

Ph.D. (2006  2014)
Dept. of Electrical Communication Engg.,
Indian Institute of Science,
Bangalore.
B.Tech in Electronics and Communication Engineering, (2002  2006)
College of Engineering,
Trivandrum.
AV324, AV312  Communication Systems II (earlier Digital Communication)
January  May 2020, 2019
July  November, 2016, 2015
AV343, AV332  Communication Systems Lab (earlier Digital Communication Lab)
January  May 2020, 2019
July  November, 2016
AV314  Communication Systems I
July  November, 2020, 2019, 2018
AV316  Digital Signal Processing (Engineering Physics)
July  November, 2017
AV336  Digital Signal Processing Lab (Engineering Physics)
July  November, 2017
AV224  Computer Organization and Operating Systems
January  May, 2017
AV222  Microprocessors and Microcontrollers
January  May, 2016
AVD611  Advanced Signal Analysis and Processing
July  November, 2015
AVD612  Mathematical methods for signal processing
July  November, 2019
AVD613  Communication Systems I
July  November, 2020, 2018, 2017, 2016
AVD623  Communication Systems II
January  May, 2018, 2017, 2016
AVD631  Communication Systems Lab
July  November, 2020, 2018
AV467  Introduction to Optimization
January  May, 2018,
AV834, AV499 and AVD871  Applied Markov Decision Processes and Reinforcement Learning (B.Tech and M.Tech elective)
January  May 2020, 2019
July  November, 2018
Research Methodology  Software, July  November, 2020, 2018
Assistant Professor (2017  Present)
Department of Avionics,
Indian Institute of Space Science and Technology,
Trivandrum.
Visiting Faculty Member (2015  2017)
Department of Avionics,
Indian Institute of Space Science and Technology,
Trivandrum.
Research and Development Manager (2014  2015)
Flytxt Pvt. Ltd.,
Trivandrum.
My research interests lies in the development and application of models and analytical tools for performance analysis and optimization of engineering systems. Specifically, I am interested in the development and application of queueing models and analytical tools for communication and computer networks. However, I am also interested in several other problems. Please read on to find what all I am working on as well as related publications.
Stability and delay performance for wireless systems with reconfiguration delay
We consider wireless downlinks where the base station switches between different users in order to transmit data intended for the respective users. When switching between users, the logical links between the user and the base station need to be configured. For example, the user’s state may need to be changed from an idle to an active state. This incurs a reconfiguration delay, which is the delay between the time at which the base station scheduler decides to serve the user and the time at which the actual data transmission starts. Motivated by such scenarios, we consider the stability region and throughput optimal scheduling for a wireless downlink model with random connectivity over time and reconfiguration delay. We have also looked at the problem of minimizing average delay for wireless systems with reconfiguration delay when the channel connectivity is correlated
J4: Scheduling Policies for Wireless Downlink with Correlated Random Connectivity and Multislot Reconfiguration Delay, with Amit Kumar  Accepted to IEEE Communications Letters.
C11: Throughput Optimal Scheduling for Wireless Downlinks with Reconfiguration Delay  accepted to NCC 2018.Extended version of paper submitted to NCC2018
Stability and delay analysis for delay tolerant networks with random packet arrivals
Our research objective is to theoretically analyze the stability of queues and average delay of messages in a delay tolerant network. We consider a simple delay tolerant network model with the source spray and wait routing protocol without feedback for our initial analysis. This is work in progress. Some approximations to the average queueing delay has been obtained by interpreting the system as a M^{K}/G/N system. Simulation code for this work is available here.
C9: Stability and delay analysis of delay tolerant networks with random message arrivals, with Sarath A. Y. and Chandramani Singh  COMSNETS, 2017.
