Tag Archives: wireless

Wireless Radio Architecture

Wireless Radio Architecture

As we move forward towards the next generation of wireless protocols, the push for a better radio physical layer is ever increasing. Conventional radio architectures are limited to narrow operating regions and fails to adapt with changing technology. This is further strengthened with the advent of cognitive radio, which needs a more versatile and flexible framework that is programmable within the timing constraints of a protocol. In this research, we present an architecture for Software Defined Cognitive Radio that caters to the specific baseband processing requirements in a changing environment. We aim to provide more flexibility by deconstructing the radio pipeline into a framework of user controlled kernels that can be reconfigured at run-time. This architecture provides the barebones of a OFDM based radio physical layer that can adapt to perform a varied number of tasks in different radio networks. We also present a novel message based real-time reconfiguration method to transmit and receive a wide range of waveforms used in concurrent wireless protocols.

Publications

Security, Privacy & Anonymity

Security, Privacy & Anonymity

We have been actively working on several projects within the realm of security, privacy, and anonymity. The first has been a security analysis of Tor, a popular onion routing network used to anonymize TCP connections. Specifically, this work has examined how performance optimizations added to enhance the system’s performance are fundamentally at odds with the network’s ability to ensure strong anonymity properties. Through experimentation with an isolated Tor network deployed on Planetlab, we show that an low-resource adversary can compromise over 46% of all circuits through the network; this is a significant increase over the previously accepted analytical attack success prediction.

Another project has focused on characterizing and modeling anonymous network usage, focusing on Tor, as it is the most widely used anonymous network. We participate in the Tor network as a Tor router and provide a breakdown of application-level protocols that can be observed within Tor, a geopolitical distribution of Tor routers and clients, and a characterization of how networks like Tor are being abused by malicious parties. Our main objective through this study is to better understand the Tor network and through this understanding, propose improvements.

We have also been working on anonymizing protocols for specific applications. In particular, we proposed a simple protocol to add “plausible deniability” to the popular BitTorrent peer-to-peer file sharing protocol. In the current BitTorrent protocol, the identities of all peers sharing a particular file are published by the “tracker” server. Our protocol, called BitBlender, provides light-weight anonymity (in the spirit of the Crowds anomymizing network) by inserting special peers called “relay peers” into the BitTorrent system architecture. These peers act as proxies for other peers that actively share a particular file. In doing so, it becomes unclear to an adversary which peers listed by the trackers are engaged in the sharing of the file and which peers are merely relays. The adversary must now invest more resources and perform more sophisticated (and error-prone) traffic analysis tactics to ascertain the identities of the real peers.

Our projects also focus on security and privacy in wireless networks. Such completed projects include an identifier-free wireless link-layer, a confidential service discovery protocol, an accurate technique for wireless device driver fingerprinting, a method for constructing implicit identifiers using information extracted from the wireless physical layer, and a set of techniques to detect “evil twin” access points in 802.11.

