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# Alexander Stolyar

## Primary Research Area

- Operations Research

## Professor

201C Transportation Building

phone: (217) 300-5495

email: stolyar@illinois.edu

## For more information

## Education

- Ph.D., Mathematics, 1989, Institute of Control Sciences, USSR Academy of Science, Moscow, USSR.
- M.S., Applied Mathematics, 1982, Moscow College of Transportation Engineering, Moscow, USSR.

## Academic Positions

- Founder Professor, University of Illinois at Urbana-Champaign, ISE Department, 1/2017-present
- Timothy J. Wilmott Endowed Chair Professor, Lehigh University, ISE Department, 8/2014-1/2017
- Distinguished Member of Technical Staff, Bell Laboratories, Mathematical Sciences Research, 3/2006-8/2014
- Member of Technical Staff, Bell Laboratories, Mathematical Sciences Research, 8/1998-3/2006
- Senior Staff Engineer, Motorola, Wireless Networks Research, 5/1997-8/1998
- Senior Technical Staff Member, AT&T Labs-Research, Network Mathematics Research, 9/1996-4/1997
- Lead Engineer, Motorola, Wireless Networks Research, 6/1992-9/1996
- Research Scientist, Institute of Control Sciences, USSR Academy of Science, 2/1989-6/1991

## Research Interests

- Stochastic Modeling of Communication, Information and Service Systems: cloud data systems, communication networks, call/contact centers and other service systems; dynamic resource allocation, scheduling and congestion control, distributed algorithms, large scale systems
- Stochastic Processes and Queueing Networks: asymptotic methods, fluid and diffusion limits, stochastic stability, large deviations, dynamic control and optimization.

