IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

The design of the medium-access control (MAC) protocol is the most crucial aspect for high-speed and high-performance local and metropolitan area networks, since the decisions made at this level determine the major functional characteristics of these networks. Most of the MAC protocols proposed in the literature are not suitable for multimedia applications, since they have been designed with one generic traffic type in mind. As a result, they perform quite well for the traffic types they have been designed for, but poorly for other traffic streams with different characteristics. In this paper, we propose an integrated MAC protocol called the Multimedia-MAC (M-MAC), which integrates different MAC protocols into a hybrid protocol in a shared-medium network to efficiently accommodate various types of multimedia traffic streams with different characteristics and quality-of-service demands, namely, a constant-bit-rate traffic, bursty traffic (say, variable-bit-rate traffic), and emergency messages (say, control messages). We have developed a mathematical framework for the analysis and performance evaluation of our M-MAC protocol, which involves a queueing system with vacation. We have applied our M-MAC design approach to a wavelength-division multiplexing network, and evaluated its performance under various traffic conditions. © 2006 IEEE.

Department of Electrical Engineering

IEEE Transactions on Communications

Multimedia-MAC protocol: Its performance analysis and applications for WDM networks

Parallel scheduling algorithms are used extensively in the high-speed switches today. In order to benchmark the performance of various scheduling algorithms, it is of paramount importance to evaluate the performance under a traffic model that is more realistic. It makes more sense to study the performance of various scheduling algorithms under the correlated traffic, in the special context to the discovery of the highly correlated or self-similar nature or Long Range Dependence (LRD) of the Ethernet traffic. In this paper, a simple, linear discrete time model for the arrival of packets at the input of the high-speed switch is assumed. In sequel, a comparative study of the performance of various parallel-scheduling algorithms is undertaken.

The 7th International Conference on Advanced Communication Technology, ICACT 2005

Performance of parallel scheduling algorithms under correlated traffic

We address the problem of the performance analysis of the stochastic fair sharing (SFS) algorithm for fair link sharing. The SFS scheme has been proposed to carry out a fair link sharing and fair sharing among virtual private networks. Depending upon the current utilization and provisioned capacities of the classes, the SFS admission control algorithm decides which sessions to accept and which to reject. In this letter, we undertake the performance evaluation of the SFS scheme analytically. We explore the tradeoff between fairness and the blocking probability by varying the trunk reservation parameter. The results show that the analytical performance measure agrees well with the simulation results.

Performance Analysis of Stochastic Fair Sharing Scheme for Link Sharing

We address the problem of the performance analysis of the Stochastic Fair Sharing (SFS) algorithm for fair link sharing. The SFS scheme has been proposed in [1] to carry out a fair link sharing and fair sharing among Virtual Private Networks (VPNs). Depending upon the current utilization and provisioned capacities of the classes, the SFS admission control algorithm decides which sessions to accept and which to reject. In this paper, we undertake the performance evaluation of the SFS scheme analytically. The main performance measure in our analysis is the session blocking probability. In particular, we obtain the Roberts-Kaufman's like recursion for the SFS scheme to compute the blocking probability. We then use linear programming techniques to compute the blocking probability from the above recursion.

World University root node

IEEE International Conference on Communications

Performance analysis of Stochastic Fair Sharing (SFS) scheme for link sharing

Virtual output queueing (VoQ) in conjunction with matching algorithms have been proposed to overcome the HOL problem in input queued (IQ) high-speed switches. The dual round-robin matching (DRRM) scheme, has been shown to achieve good performance while being easy to build to high-speed and scalable switches. In this paper, we present a variant and improved version of the DRRM scheme, termed the pseudo-grant dual round-robin matching (PDRRM) algorithm. The PDRRM gives a pseudo-grant to a needy input to increase the number of matches per time slot. We have evaluated the PDRRM using extensive simulations. Our results demonstrate that using the "pseudo-grant" concept results in significant improvement in the performance of DRRM under different networking scenarios. In addition, PDRRM is conjectured to achieve an asymptotic 100% throughput for any arrival pattern. © 2002 IEICE.

