阵列天线在OFDM系统下行链路中的应用

正交频分多址(OFDM:orthogonal frequency division multiplexing)技术由于其在多径环境下克服码间干扰的固有特点,在移动通信中已得到广泛地应用。利用阵列天线上行链路信号到达角估计实时信息,计算OFDM系统下行链路阵列天线权重,将阵列天线应用于下行链路中,最后给出系统误码率性能的计算机仿真结果。     

异构随机蜂窝网络上行性能分析

研究了两层蜂窝接入网(TTCAN)的上行能效和上行故障概率。为了在TTCAN中对上行链路能量效率和上行链路中断概率进行建模,通过考虑飞蜂窝接入点(AP)的接通/断开状态来导出信号干扰比(SIR)的闭合表达式。此外,二阶核函数首先用于解决TTCAN中的飞蜂窝AP的分析干扰模型。仿真结果表明,飞蜂窝用户的强度对TTCAN的上行能效和上行故障概率有很大的影响。这些结果为在实际TTCAN部署中开发新的节能方案提供了一些指导。     

LTE-Advanced载波聚合技术研究

LTE-Advanced(高级长期演进)是3GPP(第三代合作伙伴计划)LTE(长期演进)标准的增强版,载波聚合是其关键技术之一。载波聚合的原理是通过聚合多个载波,对上行链路/下行链路方向上(或同时)的最大带宽进行扩展。文章列举载波聚合对高层协议和架构的影响,描述载波聚合的物理层细节,研究由载波聚合导致的物理层上行链路和下行链路变化,分析载波聚合与移动性之间的关系,最后验证载波聚合性能。     

多载波码分多址系统在瑞利衰落信道中的性能分析

多载波码分多址(MC-CDMA)是一种把多载波和CDMA相结合的技术方案。在MC-CDMA中,每个数据符号通过N个子载波传输,且根据扩频码对每个子载波以0或π相位偏移进行编码。分别研究了MC-CDMA系统上行链路和下行链路的瑞利衰落信道模型以及采用等增益组合和最大比组合的接收机模型,并对上行链路和下行链路的系统误码率性能进行了分析和计算。数值结果表明,MRC在上行链路中的性能要优于EGC,但在下行链路中的抗干扰性能不如EGC。     

基于上行非正交多址接入技术的星空地融合网络性能分析

针对光电混合的星空地融合网络上行链路,该文研究了多天线波束成形技术和上行非正交多址接入(NOMA)技术相结合的系统遍历和速率性能。首先,在无人机采用多天线和上行NOMA技术条件下,为实现系统和速率最大化,提出了一种基于统计信道状态信息的波束成形方案。接着,假设卫星-无人机链路采用自由空间光链路且服从伽马-伽马衰落,无人机-地面用户链路采用射频链路且服从相关瑞利衰落,推导了系统和速率的闭合表达式。最后,通过数值仿真验证了理论分析的正确性。仿真结果表明,与正交多址接入(OMA)方案相比,所提方案提高了系统性能,并且与基准波束成形(BF)方案相比,所提方案具有更好的性能优势。     

WCDMA增强的上行链路关键技术及性能分析

文章首先介绍了上行链路提出的背景以及与下行链路的区别，接着介绍了上行链路的整体结构，重点分析了增强上行链路的关键技术，以及为了增加上行链路需要增加的物理信道，最后分析了增强上行信道的性能。     

卫星导航系统上行注入的研究现状与发展趋势

上行注入系统是卫星导航系统的生命线,是卫星导航系统不可或缺的一部分。详细研究了国外全球卫星导航系统和区域卫星导航系统的上行注入方案：全球定位系统（GPS）正由GPS II阶段过渡到GPS III阶段,上行注入也从全球布站的单星直接注入方案转变为本土布站的基于星间链路转发的注入方案,“伽利略”（Galileo）采取了全球布站的单星直接注入方案,而俄罗斯全球导航卫星系统（GLONASS）、准天顶卫星导航系统(QZSS)和印度区域导航卫星系统(IRNSS)采取了本土布站的单星直接注入方案。随着各大全球系统逐步研究、规划和开发星间链路,基于星间链路转发的上行注入方案势必成为全球系统的上行注入方案发展趋势,链路协同注入和高速传输也必然成为该方案的关键技术。     

应用于可见光通信的上行链路方案探讨

基于对采用射频、可见光、780⁹50 nm红外光作为可见光通信上行链路的分析,提出了采用1 550 nm激光作为可见光通信上行链路的全新方案,在典型室内应用场景下,与下行的可见光链路共同构成一套波分双工全光通信链路,其上行链路可达1 Gb/s。1 550 nm激光上行链路同样具有速率高、无电磁干扰、与保密性好等与可见光通信相一致的特点,可以成为可见光通信上行链路候选方案之一。     