## Research Areas

- Operations Research

## Selected Articles in Journals

- S. Foss, A. L. Stolyar. Large-scale Join-Idle-Queue system with general service times. Journal of Applied Probability, 2017, Vol.54, No.4, to appear.
- A. L. Stolyar. Pull-based load distribution among heterogeneous parallel servers: the case of multiple routers. Queueing Systems, 2017, Vol.85, No.1-2, pp. 31-65. DOI 10.1007/s11134-016-9508-8
- A. L. Stolyar. Large-scale heterogeneous service systems with general packing constraints. Advances in Applied Probability, 2017, Vol.49, No.1, pp.61-83. DOI: https://doi.org/10.1017/apr.2016.79
- G. Pang, A. L. Stolyar. A service system with on-demand agent invitations. Queueing Systems, 2016, Vol. 82, No. 3, pp. 259-283. DOI 10.1007/s11134-015-9464-8
- A. L. Stolyar. Pull-based load distribution in large-scale heterogeneous service systems. Queueing Systems, 2015, Vol.80, No.4, pp.341-361. DOI 10.1007/s11134-015-9448-8
- A. L. Stolyar. Tightness of stationary distributions of a flexible-server system in the Halfin-Whitt asymptotic regime. Stochastic Systems, 2015, Vol. 5, No. 2, pp. 239-267. http://dx.doi.org/10.1214/14-SSY139
- A. L. Stolyar, Y. Zhong. Asymptotic optimality of a greedy randomized algorithm in a large-scale service system with general packing constraints. Queueing Systems, 2015, Vol.79, No.2, pp. 117-143. DOI 10.1007/s11134-014-9414-x
- A. L. Stolyar. Diffusion scale tightness of invariant distributions of a large-scale flexible service system. Advances in Applied Probability, 2015, Vol.47, No.1, pp. 251-269.
- Y. Guo, A. L. Stolyar, A. Walid. Shadow-routing based dynamic algorithms for Virtual Machine placement in a network cloud. IEEE Transactions on Cloud Computing. 2015, DOI 10.1109/TCC.2015.2464795
- A. L. Stolyar. An infinite server system with general packing constraints. Operations Research, 2013, Vol.61, No.5, pp.1200 - 1217.
- A. L. Stolyar, E.Yudovina. Tightness of invariant distributions of a large-scale flexible service system under a priority discipline. Stochastic Systems, 2012, Vol.2, No.2, pp.381-408.
- D. Gamarnik, A.L. Stolyar. Multiclass multiserver queueing system in the Halfin-Whitt heavy traffic regime. Asymptotics of the stationary distribution, Queueing Systems, 2012, Vol.71, pp.25-51. DOI 10.1007/s11134-012-9294-x
- A.L. Stolyar, E.Yudovina. Systems with large flexible server pools: Instability of "natural" load balancing, Annals of Applied Probability, 2013, Vol.23, No.5, pp.2099-2138. DOI 10.1214/12-AAP895
- A.L. Stolyar, T. Tezcan. Shadow routing based control of flexible multi-server pools in overload, Operations Research, 2011, Vol. 59, No.6, pp. 1427-1444.
- E. Athanasopoulou, L. Bui, T. Ji, R. Srikant, A.L. Stolyar. Backpressure-based Packet-by-Packet Adaptive Routing in Communication Networks. IEEE/ACM Trans. on Networking, 2013, Vol.21, No.1, pp.244-257.
- P.Gupta, A.L. Stolyar. Throughput Region of Random Access Networks of General Topology, IEEE Trans. on Information Theory, 2012, Vol.58, May 2012, No. 5, pp. 3016-3022.
- A.L. Stolyar. Large number of queues in tandem: Scaling properties under back-pressure algorithm, Queueing Systems, 2011, Vol. 67, pp. 111-126.
- A.L. Stolyar, T. Tezcan. Control of systems with flexible multi-server pools: A shadow routing approach, Queueing Systems, 2010, Vol. 66, pp. 1-51.
- L. Bui, R. Srikant, A.L. Stolyar. A Novel Architecture for Delay Reduction in Back-pressure Scheduling Algorithm, IEEE/ACM Trans. on Networking, 2011, Vol.19, No.6, pp. 1597-1609.
- J. Liu, A.L. Stolyar, M. Chiang, H. V. Poor. Queue Back-Pressure Random Access in Multi-Hop Wireless Networks: Optimality and Stability, IEEE Tran. Inf. Theory, 2009, Vol.55, No.9, pp. 4087-4098.
- A.L. Stolyar. Large Deviations of Queues Sharing a Randomly Time-varying Server, Queueing Systems, 2008, Vol. 59, pp. 1-35.
- A.L. Stolyar. Dynamic Distributed Scheduling in Random Access Networks, Journal of Applied Probability, 2008, Vol. 45, No.2, pp. 297-313.
- L. Bui, R. Srikant, A.L. Stolyar. Optimal Resource Allocation for Multicast Flows in Multihop Wireless Networks, Philosophical Transactions of the Royal Society A, 2008, Vol. 366, pp.2059-2074.
- A.L. Stolyar. Greedy Primal-Dual Algorithm for Dynamic Resource Allocation in Complex Networks, Queueing Systems, 2006, Vol. 54, No.3, pp.203-220.
- A.L. Stolyar. Maximizing Queueing Network Utility subject to Stability: Greedy Primal-Dual Algorithm, Queueing Systems, 2005, Vol. 50, No.4, pp.401-457.
- A.L. Puha, A.L. Stolyar, R.J. Williams. The Fluid Limit of an Overloaded Processor Sharing Queue, Mathematics of Operations Research, 2006, Vol.31, No.2, pp.316-350.
