Kumar Appaiah

I am an Associate Professor in the Department of Electrical Engineering, Indian Institute of Technology Bombay.

From March 2013 till June 2014, I was working at Qualcomm Research on problems related to visible light communication. Before that, I was a graduate student in the Department of Electrical and Computer Engineering at the University of Texas at Austin. I successfully defended my Ph.D. dissertation in February 2013.

Contact

Office: 232-D, 2nd Floor, Electrical Engineering Building, IIT Bombay

E-mail: ee.iitb.ac.in, preceded by an @ sign, preceded by akumar

Education

• Ph. D., Electrical and Computer Engineering, The University of Texas at Austin, August 2008 - March 2013
• B.Tech. + M. Tech., Electrical Engineering, Indian Institute of Technology Madras, August 2003 - July 2008

Research

My work involves studying and quantifying the benefits and performance of multiple-input multiple-output (MIMO) concepts in optical and wireless communication systems systems. In particular, I aim to study different signaling as well as signal processing techniques which would enable efficient MIMO communication over optical fibers, as well as wireless communication links.

NPTEL Course: Digital Communication using GNU Radio

I have designed and recorded an NPTEL course titled Digital Communication using GNU Radio that teaches the concepts of digital communication using a mix of theory and some hands-on applications using the GNU Radio software. You can browse the videos here.

Useful Links

• Grading Assistant: A web app to assist with assigning grades. Currently customized for IIT Bombay, but easily usable by other universities and colleges. Get the source code. Patches welcome!
• Tips on writing good reports and making good presentations.

