Shih-Chieh Lee

Relay reduction and disjoint routes construction for scatternet over Bluetooth radio system

Bluetooth is a new technology for low-cost, low-power, and short-range wireless communication. By constructing a piconet, Bluetooth device establishes link and communicates with other device in a master-slave manner. Relay is a Bluetooth device that joins two or more piconets and forwards data from one piconet to another, providing multi-hop (or inter-piconet) communication services. In a Bluetooth scatternet, the number of relays and the degree of each relay are factors that significantly affect the performance of entire network. Unnecessary relays raise the difficulty of scheduling, leading to frequent packet loss. Relay switching among several piconets in turns also creates guard time overhead and increases the transmission delay. This study presents an effective protocol that can dynamically adjust the network topology by reducing the unnecessary relays. An efficient scatternet environment thus can be constructed with characteristics of connected, high bandwidth utilization and low maintenance cost. Additionally, a routing protocol is developed to reduce the path length and generate two disjoint routes for any pair of source and destination devices located in different piconets. Experimental results demonstrate that the proposed protocols perform well in terms of route length, bandwidth consumption, and transmission delay.

RGP: Active Route Guiding Protocol for Wireless Sensor Networks with Obstacles

In wireless sensor networks, a geographic region without functionality of sensing and communication can be generally treated as an obstacle, which significantly impacts the performance of existing location-based routing. In a WSN, an obstacle can be dynamically formed due to unbalanced deployment, failure or power exhaustion of sensors, animus interference, or physical obstacles such as mountains or buildings. This paper proposes a novel algorithm, namely RGP, to enable the existing location-based routing protocols resisting obstacles. Applying the proposed RGP, border nodes that surround the obstacles will actively establish a forbidden region for concave obstacles and make the obstacle information transparent. Then packets will be guided to overcome the obstacle and move along the shortest path from the encountered border node to the sink node. Simulation results show that RGP creates low overhead and significantly reduces the average route length and therefore improves the energy consumption and end-to-end delay for a wireless sensor network with obstacles

ZBP: A Zone-Based Broadcasting Protocol for Wireless Sensor Networks

Wireless Sensor Networks (WSNs) have been widely used in motoring and collecting interests of environment information. Packet flooding or broadcasting is an essential function for establishing a communication path from sink node to a region of sensor nodes. However, flooding operation consumes power and bandwidth resources and raises the packet collision and contention problems, which reduce the success rate of packet transmissions and consume energy. This article proposes an efficient broadcasting protocol to reduce the number of sensor nodes that forward the query request, hence improves the packet delivery rate and saves bandwidth and power consumptions. Sensor node that received the query request will dynamically transfers the coordinate system according to the zone-ID of source node and determines whether it would forward the request or not in a distributed manner. Compared with the CBM and traditional flooding operation, experimental results show that the proposed zone-based broadcasting protocol decreases the bandwidth and power consumptions, reduces the packet collisions, and achieves high success rate of packet broadcasting.

A Location-Aware Routing Protocol for the Bluetooth Scatternet

Bluetooth is a most promising technology for the wireless personal area networks and its specification describes how to build a piconet. Though the construction of scatternet from the piconets is left out in the specification, some of the existing solutions discuss the scatternet formation issues and routing schemes. Routing in a scatternet, that has more number of hops and relay nodes increases the difficulties of scheduling and consumes the bandwidth and power resources and thereby impacts on the performance of the entire network. In this paper, a novel routing protocol (LARP) for the Bluetooth scatternet is proposed, which reduces the hop counts between the source and the destination and reconstructs the routes dynamically using the location information of the Bluetooth devices. Besides, a hybrid location-aware routing protocol (HLARP) is proposed to construct the shortest routes among the devices with or without having the location information and degenerate the routing schemes without having any location information. Experimental results show that our protocols are efficient enough to construct the shortest routing paths and to minimize the transmission delay, bandwidth and power consumption as compared to the other protocols that we have considered.

