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Ongoing Research in Communication Technology Laboratory. Information Engineering Department The Chinese University of Hong Kong. Prof. Tak-Shing Peter Yum ( 任德盛 教授 ). Outline. Internet Congestion Control (Cun-Qing Hua) Peer-to-Peer Network (Li Zhang)

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Ongoing Research in

Communication Technology Laboratory

Information Engineering Department

The Chinese University of Hong Kong

Prof. Tak-Shing Peter Yum (任德盛 教授)

  • Internet
    • Congestion Control (Cun-Qing Hua)
    • Peer-to-Peer Network (Li Zhang)
    • Internet Content Adaptation Protocol (Wing-Lam Tam)
  • Wireless Communication
    • OVSF Code Assignment Schemes (Yang Yang)
    • Cell Sectoring for CDMA Systems (Fang-Zhong Shen)
  • Routing
    • Offline Routing for RPR (Cheng Li)
congestion control 1
Congestion Control – 1
  • Host-based Congestion Control
    • Based on packet loss detection:

e.g. TCP Tahoe, Reno and NewReno

    • Based on end-to-end delay variance:

e.g. TCP Vegas and Tri-S

    • Advantages
      • Easy to implement
      • Easy for decentralized resource allocation
    • Weakness
      • long response delay (at least one round trip time)
      • Limited information collected solely from end hosts may lead to improper response to congestion
congestion control 2
Congestion Control – 2
    • Case study: TCP Vegas

The TCP Vegas flows passing through multiple congested links tend to be unfairly treated due to the cumulative nature of round trip time

  • Router-based Congestion Control
    • Routers monitor the network state and notify the end hosts in case of congestion by dropping or marking packets: e.g. RED, BLUE, ECN
congestion control 3
Congestion Control – 3
  • Our solution:The Joint Congestion Control (JCC)
    • It unifies the efforts of end hosts and routers to provide proactive and accurate congestion control
  • Basic Idea

The source sends probing packets to collect the state of the most congested link along the path, and with which to adjust the congestion window

  • Properties
    • Lower variance of throughput
    • Lower packet loss rate
    • Fairer resource allocation
peer to peer network 1
Peer-to-Peer Network – 1
  • Traditional C/S Model
  • P2P network:
    • every node can take the roles of both server and client
    • intermittently connected edge devices (PC, PDA, WAP Phones) can receive information from and provide information to the Internet
    • Takes advantage of edge device resources
      • Storage and processing capability of edge devices
      • Content of edge devices
      • Human presence at edge devices
peer to peer network 2
Peer-to-Peer Network – 2
  • Typical Problems
    • A distributed naming scheme for nodes and files
    • A distributed file indexing scheme
    • Server selection
    • A distributed routing protocol (reverse anycast)
    • Security and authentication
peer to peer network 3
Peer-to-Peer Network – 3
  • Our work
    • Architecture and topology
      • Architecture design: Distributed, Centralized and Augmented
      • Network partitioning
    • Server selection
      • Network distance Measures
      • Routing rules
      • Delay and throughput Analysis
ovsf code assignment schemes 1
OVSF Code Assignment Schemes– 1
  • Orthogonal variable-spreading-factor(OVSF) codes are the basic resource units for assignment in UTRA-TDD and FDD systems
ovsf code assignment schemes 2
OVSF Code Assignment Schemes– 2
  • Nonrearrangeable and rearrangeable code assignment schemes
  • Our solution:Compact Assignment (CA) and Rearrangeable Compact Assignment (RCA)
    • Both schemes can leave the resulting code tree as flexible as possible (in supporting multi-rate traffic classes) after each code assignment
    • Analytical and simulation results show both schemes can offer the blocking, throughput and fairness performance very close to the theoretical bounds
    • Compared with other schemes, CA and RCA have the combined advantage of simple, efficient, stable and fair
    • Generalization: optimize the assignment to match the traffic rate distribution
cell sectoring for cdma systems 1
Cell Sectoring for CDMA Systems– 1
  • Problem
    • Cell sectoring is used to reduce the co-channel interference
    • However, it works inefficiently when addressing hot-spot scenarios. Some congested sectors may have outages, while the lightly loaded sectors may have spare capacity
  • Solution
    • Dynamic cell sectoring, i.e., adaptively changing the sector pattern according to the traffic can solve the problem
cell sectoring for cdma systems 2
Cell Sectoring for CDMA Systems– 2
  • Three Aspects
    • How to produce dynamic sector patterns?
      • Circular Array Beamforming networks with Butler Matrix
    • Dynamic Cell Sectoring Algorithms
      • MinTTP Sectoring based on Shortest Path Algorithm
      • PE Sectoring based on Greedy Algorithm
    • How to keep the optimality of the sectoring at all times
      • Resectoring: Detect the traffic and readjust the sector boundaries when necessary.
internet content adaptation protocol 1
Internet Content Adaptation Protocol– 1
  • Objective
    • Develop Web services for customizing content
      • Language Translation
      • Advertisement Insertion
  • Conventional Approach
    • Proprietary API
      • Single-source solution, creating programming and testing complexities
      • Problems of scalability, flexibility, reusability
internet content adaptation protocol 2
Internet Content Adaptation Protocol– 2
  • Our Approach
    • Attach application servers to proxies through ICAP
internet content adaptation protocol 3
Internet Content Adaptation Protocol– 3
  • Internet Content Adaptation Protocol
    • Open protocol
    • Enables communication between edge content devices (web caches and Internet content origin servers) and application servers for content adaptation
    • Part of an evolving architecture that promotes Web scalability by better facilitating distribution and caching
internet content adaptation protocol 4
Internet Content Adaptation Protocol– 4
  • Work Involved:
    • Development of the ICAP protocol core
      • Architecture design
      • Software implementation
    • Development of the ICAP-enabled e-services
      • Content filter and transcoder for WAP phones
      • Advertisement insertion server
    • Performance analysis of ICAP-enabled proxy
      • ICAP overhead
      • System scalability, efficiency
      • Caching performance
offline routing for rpr 1
Offline Routing for RPR – 1
  • The topology of IEEE 802.17 Resilient Packet Ring (RPR) is as follows
offline routing for rpr 2
Offline Routing for RPR – 2
  • Objective
    • Design the link capacity dimensioning for this system
  • Problems
      • Given: Traffic matrix, Ring topology, utility function
        • Maximize the system revenue or throughput while maintain fairness among the competing flows
      • Given: Traffic matrix, utility function
        • Link capacity dimensioning
  • Solutions:
      • Linear programming
      • Non-linear programming with convex objective function and linear constraints