Publications

Journal

• A. Kumar, K. Appaiah, S. B. Pillai, “Carrier Phase and Frequency Discriminators for Receivers with One-Bit Quantization,” IEEE Transactions on Communications, to appear - 2025 (link)
• J. Ajith, K. Appaiah, “Energy Efficient Low-cost Gigabit Plastic Optical Fiber Links for Automotive Communication,” IEEE Communications Letters, to appear - 2025 (link)
• N. Kolla, P. Mehta, K. Appaiah, D. Pal, “Nested Grassmannian Codebooks for Quantizing MIMO Precoders on the Flag Manifold,” IEEE Communications Letters, vol. 29, no. 6 - 2025 (link)
• K. Ojha, K. Appaiah, “Mode separability in offset-based MGDM MMF links: a phase-retrieval-based approach,” Journal of the Optical Society of America B, vol. 41, no. 11 - 2024 (link)
• K. Ojha, J. Ajith, E. Lidiya, K. Appaiah, “Characterizing Mode Propagation in PMMA POFs with Intensity Measurements and Phase Retrieval,” IEEE Photonics Technology Letters, vol. 37, no. 7 - 2024 (link)
• P. Mehta, A. S. Bharath, K. Appaiah, R. Velmurugan, D. Pal, “Lattice All-Pass Filter based Precoder Adaptation for MIMO Wireless Channels,” IEEE Transactions on Vehicular Technology, vol. 73, no. 11 - 2024 (link)
• R. Chopra, C. R. Murthy, K. Appaiah, “Adaptive Data-Aided Time-Varying Channel Tracking for Massive MIMO Systems,” IEEE Transactions on Communications, vol. 72, no. 9 - 2024 (link)
• S. M. R. Rani, R. Chopra, K. Appaiah, “Statistical beamforming for cell free massive MIMO under mixed LoS/ NLoS channels,” Physical Communication, vol. 62, no. 1 - 2024 (link)
• P. Mehta, K. Appaiah, R. Velmurugan, D. Pal, “Matrix Unimodular Precoder Interpolation for MIMO-OFDM Wireless Communication Systems,” IEEE Communications Letters, vol. 27, no. 11 - 2023 (link)
• P. Mehta, K. Appaiah, R. Velmurugan, “Robust Direction-of-Arrival Estimation using Array Feedback Beamforming in Low SNR Scenarios,” IEEE Access, vol. 11, no. 1 - 2023 (link)
• K. Ojha, D. Mishra, K. Appaiah, D. Jain, “Optimizing graded-index few-mode fiber for space division multiplexing,” Optics Express, vol. 31, no. 13 - 2023 (link)
• P. Mehta, K. Appaiah, R. Velmurugan, D. Pal, “All-Pass Filter Design Using Unimodular Interpolation,” IEEE Signal Processing Letters, vol. 30, no. 1 - 2023 (link)
• K. P. Anoop, A. M. Reddy, M. S. Bhatia, A. K. Jain, R. Gopalakrishnan, M. Salekin, S. P. Singh, R. V. Satwik, S. Pulapadi, C. Bobade, I. S. Kumar, S. Gopalakrishnan, K. Appaiah, N. Rangaraj, M. N. Belur, “Rationalized Timetabling Using a Simulation Tool: A Paradigm Shift in Indian Railways,” INFORMS Journal on Applied Analytics, vol. 53, no. 4 - 2023 (link)
• A. S. Bharath, D. S. Gaharwar, K. Appaiah, D. Pal, “Design of discrete-time matrix all-pass filters using subspace Nevanlinna pick interpolation,” Signal Processing, vol. 204, no. 1 - 2023 (link)
• N. Kolla, K. Appaiah, R. Chopra, “Efficient parameterized precoder tracking in slowly time-varying MIMO channels,” IEEE Communications Letters, vol. 27, no. 1 - 2022 (link)
• A. Kumar, K. Appaiah, S. B. Pillai, “On the Sum Capacity Achieving Precoders and their CSI Requirements for MIMO-BC,” IEEE Communications Letters, vol. 26, no. 7 - 2022 (link)
• I. M. Baby, K. Appaiah, R. Chopra, “Optimal Channel Tracking and Power Allocation for Time Varying FDD Massive MIMO Systems,” IEEE Transactions on Communications, vol. 70, no. 2 - 2022 (link)
• M. B. Patil, R. D. Korgaonkar, K. Appaiah, “GSEIM: A General-purpose Simulator with Explicit and Implicit Methods,” Sadhana, vol. 46, no. 1 - 2021 (link)
• A. Radhakrishnan, R. Prasad, K. Appaiah, “Efficient multiplexing using delayed CSI in few-mode fiber links,” Optical Fiber Technology, vol. 66, no. 1 - 2021 (link)
• A. E. Bangera, K. Appaiah, “Quantum-confined ultra-wideband Si-based absorbers by a non-lithographic approach,” Solar Energy Materials and Solar Cells, vol. 230, no. 1 - 2021 (link)
