多中继通信系统中量化误差补偿的MMSE中继预编码方案

为了补偿量化误差造成的系统性能的降级,文中提出将Grassmannian码本量化误差的统计特性引入多中继系统有限反馈中继预编码的设计,首先在QoS要求下的完全反馈中继预编码与接收均衡MMSE两步优化算法的基础上,给出了有限反馈下量化误差补偿的中继预编码与接收均衡MMSE两步优化方案,进而文中在中继和功率约束下,提出了一种有限反馈下量化误差补偿的中继预编码与接收均衡MMSE联合优化方案,并给出了中继预编码矩阵设计的闭合表达式.计算机仿真表明,文中提出的中继和功率约束下量化误差补偿的MMSE联合优化方案的系统性能优于QoS要求下量化误差补偿的MMSE两步优化方案,而且相比没有采用量化误差补偿的MMSE联合优化方案可以获得更低的误码率性能.     

基于协作中继的多点广播码分多址信息系统设计

为了提高多群多点广播中继网络系统的性能,提出一种改进的协作中继多点广播码分多址(CDMA)系统设计。该方案利用协作中继辅助的分布式波束形成 实现单天线基站多播,获得了较好的空间分集增益。在该系统中,多个基站利用多个中继节点向多个目的地的各个小组传播消息;利用CDMA技术来减少中继节点以及目的地节点的多址干扰(MAI)障碍,同时每个中继节点作为线性预编码波束合成器,可以在合适的代码空间重塑基站信号;对线性波束形成矩阵进行优化,使得中继节点的功率最小化,从而满足QoS在信号干扰噪声比方面的要求。系统性能仿真对比实验的结果表明,提出的改进方案明显优于传统的正交复用方案(FDMA / TDMA)。     

新的多代理签名和多代理多签名方案

涉及多个签名人的代理签名体制有三类：第一类称为代理多签名体制;第二类称为多代理签名体制;第三类称为多代理多签名体制。针对Lee等人的强代理签名方案和代理多签名方案中的安全缺陷,给出了新的改进方案,新方案能有效地防止原始签名人的伪造攻击,在改进方案的基础上给出了安全的多代理签名方案和多代理多签名方案。     

MIMO系统中的最优中继选择方案

研究多输入多输出中继系统中基于放大转发协议的最优中继选择方案,推导出中断概率和平均信道容量的闭式表达式,并对不同中继节点数时的中断概率和平均信道容量进行仿真。结果表明,该方案可以有效降低系统中断概率,且随着中继节点数的增多,系统平均信道容量优于直接传输方案。     

基于自适应量化信道信息的机会中继选择研究*

针对协同蜂窝网中基于发送量化信道状态信息的中继选择方案下,目的节点需要不停地获取所有中继处第一跳的信道信息而引起的系统开销问题,提出了一种基于自适应量化信道状态信息的机会中继选择方案。新方案下,仅在第一跳的瞬时信道条件高于预先设置的门限值时,各候选中继发送量化后的信道信息比特。仿真结果表明,改进方案在对系统性能影响不大的同时可以获得较高的比特利用率。同时,随着候选中继数从3增加至5时,中继点处设置的发送门限值可相应从0.267 1提升至0.575 6,这表明新方案具有较好的鲁棒性。     

面向移动自组网的高效多点中继选择算法

多点中继选择算法是一种泛洪技术,可用于移动自组网中信息的有效传播,减少不必要的节点选取及网络中数据包冲突的数量,从而达到节约节点能量、延长移动自组网的生存周期以及减少节点查找和信息传播的时间的目的。从探索集合覆盖理论与多点中继算法的关系入手,提出了新的适应度函数,并改进了经典的多点中继算法。最后采用模拟实验来验证提出的算法。仿真结果表明,该算法能够减少14%的搜索节点数目、12%的能量消耗以及9%的信息传递时间,在一定程度上改进了移动自组网的性能。     

天线多中继系统中分布式预编码方案的研究

在天线多中继系统优化问题的研究中,一般多中继系统源节点到中继和中继到目的节点的两个阶段的信道矩阵必须与其它中继节点共享,将使得系统开销增大。针对以上问题,提出了一种中继节点之间信道状态信息(CSI)连续共享方案。在源节点发送过来的CSI中,不是采用传统的以广播方式发包给所有中继,而是根据相位信息与中继节点矩阵的匹配,通过中继发送到目的节点。在中继节点处设计一种多用户分布式预编码方案,以改善和平衡目的节点接收信号的功率,使接收机实现相干合成,完成系统优化设计。仿真表明,提出的编码方案提高了系统容量,降低了编码复杂度,缓解了多入多出多中继系统中多路信号之间的干扰,提高系统的频谱效率,能很好地适用于多中继系统中。     

