I-Hsuan Peng

Energy consumption bounds analysis and its applications for grid based wireless sensor networks

Grid based wireless sensor networks have the advantages of dynamic topology configuration and flexible selection of forwarding paths. However, like other schemes, the energy management of electronic device is a very important issue when the lifespan of the network is critical. The energy consumption of a grid based network depends on the topology of the grid as well as the actual forwarding path. In this paper, we analyze the upper and lower bounds of the transmission energy costs for grid based wireless sensor networks. The results are applicable for evaluation of the effectiveness of grid construction scheme and the routing efficiency of grid based networks. In order to illustrate the applications of the derived results, we proposed an example of topology combination approach to evaluate efficiency with respect to the derived lower bound. Experiments were conducted to verify the validity of the derived bounds and evaluate the energy consumption of the multiple sources forwarding through topology combination.

Implementation of a PDA/GPS based development platform and its applications in native education

In order to apply the mobile technology and the information technology for the applications in the learning environment, the PDA, wireless, and the location identification feature provided by GPS are integrated for the development of the GPS/PDA Guide system. By using this system, the guided information can bind with its location automatically. The most important concept of the proposed system is that the guiding information can be constructed by users during the tour guide, which is different from the traditional guiding experience. In this paper, we propose a platform for the development of the GPS/PDA guide system. This platform includes the software resided at PC side and PDA side. In the PC side, a target based digital map generation tool is also designed. Currently, this platform is applied for the native education of Hwa-lien city in Taiwan and we will plan to promote the proposed platform and the application style to other guided based environments.

Study of multicast wavelength arrangement for maximizing network capacity in WDM networks with sparse wavelength converters

The issue of wavelength assignment is one of the most important factors that affect the capacity for the deployment of optical networks. This issue becomes more critical for multicast connections, especially when the network nodes have no wavelength conversion capability. Although the wavelength assignment can be more flexible if each node can perform wavelength conversion, the deployment cost increases accordingly. A compromise is to support a limited portion of conversion nodes in the WDM network. We propose a systematic approach for the wavelength assignment of multicast connections in WDM networks with sparse wavelength conversion nodes. The efficiency of the arrangement of wavelength is measured by its influences on the available capacity of the network and the consumption of wavelengths. By using the proposed approach, the Static Cost Greedy (SCG) algorithm [8] can be easily extended to be applicable in a Sparse Wavelength Conversion Network (SWCN). In addition, instead of SCG, the Minimum-Effect-First (MEF) algorithm is proposed to maximize the network capacity during wavelength assignment. We compare the performance of the proposed MEF methods with the extended SCG scheme through exhaustive simulations. The experimental results indicate that the proposed MEF schemes demonstrate much better performance than the SCG scheme. We also found that the performance is not always improved proportionally to the increment of the wavelength conversion nodes. The improvement reaches saturation when the number of conversion nodes is above 35% of the total number of nodes.

Dynamic Bandwidth Management for Handoffs with RSVP in 802.16/WLAN Environment

In order to provide seamless handoff for QoS connections in 802.16-2004/WLAN environment, a cross layer design approach is proposed to manage the bandwidth requirement of mobile node during movement. The main concept of the dynamic bandwidth management proposed in this paper is to treat the layer 2 connection of 802.16 as a pipe that aggregates multiple layer 3 RSVP connections with the same class of service. As the layer 3 connections are integrated into a pipe, bandwidth can be managed in a more statistical way. The control procedure of RSVP connection is designed in accordance with the signaling procedure of 802.16. In order to manage the bandwidth effectively, the admitted bandwidth utilization portion (ABUP) is defined as a threshold of the layer 2 pipe to determine whether the reserved bandwidth is enough or not. This threshold also plays an important role for the acceptance of handoff connection and new connection. The performance of the proposed scheme is examined through exhaustive simulations. Our results show that our scheme demonstrates a quite good performance in managing resources for RSVP connections in 802.16/WLAN environment.

Study of Radio Resource Allocation Scheme for Single Carrier FDMA in LTE Network

Single carrier frequency division multiple access (SC-FDMA) is applied as the transmission technology for the uplink traffic in LTE networks. The radio resource allocation is one of the most important issues to achieve effective wireless communication. Most researches focus on maximizing the system throughput of SC-FDMA under changing channel condition. However, users may require different quality of services (QoS) for different applications. This paper studies the radio resource allocation for QoS users in using localized SC-FDMA transmission. The proposed scheme is divided into the matching algorithm and the radio resource assignment algorithm. The Gale-Shapley algorithm is applied to find the optimal matching of resource block (RB) by considering the channel condition and the desired QoS of UE. The Recursive Maximum Expansion (RME) algorithm is modified in this paper to effectively assign radio resource for UEs with different bandwidth demands. The video streaming, VoIP, and FTP traffic types were adopted for simulations. Our results show that the proposed scheme achieves better QoS satisfaction than that without matching mechanism.

