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University: City University of Hong Kong
Sponsoring Professor: Dr. Sammy CHAN
Department: Department of Electronic Engineering

1.  Project: Performance Modeling for Hierarchical Overlay Networks

Future broadband wireless networks aim to provide all-IP based access through integrating various existing wireless access technologies, e.g.WiFi,WiMAX, 3G and LTE. To facilitate internetworking between these heterogeneous networks, hierarchical overlay infrastructure has been considered as a possible solution, e.g. overlaying GPRS/WiMAX on top of WiFi access points, or cellular systems over femtocells. When mobile users enter the uncovered areas of cellular base stations, on-going traffic can overflow to neighboring open-access femtocell networks for continuous connection; or when call requests are rejected by femtocells due to capacity limit, the blocked calls can overflow to the covering GPRS/WiMAX. Efficient and accurate modeling is crucial for performance evaluation and network dimensioning. However, it is a difficult issue in hierarchical overlay wireless networks since the arrivals of inter-network overflow traffic can be bursty in nature with large variance. The loss analysis methods for Poisson traffic are not available for non-Poisson overflow traffic. This project aims to propose a computationally efficient performance modeling for overflow traffic to achieve approximate performance evaluation for hierarchical overlay networks. We use OPNET to obtain the simulation results of the performance in multi-tier hierarchical overlay networks in order to verify the accuracy of the analytical results obtained by our proposed approximate performance modeling.

PUBLICATIONS

• Qian Huang, King-Tim Ko, and Villy B. Iversen, "Approximation of loss calculation for hierarchical networks with multiservice overflows", IEEE Transactions on Communications, vol. 56, no. 3, pp. 466473, Mar. 2008.

• Qian Huang, King-Tim Ko, and Villy B. Iversen, "Performance Modeling for Heterogeneous Wireless Networks with Multiservice Overflow Traffic", Proceedings, IEEE Globecom 2009.
   

2. Performance Evaluation of a TCM-based Hybrid ARQ Scheme over Wireless Links

Mechanisms providing efficient and reliable transmission in wireless radio channels is very important because they are noisy and bandwidth-limited compared with wired transmission medium. With the proliferation of running TCP/IP-based applications in heterogeneous networks comprising both wired and wireless systems, such mechanisms are even more important, as directly deploying current TCP congestion control schemes over radio links would lead to serious end-to-end throughput degradations. To alleviate the adverse impacts from wireless links on TCP performance, one possible solution is to improve the link quality by using efficient local error recovery mechanisms in the link layer. In this project, an efficient TCM-based hybrid ARQ is proposed. The throughput performance of this novel ARQ scheme is evaluated based on a link layer simulation model developed in OPNET.
 

PUBLICATIONS

4. Performance Model of Video-on-Demand Systems in Broadband Networks

A video-on-demand (VoD) system allows a viewer to choose a video of his choice such as movies, electronic encyclopedia, and educational videos and be delivered to him real time via a network. This project is a performance study of a distributed video server system in a fully connected backbone network. The nature of the VoD service requires massive storage from the video server and massive bandwidth from the network. Our analytical model can be used to determine the storage and bandwidth requirements for different system configurations. Analytical results will be compared with simulation results obtained using OPNET.

• E.W.M. Wong and S. Chan, "Performance Modelling of Video-on-Demand Systems in Broadband Networks", IEEE Circuits and Systems in Video Technology, vol. 11, no. 7, pp. 848 -859, July 2001.
  

 

5. Server Allocation Stragtegy in VoD Service

When a subscriber's request arrives at the VoD system, it is directed to one of the available servers. The role of allocation strategy is to spread out the loading among the servers, hence reducing the blocking probability and increasing the utilization. We will study the performance of different strategies by simulation using OPNET.

PUBLICATION

• S. Chan, K.S Tang, K.T. Ko and E. Wong, "Minimum Blocking Probability in a Multimedia-on-Demand System", Proceedings, ISTN' 2000, Hangzhou, November 2000.
  

6. Efficient Handoff Management Scheme for Mobile Wireless ATM Networks

In this project, a new handoff management scheme for wireless ATM networks is studied. In this scheme, all cells are connected to its neighboring cells by permanent virtual circuits (PVCs), and to the Access Switch (AS) by switched virtual circuits (SVCs) which are only for new calls. Some carefully chosen cells, called rerouting cells, are also connected to the AS by PVCs. In summary, if a mobile roams to an ordinary neighboring cell, its traffic path is simply elongated by a PVC connecting the old and new cells. If a mobile roams to a rerouting cell, its traffic path is rerouted to a PVC between the AS and rerouting cell. By using PVCs for handoff calls, we can guarantee fast and seamless handoff. At the same time, our scheme improves the path efficiency by limiting the maximum number of hops that a path can be extended. OPNET is the simulation tool used to study the performance of this scheme.

• K.S. Chan, S. Chan, K.T. Ko, K. Yeung and E. Wong, "An Efficient Handoff Management Scheme for Mobile Wireless ATM Networks", IEEE Trans. on Vehicular Technology, vol. 49, no. 3, pp. 799-816, May 2000.
  

7. Course/Lab Using OPNET

• EE6412 - Switching and Routing in Telecommunication Networks
  
  • Lab Manual
     
• EE3313 - Queueing System & Teletraffic Engineering
   
  • Lab Manual