Research Projects

My research interests are broadly on experimental wireless networking and mobile computing, with a focus on high performance protocol design and implementation, testbed prototyping, network measurements, and performance evaluation. My research spans multiple layers of the networking stack (MAC, routing, and transport layer), and multiple types of wireless networks (mesh networks, mobile ad hoc networks, sensor networks, and more recently, broadband access networks, e.g., 3G cellular and WiFi networks).

Bandwidth estimation in wireless broadband access networks

We conducted the first study of the feasibility of fast probe-based bandwidth estimation in wireless broadband access networks ``in the wild'', i.e., in deployed operational networks. We identified the challenges associated with bandwidth measurements in operational networks in contrast to in controlled lab environments. We studied the applicability of a state-of-the-art probe-based tool for 802.11 WLANs on a commercial 1x EVDO network. In addition, we evaluated the accuracy of the tool in WLAN environments, e.g., lab, home, and hotspot. Our results show that bandwidth estimation using a probe-based tool can be challenging in certain WLAN environments, and practically infeasible in EVDO cellular networks, due to the short-scale dynamics in this type of networks.

  1. On the Feasibility of Fast Bandwidth Estimation in Wireless Access Networks.
    Dimitrios Koutsonikolas, Y. Charlie Hu.
    In ACM Wireless Networks, Vol. 17(6), pp. 1561–1580, July 2011.


  2. On the Feasibility of Bandwidth Estimation in 1x EVDO Networks.
    Dimitrios Koutsonikolas, Y. Charlie Hu.
    In Proceedings of the ACM Mobicom International Workshop on Mobile Internet Through Cellular Networks (MICNET 2009), Beijing, China, September 21, 2009.

Mesh@Purdue [MAP]

I was actively involved in the deployment of MAP (Mesh@Purdue), an experimental 802.11a/b/g Wireless Mesh Network testbed at Purdue University. MAP currently consists of 32 dual radio mesh nodes deployed in four academic buildings (MSEE, EE, PHYSICS and ME). I have been actively maintaining MAP since December 2007. Most of the projects listed below involve prototyping and experimentation on MAP testbed.

"Exotic" routing protocol design, implementation, and evaluation for Wireless Mesh Networks

We studied the use of recently proposed "exotic" (network coding, opportunistic routing) optimization techniques for improving throughput of Wireless Mesh Networks. We first reviewed the current diverse set of evaluation methodologies for "exotic" high-throughput routing protocols and proposed guidelines for a meaningful and fair evaluation. We conducted an empirical study of performance benefits of inter-flow network coding, and showed its limitations in practical scenarios. We than proposed novel ways of exploiting intra-flow network coding for improving performance of both multicast and unicast routing in wireless mesh networks. For multicast, we proposed Pacifier, described below. For unicast, we designed CCACK, a novel network coding-based opportunistic routing protocol exploiting a simple but efficient coded feedback scheme, which allows routers to decide how many coded packets to forward, online, in a way oblivious to link loss rates, and with practically zero overhead, in contrast to existing state-of-the-art protocols which rely on offline, loss rate-based heuristics.

  1. Pacifier: High-Throughput, Reliable Multicast without “Crying Babies” in Wireless Mesh Networks.
    Dimitrios Koutsonikolas, Y. Charlie Hu, and Chih-Chun Wang.
    In IEEE/ACM Transactions on Networking (ToN), Vol. 20(5), pp. 1375-1388, October 2012.

