Relay Sensor Research Articles

QoS-aware Opportunistic Cooperative ARQ Mechanism of Sensors Based on Channel state Sensing for Internet of Things

It is well known that the performance of Internet of Things application services is easy to be affected by internal noise of sensor, external environment interference and constriction of system resource. In order to solve the above problems, we studied the characteristics of bit error rate, outage ratio, signal to noise, and scale of relay sensors with channel state to choose the optimal transmission control scheme between direct mode and cooperative mode, building upon which we proposed the opportunistic cooperative automatic repeat request (ARQ) mechanism based on the rules and features of throughput ratio, average delay, packet error rate and energy efficiency, in consideration of retransmission time and channel quality. More importantly, the proposed opportunistic cooperative ARQ mechanism could set up the max retransmission time and control the progress of cooperative transmission according to the real-time network and sensor state, as well as Quality of Services (QoS) guarantee requirements of Internet of Things applications. The mathematical analyses and experiment results show that the proposed scheme is superior to the QoS provisioning schemes based on cooperative ARQ alone and direct transmission with channel state alone in terms of reliability, real time performance and life cycle of system, as well as energy efficiency.

Design of a Wireless Sensor Network Monitoring System for Biological and Pharmaceutical Products

Biological and pharmaceutical (B&P) products are essential in modern life. Currently, the demand and requirements of these products are dramatically growing; product quality and integrity then become crucial. As a key factor for ensuring quality and integrity, the current product status monitoring system needs to be enhanced in a more sophisticated and comprehensive way. This research describes the design of a wireless sensor network (WSN) monitoring system for B&P products supply chain management. In this study, the system architecture is presented based on the proposed framework. The framework consists of three processes: the first one is to generate a WSN with full coverage, the second one is to determine the optimal position of the sink, and the last process is to add additional relay nodes for providing fault tolerance to the network. Finally, a feasibility test on B&P product storage in a hospital is conducted. The proposed system provides a systematic approach for the deployment of sensor nodes and relay nodes. It also provides a relatively simple and rapid method for industries in general to follow and implement when designing a WSN system.

SEECH: Scalable Energy Efficient Clustering Hierarchy Protocol in Wireless Sensor Networks

The energy efficiency is an important issue for employ distributed wireless sensor networks in smart space and extreme environments. The cluster-based communication protocols play a considerable role for energy saving in hierarchical wireless sensor networks. In most of traditional clustering algorithms, a cluster head (CH) simultaneously serves as a relay sensor node to transmit its cluster/other clusters data packet(s) to the data sink. As a result, each node would have CH role as many as relay role during network lifetime. In our view, this is inefficient from an energy efficiency perspective because in lots of cases, a node due to its position in the network comparatively is more proper to work as a CH and/a relay. This paper proposes a new distributed algorithm named scalable energy efficient clustering hierarchy (SEECH), which selects CHs and relays separately and based on nodes eligibilities. In this way, high and low degree nodes are, respectively, employed as CHs and relays. In only a few past researches, CHs and relays are different, but their goal was mainly mitigation of CHs energy burden which is intrinsically satisfied by the proposed mechanism. To consider uniformity of CHs to balance clusters, SEECH uses a new distance-based algorithm. Comparisons with LEACH and TCAC protocols show obvious better performance of SEECH in term of lifetime. To evaluate the scalability of SEECH strategy, simulations are conducted in three different network size scenarios.

Joint adaptive power allocation and interference suppression algorithms based on theMSER criterion for wireless sensor networks

In this study, a two-hop wireless sensor network with multiple relay nodes is considered where the amplify-and-forward (AF) scheme is employed. Two algorithms are presented to jointly consider interference suppression and power allocation (PA) based on the minimization of the symbol error rate (SER) criterion. A stochastic gradient (SG) algorithm is developed on the basis of the minimum-SER (MSER) criterion to jointly update the parameter vectors that allocate the power levels among the relay sensors subject to a total power constraint and the linear receiver. In addition, a conjugate gradient (CG) algorithm is developed on the basis of the SER criterion. A centralized algorithm is designed at the fusion center. Destination nodes transmit the quantized information of the PA vector to the relay nodes through a limited-feedback channel. The complexity and convergence analysis of the proposed algorithms are carried out. Simulation results show that the proposed two adaptive algorithms significantly outperform the other previously reported algorithms.

