Shuhui Yang

SMART: a scan-based movement-assisted sensor deployment method in wireless sensor networks

The efficiency of sensor networks depends on the coverage of the monitoring area. Although in general a sufficient number of sensors are used to ensure a certain degree of redundancy in coverage so that sensors can rotate between active and sleep modes, a good sensor deployment is still necessary to balance the workload of sensors. In a sensor network with locomotion facilities, sensors can move around to self-deploy. The movement-assisted sensor deployment deals with moving sensors from an initial unbalanced state to a balanced state. Therefore, various optimization problems can be defined to minimize different parameters, including total moving distance, total number of moves, communication/computation cost, and convergence rate. In this paper, we propose a Scan-based Movement-Assisted sensoR deploymenT method (SMART) that uses scan and dimension exchange to achieve a balanced state. SMART also addresses a unique problem called communication holes in sensor networks. Using the concept of load balancing, SMART achieves good performance especially when applied to uneven distribution sensor networks, and can be a complement to the existing sensor deployment methods. Extensive simulation has been done to verify the effectiveness of the proposed scheme.

On Connected Multiple Point Coverage in Wireless Sensor Networks

We consider a wireless sensor network consisting of a set of sensors deployed randomly. A point in the monitored area is covered if it is within the sensing range of a sensor. In some applications, when the network is sufficiently dense, area coverage can be approximated by guaranteeing point coverage. In this case, all the points of wireless devices could be used to represent the whole area, and the working sensors are supposed to cover all the sensors. Many applications related to security and reliability require guaranteed k-coverage of the area at all times. In this paper, we formalize the k-(Connected) Coverage Set (k-CCS/k-CS) problems, develop a linear programming algorithm, and design two non-global solutions for them. Some theoretical analysis is also provided followed by simulation results.

Scan-Based Movement-Assisted Sensor Deployment Methods in Wireless Sensor Networks

The efficiency of sensor networks depends on the coverage of the monitoring area. Although, in general, a sufficient number of sensors are used to ensure a certain degree of redundancy in coverage, a good sensor deployment is still necessary to balance the workload of sensors. In a sensor network with locomotion facilities, sensors can move around to self-deploy. The movement-assisted sensor deployment deals with moving sensors from an initial unbalanced state to a balanced state. Therefore, various optimization problems can be defined to minimize different parameters, including total moving distance, total number of moves, communication/computation cost, and convergence rate. In this paper, we first propose a Hungarian-algorithm-based optimal solution, which is centralized. Then, a localized scan-based movement-assisted sensor deployment method (SMART) and several variations of it that use scan and dimension exchange to achieve a balanced state are proposed. An extended SMART is developed to address a unique problem called communication holes in sensor networks. Extensive simulations have been done to verify the effectiveness of the proposed scheme.

Extended Dominating Set and Its Applications in Ad Hoc Networks Using Cooperative Communication

We propose a notion of an extended dominating set where each node in an ad hoc network is covered by either a dominating neighbor or several 2-hop dominating neighbors. This work is motivated by cooperative communication in ad hoc networks whereby transmitting independent copies of a packet generates diversity and combats the effects of fading. We first show the NP-completeness of the minimum extended dominating set problem. Then, several heuristic algorithms, global and local, for constructing a small extended dominating set are proposed. These are nontrivial extensions of the existing algorithms for the regular dominating set problem. The application of the extended dominating set in efficient broadcasting is also discussed. The performance analysis includes an analytical study in terms of approximation ratio and a simulation study of the average size of the extended dominating set derived from the proposed algorithms

Topology control in ad hoc wireless networks using cooperative communication

In this paper, we address the Topology control with Cooperative Communication (TCC) problem in ad hoc wireless networks. Cooperative communication is a novel model introduced recently that allows combining partial messages to decode a complete message. The objective of the TCC problem is to obtain a strongly-connected topology with minimum total energy consumption. We show that the TCC problem is NIP-complete and design two distributed and localized algorithms to be used by the nodes to set up their communication ranges. Both algorithms can be applied on top of any symmetric, strongly-connected topology to reduce total power consumption. The first algorithm uses a distributed decision process at each node that makes use of only 2-hop neighborhood information. The second algorithm sets up the transmission ranges of nodes iteratively, over a maximum of six steps, using only 1-hop neighborhood information. We analyze the performance of our approaches through extensive simulation.

