多用户多速率OFDM中的子载波分配和功率控制

该文基于对多用户多速率正交频分复用(OFDM)系统性能的分析,提出了子载波分配和功率控制方案。在采用P-QAM调制的下行链路中,如已知所有子信道的信息状态(CSI),在满足每一个用户的服务质量的前提下,先给固定速率的用户分配最优子信道,再给变速率的用户按照子信道链路增益最大化分配剩余的子信道;每一个用户分配的子信道数目,由链路增益的取值区间决定。信号发射功率则按照注水法则分配:链路增益大的子信道分配的功率大,链路增益小的子信道分配的功率小,则系统的总传输速率可达最大。仿真结果证明了该文提出的分配方案优于Jang的分配方案。     

基于NGA的可见光通信接收系统分析

在室内可见光通信MIMO(多输入多输出)系统中,针对用户无法公平享用通信服务的问题,提出了一种寻找光接收机中最优聚光器增益来优化多用户情况下功率分配不均匀的方法。利用改进的NGA(小生境遗传算法)建立与接收光功率相对应的节点模型,通过运算寻找一组最优的聚光器增益组合运用到光接收系统中。仿真结果表明,改进的NGA能高效地找出一组最优聚光器增益组合,从而改善用户接收光功率分配不均匀的现象。     

OFDM系统中动态子信道和功率的分配

在分析一种多用户OFDM系统中自适应子信道和比特功率分配算法的基础上,根据多径频率选择性衰落信道的瞬时特性,动态地为多用户分配子信道和传输比特数,并服从MA优化准则.并且进一步考虑了系统中有固定速率用户和可变速率用户同时存在的情况:在子信道分配时,先给固定速率的用户分配子信道,再给可变速率用户按照子信道链路增益最大化分配剩余的子信道;在信号发射功率分配上,按照"注水"法则分配,链路增益大的子信道分配的功率大,链路增益小的子信道分配的功率小,则系统的目标函数,总传输速率可以达到最大.仿真证明了此方案优于一般的方案.     

室内LED可见光语音通信网络的信道分配算法研究

采用SIC算法对室内LED可见光语音通信网络的信道分配进行研究。通过对室内可见光通信系统、白光音频调频信号传输系统原理的分析,设计了语音通信收发机电路。电路信号接收效果较好,利用SIC检测算法进行通信网络信道功率分配,与采用线性工作范围为2.25~5 V,工作电流范围为0.1~1 A的商用照明LED进行性能仿真试验,结果表明,与传统的FCA算法相比,SIC算法的阻塞率要高于FCA算法,且算法引入了更小的系统干扰量,在服务区内使用户通信质量得到保证。     

色/频/空三维资源复用的室内可见光非直流偏置OFDM系统性能研究

提出一种新的室内可见光非直流偏置正交频分（Non-DC-Biased Orthogonal Frequency Division Multiplexing, NDC-OFDM）复用系统,该系统采用多个颜色LEDs作为光源,在保证高传输可靠性的同时可以维持环境光的稳定。将空间调制和同色异谱调制结合并应用到室内可见光OFDM通信系统中得到一种新的适用于室内可见光通信系统的NDC-OFDM传输方案,该方案具有OFDM、空间调制和同色异谱调制的优势,适用于高速室内白光通信系统。仿真结果表明所提出的NDC-OFDM室内可见光传输系统与传统的直流偏置光OFDM （DC-biased Optical OFDM）和非对称限幅光OFDM （Asymmetrically Clipped Optical OFDM）相比具有更好的优势,并且与其它NDC-OFDM室内可见光传输方案相比,对于OFDM信号高峰均功率比引起的光信号非线性畸变问题,本文提出的多色LEDs NDC-OFDM室内可见光传输方案除了具有更好的鲁棒性外,还不会产生光强度波动。     

NOMA系统中利用共轭梯度法的功率分配方案

通过功率分配,5G通信的关键技术——非正交多址（NOMA）实现发射功率域的多用户复用,有效提高了频谱效率。不同的功率分配方案直接影响系统的吞吐量,针对NOMA下行链路现有功率分配算法存在的局部最优问题,提出了一种利用共轭梯度法的最优功率分配方案,采用共轭梯度法求解用户的加权和速率最大化的优化问题。现有理论证明,该方法可以收敛到全局最优解。仿真结果表明,该方法性能优于已有的固定功率分配（FPA）算法和分数阶发射功率分配（FTPA）算法,且此非正交多址（NOMA）系统性能明显优于正交多址（OMA）系统。      

一种基于OFDM的多用户认知无线电系统联合资源分配算法

针对频谱共享环境,研究了采用OFDM调制方式的多用户认知无线电系统中,综合考虑自身发射功率约束与主用户干扰功率约束的资源分配问题.基于最大化认知用户和速率的优化目标,给出了连续比特条件下最优的多水位注水功率分配表达式;针对更实际的整数比特要求情况,通过基于相对增益因子RG的子信道选择机制与每个认知用户内多约束的贪婪比特与功率分配策略,来最大限度地提高频谱利用率.仿真结果表明:联合的子信道、功率与比特分配算法在不同的参数设置下均达到了良好的性能,在不影响主用户通信的前提下有效地提高了认知系统的频谱利用率.     

