Showing papers in "Wireless Networks in 2011"
TL;DR: This paper offers a survey of the concept of Wireless Body Area Networks, focusing on some applications with special interest in patient monitoring and the communication in a WBAN and its positioning between the different technologies.
Abstract: The increasing use of wireless networks and the constant miniaturization of electrical devices has empowered the development of Wireless Body Area Networks (WBANs). In these networks various sensors are attached on clothing or on the body or even implanted under the skin. The wireless nature of the network and the wide variety of sensors offer numerous new, practical and innovative applications to improve health care and the Quality of Life. The sensors of a WBAN measure for example the heartbeat, the body temperature or record a prolonged electrocardiogram. Using a WBAN, the patient experiences a greater physical mobility and is no longer compelled to stay in the hospital. This paper offers a survey of the concept of Wireless Body Area Networks. First, we focus on some applications with special interest in patient monitoring. Then the communication in a WBAN and its positioning between the different technologies is discussed. An overview of the current research on the physical layer, existing MAC and network protocols is given. Further, cross layer and quality of service is discussed. As WBANs are placed on the human body and often transport private data, security is also considered. An overview of current and past projects is given. Finally, the open research issues and challenges are pointed out.
1,077 citations
TL;DR: Since identity-based cryptography is employed in the scheme to generate private keys for pseudo identities, certificates are not required and thus transmission overhead can be significantly reduced, and thus message verification speed can be tremendously increased.
Abstract: In this paper, an efficient identity-based batch signature verification scheme is proposed for vehicular communications. With the proposed scheme, vehicles can verify a batch of signatures once instead of in a one-by-one manner. Hence the message verification speed can be tremendously increased. To identify invalid signatures in a batch of signatures, this paper adopts group testing technique, which can find the invalid signatures with few number of batch verifications. In addition, a trust authority in our scheme is capable of tracing a vehicle's real identity from its pseudo identity, and therefore conditional privacy preserving can also be achieved. Moreover, since identity-based cryptography is employed in the scheme to generate private keys for pseudo identities, certificates are not required and thus transmission overhead can be significantly reduced.
128 citations
TL;DR: This work proposes two new improvements to the problem of scheduling in wireless sensor networks for the purposes of aggregation convergecast, starting with a new lower bound on the schedule length in the tree construction phase.
Abstract: We consider the problem of scheduling in wireless sensor networks for the purposes of aggregation convergecast. We observe that existing schemes adopt essentially a two phase approach, consisting of, first, a tree construction and, second, a scheduling phase. Following a similar approach, we propose two new improvements, one to each of the two phases. Starting with a new lower bound on the schedule length, we make use of it in the tree construction phase. The tree construction phase consists of solutions to instances of bipartite graph semi-matchings. The scheduling phase is a weight-based priority scheme that obeys dependency (tree) and interference constraints. Our extensive experiments show that, overall, our proposed solution not only outperforms all previously proposed solutions in terms of schedule length, but it also significantly extends the network's lifetime.
102 citations
TL;DR: The Behavior-based Mobility Prediction scheme to eliminate the scanning overhead incurred in IEEE 802.11 networks is presented, which improves the next-cell prediction accuracy by 23~43% compared to location-only based schemes and reduces the average handoff delay down to 24~25 ms.
Abstract: The field of wireless networking has received unprecedented attention from the research community during the last decade due to its great potential to create new horizons for communicating beyond the Internet. Wireless LANs (WLANs) based on the IEEE 802.11 standard have become prevalent in public as well as residential areas, and their importance as an enabling technology will continue to grow for future pervasive computing applications. However, as their scale and complexity continue to grow, reducing handoff latency is particularly important. This paper presents the Behavior-based Mobility Prediction scheme to eliminate the scanning overhead incurred in IEEE 802.11 networks. This is achieved by considering not only location information but also group, time-of-day, and duration characteristics of mobile users. This captures short-term and periodic behavior of mobile users to provide accurate next-cell predictions. Our simulation study of a campus network and a municipal wireless network shows that the proposed method improves the next-cell prediction accuracy by 23~43% compared to location-only based schemes and reduces the average handoff delay down to 24~25 ms.
89 citations
TL;DR: The observed results show that the distributed heuristic achieves network lifetimes that are remarkably close to the optimum ones, resulting also in significant improvements over the cases of deploying the sinks statically, of random sink mobility and of heuristics previously proposed for restricted sink movements.
