Hsu-Ruey Chang

Obstacle-Resistant Deployment Algorithms for Wireless Sensor Networks

Node deployment is an important issue in wireless sensor networks (WSNs). Sensor nodes should be efficiently deployed in a predetermined region in a low-cost and high-coverage-quality manner. Random deployment is the simplest way to deploy sensor nodes but may cause unbalanced deployment and, therefore, increase hardware costs and create coverage holes. This paper presents the efficient obstacle-resistant robot deployment (ORRD) algorithm, which involves the design of a node placement policy, a serpentine movement policy, obstacle-handling rules, and boundary rules. By applying the proposed ORRD, the robot rapidly deploys a near-minimal number of sensor nodes to achieve full sensing coverage, even though there exist unpredicted obstacles with regular or irregular shapes. Performance results reveal that ORRD outperforms the existing robot deployment mechanism in terms of power conservation and obstacle resistance and, therefore, achieves better deployment performance.

Energy-aware node placement, topology control and MAC scheduling for wireless sensor networks

In the WSNs, the nodes closer to the sink node have heavier traffic load for packet forwarding because they do not only collect data within their sensing range but also relay data for nodes further away. The unbalanced power consumption among sensor nodes may cause network partition. This paper proposes efficient node placement, topology control, and MAC scheduling protocols to prolong the sensor network lifetime, balance the power consumption of sensor nodes, and avoid collision. Firstly, a virtual tree topology is constructed based on Grid-based WSNs. Then two node-placement techniques, namely Distance-based and Density-based deployment schemes, are proposed to balance the power consumption of sensor nodes. Finally, a collision-free MAC scheduling protocol is proposed to prevent the packet transmissions from collision. In addition, extension of the proposed protocols are made from a Grid-based WSN to a randomly deployed WSN, enabling the developed energy-balanced schemes to be generally applied to randomly deployed WSNs. Simulation results reveal that the developed protocols can efficiently balance each sensor nodes power consumption and prolong the network lifetime in both Grid-based and randomly deployed WSNs.

OFRD:Obstacle-Free Robot Deployment Algorithms for Wireless Sensor Networks

Node deployment is an important issue in wireless sensor networks (WSNs). Sensor nodes should be efficiently deployed in a predetermined region in a low cost and high coverage quality manner. Random deployment is the simplest way for deploying sensor nodes but may cause the unbalanced deployment and therefore increase the hardware cost. This paper presents an efficient obstacle-free robot deployment algorithm, called OFRD which involves the design of node placement policy, snake-like movement policy, and obstacle handling rules. By applying the proposed OFRD, the robot rapidly deploys near-minimal number of sensor nodes to achieve full sensing coverage even though there exist unpredicted obstacles. Performance results reveal that OFRD outperforms the existing robot deployment mechanism in terms of power conservation and obstacle resistance, and, therefore achieves a better deployment performance.

Adaptive role switching protocol for improving scatternet performance in Bluetooth radio networks

Bluetooth has been considered as a high potential technology for providing wireless communication in a home-networking environment. In a Bluetooth network, it is difficult to control or predefine a scatternet structure because that the scatternet is formed using a distributed procedure, with the master and slave connected at random. A badly structured scatternet exhibits the following characteristics. Firstly, too many bridges in the scatternet will create a guard slot overhead associated with bridge switching among the participated piconets, increasing the probability of packet loss. Secondly, too many piconets in a communicative range will cause packet collision and thus degrade the performance. Unnecessary piconets also lengthen the routing path and transmission delay. This work proposes a distributed scatternet reconstruction protocol for dynamically reorganizing the scatternet topology. By applying the role switching operation, the unnecessary bridges and the piconet can be dynamically removed and hence, improve the packet error rate, save guard slots, and reduce the average routing length. Experimental results reveal that the proposed protocol significantly improves the performance of a Bluetooth scatternet

WSN19-2: Energy-Balanced Deployment and Topology Control for Wireless Sensor Networks

In wireless sensor networks (WSNs), nodes closer to the sink node have heavier traffic load for packet forwarding. The unbalanced power consumption among sensor nodes may cause network partition. This paper proposes efficient node placement and topology control protocols to balance the power consumption of sensor nodes. Firstly, a virtual tree topology is constructed based on Grid-based WSNs. Then two node placement techniques, namely Distance-based and Density-based deployment schemes are proposed to balance the power consumption of sensor nodes. Finally, extension of the proposed protocols are made from a Grid-based WSN to a randomly deployed WSN, making the developed energy-balanced schemes can be generally applied to randomly deployed WSNs. Simulation results reveal that the developed protocols can efficiently balance each sensor nodes power consumption and prolong the network lifetime in both Grid-based and randomly deployed WSNs.

