Chyi-Ren Dow

A study of recent research trends and experimental guidelines in mobile ad-hoc network

This work investigates and analyzes recent research trends and presents experimental guidelines on MANETs. More than 1,300 MANET related papers in IEEE/IEE Electronic Library (IEL Online) from 1998 to 2003 were collected and surveyed. The research trends, qualitative analysis and simulation guidelines from fifteen major MANET issues are investigated to assist the user in conducting MANET research. Based on recent six year trends we found that some issues such as routing and power management attracted much attention. We also found that some issues have potential study value, such as IP addressing and fault tolerance. In the qualitative analysis, we found that some factors such as scalability, stability, and reliability attracted much attention in major MANET issues. The essential simulation metrics for various MANET issues are identified and listed for experimental guidelines. The analysis results demonstrate the utilization trends for various MANET simulators.

A generalized processor mapping technique for array redistribution

In many scientific applications, array redistribution is usually required to enhance data locality and reduce remote memory access in many parallel programs on distributed memory multicomputers. Since the redistribution is performed at runtime, there is a performance trade-off between the efficiency of the new data decomposition for a subsequent phase of an algorithm and the cost of redistributing data among processors. In this paper, we present a generalized processor mapping technique to minimize the amount of data exchange for BLOCK-CYCLIC(kr) to BLOCK-CYCLIC(r) array redistribution and vice versa. The main idea of the generalized processor mapping technique is first to develop mapping functions for computing a new rank of each destination processor. Based on the mapping functions, a new logical sequence of destination processors can be derived. The new logical processor sequence is then used to minimize the amount of data exchange in a redistribution. The generalized processor mapping technique can handle array redistribution with arbitrary source and destination processor sets and can be applied to multidimensional array redistribution. We present a theoretical model to analyze the performance improvement of the generalized processor mapping technique. To evaluate the performance of the proposed technique, we have implemented the generalized processor mapping technique on an IBM SP2 parallel machine. The experimental results show that the generalized processor mapping technique can provide performance improvement over a wide range of redistribution problems.

Benchmark Dalvik and Native Code for Android System

Googles Android Native Development Kit (NDK) is a toolset that lets you embed components to use of native code in your Android applications. It makes possible for developers to easily compile in C/C++ for the Android development platform. Generally, developer does not concern how effective between native code and Dalvik Java code that will causes poor performance of Android. There are some researches discussed about benchmark Java and C/C++. But they do not consider the issues of Dalvik and native code for Android programming or evaluate them in real Android device. In this work, we use a more complete approach to benchmark Dalvik java code and Native code on real Android device. We conducted 12 test programs to analyze the performance and found that native code faster than Dalvik Java code for about 34.2%.

A Cloud-Based Smart-Parking System Based on Internet-of-Things Technologies

This paper introduces a novel algorithm that increases the efficiency of the current cloud-based smart-parking system and develops a network architecture based on the Internet-of-Things technology. This paper proposed a system that helps users automatically find a free parking space at the least cost based on new performance metrics to calculate the user parking cost by considering the distance and the total number of free places in each car park. This cost will be used to offer a solution of finding an available parking space upon a request by the user and a solution of suggesting a new car park if the current car park is full. The simulation results show that the algorithm helps improve the probability of successful parking and minimizes the user waiting time. We also successfully implemented the proposed system in the real world.

An efficient multi-source multicast routing protocol in mobile ad hoc networks

Mobile ad hoc networks are organized by a collection of wireless devices. Any pre-established wired or wireless infrastructure or centralized administration is unnecessary. Thus, ad hoc wireless networks are particularly useful in regions such as battle-fields or disaster areas. There are numerous applications, such as video conferencing, distance learning and video on-demand relay on multicast routing. Most existing multicast routing protocols in ad hoc networks consider only one source in a multicast group, resulting in large overhead when the system is extended to multi-source multicasting. In this paper, we propose a cluster-based multi-source multicast routing protocol to provide efficient multicasting in the multi-source multicast environment. Simulation results show that the proposed protocol generates low overhead without dropping the delivery ratio in the multi-source multicast environment.