Abstract: We define scalable models and distributed heuristics for the concurrent and coordinated movement of multiple sinks in a wireless sensor network, a case that presents significant challenges compared to the widely investigated case of a single mobile sink. Our objective is that of maximizing the network lifetime defined as the time from the start of network operations till the failure of the first node. We contribute to this problem providing three new results. We first define a linear program (LP) whose solution provides a provable upper bound on the maximum lifetime possible for any given number of sinks. We then develop a centralized heuristic that runs in polynomial time given the solution to the LP. We also define a deployable distributed heuristic for coordinating the motion of multiple sinks through the network. We demonstrate the performance of the proposed heuristics via ns2-based simulations. The observed results show that our distributed heuristic achieves network lifetimes that are remarkably close to the optimum ones, resulting also in significant improvements over the cases of deploying the sinks statically, of random sink mobility and of heuristics previously proposed for restricted sink movements.
70 citations
TL;DR: The results validate the probabilistic method for coverage estimation and show that the proposed sleep scheduling and routing scheme can significantly increase the network lifetime while keeping the message complexity low and preserving both connectivity and coverage.
Abstract: Sleep scheduling, which is putting some sensor nodes into sleep mode without harming network functionality, is a common method to reduce energy consumption in dense wireless sensor networks. This paper proposes a distributed and energy efficient sleep scheduling and routing scheme that can be used to extend the lifetime of a sensor network while maintaining a user defined coverage and connectivity. The scheme can activate and deactivate the three basic units of a sensor node (sensing, processing, and communication units) independently. The paper also provides a probabilistic method to estimate how much the sensing area of a node is covered by other active nodes in its neighborhood. The method is utilized by the proposed scheduling and routing scheme to reduce the control message overhead while deciding the next modes (full-active, semi-active, inactive/sleeping) of sensor nodes. We evaluated our estimation method and scheduling scheme via simulation experiments and compared our scheme also with another scheme. The results validate our probabilistic method for coverage estimation and show that our sleep scheduling and routing scheme can significantly increase the network lifetime while keeping the message complexity low and preserving both connectivity and coverage.
54 citations
TL;DR: Two hybrid clustering based data aggregation mechanisms are proposed that can increase the data aggregation efficiency as well as improve energy efficiency and other important issues compared to previous works.
Abstract: In wireless sensor network applications for surveillance and reconnaissance, large amounts of redundant sensing data are frequently generated. It is important to control these data with efficient data aggregation techniques to reduce energy consumption in the network. Several clustering methods were utilized in previous works to aggregate large amounts of data produced from sensors in target tracking applications (Park in A dissertation for Doctoral in North Carolina State University, 2006). However, such data aggregation algorithms show effectiveness only in restricted environments, while posing great problems when adapting to other various situations. To alleviate these problems, we propose two hybrid clustering based data aggregation mechanisms. The combined clustering-based data aggregation mechanism can apply multiple clustering techniques simultaneously in a single network depending on the network environment. The adaptive clustering-based data aggregation mechanism can adaptively choose a suitable clustering technique, depending on the status of the network. The proposed mechanisms can increase the data aggregation efficiency as well as improve energy efficiency and other important issues compared to previous works. Performance evaluation via mathematical analysis and simulation has been made to show the effectiveness of the proposed mechanisms.
46 citations
TL;DR: Two new metrics are introduced to aid in the selection of the sensor nodes which will take special roles in running the caching and request forwarding decisions in PCICC and scaPCICC, which are compared against the state-of-the-art competing protocol, namely NICoCa.
Abstract: During the last decade, Wireless Sensor Networks have emerged and matured at such point that they currently support several applications such as environment control, intelligent buildings, target tracking in battlefields. The vast majority of these applications require an optimization to the communication among the sensors so as to serve data in short latency and with minimal energy consumption. Cooperative data caching has been proposed as an effective and efficient technique to achieve these goals concurrently. The essence of these protocols is the selection of the sensor nodes which will take special roles in running the caching and request forwarding decisions. This article introduces two new metrics to aid in the selection of such nodes. Based on these metrics, we propose two new cooperative caching protocols, PCICC and scaPCICC, which are compared against the state-of-the-art competing protocol, namely NICoCa. The proposed solutions are evaluated extensively in an advanced simulation environment and the results confirm that the proposed caching mechanisms prevail over its competitor. The evaluation attests also that the best policy is always scaPCICC, achieving the shortest latency and the least number of transmitted messages.
