Random Walk Routing in WSNs with Regular Topologies

Topology is one of the most important characteristics for any type of networks because it represents the network's inherent properties and has great impact on the performance of the network. For wireless sensor networks (WSN), a well-deployed regular topology can help save more energy than what a random topology can do. WSNs with regular topologies can prolong network lifetime as studied in many previous work. However, little work has been done in developing effective routing algorithms for WSNs with regular topologies, except routing along a shortest path with the knowledge of global location information of sensor nodes. In this paper, a new routing protocol based on random walk is proposed. It does not require global location information. It also achieves load balancing property inherently for WSNs which is difficult to achieve by other routing protocols. In the scenarios where the message required to be sent to the base station is in comparatively small size with the inquiry message among neighboring nodes, it is proved that the random walk routing protocol can guarantee high probability of successful transmission from the source to the base station with the same amount of energy consumption as the shortest path routing. Since in many applications of WSNs, sensor nodes often send only beep-like small messages to the base station to report their status, our proposed random walk routing is thus a viable scheme and can work very efficiently especially in these application scenarios. The random walk routing provides load balancing in the WSN as mentioned, however, the nodes near to the base station are inevitably under heavier burden than those far away from the base station. Therefore, a density-aware deployment scheme is further proposed to guarantee that the heavy-load nodes do not affect the network lifetime even if their energy is exhausted. The main idea is deploying sensors with different densities according to their distance to the base station. It will be shown in this paper that incorporating the random walk routing protocol with the density-aware deployment scheme can effectively prolong the network lifetime.     

An efficient hop count routing protocol for wireless ad hoc networks

An efcient hop count route fnding approach for mobile ad hoc network is presented in this paper.It is an adaptive routing protocol that has a tradeof between transmission power and hop count for wireless ad hoc networks.During the route fnding process,the node can dynamically assign transmission power to nodes along the route.The node who has received route request message compares its power with the threshold power value,and then selects a reasonable route according to discriminating algorithms.This algorithm is an efective solution scheme to wireless ad hoc networks through reasonably selected path to reduce network consumption.Simulation results indicate that the proposed protocol can deliver better performances with respect to energy consumption and end-to-end delay.     

REMUDA: 一个实用地无线传感网络拓扑控制和数据转发机制

In wireless sensor networks, topology control plays an important role for data forwarding efficiency in the data gathering applications. In this paper, we present a novel topology control and data forwarding mechanism called REMUDA, which is designed for a practical indoor parking lot management system. REMUDA forms a tree-based hierarchical network topology which brings as many nodes as possible to be leaf nodes and constructs a virtual cluster structure. Meanwhile, it takes the reliability, stability and path length into account in the tree construction process. Through an experiment in a network of 30 real sensor nodes, we evaluate the performance of REMUDA and compare it with LEPS which is also a practical routing protocol in TinyOS. Experiment results show that REMUDA can achieve better performance than LEPS.     

Dynamic cluster head for lifetime efficiency in WSN

Saving energy and increasing network lifetime are significant challenges in wireless sensor networks （WSNs）. In this paper, we propose a mechanism to distribute the responsibility of cluster-heads among the wireless sensor nodes in the same cluster based on the ZigBee standard, which is the latest WSN standard. ZigBee supports ad hoc on-demand vector （AODV） and cluster-tree routing protocols in its routing layer. However, none of these protocols considers the energy level of the nodes in the network establishing process or in the data routing process. The cluster-tree routing protocol supports single or multi-cluster networks. However, each single cluster in the multi-cluster network has only one node acting as a cluster head. These cluster-heads are fixed in each cluster during the network lifetime. Consequently, using these cluster-heads will cause them to die quickly, and the entire linked nodes to these cluster-heads will be disconnected from the main network. Therefore, the proposed technique to distribute the role of the cluster head among the wireless sensor nodes in the same cluster is vital to increase the lifetime of the network. Our proposed technique is better in terms of performance than the original structure of these protocols. It has increased the lifetime of the wireless sensor nodes, and increased the lifetime of the WSN by around 50% of the original network lifetime.     