Implementation of Indoor VOC Air Pollution Monitoring System with Sensor Network

The air quality monitoring has become one of the most important and critical issues as human beings are paying more and more attention to the living quality. Various countries legislate on air quality norm related to the monitoring and measurement standards of air condition. However, most of monitoring stations for air pollution are set up in outdoor and monitor sources of air pollution and global warming gases in big region, neglecting the importance of Indoor Air Quality (IAQ). In this paper, we implement a Total Volatile Organic Compounds (VOCs) air pollution monitoring system to report value of VOCs concentration in indoor environment. The air pollution monitoring system is with long term monitor and sets up indoor gases Wireless Sensor network (WSN) with the consideration of the cost, development complexity, and the operation convenience. Through experiments and evaluation in the indoor painting environment, we have verified the feasibility of the system and shown the variation of indoor air quality.

Improvement of Streaming Video in Differential Service Networks by Using Opportunity RED Mechanism

The video streaming service is one of the emerging services for network users. The network conveys various kinds of traffic to the users and different traffic classes always have different quality requirements. Therefore, it is a critical issue to allocate suitable network resource to suitable traffic class for better service quality provisioning and resource utilization. This paper considers the characteristics of video frames to forward the video packet in an efficient way. The proposed scheme properly utilizes the unused bits of the differential service (DS) field of the IP header to provide some heuristic information for packet early discarding. Thus, by using the opportunity random early dropping (RED) concept, the proposed packet correlated RED (PCRED) scheme refers the heuristic information to selectively drop useless packet that is not helpful for the improvement of receiving quality for better buffer and bandwidth utilization. Exhaustive simulations were conducted to compare the performance of the proposed scheme with the RED with in/out (RIO) and weighted RED (WRED) schemes. The simulation results show that the proposed scheme is superior to the other schemes for video streaming services.

Study of safety and efficient routing for intelligent transportation system

In this paper, a novel dispatching and routing scheme of Vehicle Route Guidance Systems (VRGS) is proposed for safe and efficient transportation. The application scenario focuses on the cooperative dispatching and route decision of vehicles within a specific area consisting of streets and several intersections. In addition to computing a specific routing path for the arrival vehicle according to its destination and safety considerations at intersections, the proposed scheme provides a detour mechanism triggered by traffic jam. The performance is analyzed by measuring the time required for vehicles to travel in this area, the average moving speed of the vehicles, the frequency of the detour routes, etc. The experimental results show that the proposed scheme can effectively route the vehicles without any collision and it also demonstrates a quite good performance in above measurement criteria.

Connection control by virtual admission in wireless LAN environment

The traditional wireless technology confronted with some short-comings in practical use, such as insufficiency for bandwidth, and lack of guaranteed on Quality of Services (QoS). Both of the packet scheduling and connection admission control are the main consideration issues toward QoS networks. These two issues are mutually correlated. In this paper, we propose a measurement based with fake priority scheme for the control of connection admission in WLAN. As the concept of the virtual source and virtual MAC (VS/VMAC) is applied, the proposed scheme will not affect the transmission of existing traffic during traffic probing. The proposed scheme also provides a difference factor (D factor) for the compensation of the performance measured by VMAC. This factor is also applied to control the tightness of the policy of connection acceptance. The simulations results show that the proposed scheme can effectively manage the connection requests while maintaining QoS in WLAN.

Energy-saving centric uplink scheduling scheme for broadband wireless access networks

This study proposes an energy-saving centric uplink scheduling (ESC-US) scheme to support efficient energy usage and satisfy the quality of service (QoS) requirements of Worldwide Interoperability for Microwave Access (WiMax) networks. The uplink resource allocation is different from that of the downlink resource allocation scheme because the uplink traffic is queued at the mobile station (MS) and the base station (BS) has no information regarding it without using a polling procedure. The considered resource scheduling schemes maximize the sleep efficiency and consider the QoS requirements of individual MSs. The proposed scheduling scheme in this study considers the delay budget of MSs with real-time connections and the required minimum reserved traffic rate (MRTR) of MSs with non-real time connections when maximizing sleep efficiency. Both scheduling schemes for the traffic of real-time polling services (rtPS) and non-real-time polling services (nrtPS) apply the ‘just enough QoS’ and ‘sleep before transmission’ (SbT) concepts to achieve this energy-saving centric objective. Exhaustive simulations were conducted to examine the performance of the proposed schemes. The simulation results show that both schemes guarantee the desired QoS and achieve superior energy-savings efficiencies compared to the conventional scheme.