无线传感器网络中不同节点分布模型的性能分析

针对传感器网络中较为关心的生存时间和覆盖率问题,对不同分布模型下的网络性能进行了分析。根据传感器网络中节点密度的分布规律,基于传统的分簇LEACH协议,选择对均匀分布、一次衰落和0.5方衰落三种随机分布场景下传感器网络的生存时间、覆盖率等指标进行了研究,仿真实验表明:对于三种传感器节点的撒布模型:一次衰落模型网络生存时间最长,但覆盖率最低;均匀分布网络生存时间最短,覆盖率最高;0.5次衰落模型下两项性能折中,更加符合现实需求。     

无线传感网物理层协作分集的性能分析

该文针对无线传感网中的远距传输问题,研究了一种无需网络同步和正交信道的协作分集方法的性能,给出了在两种典型信道中当解码转发存在误差传播时远程目的节点的误码率及分集指数;分析了当转发节点间为白高斯信道时增加协作节点数能够提高目的节点性能的条件。研究结果表明,当转发节点间为白高斯信道时,只要转发节点处于正常工作点,增加节点数就能提高目的节点的性能;当转发节点间为瑞利平衰落信道时,只有当转发节点处于一定位置时,协作分集相对于直接发送或传统空间分集才有性能增益;当转发节点间为瑞利平衰落信道时增加跳数性能更好,为白高斯信道时增加分支数更有效;当转发节点间为瑞利平衰落信道时,误差传播将使目的节点的分集指数为1,但在较低信噪比条件下对分集性能影响很小。     

Cooperative Connectivity Models for Wireless Relay Networks

This paper considers the ways that cooperating terminals can be connected to each other in wireless relay networks and the constraints imposed by the availability of different system resources. A framework is developed that exposes the relationship between constraints on available system resources and the achievable combinations of communication links between cooperating terminals. Cooperative connectivity models defined by the achievable combinations of links are derived, associated with their minimum cost constraint sets, and mapped to diversity techniques presented in the literature. The constraints considered are the available number of orthogonal relaying channels, the ability of terminals to diversity combine signals on a single common channel, the ability of terminals to diversity combine signals on orthogonal channels, the ability of terminals to transmit signals on multiple orthogonal channels, and the ability of terminals to cancel the effects of interhop interference.     

中继未知任何信道信息条件下中继选择的研究

由于信道情况差的中继对协作贡献小,且消耗额外的能量,基于某种标准选择出一个或者多个好的中继参加协作,可以提高协同通信系统性能,所以中继选择是协同通信系统的研究热点。针对一个发送端、接收端及每个中继都配置单根天线的无线中继网络,在假设发送方不知道信道信息而接收方已知全部信道信息前提下,本文提出了中继未知任何信道信息时的中继选择方案。首先提出基于信噪比最大的单中继选择方案,推导了单中继选择的成对错误概率表达式;其次提出基于中继排序方法的多中继选择方案,推导了选择2个中继的成对错误概率的下界;最后给出了仿真结果。理论与仿真结果都表明,中继未知任何信道信息的情况下,选择2个中继参加协作的系统错误概率却高于单中继选择。      

BER-Constrained Incremental Relaying with Relay Selection in Cooperative Wireless Networks

One of the main drawbacks of cooperative communication systems with half-duplex relaying is inefficient use of spectrum. Incremental relaying is an effective technique that overcomes this limitation, particularly in the high-SNR regime. In this paper, for a multi-relay cooperative network with arbitrary number of relay nodes, we propose a spectrally-efficient incremental relaying scheme that eliminates redundant relay transmissions such that an average end-to-end bit error rate (BER) constraint is satisfied. For detect-and-forward relaying, under the assumption of error propagation from the relays to the destination, we analyze the performance of the system in terms of the end-to-end BER, the average spectral efficiency and the outage probability for Rayleigh fading environment. The performance of the system depends on a single threshold employed by the relays and the destination. We optimize this threshold such that the average spectral efficiency of the system is maximized under an average end-to-end BER constraint. This optimization criterion results in a constant-BER, variable-spectral efficiency relaying scheme. The proposed scheme makes use of spectrum as efficiently as possible, while providing the required quality of service at the destination.     

An Analytical Model for Wireless Sensor Networks with Sleeping Nodes

We consider a wireless sensor network whose nodes may enter the so-called sleep mode, corresponding to low power consumption and reduced operational capabilities. We develop a Markov model of the network representing: 1) the behavior of a single sensor as well as the dynamics of the entire network, 2) the channel contention among sensors, and 3) the data routing through the network. We use this model to evaluate the system performance in terms of energy consumption; network capacity, and data delivery delay. Analytical results present a very good matching with simulation results for a large variety of system scenarios, showing the accuracy of our approach     

Performance Analysis of OSTBC Transmission in Amplify-and-Forward Cooperative Relay Networks

A performance analysis is presented for amplify-and-forward (AF) cooperative relay networks employing transmit antenna diversity with orthogonal space-time block codes (OSTBCs), where multiple antennas are equipped at the transmitter. We develop a symbol-error-rate (SER) and outage performance analysis for OSTBC transmissions with and without cooperative diversity over flat Rayleigh fading channels. We first derive exact probability density functions (pdf's) and cumulative distribution functions (cdf's) for the system SNR without direct transmission with an arbitrary number of transmit antennas and then present the exact closed-form SER and outage probability expressions. Next, we derive the moment-generating function (MGF) for the overall system SNR with direct transmission and present the exact SER and outage probability with joint transmit antenna diversity and cooperative diversity. The theoretical analysis is validated by simulations, which indicate an exact match between them. The results also show how the transmit antenna diversity and the cooperative diversity affect the overall system performance.      

