A joint maximum likelihood algorithm for simultaneous track correlation and sensorbias estimation

In this study a joint maximum likelihood （JML） algorithm was developed to solve problems re- garding interdependent and contradictory relationships between track correlation and sensor bias estimation in multi-sensor information fusion systems. First, the relationships between track correlation and sensor bias estimation of a multi-sensor system were analyzed. Then, based on these relationships, a JML function of the track correlation and sensor bias estimation was developed, while an iterative two-step optimization procedure was adopted to solve the JML function. In addition, transformation of sensor bias from Cartesian coordinates to polar coordinates and a complete design of track quality and ambiguity processing were provided. Finally, several Monte Carlo simulations were built to test the effect of target density and different sensor bias in the JML algorithm. Simulation results showed that the JML algorithm presented in this paper had a higher correct correlation rate and more accurate sensor bias estimation than traditional methods, demonstrating that the JML algorithm had good performance.     

Jointly optimal congestion control, channel allocation and power control in multi-channel wireless multihop networks

In this paper, to increase end-to-end throughput and energy efficiency of the multi-channel wireless multihop networks, a framework of jointly optimize congestion control in the transport layer, channel allocation in the data link layer and power control in the physical layer is proposed. It models the network by a generalized network utility maximization (NUM) problem with elastic link data rate constraints. Through binary linearization and log-transformation, and after relaxing the binary constraints on channel allocation matrix, the NUM problem becomes a convex optimization problem, which can be solved by the gateway centralized through branch and bound algorithm with exponential time complexity. Then, a partially distributed near-optimal jointly congestion control, channel allocation and power control (DCCCAPC) algorithm based on Lagrangian dual decomposition technique is proposed. Performance is assessed through simulations in terms of network utility, energy efficiency and fairness index. Convergence of both centralized and distributed algorithms is proved through theoretic analysis and simulations. As the available network resources increase, the performance gain on network utility increases.     

基于二元多跳WSN的信道容错的目标定位方法

针对信道退化的多跳无线传感器网络下的定位问题,基于最大似然估计提出一种新的信道容错的定位算法.传感器节点接收到的源信号强度数据被压缩量化为二元信号,经Rayleigh退化信道多跳中继到达融合中心.利用信道退化统计量和译码策略,推导出二元观测数据的似然函数,基于最大似然估计获得目标定位,进一步给出目标位置估计的克拉美-罗下界.仿真结果表明了所提出算法的有效性.     

无线多跳传感器网络下基于粒子滤波的信道容错的目标跟踪方法

对信道衰落的无线多跳传感器网络下的目标跟踪问题, 提出一种新的信道容错的粒子滤波方法. 传感器观测数据被量化成二元信号, 经非理想无线信道多跳中继通讯到达融合中心. 中继节点采用一种二元中继策略, 中继输出是信道污染的中继信号的估计值. 在粒子滤波器下, 考虑实际的物理信道, 计算粒子的似然度函数. 将信道衰落结合进跟踪算法, 在已知信道衰落包络和信道统计分布下, 分别设计信道容错的粒子滤波算法. 仿真结果表明信道容错的粒子滤波器提高了目标跟踪的精度, 对非完美信道具有鲁棒性.     

针对不确定流量的多收发机无线网络资源优化研究

多收发机无线网络具有多接口多信道多跳的特点,是今后无线网络发展的趋势。该网络中信道与链路的资源分配,涉及路由、信道分配以及链路调度的联合优化。在以往的研究中通常对网络流量模型进行简化,假设其是确定且相对稳定的。考虑到实际网络中流量不确定性的特征,以网络吞吐量最大化为目标,提出传输流约束、信道资源约束以及干扰约束条件下的资源分配联合优化模型,以及基于不确定流量条件下资源分配最优解的链路调度策略。仿真实验结果证明所提出的路由、信道分配及链路调度方案能够更好地适应变化的网络流量需求。     

多信道无线Mesh网络信道分配算法

针对无线Mesh网络的带宽容量问题,文章通过使用无线网络干扰协议模型对无线链路的干扰进行量化,利用整数线性规划公式对信道分配问题进行描述,在信道分配的时候,应用目标函数对无线链路的信道分配进行优化,使网络总的干扰权重最小化,在此基础上提出一个信道分配的启发式算法。仿真结果表明,文章提出的算法能提高网络的吞吐量。     

多跳无线传感器网络下信道感知的目标定位方法

针对资源有限、存在信道退化的无线传感器网络(Wireless sensor network, WSN),基于最大似然估计(Maximum-likelihood estimation, MLE)提出一种信道感知的目标定位方法. 把传感器观测数据量化为M位二进制序列,经过衰落信道多跳中继到达融合中心. 中继节点采用二元解码-前向中继策略,中继输出是被信道污染的中继信号的估计值. 在Rayleigh信道衰落和高斯信道噪声假设下,结合无线信道衰落的统计知识和解码策略, 推导了观测数据的似然函数,得到目标位置的最大似然估计. 此外,还推导了估计器性能的后验克拉美-罗下界(Cramr-Rao lower bounds, CRLB). 仿真结果表明,信道感知的方法能够减缓由于信道衰落和噪声所带来的定位性能的退化.     