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...     

基于小波变换的可见光OFDM通信系统性能优化

在可见光通信中, 由于信道的多径效应和信道衰减在传统正交频分复用(OFDM)系统会产生符号间干扰, 从而降低系统的可靠性。为了保障通信质量, 采用带有循环前缀的OFDM系统来抵抗多径效应引起的符号干扰; 为了降低系统的误比特率和峰均比, 采用Haar小波来实现系统有效性、可靠性、峰均比等参量的性能优化, 并采用蒙特卡洛法进行了仿真验证。结果表明, 当系统的误比特率为10-4时, 离散小波变换OFDM系统较快速傅里叶变换OFDM(FFT-OFDM)系统的误码性能大约提高了5dB, 通信效率提高了大约11%;当系统的峰均比为5dB时, FFT-OFDM系统的互补累计分布函数(CCDF)值接近10-2, DWT-OFDM系统的CCDF值为0。该研究为可见光小波变换OFDM通信提供了参考。     

反向散射中基于载波索引的混合NOMA方案

基于功率域非正交多址的环境反向散射通信系统上行链路常通过距离差完成用户配对。无源反向散射系统的双重信道衰落,导致远端边缘设备无法满足通信所需功率或解码所需信干噪比(Signal-to-Interference-Noise Ratio, SINR)约束。为了解决上述问题,提出一种OFDM和具有索引调制(Index Modulation, IM)的OFDM混合的上行NOMA方案,该方案由标签调制方案和反射系数调节方案组成。OFDM-IM提供了更好的能量效率,可以使功率水平低的设备满足通信条件。反向散射设备(Backscatter Devices, BD)根据接收到的功率水平,灵活地选择OFDM或者OFDM-IM,并在功率域叠加;通过调节反射系数保证叠加信号的功率差,接收机利用功率电平来执行多用户检测。实验结果表明,该方能够有效地提高远端用户解码的成功率,并且解码用户数量的增加提高了系统容量。     

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...     

Power domain cyclic spread multiple access: An interference‐resistant mixed NOMA strategy

The next generation wireless access technology highly relies on nonorthogonal multiple access (NOMA) technique. This paper proposes a novel power domain cyclic spread multiple access (PDCSMA) scheme for the design of NOMA system with power domain superposition coding (SC) and cyclic spreading at the transmitter concurrent with symbol level successive interference cancellation (SL‐SIC) at the receiver. Based on acceptable difference in channel gain, the users are grouped together to form PDCSMA clusters, and the unique power is allotted to each user in a cluster. The user with good channel condition is allotted less power, and the user with poor channel condition is allotted more power. Each PDCSMA cluster has its own spreading code, and the data of every user in a cluster are cyclic spread with the same code. Each cluster supports the number of multipath components equivalent to the length of the spreading code. The use of cyclic spreading makes the signal suffered by multipath fading less prone to intra cluster interference. The user signal is decoded by minimum mean square error‐frequency domain equalization (MMSE‐FDE) or maximal ratio combining (MRC)–based receiver in which weak user is detected with hard decision, and strong user is detected with SIC. Compared with conventional power domain NOMA (PDNOMA) and interleaved NOMA, the proposed PDCSMA achieves better bit error rate (BER) performance and assures guaranteed detection.     

New Optimal and Suboptimal Resource Allocation Techniques for Downlink Non-orthogonal Multiple Access

This paper investigates several new strategies for the allocation of radio resources (bandwidth and transmission power) using a non-orthogonal multiple access (NOMA) scheme with successive interference cancellation (SIC) in a cellular downlink system. In non-orthogonal access with SIC, the same subband is allocated to multiple users, which requires elaborate multiuser scheduling and subband assignment techniques, compared to orthogonal multiplexing. While taking into account various design issues, we propose and compare several optimum and suboptimum power allocation schemes. These are jointly implemented with multiple user scheduling strategies. Besides, a minimization of the total amount of used bandwidth is targeted. Also, to increase the total achieved system throughput, a hybrid orthogonal-non orthogonal scheme is introduced. This hybrid scheme enables a dynamic switching to orthogonal signaling whenever the non-orthogonal cohabitation in the power domain does not improve the achieved data rate per subband. Extensive simulation results show that the proposed strategies for resource allocation can improve both the spectral efficiency and the cell-edge user throughput, especially when compared to previous schemes employing either orthogonal signaling or NOMA with static inter-subband power allocation. They also prove to be robust in the context of crowded areas.     

