Wei-Tsong Lee

An adaptive approach to weighted fair queue with QoS enhanced on IP network

We propose an adaptive bandwidth allocation algorithm for reservation protocols to support quality-of-service networking on the future multimedia Internet. QoS design is the fundamental functionality of the next generation IP router to enable differentiated delivery and to guarantee the delivery quality for diverse service traffic. The proposed algorithm called adaptive weighted fair queue (AWFQ) scheduling employs the queue status and priority assignment to determine the bandwidth sharing of various Internet services and to ensure the defined QoS policy is obtained. We propose a smart methodology of distributing the outlink bandwidth in a flexible, fair and prioritized manner to utilize network bandwidth more effectively and efficiently. In simulation, we compare the proposed AWFQ algorithm with priority queue (PQ) and weighted fair queue (WFQ) that are two famous scheduling algorithms in practice. In comparison, we examine their performances in terms of packet loss, bandwidth utilization and queue dynamics to verify our algorithm. We find that the proposed algorithm has the following advantages: 1) improves the bandwidth starvation of low-priority traffic occurring in PQ, 2) has a high bandwidth utilization close to PQ, 3) has a low queue congestion and 4) maintains the fairness of WFQ. Overall, the proposed algorithm not only has an excellent performance close to PQ but also improve the disadvantage of PQ.

A Novel Geographic Routing Strategy over VANET

In recent years, the issue of Vehicular Ad-Hoc Network (VANET) has received great attention, and more and more VANET-related researches have been brought up. Generally speaking, the biggest difference between VANET and traditional Ad-Hoc is the velocity of carriers because in VANET, the velocity of vehicles the carriers is much higher than that of the carriers in traditional Ad-Hoc. Furthermore, it would be a great challenge to forward data efficiently in VANETs. Thus, many researches proposed have focused on the development of Routing Protocols. The main purpose of this paper is to investigate Geographic Position-Based Routing Protocol, which needs Global Position System (GPS) to obtain the positions of vehicles and to enhance the decision-making of data delivery. Therefore, only partial topology information is needed during the decision-making of data delivery for the routing protocol to have better adaptability in high-speed network topology. This paper aims to improve Greedy Perimeter Stateless Routing (GPSR) Protocol and implement our proposed scheme into a complex scenario like urban area. For this reason, with the concept of vector, greedy forwarding mode of GPSR not only concerns the distance to enhance the accuracy of routing data while choosing the next hop, but also, in terms of the intersections in urban area, adds a predictive mode to predict the motions of vehicles at the intersections to improve the efficiency of routing protocol.

CSMA/CF Protocol for IEEE 802.15.4 WPANs

Different emerging IEEE 802.15.4 wireless personal area networks (WPANs) are one solution for wireless sensor networks (WSNs), where applications are restricted by low data rate, short transmission distance, and low power consumption. The frame transmission mechanism of the IEEE 802.15.4 standard, which adopts the blind random backoff mechanism, was designed to minimize power consumption. However, it cannot provide satisfactory performance in a realistic hidden-node environment, because it may incur a hidden-node collision chain situation and unexpectedly limit the overall network capacity. For each successful data transmission, any inefficient transmission mechanism will incur prolonged access delay and will consume too much power. Moreover, the current design becomes inefficient as the number of devices significantly increases. As a solution, we propose a new multiple access protocol with improved efficiency at the sublayer between the media access control layer and the physical layer, i.e., a carrier sense multiple access with collision freeze (CSMA/CF) protocol, which comprises a collision resolving scheme and a P-frozen contention strategy. The CSMA/CF protocol can quickly alleviate aggravated collision situations in a hidden-node environment. Such a particular collision phenomenon is denoted as a collision chain problem (CCP). The impact from CCP is thoroughly discussed and analyzed. As confirmed by the results of analysis and performance evaluations, the proposed CSMA/CF protocol can achieve significant performance improvement in energy conservation, access delay reduction, and transmission reliability enhancement.

Cloud-based image processing system with priority-based data distribution mechanism

Most users process short tasks using MapReduce. In other words, most tasks handled by the Map and Reduce functions require low response time. Currently, quite few users use MapReduce for 2D to 3D image processing, which is highly complicated and requires long execution time. However, in our opinion, MapReduce is exactly suitable for processing applications of high complexity and high computation. This paper implements MapReduce on an integrated 2D to 3D multi-user system, in which Map is responsible for image processing procedures of high complexity and high computation, and Reduce is responsible for integrating the intermediate data processed by Map for the final output. Different from short tasks, when several users compete simultaneously to acquire data from MapReduce for 2D to 3D applications, data that waits to be processed by Map will be delayed by the current user and Reduce has to wait until the completion of all Map tasks to generate the final result. Therefore, a novel scheduling scheme, Dynamic Switch of Reduce Function (DSRF) Algorithm, is proposed in this paper for MapReduce to switch dynamically to the next task according to the achieved percentage of tasks and reduce the idle time of Reduce. By using Hadoop to implement our MapReduce platform, we compare the performance of traditional Hadoop with our proposed scheme. The experimental results reveal that our proposed scheduling scheme efficiently enhances MapReduce performance in running 2D to 3D applications.