• A. Miryala, I. M. Baby, K. Appaiah, S. B. Pillai, “A Post-Coder Feedback Approach to Overcome Training Asymmetry in MIMO-TDD,” IEEE Transactions on Vehicular Technology, vol. 70, no. 6 - 2021 (link)
• R. Arjun, H. Shah, S. Dhua, P. M. Krishna, K. Appaiah, V. M. Gadre, “Low Complexity FBMC for wireless MIMO systems,” Elsevier Physical Communications, vol. 47, no. 1 - 2021 (link)
• S. Nijhawan, A. Gupta, K. Appaiah, R. Vaze, N. Karamchandani, “Flag manifold based precoder interpolation techniques for MIMO-OFDM systems,” IEEE Transactions on Communications, vol. 69, no. 7 - 2021 (link)
• H. Rahman, A. Vinayachandran, S. R. B. Pillai, K. Appaiah, R. Vaze, N. Kashyap, “Deadline Constrained Packet Scheduling in the Presence of an Energy Harvesting Jammer,” IEEE Transactions on Green Communications and Networking, vol. 5, no. 1 - 2021 (link)
• A. E. Bangera, K. Appaiah, “Three-Dimensional Grids of Optimized Ti-Compounds on Si for Ultra-Wideband Optical Absorption,” ACS Applied Materials & Interfaces, vol. 12, no. 35 - 2020 (link)
• M. Madan, A. Gupta, K. Appaiah, “Scalar Feedback based Joint Time-Frequency Precoder Interpolation for MIMO-OFDM Systems,” IEEE Wireless Communications Letters, vol. 9, no. 9 - 2020 (link)
• A. Radhakrishnan, K. Appaiah, “Mode Subset Selection and Feedback for Low Complexity Equalization in DWDM MMF Links,” IEEE Communications Letters, vol. 24, no. 8 - 2020 (link)
• A. E. Bangera, K. Appaiah, “Tunable wettability and prediction of total surface energy for nanocoatings: An empirical model,” Surface and Coatings Technology, vol. 383, no. 1 - 2020 (link)
• K. Appaiah, D. Pal, “All-Pass Filter Design Using Blaschke Interpolation,” IEEE Signal Processing Letters, vol. 27, no. 1 - 2020 (link)
• A. E. Bangera, K. Appaiah, “A conditional justification for the determination of surface energy of solids using contact angle methods,” Materials Chemistry and Physics, vol. 234, no. 1 - 2019 (link)
• J. C. Jacob, K. Appaiah, “Mode multiplexing using Principal Modes in Few-mode Fiber Links with Delayed Feedback,” IEEE Communications Letters, vol. 23, no. 8 - 2019 (link)
• R. Prasad, K. Appaiah, “Impact of modulation bandwidth on multiplexing using principal modes in MMF links,” Optics Express, vol. 26, no. 2 - 2018 (link)
• J. C. Jacob, R. Mishra, K. Appaiah, “Quantization and Feedback of Principal Modes for Dispersion Mitigation and Multiplexing in Multimode Fibers,” IEEE Transactions on Communications, vol. 64, no. 12 - 2016 (link)
• K. Appaiah, S. Vishwanath, S. R. Bank, “Impact of Fiber Core Diameter on Dispersion and Multiplexing in Multimode-Fiber Links,” OSA Optics Express, vol. 22, no. 14 - 2014 (link)
• K. Appaiah, S. Zisman, A. K. Das, S. Vishwanath, S. R. Bank, “Analysis of Laser and Detector Placement in Incoherent MIMO Multimode Fiber Systems,” IEEE/OSA Journal of Optical Communications and Networking, vol. 6, no. 4 - 2014 (link)
• K. Appaiah, S. Vishwanath, S. R. Bank, “Vector Intensity-Modulation and Channel State Feedback for Multimode Fiber Optic Links,” IEEE Transactions on Communications, vol. 61, no. 7 - 2013 (link)
• K. Appaiah, R. Salas, S. Vishwanath, S. R. Bank, “Offset Coupling, Feedback, and Spatial Multiplexing in 4 × 4 Incoherent-MIMO Multimode Fiber Links,” Journal of Lightwave Technology, vol. 31, no. 17 - 2013 (link)
• K. Appaiah, S. Vishwanath, S. R. Bank, “Device Design and Signal Processing for Multiple-Input Multiple-Output Multimode Fiber Links (Invited),” Proc. of SPIE, vol. 8267, no. 1 - 2012
• K. Appaiah, S. Vishwanath, S. R. Bank, “Advanced Modulation and Multiple-Input Multiple-Output for Multimode Fiber Links,” IEEE Photonics Technology Letters, vol. 23, no. 20 - 2011 (link)

