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University: Imperial College, London
Professor: Kin K. Leung
Department: Department of Electrical and Electronic Engineering
Post-Docs : Miss Yun Hou, Dr. Erwu Liu
PhD Students: Mr. Chi (Harold) Liu, Mr. Georgios Tychogiorgos


Presently, we are using OPNET to carry on a PhD research on the simulation of a new transport protocol (TCP) for wireless ad-hoc networks.

Previously, we are using OPNET to carry on an undergraduate final year research project on real-time services on wireless ad-hoc networks.

Previously, we built a three-layer (Transport + Network + MAC layer) simulation platform for Wireless Mesh Backhaul networks to verify the TCP/Routing/Scheduling algorithms proposed in our research project MEMBRANE, funded by the European Community's 6th Framework Programme. Meanwhile, we are planning to simulate routing protocols in real ad hoc wireless network environment as in MESSAGE project , funded by the Department for Transport in UK and EPSRC in UK.

Title: TCP over Wireless Ad-Hoc Networks (ongoing project) :

The aim of using OPNET is the simulation of a new transport protocol (TCP) for wireless ad-hoc networks. The protocol will be independent of the channel which means that the network can be wireless, wired or even a combination of both. The aim is to overcome some of the limitations that TCP imposes and therefore the proposed protocol will be compared to various versions of the TCP protocols. “

Title: Real-Time Services on Wireless Ad-Hoc Networks (past project) :

Wireless ad-hoc networks enable data to be transported from a source node through multiple intermediate nodes to a destination node without a fixed communication infrastructure. It is difficult to control and maintain the quality of service (QoS) in terms of delay and available bandwidth for a given node pair. Therefore, it is challenging to support real-time applications such as streaming music and voice-over-IP (VoIP), which have stringent delay requirements, in the ad-hoc networks.

The goal of this project is three-folded. First, it surveys and criticizes existing algorithms and techniques for maintaining QoS in wireless ad-hoc networks. Second, study how packet delay and available bandwidth fluctuate in ad-hoc networks as a way to determine if the networks are suitable for music streaming or VoIP applications. Third, if time permits, we shall build a small prototype based on simulation models and encoded packets to demonstrate music or VoIP quality in the ad-hoc network environments. Simulation, analysis and programming skills will be helpful on this project.

List of Publications:

[1] Shihao He, "Real-Time Services on Wireless Ad-Hoc Networks, " M.Eng. thesis, Imperial College, July, 2009. (pdf)

Title: MESSAGE Project Description (past project):
The impact of road traffic on local air quality and individuals exposure to air pollution are major public policy concerns and have stimulated a substantial body of research aimed at improving underlying vehicle technologies and traffic management schemes to minimise the impact of air pollution.

This research however requires increasingly detailed knowledge of how traffic-generated pollution behaves in the urban environment (with factors such as street and building design, vehicle braking and accelerating patterns, individual traveller decisions and local weather conditions all potentially affecting the concentration of pollutants) and can therefore only be undertaken based on the availability of high quality, high-granularity spatial-temporal environmental sensor data.

A particularly exciting direction for future development of such environmental sensor data sources is the use of vehicles and people themselves as platforms for outward facing environmental sensor systems, enabling them to operate as mobile environmental probes, providing radically improved capability for the detection and monitoring of environmental pollutants and hazardous materials.

However, these developments present new and formidable research challenges arising from the need to transmit, integrate, model and interpret vast quantities of highly diverse spatially and temporally varying sensor data.

This project aims to address these challenges by novel combination and extension of state-of-the-art e-Science, sensor and positioning technologies, data fusion, traveller behaviour, traffic modelling and emissions dispersion modelling techniques, based on combinations of pervasive roadside and vehicle/person-mounted sensors.

This work will be at the leading edge of e-Science, stretching the capabilities of the grid in a number of important respects and also facilitating a step change in the capability of underlying measurement and modelling capabilities in transport and environmental science.

Work Plan on Using OPNET for simulating VANET protocols:
High node mobility and transient connectivity in Vehicular Ad Hoc NETworks have introduced numerous challenges in the design of efficient communication protocols for these networks. Toward the goal of efficient design of such networks, the focus of our work has been to develop methods that will allow the estimation of a wireless link’s future quality and the remaining (residual) time for which this will remain efficiently active and useful for data transmission [1,2]. Our ongoing work includes utilizing such information as key input to the routing algorithms and data dissemination for VANETs. We are planning to modify the PHY layer of OPNET in order to realistically depict the challenging channel conditions in VANETs (Doppler effect, shadowing etc) and then implement novel cross layer routing protocols utilizing the already developed estimation methods.

