无线感知网的网络结构与路由协议研究

对于无线感知网本身问题的关注和研究目前正在成为该领域研究的一个的热点。随着I.F.Akyildiz对无线感知网体系结构和协议模型的总结和对协议栈框架的提出,对每一层协议的研究越来越多,其中重点主要集中在网络层和链路层。本文首先对无线感知网的网络结构进行了研究,提出了由这种特殊的网络结构决定的相应路由协议的特点。通过与无线自组网的比较,总结了无线感知网路由协议设计应当重点考虑的因素。接着,对现存几种主要的路由协议进行了较为详细的介绍,最后对其中几种最为普遍的协议进行了比较研究。

无线感知网的网络结构与路由协议研究

现在研究无线感知网相关的问题已经成为了网络研究领域当中的一个重点和热点,而随着有关研究工作人员对于协议模型的进一步结构化和总结可以看出现在协议方面的研究已经越来越深入和广泛,而现在研究的重点内容主要集中在了网络层当中。

无线感知执行网的智能协作机制研究

针对无线感知执行网中的节点协作问题,提出了多目标智能协作策略。在感知节点不完全连通的WSANs中,设计局部感知节点成簇算法,实现感知节点间的通信协作;以网络能耗均衡和信息传输时延为目标,应用离散多目标自由搜索算法对WSANs进行实时路径规划,实现簇头节点和执行节点间的协作,并通过路径惩罚策略和路径均衡策略,保证寻优结果的有效性、均衡执行节点之间的能耗。仿真实验表明:无线感知执行网智能协作机制能有效地选择多执行节点路径,实现网络协作的实时需求与能量消耗之间的平衡。

感知矿山物联网智慧照明系统设计

针对现有矿井照明系统存在低智能化、高能耗的问题,提出一种基于感知矿山物联网的矿井智慧照明系统的设计方案,给出了系统架构,介绍了系统无线感知子网的节点和系统控制实现流程。该系统根据移动目标位置和标签号自主判别并设置照明状态,达到节能效果;同时可将网络各节点状态信息上传至地面监控中心,便于节点的控制和维护;遇险时还可作为应急避险指示系统,具有避险功能。

基于状态转移的感知节点能耗模型研究与设计

针对基于理论模型的感知节点能耗研究通常仅考虑部件能耗、缺少从节点整体上分析与评估系统能耗问题的现状,通过分析节点部件在状态运行以及状态变迁时的能耗状况;基于状态转移的矩阵建模方式建立部件能耗模型;基于事件触发机制明确系统主要能耗部件之间的关联,建立节点整体的能耗模型。在OPNET上仿真验证了本模型的可靠性及实用性。仿真结果证明,本模型可为节点选型、协议评测以及网络构建分析提供模型支持和理论指导。

基于WebGIS的校园应急响应系统模型

在分析校园突发事件特点的基础上,以WebGIS技术为基础,建立了校园应急响应系统模型(Cam-pus Federal Emergency Response System-CFERS).在模型中定义了应急事件本体,以方便各个应急系统之间的集成,使用GIS系统对发生事件的类型和地点分别进行辨别和定位,然后根据预定的应急方案,启动相应的应急系统,并对应急方案实施的效果进行实时跟踪.

Reputation-Based Hierarchically Cooperative Spectrum Sensing Scheme in Cognitive Radio Networks

Cooperative spectrum sensing in cog- nitive radio is investigated to improve the det- ection performance of Primary User （PU）. Meanwhile, cluster-based hierarchical coop- eration is introduced for reducing the overhead as well as maintaining a certain level of sens- ing performance. However, in existing hierar- chically cooperative spectrum sensing algo- rithms, the robustness problem of the system is seldom considered. In this paper, we pro- pose a reputation-based hierarchically coop- erative spectrum sensing scheme in Cognitive Radio Networks （CRNs）. Before spectrum sensing, clusters are grouped based on the location correlation coefficients of Secondary Users （SUs）. In the proposed scheme, there are two levels of cooperation, the first one is performed within a cluster and the second one is carried out among clusters. With the reputa- tion mechanism and modified MAJORITY rule in the second level cooperation, the pro- posed scheme can not only relieve the influ- ence of the shadowing, but also eliminate the impact of the PU emulation attack on a rela- tively large scale. Simulation results show that, in the scenarios with deep-shadowing or mul- tiple attacked SUs, our proposed scheme ach- ieves a better tradeoff between the system robustness and the energy saving compared with those conventionally cooperative sensing schemes.

Determination of Threshold for Energy Detection in Cognitive Radio Sensor Networks

The Internet of Things （loT） is called the world＇ s third wave of the information industry. As the core technology of IoT, Cognitive Radio Sensor Networks （CRSN） technology can improve spectrum utilization efficiency and lay a sofid foundation for large-scale application of IoT. Reliable spectrum sensing is a crucial task of the CR. For energy de- tection, threshold will determine the probability of detection （Pd） and the probability of false alarm Pf at the same time. While the threshold increases, Pd and Pf will both decrease. In this paper we focus on the maximum of the difference of Pd and Pf, and try to find out how to determine the threshold with this precondition. Simulation results show that the proposed method can effectively approach the ideal optimal result.