C13: Stability properties of delay tolerant networks with buffered relay nodes, with Chandramani Singh  CCDWN, 2018. (Extended version of paper submitted to CCDWN)
Bayesian quickest detection for active sensors
Active sensors use radar, ultrasound, or optical sensing to control the information content in the sequentially collected noisy data. Using such active sensing to increase the extent of collected information, it is possible to quickly detect changes in the environment. However, increasing the extent of information contained in the collected data would lead to a cost or energy expenditure, where the cost would naturally increase as the extent of contained information increases. For such a sensor, our objective is to design control policies that optimally trade off performance metrics such as detection delay, average cost expended in control, and probability of false alarm. We consider this problem in the setting of Bayesian quickest change detection. Our preliminary results can be found in the following paper.
J3: Bayesian quickest change detection for active sensors  In IEEE Communications Letters, November 2016.
Optimal addition of links to a communication network
The quality of service offered by a communication network to its users can be improved by the addition of communication links between appropriate nodes in the network. We pose this link addition problem as an optimal edge addition problem in graphs. Some of our preliminary results are given in the following paper, where we have considered a simple linear graph.
J2: Analytical Identification of Anchor Nodes in a SmallWorld Network, with Abhishek Chakraborty and B. S. Manoj  In IEEE Communications Letters, 2016.
Power delay tradeoff for dynamic data compression and transmission over a wireless channel
In power constrained sensor networks and satellite telemetry systems there arises scenarios where multiple sensors produce data which is correlated. We consider a communication scenario where a powerlimited transmitter aggregates correlated data from different sources for transmission to a sink over a wireless fading channel. In order to reduce the average queueing delay, the transmitter could compress the data before transmission. We note that it is not obvious that compressing the data to the maximum extent possible leads to the best possible tradeoff. Prior work has found that although wireless transmission of a bit can require energy over a 1000 times more than a single 32bit computation, compression using typical algorithms (LZW) may actually lead to larger power expenditure, due to power expensive memory accesses. So both data compression as well as wireless transmission expends comparable amounts of power which is a precious resource for the transmitter. We consider the problem of designing joint compression and transmission policies for the transmitter which can optimally tradeoff the average queueing delay of the transmitted data with the average total power of compression and transmission. Our preliminary results are reported in this work.
C8: Power delay tradeoff for dynamic data compression and transmission over a wireless channel, with Utpal Mukherji  In Signal Processing and Communication Conference, Bangalore  2016.
We studied the tradeoff of average delay with average service cost and average utility, for single server queueing models without and with admission control. We considered continuous time and discrete time queueing models with a random environment. The tradeoff problem is studied for the class of monotone scheduling policies, i.e., scheduling policies for which the service rate is a nondecreasing function of the queue length for each environment state. The continuous time and discrete time queueing models that we considered are motivated by crosslayer models for pointtopoint links with random packet arrivals and fading at slow and fast time scales. Our objective is motivated by the need to optimally tradeoff the average delay of the packets (a network layer performance measure), with the average service cost of transmitting the packets, e.g. the average power required for transmission (a physical layer performance measure), under a lower bound constraint on the average throughput. We also considered the problem of optimally trading off the average delay and average error rate of randomly arriving message symbols which are transmitted over a noisy pointtopoint link. It is intuitive that to keep a queue stable under a lower bound constraint on the average utility, a minimum number of customers have to be served per unit time. This in turn implies that queue stability requires a minimum average service cost expenditure. In this thesis, we obtain primarily an asymptotic characterization of the minimum average delay for monotone policies, subject to an upper bound constraint on the average service cost and a lower bound constraint on the average utility, in the asymptotic regime where the average service cost constraint is made arbitrarily close to the above minimum average service cost. The results are presented in J1, C4, and C5. This is also presented in the thesis.
J1: Asymptotic Bounds on the PowerDelay Tradeoff for Fading PointtoPoint Links From Geometric Bounds on the Stationary Distribution of the Queue Length, with Utpal Mukherji  In IEEE Transactions on Information Theory, 2015.
C4 : Tradeoff of average power and average delay for a pointtopoint link with fading, with Utpal Mukherji  In Proceedings of the National Conference on Communications (NCC), 2013.
C5 : Tradeoff of average service cost and average delay for the state dependent M/M/1 queue, with Utpal Mukherji  In Proceedings of the National Conference on Communications (NCC), 2013.