无线Ad hoc网络中基于0-1优化的两步骤资源分配算法

为了解决无线Ad hoc网络中节点性能随节点个数增加而下降的问题,利用多射频多信道技术(MR-MC)进行资源分配以及减少网络干扰量已成为优化无线网络性能的重要技术手段。在此基础上,提出了一种基于0-1规划的网络优化模型和两步骤资源分配算法TBCA&LS(Tree Based Channel Assignment&Link Scheduling)。该算法利用分簇重组网络结构,通过分析相邻链路干扰关系构建0-1优化模型,并在此基础上执行将信道分配和链路调度结合的资源分配算法,减少相邻链路冲突,增加并行传输量,进而达到提升网络吞吐量、优化网络资源分配的目的。最后,在Matlab仿真软件中执行两步骤资源分配算法,实验结果表明,与对比算法CCAS和仅利用信道分配的算法相比,所提算法可以有效优化网络性能。     

Rematch: a highly reliable scheduling algorithm on heterogeneous wireless mesh network

In highly dynamic and heterogeneous wireless mesh networks (WMN), link quality will seriously affect network performance. Two challenges hinder us from achieving a highly efficient WMN. One is the channel dynamics. As in real network deployment, channel qualities are changing over time, which would seriously affect network bandwidth and reliability. Existing works are limited to the assumption that link quality values are fixed, and optimal scheduling algorithms are working on the fixed values, which would inevitably suffer from the link quality dynamics. Another challenge is the channel diversity. In single channel wireless networks, channel assignment and scheduling are NP\mathcal{NP} -hard. And in multichannel wireless networks, it could be even harder for higher throughput and efficient scheduling. In this study, we firstly characterize the stochastic behavior on wireless communications in a Markov process, which is based on statistical methodology. Secondly, on exploiting the stochastic behavior on wireless channels, we propose a stochastic programming model in achieving maximized network utilization. Considering the NP\mathcal{NP} -hardness, we propose a heuristic solution for it. The key idea in the proposed algorithm is a two-stage matching process named “Rematch.” Indeed, our solution to the stochastic network scheduling is a cross-layer approach. Also, we have proved that it is 2-approximate to the optimal result. Moreover, extensive simulations have been done, showing the efficiency of “Rematch” in highly dynamic and distributed wireless mesh networks.     

Cross-layer optimization for wireless multihop multicast networks

Cyber-Physical System (CPS) is envisioned to tightly integrate the cyber-world of computation, communication, and control with the physical world. CPS is typically designed as a networked system of interacting sensors, actuators, and embedded computing devices to monitor and control the physical world. Thus, one of the essential building blocks of such a system is a highly efficient networking infrastructure. In this paper, we aims to develop an efficient wireless networking technology which can be utilized in CPS. More specifically, we develop a cross-layer optimization model based on the Network Utility Maximization (NUM) framework and its distributed solution for wireless multihop multicast networks exploiting multi-user diversity. It is known that the capacity of a wireless network can be increased by exploiting different channel conditions at different users, i.e., multi-user diversity; however, it is yet to be determined how much performance gain can be achieved by exploiting multi-user diversity in wireless multihop multicast networks. To address this problem, we extend the NUM framework and derive a new optimization problem including the benefits of multi-user diversity for multicasting scenarios in wireless multihop networks under a probabilistic media access control (MAC). In our problem, multi-user diversity is achieved via opportunistic scheduling. Then, we propose a distributed approximation algorithm for the problem. Our numerical results confirm that the benefit of multi-user diversity is prominent in a wireless multihop network with multicast flows.     