43 citations
TL;DR: This paper takes an integrated design approach to jointly optimize multimedia intra refreshing rate, an application layer parameter, together with access strategy, and spectrum sensing for multimedia transmission in a CR system with time varying wireless channels.
Abstract: In cognitive radio (CR) networks, the perceived reduction of application layer quality of service (QoS), such as multimedia distortion, by secondary users may impede the success of CR technologies. Most previous work in CR networks ignores application layer QoS. In this paper we take an integrated design approach to jointly optimize multimedia intra refreshing rate, an application layer parameter, together with access strategy, and spectrum sensing for multimedia transmission in a CR system with time varying wireless channels. Primary network usage and channel gain are modeled as a finite state Markov process. With channel sensing and channel state information errors, the system state cannot be directly observed. We formulate the QoS optimization problem as a partially observable Markov decision process (POMDP). A low complexity dynamic programming framework is presented to obtain the optimal policy. Simulation results show the effectiveness of the proposed scheme.
43 citations
TL;DR: This paper formulate the jamming effects using two jamming models: region-based and signal-to-noise-ratio(SNR)-based; and they categorize network nodes into three states based on the level of disturbance caused by the jammer.
Abstract: Wireless communication is susceptible to radio interference and jamming attacks, which prevent the reception of communications. Most existing anti-jamming work does not consider the location information of radio interferers and jammers. However, this information can provide important insights for networks to manage its resource in different layers and to defend against radio interference. In this paper, we investigate issues associated with localizing jammers in wireless networks. In particular, we formulate the jamming effects using two jamming models: region-based and signal-to-noise-ratio(SNR)-based; and we categorize network nodes into three states based on the level of disturbance caused by the jammer. By exploiting the states of nodes, we propose to localize jammers in wireless networks using a virtual-force iterative approach. The virtual-force iterative localization scheme is a range-free position estimation method that estimates the position of a jammer iteratively by utilizing the network topology. We have conducted experiments to validate our SNR-based jamming model and performed extensive simulation to evaluate our approach. Our simulation results have showed that the virtual-force iterative approach is highly effective in localizing a jammer in various network conditions when comparing to existing centroid-based localization approaches.
39 citations
TL;DR: A new analytical model to predict accurate media access delay by obtaining its distribution function in a single wireless node and extending the modeling approach to investigate the delay in multi-hop networks is proposed.
Abstract: Several analytical models of different wireless networking schemes such as wireless LANs and meshes have been reported in the literature. To the best of our knowledge, all these models fail to address the accurate end-to-end delay analysis of multi-hop wireless networks under unsaturated traffic condition considering the hidden and exposed terminal situation. In an effort to gain deep understanding of delay, this paper firstly proposes a new analytical model to predict accurate media access delay by obtaining its distribution function in a single wireless node. The interesting point of having the media access delay distribution is its generality that not only enables us to derive the average delay which has been reported in almost most of the previous studies as a special case but also facilitates obtaining higher moments of delay such as variance and skewness to capture the QoS parameters such as jitters in recently popular multimedia applications. Secondly, using the obtained single node media access delay distribution, we extend our modeling approach to investigate the delay in multi-hop networks. Moreover, probabilities of collisions in both hidden and exposed terminal conditions have been calculated. The validity of the model is demonstrated by comparing results predicted by the analytical model against those obtained through simulation experiments.
TL;DR: A proxy-based autoconfiguration protocol that guarantees the assignment of a unique address to each node in the network and outperforms similar network address configuring mechanisms in terms of latency and overhead.
Abstract: Sensor networks have become increasingly important in various areas, and most current applications require connectivity between sensor networks and the Internet. By being seamlessly integrated into IP network infrastructure, sensor network applications would benefit from standardized and established technology, as well as from the plethora of readily available applications. Preparing sensor networks for IP communication and integrating them into the IP network, however, present new challenges on the architecture and its functional blocks, e.g., the adaptation of the respective link technology for IP support, development of security mechanisms, and autoconfiguration to support ad hoc deployment. In this paper, we focus on the IPv6 address autoconfiguration issue and propose a proxy-based autoconfiguration protocol. The proposed protocol guarantees the assignment of a unique address to each node in the network. The protocol is simulated and implemented on off-the-shelf sensor network platforms. The experiment results show that our mechanism outperforms similar network address configuring mechanisms in terms of latency and overhead.
