Modification of cutsets for reliability evaluation of communication systems

A general and simple technique for the evaluation of symbolic reliability expression in the case of practical systems such as a communication system having fixed channel capacities of its various communicating links, a computer communication network allowing a fixed amount of data exchange amongst different terminals of various computer centres and a power distribution system having limited power ratings of its various power lines, is presented. A system is considered reliable only if it successfully transmits at least the required system capacity from the transmitter to the receiver station. In this method, the various branch sets are obtained which completely disrupt the communication path, i.e. ensure system failure. It is observed that these branch sets are not necessarily the cutsets in the usual graph theoretic sense. The unreliability expression is then determined by adopting an existing method for making various terms disjoint. Two typical examples are solved by this method. It is observed that the method is computationally fast and efficient.     

A New Algorithm for Symbolic System Reliability Analysis

This paper presents a new algorithm for symbolic system reliability analysis. The method is applicable to system graphs with unreliable branches or nodes. Each branch is directed or undirected. Element probabilities need not be equal, but their failures are assumed to be s-independent. The new method makes no attempt to generate mutually exclusive events from the set of paths or cutsets but uses a technique to reduce greatly the number of terms in the reliability expression. Actual programming results show that the new method can efficiently handle systems having fewer than 20 paths or cutsets between the input-output node pair.     

基于OLSR协议的无线MESH网络系统设计

本文针对传统单跳无线网络(WLAN)可伸缩性低、鲁棒性差等缺点,提出了一种基于OLSR协议的无线MESH网络系统设计方法,该方法在提高对网络拓扑变化动态适应性的同时, 达到减少控制开销的目的。每个子网选择部分节点作为网络控制分组的多点中继节点(MPR), 其它邻居节点收到该节点发送的控制分组时,只进行处理而不转发,通过这种方式显著地减少了传统先应式路由协议网络拓扑信息广播的控制分组数量。每一个 MPR 节点只报告自己与其 MPR 节点之间的链路,进一步地减少了网络控制开销。该方法在城市数字化、城市无线监控等领域具有较高应用前景。     

Power and cost aware localized routing with guaranteed delivery in unit graph based ad hoc networks

In a localized routing algorithm, each node currently holding a message makes forwarding decision solely based on the position information about itself, its neighbors and destination. In a unit graph, two nodes can communicate if and only if the distance between them is no more than the transmission radius, which is the same for each node. This paper proposes localized routing algorithms, aimed at minimizing total power for routing a message or maximizing the total number of routing tasks that a network can perform before a partition. The algorithms are combinations of known greedy power and/or cost aware localized routing algorithms and an algorithm that guarantees delivery. A shortcut procedure is introduced in later algorithm to enhance its performance. Another improvement is to restrict the routing to nodes in a dominating set. These improvements require two‐hop knowledge at each node. The efficiency of proposed algorithms is verified experimentally by comparing their power savings, and the number of routing tasks a network can perform before a node loses all its energy, with the corresponding shortest weighted path algorithms and localized algorithms that use fixed transmission power at each node. Significant energy savings are obtained, and feasibility of applying power and cost‐aware localized schemes is demonstrated. Copyright © 2004 John Wiley & Sons, Ltd.     

一种低功耗高效无线传感器结点的硬件设计

本文基于IEEE 802.15.4/ZigBee协议,着重讨论了无线传感器节点的硬件架构。文章回顾了一些主要的常用芯片厂商提供的解决方案,列出了一些典型的组件及其相关的功耗等参数,其中讨论了其节点及子系统的体系结构,并分析了在典型应用中的无线传感器节点的特殊要求,基于此提出了一种可行的无线传感器节点的硬件结构。     

Link State Routing Based on Compressed Sensing

In table routing protocols such as link state routing, every node in the network periodically broadcasts its link state and the state of its neighbors. These routing updates result in the transmission of a large number of packets. Some of these packets contain correlated or even redundant data which could be compressed if there is central management in the network. However, in autonomous networks, each node acts as a router, in which case central coordination is not possible. In this paper, compressed sensing is used to reduce routing traffic overhead. This can be done at nodes which have greater processing capabilities and no power consumption limitations such as backbone nodes in wireless mesh networks. A method is proposed to select a subset of nodes and thus a subset of links to probe their state. The sensed states are encoded to generate a low dimension sampled vector. This compressed link state vector is broadcast to the entire network. Nodes can then reconstruct link states from this vector using side information. Performance results are presented which demonstrate accurate anomaly detection while adapting to topology changes. Further, it is shown that a proper choice of weighting coefficients in the sampling process can improve detection performance.     

