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In the paper a performance evaluation model of mobile wireless sensor network is presented. The model is based on renewal theory. The hierarchical structure of the network holds a clusters composed of ordinary sensors. Afterwards, all clusterhead sensors belong to a backbone network which is needed for data transmission to the sink of the sensor network. Some sensors are mobile and can send their data to the clusterhead sensors. In this paper, we address one of the fundamental problems, namely performance modeling of mobile wireless sensor networks. Moreover, our model can also be used for ordinary wireless sensor networks which are static and geometrically constrained. Specific models are suggested and analysed for different communication needs. [ABSTRACT FROM AUTHOR]

In some specific applications, sensors can be deployed in a deterministic way to form regular network. This paper firstly analyzes the relationship between the probability of coverage and that of the node failure in the network with triangular topology. Then the fault tolerance performance in triangular topology network is analyzed by using the k-subnet. At last, the paper discusses the connectivity performance in triangular topology network and in grid topology network. [ABSTRACT FROM AUTHOR]

For multi-hop wireless networks using IEEE 802.11 most TCP performance degradation results from hidden, exposed terminal problems and bandwidth waste caused by exponential backoff of retransmission timer due to node's mobility, not from collisions. However, in normal DCF algorithm, a failed user increases its contention window (CW) exponentially, thus it reduces the success probability of exposed terminal nodes. That is, these problems will cause burst data transmissions frequently in a particular node which already was successful in packet transmission, because the probability of successful packet transmission rate would be increased. To solve these problems, in this paper, we propose an efficient contention window control (ECWC) scheme to increase TCP performance in wireless multi-hop network. The proposed ECWC scheme is suggested to reduce the hidden and exposed terminal problems of wireless multi-hop network. That is, the proposed scheme increases the number of backoff retransmissions to increase the successful probability rate of MAC transmission, and fixes the contention window at a predetermined value. [ABSTRACT FROM AUTHOR]

In this paper, a new QoS model is presented for end-to-end service provisioning in wireless ad hoc networks. Many previous works focus on the packet scheduling mechanism using multiple service classes implemented for traffic prioritization based service differentiation. However, this paper concentrates on a scheme for dynamically selecting a proper one among several forwarding classes that perform different service rate according to service requirements. There service requirements include low delay, high throughput, and low loss. The proposed solution is a new QoS provisioning model called Dynamic Hop Service Differentiation (DHSD). This model supports soft QoS provisioning to reduce network overhead and wireless PHB (WPHB) to achieve the end-to-end QoS required by applications. The proposed QoS model is evaluated using OPNET simulation. We show that this model outperforms both best-effort and strict priority service models in wireless ad hoc network environments. [ABSTRACT FROM AUTHOR]

The ieee 802.11 mac-protocol, often used in ad-hoc networks, has the tendency to share the capacity equally amongst the active nodes, irrespective of their loads. An inherent drawback of this fair-sharing policy is that a node that serves as a relay-node for multiple flows is likely to become a bottleneck. This paper proposes a flow-level performance model of such a bottleneck node using fluid-flow analysis. Assuming Poisson initiations of new flow transfers at the bottleneck node, we obtain insightful, robust, and explicit expressions for characteristics related to the overall flow transfer time, the buffer occupancy, and the packet delay at the bottleneck node. The analysis is enabled by a translation of the behavior of the bottleneck node and the source nodes in terms of an m/g/1 queueing model. We conclude the paper by an assessment of the impact of alternative capacity sharing amongst source nodes and the bottleneck in order to improve the performance of the bottleneck. [ABSTRACT FROM AUTHOR]

The absence of a router or a base station urges the need for better access control mechanism in the ad-hoc networks. This paper presents a localized approach for access control which implements ticket certification services through reputation mechanism. Reputation refers to, the opinion of one node as seen by other nodes. Ticket certification ensures that, only well behaving nodes (which forward and route packets of other nodes) can get the tickets and only they can access the network. The tickets are obtained from any node in the locality with high reputation instead of getting it from a centralized authority or from some k neighbors in the neighborhood. This paper gives the analysis and simulation results of the localized approach through reputation mechanism and proves that the localized access control with reputation is better than the localized approach without reputation. [ABSTRACT FROM AUTHOR]

Multipath is a sought-after mechanism to achieve reliability along the error-prone channel in wireless sensor networks. However, this technique is not energy efficient since sensor networks are subject to strict resource constraints. In this paper, we propose an energy aware method to combine multipath routing with practical network coding technique. Through this method, we can guarantee the same reliability while reduce much energy consumption by decreasing the number of paths needed to delivery data. This method only needs little metadata overhead and some small-scale linear operations. Simulations under different circumstances verify the theoretical results. The paper also discusses other advantages of network coding in multi-receiver case to illustrate our future work. [ABSTRACT FROM AUTHOR]