TL;DR: Simulation results reveal that the proposed technique is more suitable for real-world BS placement problem and a better distributed Pareto-front is obtained in MNSGA- II when compared with NSGA-II.
Abstract: In this paper, various parameters of cellular base station (BS) placement problem such as site coordinates, transmitting power, height and tilt angle are determined using evolutionary multiobjective algorithm to obtain better compromised solutions The maximization of service coverage and minimization of cost are considered as conflicting objectives by satisfying inequality constraints such as handover, traffic demand and overlap For the purpose of simulation, a 15 × 15 Km2 synthetic test system is discretized as hexagonal cell structure and necessary simulations are carried out to calculate receiving field strength at various points The path loss is calculated using Hata model To improve the diversity and uniformity of the obtained nondominated solutions, controlled elitism and dynamic crowding distance operators are introduced in non-dominated sorting genetic algorithm-II (NSGA-II) and are designated as modified NSGA-II (MNSGA-II) The optimal placement for BS is determined using MNSGA-II and NSGA-II The effect of maximum number of function evaluations, handover and overlap on the performances of the algorithms is studied A better distributed Pareto-front is obtained in MNSGA- II when compared with NSGA- II The results reveal that, increasing of overlap percentage not only increases the coverage but also increases the overlap and handover error The coverage percentage is indirectly proportional to the number of antennas involved in the handover constraint The simulation results reveal that the proposed technique is more suitable for real-world BS placement problem
TL;DR: It is proved that every quasi-UDG has a corresponding grid graph with small balanced separators that captures its connectivity properties and a distributed local algorithm is presented that constructs a nearly planar backbone with a constant stretch factor and a bounded degree.
Abstract: A deep understanding of the structural properties of wireless networks is critical for evaluating the performance of network protocols and improving their designs. Many protocols for wireless networks--routing, topology control, information storage/retrieval and numerous other applications--have been based on the idealized unit-disk graph (UDG) network model. The significant deviation of the UDG model from many real wireless networks is substantially limiting the applicability of such protocols. A more general network model, the quasi unit-disk graph (quasi-UDG) model, captures much better the characteristics of wireless networks. However, the understanding of the properties of general quasi-UDGs has been very limited, which is impeding the designs of key network protocols and algorithms. In this paper, we present results on two important properties of quasi-UDGs: separability and the existence of power efficient spanners. Network separability is a fundamental property leading to efficient network algorithms and fast parallel computation. We prove that every quasi-UDG has a corresponding grid graph with small balanced separators that captures its connectivity properties. We also study the problem of constructing an energy-efficient backbone for a quasi-UDG. We present a distributed local algorithm that, given a quasi-UDG, constructs a nearly planar backbone with a constant stretch factor and a bounded degree. We demonstrate the excellent performance of these auxiliary graphs through simulations and show their applications in efficient routing.
TL;DR: This paper forms the channel access process in CR network as a restless bandit system, and exploits cross-layer design methodology to improve TCP throughput, where modulation and coding at the physical layer and frame size at the data-link layer are considered together with TCP throughput in the transport layer to improve UDP performance.
Abstract: Cognitive radio (CR) is a promising technology to improve spectrum utilization. Most of previous work on CR networks concentrates on maximizing transmission rate in the physical layer. However, the end-to-end transmission control protocol (TCP) performance perceived by secondary users is also a very important factor in CR networks. In this paper, we propose a novel multi-channel access scheme in CR networks, where the channel access is based on the TCP throughput in the transport layer. Specifically, we formulate the channel access process in CR network as a restless bandit system. With this stochastic optimization formulation, the optimal channel access policy is indexable, meaning that the channels with highest indices should be selected to transmit TCP traffic. In addition, we exploit cross-layer design methodology to improve TCP throughput, where modulation and coding at the physical layer and frame size at the data-link layer are considered together with TCP throughput in the transport layer to improve TCP performance. Simulation results show the effectiveness of the proposed scheme.
TL;DR: Numerical results show that the proposed vertical handoff decision algorithm outperforms other decision schemes in a wide range of conditions such as variations on connection duration, user’s velocity, users’ budget, traffic type, signaling cost, and monetary access cost.