Resource allocations in relay‐assisted cellular networks

In a relay‐assisted cellular network, the transmission mode (either direct transmission or relaying) and the transmit power of the source and relay nodes affect not only transmission rates of individual links but also the rates of other links sharing the same channel. In this paper, we propose a cross‐layer design that jointly considers the transmission mode/relay node selection (MRS) with power allocation (PA) to optimize the system rate. We first formulate an optimization problem for a cellular system, where the same frequency channel can be reused in different cells. A low complexity heuristic MRS scheme is proposed on the basis of the link and interference conditions of the source and potential relay nodes. Given the transmission mode and relay node (if the relaying mode is chosen) of each link, the transmit power of the source and relay nodes can be solved by geometric programming. This method for MRS and PA can achieve a close‐to‐optimum performance, but implementing the PA requires heavy signalling exchanged among cells. To reduce the signalling overheads, we finally proposed a heuristic and distributed method for MRS and PA inspired by some asymptotic analysis. Numerical results are conducted to demonstrate the rate performance of the proposed methods.Copyright © 2013 John Wiley & Sons, Ltd.     

A new algorithm for cluster head selection in LEACH protocol for wireless sensor networks

In wireless sensor network, a large number of sensor nodes are distributed to cover a certain area. Sensor node is little in size with restricted processing power, memory, and limited battery life. Because of restricted battery power, wireless sensor network needs to broaden the system lifetime by reducing the energy consumption. A clustering‐based protocols adapt the use of energy by giving a balance to all nodes to become a cluster head. In this paper, we concentrate on a recent hierarchical routing protocols, which are depending on LEACH protocol to enhance its performance and increase the lifetime of wireless sensor network. So our enhanced protocol called Node Ranked–LEACH is proposed. Our proposed protocol improves the total network lifetime based on node rank algorithm. Node rank algorithm depends on both path cost and number of links between nodes to select the cluster head of each cluster. This enhancement reflects the real weight of specific node to success and can be represented as a cluster head. The proposed algorithm overcomes the random process selection, which leads to unexpected fail for some cluster heads in other LEACH versions, and it gives a good performance in the network lifetime and energy consumption comparing with previous version of LEACH protocols.     

Detailed Analysis of Split-Level Combining

High level combining is a practical way to upgrade existing FM transmitters to IBOC. Very well understood, with readily available 10 dB couplers, it is a very attractive method with which to upgrade even the highest power levels in the field. Unfortunately, if offers only a combining efficiency of 83%, as 90% of the IBOC power is wasted into a dummy load, along with 10% of the generated FM power. Additionally, the power headroom demanded from the FM transmitter is proving to be an unsurpassable requirement for some existing sites ready to upgrade. This paper presents an innovative combining technique that minimizes the FM and IBOC power loss in high level combining. Instead of combining two totally incoherent signals with its known resulting losses, this method first achieves partial coherence of the signals, and only then combines them at an optimum coupling ratio. A system implemented this way offers two main benefits; a higher overall system efficiency, and the elimination of the need for FM headroom. Though the paper focuses on the particular case of FM HD radio upgrade, this technique can also be used whenever low loss is needed when combining dissimilar signals.     

Fault tree analysis method of a system having components of multiple failure modes

The problem of fault tree analysis of a system whose components can be dealt with by two states (success or failure) has been successfully solved in the last decade. On the other hand, in a practical system, there are a lot of components having multiple failure modes and each failure mode effects the system performance in a different way. Under this case, a two states method is not enough for exact analysis. This paper extends the ordinary method to the cases mentioned above. The method has been proved by the theory of measure. The paper gives the brief steps of constructing and evaluating a fault tree of a system having components of multiple failure modes. An example of a power supply system is presented. The problem has been perfectly solved.     

A novel method for the synthesis of magnetically coupled networks considering the frequency-dependence of the impedances

A new methodology for the representation of a set of magnetically coupled coils by means of an equivalent circuit is presented in this paper. The proposed method makes use of an equivalent circuit made up of a primary group of RL branches, which are the input terminals-pairs of the model, and a group of RL loops that are magnetically coupled with the primary branches, constituting a multiport model of a system of coupled coils that allows representing its frequency-behavior very accurately. This can be seen as a generalization of the classic methodology for the synthesis of RL driving-point impedances (developed by Foster and Cauer) considering the more general case of having multiple input terminals-pairs. This paper contributes an appropriate tool for the accurate modeling of transformer windings, a historically very difficult problem due to the frequency-dependence of the inductances and losses. The new method is first applied to the simple case of a single coil and was used afterward to the representation of a coil system, proving in both cases the mathematical validity of the method. The usefulness of the method is shown through its application to the modeling of a transformer winding.     