无线传感器网络中基于伸展树的感知节点分布优化

In a sensor network, reasonable distribution of sensor nodes will do much good to the improvement of sensorial ability. In a sensor network constructed by randomly scattering, a better sensing coverage can be achieved by topology adjustment utilizing mobility of some sensor nodes. To solve this problem, we define an extending-tree in the sensor network using Voronoi diagrams and Delaunay network. On this base, a new optimization algorithm of sensor node distribution based on genetic algorithm is designed, which provides a sound effective means to improve the sensorial ability of network. Simulation output shows that this algorithm can achieve an optimizing node distribution in the object area, by which sensorial ability of the whole sensor network can be improved at a relatively low cost.     

Sensor Distribution Optimization Based on Extending-tree in Sensor Network

In a sensor network,reasonable distribution of sensor nodes will do much good to the improvement of sensorial ability.In a sensor network constructed by randomly scattering,a better sensing coverage can be achieved by topology adjustment utilizing mobility of some sensor nodes.To solve this problem,we define an extending-tree in the sensor network using Voronoi diagrams and Delaunay network.On this base,a new optimization algorithm of sensor node distribution based on genetic algorithm is designed,which provides a sound effective means to improve the sensorial ability of network.Simulation output shows that this algorithm can achieve an optimizing node distribution in the object area,by which sensorial ability of the whole sensor network can be improved at a relatively low cost.     

NBgossip: An Energy-Efficient Gossip Algorithm for Wireless Sensor Networks

Gossip-based algorithms for information dissemination have recently received significant attention for sensor and ad hoc network applications because of their simplicity and robustness.However,a common drawback of many gossip- based protocols is the waste of energy in passing redundant information over the network.Thus gossip algorithms need to be re-engineered in order to become applicable to energy constrained networks.In this paper,we consider a scenario where each node in the network holds a piece of information(message)at the beginning,and the objective is to simultaneously disseminate all information(messages)among all nodes quickly and cheaply.To provide a practical solution to this problem for ad hoc and sensor networks,NBgossip algorithm is proposed,which is based on network coding and neighborhood gossip. In NBgossip,nodes do not simply forward messages they receive,instead,the linear combinations of the messages are sent out.In addition,every node exchanges messages with its neighboring nodes only.Mathematical proof and simulation studies show that the proposed NBgossip terminates in the optimal O(n)-order rounds and outperforms the existing gossip-based approaches in terms of energy consumption incurred in spreading all the information.     

Energy-aware routing for delay-sensitive underwater wireless sensor networks

The energy reduction is a challenging problem in the applications of underwater wireless sensor networks （UWSNs）. The embedded battery is difficult to be replaced and it has an upper bound on its lifetime. Multihop relay is a popular method to reduce energy consumption in data transmission. The energy minimum path from source to destination in the sensor networks can be obtained through the shortest path algorithm. However, because of the node mobility, the global path planning approach is not suitable for the routing in UWSNs. It calls for an energy-efficient routing protocol for the high dynamic UWSNs. In this paper, we propose the modified energy weight routing （MEWR） protocol to deal with the energy-efficient routing of delay- sensitive UWSNs. MEWR is a low flooding routing protocol. It can tolerate the node mobility in UWSNs and achieve a low end-to-end packet delay. MEWR can provide lower energy consumption than the existing low delay routing protocols through the dynamic sending power adjustment. The simulation results demonstrate the effectiveness of MEWR.     