Service discovery is a basic requirement for mobile ad hoc networks to provide service efficiently with dynamically changing network topology. In this paper, we propose a service discovery protocol with maximal area disjoint path (SDMAD) for mobile ad hoc networks. The goal of SDMAD is to exploit multiple servers simultaneously and do parallel delivery. One key feature of SDMAD is that there is no contention between the multiple paths discovered by it. Moreover, SDMAD considers service discovery and routing jointly to reduce control overhead. Extensive simulations show that with SDMAD the performance of service delivery is greatly improved over that with other service discovery protocols. [ABSTRACT FROM AUTHOR]

In this paper, we investigate the performance of multicast protocols for wireless mobile ad hoc networks (MANETs). Recently, there have been several proposals to reduce overhead and enable scalability in respect to the number of multicast members. Explicit multicast protocols, which differ from common approaches proposed for MANET multicast routing, are based on the Xcast scheme and intends to reduce energy consumption. These protocols are best suited for use with Small Multicast Groups operating in dynamic networks of any size. Classical multicast protocols which are tree based or mesh based are more appropriate for large scale multicast group. We evaluate the performance of EM2NET, an Explicit Multicast Protocol for MANET, with other multicast protocols proposed for ad hoc networks via extensive and detailed simulation. The performance differentials are analyzed using varying network load, mobility and multicast group size in order to provide a qualitative assessment of the applicability of the protocols in different scenarios. Results indicate that EM2NET offers better energy conservation and also supports mobility better than existing explicit protocols. [ABSTRACT FROM AUTHOR]

The multiple expected sources of traffic skewness in Next- Generation SensorNets (NGSN) will trigger the need for load-balanced point-to-point routing protocols. Driven by this fact, we present in this paper a load-balancing primitive, namely Traffic-Oblivious Load-Balancing (TOLB), to be used on top of any point-to-point routing protocol. TOLB obliviously load balances traffic by pushing the decision-making responsibility to the source of any packet without depending on the energy status of the network sensors or on previously taken decisions for similar packets. We present theoretical bounds on TOLB's performance for special network types such as mesh networks. Additionally, we ran simulations to evaluate TOLB's performance on general networks. Our experimental results show the high benefit (in terms of network lifetime and throughput) of applying TOLB on top of routing schemes to deal with various traffic skewness levels in different sensor deployment scenarios. [ABSTRACT FROM AUTHOR]

The increased use of ubiquitous computing devices is resulting in networks that are highly mobile, well connected and growing in processing and storage capabilities. The nature of these ubiquitous systems, however, also increases the risk of building systems that are undependable and potentially insecure. This paper investigates the use of autonomous agents combined with an intrusion tolerance technique for providing secure and dependable storage for ad hoc networks. The proposed approach is based on the fragmentation-redundancy-scattering (FRS) technique that is able to tolerate both accidental and intentional faults by fragmenting confidential information into insignificant fragments, and by scattering these fragments in a redundant fashion across a network. Two algorithms that are able to maintain a constant number of fragments replicas were developed for this study: one based on the game of life, and the other based on roaming ants. Both algorithms were simulated in NetLogo, and simulated further in a cluster of computers for evaluation of their scalability. [ABSTRACT FROM AUTHOR]

In this paper, we propose an efficient and practical routing scheme for MANETs based on a new routing metric called the free-degree of nodes. In the proposed routing scheme named FDAR (Free-Degree Adaptive Routing), it is intended to deliver data packets circumventing congested routes, so as to realize a short end-to-end delay and a moderate load balancing of the overall network. In addition, it tries to avoid frequent and unnecessary invocation of route discovery process which would significantly degrade the routing performance of the MANET. The effectiveness of the proposed scheme is evaluated by simulation. The result of simulations indicates that it certainly outperforms previous load-balanced routing schemes including DLAR and LBAR, in terms of the packet loss rate and the average end-to-end delay. [ABSTRACT FROM AUTHOR]

The success of authentication mechanisms, intrusion detection and response systems, and other security measures to protect MANET from attack are very much dependant on nodes' cooperation. Ensuring a node's cooperation is very challenging in a MANET environment because of the nature of such a network; consisting of a set of anonymous nodes that operate independently, without the existence of a central authority to enforce them to cooperate. One of the solutions for this problem is by creating a trust chain between nodes to create a trusted community. This paper discusses some of the existing studies that have been proposed to overcome this issue and proposes a novel trust framework based upon a friendship concept. Results from simulation experiments proved that the proposed trust framework is capable of creating a trusted community in MANET, whilst at the same time addressing limitations of existing trust frameworks. [ABSTRACT FROM AUTHOR]