Abstract: The 4th generation wireless communication systems aim to provide users with the convenience of seamless roaming among heterogeneous wireless access networks. To achieve this goal, the support of vertical handoff is important in mobility management. This paper focuses on the vertical handoff decision algorithm, which determines the criteria under which vertical handoff should be performed. The problem is formulated as a constrained Markov decision process. The objective is to maximize the expected total reward of a connection subject to the expected total access cost constraint. In our model, a benefit function is used to assess the quality of the connection, and a penalty function is used to model the signaling incurred and call dropping. The user's velocity and location information are also considered when making handoff decisions. The policy iteration and Q-learning algorithms are employed to determine the optimal policy. Structural results on the optimal vertical handoff policy are derived by using the concept of supermodularity. We show that the optimal policy is a threshold policy in bandwidth, delay, and velocity. Numerical results show that our proposed vertical handoff decision algorithm outperforms other decision schemes in a wide range of conditions such as variations on connection duration, user's velocity, user's budget, traffic type, signaling cost, and monetary access cost.
TL;DR: This work proposes two mechanisms that augment the current multicasting standards in a backward-compatible fashion: semi-reliable multicasting (SRM) and probing-based auto-rate fallback (PARF).
Abstract: Multicasting multimedia streams in IEEE 802.11 wireless LANs has two issues: reliability and rate adaptation. We address these issues by proposing two mechanisms that augment the current multicasting standards in a backward-compatible fashion. Semi-reliable multicasting (SRM) selects a leader who sends feedback information to lessen the reliability problem of multicast frames. Probing-based auto-rate fallback (PARF) allows the multicast source to adjust the bit rate depending on the link conditions of multicast recipients. Comprehensive simulation experiments reveal that SRM + PARF achieves reliability and link efficiency close to those of an omniscient multicasting framework.
TL;DR: This work develops polynomial time algorithms to provably approximate the throughput capacity of wireless network under the SINR model, on arbitrary wireless networks without any assumptions on node distributions.
Abstract: A fundamental problem in wireless networks is to estimate their throughput capacity--given a set of wireless nodes and a set of connections, what is the maximum rate at which data can be sent on these connections. Most of the research in this direction has focused either on random distributions of points, or has assumed simple graph-based models for wireless interference. In this paper, we study the capacity estimation problem using a realistic Signal to Interference Plus Noise Ratio (SINR) model for interference, on arbitrary wireless networks without any assumptions on node distributions. The problem becomes much more challenging for this setting, because of the non-locality of the SINR model. Recent work by Moscibroda et al. (IEEE INFOCOM 2006, ACM MobiHoc 2006) has shown that the throughput achieved by using SINR models can differ significantly from that obtained by using graph-based models. In this work, we develop polynomial time algorithms to provably approximate the throughput capacity of wireless network under the SINR model.
TL;DR: This paper proposes a topology control method for multi-channel multi-radio wireless mesh networks that use directional antennas, and constructs a set of routing trees to balance the traffic among tree links.
Abstract: Directional antennas are widely used technologies for reducing signal interference and increasing spatial reuse. In this paper, we propose a topology control method for multi-channel multi-radio wireless mesh networks that use directional antennas. We are given a set of mesh routers installed in a region and some of them are gateway nodes that are connected to the Internet via wired lines. Each router has a traffic demand (Internet access traffic) generated from the end-users. The problem is how to adjust antenna orientations of radios and assign channels to them to construct a logical network topology, such that the minimum delivery ratio of traffic demands of routers is maximized. We first formulate the problem to an equivalent optimization problem with a clearer measurable metric, which is to minimize the largest interfering traffic of links in the network. We then propose a three-step solution to solve the problem. Firstly, we construct a set of routing trees, with the objective to balance the traffic among tree links. Secondly, we assign the radios of a node to the links it needs to serve, such that the total traffic load of the links that each radio serves is as balanced as possible. Thirdly, we do a fine-grained adjustment of antenna orientations and assign channels to them, such that the transmission area of each antenna will cover all the links it serves and the largest interfering traffic of links is minimized.
TL;DR: An analytic approximation of the performance of elastic traffic in wireless cellular networks accounting for user’s mobility is given by a Whittle one for which the performance is expressed analytically and may be used for a conservative dimensioning of the cellular networks.