车联网中基于多参数决策的中继选择方案

5G时代,车联网是最具发展潜力的应用,也是未来智能交通管理系统的重要组成部分。但是,车联网本身也存在局限性。车联网中的车辆节点移动迅速,网络拓扑变化快,道路环境复杂,这些问题都将导致通信链路不稳定,甚至产生中断。因此,选择可靠、高效的中继节点来保障车联网的有效通信连接极为重要。提出基于多参数决策的中继选择方案,综合考虑候选中继节点的带宽、时延、节点切换预测值以及用户节点的相应需求,利用简单的线性加权函数评估候选中继的性能,最终得到最优中继。仿真结果表明,该方案在系统吞吐量和中继切换次数方面比传统方案更具优越性。     

改进的解码转发多跳中继系统及最优功率分配

多跳信道的中断性能较差,且节点接收设备上的多跳分集信道较为复杂。为此,基于解码转发多跳信道和多跳分集信道,提出一种改进的解码转发多跳中继系统,解决上述2种信道性能和复杂度的矛盾。推导中断概率的计算公式,以最小化系统中断概率为目标,利用拉格朗日乘子优化各节点的功率分配。仿真结果表明,改进系统能获得比传统多跳中继系统更低的中断概率,最优功率分配方案下系统的中断性能优于均匀功率分配方案,并且性能优势随跳数增加更为明显。     

基于应用层流量优化的中继路径选择方案

基于网络层路由协议的缺省单一路径难以满足高带宽应用的端到端传输需求,多径传输是一种有效方式。在基于应用层中继的多径传输系统的基础上,提出基于应用层流量优化的中继路径选择方案：借助于应用层流量优化机制,提出中继路径选择过程中遵循的规则,提出基于运营商定义域的最优中继路径生成算法,为数据传输分配优质的中继路径,同时在运营商定义域之间以及中继服务转发器之间保持负载均衡。仿真结果表明,提出的方案在选择优质中继路径方面具有较优性能,同时能够灵活地均衡运营商定义域之间的负载。     

协同通信中继选择技术的研究

协同通信是目前无线通信的研究热点,如何进行协同中继的选择成为协同通信中需要解决的首要问题。提出了协同中继选择技术的评价标准,并对近年来的算法进行了分类分析和比较,最后对协同中继选择算法的发展方向进行了展望。     

无线网络功率最小化的分布式中继选择方法

中继协作已视作提高边沿用户能量有效性和服务质量的新型技术.因此,针对存在瑞利衰落的解码转发中继网络如何选择中继节点以最小化系统总功率的问题,提出了使用分布式拍卖算法选择合适的中继节点以最小化系统总传输功率.该算法首先通过信道传输功率的闭合表达式得到用户节点和中继节点的最小传输功率,然后根据分布式拍卖算法为用户节点分配合适的中继节点.仿真结果显示用户节点仅需要通过和中继节点交换少量信息就可以选择合适的中继节点.     

基于势博弈的认知全双工中继选择策略研究

在对主用户干扰功率限制、自干扰限制和总功率干扰限制的网络中,针对认知中继选择算法复杂度较高的问题,提出基于势博弈理论的认知全双工协作网络下中继选择策略。认知中继选择问题被建模为使用认知协作网络的系统速率作为共同效用函数的势博弈模型,并分析出在没有不可行策略集信息的前提下,所提的博弈可以保证纯策略纳什均衡(NE)的存在性和可行性条件。在此基础上,给出全双工中继选择迭代算法,并对算法的复杂度进行讨论。仿真分析表明,所提算法在较低复杂度的情况下,能够获得最优或者接近最优速率的性能,并与传统的半双工中继模式相比,性能也有明显提升。     

Relay feedback method under large static disturbances

None of the previous relay feedback methods can provide a desired cyclic steady state in the case of large static disturbances, of which the magnitude is bigger than the magnitude of the relay. The proposed relay feedback method overcomes this limitation by placing a relay before a proportional-integral (PI) controller of which the integral part plays an important role in rejecting the large static disturbances. This is very attractive from a practical point of view because we do not need to define deviation variables in order to apply the proposed relay test. Furthermore, the proposed method can provide the frequency data of the process for a pre-specified phase angle by adjusting the integral gain.     