The in-network aggregation and processing of information is what sets a sensor network apart from a pure data acquisition device. One way to model the exchange of information between the network nodes is to distinguish between nodes that are producers of information, i.e., those that have collected data, detected events, etc., and nodes that are consumers of information, i.e., nodes that seek data or events of certain types. In this paper we aim to support that exchange of information via a so-called information brokerage scheme. Main features of our proposed scheme are that 1) it works in a location-free setting where nodes are unaware of their geographic locations 2) it is robust to non-regular network topologies and 3) it does not require the information producers and consumers to know of each other. Our proposed scheme employs boundary detection algorithms which only quite recently have been developed to extract geometry and topology information even in location-free network deployments. [ABSTRACT FROM AUTHOR]

Sensor networks are wireless adhoc networks where all the nodes cooperate for routing messages in the absence of a fixed infrastructure. Non-flooding, guaranteed delivery routing protocols are preferred because sensor networks have limited battery life. Location aware routing protocols are good candidates for sensor network applications, nevertheless they need either an external location service like GPS or Galileo (which are bulky, energy consuming devices) or internal location services providing non-unique virtual coordinates leading to low delivery rates. In this paper we introduce Position Trees a collision free, distributed labeling algorithm based on hop counting, which embed a spanning tree of the underlying network . The Routing with Position Trees (RTP) is a guaranteed delivery, non-flooding, efficient implicit routing protocol based on Position Trees. We study experimentally the statistical properties of memory requirements and the routing efficiency of the RPT. [ABSTRACT FROM AUTHOR]

Consumers increasingly demand high quality of service (QoS) for multimedia applications. Rate control scheme is one of the major methods that provide high video quality for mobile multimedia devices over wireless networks. This paper presents an efficient rate-control scheme which estimates the transmission power level of mobile devices, then adaptively adjusts the encoding bit rate according to the estimated power level to minimize overall distortion over sequences of video frames. Experimental results show that the proposed method can efficiently enhance the video quality and provide better peak signal to noise ratio (PSNR) performance than existing TMN8 rate control method. [ABSTRACT FROM AUTHOR]

In 2005, Liaw et al. proposed an ID-based key exchange protocol without the auxiliary of certification authority that can be applied to wireless mobile Ad hoc networks, which can solve the security problem in the Wireless Mobile Ad hoc Networks (MANET) and is suitable for other wired network structures. Liaw et al.'s protocol, however, still has other serious weaknesses. The current paper will demonstrate the vulnerability of the protocol. Furthermore, we present a method that can avoid attacks. Keywords: Cryptography, Wireless mobile, Ad hoc networks, Network security, Key exchange, ID-based, Impersonation attack. [ABSTRACT FROM AUTHOR]

TCP does not distinguish between congestion and packet losses due to route change and link failures, which are prevalent in mobile ad hoc networks. So, TCP does not show satisfactory performance in ad hoc networks since it assumes that all packet losses are due to network congestions. In particular, when a route is reestablished it needs to be adaptively determined congestion window (CWND) according to the new route features. In this paper, we proposed an adjustable CWND scheme to improve the TCP performance over ad hoc networks. TCP sender effectively adjusts CWND by monitoring the network situation using control packets. Simulation results using NS-2 show that our scheme may increase TCP throughput compared with those of general TCP. [ABSTRACT FROM AUTHOR]

The Bluetooth wireless technology realizes a low-cost short-range wireless voice- and data-connection through radio propagation. Bluetooth also has a security architecture. In this paper, we focus on the key agreement protocol, which is the most critical part of this security architecture. Several security flaws have been identified within the Bluetooth protocols: an attacker can track users by monitoring the Bluetooth hardware address, all keys depend on a low-entropy shared secret (the PIN), there are some very easy to perform Denial of Service attacks. We propose a new initialization mechanism for the key agreement protocol of Bluetooth. This improved pairing protocol can be easily extended so that it will not only solve the dependency of the keys on the PIN, but also the location privacy problem and an important Denial of Service attack. Our solution is user friendly and energy-efficient, two essential features for Wireless Personal Area Networks (WPAN). Keywords: Bluetooth, security, pairing. [ABSTRACT FROM AUTHOR]

Recently, identity-based cryptographic (IBC) schemes have been considered to secure mobile ad hoc networks (MANETs) due to their efficient key management properties. However, proposed schemes do not provide mechanisms for key revocation and key renewal. In this paper, we propose the first key revocation and key renewal mechanisms for IBC schemes that are especially designed for MANETs. In our fully self-organized revocation scheme, each node monitors nodes in communication range and securely propagates its observations. The public key of a node is revoked if a minimum number of nodes accused the node. To enable key renewal, we introduce a modified format for ID-based public keys, such that new keys can be issued for the same identity. The introduced revocation scheme is efficient because it uses pre-shared keys from the Weil pairing and messages are sent to an m-hop neighborhood instead to the entire network. Keyword: Identity-Based Schemes, Revocation, Key Renewal, Mobile Ad Hoc Networks, Neighborhood Monitoring. [ABSTRACT FROM AUTHOR]