A Cluster-Based Coverage-Preserved Node Scheduling Scheme in Wireless Sensor Networks

Wireless sensor networks consist of a large number of low-power, small-scale sensors with limited processing and communication capabilities. Such networks are usually applied to gather data from interested area or specific environment and deliver to remote users for analyzing or monitoring. Because of sensing devices are usually powered by batteries, it is a great challenge to meet the performance of long system lifetime required by different applications under limited power. In the densely deployed sensor networks, the area or data sensed by neighboring sensors may overlap. In recent researches, coverage preserved node scheduling has been proposed to conserve power and provide sensing reliability. By selecting appropriate sensors into sleep state, the system lifetime can be extended without losing coverage. In this paper, we propose a duster-based coverage-preserved node scheduling scheme. We divide sensors into clusters and group cluster members into sponsor sets based on neighbor information. The proposed approach distributes the workloads among sponsor set nodes and ensures sufficient coverage as long as possible

HarpiaGrid: A Geography-Aware Grid-based Routing Protocol for Vehicular Ad Hoc Networks

Vehicular Ad Hoc Network (VANET) is a research field attracting growing attention. Current routing protocols in VANETs usually use route discovery to forward data packets to the destination. In addition, if vehicle density is low in the network, there might not be vehicles available to deliver the packet. This paper proposes HarpiaGrid, a geography-aware grid-based routing protocol for VANETs. The protocol uses map data to generate a shortest transmission grid route, effectively trades route discovery communication overhead with insignificant computation time. By restricting packets in grid sequences rather than blindly greedy search and making use of route cache approach, HarpiaGrid reduces many unnecessary transmissions, thus greatly improving routing efficiency. Moreover, in the route maintenance, this work proposes a local recovery scheme and uses backtracking techniques to generate a new grid forwarding route, providing superior fault-tolerance capability. Experiments were conducted, and the results demonstrated that the proposed scheme is indeed more efficient than other protocols.

An efficient traffic control system using dynamic thresholding techniques in wireless mesh networks

Wireless mesh networks (WMNs) depend on a resilient and high-performance infrastructure to provide users pervasive Internet access. In WMNs, all Internet traffic will be forwarded to the Internet gateways. Hence, these gateways are generally bottleneck nodes. This work proposes a traffic control technique to reduce the bottleneck problem and increase the utilization of network resources. Our approach provides a traffic control strategy that exploits dynamic techniques to adjust the threshold according to the traffic load of each gateway. The base threshold is defined in order to effectively control the traffic. When the current load exceeds the threshold of a gateway, the traffic redirection strategy is implemented by switching border nodes. The service regions can be adjusted for each gateway based on the traffic load. Furthermore, the proposed dynamic thresholding approaches can distribute the workloads of gateways and maintain the thresholds of any two gateways within a level range, making an in-band balance of load. Thus, our proposed scheme can handle the unnecessary traffic redirection and reduce the traffic control overhead for various distributions of traffic. Experimental results demonstrate that our scheme outperforms other schemes in terms of packet delivery ratio and efficiency, especially in bursty traffic environments. Copyright

A Distributed Virtual Backbone Development Scheme for Ad-Hoc Wireless Networks

The virtual backbone is an approach for solving routing problems in ad-hoc wireless networks. The virtual backbone approach features low latency, moderate routing overhead and is a hybrid scheme that uses the table-driven and on-demand routing protocols. This work presents a distributed virtual backbone development scheme for ad-hoc wireless networks. Using clustering, distributed labeling and heuristic Steiner tree techniques, our scheme outperforms other schemes in terms of the size and stability of the virtual backbone and the virtual backbone change rate. Experimental results demonstrate that our scheme has lower overhead than traditional table-driven and on-demand routing schemes.

HarpiaGrid: A Reliable Grid-based Routing Protocol for Vehicular Ad Hoc Networks

Vehicular ad hoc network (VANET) is a research field attracting growing attention. Current routing protocols in VANET usually use geographic information to forward data packets to the destination. Since geographic routing is stateless, during routing forwarding, route recovery processes would be continuously initiated if any topology hole exists, resulting in serious performance degradation. In addition, if vehicle density is low in the network, there might not be vehicles available to deliver the packet. This paper proposes HarpiaGrid, a reliable grid-based routing protocol for VANETs. The protocol utilizes in-car navigators to produce geographically logical routing paths, effectively trades route discovery network overhead with insignificant computation time. In addition, by taking advantage of the information provided by gridded geographic data, transmissions are made more efficient. Moreover, in the route maintenance, a fault-tolerance procedure is designed to avoid dead paths. Simulations were conducted, and the results demonstrated that the proposed scheme is indeed more efficient and reliable than other protocols.