Performance of RSS Based Cooperative Localization in Millimeter Wave Wireless Sensor Networks

Wireless Personal Communications - Localization in wireless sensor networks (WSNs) is a necessity as there is a vital need to have location information combined with the measured quantities. The...     

Relay Selection and Performance Analysis of Wireless Energy Harvesting Networks

Wireless Personal Communications - We proposed an integrated information relay and wireless power supply assisted RF energy harvesting-based cooperative dual-hope decode-and-forward (DF) relaying...     

Cooperative Caching in Wireless Multimedia Sensor Networks

The recent advances in miniaturization and the creation of low-power circuits, combined with small-sized batteries have made the development of wireless sensor networks a working reality. Lately, the production of cheap complementary metal-oxide semiconductor cameras and microphones, which are able to capture rich multimedia content, gave birth to what is called Wireless Multimedia Sensor Networks (WMSNs). WMSNs will boost the capabilities of current wireless sensor networks, and will fuel several novel applications, like multimedia surveillance sensor networks. WMSNs introduce several new research challenges, mainly related to mechanisms to deliver application-level Quality-of-Service (e.g., latency minimization). To address this goal in an environment with extreme resource constraints, with variable channel capacity and with requirements for multimedia in-network processing, the caching of multimedia data, exploiting the cooperation among sensor nodes is vital. This article presents a cooperative caching solution particularly suitable for WMSNs. The proposed caching solution exploits sensor nodes which reside in “positions” of the network that allow them to forward packets or communicate decisions within short latency. These so-called “mediator” nodes are selected dynamically, so as to avoid the creation of hot-spots in the communication and the depletion of their energy. The mediators are not more powerful than the rest of the nodes, but they have some special role in implementing the cooperation among the sensors. The proposed cooperative caching protocol includes components for locating cached data as well as for implementing data purging out of the sensor caches. The proposed solution is evaluated extensively in an advanced simulation environment, and it is compared to the state-of-the-art cooperative caching algorithm for mobile ad hoc networks. The results confirm that the proposed caching mechanism prevails over its competitor.     

无线协作网络中一种高效的分布式安全中继选择方法

Cloud computing is always adopted to enhance the computing capability of mobile systems , especially when the mobile users prefer to use some computation intensive applications . Consequently, the distributed wireless relay infrastructure should be deployed to aid the traffic transmission. To further enhance the QoS provisioning goals of wireless cooperative network, this paper puts forward a multiobjective approach for distributed optimal relay selection, which takes Bit Error Rate (BER) and Secrecy Capacity (SC) into account simultaneously. Firstly, our proposal partitions the channel state into several levels according to the received signaltonoise ratio (SNR) and describes the timevarying Rayleigh fading channel characteristics by using first order finitestate Markov model. Secondly, we model the relay selection as Restless Multiarmed Bandit optimal solution problem with respect to the channel state and the state transition probability. Finally, simulation results demonstrate the efficiency of the proposed approach which outperforms the existing ones .     

Performance Analysis of RSS-Based Localization in Wireless Sensor Networks

Wireless Personal Communications - In this paper, localization error of the received signal strength (RSS)-based method in mixed LOS/NLOS conditions is analysed. In contrast to the time of arrival,...     

Performance Analysis of Soft-Bit Maximal Ratio Combining in Cooperative Relay Networks

In digital cooperative relaying, signals from the source-destination and relay-destination links are combined at the destination to achieve spatial diversity. These signals may not necessarily belong to the same modulation scheme due to the varying channel qualities of the two links. Recently, we have proposed the "soft-bit maximum ratio combiner" (SBMRC) as a low complexity diversity combining scheme for signals with different modulation levels. SBMRC exhibits BER performance that is very close to the optimal maximum likelihood detector (MLD), but with much reduced complexity. In this paper, we revisit SBMRC and provide tight lower bound for the BER performance. Since SBMRC has BER performance slightly inferior to MLD, the derived lower bound can also be used as a good approximation for the BER performance of MLD.     

