Retransmission or redundancy:Transmission reliability study in wireless sensor networks

As an application-driven network,wireless sensor network generally requires data reliability to maintain detection and response capabilities.Although two approaches,namely,retransmission and redundancy,have been proposed to enhance data reliability,the theoretical work is required to evaluate their impact on transmission reliability and energy efficiency.In this paper,we offer a comprehensive theoretical study on packet arrival probability and average energy consumption for both approaches.Our analysis and simulations indicate that when loss probabilities remain low or moderate,erasure coding,a typical redundancy-based scheme,is more energy efficient than retransmission.We also demonstrate that the resistance capability of erasure coding against packet loss weakens as the hop number increases,which motivates us to propose two improved mechanism based on the idea of the loss detection and the loss recovery.Finally,the simulation results carried out using TOSSIM verify the performance of different mechanisms both in the chain topology and the tree topology.     

State estimation over a communication network： measurement or estimate communication？

In this paper we consider the problem of state estimation over a communication network. Using estimation quality as a metric, two communication schemes are studied and compared. In scheme one, each sensor node communicates its measurement data to the remote estimator, while in scheme two, each sensor node communicates its local state estimate to the remote estimator. We show that with perfect communication link, if the sensor has unlimited computation capability, the two schemes produce the same estimate at the estimator, and if the sensor has limited computation capability, scheme one is always better than scheme two. On the other hand, when data packet drops occur over the communication link, we show that if the sensor has unlimited computation capability, scheme two always outperforms scheme one, and if the sensor has limited computation capability, we show that in general there exists a critical packet arrival rate, above which scheme one outperforms scheme two. Simulations are provided to demonstrate the two schemes under various circumstances.     

An adaptive epidemic information dissemination model for wireless sensor networks

We propose an adaptive bio-inspired information dissemination model that exploits the specific characteristics of the sampled/generated data stream (DS) in a wireless sensor network. Our model extends the basic epidemic algorithm by adapting key operational parameters (i.e., the forwarding probability and validity period) of the data dissemination process. The main idea is that the forwarding probability is tuned according to the variability of the involved DS. Our findings from the introduction of this adaptive epidemic are quite promising. Our scheme supersedes conventional probabilistic information dissemination algorithms in terms of efficiency and reliability.     

Traceback in wireless sensor networks with packet marking and logging

In a hostile environment, sensor nodes may be compromised and then be used to launch various attacks. One severe attack is false data injection which is becoming a serious threat to wireless sensor networks. An attacker uses the compromised node to flood the network and exhaust network resources by injecting a large number of bogus packets. In this paper, we study how to locate the attack node using a framework of packet marking and packet logging. We propose a combined packet marking and logging scheme for traceback (CPMLT). In CPMLT, one packet can be marked by up to M nodes, each node marks a packet with certain probability. When one packet is marked by M nodes, the next marking node will log this packet. Through combining packet marking and logging, we can reconstruct the entire attack path to locate the attack node by collecting enough packets. In our simulation, CPMLT achieves fast traceback with little logging overhead.     

无线传感网络的广播时效性研究

无线传感网络的节点采用时隙CSMA/CA协议获取信道并广播数据.为了度量信息广播的时效性,提出了广播信息年龄(broadcast age of information,bAoI)的概念.广播信息年龄等于当前时刻减去刚刚广播成功的那个数据包的生成时刻.bAoI量化了每个节点的数据包的新鲜度,并且描述了节点在网络上快速广播...     

Deployment of an unreliable robotic sensor network for spatial estimation

This paper studies an optimal deployment problem for a network of robotic sensors moving in the real line. Given a spatial process of interest, each individual sensor sends a packet that contains a measurement of the process to a data fusion center. We assume that, due to communication limitations or hardware unreliability, only a fraction of the packets arrive at the center. Using convex analysis, nonsmooth analysis, and combinatorics, we show that, for various fractional rates of packet arrival, the optimal deployment configuration has the following features: agents group into clusters, clusters deploy optimally as if at least one packet from each cluster was guaranteed to reach the center, and there is an optimal cluster size for each fractional arrival rate.     