In mobile ad hoc wireless networks, energy consumption is an important issue as most mobile nodes operate on limited battery resources. Existing models for evaluating the energy consumption in a mobile ad hoc network have shown that the various components of energy related costs include transmission power as well as the reception power. In this paper, we extend the model for calculating the energy spent at a node due to a flow in the network. We include the transmission and reception costs if the node belongs to a flow, and reception costs if it is near a flow. This model gives the energy costs of nodes in ideal conditions where interferences are absent. It is then extended to evaluate the interference effect on energy consumption in more realistic conditions. The collisions due to concurrent flows are also measured. We then show how the extra energy spent due to collisions can be calculated by predicting the collisions in the nodes of the network. This prediction is shown to be capable of accurate calculation of the extra energy consumption. [ABSTRACT FROM AUTHOR]

This paper proposes a novel routing protocol dedicated to IVC. This routing protocol, named as geographic pattern routing (GPR). The protocol does not need to search route frequently, so sufficient bandwidth is reserved for application packets, and QoS is easily guaranteed. It has ingredients to support geographic pattern search and packet forwarding assisted by geographic pattern, and it considers whether sufficient nodes are on the path represented by geographic pattern to allow packets forwarding to the destination. Besides vehicle location, it does not need other information. The simulation shows that GPR is better than other routing protocols. [ABSTRACT FROM AUTHOR]

This paper describes formal probabilistic models of flooding and gossiping protocols, and explores the influence of different modeling choices and assumptions on the results of performance analysis. We use Prism, a model checker for probabilistic systems, for the formal analysis of protocols and small network topologies, and use in addition Monte-Carlo simulation, implemented in Matlab, to establish if the results and effects found during formal analysis extend to larger networks. This combination of approaches has several advantages. The formal model has well defined synchronisation primitives with clear semantics for modeling synchronous and asynchronous communication between nodes. Model checking of the probabilistic model determines exact probabilities and performance bounds, even if the model is non-deterministic; results that cannot be obtained by simulation. However, Monte-Carlo simulation can then be used in addition to study effects that only emerge in larger networks, such as phase transition. [ABSTRACT FROM AUTHOR]

Geographical routing protocols have several desirable features for use in ad hoc and sensor networks but are susceptible to voids and localization errors. Virtual coordinate systems which overlay a coordinate system on the nodes offer an alternative that is more resilient to localization errors. However, we show that it is vulnerable to different forms of the void problem where packets reach nodes with no viable next hop in the forwarding set. In addition, it is possible for nodes with the same coordinates to arise at different points in the network in the presence of voids. This paper identifies and analyzes these problems. It also compares several existing routing protocols based on Virtual Coordinate systems. Finally, we propose a routing algorithm that uses geographic routing in the greedy phase and virtual coordinates with backtracking to overcome voids and achieve high connectivity in the greedy phase with higher overall path quality and more resilience to localization errors. We demonstrate these properties using extensive simulation studies. [ABSTRACT FROM AUTHOR]

This paper is concerned with the problem of checking whether a network with positive and negative costs on its arcs contains a negative cost cycle. We introduce a fundamentally new approach for negative cost cycle detection; our approach, which we term as the Stressing Algorithm, is based on exploiting the connections between the Negative Cost Cyle Detection (NCCD) problem and the problem of checking whether a system of difference constraints is feasible. The Stressing Algorithm is an incremental, comparison-based procedure which is asymptotically optimal, modulo the fastest comparison-based algorithm for this problem. In particular, on a network with n vertices and m edges, the Stressing Algorithm takes O(m· n) time to detect the presence of a negative cost cycle or to report that none exist. A very important feature of the Stressing Algorithm is that it uses zero extra space; this is in marked contrast to all known algorithms that require Ω(n) extra space. [ABSTRACT FROM AUTHOR]

Many to many reliable broadcast is useful while building distributed services like group membership and agreement in a MANET. Efforts in implementing reliable broadcast optimised for MANETs have resulted in new protocols that reduce the number of transmissions required to achieve reliable broadcast. A practical implementation of reliable broadcasts requires the ability to detect message stability, and there is still a need to develop protocols that efficiently support message stability determination in a MANET. In this paper we describe such a protocol that is independent of the broadcast optimisation being used, and focuses on providing efficient message stability. As the main idea of the protocol, we define a message dependency relationship and use this relationship to implement reliable broadcast as well as message stability detection. Simulations for mobile and static scenarios show our protocol has only a minimal performance degradation with node mobility. Keywords: message stability, reliable broadcast, MANET [ABSTRACT FROM AUTHOR]