Reliable and delayoptimal communication of bursty sources over communication channels (DRDOIISc programme on mathematical engineering)
An understanding of communication networks is possible only if queueingtheoretic and informationtheoretic aspects of communication are considered as a whole. Classical information theory assumes that sources always have information to send and characterizes performance through metrics such as capacity regions and the asymptotic dependence of error probability on coding length. But real world sources produce information that is bursty in nature. The bursty nature of sources has two main implications : a) a bursty source uses the channel resources intermittently thus presenting a time varying channel to the other sources in the network, and b) the random nature of information production and its transmission leads to queueing at the transmitters and resource scheduling problems. In this project, we restricted ourselves to understanding the implication (b) by considering simple discrete time pointtopoint channels. We studied the queueing process at the transmitter of a pointtopoint channel with a refined information theoretic model, based on the channel coding error exponent, for the transmission scheme. For pointtopoint channels using variable length block codes, that guarantee a constant error probability per transmission, we obtain an approximately averagedelayoptimal policy, presented in C1 and T1. We also obtain analytical upper and lower bounds on the minimum average delay, presented in C3 and T2. For pointtopoint channels using block coding we obtain the exponential decay rate of average error probability with average delay for both ﬁxed and variable length block coding in C2 and T3. Furthermore for fixed block length coding schemes we obtain upper and lower bounds on the tradeoff in C2. In T4 we show that using streaming codes the exponential decay rate of average error probability with average delay can be improved from what that is achieved by block coding schemes. We then consider the problem of allocating transmitter power, for channel inversion, for a slow fading pointtopoint channel in T5. Approximations to the optimal allocation are obtained when the average delay is allowed to be large or equivalently when the available average transmitter power is reduced.
C1 : Averagedelay optimal policies for the pointtopoint channel with Utpal Mukherji  In proceedings of the 7th international symposium on modeling and optimization in mobile, ad hoc, and wireless networks (WiOpt), 2009.
C2 : Queueing delay  error probability tradeoff for pointtopoint channels with fixed length block codes, with Utpal Mukherji  In proceedings of the IEEE International symposium on Information Theory (ISIT), 2011.
C3 : Delay optimal scheduling of a discrete time batch service queue for pointtopoint channel code rate selection, with Utpal Mukherji  In proceedings of the National Conference on Communications (NCC), 2012.
T1 : Averagedelay optimal policies for the pointtopoint channel, TRPME201013, 2010
T2 : Bounds on the optimal queueing delay for variable rate pointtopoint channels with fixed block error probability, TRPME201111, 2011.
T3 : Queueing delay  error probability tradeoff for pointtopoint channels using block codes, TRPME201112, 2011.
T4 : Queueing delay  error probability tradeoff for pointtopoint channels using streaming codes, TRPME201113, 2011.
T5 : Tradeoff of average power and average delay for slow fading pointtopoint channels under reliability constraints, TRPME201114, 2011.
My teaching interests are in
My research interests lies in the development and application of models and analytical tools for performance analysis and optimization of engineering systems. Specifically, I am interested in the development and application of queueing models and analytical tools for communication and computer networks. However, I am also interested in several other problems. Please read on to find what all I am working on as well as related publications.
J4: Scheduling Policies for Wireless Downlink with Correlated Random Connectivity and Multislot Reconfiguration Delay, with Amit Kumar  In IEEE Communications Letters, February 2018.
J3: Bayesian quickest change detection for active sensors  In IEEE Communications Letters, November 2016.
J2: Analytical Identification of Anchor Nodes in a SmallWorld Network, with Abhishek Chakraborty and B. S. Manoj  In IEEE Communications Letters, June 2016.
J1: Asymptotic Bounds on the PowerDelay Tradeoff for Fading PointtoPoint Links From Geometric Bounds on the Stationary Distribution of the Queue Length, with Utpal Mukherji  In IEEE Transactions on Information Theory, 2015.
C22: Design of Joint Relay Placement and Scheduling Algorithms for TimeSlotted Networks with HalfDuplex Constraints, with Harshavardhana T. G. and Pragya Shah, COMSNETS 2021.