A Cloud-Assisted Random Linear Network Coding Medium Access Control Protocol for Healthcare Applications

Relay sensor networks are often employed in end-to-end healthcare applications to facilitate the information flow between patient worn sensors and the medical data center. Medium access control (MAC) protocols, based on random linear network coding (RLNC), are a novel and suitable approach to efficiently handle data dissemination. However, several challenges arise, such as additional delays introduced by the intermediate relay nodes and decoding failures, due to channel errors. In this paper, we tackle these issues by adopting a cloud architecture where the set of relays is connected to a coordinating entity, called cloud manager. We propose a cloud-assisted RLNC-based MAC protocol (CLNC-MAC) and develop a mathematical model for the calculation of the key performance metrics, namely the system throughput, the mean completion time for data delivery and the energy efficiency. We show the importance of central coordination in fully exploiting the gain of RLNC under error-prone channels.

Adaptive Opportunistic Cooperative Control Mechanism Based on Combination Forecasting and Multilevel Sensing Technology of Sensors for Mobile Internet of Things

In mobile Internet of Things, there are many challenges, including sensing technology of sensors, how and when to join cooperative transmission, and how to select the cooperative sensors. To address these problems, we studied the combination forecasting based on the multilevel sensing technology of sensors, building upon which we proposed the adaptive opportunistic cooperative control mechanism based on the threshold values such as activity probability, distance, transmitting power, and number of relay sensors, in consideration of signal to noise ratio and outage probability. More importantly, the relay sensors would do self-test real time in order to judge whether to join the cooperative transmission, for maintaining the optimal cooperative transmission state with high performance. The mathematical analyses results show that the proposed adaptive opportunistic cooperative control approach could perform better in terms of throughput ratio, packet error rate and delay, and energy efficiency, compared with the direct transmission and opportunistic cooperative approaches.

Maximum WSN coverage in environments of heterogeneous path loss

We study wireless sensor network (WSN) node placement in an environment where RF signal losses vary with position. This reflects real-world outdoor environments where vegetation and topography cause nonuniform path loss. Many techniques that solve for a variety of objective functions subject to various constraints have previously been proposed for node placement. However, many of these methods make simplifying assumptions such as all nodes having the same transmission range. Our goal is to take the insights and approaches of this previous ork and extend it to real-world environments. The present work assumes we have a map that quantifies the path loss behaviour of the real environment. Based on this map, and a path loss model that accounts for spatial variations in the path loss exponent, we propose a node placement algorithm for two-tiered WSNs that maximises the area covered by a specified number of relay nodes and sensor nodes.

Cooperative Transmission in Mobile Wireless Sensor Networks with Multiple Carrier Frequency Offsets: A Double-Differential Approach

As a result of the rapidly increasing mobility of sensor nodes, mobile wireless sensor networks (MWSNs) would be subject to multiple carrier frequency offsets (MCFOs), which result in time-varying channels and drastically degrade the network performance. To enhance the performance of such MWSNs, we propose a relay selection (RS) based double-differential (DD) cooperative transmission scheme, termed RSDDCT, in which the best relay sensor node is selected to forward the source sensor node’s signals to the destination sensor node with the detect-and-forward (DetF) protocol. Assuming a Rayleigh fading environment, first, exact closed-form expressions for the outage probability and average bit error rate (BER) of the RSDDCT scheme are derived. Then, simple and informative asymptotic outage probability and average BER expressions at the large signal-to-noise ratio (SNR) regime are presented, which reveal that the RSDDCT scheme can achieve full diversity. Furthermore, the optimum power allocation strategy in terms of minimizing the average BER is investigated, and simple analytical solutions are obtained. Simulation results demonstrate that the proposed RSDDCT scheme can achieve excellent performance over fading channels in the presence of unknown random MCFOs. It is also shown that the proposed optimum power allocation strategy offers substantial average BER performance improvement over the equal power allocation strategy.