Abstract: The objective of the present paper is to give an analytic approximation of the performance of elastic traffic in wireless cellular networks accounting for user's mobility. To do so we build a Markovian model for users arrivals, departures and mobility in such networks; which we call WET model. We firstly consider intracell mobility where each user is confined to remain within its serving cell. Then we consider the complete mobility where users may either move within each cell or make a handover (i.e. change to another cell). We propose to approximate the WET model by a Whittle one for which the performance is expressed analytically. We validate the approximation by simulating an OFDMA cellular network. We observe that the Whittle approximation underestimates the throughput per user of the WET model. Thus it may be used for a conservative dimensioning of the cellular networks. Moreover, when the traffic demand and the user speed are moderate, the Whittle approximation is good and thus leads to a precise dimensioning.
TL;DR: This work views the problem of channel assignment in multi-channel multi-radio networks with multiple collision domains as a non-cooperative game where the objective of the players is to maximize their individual utility by minimizing its interference.
Abstract: Channel assignment in multi-channel multi-radio wireless networks poses a significant challenge due to scarcity of number of channels available in the wireless spectrum. Further, additional care has to be taken to consider the interference characteristics of the nodes in the network especially when nodes are in different collision domains. This work views the problem of channel assignment in multi-channel multi-radio networks with multiple collision domains as a non-cooperative game where the objective of the players is to maximize their individual utility by minimizing its interference. Necessary and sufficient conditions are derived for the channel assignment to be a Nash Equilibrium (NE) and efficiency of the NE is analyzed by deriving the lower bound of the price of anarchy of this game. A new fairness measure in multiple collision domain context is proposed and necessary and sufficient conditions for NE outcomes to be fair are derived. The equilibrium conditions are then applied to solve the channel assignment problem by proposing three algorithms, based on perfect/imperfect information, which rely on explicit communication between the players for arriving at an NE. A no-regret learning algorithm known as Freund and Schapire Informed algorithm, which has an additional advantage of low overhead in terms of information exchange, is proposed and its convergence to the stabilizing outcomes is studied. New performance metrics are proposed and extensive simulations are done using Matlab to obtain a thorough understanding of the performance of these algorithms on various topologies with respect to these metrics. It was observed that the algorithms proposed were able to achieve good convergence to NE resulting in efficient channel assignment strategies.
TL;DR: This paper provides polynomial time approximation algorithms, with guaranteed performance bounds while considering omnidirectional and unid Directional transmissions, and considers an extended variant of the maximum lifetime problem, which simultaneously satisfies additional constraints, such as bounded hop-diameter and degree of the routing tree, and minimizing the total energy used in a single transmission.
Abstract: One of the major concerns in wireless ad-hoc networks design is energy efficiency. Wireless devices are typically equipped with a limited energy supply sufficient only for a limited amount of time which is reversely proportional to the transmission power of the device. The network lifetime is defined as the time the first device runs out of its initial energy charge. In this paper we study the maximum network lifetime problem for broadcast and data gathering in wireless settings. We provide polynomial time approximation algorithms, with guaranteed performance bounds while considering omnidirectional and unidirectional transmissions. We also consider an extended variant of the maximum lifetime problem, which simultaneously satisfies additional constraints, such as bounded hop-diameter and degree of the routing tree, and minimizing the total energy used in a single transmission. Finally, we evaluate the performance of some of our algorithms through simulations.
TL;DR: This paper presents an extensive survey and classification of channel (bandwidth) reservation schemes which employ user mobility prediction in the resource reservation process, including discussion of prioritized and non-prioritized handoff schemes.
Abstract: Provision of seamless service to multimedia applications in cellular wireless networks largely depends on the way calls are handled during handoff. Hence, sufficient resources must be provided for handoff (HO) connections when a mobile station (MS) moves from one cell to another. Effective allocation of resources can be achieved when the exact future trajectory of MSs is known in advance. However, such a scenario is unrealistic. The next best possibility is to employ user mobility prediction to determine the cell(s) a MS will likely visit in the near future. In this paper, we present an extensive survey and classification of channel (bandwidth) reservation schemes which employ user mobility prediction in the resource reservation process. We also present a survey and classification of call admission control (CAC) schemes, including discussion of prioritized and non-prioritized handoff schemes, which can be useful for researches both in academia and industry.
TL;DR: A methodology is proposed to make the localization algorithms robust by calculating such flip ambiguity probabilities and eliminating potentially poor location estimates as well as assigning confidence factors to the estimated locations to prevent them from ruining the subsequent localization steps.
