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Underwater wireless sensor networks (UWSNs) will pave the way for a new era of underwater monitoring and actuation applications. The envisioned landscape of UWSN applications will help us learn more about our oceans, as well as about what lies beneath them. They are expected to change the current reality where no more than 5% of the volume of the oceans has been observed by humans. However, to enable large deployments of UWSNs, networking solutions toward efficient and reliable underwater data collection need to be investigated and proposed. In this context, the use of topology control algorithms for a suit-able, autonomous, and on-the-fly organization of the UWSN topology might mitigate the undesired effects of underwater wireless communications and consequently improve the performance of networking services and protocols designed for UWSNs. This article presents and discusses the intrinsic properties, potentials, and current research challenges of topology control in underwater sensor networks. We propose to classify topology control algorithms based on the principal methodology used to change the network topology. They can be categorized in three major groups: power control, wireless interface mode management, and mobility assisted-based techniques. Using the proposed classification, we survey the current state of the art and present an in-depth discussion of topology control solutions designed for UWSNs. [ABSTRACT FROM AUTHOR]

In the area of wireless sensor networks the network is composed of a significant number of nodes deployed in an extensive area in which not all nodes are directly connected. The sensor nodes are generally unattended after their deployment in hazardous, hostile or remote areas. But the thing is that ,"how nodes share the channel" and "how it will work at low energy" are the two main design goal. Contention-based vs. Scheduled-based protocols are used to avoid above problems. In this paper, we present the challenges in the design of the energy efficient protocols and for the wireless sensor network. We describe several Contention-based and Scheduledbased protocols for the WSNs emphasizing their strength and weakness wherever possible. At the end, we discuss the future research directions in the MAC protocol design. [ABSTRACT FROM AUTHOR]

Underwater sensor networks have enabled a new era in scientific and industrial underwater monitoring and exploration applications. However, these networks are energy-constrained and, more problematically, energy-hungry, as a consequence of the use of underwater acoustic links. In this work, we thoroughly review potential techniques for greening underwater sensor networks. In a top-down approach, we discuss the principal design and challenges of the appealing highlighted techniques. We also exemplify their use by surveying recent proposals in underwater sensor networks. Finally, we describe potential future research directions for energy conservation in underwater networks. [ABSTRACT FROM PUBLISHER]

Wireless link correlation has shown significant impact on the performance of various sensor network protocols. Many works have been devoted to exploiting link correlation for protocol improvements. However, the effectiveness of these designs heavily relies on the accuracy of link correlation measurement. In this paper, we investigate state-of-the-art link correlation measurement and analyze the limitations of existing works. We then propose a novel lightweight and accurate link correlation estimation (LACE) approach based on the reasoning of link correlation formation. LACE combines both long-term and short-term link behaviors for link correlation estimation. We implement LACE as a stand-alone interface in TinyOS and incorporate it into both routing and flooding protocols. Simulation and testbed results show that LACE: (1) achieves more accurate and lightweight link correlation measurements than the state-of-the-art work; and (2) greatly improves the performance of protocols exploiting link correlation. [ABSTRACT FROM AUTHOR]

Abstract: The growing interest in applications of Wireless Multimedia Sensor Networks (WMSNs) imposes new challenges on congestion control protocols in such networks. In this paper, we propose a new content-aware cross layer WMSN Congestion Control Protocol (WCCP) by considering the characteristics of multimedia content. WCCP employs a Source Congestion Avoidance Protocol (SCAP) in the source nodes, and a Receiver Congestion Control Protocol (RCCP) in the intermediate nodes. SCAP uses Group of Picture (GOP) size prediction to detect congestion in the network, and avoids congestion by adjusting the sending rate of source nodes and distribution of the departing packets from the source nodes. In addition, RCCP monitors the queue length of the intermediate nodes to detect congestion in both monitoring and event-driven traffics. Moreover, to improve the received video quality in base stations, WCCP keeps the I-frames and ignores the other less important frame types of compressed video, in the congestion situations. The proposed WCCP protocol is evaluated through simulations based on various performance metrics such as packet loss rate, frame loss rate, Peak Signal-to-Noise Ratio (PSNR), end-to-end delay, throughput, and energy consumption. The results show that WCCP significantly improves the network performance and the quality of received video in the sink nodes, and outperforms the existing state-of-the-art congestion control protocols. [Copyright &y& Elsevier]

