Neng-Chung Wang

Efficient Cluster Head Selection Methods for Wireless Sensor Networks

The past few years have witnessed increased in the potential use of wireless sensor network (WSN) such as disaster management, combat field reconnaissance, border protection and security surveillance. Sensors in these applications are expected to be remotely deployed in large numbers and to operate autonomously in unattended environments. Since a WSN is composed of nodes with nonreplenishable energy resource, elongating the network lifetime is the main concern. To support scalability, nodes are often grouped into disjoint clusters. Each cluster would have a leader, often referred as cluster head (CH). A CH is responsible for not only the general request but also assisting the general nodes to route the sensed data to the target nodes. The power-consumption of a CH is higher then of a general (non-CH) node. Therefore, the CH selection will affect the lifetime of a WSN. However, the application scenario contexts of WSNs that determine the definitions of lifetime will impact to achieve the objective of elongating lifetime. In this study, we classify the lifetime into different types and give the corresponding CH selection method to achieve the life-time extension objective. Simulation results demonstrate our study can enlarge the life-time for different requests of the sensor networks.

A dual-Hamiltonian-path-based multicasting strategy for wormhole-routed star graph interconnection networks

Multicast is an important collective communication operation on multicomputer systems, in which the same message is delivered from a source node to an arbitrary number of destination nodes. The star graph interconnection network has been recognized as an attractive alternative to the popular hypercube network. In this paper, we first address a dual-hamiltonian-path-based routing model with two virtual channels based on two hamiltonian paths (HPs) and a network partitioning strategy for wormhole-routed star graph networks. Then, we propose three efficient multicast routing schemes on basis of such a model. All of the three proposed schemes are proved deadlock-free. The first scheme, network-selection-based dual-path routing, selects subnetworks that are constructed either by the first HP or by the second HP for dual-path routing. The second one, optimum dual-path routing, selects subnetworks with optimum routing path for dual-path routing. The third scheme, two-phase optimum dual-path routing, includes two phases, source-to-relay and relay-to-destination. Finally, experimental results are given to show that our proposed three routing schemes outperform the unicast-based, the HP, and the single-HP-based dual-path routing schemes significantly.

A multi-path QoS multicast routing protocol with slot assignment for mobile ad hoc networks

Mobile multimedia applications have recently generated much interest in mobile ad hoc networks (MANETs) supporting quality-of-service (QoS) communications. Due to the limited bandwidth of a wireless node, a QoS multicast routing is often blocked if there is not a single multicast tree with the requested bandwidth, even when there is sufficient bandwidth in the network to support the call. In this paper, a multi-path QoS multicast routing (MQMR) protocol for MANETs is proposed. The scheme offers dynamic time slot control using a multi-path tree (or a uni-path tree) to meet the bandwidth requirements of a call. The final multi-path QoS multicast tree meets the QoS requirements, and the aggregate bandwidth of the paths meets the bandwidth requirements of a call. To avoid the hidden terminal problem or insufficient bandwidth in the bandwidth reservation process, each destination uses a decision rule. Moreover, a bandwidth reservation scheme is used for selecting the reserved time slots on each node in the multi-path QoS multicast tree. Simulation results demonstrate the effectiveness of MQMR in reducing network blocking and improving the call success ratio.

A reliable QoS aware routing protocol with slot assignment for mobile ad hoc networks

A mobile ad hoc network (MANET) is a collection of mobile hosts that form a temporary network on the fly without using any fixed infrastructure. Recently, the explosive growth in the use of real-time applications on mobile devices has resulted in new challenges to the design of protocols for MANETs. Chief among these challenges to enable real-time applications for MANETs is incorporating support for quality of service (QoS), such as bandwidth constraints. However, MANETs having a high ratio of topology change make routing especially unstable; making stability is an important challenge, especially for routing having a quality of service provision. In this paper, we propose a reliable multi-path QoS routing (RMQR) protocol with a slot assignment scheme. In this scheme, we examine the QoS routing problem associated with searching for a reliable multi-path (or uni-path) QoS route from a source node to a destination node in a MANET. This route must also satisfy certain bandwidth requirements. We determine the route expiration time between two connected mobile nodes using global positioning system (GPS). Then, two parameters, the route expiration time and the number of hops, are used to select a routing path with low latency and high stability. Simulation results show that the proposed RMQR protocol have some outstanding properties when compared with Lins [Lin C-R. On-demand QoS routing in multihop mobile networks. In: Proceedings of the twentieth annual joint conference of the IEEE computer and communications societies (INFOCOM), vol. 3(22-26), 2001, p. 1735-44], Liaos [Liao W-H, Tseng Y-C, Wang S-L, Sheu J-P. A multi-path QoS routing protocol in a wireless mobile Ad Hoc network. Telecommunication Systems 2002;19(3-4):329-47], and Chens [Chen Y-S, Tseng Y-C, Sheu J-P, Kuo P-H. An on-demand, link-state, multi-path QoS routing in a wireless mobile Ad-Hoc network. Computer Communications 204;27(1):27-40] protocols.