Performance analysis for hierarchical resource allocation in multiplexed mobile packet data networks

The general packet radio service (GPRS) can be thought of as an overlay network above a Global Systems for Mobile (GSM) network. In cooperation with the GSM system, GPRS supports both voice and packet data services. Obviously, combining voice and data traffic implies the nature of contending with finite radio resources. The paper focuses on voice/data integrated GPRS downlink traffic and proposes two hierarchical resource allocation strategies by considering time slots and radio blocks simultaneously with two different TDMA frame configurations. The radio block based resource allocation can characterize the multiplexing scheme of the practical GPRS operation. The performance of the proposed strategies were evaluated analytically by multidimensional Markov chain and verified through intensive computer simulations. Based on both the analytical and simulation results, it showed that the proposed allocation strategies can offer high utilization of transmission resource, as well as low blocking probability to GPRS users. The results of the study provide not only a practical thinking for implementation but also a guideline for analysis.     

一种分布式的基于预留的多信道MAC协议

无线传感器网络(wireless sensor networks,WSNs)已经广泛应用于各个领域。许多领域利用了周期性数据汇聚,传感器节点周期性地产生数据包,通过一系列中继节点传输到汇聚节点。提出了一种分布式的基于预留的多信道MAC协议,称为R-MMAC协议,其中利用了预留机制和多信道通信机制,在多信道条件下,每个节点传输数据包时都将预留下一个数据包的传输,根据接收信号强度指示(received signal strength indication,RSSI)值选择自己的最佳信道进行预留。另外,还提出了针对预留时发生冲突的解决算法,利用信干噪比(signal to interference and noise ratio,SINR)和数据包接收率(packet reception rate,PRR)得到了预留的传输时间,从而降低了传感器节点到汇聚节点的传输时延和未来数据包的冲突概率。利用OMNET++5.3仿真工具对R-MMAC协议、X-MAC和EM-MAC协议进行了比较,结果表明R-MMAC协议实现了更低的端到端时延。     

HMCAWSN: A hybrid multi-channel allocation method for erratic delay constraint WSN applications

Increasing throughput and meeting high packet delivery ratio demands in delay constraint Wireless Sensor Network (WSN) applications have triggered the use of hybrid multi radio and multichannel communication techniques. There are many works in literature on such classical techniques which are deployed in wireless structured networks like IEEE 802.11. Indeed, they cannot be directly utilized for wireless sensor devices due to energy, memory, radio and processor constraints. A number of protocols have been recently proposed to utilize multichannel communication techniques designed for WSNs. However, there is still a high demand of contribution for designing new channel allocation approaches for multi radio and multichannel communication to meet emerging WSN requirements. In this paper, we propose a new multichannel allocation approach, named Hybrid Multi-Channel Allocation for WSNs (HMCA_WSN), based on hybrid Time Division Multiple Access (TDMA)–Frequency Division Multiple Access (FDMA) techniques and using dual radio with multichannel communication. A detailed simulation study indicates significant improvement on average and end-to-end delay results while keeping the sensor node energy consumptions at reasonable levels. Compared to its traditional and contemporary counterparts, the proposed HMCA_WSN assures steady and high packet delivery ratios in large scale networking environments even with hundreds of sensor nodes.     

Sleep–wake up scheduling with probabilistic coverage model in sensor networks1

Energy optimisation is one of the important issues in the research of wireless sensor networks (WSNs). In the application of monitoring, a large number of sensors are scattered uniformly to cover a collection of points of interest (PoIs) distributed randomly in the monitored area. Since the energy of battery-powered sensor is limited in WSNs, sensors are scheduled to wake up in a large-scale sensor network application. In this paper, we consider how to reduce the energy consumption and prolong the lifetime of WSNs through wake-up scheduling with probabilistic sensing model in the large-scale application of monitoring. To extend the lifetime of sensor network, we need to balance the energy consumption of sensors so that there will not be too much redundant energy in some sensors before the WSN terminates. The detection probability and false alarm probability are taken into consideration to achieve a better performance and reveal the real sensing process which is characterised in the probabilistic sensing model. Data fusion is also introduced to utilise information of sensors so that a PoI in the monitored area may be covered by multiple sensors collaboratively, which will decrease the number of sensors that cover the monitored region. Based on the probabilistic model and data fusion, minimum weight probabilistic coverage problem is formulated in this paper. We also propose a greedy method and modified genetic algorithm based on the greedy method to address the problem. Simulation experiments are conducted to demonstrate the advantages of our proposed algorithms over existing work.     