Conference

• S. Mulleti, K. Appaiah, S. R. B. Pillai, “Low-Rate Modulo Folded ADC for Detecting Linearly Modulated Communication Symbols,” IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP) - 2025 (link)
• A. Kumar, K. Appaiah, S. R. B. Pillai, “Resolving the DMD-crosstalk trade-off in SDM through graded-index FMF,” 2025 National Conference on Communications (NCC) - 2025 (link)
• K. Ojha, D. Mishra, K. Appaiah, D. Jain, “Resolving the DMD-crosstalk trade-off in SDM through graded-index FMF,” Next-Generation Optical Communication: Components, Sub-Systems, and Systems XIII - 2024 (link)
• A. Kumar, K. Appaiah, S. R. B. Pillai, “On the Ergodic Sum Capacity of Multi-User MIMO with Distributed Transmitter,” 2023 IEEE International Conference on Communications (ICC) - 2023 (link)
• P. Mehta, K. Appaiah, R. Velmurugan, “Direction-of-Arrival Estimation using Location Unaware Linear Array,” 2023 57th Asilomar Conference on Signals, Systems, and Computers - 2023 (link)
• R. D. Kamble, K. Appaiah, “Impact of Component Sensitivity on Biquad Equalizer based Plastic Optical Fiber Links,” 2023 International Conference for Advancement in Technology (ICONAT) - 2023 (link)
• D. Mishra, K. Ojha, K. Appaiah, D. Jain, “Germania Glass-Based Negative-Curvature Hollow-Core Fiber for Mid-IR Applications,” Frontiers in Optics - 2022 (link)
• R. D. Kamble, K. Appaiah, “Biquad filter based equalization for PMMA SI-POF links,” 2022 IEEE International Conference on Signal Processing and Communications (SPCOM) - 2022 (link)
• K. Ojha, K. Appaiah, “Feedback based Compensation of Second Order Modal Dispersion in Principal Mode based Multiplexed MMF Links,” 2022 National Conference on Communications (NCC) - 2022 (link)
• A. Radhakrishnan, K. Appaiah, “Multiplexed Principal Modes in Few-Mode Fiber Links With Limited Delayed Feedback,” 2022 National Conference on Communications (NCC) - 2022 (link)
• H. Rahman, A. Vinayachandran, S. B. Pillai, K. Appaiah, R. Vaze, “A Game Theoretic Model for Deadline Constrained Packet Scheduling with an Energy Harvesting Jammer,” 2020 International Conference on Computing, Networking and Communications (ICNC) - 2020 (link)
• P. Sankhe, S. Azim, S. Goyal, T. Choudhary, K. Appaiah, S. Srikant, “Indoor Distance Estimation using LSTMs over WLAN Network,” 2019 16th Workshop on Positioning, Navigation and Communications (WPNC) - 2019 (link)
• M. Khaturia, K. Appaiah, A. Karandikar, “On Efficient Wireless Backhaul Planning for the Frugal 5G Network,” 2019 IEEE Wireless Communications and Networking Conference Workshop (WCNCW) - 2019 (link)
• P. Agrawal, K. Appaiah, “Kalman Filter Based Channel Tracking for Precoded GFDM Systems,” TENCON 2019 - 2019 IEEE Region 10 Conference - 2019 (link)
• A. Bangera, K. Appaiah, S. Chakrabarti, “Surface engineering using compounds of titanium nanocoatings for silicon based optical devices,” SPIE Photonics West - 2019 (link)
• A. Gupta, K. Appaiah, R. Vaze, “Predictive Quantization and Joint Time-Frequency Interpolation technique for MIMO-OFDM precoding,” 2019 IEEE International Conference on Communications (ICC) - 2019
• N. Murali K. Appaiah, “Keyboard Side Channel Attacks on Smartphones Using Sensor Fusion,” 2018 IEEE Global Communications Conference (GLOBECOM) - 2018 (link)
• V. Arya, K. Appaiah, “Kalman Filter Based Tracking for Channel Aging in Massive MIMO Systems,” 2018 International Conference on Signal Processing and Communications (SPCOM) - 2018
• R. Prasad, K. Appaiah, “Utility of Delayed CSI Feedback in Mode Division Multiplexed Multimode Fiber Links,” 2018 International Conference on Signal Processing and Communications (SPCOM) - 2018
• J. C. Jacob, K. Appaiah, “Limited Feedback and Interpolation of Principal Modes in Spatially Multiplexed WDM Fiber Links,” 2018 International Conference on Signal Processing and Communications (SPCOM) - 2018
• A. R, A. Sukhwani, K. Appaiah, V. Gadre, “Non-orthogonal Transmultiplexers for FBMC with Controlled ISI,” 2018 International Conference on Signal Processing and Communications (SPCOM) - 2018
• J. C. Jacob, K. Appaiah, “Multiplexing using principal modes in spliced MMFs with mode dependent losses,” 2017 Twenty-third National Conference on Communications (NCC) - 2017
• R. Mishra, J. C. Jacob, K. Appaiah, “Quantization and Feedback of Principal Modes for High Speed Multimode Fiber Links,” IEEE International Conference on Communications (ICC), Kuala Lumpur - 2016 (link)
• R. Mishra, J. C. Jacob, K. Appaiah, “Limited feedback of principal modes for high speed multimode fiber links,” 2015 Workshop on Recent Advances in Photonics (WRAP), Bengaluru - 2015 (link)
• K. S. Sanila, K. Appaiah, “Low Complexity Equalization Using Mode-Subset Selection in MIMO Multimode Fiber Links,” IEEE Global Communications Conference (GLOBECOM), San Diego, CA - 2015 (link)
• K. Appaiah, “Detector and Mode Subset Selection for DSP based Multimode Fiber Links (Invited),” Twenty First National Conference on Communications (NCC), Mumbai - 2015 (link)
• K. Appaiah, R. Salas, S. Vishwanath, S. R. Bank, “Enhancing Data Rates in Graded-Index Multimode Fibers with Offset Coupling and Multiplexing,” Optical Fiber Communication Conference, Anaheim, CA - 2013 (link)
• K. Appaiah, S. Zisman, S. Vishwanath, S. R. Bank, “Analysis of Laser and Detector Placement in MIMO Multimode Optical Fiber Systems,” IEEE International Conference on Communications (ICC), Ottawa, ON - 2012 (link)
• K. Appaiah, S. Vishwanath, S. R. Bank, “Device Design and Signal Processing for Multiple-Input Multiple-Output Multimode Fiber Links (Invited),” SPIE OPTO, San Francisco, CA - 2012
• K. Appaiah, S. Zisman, S. Vishwanath, S. Bank, “Dynamic Detector Selection for Multiple-Input Multiple-Output (MIMO) Multimode Fiber Links,” CLEO: Science and Innovations, San Jose, CA - 2012 (link)
• O. O. Koyluoglu, K. Appaiah, H. Si, S. Vishwanath, “Expansion Coding: Achieving the Capacity of an AEN Channel,” IEEE International Symposium on Information Theory Proceedings (ISIT), Boston, MA - 2012 (link)
• K. Appaiah, O. O. Koyluoglu, S. Vishwanath, “Polar Alignment for Interference Networks,” 49th Annual Allerton Conference on Communication, Control, and Computing, Allerton, IL - 2011 (link)
• K. Appaiah, S. Vishwanath, S. R. Bank, “Multiple-Input Multiple-Output with Predistortion and Signal Processing for Multimode Fiber Links,” CLEO: Science and Innovations, Baltimore, MD - 2011 (link)
• K. Appaiah, A. Ashikhmin, T. L. Marzetta, “Pilot Contamination Reduction in Multi-User TDD Systems,” IEEE International Conference on Communications (ICC), Cape Town, South Africa - 2010 (link)