在非完美串行干扰消除(SIC)、信道估计误差和同频干扰下,对星地融合网络的性能进行研究。该文在假设卫星端和地面端均采用多天线的前提下,推导了系统遍历容量的闭式表达式,验证了非完美条件对于系统性能的影响。同时蒙特卡罗仿真验证了理论分析和推导的正确性。     

自适应窃听下NOMA用户协作干扰的物理层安全研究

在存在一个半双工自适应窃听者的通信模型中,分析了采用非正交多址(Non-orthogonal Multiple Access,NOMA)技术合作系统的性能。提出了一种新型的合作NOMA方案,该方案在中继转发时,强用户可充当中继协助转发弱用户信号,而弱用户采用全双工技术向窃听者发送干扰信号,提高了通信链路的安全性和用户的服务质量。合法接收端采用连续干扰消除(SIC)技术,以解码来自叠加信号的各个消息。在已知窃听信道统计信道状态信息(CSI)的情况下,分别推导了2个用户的安全中断概率和中断概率的闭合表达式,并通过Monte-Carlo仿真验证。理论分析和数值模拟结果均表明所提出的NOMA用户合作方案在保密率方面优于非合作方案的性能。     

针对动态用户的上行非正交多址接入技术

为了增强非正交多址接入技术(NOMA, non-orthogonal multiple access)应用场景的广泛性，本文给出了一个针对动态用户的上行NOMA系统。在传统的NOMA系统中，基站将用户到基站间的具体距离反馈给用户。由于在本文的场景中用户是动态分布的，基站实时地反馈具体距离势必会使系统开销过大。为了减少系统开销，本文假定基站只向用户反馈距离的统计特性，用户在之后的信息传输中根据距离的统计特性确定发射功率。理论分析了动态用户的中断性能并推导出了中断概率的表达式。仿真验证了理论推导的正确性，表明了当用户的分布区域内外边界值相差不大时，利用距离的统计特性和利用具体距离确定发射功率可以获得几乎相同的中断性能。      

基于非正交多址的室内可见光通信系统性能优化方法

室内可见光通信(Visible Light Communication, VLC)系统常用的非对称限幅光OFDM(Asymmetrically Clipped Optical Orthogonal Frequency Division Multiplexing, ACO-OFDM)与直流偏置光OFDM(DC-biased Optical OFDM, DCO-OFDM)采用加循环前缀、信道均衡和载波复用等方法解决信道干扰及多用户复用问题,但均以牺牲有效性为代价。非正交多址(Non-orthogonal Multiple Access, NOMA)通过功率域复用提高频谱利用率,利用串行干扰消除(Successive Interference Cancelling, SIC)进行多用户信号处理,有效兼顾可靠性与有效性。将NOMA应用于室内可见光系统,建立基于NOMA-DCO-OFDM的可见光信号传输及信道增益模型。通过功率域多用户信道差异计算信道增益,进行功率分配实现功率域复用,提高系统容量和通信速率;利用SIC按功率分配算法对用户逐一解调,减弱信道干扰,提高可靠性。通过理论分析和仿真实验验证表明:该系统的通信速率达到6.8×107 bit·s?1,且合速率受用户数量的影响不显著。2用户下,误码率(Bit Error Rate, BER)为10?4时用户1有5.2 dB左右的性能提升,用户2有2.3 dB左右的性能提升,通信可靠性也明显提高。     

NOMA系统中基于协作干扰的物理层安全方案

针对NOMA系统中的信息安全传输问题,提出基于协作干扰的物理层安全方案,该方案利用外部协作节点发送干扰信号恶化窃听者的接收性能。本文首先利用泊松点过程对协作节点和窃听者的位置进行安全建模,然后推导了随机协作干扰方案下系统保密中断概率的闭式解,但随机协作干扰方案会同时恶化合法用户的接收信号,性能有限,因此提出一种信道增益受限的协作干扰方案,该方案选择到近端用户和远端用户的瑞利信道因子均小于一定阈值的协作节点发送干扰信号,会对窃听者造成更严重的影响。仿真结果表明,在NOMA系统中采用受限的协作干扰方案能够有效提升系统安全性能。      