A GA-based mobile RFID localization scheme for internet of things

In the current (Internet of Things) trend, the identification capability of RFID is integrated for the identification and applications of all objects, and this trend reveals the future demand for RFID wireless communication and localization. Therefore, this paper investigates the influences of RSSI and the distance to RFID and analyzes the common indoor localization algorithms, including range-based algorithms and range-free algorithms. However, there are too many interference factors in the indoor environment that easily lead to localization inaccuracy. To improve the RF-mapping technique in RFID that requires much time for initiation and lots of calculations, this paper proposes a GA-based (Genetic Algorithms, GA) localization algorithm to estimate the locations of unknown nodes and avoid the influence of environmental factors by pre-establishing the pattern. The designed scenarios and reference nodes in this paper are used to train our proposed algorithm and obtain the patents of the scenarios, which are adopted for RFID nodes to further compare and decrease errors. Therefore, as long as the algorithm is trained in advance with the scenarios and then include the patents in the new environment, the errors and the training time can be greatly reduced. Moreover, our proposed algorithm needs only little information about reference nodes to pre-establish the pattern.

Scalable Video Coding of H.264/AVC Video Streaming with QoS-Based Active Dropping in 802.16e Networks

Multimedia applications over mobile wireless network are becoming popular in recent years. High video quality depends on the wide bandwidth but the wide bandwidth restricts the number of users in the network system. Effective bandwidth utilization is the major problem in wireless network because the bandwidth resource in wireless environment is limited and precious. For this reason, we propose an active dropping mechanism to deal with the effective bandwidth utilization problem. In the proposed mechanism, if the network loading exceeds the threshold, the dropping mechanism starts to drop the enhancement layer data for low level user and the dropping probability is varying with the different network loading. For the multimedia application, we use the characteristic of the scalable video coding (SVC) extension of H.264/AVC standard to provide different video quality for different level user. By the dropping mechanism, base station increases the system capability and users can obtain better quality of service when the system is under heavy loading. In this paper, we study the network platform of the 802.16e standard and add the QoS-based active dropping mechanism to the MAC layer. In the simulation results, the system capability that releases bandwidth by dropping mechanism and service quality of users are observed.

New P2P Sharing Incentive Mechanism Based on Social Network and Game Theory

P2P technology has been used widely in file and live media streaming sharing fields. But the architecture of P2P technology which we used is imperfect. In P2P system, most users are free-rider. They were not sharing their own resource because the architecture has no perfect incentive mechanism. Therefore, in this research, we propose a novel incentive mechanism (NIM) that considers useful information in social network and various important factors of the peers in P2P architecture to affect the system performance. In addition, we analyze the effectiveness of NIM by game theory. The simulation results show that deploying NIM to P2P system not only promotes the peers to spontaneous sharing their own resource but also decrease amount of free-rider.

DOCSIS performance analysis under high traffic conditions in the HFC networks

Hybrid Fiber Coaxial (HFC) networks provide a wide bandwidth and represent the solution of choice for many residential networks nowadays. The Data Over Cable Service Interface Specification (DOCSIS) protocol is an important standard for HFC networks and is supported by the majority of current vendors. This protocol uses the Truncated Binary Exponential Back-off (TBEB) algorithm to resolve collisions within the network by means of a back-off window. However, the performance of this algorithm tends to deteriorate when the network load is high. Consequently, the present study develops a novel mathematical model for the TBEB algorithm and then uses this model to identify the window size which yields the optimal system throughput and minimum delay time under high traffic conditions. The present numerical results confirm that the performance is improved when the window settings identified from the developed model are applied.

Mixing greedy and predictive approaches to improve geographic routing for VANET

In recent years, thanks to the development and popularization of wireless network technologies, the issue of vehicular ad hoc network (VANET) has received great attention, and more and more VANET-related researches have been brought up. Generally speaking, the biggest difference between VANET and traditional ad hoc network is the velocity of carriers because in VANET, the velocity of vehicles, the carriers, is much higher than those in traditional ad hoc. Therefore, it would be a great challenge to forward data efficiently in VANETs and many researches proposed have focused on the development of routing protocols. The current proposed routing protocols are all assumed to simulate in a distributed and ideal environment. As for the complex geographic environments, such as urban scenarios, extra amendments must be needed to improve the efficiency of the routing protocols. Thus, the main purpose of this paper is to design a suitable routing protocol for urban scenarios with better performance and adaptability. For this reason, greedy on straight roads and predictive at the intersections (GSPI) routing protocol is proposed to use greedy mode on straight roads and to use predictive mode at the intersections. In greedy mode, we choose the next hop according to the weight value that combines the distances and multi-rate. In predictive mode, we predict the directions of the vehicles to determine the next hop. The simulation results reveal that our proposed algorithm indeed proves its feasibility. Copyright

A Novel Adaptive FEC and Interleaving Architecture for H.264/SVC Wireless Video Transmission

The error-prone nature of wireless communication makes it hard for the traditional error recovery techniques to promptly recover different priority lost video packets. In this paper, we extend an intelligent Forward Error Correction (FEC) mechanism, Enhanced Adaptive FEC (EAFEC), to further propose and analyze the efficiency of using different FEC strength depending on H.264/SVC video stream priorities for wireless video transmission. The simulation results show that, compared with the EAFEC, our novel adaptive FEC and interleaving architecture offers better wireless bandwidth utilization through video data interleaving and less packet loss rate.