- A.L. Stolyar. Optimal Routing in Output-Queued Flexible Server Systems, Probability in the Engineering and Informational Sciences, 2005, Vol.19, pp.141-189.
- A.L. Stolyar. On the Asymptotic Optimality of the Gradient Scheduling Algorithm for Multi-User Throughput Allocation, Operations Research, 2005, Vol.53, No.1, pp. 12-25.
- M. Mandjes, I. Saniee, A. L. Stolyar. Load Chracterization and Anomaly Detection for Voice Over IP Traffic. IEEE Transactions on Neural Networks, Vol.16, September 2005, No. 5, pp. 1019-1026.
- A. Mandelbaum, A.L. Stolyar. Scheduling Flexible Servers with Convex Delay Costs: Heavy-Traffic Optimality of the Generalized c-mu-rule, Operations Research, 2004, Vol.52, No.6, pp. 836-855.
- S. Shakkottai, R. Srikant, A.L. Stolyar. Pathwise Optimality of the Exponential Scheduling Rule for Wireless Channels, Advances in Applied Probability, 2004, Vol. 36, No. 4, pp. 1021-1045.
- A.L. Stolyar. MaxWeight Scheduling in a Generalized Switch: State Space Collapse and Workload Minimization in Heavy Traffic, Annals of Applied Probability, 2004, Vol.14, No.1, pp.1-53.
- A.L. Stolyar. Control of End-to-End Delay Tails in a Multiclass Network: LWDF Discipline Optimality, Annals of Applied Probability, 2003, Vol.13, No.3, pp.1151-1206.
- K. Kumaran, M. Mandjes, A.L. Stolyar. Convexity Properties of Loss and Overflow Functions, Operations Research Letters, 2003, Vol. 31, No.2, pp. 95-100.
- S. Shakkottai and A. L. Stolyar. Scheduling for Multiple Flows Sharing a Time-Varying Channel: The Exponential Rule, Analytic Methods in Applied Probability. In Memory of Fridrih Karpelevich. Yu. M. Suhov, Editor. American Mathematical Society Translations, Series 2, Volume 207, pp. 185-202. American Mathematical Society, Providence, RI, 2002.
- A.N. Rybko, A.L. Stolyar and Yu.M. Suhov. Stability of Global LIFO Networks, Analytic Methods in Applied Probability. In Memory of Fridrih Karpelevich. Yu. M. Suhov, Editor. American Mathematical Society Translations, Series 2, Volume 207, pp. 177-184. American Mathematical Society, Providence, RI, 2002.
- M. Andrews, K. Kumaran, K. Ramanan, A. L. Stolyar, R. Vijayakumar, P. Whiting. Providing Quality of Service over a Shared Wireless Link, IEEE Communications Magazine, 2001, Vol.39, No.2, pp.150-154.
- M. Andrews, K. Kumaran, K. Ramanan, A.L. Stolyar, R. Vijayakumar, P. Whiting. Scheduling in a Queueing System with Asynchronously Varying Service Rates, Probability in the Engineering and Informational Sciences, 2004, Vol.18, pp. 191-217.
- A.L. Stolyar and K. Ramanan. Largest Weighted Delay First Scheduling: Large Deviations and Optimality, Annals of Applied Probability, 2001, Vol.11, No.1, pp. 1-48.
- E.G. Coffman, Jr. and A.L. Stolyar. Bandwidth Packing, Algorithmica, 2001, Vol.29, pp. 70-88.
- E.G. Coffman, Jr., E.N.Gilbert, A.G. Greenberg, F.T.Leighton, P. Robert, A.L.Stolyar. Queues served by a rotating ring, Stochastic Models, vol. 11, no. 3, p. 371-394, 1995.
- A.L.Stolyar. On the stability of multiclass queueing networks: A relaxed sufficient condition via limiting fluid processes, Markov Processes and Related Fields, 1995, pp. 491-512.
- E.G. Coffman, Jr. and A.L.Stolyar. Continuous polling on graphs, Probability in the Engineering and Informational Sciences, vol. 7, pp. 209-226, 1993.
- A.N. Rybko and A.L.Stolyar. Ergodicity of stochastic processes describing the operation of open queueing networks , Problems of Information Transmission, vol. 28, 1992, pp. 199-220. (Translated from Problemy Peredachi Informatsii, vol. 28, no. 3, pp. 3-26, 1992.)
- A.L.Stolyar. Comparative throughput analysis of queueing networks with exponential and deterministic service times in nodes, Problems of Information Transmission, vol.27, pp. 99-107, 1991. (Translated from Problemy Peredachi Informatsii, vol. 27, no. 2, pp. 15-24, 1991.)
- A.L.Stolyar. Asymptotic behavior of the stationary distribution for a closed queueing system, Problems of Information Transmission, vol.25, pp. 321-331, 1989. (Translated from Problemy Peredachi Informatsii, vol. 25, no. 4, pp. 80-91, 1989.)
- L.B. Boguslavsky, V.S.Podlazov, A.L.Stolyar. Analysis of methods for priority access for local networks with waiting time constraints, Automation and Remote Control, vol.50, pp. 1449-1457, 1989. (Translated from Avtomatika i Telemekhanika, no. 10, pp. 175-186, 1989.)
- A.L.Stolyar. On the optimal load control of a queueing network, Automation and Remote Control, vol.50, 1989. (Translated from Avtomatika i Telemekhanika, no. 5, pp.184-187, 1989.)