Improving Low-Energy Adaptive Clustering Hierarchy Architectures with Sleep Mode for Wireless Sensor Networks

A wireless sensor network (WSN) is composed of sensor nodes whose energy is battery-powered. Therefore, the energy is limited. This paper aims to improve the energy efficiency of sensor nodes in order to extend the lifetime of WSNs. In this paper, we propose four new hierarchical clustering topology architectures: random cluster head and sub-cluster head (RCHSCH), random cluster head and max energy sub-cluster head (RCHMESCH), random cluster head and sub-cluster head with sleep mode (RCHSCHSM) and random cluster head and max energy sub-cluster head with sleep mode (RCHMESCHSM). Our proposed architectures involve three-layers and are based on low-energy adaptive clustering hierarchy (LEACH) architecture. Notably, RCHSCH can improve upon cluster head death within the LEACH architecture. In addition, we develop a sleep mode for sensor nodes based on correlations among sensor data within sub-clusters in RCHSCHSM. Thus, we can reduce the energy consumption of the sensor node and increase energy efficiency. From the simulation results, our proposed RCHSCH, RCHMESCH, RCHSCHSM and RCHMESCHSM architectures perform better than the LEACH architecture in terms of initial node death, the number of nodes alive and total residual energy. Furthermore, we find the performance of RCHMESCHSM architecture to be optimal in the set of all available architectures.

Power-aware data dissemination protocol for grid-based wireless sensor networks with mobile sinks

In wireless sensor networks (WSNs), sink mobility has been drawing more and more attention in recent years. Some approaches suggest that mobile sinks repeatedly propagate packets to notify the potential sources of their latest location information. As a result, frequent location updates from multiple sinks introduce both increased transmission traffic and rapid power expenditure. In order to reduce power consumption and minimise the overhead of frequently propagating packets, the authors propose a power-aware data dissemination (PADD) protocol for grid-based WSNs with mobile sinks. Rather than propagate the query messages from each sink to all sensor nodes to establish data forwarding information, a source constructs a grid structure beforehand so that only the dissemination nodes located at grid points need to acquire forwarding information. A properly grid cell size is determined to ensure that a dissemination node can directly communicate each other with its eight neighbouring dissemination nodes. As a result, a message can traverse not only vertically or horizontally but diagonally as well. Besides, dissemination nodes with the most residual energy are selected for forwarding query and disseminating data to evenly distribute energy load in the sensor field. Simulation results demonstrate the effectiveness of PADD in reducing the energy consumption and prolonging the network lifetime.

Performance of a Hierarchical Cluster-Based Wireless Sensor Network

This paper proposes a clustering scheme to improve energy efficiency for cluster-based wireless sensor networks (WSNs). In order to reduce the energy dissipation of transmitting sensing data at each sensor, the proposed fixed algorithm uniformly divides the sensing area into clusters where the cluster head is deployed in the center of the cluster area. Moreover, to improve the energy efficiency in the cluster based on the fixed clustering, the cluster head is elected by the LEACH scheme. Simulation results show that the proposed low-energy fixed clustering (LEFC) definitely reduces the energy consumption of the sensors and outperform LEACH with more 60% network lifetime.

A Fuzzy-Based Transport Protocol for Mobile Ad Hoc Networks

A mobile ad hoc network (MANET) is a dynamically reconfigurable wireless network that does not have a fixed infrastructure. Because this kind of network uses wireless connections for communication, traditional transport protocol for wired networks is not suitable for MANETs. In this paper, we propose an improved transport protocol (ITP) to enhance the efficiency of the transport protocol in MANETs. In ITP, we use a rate-based transmission scheme with fuzzy logic control to tune the proper data rate. ITP gets the MAC layer information and uses a fuzzy logic controller to estimate the appropriate data rate for transmission. Then ITP uses a feedback scheme to adjust data flow by receiving a feedback packet. The difference between traditional TCP and ITP is that ITP adjusts its transmission rate using the received packet instead of the acknowledgments or lost packets. Simulation results show that the proposed ITP outperforms TCP and ATP.

Task migration in all-port wormhole-routed 2D mesh multicomputers

In a mesh multicomputer, submeshes are scheduled to perform jobs according to some processor allocation schemes, each job assigned to occupy processors of one submesh with an appropriate size. In order to assign the region for the incoming jobs, a task compaction is needed to produce a larger contiguous free region. The overhead of task compaction is primarily relied on designing an efficient task migration scheme. In this paper, we aim at the 2D mesh multicomputers with supporting wormhole routing in all-port communication model as the target machine. First, a certain and a relieved constraints between two submeshes for task migration are proposed. We next propose two task migration schemes following one of the constraints in 2D mesh multicomputers. We also analyze and discuss the routing phases for task migration. Finally, we compare the proposed task migration schemes via performance analysis.

Grid-Based Data Aggregation for Wireless Sensor Networks

In a wireless sensor network (WSN), a huge number of sensor nodes with limited battery power are generally deployed over a severe field to gather data. It is impractical to recharge or replace the batteries of the sensor nodes in such a severe environment. Therefore, an energy efficient protocol is essential to maximize the lifetimes of nodes. In this paper, we propose a grid-based data aggregation scheme (GBDAS) for WSNs. We partition the whole sensor field into a 2-D logical grid of cells. In each cell, the node with the most residual energy takes turn to be the cell head, responsible for aggregating its own data with the data sensed by the other sensor nodes of the cell, and then transmitting it out. In order to reduce the data transmissions to the base station (BS), we further link each cell head to form a chain. In the chain, the cell head with the most residual energy is designated in turn as the chain leader. Aggregated data moves from head to head along the chain, and finally the chain leader transmits to the BS. In GBDAS, only the cell heads need to transmit data toward the BS. Therefore, the data transmissions to the BS substantially decrease. Besides, the cell heads and chain leader are designated in turn according to the energy level so that the energy depletion of nodes is evenly distributed. Simulation shows that GBDAS outperforms Direct and PEGASIS.