Ultralow-power high-speed flip-flop based on multimode FinFETs

In this paper, we first reconstruct a novel planar static contention-free single-phase-clocked flipflop(S2CFF) based on high-performance fin-type field-effect transistors(FinF ETs) to achieve high speed and ultralow power consumption. Benefiting from better control of the conductive channel, the shorted-gate(SGmode) FinF ET flip-flop obtains a persistent reduction of 56.7% in average power consumption as well as a considerable improvement in timing performance at a typical 10% data switching activity, while the low-power(LP-mode) FinF ET flip-flop promotes the power reduction to 61.8% without appreciable degradation in speed.However, through further analysis of the simulation results, we have revealed an unnecessary energy loss caused by the redundant leaps of internal nodes at the static input ‘0’, which has a noticeable negative impact on total power consumption at low data switching activity. In order to overcome this defect, a conditional precharge technique is introduced to control the charging path, and we demonstrate that the independent-gate(IG-mode)FinF ET is the best option for the added control transistor. The verification results indicate that our optimization reduces the power consumption by more than 50% at low data switching activity with an acceptable area and setup time penalty compared with that of LP-mode FinF ET flip-flop.     

Balancing the power consumption speed in flat and hierarchical WSN

A combination of a cluster tree routing protocol and an Ad hoc on demand vector (AODV) routing protocol is used in the latest ZigBee standard wireless sensor networks (WSNs) technology. However, the AODV routing protocol has no means by which to take into consideration the power consumption of the nodes during the routing process. Therefore, a new approach is proposed in this paper to balance the power consumption speed and to distribute the responsibilities of routing among fiat wireless sensor nodes and the three levels of hierarchical wireless sensor nodes. These three levels are based on the three types of devices, which are used in the ZigBee standard: the coordinator, the touters, and the end devices. In this paper, we have compared the original AODV routing protocol with our extension approach for the distribution of power consumption. Based on the simulation results, our new approach has achieved better performance in terms of increasing the lifetime of the fiat wireless sensor network, the personal area network (PAN)coordinator, the touters, and the whole network of the hierarchical wireless sensor network. Additionally, it has better performance in terms of distributing the power consumption among the key nodes of the wireless sensor network.     

异构传感器网络能量空洞分析与避免研究

在无线传感器网络中,由于sink附近的节点承担远方节点数据的转发,故能量消耗较高,容易在sink附近形成能量空洞而使网络提前死亡.针对由初始能量较大节点充当簇头节点与初始能量较小的节点作为普通节点组成的异构分簇无线传感器网络,提出了不等簇半径工作能量空洞避免策略.策略的核心是让近sink的簇半径较小,而远sink的簇半径较大,这样,近sink部署的初始能量较大的簇头节点较多,因而能够减弱能量空洞的影响,以达到能量消耗均衡的目的.将能量空洞避免问题转化为在保证网络寿命满足应用需求约束前提下如何使部署的节点最小的优化问题,并详细给出了不等簇半径的取值与优化方法.理论分析与实验结果表明,所提出的策略对网络寿命与性能有较大的改善,对于异构传感器网络建设有较好的指导意义.     

矿井无线传感器网络路由机制研究

针对矿井巷道结构狭长而造成无线传感器网络节点能耗不均的问题,提出了一种新的矿井无线传感器路由机制,即矿井非均匀分簇LBUC-M协议:构造一个新的阈值公式以一定周期选举候选簇首,以非均匀半径确定最终簇首,使得远离汇聚节点的簇数量少、簇内节点多,靠近汇聚节点的簇数量多、簇内节点少,从而减轻靠近汇聚节点的簇首节点转发数据的负担,达到负载均衡的目的。仿真结果表明,LBUC-M协议有效减小了节点能耗,延长了网络生命周期。     

无线传感器网络数据融合协议比较

传感器网络由电池能量受限的节点组成,必须采用一种能量有效的方法收集节点感知的信息,如果每个节点都采用单跳方式将其感知的数据直接传输给汇聚节点,则与汇聚节点距离较远的节点能量将很快被耗尽。应用于无线传感器网络的LEACH协议提出了通过分簇实现数据融合的方法,簇头在接收到本簇成员的数据后进行融合处理,最终,将融合结果传输到汇聚节点。另一种应用数据融合的PEGASIS协议,是一种接近理想的基于链状的协议,它在LEACH协议的基础上做出了改进。在PEGASIS中,每个节点只与一个位置最近的邻居进行通信,并且,轮流传输数据到汇聚节点,然后,降低每一轮中的能量消耗。模拟结果表明:采用PEGASIS协议有效地延长了网络的生存时间。     