## Articles in Conference Proceedings

- S. Foss, A. L. Stolyar. Join-Idle-Queue system with general service times: Large-scale limit of stationary distributions. The Workshop on MAthematical performance Modeling and Analysis (MAMA), 2017.
- L. Nguyen, A. L. Stolyar. A service system with randomly behaving on-demand agents. SIGMETRICS-2016.
- A. L. Stolyar. Large-scale service systems with packing constraints and heterogeneous servers. The Workshop on MAthematical performance Modeling and Analysis (MAMA), 2016.
- R. Singh, A. L. Stolyar. MaxWeight Scheduling: Smoothness of the Service Process, INFOCOM-2016.
- R. Singh, A. L. Stolyar. MaxWeight Scheduling: Asymptotic Behavior of Unscaled Queue-Differentials in Heavy Traffic. SIGMETRICS-2015.
- Y. Guo, A. L. Stolyar, A.Walid. Online Algorithms for Joint Application-VM-Physical-Machine Assignment in a Cloud. SIGMETRICS-2014.
- A. L. Stolyar, Y. Zhong. An infinite server system with general packing constraints: Asymptotic optimality of a greedy randomized algorithm. Proceedings of the 51st Annual Allerton Conference, 2013.
- A. L. Stolyar, Y. Zhong. A large-scale service system with packing constraints: Minimizing the number of occupied servers. SIGMETRICS-2013.
- Y. Guo, A. L. Stolyar, A.Walid. Shadow-routing based dynamic algorithms for Virtual Machine placement in a network cloud. INFOCOM-2013, pp. 620 - 628. DOI 10.1109/INFCOM.2013.6566847
- A. L. Stolyar. An infinite server system with customer-to-server packing constraints. Proceedings of the 50th Annual Allerton Conference, 2012.
- A. L. Stolyar, E.Yudovina. Instability of natural load balancing in large-scale flexible-server systems. Proceedings of the 49th Annual Allerton Conference, 2011.
- B. Rengarajan, A. L. Stolyar, H. Viswanathan. Self-organizing Dynamic Fractional Frequency Reuse on the Uplink of OFDMA Systems. Proceeding of CISS'2010, Princeton, March 2010.
- A. L. Stolyar, H. Viswanathan. Self-organizing Dynamic Fractional Frequency Reuse for Best-Effort Traffic Through Distributed Inter-cell Coordination. Proceeding of INFOCOM'2009, Rio de Janeiro, April 2009.
- L. Bui, R. Srikant, A. L. Stolyar. Novel Architectures and Algorithms for Delay Reduction in Back-pressure Scheduling and Routing. Proceeding of INFOCOM'2009 Mini-conference, Rio de Janeiro, April 2009.
- J. Liu, A. L. Stolyar. Distributed Queue-Length based Algorithms for Optimal End-to-End Throughput Allocation and Stability in Multihop Random Access Networks. Proceedings of the 45th Annual Allerton Conference, 2007.
- L. Bui, R. Srikant, A. L. Stolyar. Optimal Resource Allocation for Multicast Flows in Multihop Wireless Networks. CDC-2007.
- U. Akyol, M. Andrews, P. Gupta, J. Hobby, I. Saniee, A. L. Stolyar. Joint Scheduling and Congestion Control in Mobile Ad-Hoc Networks. Proceeding of INFOCOM'2008, Phoenix, April 14-18, 2008.
- A. L. Stolyar, H. Viswanathan. Self-organizing Dynamic Fractional Frequency Reuse in OFDMA Systems. Proceeding of INFOCOM'2008, Phoenix, April 14-18, 2008.
- M. Andrews, K. Jung, A. L. Stolyar. Stability of the Max-Weight Routing and Scheduling Protocol in Dynamic Networks and at Critical Loads. STOC'07, San Diego, CA, June 11-13, 2007.
- A. L. Stolyar. Large Deviations of Queues under QoS Scheduling Algorithms. Proceedings of the 44st Annual Allerton Conference, 2006.
- P. Gupta, A. L. Stolyar. Optimal Throughput Allocation in General Random-Access Networks. Proceeding of CISS'2006, Princeton, March 2006.
- M. Mandjes, I. Saniee, A. L. Stolyar. Load Chracterization and Anomaly Detection for Voice Over IP Traffic. SIGMETRICS/Performance 2001, pp. 326-327.