Selected Publications

  • Kevin Bauer, Micah Sherr, Damon McCoy, and Dirk Grunwald. ExperimenTor: A Testbed for Safe and Realistic Tor Experimentation. 4th USENIX Workshop on Cyber Security Experimentation and Test (CSET 2011). San Francisco, CA. (August 2011)
  • Mashael AlSabah, Kevin Bauer, Ian Goldberg, Damon McCoy, Dirk Grunwald, Stefan Savage, and Geoffrey Voelker – DefenestraTor:  Throwing Out Windows in Tor. 11th Privacy Enhancing Technologies Symposium (PETS 2011) Waterloo, ON, July 2011
  • Harold Gonzales, Kevin Bauer, Janne Lindqvist, Damon McCoy, Douglas Sicker – Practical Defenses for Evil Twin Attacks in 802.11. Proceedings of the IEEE Globecom Communications and Information Security Symposium , Miami, FL, December, 2010
  • Dirk Grunwald, Aaron Beach, Kevin Bauer, Qin Lv, Douglas Sicker – The Risks and Regulation of Location. Proceedings of the 38th Research Conference on Communication, Information and Internet Policy (TPRC) , Arlington, VA, October, 2010
  • J. Trent Adams, Kevin Bauer, Asa Hardcastle, Dirk Grunwald, Douglas Sicker – Automated Tracking of Online Service Policies. Proceedings of the 38th Research Conference on Communication, Information and Internet Policy (TPRC) , Arlington, VA, October, 2010
  • Kevin Bauer, Joshua Juen, Nikita Borisov, Dirk Grunwald, Douglas Sicker, Damon McCoy – On the Optimal Path Length for Tor. HotPETS 2010
  • Kevin Bauer, Dirk Grunwald, Douglas Sicker – Predicting Tor Path Compromise by Exit Port. Proceedings of 2nd IEEE International Workshop on Information and Data Assurance , Phoenix, AZ, December, 2009
  • Kevin Bauer, Damon McCoy, Dirk Grunwald, Douglas Sicker – BitStalker: Accurately and Efficiently Monitoring BitTorrent Traffic. Proceedings of the 1st IEEE Workshop on Information Forensics and Security , London, United Kingdom, December, 2009
  • Kevin Bauer, Damon McCoy, Eric Anderson, Markus Breitenbach, Greg Grudic, Dirk Grunwald, Douglas Sicker – The Directional Attack on Wireless Localization – or – How to Spoof your Location with a Tin Can. Proceedings of the IEEE Globecom Communications and Information Security Symposium , Honolulu, HI, USA, December, 2009
  • Kevin Bauer, Dirk Grunwald, Douglas Sicker – The Arms Race in P2P. Proceedings of the 37th Research Conference on Communication, Information and Internet Policy , Arlington, VA, USA, September, 2009
  • Kevin Bauer, Damon McCoy, Ben Greenstein, Dirk Grunwald, Douglas Sicker – Physical Layer Attacks on Unlinkability in Wireless LANs. Proceedings of the 9th Privacy Enhancing Technologies Symposium (PETS 2009) , Seattle, WA, USA, August, 2009
  • Kevin Bauer, Dirk Grunwald, Douglas Sicker – The Challenges of Stopping Illegal Peer-to-peer File Sharing. Proceedings of National Cable & Telecommunications Association Technical Papers , Washington, DC, USA, April, 2009
  • Kevin Bauer, Harold Gonzales, Damon McCoy – Mitigating Evil Twin Attacks in 802.11. Proceedings of 1st IEEE International Workshop on Information and Data Assurance (WIDA 2008) in conjunction with the 27th IEEE International Performance Computing and Communications Conference (IPCCC 2008) , Austin, TX, USA, December, 2008
  • Kevin Bauer, Damon McCoy, Dirk Grunwald, Douglas Sicker – BitBlender: Light-Weight Anonymity for BitTorrent. Proceedings of the Workshop on Applications of Private and Anonymous Communications (AlPACa 2008) in conjunction with SecureComm 2008 , Istanbul, Turkey, September, 2008
  • Damon McCoy, Kevin Bauer, Dirk Grunwald, Tadayoshi Kohno, Douglas Sicker – Shining Light in Dark Places: Understanding the Tor Network. Proceedings of the 8th Privacy Enhancing Technologies Symposium (PETS 2008) , Leuven, Belgium, July, 2008
  • Kevin Bauer, Damon McCoy, Ben Greenstein, Dirk Grunwald, Douglas Sicker – Using Wireless Physical Layer Information to Construct Implicit Identifiers. Technical Report presented at HotPETS in conjunction with the 8th Privacy Enhancing Technologies Symposium (PETS 2008) , Leuven, Belgium, July, 2008
  • Ben Greenstein, Damon McCoy, Jeffrey Pang, Tadayoshi Kohno, Srinivasan Seshan, David Wetherall – Improving Wireless Privacy with an Identifier-Free Link Layer Protocol. MobiSys ’08: 6th International Conference on Mobile Systems, Application, and Services , Breckenridge, CO, USA, June, 2008
  • Jeffrey Pang, Ben Greenstein, Damon McCoy, Srinivasan Seshan, and David Wetherall – Tryst: The Case for Confidential Service Discovery. HotNets VI: The Sixth Workshop on Hot Topics in Networks , Atlanta, GA, USA, October, 2007
  • Kevin Bauer, Damon McCoy, Dirk Grunwald, Tadayoshi Kohno, Douglas Sicker – Low-Resource Routing Attacks Against Tor. Proceedings of the Workshop on Privacy in the Electronic Society (WPES 2007) , Alexandria, VA, USA, October, 2007
  • Douglas Sicker, Damon McCoy, Dirk Grunwald – A Mechanism for Detecting and Responding to Misbehaving Nodes in Wireless Networks. SDR Workshop, IEEE SECON , 2007.
  • Jason Franklin, Damon McCoy, Parisa Tabriz, Vicentiu Neagoe, Jamie Van Randwyk, Douglas Sicker – Passive Data Link Layer 802.11 Wireless Device Driver Fingerprinting. Proceedings of the 15th USENIX Security Symposium , Vancouver, BC, Canada, August, 2006

