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Communication Networks

Communication Networks. Prof. D. Manjunath manju@ee.iitb.ac.in.

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Communication Networks

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  1. Communication Networks Prof. D. Manjunath manju@ee.iitb.ac.in Indian Institute of Technology Bombay

  2. Recent Research and ProjectsInternet Pricing and Queue Control Wireless Networks Internet Measurement and Analysis Voice over IP Technologies Optical Networks Packet Switch Architectures Indian Institute of Technology Bombay

  3. Academia Industry Meet 2002, Electrical Engineering Department Internet Pricing and Queue Control Join Minimum Cost Queue • Parallel queues with single server providing round robin service • Each queue has a join price and congestion is posted • Arrivals use a disutility f(price,queue) that is increasing in price and queue and joins the queue for which the disutility is minimum • Motivation from Tirupati queues Indian Institute of Technology Bombay

  4. Academia Industry Meet 2002, Electrical Engineering Department Results: We show that for single class with linear cost function, the system is nearly socially optimal Use truncation models and reduce the problem to Quasi Birth Death Models for analysis in the presence of multiclass customers Use a dynamic price adaptation scheme to maintain the queue lengths at prescribed levels and analyse using o.d.e. approach to stochastic approximation Indian Institute of Technology Bombay

  5. Academia Industry Meet 2002, Electrical Engineering Department Wireless Networks • Power control and its analysis using stochastic Approximation techniques. • Simplified derivation for the critical transmission range using results from geometric random graphs • Exact connectivity expression for finite networks • Scheduling in Ad Hoc Networks for special purpose communication like gossiping: motivation from distributed control using ad hoc networks Indian Institute of Technology Bombay

  6. Academia Industry Meet 2002, Electrical Engineering Department Internet Measurement and Analysis • Construct user based models: How does a end-user use the Internet? • Develop passive and active algorithms to measure the “Local Internet” • Summary of recent results • Entropy of the destination set from a LAN is very • low -- 3-5 bits! • Hoggers are hoggers over long and short time scales • Sampling can be used to know the “destination” • profile from a sink Continued Indian Institute of Technology Bombay

  7. Academia Industry Meet 2002, Electrical Engineering Department Internet Measurement and Analysis • Local Topology does not change frequently • Loss is infrequent but delay variation is • significant • Work in progress: • Active techniques to characterise delays and losses in forward and reverse links and paths. • Development of Arrowsmith tool for Local Internet characterisation. Indian Institute of Technology Bombay

  8. Academia Industry Meet 2002, Electrical Engineering Department Optical Networks • Efficient virtual topology sequence for • multiperiod design. • Apply “simple” well known algorithms to resource • allocation problems in Optical Networks – • Edge Disjoint Path and its applicability to Routing and Wavelength Assignment; • Vehicle Routing Problems to Grooming; • Time dependent solutions of queues to capacity allocation and expansion Indian Institute of Technology Bombay

  9. Academia Industry Meet 2002, Electrical Engineering Department Packet Switching Architectures • Extensive analysis of copy networks and • multicast switches • Extensive continuous time analysis of input • queued packet switches to deal with variable • length packets and interarrival times • drawn from continuous distributions. Indian Institute of Technology Bombay

  10. Academia Industry Meet 2002, Electrical Engineering Department In the not too distant past • Queueing Theory and Stochastic Processes • A bivariate exponential distribution using linear • structures and using it to model queues with • correlations in the arrival and service times. • Queue Inference Algorithms: Passive estimation • algorithms of queue length and waiting times • using transaction information. Also • applications to many WANs and LANs.. • Integral Expressions for Normalising Constant • in generalised product form networks Continued Indian Institute of Technology Bombay

  11. Academia Industry Meet 2002, Electrical Engineering Department In the not too distant past QNAT: • Queueing Network Analysis Tool for use with Mathematica • Over 1000 downloads and good feedback. Multiple Access Networks: • Bandwidth Allocation Schemes in Unidirectional Bus Networks • Performance analysis of random access protocols for ring topology networks • Renewal models for inter-LAN traffic Multicasting: • Closed queueing network models with fork-join nodes to analyse throughput properties. Indian Institute of Technology Bombay

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