A novel weighed cooperative bandwidth spectrum sensing for spectrum occupancy of cognitive radio network

In cognitive radio network(CRN), a secondary user(SU) may utilize the spectrum resource of the primary user(PU) and avoid causing harmful interference to the primary network(PN) via spectrum sensing. In the traditional time spectrum sensing, the SU cannot detect the PU's presence during its transmission, thus increasing interference to the PN. In this work, a novel weighed cooperative bandwidth spectrum sensing method is proposed, which allows multiple SUs to use part of the bandwidth to perform cooperative spectrum sensing throughout the whole frame in order to detect the PU's reappearance in time. The SU's spectrum efficiency is maximized by jointly optimizing sensing bandwidth proportion, number of cooperative SUs and detection probability, subject to the constraints on the SU's interference and the false alarm probability. Simulation results show significant decrease on the interference and improvement on the spectrum efficiency using the proposed weighed cooperative bandwidth spectrum sensing method.

Bidirectional secondary transmissions with energy harvesting in cognitive wireless sensor networks

To the existing spectrum sharing schemes in wireless-powered cognitive wireless sensor networks,the protocols are limited to either separate the primary and the secondary transmission or allow the secondary user to transmit signals in a time slot when it forwards the primary signal.In order to address this limitation,a novel cooperative spectrum sharing scheme is proposed,where the secondary transmission is multiplexed with both the primary transmission and the relay transmission.Specifically,the process of transmission is on a three-phase time-switching relaying basis.In the first phase,a cognitive sensor node SU1 scavenges energy from the primary transmission.In the second phase,another sensor node SU2 and primary transmitter simultaneously transmit signals to the SU1.In the third phase,the node SU1 can assist the primary transmission to acquire the opportunity of spectrum sharing.Joint decoding and interference cancellation technique is adopted at the receivers to retrieve the desired signals.We further derive the closed-form expressions for the outage probabilities of both the primary and secondary systems.Moreover,we address optimization of energy harvesting duration and power allocation coefficient strategy under performance criteria.An effective algorithm is then presented to solve the optimization problem.Simulation results demonstrate that with the optimized solutions,the sensor nodes with the proposed cooperative spectrum sharing scheme can utilize the spectrum in a more efficient manner without deteriorating the performance of the primary transmission,as compared with the existing one-directional scheme in the literature.

Detection Performance Analysis of Spectrum Sensing in Cognitive Radio Networks with Mobile Secondary Users

The majority of existing papers about spectrum sensing have the assumption that secondary users(SUs) are stationary. However,mobility is an essential feature of mobile communications networks. In this paper,the detection performance of spectrum sensing by mobile SUs was analyzed. Three performance metrics,i.e.,detection probability,miss detection probability and false alarm probability,were thoroughly investigated. In our analysis,a critical variable was the real-time received primary user signal power by a mobile SU. Its probability distribution and mathematical expectation were analytically derived. Moreover,the three performance metrics in single-node spectrum sensing and multi-node collaborative spectrum sensing systems were also derived. Extensive simulations were performed. The results are consistent with the theoretical analysis. And it is concluded that SU mobility has a significant impact on the detection probability and the miss detection probability,but not on the false alarm probability.

Practical network coding-aware routing protocol for multi-hop wireless networks

Network coding has been considered as one of the effective strategies that improve the throughput of multi- hop wireless networks. In order to effectively apply network coding techniques to the real multi-hop wireless networks, a practical network coding aware routing protocol is proposed in this paper, for unicast sessions in multi- hop wireless networks. The protocol is based on a novel routing metric design that captures the characteristics of network coding and unicast sessions. To ensure the novel routing mettle can operate with practical and widely available path calculation algorithms, a unique mapping process is used to map a real wireless network to a virtual network. The mapping process ensures that the paths with the biggest coding opportunities will be selected by commonly used path calculation algorithms. Simulation results show that the proposed routing protocol is effective to improve the network throughput.

Spectrum sensing sequence prediction in cognitive radio networks

Spectrum sensing is one of the key issues in cognitive radio networks. Most of previous work concenates on sensing the spectrum in a single spectrum band. In this paper, we propose a spectrum sensing sequence prediction scheme for cognitive radio networks with multiple spectrum bands to decrease the spectrum sensing time and increase the throughput of secondary users. The scheme is based on recent advances in computational learning theory, which has shown that prediction is synonymous with data compression. A Ziv-Lempel data compression algorithm is used to design our spectrum sensing sequence prediction scheme. The spectrum band usage history is used for the prediction in our proposed scheme. Simulation results show that the proposed scheme can reduce the average sensing time and improve the system throughput significantly.

Bamboo Winding Composite Utility Tunnels:a case study on mechanical behavior with WSN monitoring and numerical simulation

Bamboo Winding Composite Pipes(BWCPs)have many advantages such as good mechanical properties,low cost,low carbon,environmental friendliness,thermal insulation and easy installation et al.At present,BWCP is widely used in urban water supply,drainage,communication cable protection,farmland irrigation etc.It is obvious that the Bamboo Winding Composite materials have good application prospects in the field of utility tunnels.However,considering that the size of utility tunnels is much larger than that of normal pipelines,the wide application of Bamboo Composite Utility Tunnels(BCUTs)is still a challenge.In this paper,the force performance of BCUT in Datong Shanxi Province,was studied using two methods:real time monitoring and numerical simulation.Wireless sensor networks were used for monitoring,and the real time monitoring data of horizontal convergence and strains under the condition of backfill were obtained.The monitoring data indicated that the horizontal convergence can meet the requirement of relevant technical standards.A three-dimensional numerical model of the utility tunnel was established using FEM software.The influence of soil parameters on the deformation and strain of the BCUT was studied using the numerical method.The simulation results were compared with real-time monitoring data.The soil parameters K_(0) and k_(sh) have significant effects on the deformation,stress and strain of the utility tunnel.This kind of utility tunnel is recommended to use in areas with relatively good geological conditions.