- P. Gupta, Y. Sankarasubramaniam, A. L. Stolyar. Random-Access Scheduling with Service Differentiation in Wireless Networks. Proceeding of INFOCOM'2005, Miami, March 13-17, 2005.
- P. Gupta, Y. Sankarasubramaniam, A. L. Stolyar. Distributed Scheduling in Wireless Data Networks with Service Differentiation. ISIT'2004, Chicago, July 2004.
- M. Andrews, L. Qian, A. L. Stolyar. Optimal Utility Based Multi-User Throughput Allocation subject to Throughput Constraints. Proceeding of INFOCOM'2005, Miami, March 13-17, 2005.
- A. L. Stolyar. Optimal Control of Output-Queued Flexible Server Systems in Heavy Traffic. Proceedings of the 41st Annual Allerton Conference, 2003.
- A. Mandelbaum, A. L. Stolyar. Gcmu Scheduling of Flexible Servers: Asymptotic Optimality in Heavy Traffic. Proceedings of the 40th Annual Allerton Conference, 2002.
- S. Shakkottai, R. Srikant, A. L. Stolyar. Pathwise Optimality of the Exponential Scheduling Rule for Wireless Channels. Proceedings of ISIT, Lausanne, Switzerland, July 2002.
- A.L. Stolyar. Scheduling of a Generalized Switch: Heavy Traffic Regime. Telecommunications Network Design and Management. G.Anandalingam and S.Raghavan, Editors, pp. 143-166, Kluwer, 2002.
- A. Mandelbaum, W.A. Massey, M.I. Reiman, A. Stolyar, B.Rider. Queue Length and Waiting Times for Multiserver Queues with Abandonment and Retrials. Telecommunications Systems, 2002, Vol.21, Nos.2-4, pp. 149-171.
- S. Shakkottai, A. L. Stolyar. Scheduling Algorithms for a Mixture of Real-Time and Non-Real-Time Data in HDR. Proceedings of the 17th International Teletraffic Congress - ITC-17, Salvador da Bahia, Brazil, 24-28 September, 2001, pp. 793-804.
- E. G. Coffman, Jr., Ph. Robert, A. L. Stolyar. The interval packing process of linear networks. SIGMETRICS Performance Evaluation Review, 1999, Vol. 27(3), pp. 3-4.
- E.G. Coffman, Jr., A.L. Stolyar. Fluid Limits, Bin Packing, and Stochastic Analysis of Algorithms. Proc. of the Tenth Annual ACM-SIAM Symposium on Discrete Algorithms (SODA-1999), pp. 877-878, New York, 1999. ACM Press.
- A. Mandelbaum, W.A. Massey, M.I. Reiman, A.L. Stolyar. Waiting Time Asymptotics for Time Varying Multiserver Queues with Abandonment and Retrials. Proceedings of the 37th Annual Allerton Conference, 1999, pp. 1095-1104.
- A.L. Stolyar and K.K. Ramakrishnan, The Stability of a Flow Merge Point with Non-Interleaving Cut-Through Scheduling Disciplines. INFOCOM'99, New York, March 23-25, 1999, pp. 1231-1238.
- R. Pazhyannur, A. Stolyar and P. Fleming. Fluid Analysis of CDMA Cellular Systems. Proceedings of the 15th International Teletraffic Congress - ITC-15, Washington, DC, 22-27 June, 1997, pp. 13-22.
- A.G. Greenberg, S. Shenker, A.L. Stolyar. Asynchronous Updates in Large Parallel Systems. Proceedings of ACM Sigmetrics'96, 1996, pp. 91-103.
- A.L. Stolyar. On the stability of multiclass queueing networks. Second International Conference on Telecommunication Systems, Modeling and Analysis, Nashville, TN, March 23-26, 1994, pp. 23-36.
- P.J. Fleming, A. Stolyar and B. Simon. Heavy traffic limit for a mobile system model. Second International Conference on Telecommunication Systems, Modeling and Analysis, Nashville, TN, March 23-26, 1994, pp. 317-327.
- L.B. Boguslavsky and A.L. Stolyar. Performance analysis of data link and communication device control procedures in distributed micro/mini computer systems. Lecture Notes in Control and Information Science, System Modeling and Optimization, vol. 84, pp. 91-101, Springer-Verlag, Berlin, 1986.