The Route re-establishment methods that intend to extend the lifetime of the network attempt to find a new route periodically not to overly consume the energy of certain nodes. They outperform other algorithms in the network lifetime aspect, however, they require heavy signaling overheads because new routes are found based on the flooding method and route re-establishments occur frequently as a result. Because of the overhead they often can not extend the lifetime of the network as much as they want. In the paper, we propose a new maintenance algorithm which considers the costs associated with packet transmission and route re-establishment at the same time. Since the proposed algorithm considers packet transmission and future route re-establishment costs at the same time when it initially finds the route, it spends less energy to transmit the packets while evenly consuming the energy of the node as much as possible. Simulation results show that the proposed algorithm outperforms other route re-establishment methods. [ABSTRACT FROM AUTHOR]

We study the problem of computing multicast trees with minimal bandwidth consumption in multi-hop wireless mesh networks. For wired networks, this problem is known as the Steiner tree problem, and it has been widely studied before. We demonstrate in this paper, that for multihop wireless mesh networks, a Steiner tree does not offer the minimal bandwidth consumption, because it neglects the wireless multicat advantage. Thus, we re-formulate the problem in terms of minimizing the numbrer of transmissions, rather than the edge cost of multicast trees. We show that the new problem is also NP-complete and we propose heuristics to compute good approximations for such bandwidth-optimal trees. Our simulation results show that the proposed heuristics offer a lower bandwidth consumption compared with Steiner trees. [ABSTRACT FROM AUTHOR]

In this work we investigate bounds on throughput and delay performance of a scheduling protocol that derives its decisions from codes traditionally used to correct or detect errors in the information carried over a noisy channel. In this paper we study the particular cases in which the Reed-Solomon and Hermitian code constructions are used. It is found that Hermitian codes outperform Reed-Solomon codes in minimum throughput guarantee and delay metrics when the number of nodes is in the order of thousands. The relative minimum distance of the code used to schedule the transmissions is identified as an important property that can be used to identify codes that can enable scheduling patterns with better minimum performance guarantees. Furthermore, the terminology of error control coding is used to present a more general and constructive framework for the study of code-based scheduling protocols. [ABSTRACT FROM AUTHOR]

This paper proposes and analyzes a message scheduling scheme and corresponding capacity allocation method for the distributed hard real-time communication on dual Wireless LANs. By making the superframe of one network precede that of the other by half, the dual network architecture can minimize the effect of deferred beacon and reduce the worst case waiting time by half. The effect of deferred beacon is formalized and then directly considered to decide polling schedule and capacity vector. Simulation results executed via ns-2 show that the proposed scheme improves the schedulability by 36 % for real-time messages and allocates 9 % more bandwidth to non-real-time messages by enhancing achievable throughput for the given stream sets, compared with the network whose bandwidth is just doubled. [ABSTRACT FROM AUTHOR]

In this paper we present CCM-MAC, a cooperative CDMA-based multi-channel medium access control (MAC) protocol for multi-hop wireless networks. The protocol mitigates the multi-channel hidden and exposed terminal problems through cooperation from overhearing neighbours. By accounting for the multiple access interference obtained through cooperation, it also addresses the near-far problem of CDMA. We provide an analysis of the maximum throughput of CCM-MAC and validate it through simulation in Matlab. A significant improvement in network throughput is achieved over IEEE 802.11 and another multi-channel MAC protocol. [ABSTRACT FROM AUTHOR]

The primary concerns in ad hoc networks are bandwidth limitation and unpredictable dynamic topology. Therefore, efficient bandwidth utilization is crucial in routing protocols. The On-Demand Multicast Routing Protocol (ODMRP) was designed for multicast routing in ad hoc networks. It is very important to efficiently allocate and consume link bandwidth in this protocol, especially when many groups are working concurrently. In this paper, we propose a new method for estimating bandwidth in multicast protocols and also a new technique for supporting QoS routing in ODMRP by making an acceptable estimation of available and required bandwidth. Simulation results show that using QoS routing for ODMRP improves network performance in presence of mobility, by searching for suitable paths. [ABSTRACT FROM AUTHOR]