全双工认知NOMA网络下中继选择策略性能分析

本文把非正交多址接入(NOMA)技术与认知网络相结合,提出了一种基于多中继选择的认知NOMA网络模型。考虑了在瑞利衰落信道下,主网络借助次级网络中的全双工中继实现可靠通信,作为回报,次级网络允许接入授权频谱来传输次级信号。中继同时接收主次信号后,采用串行干扰消除技术(SIC)依次解码主次信号,并根据NOMA协议转发信号到主次用户端。推导了在两种中继选择策略下认知NOMA网络中断概率,并通过了蒙特卡罗仿真验证。仿真结果表明,两阶段中继选择策略和全双工技术能有效提高系统中断性能。      

基于NOMA场景的多用户调度物理层安全性能分析

针对NOMA系统传输模型,提出了基于NOMA通信场景下的多用户调度策略,对非窃听中继和窃听中继2种场景分别进行研究分析,推导计算出2种场景下OMA与NOMA系统安全中断概率数学闭合表达式,并进行对比分析。分析和仿真结果表明通过增加主信道信噪比(SNR)和发送用户数目可以有效提高系统安全性能,分析表明同等情况下基于NOMA系统的安全中断概率总是低于OMA系统,并且这种优势随着主信道SNR的增加、窃听信道SNR的减小而更加显著。     

不完美SIC下NOMA系统用户配对和功率分配联合优化

当前非正交多址(Non-Orthogonal Multiple Access,NOMA)系统的用户配对和功率分配通常作为独立的问题进行研究,未考虑接收端不能完美执行串行干扰消除(Successive Interference Cancellation,SIC)的限制.鉴于此,提出一种不完美SIC下NOMA系统用户配对和...     

The coverage-capacity tradeoff in multiservice WCDMA cellular systems with serial interference cancellation

The uplink coverage and capacity of CDMA cellular systems with the conventional single user detector receiver are interference limited. Particularly, during the roll-out phase, the coverage of a CDMA system is uplink limited. Hence, using serial interference cancellation (SIC) at the base station is a low cost option to improve the overall performance. Considering the typical quality of service requirements of mixed services, i.e. voice and data, a new hybrid receiver structure for interference cancellation is proposed. In order to perform system level analysis, the calculation of signal-to-interference ratios is extended to the case of multiple service classes with various SIC receiver structures. Given this tooling, the optimum powers of the mobile stations are derived as a function of various system and design parameters. This enables an accurate calculation of the intracell and intercell interference. Based on this, analytical expressions are derived for the coverage-capacity tradeoff. Results show significant performance gains in terms of user capacity and cell coverage by using SIC receivers including the proposed hybrid structure that meets the delay and complexity requirements of the different service classes.     

基于短包通信的NOMA下行链路安全传输

面向物联网业务中的低时延需求,将短包通信(SPC)和非正交多址接入(NOMA)技术相结合,针对存在窃听者的情况研究多用户NOMA系统中的安全传输问题.以最大化弱用户的安全吞吐量为目标,考虑用户译码错误概率约束、总功率约束和功率分配约束,提出了一种低复杂度的功率分配方案实现系统安全传输.为解决复杂的目标函数和不可靠的串行...     

On Multiple Access Using H-ARQ with SIC Techniques for Wireless Ad Hoc Networks

In this paper, we consider non-orthogonal multiple access (NOMA) for wireless ad hoc networks over block fading channels where the performance is limited by interference and fading. In order to provide a reasonable performance, we can use re-transmission and interference cancellation techniques. Re-transmission techniques can provide a diversity gain over fading channels, while the successive interference cancellation (SIC) can improve the signal to interference ratio (SIR). Using the information outage probability, we show that the NOMA approach with re-transmissions can perform better than the orthogonal multiple access (OMA) approach with re-transmissions when the signal to noise ratio (SNR) is low. It is also shown that the outage probability of the NOMA with SIC is lower than that of OMA when the rate is sufficiently low where SIC can be facilitated.     