The Node Arrangement Methodology of Wireless Sensor Networks for Long-Span Bridge Health Monitoring

Wireless sensor networks (WSNs), which are a promising technology for the implementation of long-span bridge health monitoring, have gained increasing attention from both the research community and actual users. The limited energy of sensor emphasizes the importance of performance optimization of WSNs. In this paper, a methodology and strategy of node arrangement are developed to improve the performance of WSN for long-span bridge health monitoring, including balancing energy consumption, increasing data capacity, and reducing deployment cost. A composite WSN organized by sensor nodes and relay nodes is introduced for structural health monitoring. The energy consumption model of the composite WSN is firstly presented. And then, the data acquisition efficiency (DAE) defined as data capacity per unit deployment cost is suggested to evaluate the performance of WSN. Subsequently, the node arrangement is divided into two phases of sensor node arrangement and relay node arrangement. An improved general genetic algorithm is proposed to configure sensor nodes, and a nonuniform node arrangement method is developed to distribute relay nodes. Based on the DAE, the theoretical formulae of nonuniform node arrangement are deduced. The process of two-phase node arrangement is also provided for practical bridge engineers.

On the Problem of Energy Balanced Relay Sensor Placement in Wireless Sensor Networks

Balanced energy depletion is an important way to prolong network lifetime for wireless sensor networks. Traditional algorithms mainly aim at maximizing network coverage rate with uniform sensor node distribution. However, wireless sensor network is characterized by many-to-one traffic pattern and multihop communication, which usually lead to the energy hole problem in the region around the sink node. In this paper, we investigate the problem of joint placement for both relays and sensors to eliminate energy hole. We first theoretically conclude that balanced energy depletion is achievable with rational designed deployment density for relay nodes. We then propose a novel relay deploying strategy as well as a data routing scheme to eliminate uneven energy depletion. Extensive simulations are presented to verify that our approach outperforms other schemes in terms of both network lifetime and unused energy ratio.

Enhancement of Lifetime using Duty Cycle and Network Coding in Wireless Sensor Networks

A fundamental challenge in the design of Wireless Sensor Network (WSN) is to enhance the network lifetime. The area around the Sink forms a bottleneck zone due to heavy traffic-flow, which limits the network lifetime in WSN. This work attempts to improve the energy efficiency of the bottleneck zone which leads to overall improvement of the network lifetime by considering a duty cycled WSN. An efficient communication paradigm has been adopted in the bottleneck zone by combining duty cycle and network coding. Studies carried out to estimate the upper bounds of the network lifetime by considering (i) duty cycle, (ii) network coding and (iii) combinations of duty cycle and network coding. The sensor nodes in the bottleneck zone are divided into two groups: simple relay sensors and network coder sensors. The relay nodes simply forward the received data, whereas, the network coder nodes transmit using the proposed network coding based algorithm. Energy efficiency of the bottleneck zone increases because more volume of data will be transmitted to the Sink with the same number of transmissions. This in-turn improves the overall lifetime of the network. Performance metrics, namely, packet delivery ratio and packet latency have also been investigated. A detailed theoretical analysis and simulation results have been provided to show the efficacy of the proposed approach.

