基于NOMA技术的PLC-VLC用户配对和子载波分配方法

为了提高室内电力线通信和可见光通信(PLC-VLC)系统的吞吐量和用户体验的公平性,该文提出一种改进遗传算法优化用户配对联合子载波分配(IGA-JUPSA)方法.在IGA-JUPSA的用户配对阶段,设计了最优的非正交多址技术(NOMA)用户配对方法,提高PLC-VLC系统的吞吐量;在IGA-JUPSA的子载波分配阶段,设计NOMA与正交多址技术结合的子载波分配策略,设计改进的遗传算法优化不同NOMA组的子载波分配,提高系统的吞吐量和用户体验的公平性.仿真结果表明,所提的用户配对和子载波联合方法可以提高PLC-VLC系统的吞吐量和用户体验的公平性.     

多用户OFDM系统中一种新颖的自适应功率分配方案

针对多用户正交频分复用(OFDM)系统自适应资源分配的问题,提出了一种新的自适应子载波分配方案。子载波分配中首先通过松弛用户速率比例约束条件确定每个用户的子载波数量,然后对总功率在所有子载波间均等分配的前提下,按照最小比例速率用户优先选择子载波的方式实现子载波的分配;在功率分配中提出了一种基于人工蜂群算法和模拟退火算法(ABC-SA)相结合的新功率分配方案,并且通过ABC-SA算法的全局搜索实现了在所有用户之间的功率寻优,同时利用等功率的分配方式在每个用户下进行子载波间的功率分配,最终实现系统容量的最大化。仿真结果表明,与其他方案相比,所提方案在兼顾用户公平性的同时还能有效地提高系统的吞吐量,进而证明了所提方案的有效性。     

多业务MIMO-OFDMA/SDMA系统跨层调度与动态资源分配

对多业务MIMO-OFDMA/SDMA 系统下行链路跨层调度与动态资源分配问题进行了研究.首先,在满足各种约束条件的前提下,以最大化系统吞吐量为目标建立了相应的优化模型;然后,提出了一种基于业务类型和子空间距离的用户分组算法,该算法采用聚类分析的方法在每个子载波上对配置有多根接收天线的用户进行分组,从而降低了调度时所需搜索的用户空间的维数;接着,基于所提出的用户分组算法并结合不同业务的优先级提出了一种新的跨层调度和资源分配算法,该算法充分利用跨层信息为每个子载波调度相应的用户组,并为调度到的用户分配相应的系统资源,从而通过最大化每个子载波的吞吐量近似实现了系统整体吞吐量的最大化.仿真结果表明,与现有的方案相比,所提算法更好地满足了不同业务用户的QoS要求,并获得了更好的吞吐量性能.     

星上MF-TDMA系统信道管理方法

MF-TDMA被广泛应用于现代宽带通信卫星系统的上行链路设计中,而时隙分配算法是系统资源利用率的重要保证。针对MF-TDMA时隙分配复杂,时隙资源浪费严重等难题,该文给出一种可动态调整载波信道的MF-TDMA系统时隙分配算法,算法将天基移动通信系统用户接入时隙分配问题分解为载波确定和载波内时隙分配两个部分,并针对用户终端载波确定问题,给出一种带载波调整的RCP算法(RCP-A)算法,解决现有方法在多业务多用户条件下资源浪费大、使用率低的问题;针对载波内时隙分配问题,采用基于倒序时隙编号时隙资源树管理方式,解决业务因时隙分配而带来的时延抖动问题;并给出了适合星上处理能力的时隙资源管理其实现方法。仿真测试显示,该实现方法适合于星上MF-TDMA无线资源管理器。     

多载波系统随机子载波加权的物理层加密算法

针对多载波传输系统中,基于载波资源分配算法在窃听者信道质量优于合法用户的条件下无法实现安全传输的问题,建立了OFDM系统安全传输模型并在物理层提出了一种随机子载波加权的加密算法。该算法将合法通信双方的信道状态信息作为区分不同用户的唯一特征,并以此在发端为每个子载波数据设置随机加权因子扰乱窃听用户接收的信号,而合法用户能够通过发送参考解调算法恢复数据,仿真结果表明,发端采用该算法进行加密后,合法用户的误比特率随信噪比的增加迅速下降,而窃听用户误比特率始终为50%,系统具有一定的保密传输速率,有效实现了信息的安全传输。     

基于比例公平原则的多用户MIMO-OFDM系统资源分配

提出了一种基于比例公平原则提高MIMO-OFDM系统吞吐量的子载波和功率分配算法.它在总功率和误比特率的约束下,以获取最大系统吞吐量为目标,同时为兼顾用户间资源享用的公平性,根据用户速率成比例推导出了子载波分配限制准则.仿真结果表明,本算法不仅可满足不同用户的速率要求,而且平衡了容量最大化和用户间公平性的矛盾,同时计算...     

