Publications

To get a quick summary, click on [Short discription]. To get a more colorful summary, click on the [Handout]!

Journal/Magazine Papers and Preprints

Decentralized control



6. [CSM '10] Pulkit Grover and Anant Sahai, Demystifying the Witsenhausen Counterexample. IEEE Control Systems Magazine, vol. 30, no. 6, pp. 20-24, Dec. 2010.


5. [TIT '10 Sub.] Pulkit Grover, Aaron B. Wagner and Anant Sahai, Information Embedding Meets Distributed Control. IEEE Transactions on Information Theory, Submitted (2010). [Short description] [PDF] [MATLAB code]
   
   Building on our work in [IJSCC 2010] paper, this paper derives an improved outer bound to the asymptotically infinite length Witsenhausen's counterexample, characterizing the optimal cost to within a factor of 1.3 of the optimal (an improvement from a factor of 2 earlier). The minimum required power for zero distortion is obtained exactly. Upper and lower bounds on cost are also derived for a problem where the first controller wants to communicate an explicit message to the second controller.


4. [TAC '10 Sub.] Pulkit Grover, Anant Sahai and Se Yong Park, The finite-dimensional Witsenhausen counterexample. IEEE Transactions on Automatic Control, Submitted (2010). [Short description] [PDF] [Talk Handout] [Talk Slides][MATLAB code]
   
   An approximate solution to Witsenhausen's counterexample: we show that quantization based strategies can obtain within a factor of 8 of the optimal costs for the original (scalar) Witsenhausen counterexample for all values of the problem parameters. Further, lattice based strategies obtain within a constant factor of optimal for vector Witsenhausen counterexample of any length. These are first results that show approximate optimality of any scheme for this longstanding problem.
   


3. [IJSCC '10] Pulkit Grover and Anant Sahai, Vector Witsenhausen Counterexample as Assisted Interference Suppression. Special Issue on "Information Processing and Decision Making in Distributed Control Systems" of the International Journal of Systems, Control and Communications (IJSCC), 2010. [Short description]
   
   This paper put forth a novel approach to solving (approximately) the Witsenhausen counterexample. SomeIn 1967, Witsenhausen formulated a seemingly simple problem to demonstrate that decentralized control problems can be hard. That problem, now infamously called Witsenhausen's counterexample, is still unsolved. In 1986, Papadimitrou and Tsitsiklis showed that the discrete version of the problem is NP-complete. Faced with this conclusion, the research community has resorted to heuristics for obtaining good strategies. However, these approaches provide no guarantee on their gap from optimality.
   
   Recognizing the importance of implicit communication in decentralized control systems, we approach the counterexample in an otherwise counterintuitive way: we first address an asymptotic version of the problem. Using tools from information theory, we provide approximately optimal solutions that are guaranteed to attain within a uniform constant factor of the optimal for the asymptotic version of the counterexample (this paper). Performing a finer analysis, we then obtain approximation results for the original (scalar) counterexample and its vector extensions (Trans. Auto. Control, Submitted, presented at ConCom '09).
   
   Our approach also extends to quite a few decentralized control problems beyond the original counterexample. See conference publications in decentralized control.




Green radios



2. [JSAC '11] Pulkit Grover, Kristen Ann Woyach and Anant Sahai, Towards a communication-theoretic understanding of system-level power consumption, IEEE Journal of Selected Areas in Communication (JSAC) Special Issue on Energy-Efficient Wireless Communications, to appear. [PDF][MATLAB Code]



Coding theory



1. [TIT '07] Pulkit Grover and Ajit Kumar Chaturvedi, Upper Bounds on the Rate of LDPC codes for a class of Finite State Markov Channels, IEEE Transactions on Information Theory, 53(2), Feb. 2007 Page(s):794 - 804 . IEEExplore version.
   
   

Selected Conference Papers (click on [Short description] for short descriptions)

Decentralized Control



24. [ISIT '11] Pulkit Grover and Anant Sahai, The “source-simplification” aspect of signaling. Accepted at IEEE International Symposium on Information Theory (ISIT) 2011.