Optimization of Wireless Sensor Network Lifetime by Deploying Relay Sensors

Topology control in wireless sensor networks helps to lower node energy consumption by reducing transmission power and by confining interference, collisions and consequently retransmissions. Decrease in node energy consumption implies probability of increasing network lifetime. In this paper, firs popular topology control algorithms are used for analyzing optimizing the power consumption in the wireless sensor network and later proposed a novel technique wherein power consumption is traded with additional relay nodes. Later relay nodes are introduced to make the network connected without increasing the transmit power. The relay node decreases the transmit power required while it may increase end-to-end delay. This paper designs and analyzes an algorithm that place an almost minimum number of relay nodes required to make network connected. Greedy version of this algorithm is implemented and demonstrated in simulation that it produces a high quality link. InterAvg, InterMax (no of nodes that can offer interference) MinMax, and MinTotal are used as metrics to analyze and compare various algorithms. Matlab and NS-2 are used for simulation purpose.

CBSXs are sensor relay proteins sensing adenosine-containing ligands in Arabidopsis

We recently determined that CBSX proteins, which have only one pair of cystathionine β-synthase (CBS) domains, directly regulate the activation of thioredoxins and thereby control cellular H2O2 levels and modulate both plant development and growth. The Arabidopsis genome contains six CBSXs, and these are localized to different subcellular compartments‑ CBSX1 and CBSX2 in the chloroplast, CBSX3 in the mitochondria, CBSX4 in the cytosol, and CBSX5 and CBSX6 in the endoplasmic reticulum. The CBSXs have been identified in prokaryotes and plants, but not in animals. The considerable differences in length and amino acid sequence between CBSX members may result in variations in protein structure and in their specificity to interact with ligands and/or target proteins. Here, we discuss the possibility that the CBSXs are novel sensor relay proteins that use adenosine-containing molecules as a ligand.

Chernoff information path loss in wireless relay sensor networks

The author studies wireless relay sensor networks (WRSNs) with randomly deployed sensors for detection of a phenomenon-of-interest (POI). The existing literature in this area has two main drawbacks. Firstly, little has been done to understand whether it is beneficial to relay in WRSNs and what would be the most suitable relaying mechanism such as decode-and-forward (DF) or amplify-and-forward (AF). Secondly, oversimplification in sensing and communication channel models is routinely enforced as a result of the dimensionality and complexity of the ‘whole-network’ analytical setting used in the existing works. To alleviate the aforementioned constraints, the author adopts a ‘per-path’ approach by looking into one typical information pipeline connecting the POI to the destination through either single-hop (SH) or multi-hop (MH). The author investigates the corresponding Chernoff information path loss (CIPL) as the sensor attempts to send 1-bit information about the POI to the remote data sink. The CIPL quantifies the detection reliability against the distance of separation between the original sensor and the data sink, which parallels the classic concept of power path loss (PPL) in wireless propagation channels. The notion of CIPL would provide useful insight on the problems of when and how to relay in WRSNs.

MAC aggregation protocols resilient to DoS attacks

In smart grid, sensor measurements are often sent to a control node over a hop–by–hop network of sensors themselves. To prevent en route accidental and malicious data corruption, each message is authenticated with a MAC, keyed with a symmetric key known to the generating sensor and the control node. MACs represent a significant overhead: a typical 128–bit MAC may often authenticate a 10–bit temperature reading. To mitigate these overheads, MAC aggregation methods were proposed. However, previously proposed MAC aggregation schemes are not resilient to Denial–of–Service (DoS) attacks, where a rogue node or a man–in–the–middle attacker can easily disrupt the entire set of MACs, and hence prevent using any of the transmitted data. In this work we propose a new way of MAC aggregation, which will allow the relay sensors to greatly reduce transmission overhead due to MACs, while achieving full unforgeability, and, simultaneously, much stronger resilience to DoS attacks.