[1] N. Sofra and K.K. Leung, "Estimation of Link Quality and Residual Time in Vehicular Ad Hoc Networks," Wireless Communications and Networking Conference, 2008. WCNC 2008. IEEE, pp.2444-2449.
[2] N. Sofra and K.K. Leung, " Link Classification and Residual Time Estimation Through Adaptive Modeling for VANETs", submitted to VTC Barcelona 2009.

 

Title: MEMBRANE Project Description(past project):
This project aims to bring an efficient wireless backhaul design as an alternative technology to serve wireless broadband networks in cases where a wired backhaul would be more costly to access and/or would take longer to deploy. We propose the design of efficient wireless backhaul networks that meet the Quality of Service (QoS) demands of high speed access wireless networks, thus providing a technology shortcut that will help satisfy the social need for broadband data anytime anywhere in a much more expeditious way.

Given the need for an efficient wireless backhaul network, its successful deployment necessitates careful design and this is likely to require nothing short of a number of technological breakthroughs.
To satisfy the above requirements, a number of enabling technologies will be exploited that have the potential, when combined, to deliver the expected performance:

Multi-hopping, i.e. the use of relays between the end user and the end node, is primarily motivated by the low power and the low heights of the access (AN) and relay nodes. Clearly, in low power transmissions, multi-hopping helps increase the range. Moreover, since low height ANs are likely to be surrounded by several obstacles, multi-hopping helps avoid the problem via multiple links that are more likely to have LOS between them.

Intelligent Antennas (IA) such as beamforming (BF) and MIMO transmission can offer improved throughput and range. Moreover, through their added "spatial" degrees of freedom, they can also reduce interference from adjacent links. Reconfigurable IA algorithms can be designed that match in the best possible way a given propagation environment, boost throughput and reduce interference thus improving overall end-to-end performance. The combination of multihop with multiple antennas is a field that is virtually unexplored and it will constitute a major innovation in MEMBRANE.

Opportunistic routing & scheduling targets primarily the satisfaction of the network's delay requirements; when combined with IA it can also increase the end-to-end throughput. By opportunistic routing and scheduling we refer to routing and scheduling policies that take into account the network context. By this we mean the quality of different links, the data traffic needs on different ANs, the capacity of different relays, the packet activity of different links, etc. Another potential gain of multi-antenna multihop mesh networks is their potential for significantly improved QoS via combined opportunistic routing and spatial data multiplexing.

Title: Research Ouput for MEMBRANE Simulation Platform by OPNET supports:
MEMBRANE OPNET simulator is a powerful and efficient cross-layer simulation platform developed by Prof. Kin Leung’s research group at Imperial College for wireless backhaul mesh networks. In this simulator, we develop, test and compare a set of existing and novel cross-layer protocols from physical layer all the way up to application layer. 

Here is a list of models developed by OPNET: 

  1. Support of various traffic demands with different QoS requirements
    • Interactive video
    • VoIP calls
    • FTP
    • HTTP
    • Email
  2. Several transport layer TCP protocols
    • Reno
    • NewReno
    • Jersey
    • Explicit rate/error/congestion notifications
  3. IP layer M
    • Multi-constrained QoS routing algorithm
  4. MAC layer
    • A distributed opportunistic proportional fair scheduling algorithm
  5. Enhanced physical layer functionalities
    • adaptive modulation and coding schemes
    • steering beam directional antennas
    • different fading channel representations.

The developed simulator is ideal for protocol verifications and performance analysis on all packet, connection, and network levels.  Compared with existing simulation platform like OPNET WiMax, we believe our simulator is one of the few that considers five protocol layer developments in an integrated simulation environment.

Here is a list of publications using OPNET:

1. C. H. Liu, A. Gkelias, and K. K. Leung. "Cross-Layer Design for QoS in Wireless Mesh Networks," to appear in Springer Wireless Personal Communications, Special Issue on “Cross-Layer Design for Future Generation Wireless Networks” (pdf)

2. C. H. Liu, S. G. Colombo, A. Gkelias, E. Liu, G. Paltenghi, and K. K. Leung. "Efficient Cross-Layer Simulator for Performance Evaluation of Wireless Mesh Networks," in Proc. of ACM Simutools 2009, Rome, Italy. (pdf)

3. C. H. Liu, S. G. Colombo, A. Gkelias, E. Liu, and K. K. Leung. "An Efficient Cross-Layer Simulation Architecture for Wireless Mesh Networks," in Proc. of IEEE UKSim 2009, March 25-27, Cambridge, UK. (pdf)

4. C. H. Liu, K. K. Leung, and A. Gkelias. "Route Capacity Estimation Based Admission Control and QoS Routing for Mesh Networks," submitted to IEEE Globecom 2009, Hawaii, USA. 

Updated 28/10/2009

 

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