Due to the potentials in promoting the driving safety and easing the traffic congestion, vehicular networks, especially vehicle-to-vehicle (V2V) communications, have recently been receiving much attention. The data dissemination protocol for V2V applications should not only provide end-to-end transmissions with low error probability and high throughput but also offer antieavesdropping capabilities. To achieve this goal, we in this paper propose a secrecy-enhanced relaying protocol for vehicular environments. Based on the network topology and the velocity of the moving vehicles, the proposed scheme first generates the relay candidate set, from which a single relay is then selected opportunistically to assist the source. By using the superposition coding strategy, the selected relay jointly sends the source message and the artificial interference to enable secure communications. We derive the tight closed-form expressions for the upper and lower bounds of the secrecy outage probability, based on which we analyze the diversity order of the system. The method to generate the interference signal is introduced, and the choice of superposition weight factor is also given. The analytical and simulation results show that the proposed relay-aided protocol yields a better performance than the competing alternatives in terms of both the secrecy performance and the implementation complexity. [ABSTRACT FROM AUTHOR]

Time-based localization approaches attract a lot of interest due to their high accuracy and potentially low cost for wireless sensor networks (WSNs). However, time-based localization is tightly coupled with clock synchronization. Thus, the reliability of timestamps in time-based localization becomes an important yet challenging task to deal with. In this paper, we propose robust time-based localization strategies to locate a target node with the help of anchors (nodes with known positions) in asynchronous networks. Two kinds of asynchronous networks are considered: one only with clock offsets, labeled quasi-synchronous networks, whereas the other with not only clock offsets but also clock skews, labeled fully asynchronous networks. A novel ranging protocol is developed for both networks, namely asymmetric trip ranging (ATR), to reduce the communication load and explore the broadcast property of WSNs. Regardless of the reliability of the timestamp report from the target node, closed-form least-squares (LS) estimators are derived to accurately estimate the target node position. As a result, we counter the uncertainties caused by the target node by ignoring the timestamps from this node. Furthermore, in order to simplify the estimator in fully asynchronous networks, localization and synchronization are decoupled. A simple yet efficient method is proposed to first Calibrate the Clock Skews of the anchors, and then Estimate the Node Position (CCS-ENP). Finally, Cramér-Rao bounds (CRBs) and simulation results corroborate the efficiency of our localization schemes. [ABSTRACT FROM AUTHOR]

Abstract: Mutual entity authentication plays an important role in securing wireless sensor networks. In this paper, we propose a computationally efficient authentication framework, based on a well-studied problem—learning parity with noise (LPN). This kind of LPN-based authentication approaches only involve simplest bit-operations, which makes them suitable for resource-restrained sensor nodes. The proposed HB-hybrid framework introduces a new noise mode to prevent a general man-in-the-middle attack against previous LPN-based protocols, presents a gentle approach to securely combine several HB-like one-way authentication protocols and extends to mutual authentication which effectively thwarts the reflection attack. It spawns three specific protocols with different trade-offs between communication overload and memory cost. We extensively analyze their performance and security properties. Moreover, some optimization mechanisms on communication costs are given and the application scenarios for different wireless sensor networks are discussed at length. [ABSTRACT FROM AUTHOR]

In this paper, we develop an analytical energy efficiency model using dual switched branch diversity receiver in wireless sensor networks in fading environments. To adapt energy efficiency of sensor node to channel variations, the optimal packet length at the data link layer is considered. Within this model, the energy efficiency can be effectively improved for switch-and-stay combiner (SSC) receiver with optimal switching threshold. Moreover, to improve energy efficiency, we use error control of Bose-Chaudhuri-Hochquengh (BCH) coding for SSC-BPSK receiver node compared to one of non-diversity NCFSK receiver of sensor node. The results show that the BCH code for channel coding can improve the energy efficiency significantly for long link distance and various values of high energy consumptions over Rayleigh fading channel. [ABSTRACT FROM AUTHOR]

Flood is a communication primitive that can be used by the base station of a sensor network to send a copy of a message to every sensor in the network. When a sensor receives a flood message, the sensor needs to check whether it has received this message for the first time and so this message is fresh, or it has received the same message earlier and so the message is redundant. In this paper, we discuss a family of four flood sequencing protocols that use sequence numbers to distinguish between fresh and redundant flood messages. These four protocols are: a sequencing free protocol, a linear sequencing protocol, a circular sequencing protocol, and a differentiated sequencing protocol. We analyze the self-stabilization properties of these four flood sequencing protocols. We also compare the performance of these flood sequencing protocols, using simulation, over various settings of sensor networks. We conclude that the differentiated sequencing protocol has better stabilization property and provides better performance than those of the other three protocols. [ABSTRACT FROM AUTHOR]

Wireless multimedia sensor networks (WMSNs) are expected to support multimedia services such as delivery of video and audio streams. However, due to the relatively stringent quality-of-service (QoS) requirements of multimedia services (e.g., high transmission rates and timely delivery) and the limited wireless resources, it is possible that not all the potential sensor nodes can be admitted into the network. Thus, node admission is essential for WMSNs, which is the target of this paper. Specifically, we aim at the node admission and its interaction with power allocation and link scheduling. A cross-layer design is presented as a two-stage optimization problem, where at the first stage the number of admitted sensor nodes is maximized, and at the second stage the network lifetime is maximized. Interestingly, it is proved that the two-stage optimization problem can be converted to a one-stage optimization problem with a more compact and concise mathematical form. Numerical results demonstrate the effectiveness of the two-stage and one-stage optimization frameworks. [ABSTRACT FROM AUTHOR]