Equal BER performance in linear successive interferencecancellation for CDMA systems

In this contribution, we calculate the received power distribution required to obtain equal bit-error rate (BER) performance for all links in a code-division multiple-access system employing a linear successive interference cancellation (SIC) receiver at the base station for an additive white Gaussian noise channel. We show that the variance of the decision statistic of the linear SIC receiver can be formulated in a nonrecursive manner that allows calculation of the power profile necessary to obtain equal signal-to-noise-plus-interference ratios for all received signals when cancellation order is determined based on average power. When equal BER performance is required, this formulation allows capacity limits to be determined for a required signal-to-interference-plus-noise ratio (SINR) or an SINR limitation to be calculated for a given capacity. We also show that the power profiles required are significantly larger than those obtained when perfect cancellation is assumed, highlighting the inadequacy of such an assumption     

基于双向中继和网络编码的NOMA网络性能分析

针对实际场景中存在的具有上下行双向传输任务的通信系统,本文提出了一种双向中继协作非正交多址接入(NOMA, non-orthogonal multiple access)传输方案,基于解码转发(DF, Decode and Forward)协议研究信号的上行和下行双向传输技术,与现有NOMA方案不同,本方案为近端用户分配较大的功率,利用网络编码(NC, network coding)原理在两个时隙内实现基站和用户之间的双向信息交换。进一步考虑不完美信道状态信息(CSI, Channel State Information)条件,分析系统的传输性能并推导了系统中断概率以及遍历和速率闭合表达式。仿真结果表明,在完美CSI和不完美CSI条件下,相比于现有文献所提方案、单向中继(OWR,One-Way Relay)和正交多址(OMA, Orthogonal Multiple Access)网络,本文所提方案有效降低了系统的传输中断概率,提高了系统的遍历和速率以及系统吞吐量。      

Outage of cooperative NOMA with an energy harvesting relay in an underlay cognitive radio network

This paper analyzes the performance of a cooperative nonorthogonal multiple access (NOMA) in an underlay cognitive radio network aided by an energy harvesting relay. A secondary source transmits signal for two users, where a near user acts as a relay for the far user. The far user applies the selection combining (SC) approach on the signals which were relayed by the near user and received via direct path from the secondary source. We analytically derive the outage probability (OP) of each user separately, the overall system OP, and the throughput of the system. The impact of the power allocation coefficient of NOMA and energy harvesting parameters on outage is indicated. Further, the performance of the network is investigated with imperfection in successive interference cancellation (SIC), maximal ratio combining (MRC) at relay, and Nakagami-m fading. The results derived analytically are supported by simulation in MATLAB.     

NOMA Transceiver Design for Highway Transportation in Mobile Hotspot Networks

The mobile hotspot network (MHN), which is capable of providing a data rate of gigabits per second at high speed, is considered a potential use case of the future enhanced mobile broadband for 5G. Because a unidirectional network deployment has been considered for an MHN, non‐orthogonal multiple access (NOMA) can be employed to improve the system performance. For a practical implementation of NOMA under an MHN highway scenario where multiple pieces of MHN terminal equipment are served through the same beam simultaneously, a NOMA transceiver is proposed in this paper. For the NOMA transmitter, Gray‐coded QAM constellation mapping is extended to arbitrary modulation order q. For the NOMA receiver, successive interference cancellation (SIC) is no longer necessary, and instead, a parallel demodulation is proposed. The numerical and simulation results suggest that the proposed NOMA transceiver outperforms the conventional NOMA SIC receiver and can be flexibly used for an MHN highway scenario.     

基于GSIC的上行链路毫米波大规模MIMO-NOMA系统低功耗传输方法

非正交多址接入（non-orthogonal multiple access,NOMA）和毫米波大规模多输入多输出（multiple-input multiple-output,MIMO）的结合能够支持未来无线通信网络的巨流量大连接需求。研究了上行链路毫米波大规模MIMO-NOMA系统中的功率最小化问题，提出了基于群体串行干扰消除（group-levelsuccessiveinterference cancellation,GSIC）的混合波束成形毫米波MIMO-NOMA上行传输系统新架构。具体来说，根据信道增益对用户进行群体划分，不同群体用户由NOMA服务，群体内用户采用空分多址区分。通过给不同群体设计模拟波束成形矩阵，对数字波束成形和功率控制进行联合优化，提出了一种并行迭代算法来解决优化问题。仿真结果表明，所提出的新架构在总功率方面优于传统的基于分簇和用户级串行干扰消除的毫米波大规模MIMO-NOMA。