Dynamic Resource Allocation in Non-orthogonal Multiple Access Using Weighted Maximin Fairness Strategy for a UAV Network

Non-orthogonal multiple access (NOMA) with power domain multiplexing and successive interference cancellation (SIC) is one of the promising technologies for future wireless communication. The performance of NOMA is highly dependent on resource allocation such as power allocation and channel assignment. In this paper, we investigate the power allocation (PA) scheme, to optimize the weighted maximin fairness (MMF) for 2-user and 3-user clusters. We utilize the particle swarm optimization (PSO) based algorithm for power allocation due to its promising behavior. Application area of NOMA is becoming broader, then, we considered a cellular network, assisted by an unmanned aerial vehicle (UAV) as the base station (BS) which is integrated with the NOMA system. The PA for weighted MMF problem in NOMA is non-convex, it is difficult to find out the optimal solution directly. Simulation results show the performance of PSO-based algorithm in different adaptive weights and its convergence characteristics. We have also shown that the rate and fairness tradeoff using weighted maximin fairness. Numerical results compare the performance of NOMA and orthogonal multiple access (OMA) and prove the significance of the proposed algorithm.

     

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。     

Cognitive Radio Based Multi-User Resource Allocation in Mobile Ad Hoc Networks Using Multi-Carrier CDMA Modulation

In this paper, we propose a cognitive radio based multi-user resource allocation framework for mobile ad hoc networks using multi-carrier DS CDMA modulation over a frequency-selective fading channel. In particular, given preexisting communications in the spectrum where the system is operating, in addition to potential narrow-band interference, a channel sensing and estimation mechanism is provided to obtain information such as subcarrier availability, noise power and channel gain. Given this information, both frequency spectrum and power are allocated to emerging new users (i.e., cognitive radio users), based on a distributed multi-user resource allocation framework, in order to satisfy a target data rate and a power constraint of each cognitive radio user, while attempting to avoid interference to the existing communications as well as to minimize total power consumption of the cognitive radio users.     

一种面向CR-NOMA系统的动态功率分配算法

在密集小区的认知无线电非正交多址（cognitive radio non-orthogonal multiple access, CRNOMA）网络场景下,针对用户采取Underlay方式复用时信道频带利用率低的问题,提出了一种基于能效的组合用户动态功率分配算法.该算法在保证主用户服务质量前提下,基于用户之间的干扰和信干噪比,优化了组合多用户的接入方案,使信道接入用户数量最大且提高了频带利用率.同时,根据增益排序下的功率差额配比改进了剩余功率再分配方案,使空闲功率重新利用更加合理和有效.仿真结果表明,本文算法可以有效实现接入用户数量最大化的同时提高了频谱利用率.     

Fusion of artificial intelligence and game theory for resource allocation in non-orthogonal multiple access-assisted device-to-device cooperative communication

Device-to-device (D2D) communication offers a low-cost paradigm where two devices in close proximity can communicate without needing a base station (BS). It significantly improves radio resource allocation, channel gain, communication latency, and energy efficiency and offers cooperative communication to enhance the weak user's network coverage. The cellular mobile users (CMUs) share the spectral resources (e.g., power, channel, and spectrum) with D2D mobile users (DMUs), improving spectral efficiency. However, the reuse of radio resources causes various interferences, such as intercell and intracell interference, that degrade the performance of overall D2D communication. To overcome the aforementioned issues, this paper presents a fusion of AI and coalition game for secure resource allocation in non-orthogonal multiple access (NOMA)-based cooperative D2D communication. Here, NOMA uses the successive interference cancellation (SIC) technique to reduce the severe impact of interference from the D2D systems. Further, we utilized a coalition game theoretic model that efficiently and securely allocates the resources between CMUs and DMUs. However, in the coalition game, all DMUs participate in obtaining resources from CMUs, which increases the computational overhead of the overall system. For that, we employ artificial intelligence (AI) classifiers that bifurcate the DMUs based on their channel quality parameters, such as reference signal received power (RSRP), received signal strength indicator (RSSI), signal-to-noise ratio (SNR), and channel quality indicator (CQI). It only forwards the DMUs that have better channel quality parameters into the coalition game, thus reducing the computational overhead of the overall D2D communication. The performance of the proposed scheme is evaluated using various statistical metrics, for example, precision score, accuracy, recall, F1 score, overall sum rate, and secrecy capacity, where an accuracy of 99.38% is achieved while selecting DMUs for D2D communication.     

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。