Master of Science

Date Completed: January 2007

Study and Implementation of IEEE 802.11 Physical Layer Model in YANS (Future NS-3) Network Simulator

Abstract:
Due to known difficulties of researchers in the networking domain regarding experimentation of their ideas in actual networks, network simulators have become indispensable tools for investigating and validating various ideas in all layers of the network. However, most of the wireless network researchers are not completely familiar with the implications of the assumptions they make for the physical layer in their scenarios. For the sake of building the case for a good simulator, it will be demonstrated that unknown assumptions might lead to wrong conclusions about the performance of the protocols under examination.

Having a feature-rich IEEE 802.11 Physical and MAC in a network simulator, which has more chance to be a realistic model, is of paramount interest to both Digital Communications researchers and Networking researchers. This thesis is an effort to study, design and implement a near-realistic IEEE 802.11a physical layer model, with all the phenomena associated with this layer.

YANS network simulator, a product of INRIA-Plan├Ęte group and father of the future NS-3 network simulator, is the simulator whose Physical layer is the basis of this thesis work. The implementation choices have been made based on the original architecture and with the intention of causing as little disturbance as possible to the original mechanics of the simulator.

As the principle objective, this thesis examines what it takes to have a feature-rich physical layer model, and then as the secondary goal, how these concepts could be implemented in the network simulator. Not all the explored concepts are part of the IEEE 802.11a standard, like the propagation models; nonetheless, they play a key role in having a realistic, and working, implementation.

We present the related concepts and implementation choices, where applicable, in a step-by-step approach within this thesis. Different propagation models, i.e., large-scale path loss models and fading, bit error rate calculation formulas depending on the type of modulation used and the specific channel type under examination, forward error correction mechanism employed in IEEE 802.11a and related issues, influence of Viterbi decoder on the bit error rate and, finally, bit error distribution models are the major issues elaborated in this work.

As a future work, it is envisaged to validate the results of IEEE 802.11 simulations with experiments done in ORBIT and/or Emulab testbeds. The intention of this work would be measurement-based validation of our models, by finding a set of physical layer configurations, based on which, a strong correlation between simulation and experimentation could be achieved.

Please Click Here to download my MSc thesis in PDF format.

Please Click Here to download the presentation file in PDF format.

Here is an interim Report of my MSc thesis, with a focus on implementation issues, from early November 2006.

 

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