## Pending Articles

- S. Shneer, A. L. Stolyar. Stability conditions for a discrete-time decentralised medium access algorithm. 2017.
- L. Nguyen, A. L. Stolyar. A queueing system with on-demand servers: local stability of fluid limits. 2016.
- Y. Guo, A. L. Stolyar, A. Walid. Online VM Auto-Scaling Algorithms for Application Hosting in a Cloud. 2016.
- M. Nazari, A. L. Stolyar. Reward Maximization in General Dynamic Matching Systems. 2016.
- A. L. Stolyar, Y. Zhong. A service system with packing constraints: Greedy randomized algorithm achieving sublinear in scale optimality gap. 2015.

## Patents

- US Patent App. 20150358402. Efficient and scalable pull-based load distribution.
- US Patent App. 20140189707. Virtual machine placement in a cloud-based network.
- US Patent App. 20140105018. Method and apparatus of group credit control for wireless networks.
- US Patent App. 20130311662. Cloud resource allocation system and method.
- US Patent App. 20120005370. Methods of routing for networks with feedback.
- US Patent App. 20110077016. Apparatus and method to facilitate wireless uplink resource allocation.
- US Patent App. 20100309878. Mobility access gateway.
- US Patent App. 20100266116. Pacing in knowledge worker engagement.
- US Patent App. 20040266451. Method and apparatus for improving scheduler performance in wireless packet data systems.
- US Patent 9,131,371. Method and apparatus for managing a random access communication system.
- US Patent 8,730,923. Method for controlling resource allocation in a wireless communication system.
- US Patent 8,516,085. Systems and methods for allocating resources by a network device.
- US Patents 8,295,231 and 8,411,624. Method of dynamic resource allocations in wireless systems.
- US Patent 8,027,327. Distributed scheduling in wireless networks with service differentiation.
- US Patent 7,633,865. Network operations control in packet data networks.
- US Patent 7,526,291. Method and apparatus for managing supplemental channel data rates.
- US Patent 7,298,719. Method for scheduling wireless downlink transmissions subject to rate constraints.
- US Patent 7,174,180. Methods and apparatus for transmission scheduling in wireless networks.
- US Patent 7,065,046. Scalable weight-based terabit switch scheduling methods.
- US Patent 7,054,267. Method and apparatus for scheduling traffic to meet quality of service requirements in a communication network.
- US Patent 6,590,890. Method of packet scheduling, with improved delay performance, for wireless networks.
- US Patent 5,796,722. Method and apparatus for dynamic load balancing using handoff.
- US Patent 5,666,356. Method and apparatus for controlling calls in a code division multiple access system.

## Journal Editorships

- Operations Research (2006-2011)
- Advances in Applied Probability / Journal of Applied Probability (2008-2015)
- Queueing Systems - Theory and Applications (2008 - present)

## Honors

- The INFORMS Applied Probability Society Best Publication Award (2004)
- ACM Sigmetrics'96 Conference Best Simulation Paper (1996)

## Courses Taught

- IE 370 - Stochastic Processes & Applic
- IE 598 - Queuing Systems
- IE 598 - Service Engineering