IEEE International Conference on High Performance Switching and Routing, HPSR

The dual round robin pseudo-grant matching for high-speed packet switches

Correlated interarrival time Poisson process (CIPP) has been proposed in Proceedings of the Fifth Biennial Conference on Signal Processing and Communications (SPCOM'99), for modeling both the composite arrival process of packets in broadband networks and the individual video source modeling. The CIPP - a generalization of the Poisson process - is a stationary counting process and is parameterized by correlation parameter `ρ', the degree of correlation in adjacent interarrivals and `λ', the intensity of the process. In this paper, we develop the theory for CIPP/M/1 queue and undertake the performance modeling of statistical multiplexer with VBR video traffic in broadband networks using the CIPP/M/1 queue. We first derive the expressions for stationary distributions for queue length and waiting time in a CIPP/M/1 queue. Then, we derive the queuing performance measures of interest. For reasons of feasibility of theoretical performance modeling and realistic compulsions, we propose a deterministic smoothing with random (geometrically distributed) packet sizes. We simulate a queue with (thus smoothed) VBR video trace data as input to compare with the theoretical performance measures derived above. Experimental results show that the CIPP/M/1 queue models well the statistical multiplexer performance with the real-world MPEG-1 VBR video traffic input.

Performance Evaluation

CIPP - a versatile analytical model for VBR traffic

Conventional Medium Access Control (MAC) protocols perform quite well for the traffic types they have been designed for, but poorly for other traffic streams with different characteristics. But, the emerging multimedia applications require that the MAC protocol should perform equally well for all types of traffic characteristics. In this paper, we propose an integrated MAC protocol (herein termed as Multimedia Medium Access Control protocol (Multimedia-MAC)) which integrates different MAC protocols into a hybrid protocol to efficiently accommodate various types of multimedia traffic streams with different characteristics and QoS demands. We have applied our Multimedia-MAC design approach to wavelength division multiplexing (WDM) based optical network. We have developed a mathematical framework for the analysis and performance evaluation of our Multimedia-MAC protocol which involves a queueing model with vacation.

Modelling of multimedia MAC protocols on WDM optical networks

Correlated Interarrival time Process (CIPP) has been proposed in [1], for modeling both the composite arrival process of packets in broadband networks and the individual source modeling. The CIPP - a generalization of the Poisson process - is a stationary counting process and is parameterized by a correlation parameter `ρ' which represents the degree of correlation in adjacent interarrivals in addition to `λ' the intensity of the process. In this paper, we undertake the performance modeling of more realistic finite buffered statistical multiplexer with smoothed VBR video traffic input using CIPP/M/1/K queue. Queueing performance measures considered here are, packet loss probability and conditional packet loss probability. The buffer occupancy distribution in a queue with real-world MPEG-1 VBR video traffic is compared with that of its `best fit' CIPP/M/1/K. The above simulation results show that, the correlation in interarrivals degrades the queueing performance in the finite capacity queue case also. (In [2], we have shown analytically that the (positive) correlation in interarrivals in a CIPP/M/1 queue degrades the queueing performance). Finally, we consider the fluid-flow approximation of queues with CIPP arrivals to study the behavior of statistical multiplexer with VBR video traffic input. Comparisons with other models like, Markov chain, histogram model are also undertaken.

International Zurich Seminar on Digital Communications

CIPP and the performance modeling of VBR video traffic by CIPP/M/1/K queue

In this paper, we present two new schemes for finding human faces in a photograph. The first scheme adopts a distribution-based model approach to face-finding. Distributions of the face and the face-like manifolds are approximated using higher order statistics (HOS) by deriving a series expansion of the density function in terms of the multivariate Gaussian and the Hermite polynomials in an attempt to get a better approximation to the unknown original density function. An HOS-based data clustering algorithm is then proposed to facilitate the decision process. The second scheme adopts a hidden Markov model (HMM) based approach to the face-finding problem. This is an unsupervised scheme in which face-to-nonface and nonface-to-face transitions are learned by using an HMM. The HMM learning algorithm estimates the HMM parameters corresponding to a given photograph and the faces are located by examining the optimal state sequence of the HMM. We present experimental results on the performance of both schemes. A training data base of face images was constructed in the laboratory. The performances of both the proposed schemes are found to be quite good when measured with respect to several standard test face images.