We present in this paper an investigation of a special class of wireless sensor networks for monitoring critical infrastructures that may extend for hundreds of miles in distances. Such networks are fundamentally different from traditional sensor networks in that the sensor nodes in this class of networks are deployed along narrowly elongated geographical areas and form a chain-type topology. Based on careful analysis of existing sensor network architectures, we first demonstrate the need to develop new architecture and networking protocols to match the unique topology of chain-type sensor networks. We then propose hierarchical network architecture that consists of clusters of sensor nodes to enable the chain-type sensor networks to be scalable to cover typically long range infrastructures with tolerable delay in network-wide data collection. To maintain energy efficient operations and maximize the lifetime for such a chain-type sensor network, we devise a smart strategy for the deployment of cluster heads. Protocols for network initialization and seamless operations of the chain-type sensor networks are also developed to match the proposed hierarchical architecture and cluster head deployment strategy. Simulations have been carried out to verify the performance of the hierarchical architecture, the smart node deployment strategy, and the corresponding network initialization and operation protocols. [ABSTRACT FROM AUTHOR]

Volunteer forwarding, as an emerging routing idea for large scale, location-aware wireless sensor networks, has recently received significant attention. However, several critical research issues raised by volunteer forwarding, including communication collisions, communication voids, and time-critical routing, have not been well addressed by the existing work. In this paper, we propose a priority-based stateless geo-routing (PSGR) protocol that addresses these issues. Based on PSGR, sensor nodes are able to locally determine their priority to serve as the next relay node using dynamically estimated network density. This effectively suppresses potential communication collisions without prolonging routing delays. PSGR also overcomes the communication void problem using two alternative stateless schemes, rebroadcast and bypass. Meanwhile, PSGR supports routing of time-critical packets with different deadline requirements at no extra communication cost. Additionally, we analyze the energy consumption and the delivery rate of PSGR as functions of the transmission range. Finally, an extensive performance evaluation has been conducted to compare PSGR with competing protocols, including GeRaf, IGF, GPSR, flooding, and MSPEED. Simulation results show that PSGR exhibits superior performance in terms of energy consumption, routing latency, and delivery rate, and soundly outperforms all of the compared protocols. [ABSTRACT FROM AUTHOR]

In this paper we present an energy-efficient cross layer protocol for providing application specific reservations in wireless senor networks called the "Unified Clustering and Communication Protocol" (UCCP). Our modular cross layered framework satisfies three wireless sensor network requirements, namely, the QoS requirement of heterogeneous applications, energy aware clustering and data forwarding by relay sensor nodes. Our unified design approach is motivated by providing an integrated and viable solution for self organization and end-to-end communication is wireless sensor networks. Dynamic QoS based reservation guarantees are provided using a reservation-based TDMA approach. Our novel energy-efficient clustering approach employs a multi-objective optimization technique based on OR (operations research) practices. We adopt a simple hierarchy in which relay nodes forward data messages from cluster head to the sink, thus eliminating the overheads needed to maintain a routing protocol. Simulation results demonstrate that UCCP provides an energy-efficient and scalable solution to meet the application specific QoS demands in resource constrained sensor nodes. [ABSTRACT FROM AUTHOR]

Abstract: In this paper we focus on the problems of high latency and low throughput arising from the periodic operation of MAC protocols for wireless sensor networks. In order to meet both design criteria we propose an energy-efficient, low delay, fast-periodic MAC algorithm, namely FP-MAC, that is exclusively designed for 802.15.4-like networks utilizing in full the standard’s physical layer. Our proposal relies on the short periodic communication operation of the nodes comprising the WSN. This is achieved by decreasing the actions that a node needs to perform at the start of every communication period and by incorporating a variable radio-on operation. Moreover, the algorithm introduces differences in nodes’ scheduling to further reduce delay. Local synchronization and the crucial task of determining the proper timing for transmission and reception of data is achieved through the periodic broadcast of special synchronization frames at the beginning of each on-period. FP-MAC is evaluated and compared to S-MAC and T-MAC through extensive simulations, showing a significant improvement in terms of low energy consumption and average MAC delay. [Copyright &y& Elsevier]

