Research

My research interests lie broadly in the area of wireless networks, including wireless medium access control (MAC), quality of service (QoS) and scalability issues. Part of my thesis research has focused on network architecture and medium access control for the multiGigabit 60 GHz indoor and outdoor wireless networks.

Labs: Wireless Communication and Sensornets Lab and the MOMENT Lab.

Projects

• Medium Access Control for 60 GHz Outdoor Mesh Networks
  This project investigates an architecture for multi-Gigabit outdoor mesh networks operating in the unlicensed 60 GHz millimeter (mm) wave band. In order to overcome the higher path loss at mm wave carrier frequencies, the use of narrow antenna beams is essential to attain the required link ranges (on the order of 100 meters) with the transmit powers possible with low-cost transceiver implementations. The highly directional links vastly reduce interference, but also result in deafness that makes medium access control (MAC) based on carrier sensing infeasible. We study the extent to which we can reduce, or even dispense with, interference management, by exploiting the reduction in interference due to the narrow beamwidths and the oxygen absorption characteristic of the 60 GHz band. We have designed a distributed MAC protocol that exploits the pseudo-wired nature of the 60 GHz links and attains high medium utilization by employing memory and learning for implicit coordination about nodes.
  
  
  • Sumit Singh, Raghuraman Mudumbai and Upamanyu Madhow, "Interference analysis for highly directional 60 GHz mesh networks: the case for rethinking medium access control", IEEE/ACM Trans. Networking, Vol. 19, Issue 5, Pages 1513-1527, Oct. 2011. (pdf)
  • Sumit Singh, Raghuraman Mudumbai and Upamanyu Madhow, "Distributed Coordination with Deaf Neighbors: Efficient Medium Access for 60 GHz Mesh Networks", in Proc. IEEE INFOCOM 2010, San Diego, CA, Mar. 2010. (pdf)
  • Raghuraman Mudumbai, Sumit Singh and Upamanyu Madhow, "Medium access control for 60 GHz outdoor mesh networks with highly directional links", in Proc. IEEE INFOCOM 2009, Mini Conference, Rio de Janeiro, Brazil, Apr. 2009.(pdf)


• Millimeter wave WPAN: Cross-layer modeling and multihop architecture
  The objective of this project is to develop a cross-layer modeling methodology and design a directional transmission-based multihop WPAN architecture for efficient utilization of the unlicensed spectrum in the 60 GHz band. This architecture takes into account the unique physical characteristics of the millimeter wave communication links, such as larger propagation losses and reduced diffraction around obstacles. We constrain every link to be directional for improved power efficiency (due to directivity gains) and simplicity of implementation (due to reduced delay spread). Thus, line of sight obstruction between the transmitter and receiver can result in link outage. We have developed a diffraction-based model to determine link losses as a function of stationary and moving obstacles in a given indoor setting, and have defined a directional MAC protocol that employs the multihop relay architecture to effectively maintain network connectivity.
  
  
  • Sumit Singh, Federico Ziliotto, Upamanyu Madhow, Elizabeth M. Belding and Mark J. W. Rodwell, "Blockage and Directivity in 60 GHz Wireless Personal Area Networks: From Cross-Layer Model to Multihop MAC Design", IEEE JSAC, Special Issue on Realizing Gbps Wireless Personal Area Networks, 2009.(pdf)
  • Sumit Singh, Federico Ziliotto, Upamanyu Madhow, Elizabeth M. Belding and Mark Rodwell, "Millimeter Wave WPAN: Cross-Layer Design and Multihop Architecture", in Proc. IEEE INFOCOM 2007, Minisymposium, Anchorage, AL, May 2007.(pdf)


• Resource allocation in multihop wireless networks
  We develop a resource allocation framework that opens up a rich design space for sharing transport capacity of multihop wireless networks among competing flows. We propose mixed bias strategies that blend strongly biased allocations with fairer allocation strategies so as to achieve a desired tradeoff between throughputs achieved by flows and their resource usage (i.e., flow throughput profiles), while ensuring efficient network utilization. We show that our resource sharing mechanisms can be implemented via decentralized protocols. The design space of such strategies can be quickly explored via a simple analytical model.


• Sumit Singh, Upamanyu Madhow and Elizabeth M. Belding, "Shaping Throughput Profiles in Multihop Wireless Networks: A Resource Biasing Approach", IEEE Trans. Mobile Computing, Volume 11, Issue 3, Pages 367-376, March 2012. (pdf)
• Sumit Singh, Upamanyu Madhow, Elizabeth M. Belding, "Beyond Proportional Fairness: A Resource Biasing Approach for Shaping Throughput Profiles in Multihop Wireless Networks", in Proc. IEEE INFOCOM 2008, Mini-Conference, Phoenix, AZ, Apr. 2008.(pdf)


• Sticky CSMA/CA: Implicit synchronization and real-time QoS over mesh networks
  Sticky CSMA/CA is a distributed MAC framework to support a mix of real-time and delay-insensitive traffic over mesh networks. It provides TDM-like QoS support without explicitly requiring network-wide synchronization. The basic idea is to exploit natural or artificially imposed application layer regularities in the design of medium access control such that packet transmissions from contending nodes become predictable, thereby facilitating substantial reduction in the medium contention overhead and packet collisions. Our performance evaluation over voice/data networks shows large gains over conventional CSMA/CA MAC protocols (IEEE 802.11b/e).
  
  
  • Sumit Singh, Prashanth Acharya, Upamanyu Madhow and Elizabeth M. Belding, "Sticky CSMA/CA: Implicit Synchronization and Real-time QoS in Mesh Networks", Ad Hoc Networks, Volume 5, Issue 6, (1) Wireless Mesh Networks; (2) Wireless Sensor Networks, August 2007, Pages 744-768. (pdf)
  • Sumit Singh, Prashanth Acharya, Upamanyu Madhow and Elizabeth M. Belding, "Sticky CSMA/CA: Implicit Synchronization and Real-time QoS in Mesh Networks", Poster presented at ICB Army-Industry Collaboration Conference, UCSB, Apr. 2006.(pdf)


• MAC framework for opportunistic use of TV spectrum
  MAC layer design for prediction-based opportunistic utilization of the broadcast TV spectrum by unlicensed secondary users such that interference to primary users of the spectrum is avoided.
  
  
  • Prashanth Acharya, Sumit Singh and Heather Zheng, "Reliable Open Spectrum Communications Through Proactive Spectrum Access", First International Workshop on Technology and Policy for Accessing Spectrum (TAPAS 2006), Boston, MA, Aug 2006.(pdf)