Stochastic Control and Optimization of Networks

Integrated Data Center Networking:

My earlier work on switch and network scheduling:

T. Javidi, R Magill, and T. Hrabik. A High Throughput Scheduling Algorithm for a Buffered Crossbar Switch Fabric. In Proceedings of IEEE International Conference on Communications, vol. 5, pp. 1586-1591, 2001

M. Naghshvar, H. Zhuang, and T. Javidi. A General Class of Throughput Optimal Routing Policies in Multi-hop Wireless Networks. IEEE Transactions on Information Theory, Volume 58 , Issue 4, pp 2175 - 2193, 2012

became the basis of my interactions with the Center of Integrated Access Networks (CIAN) whose research thrusts includes the integration of the optical switch technology in intra-data center networking. While optical communication technology can provide extremely fast and efficient link for data transmission, the adoption of optical technology in large scale networking is impeded by the general inefficiency of writing and buffering in optical domain. To address the issue, we conceptualized the overall non-blocking non-buffering end-end network as a generalized switch (with less than full bisection bandwidth).

We have showed the power of this network-wide generalization of switching by showing that the problem of end-end scheduling in data-center networking can be adapted to the switching cost and loss of duty-cycle. We developed a scheduling algorithm that extended all previous work on switch scheduling to the case of flow management for optical switching:

C. Wang, T. Javidi, G. Porter. End-to-End Scheduling for All-Optical Data Centers. in Proceedings of IEEE International Conference on Computer Communication (INFOCOM), April 2015

Subsequently, along with a postdoc of mine, Tugcan Aktas, we showed that the proposed architecture can easily be supported as a hybrid wireless/optical networking solution:

T. Javidi, C. Wang, T. Aktash. A Novel Data Center Network Architecture with Zero in-Network Queuing. Proceedings of the 2015 IEEE International Symposium on Modeling and Optimization in Mobile, Ad Hoc and Wireless Networks (WiOpt), May 2015 [invited]

T. Aktas, C. Wang, T. Javidi. WiCOD: Wireless Control Plane Serving an all-Optical Data Center. Proceedings of the 2015 IEEE International Symposium on Modeling and Optimization in Mobile, Ad Hoc and Wireless Networks (WiOpt), May 2015

Cognitive Networking:

As the demand for mobile/wireless services as well as the complexity and the diversity of networks and devices continue to grow, there is a need for developing affordable and scalable means for effectively utilizing the available resources to deliver the complex applications and services of the future. It this context, cognitive networking has come to the forefront of wireless networking research. While, cognitive radio technology was first envisioned around the notion of spectrum agility, with the ever increasing popularity of the “smart” devices -not only equipped with multiple wireless interface cards but also with significant storage and computational capabilities- the once dream-like notions of sensing and network computations, adaptability, and learning are now generalized across the network and protocol stack. In particular, we have looked at two aspects of cognitive networking. The first set of work attempts to addresses the exploitation versus exploration tradeoff in context of opportunistic sensing/access, while the second class of our publications deal with the problem of network/topology information in wireless multihop routing.

Javidi, T.; Krishnamachari, B.; Qing Zhao; Mingyan Liu; , "Optimality of Myopic Sensing in Multi-Channel Opportunistic Access. IEEE International Conference on Communications, 2008. ICC '08, 19-23 May 2008 [here]

Ahmad, S.; Mingyan Liu; Javidi, T.; Qing Zhao; Krishnamachari, B.; , "Optimality of Myopic Sensing in Multichannel Opportunistic Access," Information Theory, IEEE Transactions on , vol.55, no.9, pp.4040-4050, Sept. 2009 [here]

A. Bhorkar, M. Naghshvar, T. Javidi and B. Rao, An Adaptive Opportunistic Routing Scheme for Wireless Ad-hoc

Networks. in IEEE Transactions on Networking, August 2011 [here]

A. Bhorkar. Javidi. No Regret Routing for ad-hoc wireless networks. Conference Record of the Forty Fourth Asilomar Conference on Signals, Systems and Computers (ASILOMAR), vol., no., pp.676-680, 7-10 Nov. 2010 [here]

P. Mansourifard, T. Javidi, and B. Krishnamachari. Optimality of Myopic Policy for a Class of Monotone Affine Restless Multi-Armed Bandits. in Proceedings of IEEE Conference on Decision and Control (CDC), December, 2012

A third class of problems arise in the context of distributed learning and estimation. Here with my collaborator, Anand Sarwate, we have combined techniques from consensus literature with stochastic approximation and analysis to arrive at learning distributions across the network:

A.D. Sarwate, T. Javidi, Distributed Learning of Distributions via Social Sampling, Accepted for publication in IEEE Transactions on Automatic Control. [Arxiv]

Optimal Routing in Wireless Mesh Networks:

I have also used closely related techniques in stochastic optimization and approximation to address the problem of routing in ad hoc and mesh wireless networks. As a part of my thesis work, I investigated the sensitivity of opportunistic routing to errors in the underlying Bayesian model. Recently, with my graduate students at UCSD, we have extended this work to multi-packet scenarios in which reinforcement learning techniques are used to achieve the optimal performance in the absence of information about the underlying (stochastic) model of the network. Furthermore, to address the issue of congestion diversity we have combined ideas from opportunistic routing and back-pressure to arrive at throughput optimal policies with good delay performance.

T. Javidi and D. Teneketzis. Sensitivity Analysis for Optimal Routing in Wireless Ad Hoc Networks in Presence of Error in Channel Quality Estimation. IEEE Transactions on Automatic Control, August 2004 [here]

A. Bhorkar, M. Naghshvar, T. Javidi and B. Rao, An Adaptive Opportunistic Routing Scheme for Wireless Ad-hoc

Networks. in IEEE Transactions on Networking, August 2011 [here]

M. Naghshvar, H. Zhuang, and T. Javidi. A General Class of Throughput Optimal Routing Policies in Multi-hop Wireless Networks, accepted for publication in IEEE Transactions on Information Theory, 2011 [here]

P. Gupta and T. Javidi, Towards Throughput and Delay Optimal Routing for Wireless Ad-Hoc Networks. In

Proceedings of Asilomar Conference on Signals, Systems, and Computers, November 2007 [here]

M. Naghshvar and T. Javidi, Opportunistic Routing with Congestion Diversity in Wireless Multi-hop Networks.

INFOCOM, 2010 Proceedings IEEE , vol., no., pp.1-5, 14-19 March 2010 [here]

Recently, I have gotten interested in the practical implementation of these solutions in 802.11 mesh networks. In particular, we have set up a testbed in Calit2 building consisting of 12 or so wifi nodes equipped with Atheros cards to test the ideas above on, and evaluate the practicality of our theoretical ideas.

A. Bhorkar, T. Javidi, and A. Snoeren. Achieving congestion diversity in wireless ad-hoc networks. Proceedings IEEE INFOCOM, vol., no., pp.521-525, 10-15 April 2011 [here]