Abstract: The diversity of applications and typically scarce node resources set very tight constraints to Wireless Sensor Networks (WSN). It is not possible to fulfill all requirements with a general purpose WSN, for which reason the rapid development of application specific WSNs is preferred. We present a new framework called WIreless SEnsor NEtwork Simulator (WISENES) for the design, simulation, and evaluation of WSNs. The target WSN is designed in Specification and Description Language (SDL), simulated in WISENES, and implemented on target platform either through automatic code generation or manually. The high-level WSN model is back-annotated with the measured values from a real platform. In this way, very accurate WSN simulations can be performed with a rapid design cycle. WISENES itself has been verified with TUTWSN (Tampere University of Technology Wireless Sensor Network) and ZigBee protocols. The MAC protocol of ZigBee was designed in two weeks from scratch by one designer, which shows the effectiveness of WISENES. For accuracy comparison, the results show 6.7% difference between the modeled and measured TUTWSN prototype power consumption. WISENES hastens the evaluation of new protocol and application configurations, especially for the large scale and long-term WSN deployments. [Copyright &y& Elsevier]

In this paper, we study the impact of collisions and interference on a neighbor discovery process in the context of multi-hop wireless networks. We consider three models in which interference and collisions are handled in very different ways. From an ideal channel where simultaneous transmissions do not interfere, we derive an alternate channel where simultaneous transmissions are considered two-by-two under the form of collisions, to finally reach a more realistic channel where simultaneous transmissions are handled under the form of shot-noise interference. In these models, we analytically compute the link probability success between two neighbors as well as the expected number of nodes that correctly receive a Hello packet. Using this analysis, we show that if the neighbor discovery process is asymptotically equivalent in the three models, it offers very different behaviors locally in time. In particular, the scalability of the process is not the same depending on the way interference is handled. Finally, we apply our results to the dimensioning of a Hello protocol parameters. We propose a method to adapt the protocol parameters to meet application constraints on the neighbor discovery process and to minimize the protocol energy consumption. [ABSTRACT FROM AUTHOR]

IEEE 802.15.4 is the global standard protocol designed for low-power and low-rate wireless personal area networks. When applied to sensor networks, extra care should be taken due to their requirements for multihop communication with minimum energy consumption. In this article we first discuss potential problems with the energy consumption in sensor networks using IEEE 802.15.4. Then six representative categories of algorithms are presented. The algorithms reside in between the MAC and a network layer. All operations of the MAC are performed through the standard interfaces of IEEE 802.15.4 without altering the standard protocol. The energy consumption and latency of the algorithms are evaluated by analysis and experiments, and the feasibility of real implementations is also discussed. [ABSTRACT FROM AUTHOR]

Many wireless sensor network (WSN) applications demand secure communications. The random key predistribution (RKP) protocol has been well accepted in achieving secure communications in WSNs. A host of key management protocols have been proposed based on the RKP protocol. However, due to the randomness in key distribution and strong constraint in key path construction, the RKP-based protocols can only be applied in highly dense networks, which are not always feasible in practice. In this paper, we propose a methodology called network decoupling to address this problem. With this methodology, a WSN is decoupled into a logical keysha ring network and a physical neighborhood network, which significantly releases the constraint in key path construction of the RKP protocol. We design two new key management protocols, that is, RKP-DE and RKP-DEA, as well as a set of link and path dependency elimination rules in decoupled sensor networks. Our analytical and simulation data demonstrate the performance enhancement of our solutions from the perspective of connectivity and resilience and its applicability in nonhighly dense sensor networks. [ABSTRACT FROM AUTHOR]

Routing in wireless sensor networks is a demanding task. This demand has led to a number of routing protocols which efficiently utilize the limited resources available at the sensor nodes. All these protocols typically find the minimum energy path. In this paper we take a view that, always using the minimum energy path deprives the nodes energy quickly and the time taken to determine an alternate path increases. Multipath routing schemes distribute traffic among multiple paths instead of routing all the traffic along a single path. Two key questions that arise in multipath routing are how many paths are needed and how to select these paths. Clearly, the number and the quality of the paths selected dictate the performance of a multipath routing scheme. We propose an energy efficient adaptive multipath routing technique which utilizes multiple paths between source and the sink, adaptive because they have low routing overhead. This protocol is intended to provide a reliable transmission environment with low energy consumption, by efficiently utilizing the energy availability and the received signal strength of the nodes to identify multiple routes to the destination. Simulation results show that the energy efficient adaptive multipath routing scheme achieves much higher performance than the classical routing protocols, even in the presence of high node density and overcomes simultaneous packet forwarding. [ABSTRACT FROM AUTHOR]

With recent developments in ad hoc networks and sensor networks, random-access protocol without feedback is a technique that deserves a closer look. This paper is based on Massey's model on random-access channel without feedback. A central concept of this model is the idea of protocol sequences. For these sequences, it is desirable that their cross correlation should be as low as possible and that the length of their period should not be too long, even if there is a large number of active users. Another useful feature is to be able to support multirate communication. Based on these considerations, a new family of protocol sequences is proposed in this paper. These new protocol sequences are built on the concept of prime sequences. It is shown that these sequences possess properties that make them suitable candidates for designing random access protocols for certain ad hoc or sensor networks. [ABSTRACT FROM AUTHOR]