A cone-based distributed topology-control algorithm for wireless multi-hop networks

The topology of a wireless multi-hop network can be controlled by varying the transmission power at each node. In this paper, we give a detailed analysis of a cone-based distributed topology-control (CBTC) algorithm. This algorithm does not assume that nodes have GPS information available; rather it depends only on directional information. Roughly speaking, the basic idea of the algorithm is that a node u transmits with the minimum power p/sub u,/spl alpha// required to ensure that in every cone of degree /spl alpha/ around u, there is some node that u can reach with power p/sub u,/spl alpha//. We show that taking /spl alpha/=5/spl pi//6 is a necessary and sufficient condition to guarantee that network connectivity is preserved. More precisely, if there is a path from s to t when every node communicates at maximum power then, if /spl alpha//spl les/5/spl pi//6, there is still a path in the smallest symmetric graph G/sub /spl alpha// containing all edges (u,v) such that u can communicate with v using power p/sub u,/spl alpha//. On the other hand, if /spl alpha/>5/spl pi//6, connectivity is not necessarily preserved. We also propose a set of optimizations that further reduce power consumption and prove that they retain network connectivity. Dynamic reconfiguration in the presence of failures and mobility is also discussed. Simulation results are presented to demonstrate the effectiveness of the algorithm and the optimizations.     

Independent Turbo Coding and Common Interleaving Method among Transmitter Branches Achieving Peak Throughput of 1 Gbps in OFCDM MIMO Multiplexing

This paper proposes a common interleaving method associated with independent channel‐encoding among transmitter antenna branches in orthogonal frequency and code division multiplexing based on multiple‐input multiple‐output (MIMO) multiplexing to achieve an extremely high throughput such as 1 Gbps using a 100 MHz bandwidth. This paper also investigates the average packet error rate performance as a function of the average received signal energy per bit‐to‐background noise power spectrum density ratio (Eb/N0). We found that the loss in the required average received Eb/N0 of the proposed method is only within approximately 0.3 dB in up to a 12‐path Rayleigh fading channel, using 16QAM and Turbo coding with a coding rate of 5/6. We also clarify that even for a large fading correlation among antenna branches, 1 Gbps is still possible by increasing the transmission power. Therefore, the proposed method reduces the processing rate to 1/4 in the turbo decoder with only a slight loss in the required average received Eb/N0.     

基于雾计算的智能电表用户虚拟环隐私保护方案

作为智能电网的基础组件,智能电表(SMS)可以定期向电力公司报告用户的详细用电量数据。但是智能电表也带来了一些安全问题,比如用户隐私泄露。该文提出了一种基于虚拟环的隐私保护方案,可以提供用电数据和用户身份的隐私,使攻击者无法知道匹配电力数据与用户身份的关系。在所提方案中,智能电表可以利用其虚拟环成员身份对其真实身份进行匿名化,并利用非对称加密和Paillier同态系统对其获得的用电量数据生成密文数据;然后智能电表将密文数据发送给其连接的雾节点,雾节点定期采集其管理的智能电表的密文数据。同时,雾节点对这些智能电表的虚拟环身份进行验证,然后将收集到的密文数据聚合并发送给控制中心;最后控制中心对聚合后的密文进行解密,得到用电量数据。实验结果表明所提方案在计算和通信成本上具有一定的优势。     

Data aggregation in sensor networks using learning automata

One way to reduce energy consumption in wireless sensor networks is to reduce the number of packets being transmitted in the network. As sensor networks are usually deployed with a number of redundant nodes (to overcome the problem of node failures which is common in such networks), many nodes may have almost the same information which can be aggregated in intermediate nodes, and hence reduce the number of transmitted packets. Aggregation ratio is maximized if data packets of all nodes having almost the same information are aggregated together. For this to occur, each node should forward its packets along a path on which maximum number of nodes with almost the same information as the information of the sending node exist. In many real scenarios, such a path has not been remained the same for the overall network lifetime and is changed from time to time. These changes may result from changes occurred in the environment in which the sensor network resides and usually cannot be predicted beforehand. In this paper, a learning automata-based data aggregation method in sensor networks when the environment’s changes cannot be predicted beforehand will be proposed. In the proposed method, each node in the network is equipped with a learning automaton. These learning automata in the network collectively learn the path of aggregation with maximum aggregation ratio for each node for transmitting its packets toward the sink. To evaluate the performance of the proposed method computer simulations have been conducted and the results are compared with the results of three existing methods. The results have shown that the proposed method outperforms all these methods, especially when the environment is highly dynamic.     