多用户多载波无线携能通信系统的上下行联合资源分配

无线携能通信(SWIPT)技术是解决无线网络能量受限问题的有效方法,该文研究一个由基站(BS)和多用户组成的多载波SWIPT系统,其上行和下行链路均采用正交频分复用(OFDM)技术。在下行链路中,基站向用户同时进行信息与能量传输;在上行链路中,用户利用从基站接收的能量向基站回传信息。该文以最大化上下行加权和速率为目标,联合优化上行和下行的子载波分配和功率分配,提出基于拉格朗日对偶法和椭球法的最优联合资源分配算法。计算机仿真结果证实了该算法的有效性。     

HSUPA

HSUPA(high speed uplink packet access)被称为高速上行链路分组接入。我们都知道WCDMA Rel5中的HSDPA是WCDMA下行链路方向(从无线接入网络到移动终端的方向)针对分组     

基于认知的LTE系统动态频谱分配

传统的软频率复用(SFR)无法适应长期演进(LTE)系统中业务的动态分布,可能导致小区中心和边缘区域频谱利用率不均。针对此问题,该文提出一种基于认知的LTE系统动态频谱分配方法(Cog-DSA)。该方法利用基站间的相互协作获得频谱使用状态信息,从而确定可用频谱集合,并评估来自邻小区的同频干扰,最终根据可用资源块的通信质量,对重负荷小区边缘进行频谱的动态借用和服务基站的灵活选择。仿真结果表明,所提方法能够有效改善频谱利用率,减少小区间干扰,显著提升边缘用户的传输速率。     

高速客运通信系统中的动态资源预留

针对高速客运系统中用户频繁切换产生的大量资源开销,引入了组移动性概念,通过设置列车中继站,实现了车内用户的单用户切换方式.同时,针对大量用户同时切换至目标基站导致的基站拥塞,提出了基于基站协作的动态资源预留方案.即当前基站根据列车运行状态信息提前获知切换目标基站,并通告其资源需求,使其为车内用户预留资源.仿真结果表明列车业务量对系统性能产生了严重影响,采用动态资源预留方案,可以有效地提高列车用户的通信性能.     

基于用户分簇的认知超密集网络资源分配

针对5G时代小基站的密集部署带来的复杂干扰问题,对下行的认知无线电超密集网络下的资源分配进行了研究。为减小网络干扰,提高次用户吞吐量,提出了一种改进的基于用户分簇的资源分配算法。基于基站的覆盖范围,选出用户的强干扰基站,以用户-基站干扰关系建立用户-用户干扰图,按用户受到的平均弱干扰划分优先级对用户分簇,再为簇集群预分配频段,为每个簇分配对应频段中效用最大的信道。该资源分配算法能准确反映用户间的干扰关系,保障资源分配公平性。仿真结果表明,当用户密度与基站密度均较大时,与相同场景的已有算法相比,该改进算法有较好的抗干扰能力,能有效提高次用户的吞吐量。     

Improved bat optimization algorithm and enhanced artificial bee colony-based cluster routing scheme for extending network lifetime in wireless sensor networks

In this paper, improved bat and enhanced artificial bee colony optimization algorithm-based cluster routing (IBEABCCR) scheme is proposed for optimal cluster head (CH) selection with the merits of global diversity and improved convergence rate. It is proposed for achieving optimal CH selection by balancing the tradeoff between the phases of exploration and exploitation. It specifically targeted on the formulation of an ideal CH selection scheme using improved bat optimization algorithm (IBOA) for minimizing the energy depletion rate. It also focuses on the design of an enhanced artificial bee colony (EABC)-based sink node mobility scheme for determining the optimal points of deployment over which sink nodes can be moved to achieve better delivery of packets from CH to sink node. This CH selection and sink node mobility schemes are contributed for extending the network lifespan using the fitness function, which adopted the factors of node centrality, node degree, distance amid CH and base station (BS), distance among sensor nodes, and residual energy during CH selection process. The simulation experiments were performed using MATLAB version 2018, which confirmed that the number of alive nodes realized in the network is enhanced by 39.21% with the location of BS positioned at (100, 100). The number of rounds (network lifetime) is enhanced by 23.84% with different BS locations in the network. Furthermore, the packets received at the BS are also realized to be enhanced by 26.32% on an average in contrast to the baseline CH schemes used for investigation.     