协作系统中基于比例公平的资源分配方法

针对多用户协作中继系统中的资源分配问题,提出了一种在满足用户速率比例公平约束条件下的新算法。该算法先将由2个时隙组成的中继用户传输链路转换为一个等效信道链路,将涉及子载波分配、中继选择和功率分配的组合优化问题转化为分步的次优化问题。该算法在等功率分配情况下,根据各用户速率比例公平系数进行初步子载波数目分配;以瞬时信道增益最佳原则,进行剩余子载波数目分配及具体子载波分配,同时完成中继选择;在速率比例公平约束条件下推导出次优化功率分配的闭式表达式,从而完成各子载波上的功率分配。仿真结果表明,该算法在有效提高系统容量的同时,保证了各用户速率之间的比例公平性。     

基于微时隙的eMBB和uRLLC业务传输性能研究

超可靠低时延通信(Ultra Reliable Low Latency Communications, uRLLC)是5G移动通信技术的重要场景之一。相较于增强移动宽带(Enhanced Mobile Broadband, eMBB),uRLLC业务有严格的时延、可靠性要求，对数据速率的要求相对较低。在5G NR中，uRLLC业务可以使用微时隙结构抢占eMBB资源进行传输，保证uRLLC业务满足时延要求，同时实现与eMBB业务的复用。基于微时隙结构进行业务抢占的方法，研究了在微时隙结构部署uRLLC业务时，eMBB业务和uRLLC业务的传输性能。首先为eMBB业务用户配置传输资源，然后使用微时隙结构将uRLLC业务穿刺到正在运行的eMBB业务中，在uRLLC业务传输完成后的下一个时隙开展eMBB业务重传以保证uRLLC业务的低时延要求。为了进一步降低uRLLC业务的块误码率，在使用微时隙穿刺的同时，通过设置更大的子载波间隔抑制载波间干扰。通过理论分析评估了该场景中eMBB业务和uRLLC业务的块误码率(Block Error Rate, BLER)和吞吐量性能；在时延性能方面，在对用户...     

无人机短包通信中基于NOMA传输的安全性能分析

针对物联网（IoT）通信的低延时需求,为了保证数据传输的灵活性,本文构建一种基于短包传输的无人机（UAV）通信网络。由于非正交多址接入（NOMA）技术能够增加可服务的地面用户数量,故将该技术应用到无人机短包通信（UAV-SPC）系统中可以解决多用户的安全传输问题。与正交多址（OMA）技术相比,NOMA可有效提高用户接入公平性和频谱利用率,因此被广泛用于下行链路的通信传输。为解决复杂的安全传输问题,首先证明在功率和译码错误率约束的条件下,分别存在最优的功率分配,数据传输包长和系统传输比特数使目标用户的平均安全吞吐量最大。在此基础上,通过本文所提算法得到安全传输问题的优化解。实验结果验证了该算法的稳定性和可行性。此外,与基准方案相比,本文所提方案可有效降低短包传输的通信时延,提高系统中目标用户的平均安全吞吐量。     

Interleaved-OFDMA中基于子空间的上行链路载波频偏估计方法

在OFDMA系统中,通过为每个用户分配不同的子载波可以实现并行数据传输.采用Interleaved子载波分配方法可以提高频率分集和系统容量,但是发射机和接收机之间的载波频率偏移会破坏子载波间的正交性,从而导致本用户的载波间干扰(ICI)以及用户间干扰(MUI).本文提出了一种基于子空间的两阶段频偏搜索方法,该方法只采用一个OFDMA符号块就可以实现Interleaved-OFDMA上行链路多个用户频偏的联合估计,并且不需要知道接入的用户个数及用户所占用的子信道,因此适用于随机分配子信道的情况.仿真结果验证了算法的精确度和有效性.     

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...     

Energy‐efficient resource allocation in D2D communications for energy harvesting–enabled NOMA‐based cellular networks

In this paper, we propose an energy‐efficient power control and harvesting time scheduling scheme for resource allocation of the subchannels in a nonorthogonal multiple access (NOMA)–based device‐to‐device (D2D) communications in cellular networks. In these networks, D2D users can communicate by sharing the radio resources assigned to cellular users (CUs). Device‐to‐device users harvest energy from the base station (BS) in the downlink and transmit information to their receivers. Using NOMA, more than one user can access the same frequency‐time resource simultaneously, and the signals of the multiusers can be separated successfully using successive interference cancellation (SIC). In fact, NOMA, unlike orthogonal multiple access (OMA) methods, allows sharing the same frequency resources at the same time by implementing adaptive power allocation. Our aim is to maximize the energy efficiency of the D2D pairs, which is the ratio of the achievable throughput of the D2D pairs to their energy consumption by allocating the proper subchannel of each cell to each device user equipment (DUE), managing their transmission power, and setting the harvesting and transmission time. The constraints of the problem are the quality of service of the CUs, minimum required throughput of the subchannels, and energy harvesting of DUEs. We formulate the problem and propose a low‐complexity iterative algorithm on the basis of the convex optimization method and Karush‐Kuhn‐Tucker conditions to obtain the optimal solution of the problem. Simulation results validate the performance of our proposed algorithm for different values of the system parameters.     