Flash memory is often the technology of choice for sensor networks because of its cost-effectiveness and attractive energy properties. In storage- constrained sensor network applications, the monitored data is typically stored in multi-resolution fashion. This allows reclamation of some storage space when needed by reducing the quality of stored data by eliminating some of the precision. Existing sensor network file systems are optimized for sequential logging of the data. However, flash memories have a number of unique properties that require careful consideration in file system design. In this paper, we show that in applications where adjustable resolution occurs, sequential logging file-systems result in an inefficient implementation of adjustable resolution. We propose an alternative implementation of the file system where data components are grouped with each other according to resolution. Thus, reducing resolution is implemented by simply erasing the pages with the excess resolution components. We have implemented the proposed scheme on crossbow MICA2 sensor nodes. In addition, using TOSSIM simulations, we show that as compared to the existing approach, the proposed scheme results in significant savings in read and write operations to the flash (thereby in turn saving energy, and reducing wear). Further, we show that wear leveling can be maintained over time by assigning the most significant data to the most frequently used pages. [ABSTRACT FROM AUTHOR]

A central problem in distributed computing and telecommunications is the establishment of common knowledge between two computing entities. An immediate use of such common knowledge is in the initiation of a secure communication session between two entities since the two entities may use this common knowledge in order to produce a secret key for use with some symmetric cipher. The dynamic establishment of shared information (e.g. secret key) between two entities is particularly important in networks with no predetermined structure such as wireless mobile ad-hoc networks. In such networks, nodes establish and terminate communication sessions dynamically with other nodes which may have never been encountered before in order to somehow exchange information which will enable them to subsequently communicate in a secure manner. In this paper we give and theoretically analyze a protocol that enables two entities initially possessing a string each to securely eliminate inconsistent bit positions, obtaining strings with a larger percentage of similarities. This can help the nodes establish a shared set of bits and use it as a key with some shared key encryption scheme. [ABSTRACT FROM AUTHOR]

In wireless sensor networks, sensor nodes are typically resource constrained and used as routers to forward packets for other nodes. Compromised sensor nodes may be able to cause network-wide denial of service by dropping or corrupting packets. This paper presents a novel, lightweight approach for detecting disruptive routers that drop or corrupt packets. Keywords: Denial of service, intrusion detection, routing security, sensor networks. [ABSTRACT FROM AUTHOR]

In this paper, an energy-efficient data disemination protocol designed for mobile sink applications in sensor networks, is proposed. The dissemination scheme exploits the Distributed Dynamic Tree (DDT), which is able to identify current location sinks locally and dynamically transform the tree shape according to sink movement. In addition, the Dynamic Shared Tree(DST), which is an extension of the DDT, is presented. The DST is able to accomocate multiple mobile sinks. The DST, based on the DDT, creates a two-tired network composed of a sensor data dissemination level and communication level between sinks. The simulation results demonstrate that the DST performs considerably energy-efficient data dissemination with relatively low delay, compared to other dissemination protocols. [ABSTRACT FROM AUTHOR]

Recently, due to the recent advance of ubiquitous wireless networking technology, there has been a great deal of research efforts for seem-less support of the movement of mobile networks. The IETF NEMO WG's approach to network mobility has the so called ‘pinball routing problem,' and the most of research attempts to solve this problem has limitations in the efficiency of both signaling and data communication. In this paper, we have presented policy-based mobility management architecture for next generation ubiquitous wireless networks, which can provide faster signaling and data transmission. In the proposed architecture, either care-of-address or home address of the root mobile router can be used as a binding address, which is decided by the policy on the route optimization. We present the architecture, model of the policy, and management procedures. Finally, the comparative analysis is provided by simulation to sow the efficiency of the proposed approach. [ABSTRACT FROM AUTHOR]

Geographic routing protocols are one of the most common routing schemes for sensor networks. These protocols consist of two different modes of operation: greedy routing to forward data to the destination using neighbors which are closer to the destination than current node and face routing to avoid voids in the network. Face routing requires the graph to be planar, which usually means that some crossing links of the original network cannot be considered when routing in face mode. In this paper we introduce a new localized scheme to build a virtual spanner which is planar by construction and is guaranteed to be connected if the underlying network is connected as well. Unlike previous works, by performing face routing over this spanner we can reduce energy consumption in face mode because the elimination of any of the original links in the network is not required. Thus, the most energy-efficient paths can be selected when the protocol enters face mode. The virtual spanner is easy-to-build and uses only local information, making it scalable to large-scale networks. Routing is always performed in real nodes; virtual nodes are used only as routing anchors when the agent is in face mode. In addition, our simulation results show that the proposed scheme outperforms the best energy-efficient geographic routing protocol for different network densities and energy models. [ABSTRACT FROM AUTHOR]