ZBP: a zone-based broadcasting protocol for wireless sensor networks

Wireless sensor networks (WSNs) have been widely used in monitoring and collecting information. Packet flooding or broadcasting is an essential function for establishing a communication path from the sink node to a region of sensor nodes. However, flooding operation consumes power and bandwidth resources and raises the packet collision and contention problems, which reduce the success rate of packet transmissions and consume energy. This article proposes an efficient broadcasting protocol to reduce the number of sensor nodes that forward the query request, hence improving the packet delivery rate and saving bandwidth and power consumptions. The sensor node that received the query request dynamically transfers the coordinate system according to the zone-ID of the source node and determines whether it would forward the request or not in a distributed manner. Compared with a traditional flooding operation, experimental results show that the proposed zone-based broadcasting protocol decreases the bandwidth and power consumptions, reduces the packet collisions, and achieves a high success rate of packet broadcasting.

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

Bluetooth is a low-power, low-cost, and short-range wireless technology. A well structured scatternet, with the appropriate number of piconets and bridges for a specific traffic pattern, increases the performance of a Bluetooth network. However, the structure of a scatternet is difficult to control or predefine because the scatternet is formed using a distributed procedure, with the master and slaves of each piconet connected at random. The participation of mobile Bluetooth devices in a scatternet at different times also increases the difficulty of maintaining a good structure. A badly structured scatternet exhibits the following characteristics: too many bridges in the scatternet creates a guard slot overhead associated with bridge switching among the participating piconets, increasing the probability that a packet is lost; too many piconets in a communicative range causes packet collision and thus degrades the performance; unnecessary piconets also lengthen the routing path, delaying the transmission of packets from source to destination. The paper proposes a distributed scatternet reconstruction protocol for dynamically reorganizing the scatternet. Unnecessary bridges and piconets can be dynamically removed by applying a role switching operation, improving the packet error rate, saving guard slots, and reducing the average routing length. By experiment, it is shown that the proposed protocol improves the data transmission performance of a Bluetooth scatternet.

LARP: a novel routing protocol for the Bluetooth scatternet

In this paper we design an efficient location aware routing protocol (LARP) for the Bluetooth scartternet. Taking advantages of the location information of all nodes, LARP reconstructs the routing path dynamically and minimizes the number of hops between the source and the destination of the scatternet. Besides, the paper also presents a hybrid routing protocol (HLARP), which minimizes the routing path for the scatternet, taking location information of some nodes. Experimental results show that both of our protocols are efficient enough to construct the shortest routing paths over a multi-hop scatternet and bandwidth and power consumption are least as compared to other routing protocols that we have considered.

An Optimal Scheduling Algorithm for Maximizing Throughput in WiMAX Mesh Networks

The WiMAX mesh network (WMN) architecture is defined in the IEEE 802.16 standard for increasing network coverage and improving communication performance. In the past few years, several greedy or heuristic algorithms have been proposed to cope with the scheduling problem in WMNs. However, their performance highly depends on the network topology and bandwidth requests, and they do not achieve optimal performance in all cases. This paper proposes an optimal scheduling algorithm called the scheduling algorithm with dynamic programming approach (SADP), which exploits the opportunities of spatial reuse and maximizes the network throughput based on the network topology and the uplink bandwidth requests of each subscriber station. In addition, a heuristic scheduling algorithm (HSA) is proposed to reduce the computing complexity. The performance results were approximate to the optimal results. The simulation study reveals that the proposed SADP provides the WMN with maximal throughput and shortest transmission time, and the proposed HSA likely achieves the optimal results.

PAMP: a power-aware multicast protocol for Bluetooth radio systems

Bluetooth is a low power, low cost, and short-range wireless technology. A piconet consists of a master and up to seven slaves. Devices that desire to receive data from the same source construct a multicast group, sharing multicast communication services. A piconet may consist of member and non-member devices of a multicast group, causing non-member devices to consume power to overhear the multicast message. For those members that belong to different piconets, a multi-hop communication path is required, hence increasing the delay time of a multicast service and causing more non-member devices to participate in the multicast tree. The paper develops a power-aware multicast protocol (PAMP) for constructing an efficient multicast tree. By collecting members into the same piconet, the constructed multicast tree has characteristics of fewest non-member devices, smallest tree level, and proper role assignments to members. Experimental results show that PAMP provides an efficient multicast service with low power consumption and small delay.

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.