Coverage issue in sensor networks with adjustable ranges

In this paper, we study the problem of maintaining sensing coverage by keeping a small number of active sensor nodes and a small amount of energy consumption in wireless sensor networks. This paper extends a result from [21] where only uniform sensing range among all sensors is used. We adopt an approach that allows non-uniform sensing ranges for different sensors. As opposed to the uniform sensing range node scheduling model in [21], two new energy-efficient models of different sensing ranges are proposed. Our objective is to minimize the overlapped sensing area of sensor nodes, thus to reduce the overall energy consumption by sensing to prolong the whole network?s life time, and at the same time to achieve the high ratio of coverage. Extensive simulation is conducted to verify the effectiveness of our node scheduling models.

Logarithmic Store-Carry-Forward Routing in Mobile Ad Hoc Networks

Two schools of thought exist in terms of handling mobility in mobile ad hoc networks (MANETs). One is the traditional connection-based model, which views node mobility as undesirable and tries to either remove (through recovery schemes) or mask (through tolerant schemes) the effect of mobility. The other is the mobility-assisted model, which considers mobility as a desirable feature, where routing is based on the store-carry-forward paradigm with random or controlled movement of mobile nodes (called ferries). It is well known that mobility increases the capacity of MANETs by reducing the number of relays in routing. Surprisingly, only two models, diameter hop count in the connection-based model and constant hop count in the mobility-assisted model, which correspond to two extremes of the spectrum, have been systematically studied. In this paper, we propose a new routing model that deals with message routing, as well as trajectory planning, of the ferries that carry the message. A logarithmic number of relays are enforced to achieve a good balance among several contradictory goals, including increasing network capacity, increasing ferry sharing, and reducing moving distance. The model considers the dynamic control of ferries in terms of the number of ferries, trajectory planning of ferries, and node communication and synchronization. The effectiveness of the proposed model is evaluated analytically, as well as through simulation

On multiple point coverage in wireless sensor networks

We consider a wireless sensor network consisting of a set of sensors deployed randomly. A point in the monitored area is covered if it is within the sensing range of a sensor. In some applications, when the network is sufficiently dense, area coverage can be approximated by guaranteeing point coverage. In this case, all the points of wireless devices could be used to represent the whole area, and the working sensors are supposed to cover all the sensors. Many applications related to security and reliability require guaranteed k-coverage of the area at all times. In this paper, we formalize the k-(connected) coverage set (k-CCSlk-CS) problems, develop a linear programming algorithm, and design two non-global solutions for them. Some theoretical analysis is also provided followed by simulation results

Efficient Broadcasting Using Network Coding and Directional Antennas in MANETs

In this paper, we consider the issue of efficient broadcasting in mobile ad hoc networks (MANETs) using network coding and directional antennas. Network coding-based broadcasting focuses on reducing the number of transmissions each forwarding node performs in the multiple source/multiple message broadcast application, where each forwarding node combines some of the received messages for transmission. With the help of network coding, the total number of transmissions can be reduced compared to broadcasting using the same forwarding nodes without coding. We exploit the usage of directional antennas to network coding-based broadcasting to further reduce energy consumption. A node equipped with directional antennas can divide the omnidirectional transmission range into several sectors and turn some of them on for transmission. In the proposed scheme using a directional antenna, forwarding nodes selected locally only need to transmit broadcast messages, original or coded, to restricted sectors. We also study two extensions. The first extension applies network coding to both dynamic and static forwarding node selection approaches. In the second extension, we design two approaches for the single source/single message issue in the network coding-based broadcast application. Performance analysis via simulations on the proposed algorithms using a custom simulator and NS-2 is presented.

ENERGY-EFFICIENT NODE SCHEDULING MODELS IN SENSOR NETWORKS WITH ADJUSTABLE RANGES

In this paper, we study the problem of maintaining sensing coverage by keeping a small number of active sensor nodes and using a small amount of energy consumption in wireless sensor networks. This paper extends a result from 22 where only uniform sensing range among all sensors is used. We adopt an approach that allows non-uniform sensing ranges for different sensors. As opposed to the uniform sensing range node scheduling model in 22, two new energy-efficient models with different sensing ranges are proposed. Our objective is to minimize the overlapped sensing area of sensor nodes, thus to reduce the overall energy consumption by sensing and communication to prolong the whole networks life time, and at the same time to achieve the high ratio of coverage. Extensive simulation is conducted to verify the effectiveness of our node scheduling models.