In this paper, we outline a simple approach, called ROAR, that enables the Ad-Hoc On-Demand Distance Vector (AODV) routing protocol to strengthen its routes by recruiting neighbors of nodes on the least cost path as support nodes during the route construction process, and working closely with the medium access control (MAC) to employ an opportunistic forwarding scheme that takes advantage of the node diversity at each hop. We have implemented ROAR in the ns-2 simulator over the IEEE 802.11a physical layer. From our simulation studies conducted using various network topologies and realistic radio propagation model, we find that ROAR increases AODV's packet delivery ratio and end-to-end throughput several orders of magnitude, in particular for hop count based routes. Therefore, ROAR provides a simple add-on that allows routing protocols to reap the benefits of diversity without relying on physical layer approaches. [ABSTRACT FROM AUTHOR]

In this paper, we propose an aggregation scheme, which is called Combine Early and Go Together (CEGT), to reduce the energy cost to transmit sensor data from sources to the sink. In the CEGT, the aggregation point is chosen in such a way that the sum of distances from source nodes to the sink via the aggregation point measured in the number of hops is minimized. Unlike most aggregation schemes, CEGT does not need to construct a tree from each source node to the sink. Simulation results show that our scheme can prolong the network life time and improve the path durability than the conventional schemes such as the gradient path and the shortest path schemes. [ABSTRACT FROM AUTHOR]

The Hierarchical Layer Graph (HL graph) is a promising network topology for wireless networks with variable transmission ranges. It was introduced and analyzed by Meyer auf der Heide et al. 2004. In this paper we present a distributed, localized and resource-efficient algorithm for constructing this graph. The qualtiy of the HL graph depends on the domination radius and the publication radius, which affect the amount of interference in the network. These parameters also determine whether the HL graph is a c-spanner, which implies an energy-efficient topology. We investigate the performance on randomly distributed node sets and show that the restrictions on these parameters derived from a worst case analysis are not so tight using realistic settings. Here, we present the results of our extensive experimental evaluation, measuring congestion, dilation and energy. Congestion includes the load that is induced by interfering edges. We distinguish between congestion and realistic congestion where we also take the signal-to-interference ratio into account. Our experiments show that the HL graph contains energy-efficient paths as well as paths with a few number of hops while preserving a low congestion. [ABSTRACT FROM AUTHOR]

In this paper we describe the deployment of an offshore wireless sensor network and the lightweight intelligence that was integrated into the data acquisition and forwarding software. Although the conditions were harsh and the hardware readily available, the deployment managed to characterise an extended period due the some unique algorithms. In-situ adaptation to differences in data types, hardware condition and user requirements are demonstrated and analysis of performance carried out. Statistical tests, local feedback and global genetic style material exchange ensure limited resources such as battery and bandwidth are used efficiently by manipulating data at the source. [ABSTRACT FROM AUTHOR]

In this paper we present DPUMA, a mesh-based multicast routing protocol specifically designed to reduce the overhead needed to deliver multicast packets, saving bandwidth and energy, two of the scarcest resources in MANETS. The two main features of DPUMA are: (1) for each multicast group, it periodically floods a single control packet to build the mesh, elect the core of the mesh and get two-hop neighborhood information; and (2), it computes the mesh's k-dominating set to further reduce overhead induced by flooding the mesh when forwarding data packets. These two characteristics contrast with other protocols that blindly flood the net in different stages to construct their routing structure (mesh or tree), to elect the leader of the structure, and that exchange hello messages to get neighborhood information. Using detailed simulations, we show over different scenarios that our protocol achieves similar or better reliability while inducing less packet transmission overhead than ODMRP, MAODV and PUMA which is DPUMA's predecessor. [ABSTRACT FROM AUTHOR]

In this paper, we address an optimization problem that arises in context of cache placement in sensor networks. In particular, we consider the cache placement problem where the goal is to determine a set of nodes in the network to cache/store the given data item, such that the overall communication cost incurred in accessing the item is minimized, under the constraint that the total communication cost in updating the selected caches is less than a given constant. In our network model, there is a single server (containing the original copy of the data item) and multiple client nodes (that wish to access the data item). For various settings of the problem, we design optimal, near-optimal, heuristic-based, and distributed algorithms, and evaluate their performance through simulations on randomly generated sensor networks. [ABSTRACT FROM AUTHOR]