Impulse-based ultrawideband (I-UWB) is an attractive radio technology for large ad hoc and sensor networks due to its robustness to multipath effects, subcentimeter ranging ability, simple hardware, and low radiated power. Large distributed networks, such as ad hoc and sensor networks, often implement distributed medium access control (MAC) protocols based on carrier sense multiple access (CSMA). In CSMA, narrowband systems check for medium activity before transmitting by checking for in-band energy around a carrier frequency. I-UWB systems lack a carrier, and the narrow pulses, low radiated power, harsh channel conditions, and strict Federal Communications Commission power limits present challenges in detecting medium activity. We propose a pulse sensor for I-UWB systems that overcomes the challenges of quickly, reliably, and efficiently identifying medium activity. The pulse sensor enables distributed MAC protocols for I-UWB radios that are analogous to CSMA for narrowband radios. Simulations show that the proposed pulse sensor architecture is practical for I-UWE radios. [ABSTRACT FROM AUTHOR]

After around a decade of active research on wireless sensor networks, recent standards released are stimulating the development of commercial products. One of these standards is ZigBee. This article highlights some of the lessons from the field that went into the standard. It also describes the ecosystem emerging around Zigbee, and the enabling trends in that ecosystem. New areas of activity in the ZigBee standards body are highlighted as well. [ABSTRACT FROM AUTHOR]

Chapter 4 of the book "Foundations and Trends in Networking" is presented. It explores the vast opportunities of wireless and sensor network for applications of network coding. It highlights some sensor network applications in networking and discusses the challenges and open problems of wireless and sensor networks.

Many research activities on Wireless Sensor Networks (WSNs) need detailed performance statistics about protocols, systems, and applications; however, current simulation tools and testbeds lack mechanisms to report these statistics realistically and conveniently. To address this need, we have developed a WSN emulator, VMNet. VMNet emulates networked sensor nodes at the level of CPU clock cycles and executes the binary code of real applications directly. It emulates the radio channel with loss and noise as well as emulates the peripherals in sufficient detail. Moreover, VMNet takes parameter values from the real world and logs detailed runtime information of emulated nodes. Consequently, the application performance, both in response time and in power consumption, is reported realistically in VMNet, as demonstrated by our comparison studies with real sensor networks. [ABSTRACT FROM AUTHOR]

Conventional wireless sensor networks rely mostly on simple scalar data (such as temperature or humidity) and specialize in single-purpose applications. Taking a fundamental departure, in this article we motivate information-rich wireless video sensor networks that emulate the compound eyes found in certain arthropods. Although constrained by scarce resources, sensor nodes can only serve extremely low-resolution video streams; the availability of vast amount of such streams due to deployment redundance can suffice for the need of information hungry applications. Unfortunately, the unique characteristics of wireless video sensor networks will introduce novel uncertainty-driven challenges in the information-intensive and yet resource-constrained environment. Correspondingly, we describe key research problems in the areas of networking, security, sensor design, and video-data analysis. [ABSTRACT FROM AUTHOR]

Uniformly random or Poisson distributions are widely accepted models for the location of the nodes in wireless sensor networks if nodes are deployed in large quantities and there is little control over where they are dropped, On the other hand, by placing nodes in regular topologies, we expect benefits both in coverage and efficiency of communication. We describe and analyze a basic localized algorithm and three modifications for topology control that provide a tradeoff between performance and deployment cost. The objective is to regularize the topology for improved energy efficiency. The basic algorithm produces quasiregular networks, which only use nodes as sentries and relays that are approximately evenly spaced, thereby emulating a regular grid topology, It is shown that quasiregular networks have a significant energy and lifetime advantage compared with purely random networks. We consider two specific types of quasiregular networks: the ones that are based on a Gaussian deviation about an ideal grid point (type A), and the ones that consist of a subset of nodes taken from a Poisson point process (type B). We show that the two types are equivalent for a certain density of the Poisson point process and, in particular, that in both cases the deviation from the ideal regular grid follows a Rayleigh distribution, whereas the distance between nearest neighbors is Ricean. [ABSTRACT FROM AUTHOR]

Wireless sensor networks are proposed to deliver in situ observations at low cost over long periods of time. Among numerous challenges faced while designing WSNs and protocols, maintaining connectivity and maximizing the network lifetime stand out as critical considerations. Mobile platforms equipped with communication devices can be leveraged to overcome these two problems. In this article existing proposals that use mobility in WSNs are summarized. Furthermore, a new approach to compute mobile platform trajectories is introduced. These solutions are also compared considering various metrics and design goals. [ABSTRACT FROM AUTHOR]

