基于智能反射表面大规模MIMO-NOMA系统频谱效率分析

为了进一步提高频谱效率,在大规模多输入多输出(MIMO)系统中引入了非正交多址(NOMA),然而当基站与用户之间的信道较差时,这很难保证用户的频谱效率。为解决这一问题,探讨了基于智能反射表面(IRS)的大规模MIMO-NOMA系统,来保证用户的频谱效率。具体地,首先考虑了IRS辅助的大规模MIMO-NOMA系统模型。然后根据簇头选择算法,为每个波束选择一个簇头来设计模拟预编码。之后,根据等效信道的相关性对用户进行分组,选择在每个波束中等效信道增益最强的用户来设计数字预编码。最后联合优化基站的功率分配和IRS的相移矩阵,来保证用户频谱效率的公平性,即最大化最小频谱效率。仿真结果表明,与没采用IRS的大规模MIMO-NOMA系统相比,IRS辅助的大规模MIMO-NOMA系统可显著改善最弱用户的频谱效率。     

面向用户随机分布的NOMA-卫星通信网络性能分析

针对基于正交多址接入(Orthogonal Multiple Access,OMA)技术的卫星通信网络资源利用率低的问题,提出了一种基于功率域非正交多址接入(Non-orthogonal Multiple Access,NOMA)技术的上行链路卫星通信方案。该方案在用户随机分布的前提下,利用最大或受限的发送功率同时同频发送信息给卫星节点,并采用串行干扰消除(Successive Interference Cancellation,SIC)方法提取各用户信息。通过构建用户随机位置信息与波束增益关系,分析了用户分布对系统性能的影响。通过仿真验证了基于NOMA技术的卫星上行通信网络在系统遍历容量方面具有的优势,并分析了关键参数对系统性能的影响。     

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...     

一种基于SIC的NOMA下行链路信号检测方法

面对频谱效率和系统容量等方面出现的新需求,传统的多址方式已经不能满足需要,业内提出一种新的多址方式NOMA。NOMA具有频谱利用率高、系统容量大等优点,但是其传统的下行链路串行干扰消除检测技术中的检测算法是基于硬判决的,检测性能差。介绍了NOMA链路实现的基本原理,并提出一种改进的串行干扰消除检测方法,即直接计算比特的软信息来完成软判决,恢复干扰信号后再做消除。最后通过仿真分析验证,该算法可以提高串行干扰消除检测的检测性能。     

基于时延线阵列的毫米波NOMA系统混合预编码设计和功率分配

针对传统毫米波非正交多址接入（NOMA）系统中高精度移相器复杂度高、功耗大的问题,将可进行连续相位调制的低复杂度、低功耗的时延线阵列引入毫米波NOMA系统,研究了该系统能效和谱效。首先,提出一种改进K-means算法对用户进行分组,每组用户采用NOMA技术传输信息;然后,设计了一种基于开关控制时延线阵列的低复杂度混合模拟数字预编码;最后,构建了一个在用户服务质量和系统总功率约束下优化发送功率的能效最大化问题,并提出一种基于Dinkelbach算法和交替优化的两层迭代算法。仿真结果表明,与传统基于移相器的结构相比,所提方案的系统能效和谱效分别提高了32.3%和10.7%。     

多波束赋形在非正交多址接入技术中的应用研究

为解决非正交多址接入(NOMA)技术在毫米波Massive MIMO系统中用户的分组受限于基站波束宽度的问题,提出了一种能够产生指向多个方向的波束的波束赋形方案.基于该多波束波束赋形方案,建立了多小区多用户场景下的用户资源分配的数学模型.为降低计算的复杂性,采用两阶段的资源分配算法.在第一阶段中,在给定的功率分配条件下将模型转化为联盟博弈中联盟的生成问题,并提出一种通过迭代确定用户分组和天线单元分配的算法;在第二阶段中,通过将非凸的数学优化问题转化为DC规划问题,提出用户功率分配的算法.仿真结果表明,本文所提多波束波束赋形方案能够有效产生指向多个方向的波束,且所提资源分配算法能够有效提高系统的性能.     