Gallery: A Self-healing Topology Model for Pervasive Sensor Networks

Pervasive Sensor Network(PSN) is identified as rapid dynamic network. PSN environment is viable only through Sensor networks. Fault-tolerance is expected high when handling speedy movements of sensor nodes. Henceforth, we propose a novel self-healing topology named Gallery; a placement model for Pervasive WSNs with dynamic topology control functions. The topology model ensures the localization of sensor nodes and guarantees the scalability by increasing its tracks and slices. The 2D and 3D deployment methods are Gallery is discussed. A wait-n-relay method is introduced for mobility nodes. An informal clustering of nodes within a region is identified as track region. The careful design of track region and relevant parameters are done. A covering map of mobility enabled relay sensor is calculated. The simulation is done with omnetpp simulator. Self-healing is promising by exact data aggregation by relay sensor if an desirable event raised within the region of interest.

Received signal strength in large-scale wireless relay sensor network: a stochastic ray approach

The authors consider a point percolation lattice representation of a large-scale wireless relay sensor network (WRSN) deployed in a cluttered environment. Each relay sensor corresponds to a grid point in the random lattice and the signal sent by the source is modelled as an ensemble of photons that spread in the space, which may 'hit' other sensors and are 'scattered' around. At each hit, the relay node forwards the received signal to its nearest neighbour through direction-selective relaying.

Relay node placement based on balancing power consumption in wireless sensor networks

To alleviate the traffic burden of sensor nodes and extend the network lifetime in wireless sensor networks, one approach is to deploy a large number of low-cost micro-relay nodes for routing data. The question is how to deploy a minimum number of relay nodes in the sensing field with network lifetime constraint. If relay nodes are uniformly placed, the issue of uneven power consumption arises as relay nodes closer to the sink are required to relay more data and thus will deplete their energy more quickly. Here, the authors study the relay node deployment problem under the assumption that the relay node has the same energy supply as the sensor node. Based on balancing power consumption among all sensor nodes and relay nodes, the authors deduce a relay node density function according to which relay nodes are placed in the sensing field. Simulation results show that the approach can achieve high energy utilisation and the network lifetime is significantly extended compared with uniformly placing relay nodes.

Classifying Sensors Depending on their IDs to Reduce Power Consumption in Wireless Sensor Networks

Wireless sensor networks produce a large amount of data that needs to be processed, delivered, and assessed according to the application objectives. Cluster-based is an effective architecture for data-gathering in wireless sensor networks. Clustering provides an effective way for prolonging the lifetime of a wireless sensor network. Current clustering algorithms usually utilize two techniques, selecting cluster heads with more residual energy and rotating cluster heads periodically, in order to distribute the energy consumption among nodes in each cluster and extend the network lifetime. Clustering sensors are divided into groups, so that sensors will communicate information only to cluster heads and then the cluster heads will communicate the aggregated information to the processing center, and this may save energy. In this paper we show Two Relay Sensor Algorithm (TRSA), which divide wireless Sensor Network (WSN) into unequaled clusters, showing that it can effectively save power for maximizing the life time of the network. Simulation results show that the proposed unequal clustering mechanism (TRSA) balances the energy consumption among all sensor nodes and achieves an obvious improvement on the network lifetime.

Performance Improvement of Binary Sensor-Based Statistical Space-Time Block Code Cooperative Diversity Using Limited Feedback

The statistical cooperative diversity, based on space-time block codes (statistical STBC cooperative diversity) is proposed for binary sensors by several authors. Since Alamouti’s code is the only orthogonal code which achieves full diversity and full rate for two sensors, it is used in their works, and their achievable diversity order is 2. Instead of using Alamouti’s code, we use extended cooperative space-time block coding (ECBSTBC) which achieves full diversity which is shown analytically and full rate for an arbitrary number of sensors if a limited feedback is available at the active sensors. Another method to increase diversity in cooperative communications is sensor (relay) selection. However, the sensor selection method may lead to the selection of the same (near) sensor for transmission over a long period causing the energy hole problem in sensor networks. The ECBSTBC which utilizes every sensor in sight thus distributes the energy consumption among active sensors and alleviates the energy hole problem. In addition, it can be shown with detailed simulations that the ECBSTBC outperforms both the statistical STBC cooperative diversity and the sensor selection schemes.