Numerical analysis of the power saving with a bursty traffic model in LTE-Advanced networks

We analyze the power saving operation called Discontinuous Reception (DRX) with a novel bursty packet arrival model in 3GPP Long Term Evolution (LTE)-Advanced networks. Typical analytical studies on the power saving operations in wireless networks have been carried out under the assumption that an expectation of exponentially distributed packet arrival intervals stays unchanged. However, practical packet arrival rate may change depending on time or typical Internet services may incur bursty packet arrivals. In either case, we need to evaluate the performance of the DRX operation. For this purpose, we develop a more realistic traffic arrival model considering packets may arrive in a bursty manner under the DRX operation. We, then, analyze the performance of the DRX operation in terms of power saving efficiency and average queuing delay, respectively. The analytical results are validated via comparisons with simulation results.     

一种改进的瑞利小波算法无线传感器网络流媒体传输研究

针对无线传感器网络中带宽和能量受限、误码率高、信道不稳定等因素严重影响了实时流媒体传输的问题,采用瑞利小波模型模拟无线传感器网络流媒体通信,并给出概率分布和突发特性的分析模型,基于Kal-man滤波器实时预测网络带宽,自适应地在SCTP与PRSCTP之间进行切换。仿真实验表明,瑞利小波模型能够准确地描述实时流媒体通信流,Kalman滤波器可以准确地预测实时网络带宽,而且基于带宽预测的流媒体传输技术与原有的技术相比在分组成功投递率、端到端时延和吞吐率上均具有良好的性能。     

Worst case dimensioning and modeling of reliable real-time multihop wireless sensor network

Wireless Sensor Network (WSN) should be capable of fulfilling its mission, in a timely manner and without loss of important information. In this paper, we propose a new analytical model for calculating RRT (Reliable Real-Time) degree in multihop WSNs, where RRT degree describes the percentage of real-time data that the network can reliably deliver on time from any source to its destination. Also, packet loss probability is modeled as a function of the probability of link failure when the buffer is full and the probability of node failure when node’s energy is depleted. Most of the network properties are considered as random variables and a queuing theory based model is derived. In this model, the effect of network load on the packets’ delay, RRT degree, and node’s energy depletion rate are considered. Also network calculus is tailored and extended so that a worst case analysis of the delay and queue quantities in sensor networks is possible. Simulation results are used to validate the proposed model. The simulation results agree very well with the model.     

Probabilistic quality-aware routing in cognitive radio networks under dynamically varying spectrum opportunities

In this paper, we introduce a probabilistic routing metric that considers the peculiar characteristics of the operating environment of cognitive radio networks (CRNs). This metric captures the dynamic changes in channel availabilities due to the randomness of primary user’s activity and the rich channel diversity due to the fact that a CRN is expected to operate over highly separated frequency channels with different propagation characteristics. Our metric, Probability of Success (PoS), statistically quantifies the chances of a successful cognitive radio (CR) packet transmission over a given channel. Based on the PoS metric, we propose a joint probabilistic routing and channel assignment protocol for multi-hop CRNs that attempts at selecting the path with the maximum probability of success among all possible paths for a given CR source-destination pair. Selecting such a path results in minimizing the number of disruptions to CR packet transmissions, which consequently improves network throughput. Simulation results verify the significant throughput improvement achieved by our protocol compared to reference CRN routing protocols.     