  2. FEC-Based AP Downlink Transmission Schemes For Multiple Flows: Combining the Reliability and Throughput Enhancement of Intra- and Inter-flow Coding.
    Chih-Chun Wang, Dimitrios Koutsonikolas, Y. Charlie Hu, and Ness B. Shroff.
    In Proceedings of the 29th International Symposium on Computer Performance, Modeling, Measurements and Evaluation (IFIP PERFORMANCE 2011), 18-20 October, 2011, Amsterdam, Netherlands. (acceptance rate 20%)
  3. Efficient Network Coding Based Opportunistic Routing Through Cumulative Coded Acknowledgments.
    Dimitrios Koutsonikolas, Chih-Chun Wang, and Y. Charlie Hu.
    In IEEE/ACM Transactions on Networking (ToN), Vol. 19(5), pp. 1368 - 1381, October 2011.
  4. CCACK: Efficient Network Coding Based Opportunistic Routing Through Cumulative Coded Acknowledgments.
    Dimitrios Koutsonikolas, Chih-Chun Wang, and Y. Charlie Hu.
    In Proceedings of IEEE INFOCOM 2010, San Diego, CA, March 15-19, 2010. (acceptance rate 17.5%)
  5. Designing Coded Feedback for Efficient Network Coding Based Opportunistic Routing (abstract). (1st place in ACM Student Research Competition)
    Dimitrios Koutsonikolas, Chih-Chun Wang, and Y. Charlie Hu.
    Poster, In ACM International Conference on Mobile Computing and Networking ( MobiCom 2009), Beijing, China, September 20-25, 2009.
  6. CCACK: Efficient Network Coding Based Opportunistic Routing Through Cumulative Coded Acknowledgments.
    Dimitrios Koutsonikolas, Chih-Chun Wang, and Y. Charlie Hu.
    Technical report, Purdue University, August 1, 2009.
  7. Pacifier: High-Throughput, Reliable Multicast without “Crying Babies” in Wireless Mesh Networks.
    Dimitrios Koutsonikolas, Y. Charlie Hu, and Chih-Chun Wang.
    In Proceedings of IEEE INFOCOM 2009, Rio de Janeiro, Brazil, April 19-25, 2009. (acceptance rate 19.6%)
  8. Pacifier: High-Throughput, Reliable Multicast without “Crying Babies” in Wireless Mesh Networks.
    Dimitrios Koutsonikolas, Y. Charlie Hu, and Chih-Chun Wang.
    Submitted to IEEE/ACM Transactions on Networking (ToN).
  9. An Empirical Study of Performance Benefits of Network Coding in Multihop Wireless Networks.
    Dimitrios Koutsonikolas, Y. Charlie Hu, and Chih-Chun Wang.
    In Proceedings of IEEE INFOCOM 2009 Mini-Conference, Rio de Janeiro, Brazil, April 20, 2009. (acceptance rate 26.7%)
  10. An Empirical Study of Performance Benefits of Network Coding in Multihop Wireless Networks.
    Dimitrios Koutsonikolas, Y. Charlie Hu, and Chih-Chun Wang.
    Technical report TR-ECE-08-11, Purdue University, December 1, 2008.
  11. How To Evaluate Exotic Wireless Routing Protocols?
    Dimitrios Koutsonikolas, Y. Charlie Hu, Konstantina Papagiannaki.
    In Proceedings of the 2008 ACM Workshop on Hot Topics in Networking ( HotNets-VII), Calgary, Alberta, Canada, October 6-7, 2008.
  12. XCOR: Synergistic Interflow Network Coding and Opportunistic Routing (abstract). (3rd place in ACM Student Research Competition)
    Dimitrios Koutsonikolas, Y. Charlie Hu, Chih-Chun Wang.
    Poster, In ACM International Conference on Mobile Computing and Networking ( MobiCom 2008), San Francisco, CA, September 14-19, 2008.

Multi-layer techniques and protocols for improving multicast in Wireless Mesh Networks

Our research has focused on improving application-related performance metrics, such as throughput, fairness and reliability. We studied (using simulations and experiments on MAP) the use of link-quality routing metrics for throughput improvement, proposed interference-aware scheduling for providing client fairness, examined packet-level ARQ and FEC mechanisms for providing reliability. We designed, prototyped, and evaluated Pacifier, the first high throughput, reliable multicast protocol addressing the "crying baby" problem in wireless mesh networks. Pacifier combines four building blocks, namely, tree-based opportunistic routing, intra-flow network coding, source rate limiting, and round robin batching, to guarantee 100% reliability for every receiver, while simultaneously offering significant throughput improvements to all of them compared to state-of-the-art protocols.