联合时域−波束域非正交多址接入

为了提高系统容纳连接设备的能力,提出了一种适用于毫米波大规模多输入多输出系统的联合时域?波束域非正交多址接入方案。该方案利用用户空间信道的相关性和差异性实现波束域接入,利用稀疏扩频技术实现时域接入,并以提高系统的通信可靠性为优化目标,构造并求解了联合域稀疏接入矩阵设计的优化问题。最后,基于联合域信道质量对接入矩阵进行重构,并在消息传递算法中加入干扰消除操作,降低译码复杂度的同时提高了通信可靠性。     

毫米波分离型子阵列的低复杂度混合波束成型传输设计

为了增强毫米波传输的系统性能及扩大其覆盖范围,数模混合（大规模）多输入多输出（MIMO）传输技术得到了广泛关注。本文针对分离型子阵列混合波束成型架构的毫米波通信系统,研究了基于码本的低复杂度优化子阵列波束控制矢量算法。采用交替优化方法及干扰对齐思想,本文提出了一种双向交替优化设计各收发子阵列的波束控制矢量算法。所提出的算法具有收敛速度快,计算复杂度低的特点。数值仿真结果表明,基于该算法设计的分离型子阵列混合波束成型传输方案的有效性及复杂度低的优越性。      

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...     

毫米波大规模MIMO-NOMA系统功率分配和混合预编码设计

针对基于非正交多址接入(Non-Orthogonal Multiple Access, NOMA)的毫米波大规模多输入多输出(Multiple Input Multiple Output, MIMO)系统中边缘用户可达速率较低的问题，提出了一种联合功率分配和混合预编码的优化方案来保证边缘用户在内的所有用户都具有较好的速率性能。基于最大最小公平性准则，设定了一个含有复杂目标函数和高维非凸约束的优化问题。采用固定变量法将该非凸问题转换为功率分配和混合预编码2个子优化问题处理。对于功率分配的设计，通过卡罗需-库恩-塔克(Karush-Kuhn-Tucker, KKT)条件得到了封闭形式下的最优功率分配系数；对于混合预编码的设计，提出了基于迫零(Zero Forcing, ZF)和压缩边界粒子群优化(Boundary Compressed-Particle Swarm Optimization, BC-PSO)算法相结合的求解方法，得到混合预编码的次优解。提出了一种交替优化算法来交替优化功率分配和混合预编码，直到满足设定的精度要求。仿真结果表明，该方案的最大最小速率优于传统的NOMA方案。     

Space‐time block coding in millimeter wave large‐scale MIMO‐NOMA transmission scheme

In this paper, we introduce a new wireless system architecture using space‐time block coding schemes (STBC) and non‐orthogonal multiple access (NOMA) in millimeter wave (mmWave) large‐scale MIMO systems. The proposed STBC mmWave large‐scale MIMO‐NOMA system utilizes two MIMO subarrays, transmitting data over two channel vectors to mobile users. To reduce the communication overhead and latency in the system, we utilize random beamforming with optimal coefficients at the base station and random‐near random‐far user pairing in implementing the NOMA scheme. Our results show that the proposed STBC mmWave large‐scale MIMO‐NOMA technique significantly outperforms the previous counterparts.     

QoS-based optimal and fair resource allocation for energy-efficiency uplink NOMA networks

The energy-efficiency(EE) optimization problem was studied for resource allocation in an uplink single-cell network, in which multiple mobile users with different quality of service (QoS) requirements operate under a non-orthogonal multiple access (NOMA) scheme. Firstly, a multi-user feasible power allocation region is derived as a multidimensional body that provides an efficient scheme to determine the feasibility of original channel and power assignment problem. Then, the size of feasible power allocation region was first introduced as utility function of the subchannel-user matching game in order to get high EE of the system and fairness among the users. Moreover, the power allocation optimization to the EE maximization is proved to be a monotonous decline function. The simulation results show that compared with the conventional schemes, the network connectivity of the proposed scheme is significantly enhanced and besides, for low rate massive connectivity networks, the proposed scheme obtains performance gains in the EE of the system.     

Beam Tracking Particle Filter for Hybrid Beamforming and Precoding Systems

Because millimeter wave (mmWave) systems can span notably wide spectral bands, mmWave systems are expected to dominate fifth-generation (5G) communication systems. Due to the short wave-length of mmWave radiation, multiple-input multiple-output (MIMO) systems can use massive antennas and precoding technology to overcome signal attenuation in mmWave channels. However, the cost and power consumption of radio frequency (RF) chains would increase substantially with the number of antennas. Hence, hybrid beamforming was proposed to reduce the number of RF chains in massive MIMO systems. Hybrid beamforming involves RF beamforming matrix construction and baseband precoding matrix derivation. This study focused on the design and implementation of an algorithm for the RF beamforming matrix construction for mobile environments. Accordingly, this study presents a mixture particle filter that exploits the temporal continuity of beam clusters in a mobile mmWave channel to reduce the computational complexity of RF beamforming matrix construction. Moreover, this beam-tracking particle filter is based on parallel processing architecture to support the tracking of multiple beam clusters in the mmWave channel. Finally, the beam-tracking particle filter was implemented on a field-programmable gate array platform and was verified in a hybrid beamforming system for mmWave MIMO systems. The particle filter processor achieved a maximal throughput of 9.198k matrices/s with a clock rate of 192 MHz, which could support a speed of up to 88.5 km/h for mobile users.

