Research



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  • Current Projects




    Introduction
    The following research areas will be the initial focus of the Centre:
    • Data QoS (Quality of Service) - While for voice communication, the performance indices and measurement methods are well understood, wireless data QoS is a new and much needed area of research. Methodology for characterizing the end-to-end QoS will be developed. Then measurement techniques applicable to Hong Kong will be designed and deployed for periodic reporting. Innovative methods for improving wireless data QoS will be studied.

    • Service Creation - New wireless networking technologies (2.5G, 3G and wireless LAN) will provide the mobile users with a rich selection of bandwidths and connectivity choices. The Centre will design new mobile multimedia applications, using the enabling technologies to meet the needs of both consumer and business users in Hong Kong. These new applications will provide additional revenue generating opportunities for the mobile industry.

    • Content Delivery - While 3G technologies have been standardized, few operators have experience in deploying and optimizing 3G network infrastructures yet. Innovative algorithms will be designed to maximize the network performance, especially for the applications of interest to Hong Kong operators such as media streaming. Research outputs will also be useful for contributions to future wireless standards.


    Current Projects

    Resource Control in Wireless Networks

    Resource control in wireless networks is an important issue due to the limited capacity of wireless networks. Mechanisms for resource control need to be flexible, robust and efficient in order to meet the service reliability and diverse quality-of-service (QoS) requirements of different applications in various types of wireless networks like the 3G networks, IEEE 802.11-based ad-hoc networks, sensor networks, and vehicular ad-hoc networks. Resource control mechanisms in these networks must effectively manage critical tasks like flow control, routing, scheduling, buffer management and admission control. Network resources need to be fairly and efficiently allocated, depending on actual user requirements and preferences. In addition to the network resource control mechanisms, sometimes the end-user applications may also need to adapt their behavior in response to feedback signals from the network. Ultimately, the final objective is to maximize the utilization of the network resources, while at the same time meeting the needs of the wireless network users. In our research work, we investigate issues of resource control in different types of wireless networks, identify the constraints in each network and propose simple and robust methods that efficiently utilize and manage the limited resources in the wireless networks.


    Traffic Engineering with Partial Interference  

    Previous research assumed interference in a wireless network to be binary, i.e., simultaneous transmissions are either mutually exclusive or totally independent. However, experimental studies showed this assumption is not valid. We are investigating how much can be gained in terms of capacity by considering this partial interference and designing traffic engineering or network optimization algorithms to realize the gain from partial interference.


    Related publications:
  • Characterizing and Exploiting Partial Interference in Wireless Mesh Networks


  • Delay/Disruption Tolerant Networking (DTN)  

    In the real world networking environment, some extreme or challenging situations often arose where a connected end-to-end path usually does not exist. Although such networking environment is insufficient to support any real-time synchronous applications, it still allows the operations of some asynchronous applications that can tolerate large end-to-end delay. DTN provides a message oriented store-and-forward overlay architecture over transport layer. This overlay provides in-network persistent storage facility and routing framework to support data delivery under intermittent connectivity.


    Related publications:
  • Forwarding and Replication Strategies for Delay Tolerant Networks (DTN) with Resource Constraints


  • Spectrum Sharing in Cognitive Radio Network  

    Cognitive Radio Network is an interesting topic in research. Nowadays the wireless spectrum assignment is not efficient. Therefore we are looking for using Cognitive Radio Network to improve the spectrum efficiency. We are focused on the spectrum sharing. The goal of the research is to find a practical solution to share spectrum bands efficiently, in terms of user throughput and fairness.


    Capacity Planning in Multi-Radio, Multi-Channel Wireless Mesh Network  

    In a wireless mesh network, transmissions that use the same channel may interfere with each other and suffer from capacity reduction due to the shared nature of wireless medium. As a result, mesh routers are usually equipped with multiple interfaces and assigned to multiple channels to increase the capacity of the network. However, without careful planning, it is not possible to exploit the benefits of using multi-radio. Capacity planning in a multi-radio wireless mesh network is a challenging issue.


    Opportunistic Routing in Wireless Mesh Network  

    The medium in a wireless network is shared and wireless interference often causes serious capacity reduction. Recently, researchers find that it may be possible to make use of the broadcast nature of wireless medium as an advantage. This is achieved through the use of opportunistic routing. The main difference between opportunistic routing and traditional routing is that route selection is deferred until the packet transmission.


    Counting and Data-Collection Algorithms for Real-Time, Massive RFID Applications  

    RFID tags are being used in many diverse applications in increasingly large numbers. To collect information stored in the RFID tags, most existing algorithms require the explicit identification of individual tags as the first step. For a large class of applications such as data-collection/aggregation and inventory tracking, the explicit identification requirement not only increases the probing latency unnecessarily, but also raises serious privacy concern. In this work, we propose a privacy-preserving scheme that enables anonymous estimation of the cardinality of a dynamic set of RFID tags without explicit tag identification. The scheme can be used to track the dynamics of the changes of a tag set population in both the spatial and temporal domains. It can also support rapid data collection/ aggregation from multiple spatially/temporally-diverse, large and dense fields of RFID tags. We show that the proposed scheme is highly adaptive and can accurately estimate tag populations across many orders of magnitude, ranging from a few tens to millions of tags, with only a logarithmic increase in total estimation time for each order of magnitude increase in the operating range. The associated data-collection latency is also substantially lower than that (< 10%) of the schemes which require explicit tag identification. We also demonstrate the efficacy of the proposed scheme via a spatial and temporal RFID tracking application.


    Related publications:
  • Anonymous Tracking using RFID tags





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