  1. Pacifier: High-Throughput, Reliable Multicast without “Crying Babies” in Wireless Mesh Networks.
    Dimitrios Koutsonikolas, Y. Charlie Hu, and Chih-Chun Wang.
    In Proceedings of IEEE INFOCOM 2009, Rio de Janeiro, Brazil, April 19-25, 2009. (acceptance rate 19.6%)
  2. Pacifier: High-Throughput, Reliable Multicast without “Crying Babies” in Wireless Mesh Networks.
    Dimitrios Koutsonikolas, Y. Charlie Hu, and Chih-Chun Wang.
    Submitted to IEEE/ACM Transactions on Networking (ToN).
  3. Exploring the Design Space of Reliable Multicast Protocols for Wireless Mesh Networks.
    Dimitrios Koutsonikolas, Y. Charlie Hu.
    In Ad Hoc Networks (Elsevier) Journal (AdHoc), Vol. 7 (5), pp 932-954, July 2009.
  4. High-Throughput Multicast Routing Metrics in Wireless Mesh Networks.
    Sabyasachi Roy, Dimitrios Koutsonikolas, Saumitra Das, and Y. Charlie Hu.
    In Elsevier Ad Hoc Networks Journal (Ad Hoc Networks), Vol. 6 (6), pp. 878-899, August 2008.
  5. An Interference-Aware Fair Scheduling for Multicast in Wireless Mesh Networks.
    Dimitrios Koutsonikolas, Saumitra Das, and Y. Charlie Hu.
    In Elsevier Journal of Parallel and Distributed Computing (JPDC), Special Issue on Behavior, Artefacts, and Solutions in Wireless Mesh Networks, Vol. 68 (3), pp. 372-386, March 2008.
  6. The case for FEC-based Reliable Multicast in Wireless Mesh Networks.
    Dimitrios Koutsonikolas, Y. Charlie Hu.
    In Proceedings of IEEE/IFIP International Conference on Dependable Systems and Networks (DSN 2007), Edinburgh, UK, June 25-28, 2007. (acceptance rate 22.6%)
  7. High-Throughput Multicast Routing Metrics in Wireless Mesh Networks.
    Sabyasachi Roy, Dimitrios Koutsonikolas, Saumitra Das, and Y. Charlie Hu.
    In Proceedings of IEEE International Conference on Distributed Computing Systems (ICDCS 2006), Lisboa, Portugal, July 4-7 2006. (acceptance rate 13.8%)

Exploiting lower layer techniques for performance improvement in Wireless Mesh Networks

We studied the use of lower layer techniques and proposed ways of exploiting such techniques for improving throughput of Wireless Mesh Networks. We designed a microsecond-scale slotted TDM protocol for Wireless Mesh Networks, along with a synchronization algorithm that exploits the TDM structure, and implemented them on a hardware platform with full access to the firmware. We proposed DMesh, an architecture that combines practical, low cost, directional antennas with multiple channels to increase the capacity of Wireless Mesh Networks, and evaluated its performance on MAP testbed. We identified the importance of service provisioning in commercial Wireless Mesh Networks and proposed Apollo, a system that leverages off-the-shelf hardware with software modifications, to provide such a service.

  1. TDM MAC Protocol Design and Implementation for Wireless Mesh Networks.
    Dimitrios Koutsonikolas, Theodoros Salonidis, Henrik Lundgren, Pascal LeGuyadec, Y. Charlie Hu, and Irfan Sheriff.
    In Proceedings of the 4th ACM SIGCOMM International Conference on emerging Networking EXperiments and Technologies ( CoNEXT 2008), Madrid, Spain, December 9-12, 2008. (acceptance rate 17.5%)
  2. Practical Service Provisioning for Wireless Meshes.
    Saumitra Das, Dimitrios Koutsonikolas, and Y. Charlie Hu.
    In Proceedings of the 3rd ACM SIGCOMM International Conference on emerging Networking EXperiments and Technologies ( CoNEXT 2007), New York, NY, December 10-13, 2007. (acceptance rate 20%)
  3. DMesh: Incorporating Practical Directional Antennas in Multi-Channel Wireless Mesh Networks.
    Saumitra Das, Himabindu Pucha, Dimitrios Koutsonikolas, Y. Charlie Hu, and Dimitrios Peroulis.
    In IEEE Journal on Selected Areas in Communications (JSAC), Special Issue on Multi-Hop Wireless Mesh Networks, Vol. 24 (11), pp. 2028-2039, November 2006.

Measurement-based characterization of Wireless Mesh Networks

We used MAP to conduct several measurement studies in different layers of the networking stack. We measured application layer metrics, such as packet loss, jitter, and throughput. At the transport layer, we conducted the first large-scale experimental study of TCP performance in a multihop wireless network. At the physical layer, we identified and experimentally quantified the existence of multi-way interference among neighboring nodes, in addition to the well-studied pair-wise interference.