A framework is developed for analyzing capacity gains from user cooperation in slow-fading wireless networks when the number of nodes (network size) is large. The framework is illustrated for the case of a simple multipath-rich Rayleigh-fading channel model. Both unicasting (one source and one destination) and multicasting (one source and several destinations) scenarios are considered. We introduce a meaningful notion of Shannon capacity for such systems, evaluate this capacity as a function of signal-to-noise ratio (SNR), and develop a simple two-phase cooperative network protocol that achieves it. We observe that the resulting capacity is the same for both unicasting and multicasting, but show that the network size required to achieve any target error probability is smaller for unicasting than for multicasting. Finally, we introduce the notion of a network ‘scaling exponent’ to quantify the rate of decay of error probability with network size as a function of the targeted fraction of the capacity. This exponent provides additional insights to system designers by enabling a finer grain comparison of candidate cooperative transmission protocols in even moderately sized networks. [ABSTRACT FROM AUTHOR]

The throughput of wireless networks is known to scale poorly when the number of users grows. The rate at which an arbitrary pair of nodes can communicate must decrease to zero as the number of users tends to infinity, under various assumptions. One of them is the requirement that the network is fully connected: the computed rate must hold for any pair of nodes of the network. We show that this requirement can be responsible for the lack of throughput scalability. We consider a two-dimensional (2-D) network of extending area with only one active source-destination pair at any given time, and all remaining nodes acting only as possible relays. Allowing an arbitrary small fraction of the nodes to be disconnected, we show that the per-node throughput remains constant as the network size increases. As a converse bound, we show that communications occurring at a fixed nonzero rate imply a fraction of the nodes to be disconnected. Our results are of information theoretic flavor, as they hold without assumptions on the communication strategies employed by the network nodes. [ABSTRACT FROM AUTHOR]

The problem of determining what links can be simultaneously activated in a wireless network such that a signal-to-interference-and-noise (SINR) constraint is satisfied at all receivers is considered. The term ‘feasible matching’ is introduced to describe a set of (transmitter, receiver) pairs for which there exists some set of transmit powers which can simultaneously meet the SINR requirements at the receivers. Given disjoint equally sized sets of transmitters and receivers, it is shown that when the SINR requirement at the receivers is greater than 1, no more than one feasible matching between the transmitters and the receivers exists. Sufficient conditions are provided under which certain broad classes of matchings in a network are guaranteed to be feasible; for example all matchings involving k or fewer links. The application of these results to ad hoc wireless networks and to scheduling is discussed. [ABSTRACT FROM AUTHOR]

We consider a wireless network where a remote source sends information to one of two colocated users, and where the second user can serve as a relay. The source's transmission is subjected to quasi-static flat Rayleigh fading, while the transmission of the relay experiences a fixed amplitude gain with a uniform random phase, capturing its close proximity to the destination. All communications share the same time/bandwith resources, and perfect channel state information is known only to the receivers. We propose relaying protocols which are based on Wyner-Ziv quantization at the relay, and demonstrate their high efficiency (in terms of expected throughput) with respect to previously reported relaying schemes based on amplify-and-forward and decode-and-forward. A salient feature of these protocols is that the relay need not know the actual fading gain experienced by the destination in order to perform the quantization. We also consider a hybrid amplify-quantize-decode-and-forward scheme which exhibits superior performance. [ABSTRACT FROM AUTHOR]

In this paper, a novel multihop virtual multiple-input-multiple-output (MIMO) communication protocol is proposed by the cross-layer design to jointly improve the energy efficiency, reliability, and end-to-end (ETE) QoS provisioning in wireless sensor network (WSN). In the protocol, the traditional low-energy adaptive clustering hierarchy protocol is extended by incorporating the cooperative MIMO communication, multihop routing, and hop-by-hop recovery schemes. Based on the protocol, the overall energy consumption per packet transmission is modeled and the optimal set of transmission parameters is found. Then, the issues of ETE QoS provisioning of the protocol are considered. The ETE latency and throughput of the protocol are modeled in terms of the bit-error-rate (BER) performance of each link. Then, a nonlinear constrained programming model is developed to find the optimal BER performance of each link to meet the ETE QoS requirements with a minimum energy consumption. The particle swarm optimization (PSO) algorithm is employed to solve the problem. Simulation results show the effectiveness of the proposed protocol in energy saving and QoS provisioning. [ABSTRACT FROM AUTHOR]

Wireless sensor networks are appealing to researchers due to their wide range of application potential in areas such as target detection and tracking, environmental monitoring, industrial process monitoring, and tactical systems. However, low sensing ranges result in dense net- works and thus it becomes necessary to achieve an efficient medium-access protocol subject to power constraints. Various medium-access control (MAC) protocols with different objectives have been proposed for wireless sensor networks. In this article, we first outline the sensor network properties that are crucial for the design of MAC layer protocols. Then, we describe several MAC protocols proposed for sensor networks, emphasizing their strengths and weaknesses. Finally, we point out open research issues with regard to MAC layer design. [ABSTRACT FROM AUTHOR]