Cognitive Radio and Unmanned Aircraft

The Role of Cognitive Radio in Remote Operation of UAS

PIs: Timothy X Brown and Douglas Sicker

Unmanned Aircraft Systems (UAS) have the potential to play an important social, economic, and security role in the National Airspace System (NAS). The largest current barrier to the use of unmanned aircraft in the NAS is satisfaction of FAA regulations regarding safe flight operations and Air Traffic Control (ATC). In particular, the FAA requires all aircraft operating in the NAS to have detect, sense, and avoid capabilities; communication with ATC; as well as communication with a remote operator. Thus, one of the primary concerns in UAS deployment is the availability and allocation of bandwidth and spectrum for control, command, and communication (C3).

A significant C3 role can be filled by new radio technologies. One such technology is cognitive radio (CR). CRs enable fine-grained time, frequency, and location allocations of radio spectrum for communication. Current approaches allocate large swaths of spectrum over large regions for decades at a time. Finer grained allocations foster more efficient use of the spectrum with greater communication capacity to support future UAS growth and innovation. More importantly, CR can make such allocations automatically while still adhering to government policies. This automation provides government regulatory flexibility that is not currently present. However, such automated allocation has operational, security, and policy implications that are yet to be addressed for UAS.

This project investigates the possible operational models and infrastructure required to support CR-based spectrum allocation at different levels of granularity; and the security and policy models needed to support CR-based spectrum allocation. Information from this research will be relevant for the development of future requirements and standards for UAS and the NAS in general.

Realistic Simulation

Realistic Simulation of Wireless Networks

Simulation is commonly used in networking research to prototype and validate new protocols and ideas. Hence, the realism of these simulators is crucial in order for the results they produce to be trustworthy and interpretable. To this end, we are working to find limitations in existing simulation methodologies and improve them through direct measurement, modeling, and implementation.

Selected Publications

  • Eric Anderson, Gary Yee, Caleb Phillips, Douglas Sicker, and Dirk Grunwald. The Impact of Directional Antenna Models on Simulation Accuracy. 7th International Symposium on Modeling and Optimization in Mobile, Ad Hoc, and Wireless Networks (WiOpt 2009). Seoul, Korea. June 23 – 27, 2009.
  • Caleb Phillips, Suresh Singh, Douglas Sicker, and Dirk Grunwald. Techniques for Simulation of Realistic Infrastructure Wireless Network Traffic. 7th International Symposium on Modeling and Optimization in Mobile, Ad Hoc, and Wireless Networks (WiOpt 2009). Seoul, Korea. June 23 – 27, 2009.

Software and Data

Usable Coverage Mapping

Usable Coverage Mapping for Large Area Networks

PIs: Douglas Sicker and Dirk Grunwald

The problem of mapping the extent of “usable” coverage of an existing wireless network is important

Measurements of recieved signal strength of a municipal WiFi network in Portland, Oregon.

in a large number of applications, including communicating the abilities of the network to users, identifying
coverage gaps and planning expansion, and determining possible sources of interference with other
networks. Our research here addresses fundamental but unsolved problems of measurement-based wireless coverage mapping: where should measurements be made, how many are necessary, and what can be said about
the coverage at points that have not been measured.