Jointly optimized congestion control,forwarding strategy,and link scheduling in a named-data multihop wireless network

As a promising future network architecture, named data networking (NDN) has been widely considered as a very appropriate network protocol for the multihop wireless network (MWN). In named-data MWNs, congestion control is a critical issue. Independent optimization for congestion control may cause severe performance degradation if it can not cooperate well with protocols in other layers. Cross-layer congestion control is a potential method to enhance performance. There have been many cross-layer congestion control mechanisms for MWN with Internet Protocol (IP). However, these cross-layer mechanisms for MWNs with IP are not applicable to named-data MWNs because the communication characteristics of NDN are different from those of IP. In this paper, we study the joint congestion control, forwarding strategy, and link scheduling problem for named-data MWNs. The problem is modeled as a network utility maximization (NUM) problem. Based on the approximate subgradient algorithm, we propose an algorithm called ‘jointly optimized congestion control, forwarding strategy, and link scheduling (JOCFS)’ to solve the NUM problem distributively and iteratively. To the best of our knowledge, our proposal is the first cross-layer congestion control mechanism for named-dataMWNs. By comparison with the existing congestion control mechanism, JOCFS can achieve a better performance in terms of network throughput, fairness, and the pending interest table (PIT) size.     

XCHARM: A routing protocol for multi-channel wireless mesh networks

Recent experimental results have pointed out the impact of physical layer multi-path fading and co-channel interference as the key factors influencing packet delivery among mesh routers (MRs) in wireless mesh networks. In addition, in a multi-channel environment, there exists significant power spectral overlap among channels used by MRs, leading to adjacent channel interference. In this paper, a cross-layer multi-radio, multi-channel routing protocol, XCHARM, is proposed in which the key contribution is the selection of the next hop, channel and transmission rate based on fading and interference concerns. The key features of our proposed protocol are as follows: (i) Routes are chosen based on the availability of channels that support high data rates, exhibit acceptable interference levels and long term resilience to fading related losses, (ii) The path latency is analytically calculated in advance for the candidate routes, accounting for channel induced errors, link layer contention, forward error correcting (FEC) codes, and the allowed data rates over the chosen channels, (iii) The route maintenance is performed by first attempting to identify and correct the point of failure before undertaking a global recovery action. An extensive performance evaluation, spanning the network, link and physical layers, reveals the benefits of adopting our cross-layer routing solution for wireless mesh networks.     

无线传感器网络中一种基于虚拟MIMO多播的多跳传输策略

虚拟MIMO技术能够有效减少信道衰落对无线链路的影响,节省无线传输时的能耗.结合MIMO多播和LEACH协议,提出新的虚拟MIMO多跳传输策略(VMMM),由于该策略避免了多跳数据转发时的簇内广播过程,从而提高整个网络的能量有效性.为优化该传输策略的性能,本文对VMMM策略的能耗进行建模分析,并在此基础上通过联合优化以确定满足最小能耗时的网络参数.仿真结果表明,与已有的虚拟MIMO多跳传输策略—vMISO协议相比,VMMM策略能够显著提高网络的能量有效性,有效延长网络生存时间达50%以上.     

基于优先级分类的工业无线网络确定性调度算法

确定性调度技术对于工业无线网络数据的实时性和确定性传输有着重要意义.本文针对工业无线网络数据流本身存在优先级分类属性的情况, 基于多信道时分多址接入(TDMA)技术, 在分析高优先级数据流对低优先级数据流造成的链路冲突延时和信道竞争延时基础上, 对网络进行调度预处理, 进而排除参数不合理的网络, 并向网络管理者反馈.对于通过预处理的网络, 调度算法优先为高优先级数据流的链路分配时隙和信道资源, 而对属于同一类优先级的数据流, 提出一种基于比例冲突空余时间的调度方案, 在满足可调度性条件的前提下, 根据各链路的比例冲突空余时间值从小到大依次分配时隙和信道资源.实验结果表明, 所提出的调度算法可以取得较高的网络调度成功率.     

一种异构多接口多信道无线网络的信道分配算法

多接口多信道技术是无线网络环境中减少链路干扰、提高网络吞吐量的有效途径,但如何合理有效地进行信道分配已成为多接口多信道无线网络所面临的主要问题之一.针对自私的网络节点,本文使用非合作博弈对异构条件下多接口节点的信道分配问题进行建模分析,其纳什均衡解为解决该问题所需的稳定的信道分配方案.本文首先讨论纳什均衡的存在条件并提出实现纳什均衡的分布式算法.此外,考虑到实际网络中节点仅能感知局部信道信息以及接口工作信道受限等因素,本文进一步改进算法并通过仿真实验对其收敛性进行证明.     