Power control and fairness MAC mechanisms for 802.11 WLANs

Exploiting spatial reuse opportunities will allow more parallel transmissions and improve the throughput of wireless networks. Power control is one of the major mechanisms used to exploit both spatial reuse and power conservation opportunities. Increasing the transmitting power will prevent the receiver from interference but it will consume power and create additional interference to other communicating stations. On the contrary, reducing the transmitting power will reduce the interference to other communicating pairs and lessen the senders power consumption, but it will result to a lower signal to noise ratio (SNR) at receivers side. This article presents a power control MAC protocol that exploits the spatial reuse and power conservation opportunities for 802.11 Wireless LAN. The proposed protocol evaluates the interference and adopts a power control mechanism on both the sender and receiver sides to allow more communications to proceed simultaneously. In addition, a fairness control mechanism to reduce the average communication delay and alleviate the packet lost phenomenon is also proposed. Performance results reveal that the proposed protocol improves the throughput and power consumption of WLAN while the fairness among communicating pairs can also be maintained.

On Providing Temporal Full-Coverage by Applying Energy-Efficient Hole-Movement Strategies for Mobile WSNs

This paper considers a mobile WSN that contains a big hole but there exists no redundant mobile sensor to heal the hole. To achieve the temporal full-coverage purpose or enhance the tracking quality, three distributed algorithms are proposed for moving the existing big coverage hole to a predefined location. Firstly, the sink chooses a promising direction for hole-movement. Then the basic, forward-only and any-direction movement mechanisms are proposed to move the hole along the promising direction in a manner of minimizing the total power consumption or balancing the energy consumption of the given WSN. Simulation results reveal that the proposed hole-movement mechanisms enhance the coverage of WSN and balance the energy consumption of mobile sensor nodes.

PCF: on exploiting spatial reuse and power conservation opportunities with power control and fairness mechanism for 802.11 WLAN

Exploiting spatial reuse opportunities allows more parallel transmissions and improve the throughput of wireless networks. Power control is one of the major mechanisms used to exploit both spatial reuse and power conservation opportunities. Increasing the transmitting power prevents the receiver from interference but consume power and create additional interference to other communicating nodes. On the contrary, reducing the transmitting power reduces the interference to other communicating pairs and save senders power consumption, but result a lower SNR (signal to noise ratio) at receiver side. This article presents power control MAC protocol to exploit the spatial reuse and power conservation opportunities for 802.11 wireless LAN. The proposed protocol evaluates the interference and adopts power control mechanism on both sender and receiver sides, trying to allow more communications proceeding simultaneously. In addition, a fairness control mechanism is also proposed to reduce the average communication delay and alleviate the packet lost phenomenon. Performance results reveal that the proposed protocol improves the throughput and power consumption of WLAN while the fairness among communicating pairs can be maintained.

On improving network connectivity by power-control and code-switching schemes for multihop packet radio networks

Packet radio network (PRN) consists of low or even no mobility stations each assigned with a code to prevent transmission from collision. A PRN with strong connectivity will help to reduce the route length and provide more alternatives for routing, improving the overall throughput and end-to-end delay. With power control mechanism, each station could be assigned with a power level to change the neighborhood relation and improve network connectivity. Assigning high transmitting power level to a station can enhance the network connectivity but may increase the number of neighbors, raising collision problem for parallel transmissions among neighbors. How to assign appropriate power level to improve the network connectivity with a constraint of limited codes is one of the most important issues in PRNs. Given a network topology and a set of codes that has been assigned to stations, the proposed power control and code switching mechanism assigns each station with a power level and a code to improve the network connectivity. Based on the matrix-based operation, the power control and code switching metrics in network connectivity problem are generally identified and efficiently resolved. Simulation study reveals that the proposed mechanism increases network throughput and provides a variety of route selection thus improves the performance of a given PRN.