23. [CDC '11 Sub. a] Pulkit Grover and Cedric Langbort, The role of common context in facilitating coordination. IEEE Conference on Decision and Control 2011, Submitted. [PDF]


22. [CDC '11 Sub. b] Abhishek Gupta, Pulkit Grover, Cedric Langbort and Tamer Basar, One-stage control over an adversarial channel with finite codewords. IEEE Conference on Decision and Control 2011, Submitted. [PDF]


21. [Allerton '10] Pulkit Grover and Anant Sahai, Implicit and Explicit Communication in Decentralized Control. 48th Annual Allerton Conference on Communication, Control, and Computing, Monticello, Illinois. [PDF] [Handout] [Slides]


20. [CDC '10] Pulkit Grover and Anant Sahai, Is Witsenhausen's counterexample a relevant toy? IEEE Conference on Decision and Control (CDC) 2010. [PDF] Winner of the best student paper award.


19. [ISIT '10] Pulkit Grover and Anant Sahai, Distributed signal cancelation inspired by Witsenhausen's counterexample. (Expanded version) IEE International Symposium on Information Theory (ISIT) 2010. [PDF containing full proofs] [Proceedings version]. Finalist for the best student paper award.


18. [ITW '10] Pulkit Grover, Aaron B. Wagner and Anant Sahai, Information Embedding Meets Distributed Control. Proceedings of the IEEE Information Theory Workshop 2010, Cairo, Egypt. [PDF] [MATLAB code]


17. [Allerton '09] Pulkit Grover, Se Yong Park and Anant Sahai, On the Generalized Witsenhausen Counterexample. Proceedings of the Forty-Seventh Annual Allerton Conference on Communication, Control, and Computing, Monticello, Illinois, 2009. [PDF]


16. [ConCom '09] Pulkit Grover, Anant Sahai and Se Yong Park, The finite-dimensional Witsenhausen counterexample. (Extended version) Proceedings of the 7th International Symposium on Modeling and Optimization in Mobile, Ad Hoc, and Wireless Networks (WiOpt), Workshop on Control over Communication Channels (ConCom) 2009. [Short description] [PDF] [Handout] [Slides][MATLAB code]
    Companion paper : Se Yong Park, Pulkit Grover and Anant Sahai, A constant factor approximately-optimal solution to the Witsenhausen counterexample . Proceedings of the 48th Conference on Decision and Control (CDC) 2009.
    
    An approximate solution to Witsenhausen's counterexample: we show that quantization based strategies can obtain within a factor of 8 of the optimal costs for the original (scalar) Witsenhausen counterexample for all values of the problem parameters. Further, lattice based strategies obtain within a constant factor of optimal for vector Witsenhausen counterexample of any length. These are first results that show approximate optimality of any scheme for this longstanding problem.
    The companion paper provides a different proof (based on same principles) for the constant factor optimality (for the scalar case), though the approximation factor itself is not as tight.
    
    
    
15. [CDC '08] Pulkit Grover and Anant Sahai, A vector version of Witsenhausen's counterexample : Towards convergence of control, communication and computation. Proceedings of the IEEE Conference on Decision and Control in Cancun, Mexico, 2008. [Short description] [PDF] [Handout] [Slides] [MATLAB code]
    
    This paper was the first step to obtaining an approximately optimal solution to the Witsenhausen counterexample. We derive upper and lower bounds on the costs for the vector extension to the counterexample. We show that the ratio of the upper and lower bound is no more than 2 for any choice of problem parameters for infinite vector length.
    We also connected the problem to computation of good control schemes. Our results suggest that there are fundamental tradeoffs between the costs of control, communication, and computation.



Green radios



14. [EUSIPCO '11] Pulkit Grover, Anant Sahai and Ji-Hoon Park Simple models for power optimization across transmission, equalization and decoding, 2011 European Signal Processing Conference.


13. [SiPS '11] Karthik Ganesan, Pulkit Grover, and Jan Rabaey The power cost of overdesigning codes, 2011 IEEE Workshop on Signal Processing Systems, Submitted.