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。      

User scheduling and power allocation for nonfull buffer traffic in NOMA downlink systems

Nonorthogonal multiple access (NOMA) is one of the key technologies for 5G, where the system capacity can be increased by allowing simultaneous transmission of multiple users at the same radio resource. The most of the proportional fairness (PF)–based resource allocation studies for NOMA systems assumes full buffer traffic model, while the traffic in real‐life scenarios is generally nonfull buffer. In this paper, we propose User Demand–Based Proportional Fairness (UDB‐PF) and Proportional User Satisfaction Fairness (PUSF) algorithms for user scheduling and power allocation in NOMA downlink systems when traffic demands of the users are limited and time‐varying. UDB‐PF extends the PF‐based scheduling by allocating optimum power levels towards satisfying the traffic demand constraints of user pair in each resource block. The objective of PUSF is to maximize the network‐wide user satisfaction by allocating sufficient frequency and power resources according to traffic demands of the users. In both cases, user groups are selected first to simultaneously transmit their signals at the same frequency resource, while the optimal transmission power level is assigned to each user to optimize the underlying objective function. In addition, the genetic algorithm (GA) approach is employed for user group selection to reduce the computational complexity. When the user traffic rate requirements change rapidly over time, UDB‐PF yields better sum rate (throughput) while PUSF provides better network‐wide user satisfaction results compared with the PF‐based user scheduling. We also observed that the GA‐based user group selection significantly reduced the computational load while achieving the comparable results of the exhaustive search.     

Power allocation for downlink multiuser hybrid NOMA‐OMA systems: An auction game approach

Nonorthogonal multiple access (NOMA) is viewed as one of the key enabling candidate for the fifth‐generation systems. The effectiveness of such networks heavily relies on the power allocation. This paper addresses the problem of power allocation in a downlink multiuser hybrid NOMA‐orthogonal multiple access (OMA) network, where NOMA is integrated into OMA. Users with strong channel conditions are paired up with the users having weak channel conditions based on a random mechanism. Further, user pairs compete in an auction game for the transmit power being sold by the base station. Bids are placed iteratively by each user pair such that it maximizes their own utility. The existence of a unique Nash equilibrium has been proved theoretically. Simulation results show that the proposed scheme achieves higher average sum rate of users in comparison with that of the existing algorithms.     

无线供电混合多址接入网络的资源分配

无线供电技术是延长无线网络节点寿命的有效方案。该文研究一个由基站和多个分簇用户组成的无线供电混合多址接入系统。系统的传输分为两个阶段。在第1阶段,基站向用户广播能量;在第2阶段,用户向基站传输信息。用户簇和用户簇之间采用时分多址接入,分时传输;同一簇内多个用户采用非正交多址接入,同时传输。该文研究联合优化系统的各阶段的传输时间、基站的发射功率、用户的发射功率等资源,分别以优化网络频谱效率和用户簇之间的公平性为目的,提出最大化网络吞吐量和最大化用户簇的最小吞吐量的联合资源分配算法。研究结果表明所提的两种算法分别能有效提高系统的频谱效率和保证用户簇之间的公平性。     

Energy efficiency optimization algorithm for heterogeneous NOMA network based on imperfect CSI

In order to improve the suppression capability of parametric perturbation and energy efficiency (EE) of heterogeneous networks (HetNets),a robust resource allocation algorithm was proposed to maximize system EE for reducing cross-tier interference power in non-orthogonal multiple access (NOMA) based HetNets.Firstly,the resource optimization problem was formulated as a mixed integer and nonlinear programming one under the constraints of the interference power of macrocell users,maximum transmit power of small cell base station (BS),resource block assignment and the quality of service (QoS) requirement of each small cell user.Then,based on ellipsoid bounded channel uncertainty models,the original problem was converted into the equivalent convex optimization problem by using the convex relaxation method,Dinkelbach method and the successive convex approximation (SCA) method.The analytical solutions were obtained by using the Lagrangian dual approach.Simulation results verifiy that the proposed algorithm had better EE and robustness by comparing it with the existing algorithm under perfect channel state information.     

Power allocation and temporal fair user group scheduling for downlink NOMA

Non-Orthogonal Multiple Access (NOMA) has been proposed as a new radio access technique for cellular networks as an alternative to OMA (Orthogonal Multiple Access) in which the users of a group (pairs or triples of users in a group are considered in this paper) are allowed to use the wireless channel simultaneously. In this paper, for downlink single-input single-output SISO-NOMA, a heuristic power allocation algorithm within a group is first proposed which attempts to ensure that the users of a group benefit from simultaneous transmission equally in terms of achievable throughput. Moreover, a user group scheduling algorithm is proposed for downlink NOMA systems by which a user group is to be dynamically selected for transmission while satisfying long term temporal fairness among the individual contending users. The effectiveness of the proposed power allocation method along with the temporal fair scheduling algorithm for downlink NOMA is validated with simulations and the performance impact of the transmit power and the coverage radius of the base station as well as the number of users are thoroughly studied.

     

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.