Abstract: Collinear or near collinear placement of some sensors in a wireless sensor network causes the location estimates of nearby sensors to be sensitive to erroneous distance measurements which leads to large location estimation errors. These errors and the possible propagation of these errors to the entire network or a large portion of it, thereby causing larger estimation errors for some sensors' locations, is a major problem in localization. This phenomenon is well described in rigid graph theory, using the notion of "flip ambiguity". This paper considers arbitrary sensor neighborhoods of two dimensional sensor networks and formulates an analytical expression for the probability of occurrence of the flip ambiguity. Based on the derived probability expression, a methodology is proposed to make the localization algorithms robust by calculating such flip ambiguity probabilities and eliminating potentially poor location estimates as well as assigning confidence factors to the estimated locations to prevent them from ruining the subsequent localization steps. The efficiency of the proposed methodology is demonstrated via a set of simulations.
TL;DR: A closed form solution to the movement threshold is derived that minimizes the total cost of location management in an MBLMS for the CPLU model when the inter-call time has an arbitrary distribution and the cell residenceTime has an Erlang distribution.
Abstract: The paper makes new contributions to cost analysis and minimization of movement-based location management schemes in wireless communication networks. The main contributions of the paper are three-fold. First, we consider two different call handling models, that is, the call plus location update (CPLU) model and the call without location update (CWLU) model. We point out that all existing analysis of location update cost of a movement-based location management scheme (MBLMS) do not accurately capture the essence of the two models. Second, we analyze the exact location update cost of an MBLMS under both CPLU and CWLU models using a renewal process approach which has rarely been used before. We find that the location update cost of an MBLMS under the CWLU model is much easier to analyze than that of an MBLMS under the CPLU model. Furthermore, an MBLMS operated under the CWLU model has lower location update cost than an MBLMS operated under the CPLU model. Third, we are able to derive a closed form solution to the movement threshold that minimizes the total cost of location management in an MBLMS for the CPLU model when the inter-call time has an arbitrary distribution and the cell residence time has an Erlang distribution, and for the CWLU model when both inter-call time and cell residence time have arbitrary distributions. Such closed form solutions have not been available in the existing literature.
TL;DR: The IDRA platform is presented: an information driven architecture designed to support next-generation applications on resource constrained networked objects that is much more scalable in terms of memory requirements, energy requirements and processing overhead than traditional system architectures.
Abstract: Wireless sensor networks consist of embedded devices (sensor nodes), equipped with a low-power radio. They are used for many applications: from wireless building automation to e-health applications. However, due to the limited capabilities of sensor nodes, designing network protocols for these constrained devices is currently very challenging. Therefore, this paper presents the IDRA platform: an information driven architecture designed to support next-generation applications on resource constrained networked objects. IDRA supports simple but useful optimizations at an architectural level. These include support for cross-protocol interactions, energy efficiency optimizations, QoS optimizations (packet priorities, dynamic protocol selection), mobility support and heterogeneous network support. The paper shows how the development of protocols is improved by using an architecture which delegates specific tasks to a central system, decreasing the memory requirements of associated network protocols. A thorough experimental performance analysis demonstrates that IDRA is much more scalable in terms of memory requirements, energy requirements and processing overhead than traditional system architectures. Finally, the paper discusses how the optimizations presented in this paper can be used for the clean-slate design of architectures for other wireless or wired network types.
TL;DR: A novel service protocol relying on the typical wireless sensor network is proposed, which provides high throughput through distributed data gathering and low latency through short-hops data delivery to the traditional remote users and mobile users.
Abstract: A wireless sensor network typically consists of users, a sink, and a number of sensor nodes. The users may be remotely connected to a wireless sensor network and via legacy networks such as Internet or Satellite the remote users obtain data collected by the sink that is statically located at a border of the wireless sensor network. However, in practical sensor network applications, there might be two types of users: the traditional remote users and mobile users such as firefighters and soldiers. The mobile users may move around sensor fields and they communicate with the static sink only via the wireless sensor networks in order to obtain data like location information of victims in disaster areas. For supporting the mobile users, existing studies consider temporary structures. However, the temporary structures are constructed per each mobile user or each source nodes so that it causes large energy consumption of sensor nodes. Moreover, since some of them establish the source-based structure, sinks in them cannot gather collective information like mean temperature and object detection. In this paper, to effectively support both the remote users and the mobile users, we propose a novel service protocol relying on the typical wireless sensor network. In the protocol, multiple static sinks connect with legacy networks and divide a sensor field into the number of the multiple sinks. Through sharing queries and data via the legacy networks, the multiple static sinks provide high throughput through distributed data gathering and low latency through short-hops data delivery. Multiple static sinks deliver the aggregated data to the remote users via the legacy networks. In case of the mobile users, when a mobile user moves around, it receives the aggregated data from the nearest static sink. Simulation results show that the proposed protocol is more efficient in terms of energy consumption, data delivery ratio, and delay than the existing protocols.