传感器网络中考虑负载平衡的节点密度控制策略

基于多跳路由的传感器网络具有集中式数据收集和多对一数据通信模式等特点,这容易导致数据通信出现漏斗效应,即离汇聚节点越近,网络越拥塞,节点能耗也越大,结果使某些节点甚至整个网络过早死亡。针对节点呈带状分布的同构单跳分簇网络,提出了两种能有效均衡网络负载的节点密度控制策略,通过控制各簇活动节点数量以及增加备用节点的方式,实现网络能耗的平衡。理论分析给出了两种策略下各簇活动节点数量以及所需备用节点数量的定量关系。两种策略均适合于网络负载动态变化的情况,而且不要求所有节点都能直接与基站通信,因此有着更广泛的应用场合。实验结果验证了两种策略的有效性。     

Termite-hill: Performance optimized swarm intelligence based routing algorithm for wireless sensor networks

A wireless sensor network (WSN) is a large collection of sensor nodes with limited power supply, constrained memory capacity, processing capability, and available bandwidth. The main problem in event gathering in wireless sensor networks is the formation of energy-holes or hot spots near the sink. Due to the restricted communication range and high network density, events forwarding in sensor networks is very challenging, and require multi-hop data forwarding. Improving network lifetime and network reliability are the main factors to consider in the research associated with WSN. In static wireless sensor networks, sensors nodes close to the sink node run out of energy much faster than nodes in other parts of the monitored area. The nodes near the sink are more likely to use up their energy because they have to forward all the traffic generated by the nodes farther away to the sink. The uneven energy consumption results in network partitioning and limit the network lifetime. To this end, we propose an on-demand and multipath routing algorithm that utilizes the behavior of real termites on hill building termed Termite-hill which support sink mobility. The main objective of our proposed algorithm is to efficiently relay all the traffic destined for the sink, and also balance the network energy. The performance of our proposed algorithm was tested on static, dynamic and mobile sink scenarios with varying speed, and compared with other state-of-the-art routing algorithms in WSN. The results of our extensive experiments on Routing Modeling Application Simulation Environment (RMASE) demonstrated that our proposed routing algorithm was able to balance the network traffic load, and prolong the network lifetime.     

DAR: An energy-balanced data-gathering scheme for wireless sensor networks

A wireless sensor network faces special challenges due to its inherent features, such as the limited energy. The energy constraint drives research on how to utilize energy efficiently to prolong the lifetime of the network. Because a sink node takes the responsibility of collecting data from other nodes, a usual conception is to transfer data towards the sink node by multihop. However, conventional data-gathering schemes based on the conception give rise to the hotspot problem because of the nodes that run out of their energy sooner than other nodes, which results in accelerating the end of the whole network. The closer sensor nodes are to the sink, the more quickly they exhaust their energy, which leaves an upper bound to the lifetime of the whole network. Because of the bottleneck nodes, the network loses its service ability regardless of a large amount of residual energy of the other nodes. In this paper, we propose a novel data-gathering scheme, DAR, to handle the hotspot problem, in which all the nodes participate in the workload of gathering data from the whole network and transferring the data directly to the sink. In our scheme, the forwarding behavior of all the nodes is scheduled to balance their burden of aggregating and transmitting the network data and the nodes may send their data back against the sink, which differs from the conventional schemes. We performed simulation experiments to evaluate the performance of the DAR scheme, and the results show that our data-gathering scheme can balance the energy consumption among all the nodes and extend the network lifetime notably.     