     

一种基于SIC-CDM的低复杂度混合波束赋形方案

为了平衡毫米波大规模多输入多输出系统的性能和硬件开销,降低系统功耗,以频谱效率为优化目标,在部分连接结构下提出了一种收发端联合设计的低复杂度混合波束赋形方案。首先,基于连续干扰消除将原始优化问题转化为多个子阵的速率优化问题;然后,利用坐标下降法完成模拟波束赋形矩阵设计;最后,引入等效信道矩阵大幅降低矩阵维度,再对其进行奇异值分解获得数字波束赋形矩阵。仿真结果表明,与其他算法相比,所提算法在系统功耗降低的同时保持了较优的性能,且性能逼近部分连接结构的最优方案。     

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。      

An energy-efficient power allocation scheme for millimeter-wave MIMO-NOMA systems

There are many challenges in fifth generation (5G) telecommunication systems, due to the increasing demands and applications. The most important of which are need to have higher energy efficiency (EE) and spectral efficiency (SE). They are critical in the practical multiple-input multiple-output (MIMO) telecommunication systems. Non-orthogonal multiple access (NOMA) methods and millimeter-waves can be used in conjunction with MIMO systems to improve their EE and SE performance. In this paper, we investigate the application of NOMA and mm-Wave transmission in the downlink of MIMO systems. Then, we formulate the optimization problem for users in MIMO-NOMA systems to maximize the EE that is subject to minimum data rate to satisfy required quality of service (QoS) and maximum transmission power. To achieve the optimal power allocation for users, we reach a problem for the EE maximization that is non-convex and solution of the optimization problem is not trivial. We exploit a lower bound of the data rate and the Lagrange dual function to convert it to a convex and unconstrained problem, which is easy to solve. In the next step, we derive a relation for determining the optimal power allocation of users. In addition, a numerical algorithm is presented that can be used to solve the problem. According to the simulation results of the proposed algorithm, our method performs better and provides higher EE than both orthogonal multiple access and equal power allocation schemes.     

Exploiting capture and interference cancellation for uplink random multiple access in 5G millimeter-wave networks

The forthcoming 5G technology aims to provide massive device connectivity and ultra-high capacity with reduced latency and costs. These features will be enabled by increasing the density of the base stations, using millimeter-wave (mmWave) bands, massive multiple-input multiple-output systems, and non-orthogonal multiple access techniques. The ability to support a large number of terminals in a small area is in fact a great challenge to guarantee massive access. In this context, this paper proposes a new receiver model for the uplink of 5G mmWave cellular networks. The receiver, called Iterative Decoding and Interference Cancellation (IDIC), is based on the Slotted Aloha (SA) protocol and exploits the capture effect alongside the successive IC process to resolve packet collisions. A 5G propagation scenario, modeled according to recent mmWave channel measurements, is used to compare IDIC with the widely adopted Contention Resolution Diversity SA (CRDSA) scheme to show the performance gain of IDIC, when elements of practical relevance, like imperfect cancellation and receive power diversity, are considered. The impact of packet and power diversity is also investigated to derive the preferable uplink random access strategy that maximizes the system throughput according to the offered channel load.

     

Resource optimization of secure energy efficiency based on mmWave massive MIMO-NOMA system with SWIPT

The secure energy efficiency (SEE) problem was investigated for the millimeter wave (mmWave) multiple input multiple output (MIMO) non-orthogonal multiplex access (NOMA) systems with simultaneous wireless information and power transfer (SWIPT) in the presence of multiple legitimate receiver (LR) and an eavesdropper.LR was first grouped according to the channel state information and the cluster heads of each group were selected,then the LR of each cluster was served by each beam with NOMA and hybrid precoding technology.Based on this,a SEE maximization problem was formulated by optimizing power allocation and power splitting factors.The Dinkelbach algorithm and first order Taylor approximation were proposed to transform the original non-convex problem into a convex one,and an iterative algorithm was developed to solve it.Finally,numerical results show that the proposed scheme can effectively improve the SEE.     

Maximum throughput design for IRS aided WPCN system based on NOMA

This paper considers a wireless powered communication network(WPC network, WPCN) based on non-orthogonal multiple access(NOMA) technology aided by intelligent reflective surfaces(IRS). WPCN mainly focuses on downlink energy transfer(ET) and uplink information transmission(IT). At the ET phase, a dedicated multi-antenna power station(PS) is equipped to supply power to users with the assistance of IRS, and at the IT phase, the IRS adjusts the phase to assist the user in applying NOMA technology to...