无线接入网数据包最大重传次数的仿真和优化

数据业务已经成为第三代移动通信系统区别于二代移动通信系统的一个显著标志。而无线传输环境的不稳定性则使得数据的传输不能像有线网络那样得到可靠的保障。因此,在三代通信系统的无线接入网部分设定了一系列的机制来尽量减少丢包的发生。文中重点研究的是无线链路层数据包的最大重传次数对系统性能的影响,通过仿真不同的场景来找出不同的最大重传次数对系统的影响规律,从而配置合理的参数,优化系统性能。     

Packet loss detection in networked control systems

One of the main issues related to the reliable operation of network control systems concerns the design of mechanisms able to detect anomalies in the functioning of the communication network through which the control loops are closed. In this article, we address the problem of detecting the occurrence of packet losses and design a mechanism that can detect the occurrence of packet losses directly from process sensor data. Specifically, we propose a moving‐horizon estimation scheme that permits to detect if the packet‐loss rate exceeds prescribed thresholds, which are representative of stability and performance of the control system. We discuss theoretical properties of the proposed solution along with an approximation scheme with reduced computational burden. A numerical example is discussed to substantiate the analysis.     

基于马尔可夫链的IEEE802.15.4网络防丢包信道访问机制研究

为了降低802.15.4MAC层数据帧丢包率,在分析丢包率的原因基础上,提出了一种基于Markov链的信道竞争机制模型。通过对网络发送、退避和信道检测状态的稳态概率进行数学推导,研究了信道碰撞和数据帧的丢包率分析式;最后研究了参数数据包到达速率、节点数量、误码率、后退指数、后退等待次数对碰撞概率和丢包率的影响。实验结果表明,与节点无休眠态的802.15.4网络相比,节点丢包率平均降低了23.7%,模型较好地描述了提出的MAC层信道访问机制,合理的网络参数设置能够优化数据帧丢包率,研究结果对无线传感网的应用提供可靠传输优化参考。     

A data model and algebra for probabilistic complex values

We present a probabilistic data model for complex values. More precisely, we introduce probabilistic complex value relations, which combine the concept of probabilistic relations with the idea of complex values in a uniform framework. We elaborate a model-theoretic definition of probabilistic combination strategies, which has a rigorous foundation on probability theory. We then define an algebra for querying database instances, which comprises the operations of selection, projection, renaming, join, Cartesian product, union, intersection, and difference. We prove that our data model and algebra for probabilistic complex values generalizes the classical relational data model and algebra. Moreover, we show that under certain assumptions, all our algebraic operations are tractable. We finally show that most of the query equivalences of classical relational algebra carry over to our algebra on probabilistic complex value relations. Hence, query optimization techniques for classical relational algebra can easily be applied to optimize queries on probabilistic complex value relations.     

一种改进离群区间计算的PRM带宽测量算法

主动式网络路径可用带宽测量是目前网络路径带宽测量使用的主要方法,与被动式网络路径可用带宽测量相比,具有更高的灵活性且部署方便。为解决主动式网络路径可用带宽测量定义不明确、通用性不强、协议不规范和结果不准确等问题,规范定义了探测通信协议和报文结构,建立了较为完整、统一和规范的主动式网络路径可用带宽测量框架,提出了序列时延增加度和基于序列时延增加度的离群区间计算方法,改进了网络背景流量分析方法,降低了背景流量对网络路径可用带宽测量的干扰,最后使用NS2仿真对比验证了该算法的有效性。     

On the design of resilient heterogeneous wireless sensor networks based on small world concepts

In this work, we propose on-line models to design heterogeneous sensor network topologies with small world features. The proposed model takes into account the data communication flow in this kind of network to create network shortcuts toward the sink node in such a way that the communication between the sink and the sensor nodes is optimized. The endpoints of these shortcuts are nodes with more powerful hardware, leading to a heterogeneous sensor network. We evaluate the on-line models and show that they present the same small world features observed in the theoretical models. When the shortcuts are created toward the sink node, with a small number of powerful sensors, the network presents better small world features and interesting tradeoffs between energy and latency in the data communication when compared with the Random Additional Model. We evaluate the resilience of the on-line models considering general and specific failures and, in both cases, the proposed model is more robust and presents a graceful degradation of the network latency, which shows the resilience of those models.