Catálogo de publicaciones - libros

Field surveillance is one of the most important applications for wireless sensor networks. Many sensors are deployed in a region of concern to detect any potential targets. On the contrary, intelligent target looks for the best path to traverse the sensing field for fear of being detected and leads to defunct surveillance. In this paper, we focus on how an intelligent target traverses the sensing field. We model this traversing problem, design, implement and evaluate a number of path-finding algorithms. Different from previous works which assume complete information of the sensing field, we assume that the target only can detect part of the sensor network in its detection radius. This makes the proposed methods more practical. Extensive experiments with a target and a sensor network confirm the validity of the approach.

In this paper, an efficient Fibonacci series based hierarchical protocol-HFTM (Hierarchical Fibonacci Tree Multicast) is proposed for application-layer multicast. It adopts the idea of layer and cluster to construct multicast group members into a hierarchical architecture. During the cluster formation, it considers the underlying network properties to reduce packet delivering on costly links. In each cluster, a Fibonacci multicast tree is constructed by recursively partitioning the member sequence into two halves with different length. Moreover, the size of cluster is taken into account in order to obtain a balanced architecture. The considering of underlying network properties and the construction of Fibonacci multicast tree improve the delay performance of the novel protocol. The simulation shows that HFTM is an efficient and scalable application-layer multicast protocol.

It is now commonly accepted that the unit disk graph used to model the physical layer in wireless networks does not reflect real radio transmissions, and that the lognormal shadowing model better suits to experimental simulations. Previous work on realistic scenarios focused on unicast, while broadcast requirements are fundamentally different and cannot be derived from unicast case. Therefore, broadcast protocols must be adapted in order to still be efficient under realistic assumptions. In this paper, we study the well-known multipoint relay protocol (MPR). In the latter, each node has to choose a set of neighbors to act as relays in order to cover the whole 2-hop neighborhood. We give experimental results showing that the original method provided to select the set of relays does not give good results with the realistic model. We also provide three new heuristics in replacement and their performances which demonstrate that they better suit to the considered model. The first one maximizes the probability of correct reception between the node and the considered relays multiplied by their coverage in the 2-hop neighborhood. The second one replaces the coverage by the average of the probabilities of correct reception between the considered neighbor and the 2-hop neighbors it covers. Finally, the third heuristic keeps the same concept as the second one, but tries to maximize the coverage level of the 2-hop neighborhood: 2-hop neighbors are still being considered as uncovered while their coverage level is not higher than a given coverage threshold, many neighbors may thus be selected to cover the same 2-hop neighbors.

Efficient and reliable dissemination of information over a large area is a critical ability of a sensor network for various reasons such as software updates and transferring large data objects (e.g., surveillance images). Thus efficiency of wireless broadcast is an important aspect of sensor network deployment. In this paper, we study FBcast, a new broadcast protocol based on the principles of modern erasure codes. We show that our approach provides high reliability, often considered critical for disseminating codes. In addition FBcast offers limited data confidentiality. For a large network, where every node may not be reachable by the source, we extend FBcast with the idea of repeaters to improve reliable coverage. Simulation results on TOSSIM show that FBcast offers higher reliability with lower number of retransmissions than traditional broadcasts.

Wireless mesh networks have emerged to be one of the promising applications of ad hoc networks. The idea of installing multiple radio interfaces at each mesh router allows a mesh network to better utilize the available wireless bandwidth, but at the same time complicates the issue of route selection. In this paper, we propose a novel metric that measures the bandwidth and cost ratio of each route. Based on this metric, a Cost-Aware Route Selection (CARS) scheme is proposed to improve the overall throughput of a mesh network. The simulation results confirm that our scheme is able to better utilize the limited wireless resource and improves the overall network throughput by more than 95% with different types of traffic and communication patterns when it is compared against the past route selection schemes.

This paper presents the route metric, the Expected Cumulative Service Latency (ECSL), which allow any routing protocol to select a route with the high-throughput in the multi-rate wireless ad hoc networks. The ECSL route metric finds a route with minimal end-to-end forwarding time expected to successfully deliver a packet to the destination. In such networks, existing route metrics for route discovery only use the link quality metric based on the expected amount of medium time it would take by successfully transmitting a packet. Thus, in these schemes, the current state of traffic in network is not taken into account. Therefore, this may easily result in the congested network. In addition, the application has no way to improve its performance under a given network traffic condition. In this paper, we propose the route metric, the expected end-to-end latency that is estimated with the number of packets waiting for transmission in queue at relay nodes and the link transmission time as well as a new routing protocol using the proposed metric. The performance of the proposed route metric is evaluated by OPNET simulator. We show that the performance of the AODV routing protocol using the ECSL route metric outperforms that of the routing protocols using other existing route metrics in multi-rate ad hoc network.

In this study, the joint power control and scheduling problem in a multihop TD/CDMA MANET is investigated. A cluster based architecture is adopted to provide scalability and centralized control within clusters, and the corresponding power control and scheduling schemes are derived to maximize a network utility function and guarantee the minimum rate required by each traffic session. Because the resulted optimal power control suggests that the scheduled nodes transmit with full power while other nodes remain silent, the joint power control and scheduling problem is reduced to a scheduling problem. Proportional fair scheduling is selected to achieve the balance between throughput and fairness. The multi-link version of the proportional fair scheduling algorithms for multihop MANET are proposed. In addition, a generic token counter mechanism is employed to satisfy the minimum rate requirements. Service differentiation is also achieved by ensuring different minimum rate for different traffic sessions. Approximation algorithms are suggested to reduce the computational complexity. In networks that are lack of centralized control, distributed scheduling algorithms are also derived and fully distributed implementation is provided. Simulation results demonstrate the effectiveness of the proposed schemes.

In this paper, we focus on the intra-cluster information exchange problem and proposed some novel solutions. Firstly, a cluster model is presented and some algorithms based on it are proposed, such as routing, flooding, cluster head relaying and network coding algorithm. The theoretical analysis and simulation comparison of these algorithms are shown subsequently. We find that network coding algorithm allows to realize significant energy and time savings, when each node of the cluster is a source that wants to transmit information to all other cluster member nodes. Energy efficiency directly affects battery life, and delay time is a very important network performance, thus both are critical design parameters in wireless ad hoc sensor networks. Further more, the network coding algorithm we proposed are efficient and implementable. We analyze theoretical cases in detail, and use the packet level simulation.

Service discovery is expected to be a crucial feature for the usability of MANETs(mobile ad-hoc networks). However, service discovery protocols existing nowadays are generally separated from backbone construction schemes usually performing in network layer in MANETs. Recognizing this problem, we propose a FNSCSDP(Forward Node Selection based Cross-layer Service Discovery Protocol) for MANETs, which makes use of periodically hello packets used in backbone construction schemes to facilitate service discovery tasks. When forwarding service request packets, FNSCSDP deliberately selects some nodes that should forward the service request packet. Those nodes are selected basing on local topology information gathered from hello packets and history information piggybacking in service request packets. Hence, all nodes that are at most 2-hop away from the current node will be able to receive the service request packet. Simulations show that FNSCSDP outperforms a well-known service discovery protocol GSD in packet overhead and promptness.

MANETs(Mobile Ad-Hoc Network) are temporary networks composed of many autonomous nodes. Service discovery is the technology of finding services matching one’s needs in the network, which is crucial to the usability of MANETs. Many service discovery protocols for MANETs have been proposed, but no comprehensive comparative studies have been made. Hence, some typical service discovery protocols are analyzed and compared. The advantages and drawbacks of each protocol are analyzed. The paper provides a perspective overview on service discovery protocols for MANETs.