无线传感器网络中基于区域通信覆盖的节点定位投放算法

针对无线传感器网络中传感器节点投放分布对投放区域有效通信信号覆盖的影响,该文提出了一种基于通信覆盖的分布式投放概率覆盖(DDCP)算法。在保证投放精度的前提下,该算法根据传感器节点在投放区域中位置的不确定性以及信号衰减特性,建立信号覆盖模型,并通过概率优化获取传感器节点的最佳投放位置和投放数目。这样改善了区域通信覆盖,同时提高了投放效率和节省网络资源。通过仿真比较了在不同定位投放方法下的各相关性数据,验证了该算法实现高效投放的优越性和正确性。     

Energy-Aware Routing Algorithm for Wireless Sensor Networks with Optimal Relay Detecting

Efficient and reliable routing plays a key role in wireless sensor networks in which routing design with regard to network availability and node lifetime needs to be deliberately considered. When multi-hop relay transmission is frequently applied to reduce a source node’s energy consumption and improve network capacity, a key issue affecting the nodes’ participation in the transmission is the problem of suitably determining the next hop in order to prolong each node’s lifetime and to maintain the energy-balancing of the whole network. In this study, we propose an energy-aware routing scheme by taking the Cauchy operator, node’s residual energy and routing distance into account. Based on Cauchy inequation, we achieve a relationship between the routing distance and the energy usage in the routing. By fixing a relay selection parameter and then identifying the next hop appropriately, we obtain a balancing energy-aware routing algorithm. Numerical results are provided to verify the lifetime and equilibrium of the energy distribution by comparing with them with those of a traditional approach.     

Relay Node Placement with Base Stations in Wireless Sensor Networks Fault-Tolerant

It has been proposed to deploy relay nodes for the sake of prolonging Wireless sensor networks （WSN） lifetime, such that sensors transmit the sensed data to them which in turn delivers the data to base stations. For survivability requirements, relay placements which considers fault tolerant ability have been noticed and studied. While related works are limited or most existing works don＇t take factors such as fault tolerance, or base stations into account comprehensively in two tired WSN. We focus on fault tolerant relay node placement in two-tiered het- erogeneous WSN with base stations. As far as we know, fault tolerance contains two fundamental aspects, for one is multi-coverage and the second is multi-path. It is a NP- hard problem and figure out an approximation, whose approximation ratio is enhanced to be （18＋ε）. While a sub-problem approximation is also described as supplementary. Experimental results verify that the number of relay nodes deployed by our algorithm is somewhat superior to existed relay node placement solutions.     

Relay Node Deployment Strategies in Heterogeneous Wireless Sensor Networks

In a heterogeneous wireless sensor network (WSN), relay nodes (RNs) are adopted to relay data packets from sensor nodes (SNs) to the base station (BS). The deployment of the RNs can have a significant impact on connectivity and lifetime of a WSN system. This paper studies the effects of random deployment strategies. We first discuss the biased energy consumption rate problem associated with uniform random deployment. This problem leads to insufficient energy utilization and shortened network lifetime. To overcome this problem, we propose two new random deployment strategies, namely, the lifetime-oriented deployment and hybrid deployment. The former solely aims at balancing the energy consumption rates of RNs across the network, thus extending the system lifetime. However, this deployment scheme may not provide sufficient connectivity to SNs when the given number of RNs is relatively small. The latter reconciles the concerns of connectivity and lifetime extension. Both single-hop and multihop communication models are considered in this paper. With a combination of theoretical analysis and simulated evaluation, this study explores the trade-off between connectivity and lifetime extension in the problem of RN deployment. It also provides a guideline for efficient deployment of RNs in a large-scale heterogeneous WSN.     

k-Connected Relay Node Deployment in Heterogeneous Wireless Sensor Networks

Wireless Personal Communications - Compressive sensing (CS) is a new sampling theory used in many signal processing applications due to its simplicity and efficiency. However, signal reconstruction...     

Cooperative Distributed MIMO Channels in Wireless Sensor Networks

The large number of network nodes and the energy constraints make Wireless Sensor Networks (WSN) one of the most important application fields for Cooperative Diversity. Node cooperation increases the spatial diversity of wireless channels and, thus, reduces the transmitted power. In this paper, we propose a multi-hop WSN with nodes grouped in cooperative clusters that exploits transmit and receive cooperation among cluster nodes. Multi-hop transmission is carried out by concatenating single cluster-to-cluster hops, where every cluster-to-cluster link is defined as a cooperative distributed multiple-input-multiple-output (MIMO) channel. Transmit diversity is exploited through a time-division, decoder-and-forward, relaying scheme based upon two time slots: the Intracluster Slot, used for data sharing within the cluster, and the Intercluster Slot, used for transmission between clusters. At the receiver side, a distributed reception protocol is devised based upon a Selection Diversity algorithm. The proposed multi-hop cooperative WSN is optimally designed for minimum end-to-end outage probability by deriving the optimum time and power allocated on the intracluster and intercluster slots of every single hop, given a per-link energy constraint. A simplified suboptimum resource allocation is also proposed, which performs close to the optimal policy. Results show that the proposed scheme achieves diversity equal to the equivalent MIMO system and significantly reduces energy consumption with respect to. the non-cooperative channel     

Performance Analysis for a Wireless Sensor Network of Star Topology with Random Nodes Deployment

Wireless Personal Communications - A wireless sensor network is applied for detecting information, by nodes, then generates and transfers the packets to the clustering head for further...