C21: On the average and peak ageofinformation for BerkeleyMAC protocol, with Govind A. M, ANTS 2020.
C20: Pano2RSSI: Generation of RSSI maps for a room environment from a single panoramic image, with Nibin Raj and D.V.V. Sai Teja, ANTS 2020.
C19: Optimal Downlink Scheduling and Power Allocation with Reconfiguration Delay, with Gowri M., and Premkumar K., COMSNETS 2020.
C18: Minimum delay scheduling under average power constraint for 802.11ax uplink, with Binoy B, ANTS 2019.
C17: A study of Average and Peak AgeofInformation for MAC protocols in Contiki, ANTS 2019.
C16: Signal Design and Detection Algorithms for Quick Detection Under False Alarm Rate Constraints, with Alamuru Pavan Kumar, NCC 2019.
C15: On the Evolution of FiniteSized Complex Networks with Constrained Link Addition, with Abhishek Chakraborty and B. S. Manoj, ANTS 2018.
C14: Empirical Delay Models for 802.11 under Deterministic Convergecast Traffic, with Anand Ramesh  ANTS 2018.
C13: Stability properties of delay tolerant networks with buffered relay nodes, with Chandramani Singh  CCDWN 2018.
C12: Optimal Association of Wireless Devices to Cellular and WiFi Base Stations, with Chandramani Singh  NCC 2018.
C11: Throughput Optimal Scheduling for Wireless Downlinks with Reconfiguration Delay  NCC 2018.
C10: Power control and crosslayer design of RPL objective function for low power and lossy networks, with Harshavardhana T. G., SVR Anand, and Malati Hegde  COMSNETS, 2018.
C9: Stability and delay analysis of delay tolerant networks with random message arrivals, with Sarath A. Y. and Chandramani Singh  COMSNETS, 2017.
C8: Power delay tradeoff for dynamic data compression and transmission over a wireless channel, with Utpal Mukherji  In Proceedings of Signal Processing and Communications, IISc, 2016.
C7: Influence of Greedy Reasoning on Network Evolution, with Abhishek Chakraborty and B. S. Manoj  IndoUS Bilateral Workshop on Large Scale Complex Network Analysis 2015 (LSCNA  2015)
C6: On powerlaw decay exponents and Barabasi models for subscriber usage behaviour in mobile networks, with Jobin Wilson and Prateek Kapadia  In Proceedings of the National Conference on Communications (NCC), 2015.
C5 : Tradeoff of average service cost and average delay for the state dependent M/M/1 queue, with Utpal Mukherji  In Proceedings of the National Conference on Communications (NCC), 2013.
C4 : Tradeoff of average power and average delay for a pointtopoint link with fading, with Utpal Mukherji  In Proceedings of the National Conference on Communications (NCC), 2013.
C3 : Delay optimal scheduling of a discrete time batch service queue for pointtopoint channel code rate selection, with Utpal Mukherji  In proceedings of the National Conference on Communications (NCC), 2012.
C2 : Queueing delay  error probability tradeoff for pointtopoint channels with fixed length block codes, with Utpal Mukherji  In proceedings of the IEEE International symposium on Information Theory (ISIT), 2011.
C1 : Averagedelay optimal policies for the pointtopoint channel with Utpal Mukherji  In proceedings of the 7th international symposium on modeling and optimization in mobile, ad hoc, and wireless networks (WiOpt), 2009.
T1 : Averagedelay optimal policies for the pointtopoint channel, TRPME201013, 2010
T2 : Bounds on the optimal queueing delay for variable rate pointtopoint channels with fixed block error probability, TRPME201111, 2011.
T3 : Queueing delay  error probability tradeoff for pointtopoint channels using block codes, TRPME201112, 2011.
T4 : Queueing delay  error probability tradeoff for pointtopoint channels using streaming codes, TRPME201113, 2011.
T5 : Tradeoff of average power and average delay for slow fading pointtopoint channels under reliability constraints, TRPME201114, 2011.