TL;DR: It is shown that scalability and faster recovery from failures can be achieved by dynamic address allocation, and the dynamic address assignment protocol presented here requires a low memory footprint while supporting unicast, broadcast and multicast communication.
Abstract: Dynamic address allocation is an essential part in effective configuration and maintenance of a mobile ad-hoc network (MANET). In this paper, we present a new distributed dynamic address allocation protocol minimizing address allocation latency and communication overhead. Through analytic evaluation and experimental measurements, we show that scalability and faster recovery from failures can be achieved by dynamic address allocation. The dynamic address assignment protocol presented here requires a low memory footprint while supporting unicast, broadcast and multicast communication. A performance analysis of the proposed address allocation protocol is given in terms of address allocation latency and communication overhead. Node and Network mobility is addressed from the point of dynamic address management. The dynamic address allocation protocol is implemented on a TinyOS platform over a cluster tree network.
TL;DR: This paper addresses target tracking in wireless sensor networks (WSN) where the observed system is assumed to evolve according to a probabilistic state space model and proposes to improve the use of the variational filtering by optimally quantizing the data collected by the sensors.
Abstract: This paper addresses target tracking in wireless sensor networks (WSN) where the observed system is assumed to evolve according to a probabilistic state space model. We propose to improve the use of the variational filtering (VF) by optimally quantizing the data collected by the sensors. Recently, VF has been proved to be suitable to the communication constraints of WSN. Its efficiency relies on the fact that the online update of the filtering distribution and its compression are executed simultaneously. However, this problem has been used only for binary sensor networks neglecting the transmission energy consumption in a WSN and the information relevance of sensor measurements. Our proposed method is intended to jointly estimate the target position and optimize the quantization level under fixed and variable transmitting power. At each sampling instant, the adaptive method provides not only the estimate of the target position by using the VF but gives also the optimal number of quantization bits per observation. The adaptive quantization is achieved by minimizing the predicted Cramer---Rao bound if the transmitting power is constant for all sensors, and optimizing the power scheduling under distortion constraint if this power is variable. The computation of the predicted Cramer---Rao bound is based on the target position predictive distribution provided by the VF algorithm. The proposed adaptive quantization scheme suggests that the sensors with bad channels or poor observation qualities should decrease their quantization resolutions or simply become inactive in order to save energy.
TL;DR: The results show that bandwidth estimation using a probe-based tool can be challenging in certain WLAN environments, and practically infeasible in EVDO cellular networks, due to the short-scale dynamics in this type of networks.
Abstract: Bandwidth estimation refers to the measurement of a bandwidth-related metric over a network path, performed only by the end hosts, without access to the intermediate routers. The problem of fast bandwidth estimation has been extensively studied in the wired Internet. More recently, researchers have shown that tools developed for the wired Internet cannot be used in wireless networks, due to the different characteristics of these networks which invalidate many of the assumptions made for the wired Internet. This observation has led to new tools that take into account the different characteristics of wireless networks. These tools have only been evaluated in controlled environments, under controlled settings and interferers, and only for 802.11 CSMA-based WLANs. In addition, no tool has been reported so far in the literature for cellular networks. This paper presents the first study of the feasibility of fast bandwidth estimation in wireless networks "in the wild", i.e., in deployed operational networks. We discuss the challenges associated with bandwidth measurements in operational networks in contrast to in controlled lab environments. We study the applicability of a state-of-the-art probe-based tool for 802.11 WLANs in a commercial 1 × EVDO network. In addition, we evaluate the accuracy of the tool in three different WLAN environments, i.e., lab, home, and hotspot. Our results show that bandwidth estimation using a probe-based tool can be challenging in certain WLAN environments, and practically infeasible in EVDO cellular networks, due to the short-scale dynamics in this type of networks.