In recent years, sensor networks have transitioned from being objects of academic research interest to a technology that is frequently being deployed in real-life applications and rapidly being commercialized. However, energy consumption continues to remain a barrier challenge in many sensor network applications that require long lifetimes. Battery-operated sensor nodes have limited energy storage capability due to small form-factors, or operate in environments that rule out frequent energy replenishment, resulting in a mismatch between the available energy budget for system operation and the required energy budget to obtain desired lifetimes. This article surveys several techniques that show promise in addressing and alleviating this energy consumption challenge. In addition to describing recent advances in energy-aware platforms for information processing and communication protocols for sensor collaboration, the article also looks at emerging, hitherto largely unexplored techniques, such as the use of environmental energy harvesting and the optimization of the energy consumed during sensing. [ABSTRACT FROM AUTHOR]

The dynamic nature of ad hoc networks makes system design a challenging task. Mobile ad hoc networks suffer from severe performance problems due to the shared, interference-prone, and unreliable medium. Routes can be unstable due to mobility and energy can be a limiting factor for typical devices such as PDAs, mobile phones, and sensor nodes. In such environments cross-layer architectures are a promising new approach, as they can adapt protocol behavior to changing networking conditions. This article introduces CrossTalk, a cross-layer architecture that aims at achieving global objectives with local behavior. It further compares CrossTalk with other cross-layer architectures proposed. Finally, it analyzes the quality of the information provided by the architecture and presents a reference application to demonstrate the effectiveness of the general approach. [ABSTRACT FROM AUTHOR]

We present Geometric Broadcast for Heterogeneous Sensor Networks (GBS), a novel broadcasting protocol for heterogeneous wireless sensor and actor networks. While broadcasting is a very energy expensive protocol, it is also widely used as a building block for a variety of other network layer protocols. Therefore, reducing the energy consumption by optimizing broadcasting is a major improvement in heterogenous sensor networking. GBS is a distributed algorithm where nodes make local decisions on whether to transmit based on a geometric approach. GBS does not need any neighborhood information and imposes very low communication overhead. GBS is scalable to the change in network size, node type, node density and topology. Furthermore it accommodates seamlessly such network changes, including the presence of actors in heterogeneous sensor networks. Indeed, GBS takes advantage of actor nodes, and uses their resources when possible, thus reducing the energy consumption by sensor nodes. Through simulation evaluations, we show that GBS is very scalable and its performance is improved by the presence of actors. At the best of our knowledge, GBS is the first broadcast protocol designed specifically for heterogeneous sensor and actor networks. [ABSTRACT FROM AUTHOR]

Abstract: Geographic routing protocols base their forwarding decisions on the location of the current device, its neighbors, and the packets destination. Early proposed heuristic greedy routing algorithms might fail even if there is a path from source to destination. In recent years several recovery strategies have been proposed in order to overcome such greedy routing failures. Planar graph traversal was the first of those strategies that does not require packet duplication and memorizing past routing tasks. This article introduces a novel recovery strategy based on the idea of planar graph traversal but performing routing tasks along geographical clusters instead of individual nodes. The planar graph construction method discovered so far needs one-hop neighbor information only, but may produce disconnection even if there is a path from source to destination. However, simulation results show that the proposed algorithm is a good choice from a practical point of view, since disconnection does only concern sparse networks, while in dense network the proposed algorithm competes with existing solutions and even outperforms planar graph routing methods based on one-hop neighbor information. This paper finally gives an outline of further research directions which show that geographical clusters may be the key to solve some problems that come along with planar graph routing in wireless networks. [Copyright &y& Elsevier]

We present a new information dissemination protocol for wireless sensor networks. This protocol uses location information to reduce redundant transmissions, thereby saving energy. The sensor network is divided into virtual grids and each sensor node associates itself with a virtual grid based on its location. Sensor nodes within a virtual grid are classified as either gateway nodes or internal nodes. While gateway nodes are responsible for forwarding the data across virtual grids, internal nodes forward the data within a virtual grid. The proposed approach, termed location-aided flooding (LAF), achieves energy savings by reducing the redundant transmissions of the same packet by a node. We study the performance of LAF for different grid sizes and different node densities and compare it to other well-known methods. We show that LAF can save a significant amount of energy compared to prior methods. [ABSTRACT FROM AUTHOR]

Research on multi-path routing protocols to provide improved throughput and route resilience as compared with single-path routing has been explored in details in the context of wired networks. However, multi-path routing mechanisms have not been explored thoroughly in the domain of ad hoc networks. In this paper, we propose a new routing protocol which increases the network throughput. The protocol is a multi-path routing protocol with a load balance policy. The simulations show a significant improvement in terms of connection throughput and end-to-end delay, when compared to single-path routing. The second significant contribution of this paper is a theoretical analysis allowing to compare reactive single-path and multi-path routing with load balance mechanisms in ad hoc networks, in terms of overheads, traffic distribution and connection throughput. The results reveal that multi-path routing (using a load balance policy) provides better performance than reactive single-path routing in terms of congestion and connection throughput, provided that the average route length is smaller than certain upper bounds which are derived and depend on parameters specific to the network. These upper bounds are very crucial because they can be taken into account as constraints in the route discovery mechanism so that the multi-path routing protocol is guaranteed to lead to an increase performance than a simple single-path one. Also, our analysis provide some insight into choosing the right trade-off between increased overheads and better performance. We show in particular that for certain networks, a multi-path routing strategy is not worth considering. [Copyright &y& Elsevier]