Multiple-Input Multiple-Output (MIMO) antenna systems present a radical way to improve the performance of wireless communications. Such systems can be utilized in wireless ad hoc networks for improved throughput in several ways. A straightforward way is to regard the MIMO system just as a new link layer technology that provides a higher data rate. In this way, MIMO systems can be integrated with legacy Media Access Control (MAC) protocols such as 802.11 DCF. Recently, a few studies have proposed MAC protocols leveraging the advantages of MIMO systems in a different way. Those new MAC protocols enhance the network throughput by allowing simultaneous multiple communications at a lower rate rather than a single communication at a higher rate in a single collision domain. In this paper, we present a new MIMO MAC protocol for Ad hoc Networks namely MIMOMAN. MIMOMAN tries to further increase the network throughput by combining the two approaches, i.e., allowing simultaneous multiple communications at a higher data rate. It is beneficial especially in a heterogeneous setting where the number of antennas installed on each node varies. As a part of the protocol, MIMOMAN also suggests a new beamforming algorithm that allows spatial reuse among spatial multiplexing MIMO links. We investigate the performance of MIMOMAN through a simulation study. [ABSTRACT FROM AUTHOR]

Multi-hop wireless networks (such as ad-hoc or sensor networks) consist of sets of mobile nodes without the support of a pre-existing fixed infrastructure. For the purpose of scalability, ad-hoc and sensor networks may both need to be organized into clusters and require some protocols to perform common global communication patterns and particularly for broadcasting. In a broadcasting task, a source node needs to send the same message to all the nodes in the network. Some desirable properties of a scalable broadcasting are energy and bandwidth efficiency, i.e., message retransmissions should be minimized. In this paper, we propose to take advantage of the characteristics of a previous clustered structure to extend it to an efficient and scalable broadcasting structure. In this way, we build only one structure for both operations (organizing and broadcasting) by applying a distributed clustering algorithm. Our broadcasting improve the number of retransmissions as compared to existing solutions. Keywords: multi-hop wireless networks, self-organization, broadcasting. [ABSTRACT FROM AUTHOR]

To guarantee secure communication in wireless sensor networks, secret keys should be securely established between sensor nodes. Recently, a simple key distribution scheme has been proposed for pair-wise key establishment in sensor networks by Anderson, Chan, and Perrig. They defined a practical attack model for non-critical commodity sensor networks. Unfortunately, the scheme is vulnerable under their attack model. In this paper, we describe the vulnerability in their scheme and propose a modified one. Our scheme is secure under their attack model and the security of our scheme is proved. Furthermore, our scheme does not require additional communication overhead nor additional infrastructure to load potential keys into sensor nodes. Keywords: security, key management, wireless sensor networks [ABSTRACT FROM AUTHOR]

Mobile ad hoc networks (MANET) are dynamic networks formed on-the-fly as mobile nodes move in and out of each others' transmission ranges. In general, the mobile ad hoc networking model makes no assumption that nodes know their own locations. However, recent research shows that location-awareness can be beneficial to fundamental tasks such as routing and energy-conservation. On the other hand, the cost and limited energy resources associated with common, low-cost mobile nodes prohibits them from carrying relatively expensive and power-hungry location-sensing devices such as GPS. This paper proposes a mechanism that allows non-GPS-equipped nodes in the network to derive their approximated locations from a limited number of GPS-equipped nodes. In our method, all nodes periodically broadcast their estimated location, in term of a compressed particle filter distribution. Non-GPS nodes estimate the distance to their neighbors by measuring the received signal strength of incoming messages. A particle filter is then used to estimate the approximated location from the sequence of distance estimates. Simulation studies show that our solution is capable of producing good estimates equal or better than the existing localization methods such as APS-Euclidean. [ABSTRACT FROM AUTHOR]

In this paper, we characterize the performance of wireless ad-hoc networks through a capacity model which is based on explicit modeling of the interference across multiple routing paths. A set of elementary equations were developed to describe single-channel interference based on radio transmissions within a unit disk (UD) under random mobility conditions. The distinguishing feature of the model is that it introduces micro-models for three elementary sources of interference: inter-path, intra-path, and common origin interference. Simulation experiments found that the proposed session-based model generates throughput results consistent with existing approaches for modeling single path (SP) throughput performance within a unit area disk. However, we go one step further to use the SP throughput equations as the basis for developing a set of equations that model multiple path (MP) throughput performance. Mobility simulations of MP routing indicate that inter-path interference plays a dominant role in defining throughput performance, while intra-path interference and common origin interference have different effects as multi-user session and nodal densities change. [ABSTRACT FROM AUTHOR]

The application of Mobile Ad Hoc Network (MANET) technologies in the service of Intelligent Transportation Systems (ITS) has brought new challenges in maintaining communication clusters of network members for long time durations. Stable clustering methods reduce the overhead of communication relay in MANETs and provide for a more efficient hierarchical network topology. During creation of VANET clusters, each vehicle chooses a head vehicle to follow. The average number of cluster head changes per vehicle measures cluster stability in these simulations during the simulation. In this paper we analyze the effect of weighting two well-known clustering methods with the vehicle-specific position and velocity clustering logic to improve cluster stability over the simulation time. [ABSTRACT FROM AUTHOR]