A New Fault-Information Model for Adaptive & Minimal Routing in 3-D Meshes

In this paper, we rewrite the minimal-connected-component (MCC) model in 2-D meshes in a fully-distributed manner without using global information so that not only can the existence of a Manhattan-distance-path be ensured at the source, but also such a path can be formed by routing-decisions made at intermediate nodes along the path. We propose the MCC model in 3-D meshes, and extend the corresponding routing in 2-D meshes to 3-D meshes. We consider the positions of source & destination when the new faulty components are constructed. Specifically, all faulty nodes will be contained in some disjoint fault-components, and a healthy node will be included in a faulty component only if using it in the routing will definitely cause a non-minimal routing-path. A distributed process is provided to collect & distribute MCC information to a limited number of nodes along so-called boundaries. Moreover, a sufficient & necessary condition is provided for the existence of a Manhattan-distance-path in the presence of our faulty components. As a result, only the routing having a Manhattan-distance-path will be activated at the source, and its success can be guaranteed by using the information of boundary in routing-decisions at the intermediate nodes. The results of our Monte-Carlo-estimate show substantial improvement of the new fault-information model in the percentage of successful Manhattan-routing conducted in 3-D meshes.     

基于叠加调制策略的改进型协作分集方案

在无线传感器网络(WSN)中,协作分集是一种至关重要的技术。采用该技术,可利用WSN中冗余节点多的特性,用户间共享彼此的天线;从而,不仅可获得空间分集增益,而且可提高系统的吞吐量和抗衰落特性。但是,WSN中节点间如何进行协作,尤其是接收端如何译码以达到更高效的数据传输,仍然是一个值得进一步研究的问题。本文在传统传输方案的基础上引入了叠加调制策略。利用该策略,首先从节点间的链路状态和能量匹配的角度设计新型的符号映射算法,然后从信噪比和误码率方面考虑接收端的译码问题。与无协作方式、译码转发协作方式相比,这一优化算法不仅解决了传统协作方式的时隙利用率只有直通方式二分之一的问题,而且减少了误码率。此外,文中还证实了新算法可比传统传输方式最多获得3dB的信噪比增益。仿真结果表明,良好的链路状态在合适能量匹配参数时不仅可以同时传输自己和伙伴的数据,而且可以权衡系统的性能。      

Distributed simultaneous wireless information and power transfer in multiuser amplify‐and‐forward ad hoc wireless networks

This paper studies the problem of stable node matching for distributed simultaneous wireless information and power transfer in multiuser amplify‐and‐forward ad hoc wireless networks. Particularly, each source node aims to be paired with another node that takes the role of an amplify‐and‐forward relay to forward its signal to the destination, such that the achievable rate is improved, in return of some payment made to the relaying node. Each relaying node splits its received signal from its respective source into two parts: one for information processing and the other for energy harvesting. In turn, a matching‐theoretic solution based on the one‐to‐one stable marriage matching game is studied, and a distributed polynomial‐time complexity algorithm is proposed to pair each source node with its best potential relaying node based on the power‐splitting ratios, such that their utilities or payments are maximized while achieving network stability. For comparison purposes, an algorithm to enumerate all possible stable matchings is also devised to study the impact of different matchings on the source and relay utilities. Simulation results are presented to validate the proposed matching algorithm and illustrate that it yields sum‐utility and sum‐payment that are closely comparable to those of centralized power allocation and node pairing, with the added merits of low complexity, truth telling, and network stability.     

多业务CDMA系统中的前向功率预测

在综合语音、数据等多种业务CDMA蜂窝移动通信系统中，由于请求接入的各业务的传输速率和服务质量各不相同，小区基站的前向发射功率在接入业务后，变化的程度也各不相同，故为了保证系统的稳定性，必须对系统的前向发射功率进行限制，该文提出了一种在多业务，多速率环境下，CDMA系统接入新业务前向功率增量的预测方法，运用该方法预测了小区的前向发射功率，并与仿真结果进行了比较。     

Power management of autonomous wireless sensor node for structure health monitoring

This paper presents the design concepts of wireless sensor network system constructed with autonomous sensing nodes, which operates at extremely low power levels. At first, conventional, wired civil structure health-monitoring system is reviewed. Then, the monitoring methodology is discussed focusing quantitative measurement accuracy. Issues of node synchronized sampling, multi-layer cluster, node distance and integrated sensor node module are discussed. Also, radio transceiver protocol candidates are reviewed from the point of connection to the Internet gateway. Sensor node consists of microprocessor, sensing analog front end, and radio transceiver. Last two factors are critical for power consumption. Therefore, low duty cycle measurement is essential, in order to accomplish the ultra low power level, which is equivalent to energy harvesting source, such as piezoelectric and solar cells, sensor node power management device circuit design is demonstrated for the high-spec measurement.