12. [DAC '11] Karthik Ganesan and Pulkit Grover, Decoding power can increase significantly with increased wire-lengths and code performance: empirical results, Design Automation Conference (DAC) 2011, Work In Progress Session.


11. [CISS '11] Pulkit Grover and Anant Sahai, Fundamental bounds on the interconnect complexity of decoder implementations, Accepted at the Conference on Information Sciences and Systems (CISS) 2011.


10. [ISTC '10] Pulkit Grover, Kristen Ann Woyach, Hari Palaiyanur and Anant Sahai, An interference-aware perspective on decoding power. 6th International Symposium on turbo codes and iterative information processing (ISTC), to appear. [PDF]


9. [ISIT '10] Pulkit Grover, Hari Palaiyanur and Anant Sahai, Information-theoretic tradeoffs on throughput and chip power consumption for decoding error-correcting codes. IEEE International Symposium on Information Theory (ISIT) 2010. [PDF]


8. [ISIT '10] Pulkit Grover and Anant Sahai, Shannon meets Tesla: Wireless information and power transfer. IEEE International Symposium on Information Theory (ISIT) 2010. [PDF]


7. [ISIT '09] Pulkit Grover and Anant Sahai, Time-division multiplexing for Green Broadcasting. (extended version) Proceedings of the IEEE International Symposium on Information Theory (ISIT), 2009. [Short description] [PDF] [Handout] [Slides] [MATLAB code]
   
   At short distances, decoding power can be comparable to transmit power. In such cases, simple time-division multiplexing based schemes outperform transmit-power optimal superposition-based schemes if the decoding power is also taken into account. We also provide an improvement over the best known outer bound on the error exponents for the Gaussian broadcast channel.
   
   
   
6. [ISIT '08] Pulkit Grover and Anant Sahai, Green Codes: Energy-Efficient Short-Range Communication. Proceedings of the 2008 International Symposium on Information Theory in Toronto, 2008. [Short description] [PDF] [Slides]
   
   We consider the problem of decoding energy for short distance wireless communication problems in Verdu's capacity per-unit. We show that as the error probability goes to zero, the required total energy-per-bit increases to infinity, even if the rate is allowed to be arbitrary. Further, the optimal rate is non-zero, contrary to the prediction of classical theory. For minimizing total energy-per-bit, therefore, it might be prudent to communicate at a rate higher than desired.
   
   
   
5. [ITW '07] Pulkit Grover, Bounds on the Tradeoff between decoding complexity and rate for codes on graphs, Proceedings of the IEEE Information Theory Workshop (ITW) 2007, Lake Tahoe, CA, 2007. [PDF]



Everything else!



4. [Globecom '11] Kristen Woyach, Pulkit Grover and Anant Sahai, Near vs far field: interference aggregation in TV white spaces, IEEE Globecom 2011, Submitted. [PDF]
   
   
3. [DySPaN '07] Pulkit Grover and Anant Sahai, On the need for knowledge of the phase in exploiting known primary transmissions, Proceedings of the IEEE DySPAN 2007, Dublin, Ireland (The linked paper includes follow-up work that appeared in the Proceedings of IEEE International Symposium on Information Theory (ISIT) 2007). [PDF]
   
   
2. [ITW '04] Pulkit Grover and Ajit Kumar Chaturvedi, Upper Bounds on the Rate of LDPC Codes for Gilbert-Elliott Channels, Proceedings of the IEEE Information Theory Workshop (ITW) 2004, San Antonio, Texas, October 2004. [PDF]
   
   
1. [NCC '05] Pulkit Grover and Ajit Kumar Chaturvedi, Upper Bounds on the Rate of Randomly Constructed LDPC Codes for a Class of Markov Channels, Proceedings of the National Conference on Communications (NCC) 2005, IIT Kharagpur, Kharagpur, India, January 2005. [PDF]

Masters Thesis

Pulkit Grover. LDPC Codes: Bounds on the rate for FSMCs and some results on minimal stopping sets. July 2005, IIT Kanpur [PDF]