Several localized routing protocols guarantee the delivery of the packets when the underlying network topology is a planar graph. Typically, relative neighborhood graph (RNG) or Gabriel graph (GG) is used as such planar structure. However, it is well-known that the spanning ratios of these two graphs are not bounded by any constant (even for uniform randomly distributed points). Bose et al. [11] recently developed a localized routing protocol that guarantees that the distance traveled by the packets is within a constant factor of the minimum if Delaunay triangulation of all wireless nodes is used, in addition, to guarantee the delivery of the packets. However, it is expensive to construct the Delaunay triangulation in a distributed manner. Given a set of wireless nodes, we model the network as a unit-disk graph (UDG), in which a link uv exists only if the distance uv is at most the maximum transmission range. In this paper, we present a novel localized networking protocol that constructs a planar 2.5-spanner of UDG, called the localized Delaunay triangulation (LDEL), as network topology. It contains all edges that are both in the unit-disk graph and the Delaunay triangulation of all nodes. The total communication cost of our networking protocol is O(n log n) bits, which is within a constant factor of the optimum to construct any structure in a distributed manner. Our experiments show that the delivery rates of some of the existing localized routing protocols are increased when localized Delaunay triangulation is used instead of several previously proposed topologies. Our simulations also show that the traveled distance of the packets is significantly less when the FACE routing algorithm is applied on LDEL, rather than applied on GG. [ABSTRACT FROM AUTHOR]

Recently, researchers and practitioners in wireless sensor networks (WSNs) are focusing on energy-oriented communication and computing considering next-generation smaller and tiny wireless devices. The tiny sensor-enabled devices will be used for the purpose of sensing, computing, and wireless communication. The hundreds/thousands of WSNs sensors are used to monitor specific activities and report events via wireless communication. The tiny sensor-enabled devices are powered by smaller batteries to work independently in distributed environments resulting in limited maximum lifetime of the network constituted by these devices. Considering the non-uniform distribution of sensor-enabled devices in the next-generation mobility centric WSNs environments, energy consumption is imbalanced among the different sensors in the overall network environments. Toward this end, in this paper, a cluster-oriented routing protocol termed as prediction-oriented distributed clustering (PODC) mechanism is proposed for WSNs focusing on non-uniform sensor distribution in the network. A network model is presented, while categorizing PODC mechanism in two activities including setting cluster of nodes and the activity in the steady state. Further cluster set up activity is described while categorizing in four subcategories. The proposed protocol is compared with individual sensor energy awareness and distributed networking mode of clustering (EADC) and scheduled sensor activity-based individual sensor energy awareness and distributed networking mode of clustering (SA-ADC). The metrics including the overall lifetime of the network and nodes individual energy consumption in realistic next-generation WSNs environments are considered in the experimental evaluation. The results attest the reduced energy consumption centric benefits of the proposed framework PODC as compared to the literature. Therefore, the framework will be more applicable for the smart product development in the next-generation WSNs environments. [ABSTRACT FROM AUTHOR]

The infeasible signal-to-interference ratio (SIR) region is a set of SIRs that are not supportable in a power-controlled wireless network. It was conjectured that this set is convex in networks constrained on total power. We disprove the conjecture and discuss how this result may impact optimal medium-access control policies. [ABSTRACT FROM AUTHOR]

Data collection is a fundamental function provided by wireless sensor networks. How to efficiently collect sensing data from all sensor nodes is critical to the performance of sensor networks. In this paper, we aim to understand the theoretical limits of data collection in a TDMA-based sensor network in terms of possible and achievable maximum capacity. Previously, the study of data collection capacity has concentrated on large-scale random networks. However, in most of the practical sensor applications, the sensor network is not uniformly deployed and the number of sensors may not be as huge as in theory. Therefore, it is necessary to study the capacity of data collection in an arbitrary network. In this paper, we first derive the upper and lower bounds for data collection capacity in arbitrary networks under protocol interference and disk graph models. We show that a simple BFS tree-based method can lead to order-optimal performance for any arbitrary sensor networks. We then study the capacity bounds of data collection under a general graph model, where two nearby nodes may be unable to communicate due to barriers or path fading, and discuss performance implications. Finally, we provide discussions on the design of data collection under a physical interference model or a Gaussian channel model. [ABSTRACT FROM AUTHOR]