基于基站协作的5G与NGSO星座系统间干扰规避方法研究

针对Q/V频段5G基站与非静止轨道(NGSO)卫星星座系统地球站之间的同频干扰问题,提出了一种基于5G基站协作的干扰规避方法。由多个5G基站组成基站簇,通过簇内基站间协作设置空间隔离来减缓5G基站对地球站的有害干扰。以OneWeb星座系统作为受扰系统,验证了所提方法的干扰减缓效果。结果表明,当干噪比门限值为-12.2 dB时,所提方法能够将OneWeb地球站的干扰发生概率减小30%。     

无线传感器网络LEACH协议的改进方案

基于LEACH协议,提出了一种改进方案,对LEACH协议的不足进行了改善。此方案中,簇头的选择取决于节点的剩余能量,且簇头数量与网络中的剩余节点数量相关,更符合网络特性。此外,改进方案对簇中节点数量进行了限制,使得分簇更加均匀,并采用了适应性信道分配原则,更加适用于动态网络。计算机仿真结果表明,与LEACH协议相比,采用改进方案后汇聚节点接收到的数据量明显增加,网络性能得到改善。     

Dynamic Cooperative Base Station Selection Scheme for Downlink CoMP in LTE-Advanced Networks

Coordinated Multi-Point (CoMP) transmission is a technique proposed to enhance the spectral efficiency and system throughput in an interference limited cellular networks. In CoMP joint processing (JP) scheme multiple base stations (BSs) are coordinately transmit data streams to each user. As more than two base stations are involved, abundant spatial resources are exploited and more backhaul spectrum for JP cooperation is required. The backhaul architecture for CoMP JP is crucial to provide low latency, unlimited capacity, less power consumption, and perfect synchronization among the BSs. However, satisfying all these constraints is impossible as the number of cooperative BSs increases for each user. In this paper, a dynamic cooperative base station selection scheme is proposed to reduce the backhaul load for CoMP user by selecting the appropriate number of coordinated BSs from the CoMP cluster to ensure the certain quality of service (QoS). In particular, for cell edge user the number of cooperative BSs per user has been selected in order to achieve reduced overhead and the allocation of backhaul capacity is performed under the max–min fairness criterion. Simulation results show that the proposed selection scheme achieves significant performance improvement than other transmission modes in terms of the average sum rate per backhaul use and minimal total power consumption.     

An Improved Fuzzy Unequal Clustering Algorithm for Wireless Sensor Network

This paper introduces IFUC, which is an Improved Fuzzy Unequal Clustering scheme for large scale wireless sensor networks (WSNs).It aims to balance the energy consumption and prolong the network lifetime. Our approach focuses on energy efficient clustering scheme and inter-cluster routing protocol. On the one hand, considering each node’s local information such as energy level, distance to base station and local density, we use fuzzy logic system to determine each node’s chance of becoming cluster head and estimate the cluster head competence radius. On the other hand, we use Ant Colony Optimization (ACO) method to construct the energy-aware routing between cluster heads and base station. It reduces and balances the energy consumption of cluster heads and solves the hot spots problem that occurs in multi-hop WSN routing protocol to a large extent. The validation experiment results have indicated that the proposed clustering scheme performs much better than many other methods such as LEACH, CHEF and EEUC.     

Energy‐efficient cluster division for multi‐cell joint transmission technology

Coordinated Multi‐Point (CoMP) is an effective way to improve user performance in next‐generation wireless cellular networks, such as 3GPP LTE‐Advanced(LTE‐A). The base station cooperation can reduce interference, and increase the signal to interference and noise ratio (SINR) of cell‐edge users and improve the system capacity. However, the base station cooperation also adds additional power consumption for signal processing and sharing information through back‐haul links between cooperative base stations. As such, CoMP may potentially consume more energy. This paper studies such energy consumption issue in CoMP, presents a semi‐dynamic CoMP cluster division algorithm based on energy efficiency (SCCD‐EE) that can effectively adapt to users' real‐time interference, and employs the idea of Maximal Independent Set (MIS) to solve the problem of cluster overlapping. To verify the feasibility of the proposed algorithm, this paper performs comprehensive evaluations in terms of energy efficiency and system capacity. The simulation results show that the proposed semi‐dynamic cluster division algorithm can not only improve the system capacity and the quality of service (QoS) of cell‐edge users, but also achieve higher network energy efficiency compared with static cluster methods and Non‐CoMP approaches. Copyright © 2016 John Wiley & Sons, Ltd.     

Convex-optimization-based precoding for MIMO downlinks

In this paper,the design of linear leakage-based precoders is considered for multiple-input multiple-output(MIMO) downlinks.Our proposed scheme minimizes total transmit power under each user's signal-to-leakage-plus-noise ratio(SLNR) constraint.When the base station knows perfect channel state information(CSI),suitable reformulation of design problem allows the successful application of semidefinite relaxation(SDR) techniques.When the base station knows imperfect CSI with limited estimation errors,the desig...