非对称双向多中继系统机会式网络编码中断概率分析

首先建立了非对称双向多中继系统数学模型,采用机会中继策略,推导出了该模型在译码转发方式下采用网络编码时的中断概率表达式, Monte Carlo仿真和理论值非常吻合,充分验证了该表达式的正确性。其次分析了不同中继节点位置,不同中继节点个数和不同功率分配因子等情况下的系统中断性能,揭示了功率分配因子与中继节点个数和位置以及系统总功率的内在关系。仿真结果表明,在非对称双向多中继系统中同时采用网络编码和机会中继时,功率分配因子取值为0.6时可获得最佳的系统中断性能,并指出在研究中断概率问题时,中继节点位置是一个不可忽略的因素。     

Relay selection for maximizing the number of successive transmission in cooperative networks

Relay selection has an important effect on improving the performance of cooperative communication system. However, the frequent operation of relay selection can bring enormous control message overhead, and then decrease the performance of cooperative communication. To reduce the relay selection frequency, in this paper, we propose a relay selection scheme to choose the best relay considering successive packets transmission. In this scheme, through the parameters of data transmission rate, the length of data packet and the estimated channel state information, the best relay is selected to maximize the number of successive packets transmission while guaranteeing the given outage probability. It is proven by numerical results that the proposed relay selection scheme can support the successive packets transmission in cooperative wireless networks and the maximum number of successive packets transmission is affected by the different network parameters, i.e. packet length, data transmission rate, signal to noise ratio and Doppler frequency. Compared to previous relay selection schemes by simulation results, it is shown that the proposed relay selection scheme can improve the throughput performance efficiently.     

A simple amplify-and-forward opportunistic relaying based on outdated channel state information

Opportunistic relay selection(ORS)is a promising approach for cooperative communications owing to its low complexity by activating only the best relay.However,in mobile scenarios,the channel state information(CSI)estimated in relay selection may be different from the actual CSI employed in data transmission due to relatively fast varying channels,i.e.,CSI is outdated,which may lead to incorrect relay selection,and hence system performance deteriorates.To address the problem,this paper designs a relay selection strategy with instaneous and statistical CSIs in amplify-and-forward(AF)cooperative networks whose instantaneous CSIs of two hops employed in relay selection are both outdated.Based on high signal-to-noise ratio(SNR)analysis,we propose a distinctive relay selection strategy which can be described as selecting the relay with the asymptotic optimum average symbol error probability(SEP)and outage probability at high SNR.The corresponding asymptotic outage probability and SEP performance analysis are also provided.Finally,simulation results not only validate our theoretical analysis,but also show that in asymmetrical outdated CSI scenarios,the proposed strategy achieves better performance than existing relay selection strategies at medium and high SNR values.     

Developing a Domain Model for Relay Circuits

In this paper we stepwise develop a domain model for relay circuits as used in railway control systems. First we provide an abstract, property-oriented model of networks consisting of components that can be glued together with connectors. This model is strongly inspired by a network model for railways made by Bj.rner et. al., however our model is more general: the components can be of any kind and can later be re.ned to e.g. railway components or circuit components. Then we show how the abstract network model can be re.ned into an explicit model for relay circuits. The circuit model describes the statics as well as the dynamics of relay circuits, i.e. how a relay circuit can be composed legally from electrical components as well as how the components may change state over time. Finally the circuit model is transformed into an executable model, and we show how a concrete circuit can be de.ned, checked to be legal, and the reaction to an input can be simulated.     

Joint resource allocation for lifetime-aware cooperative multi-carrier DF system

In this paper,we study the problem of optimal resource allocation for lifetime maximization in an orthogonal-frequencydivision multiplexing(OFDM)system with decode-and-forward relay.The goal is to minimize total energy cost of the system by jointly optimizing power allocation,subcarrier pairing and relay selection.We present a heuristic solution that is composed of two parts.The first part is an optimal power allocation approach to allocate power to a subcarrier pair of the source and the relay.The second part is a modified Hungarian algorithm to make subcarrier pairing and relay selection.Evaluations show that the presented scheme outperforms other schemes in the total transmitted data and the network lifetime.     

Does corticothalamic feedback control cortical velocity tuning?

The thalamus is the major gate to the cortex, and its contribution to cortical receptive field properties is well established. Cortical feedback to the thalamus is, in turn, the anatomically dominant input to relay cells, yet its influence on thalamic processing has been difficult to interpret. For an understanding of complex sensory processing, detailed concepts of the corticothalamic interplay need to be established. To study corticogeniculate processing in a model, we draw on various physiological and anatomical data concerning the intrinsic dynamics of geniculate relay neurons, the cortical influence on relay modes, lagged and nonlagged neurons, and the structure of visual cortical receptive fields. In extensive computer simulations, we elaborate the novel hypothesis that the visual cortex controls via feedback the temporal response properties of geniculate relay cells in a way that alters the tuning of cortical cells for speed.