  1. Measurement-based Characterization of a Wireless Mesh Network.
    Saumitra Das, Dimitrios Koutsonikolas, Y. Charlie Hu.
    Book Chapter, In Handbook of Wireless Mesh and Sensor Networking, McGraw-Hill International, New York.
  2. On TCP Throughput and Window Size in a Multihop Wireless Network Testbed.
    Dimitrios Koutsonikolas, Jagadeesh Dyaberi, Prashant Garimella, Sonia Fahmy, and Y. Charlie Hu.
    In Proceedings of ACM Mobicom International Workshop on Wireless Network Testbeds, Experimental evaluation and CHaracterization ( WiNTECH 2007), Montreal, QC, Canada, September 10, 2007.
  3. Characterizing Multi-Way Interference In Wireless Mesh Networks.
    Saumitra Das, Dimitrios Koutsonikolas, Y. Charlie Hu, and Dimitrios Peroulis.
    In Proceedings of ACM Mobicom International Workshop on Wireless Network Testbeds, Experimental evaluation and CHaracterization (WiNTECH 2006), Los Angeles, CA, September 29, 2006. (acceptance rate 11/31)

Mobile ad hoc, sensor, and multi-robot networks

We studied different topics in wireless ad hoc and sensor networks: robot-assisted localization of sensor networks, energy-efficient localization of mobile multi-robot teams, scalable and energy-efficient geographic multicast routing for sensor networks, collaborative distributed beamforming in sensor networks, and TTL sequence-based route discovery in mobile ad hoc networks.

  1. Hierarchical Geographic Multicast Routing for Wireless Sensor Networks.
    Dimitrios Koutsonikolas, Saumitra Das, Y. Charlie Hu, Ivan Stojmenovic.
    In ACM Wireless Networks, October 2008.
  2. Radiating Sensor Selection for Distributed Beamforming in Wireless Sensor Networks.
    Che-Wei Chang, Akshay Kothari, Syed Ali Raza Jafri, Dimitrios Koutsonikolas, Dimitrios Peroulis, Y. Charlie Hu.
    In Proceedings of IEEE Military Communications Conference ( MILCOM 2008), San Diego, CA, November 17-19, 2008.
  3. Energy-Efficient MAC and Routing Design in Distributed Beamforming Sensor Networks (abstract).
    Dimitrios Koutsonikolas, Syed Ali Raza Jafri, and Y. Charlie Hu.
    Poster, In 3rd ACM SIGCOMM International Conference on emerging Networking EXperiments and Technologies ( CoNEXT 2007) Student Workshop, New York, NY, December 10, 2007.
  4. Hierarchical Geographic Multicast Routing for Wireless Sensor Networks. (Best Paper Award)
    Dimitrios Koutsonikolas, Saumitra Das, Y. Charlie Hu, and Ivan Stojmenovic.
    In Proceedings of International Conference on Sensor Technologies and Applications (SENSORCOMM 2007), Valencia, Spain, October 14-20, 2007. (acceptance rate 34%)
  5. CoCoA: Coordinated Cooperative Localization for Mobile Multi-Robot Ad Hoc Networks.
    Dimitrios Koutsonikolas, Saumitra Das, Y. Charlie Hu, Yung-Hsiang Lu, and C.S. George Lee.
    In Ad Hoc and Sensor Wireless Networks (AHSWN) Journal, Old City Publishing, Ltd., London, UK, Vol. 3(4), pp. 331-352, 2007.
  6. Path Planning of Mobile Landmarks for Localization in Wireless Sensor Networks.
    Dimitrios Koutsonikolas, Saumitra Das, and Y. Charlie Hu.
    In Elsevier Journal of Computer Communications (COMCOM), Special Issue on Sensor-Actuator Networks (SANETs), Vol. 30 (13), pp. 2577-2592, September, 2007. (acceptance rate <25%)
  7. CoCoA: Coordinated Cooperative Localization for Mobile Multi-Robot Ad Hoc Networks.
    Dimitrios Koutsonikolas, Saumitra Das, Y. Charlie Hu, Yung-Hsiang Lu, and C.S. George Lee.
    In Proceedings of ICDCS International Workshop on Dynamic Distributed Systems (IEEE IWDDS 2006), Lisboa, Portugal, July 4-7 2006.
  8. Path Planning of Mobile Landmarks for Localization in Wireless Sensor Networks.
    Dimitrios Koutsonikolas, Saumitra Das, and Y. Charlie Hu.
    In Proceedings of ICDCS International Workshop on Ad hoc and Sensor Networks (IEEE WWASN 2006), Lisboa, Portugal, July 4-7 2006.
  9. On optimal TTL sequence-based route discovery in MANETs.
    Dimitrios Koutsonikolas, Saumitra Das, Himabindu Pucha, and Y. Charlie Hu.
    In Proceedings of the 2nd ICDCS International Workshop on Wireless Ad Hoc Networking (IEEE WWAN 2005), Columbus, Ohio, June 6-9, 2005.

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