On the end-to-end flow allocation and channel assignment in multi-channel multi-radio wireless mesh networks with partially overlapped channels

The performance of wireless mesh networks (WMNs) can be improved significantly with the increase in number of channels and radios. Despite the availability of multiple channels in several of the current wireless standards, only a small fraction of them are non-overlapping and many channels are partially overlapped. In this paper, we formulate the joint channel assignment and flow allocation problem for multi-channel multi-radio WMNs as a Mixed Integer Linear Program (MILP). Unlike most of the previous studies, we consider the case when both non-overlapped and partially overlapped channels are being used. We consider an objective of maximizing aggregate end-to-end throughput and minimizing queueing delay in the network, instead of the sum of link capacities, since the traffic characteristics of a multi-hop WMN are quite different from a single hop wireless network. Our static channel assignment algorithm incorporates network traffic information, i.e., it is load aware. Our formulation takes into consideration several important network parameters such as the transmission power of each node, path loss information, the signal to interference plus noise ratio at a node, and the frequency response of the filters used in the transmitter and receiver. We show by simulations that our MILP formulation makes efficient use of the spectrum, by providing superior channel assignments and flow allocations with the addition of partially overlapped channels, without the use of any additional spectrum. We also justify the need to consider alternative objective functions such as, minimizing average queueing in the network. We also propose a polynomially bounded heuristic algorithm to scale the proposed algorithm to bigger network topologies.     

WMN中的干扰避免部分重叠信道分配算法

针对无线mesh网络(wireless mesh networks,WMN)中存在的信道干扰问题,提出一种基于部分重叠信道(partially overlapping channels,POC)的负载平衡且干扰避免的信道分配算法。通过基于Huffman树的通信接口分配方法连接邻居节点的接口;根据网络干扰情况,对链路进行迭代信道分配,使用静态链路调度保证网络连接;利用启发式算法优先为重要程度较高的链路分配无干扰时隙,对链路调度进行优化。仿真结果表明,在具有混合流量的WMN中,所提算法可以显著提升网络吞吐量,降低网络干扰与平均丢包率,改善网络性能。     

Upper-level scheduling supporting multimedia traffic in cellular data networks

Wireless data networks such as cdma2000 1x EV-DO and UMTS HSDPA use downlink scheduling that exploits channel fading to increase the system throughput. As future wireless networks will eventually support multimedia and data traffic together, we need a proper criterion for scheduling that can count various service requirements such as delay and packet loss. Although some previous approaches proposed opportunistic schedulers at the lower layer, it has not been investigated well whether they are able to meet explicit QoS defined at the upper layer. Hence, in this paper, we develop a hierarchical scheduling model that considers QoS provisioning and the time-varying channel feature separately. We focus on the upper-level QoS scheduling that supports various traffic classes in a unified manner. Supposing that a user gets some satisfaction or utility when served, we introduce a novel concept of opportunity cost, which is defined as the maximum utility loss among users incurred by serving a particular user at the current turn. We obtain each user’s net profit by subtracting the opportunity cost from its expected utility, and then select a user with the maximum profit for service. Simulation results reveal that our scheme supports various QoS classes well that are represented by delay and packet loss under various traffic loadings.     

一种基于IEEE 802.11e的多跳无线网络拥塞控制协议

多跳无线网络中网络拥塞的出现将严重降低网络的性能。基于802.11e提供的区分业务类型的信道接入优先级机制,提出了一种对尽力而为(best-effort)类型业务动态调整其优先级进行网络拥塞控制的协议。该算法的主要思想是对发生网络拥塞的节点提升其业务流传输的优先级使其获得更多的传输机会以缓解拥塞状况,并对严重的网络拥塞状况采取反向施压的策略降低上游节点业务流的转发速率。仿真结果表明,该算法有效地提高了网络重负载情况下的吞吐量。     

Cooperative beamforming design for physical-layer security of multi-hop MIMO communications在多跳MIMO通信系统下的基于物理层安全的协作波束赋形设计

The security issue is critically important for wireless communications, especially for multi-hop communications. In this paper, we propose a cooperative secrecy beamforming scheme for a multi-hop MIMO communication network, in which there is a single-antenna source, multiple multi-antenna relays and a singleantenna destination. Moreover, two types of eavesdroppers exist in the network, one of which has known channel state information (CSI), while the other not. To achieve security communications, in our work null-space beamforming and artificial noise beamforming are jointly optimized to improve the secrecy rate of the multi-hop network. In nature, the joint optimization is nonconvex and challenging. Exploiting its structure, the considered optimization problem is decoupled into a series of subproblems that can be efficiently solved based on convex optimization theory. Finally, some numerical experiment results are provided to assess the performance of the proposed secrecy beamforming design.