Graphical Models

Locating Human Faces in a Cluttered Scene

In this paper, we propose a new traffic model (with correlations in interarrivals), herein referred to as Correlated Interarrival time Poisson Process (CIPP), for modeling the VBR video traffic. The CIPP - a generalization of the Poisson process with stationary increments - is parameterized by a correlation parameter `ρ' which represents the degree of correlation in adjacent interarrivals in addition to `λ' the intensity of the process. We present the theory for the CIPP/M/1 queue and derive the corresponding expressions for queueing performance measures of interest. We undertake the performance modeling of statistical multiplexer with VBR video traffic input using the CIPP/M/1 queue. The simulation results show that the CIPP/M/1 queue approximates well the queueing situation as encountered by the VBR traffic in broadband networks.

Conference Record / IEEE Global Telecommunications Conference

CIPP based characterization of VBR traffic and related statistical multiplexer performance

In this paper, we propose a new traffic model (with correlation in interarrivals) for composite arrival process of packets in broadband networks and individual source modeling. The traffic model involves a generalization of Poisson process which is referred to as correlated interarrival time Poisson process (CIPP). The CIPP, a stationary counting process, is parametrized by a correlation parameter ρ which represents the degree of correlation in adjacent interarrivals in addition to λ, the intensity of the process. It is shown by simulations that this arrival process models well the real-time traffic source, in particular the video source. The burstiness measure corresponding to this process is evaluated as defined in Saito et al. It turns out that although CIPP is not strictly a self-similar model, it does exhibit self-similar behaviour over a range of time scales. We explore, by simulations, the relation between the positive correlation in interarrivals and the estimated local Hurst parameter.

Journal of the Indian Institute of Science

Broadband teletraffic characterization using correlated interarrival time Poisson process (CIPP)

In this paper, we model the background network traffic by CIPP in an ATM multiplexer while simulating the end-to-end transport of real world VBR traffic over ATM networks. CIPP has been proposed by Manivasakan et al. (1999) for modeling broadband teletraffic. It was shown that, an empirical relationship exists between the parameter rho/ of CIPP and estimated local Hurst parameter H. This feature is made use of to study the effect of degree of self-similarity of background network traffic on various performance measures. The modeling and simulation results show the effect of self-similarity of the background process (as measured by rho/ of CIPP) on various performance measures parameterised by ATM multiplexer buffer size and decoder buffer size. © 1999 IEEE.

Proceedings - 3rd International Conference on Computational Intelligence and Multimedia Applications, ICCIMA 1999

End-to-end simulation of VBR traffic over ATM networks using CIPP network traffic model

Correlated Interarrival time Process (CIPP) has been proposed in Ref. 1, for modeling both the composite arrival process of packets in broadband networks and the individual source modeling. The CIPP - a generalization of the Poisson process - is a stationary counting process and is parameterized by a correlation parameter `ρ' which represents the degree of correlation in adjacent interarrivals in addition to `λ' the intensity of the process. In this paper, we present the performance modeling of VBR video traffic in ATM networks, using CIPP/M/1 queue. We first give the expressions for stationary distributions for CIPP/M/1 queue. Then, we derive the queueing measures of interest. We simulate a queue with smoothed VBR video trace data as input (with exponential services) to compare with the theoretical measures derived above. Experimental results show that the CIPP/M/1 queue, models well the ATM multiplexer performance with the real world VBR video traffic input.

Proceedings of SPIE - The International Society for Optical Engineering

CIPP - a versatile analytical model for VBR traffic in ATM networks

Two new schemes are presented for finding human faces in a photograph. The first scheme approximates the unknown distributions of the face and the face-like manifolds using higher order statistics (HOS). An HOS-based data clustering algorithm is also proposed. In the second scheme, the face to non-face and non-face to face transitions are learnt using a hidden Markov model (HMM). The HMM parameters are estimated corresponding to a given photograph and the faces are located by examining the optimal state sequence of the HMM. Experimental results are presented on the performance of both the schemes.