无线传感器网络中的簇头节点能耗平衡策略

无线传感器网络（WSNs）具有集中式数据收集和多对一数据通信等特点,使得越靠近汇聚节点的簇头节点能耗越大,最终导致网络中心出现能量空洞。提出一种基于簇内节点分配的簇头节点能耗平衡策略,根据WSNs的分簇汇聚拓扑结构,分析了其中簇头节点的能量消耗情况;在此基础上,通过在各簇内分配一定数量的基本节点,并成比例地增加附加节点的方式,使网络中各簇头节点的能量消耗相等。仿真结果表明：该策略能够适应网络规模和负载的动态变化,最终达到平衡簇头节点能耗的目的。     

一种新型无线传感器网络数据收集生成树

针对无线传感器网络精确数据收集,提出一种分布式生成树算法MLT.算法以一颗最小功率生成树为基础,在收集数据过程中不断统计节点剩余能量大小,找出瓶颈节点并与sink中存储的阈值比较,若低于阈值则转移瓶颈节点负担,优化树结构.研究表明随着阈值的增加网络生命周期先不断增大然后不断减小,阈值取值的合理性有效避免了因过于频繁变更树结构导致的额外能量消耗,使得所有节点能量较为均衡并延长了网络的生命周期,仿真实验验证了算法的有效性.     

DUCF: Distributed load balancing Unequal Clustering in wireless sensor networks using Fuzzy approach

Data gathering in wireless sensor networks (WSN) consumes more energy due to large amount of data transmitted. In direct transmission (DT) method, each node has to transmit its generated data to the base station (BS) which leads to higher energy consumption and affects the lifetime of the network. Clustering is one of the efficient ways of data gathering in WSN. There are various kinds of clustering techniques, which reduce the overall energy consumption in sensor networks. Cluster head (CH) plays a vital role in data gathering in clustered WSN. Energy consumption in CH node is comparatively higher than other non CH nodes because of its activities like data aggregation and transmission to BS node. The present day clustering algorithms in WSN use multi-hopping mechanism which cost higher energy for the CH nodes near to BS since it routes the data from other CHs to BS. Some CH nodes may die earlier than its intended lifetime due to its overloaded work which affects the performance of the WSN. This paper contributes a new clustering algorithm, Distributed Unequal Clustering using Fuzzy logic (DUCF) which elects CHs using fuzzy approach. DUCF forms unequal clusters to balance the energy consumption among the CHs. Fuzzy inference system (FIS) in DUCF uses the residual energy, node degree and distance to BS as input variables for CH election. Chance and size are the output fuzzy parameters in DUCF. DUCF assigns the maximum limit (size) of a number of member nodes for a CH by considering its input fuzzy parameters. The smaller cluster size is assigned for CHs which are nearer to BS since it acts as a router for other distant CHs. DUCF ensures load balancing among the clusters by varying the cluster size of its CH nodes. DUCF uses Mamdani method for fuzzy inference and Centroid method for defuzzification. DUCF performance was compared with well known algorithms such as LEACH, CHEF and EAUCF in various network scenarios. The experimental results indicated that DUCF forms unequal clusters which ensure load balancing among clusters, which again improves the network lifetime compared with its counterparts.     

Distributed duty cycle control for delay improvement in wireless sensor networks

Dynamically adjusting the time duration of a node to stay active in one data collection period, i.e., duty cycle, is an efficient strategy to save energy and prolong the lifetime of network. In this paper, we propose a novel Adaptation Duty Cycle Control (ADCC) scheme based on feedback signals for wireless sensor networks (WSNs) which can reduce to-sink data transmission delay while lifetime is also improved. In ADCC, every node adaptively adjusts its duty cycle by comparing its own energy consumption with the largest energy consumption of the entire packet delivery flow, which is stored in a feedback ACK packet generated by sink node. Since in WSNs, a huge number of sensor nodes in the area far from the sink node have much remaining energy when network dies, even up to 90 %, these nodes have much larger duty cycles in ADCC compared with previous schemes, therefore the data transmission delay can be reduced to a great extent. Additionally, ADCC provides a largest-energy notification mechanism in order to determine the appropriate duty cycle of nodes in each data collection flow according to the application-dependent requirements. Comparing with the Wake on Idle, Dual-QCon and the Same Duty Cycle (SDC) schemes, ADCC can reduce the delay by more than 59.5 % under the same network lifetime, or increase the lifetime by 32.8 %–63.4 % under the same delay requirements, while also increase energy efficiency as much as 43.1 %.