Downloads

Selected Publications

  • Caleb Phillips, Douglas Sicker, and Dirk Grunwald. The Stability of the Longley-Rice Irregular Terrain Model for Typical Problems. University of Colorado at Boulder, Tech. Report. CU-CS-1086-11. September, 2011. (download)

  • Caleb Phillips, Douglas Sicker, and Dirk Grunwald. Bounding the Practical Error of Path Loss Models in Urban Environments. IEEE Dynamic Spectrum Access Networks 2011 (DySPAN 2011). Aachen, Germany. May 3-6, 2011.
  • Caleb Phillips, Scott Raynel, Jamie Curtis, Sam Bartels, Douglas Sicker, Dirk Grunwald and Tony McGregor. The Efficacy of Path Loss Models for Fixed Rural Wireless Links. Passive and Active Measurement Conference 2011 (PAM 2011). Atlanta, Georgia. March 20-22, 2011.
  • Caleb Phillips, Russell Senior, Douglas Sicker, and Dirk Grunwald. Robust Coverage and Performance Testing for Large-Area Wireless Networks. AccessNets 2008. Las Vegas, Nevada. October 15 – 17, 2008.

Caleb Phillips, Douglas Sicker, and Dirk Grunwald. The Stability of the Longley-Rice Irregular Terrain Model for Typical Problems. University of Colorado at Boulder, Tech. Report. CU-CS-1086-11. September, 2011. (download)

Directional and Phased Array Networks

Directional and Steerable Antennas for Optimizing Networks

PIs: Douglas Sicker and Dirk Grunwald

Directional Antennas emphasize gain in some directions and de-emphasize it in others. Steerable and phased array antennas allow these patterns to be changed in real-time.

As the demand for wireless networks grows, the research community continues to seekmethods for improving network performance. On method for improving network throughput involves using directional antennas to increase signal gain and/or decrease interference. Our work in this area focuses on real-world development and evaluation of directional and phased array antenna systems. To this end, we have built the first large-scale testbed of outdoor phased array antennas, suggested new models for directional antenna use in simulations based on measurements, and have proposed new protocols that optimize their behavior in both time and space.

Selected Publications

The CU WART testbed is the first wide area testbed of functional phased array antennas

  • Eric Anderson, Caleb Phillips, Douglas Sicker, and Dirk Grunwald. Signal Quality Pricing: Decomposition for Spectrum Scheduling and System Configuration. IEEE Dynamic Spectrum Access Networks 2011 (DySPAN 2011). Aachen, Germany. May 3-6, 2011.
  • Eric Anderson, Caleb Phillips, Douglas Sicker, and Dirk Grunwald. Modeling Environmental Effects on Directionality. Mathematical and Computer Modeling Journal. Special Issue on Modeling and Simulation of Wireless Networks. June, 2010. Elsevier.
  • Eric Anderson, Caleb Phillips, Douglas Sicker, and Dirk Grunwald. Challenges in Deploying Steerable Wireless Testbeds. TridentCom 2010. Berlin, Germany. May 18-20, 2010.
  • Gary Yee, Caleb Phillips, Douglas Sicker, and Dirk Grunwald. Wireless Networking Optimizations for Studying Algorithm Interactions. University of Colorado at Boulder, Tech. Report. CU-CS-1070-10. 2010.
  • Eric Anderson, Caleb Phillips, Douglas Sicker, and Dirk Grunwald. Modeling Environmental Effects on Directionality in Wireless Networks. 5th International workshop on Wireless Network Measurements (WiNMee 2009). Seoul, Korea. June 26, 2009.
  • Michael Buettner, Eric Anderson, Gary Yee, Dola Saha, Doug Sicker, Dirk Grunwald – A Phased Array Antenna Testbed for Evaluating Directionality in Wireless Networks. MobiEval ’07 , San Juan, Puerto Rico, USA, June, 2007.
  • Neufeld, M., Grunwald, D. – Using phase array antennas with the 802.11 MAC protocol. Broadband Networks, 2004. BroadNets 2004. Proceedings. First International Conference on pp. 733-735, 25-29 Oct. 2004

Software and Data Downloads

SMACK

SMACK (SiMultaneous ACKnowledgment) and PAMAC (PHY-Aided MAC)

A Broadcast message followed by two SMACKs, using three prototype radio platforms

Network protocol designers, both at the physical and network level, have long considered interference and simultaneous transmission in wireless protocols as a problem to be avoided. This, coupled with a tendency to emulate wired network protocols in the wireless domain, has led to artificial limitations in wireless networks. In this paper, we argue that wireless protocols can exploit simultaneous transmission to reduce the cost of reliable multicast by orders of magnitude. With an appropriate application inter- face, simultaneous transmission can also greatly speed up common group communication primitives, such as anycast, broadcast, leader election and others.

In this research, we focus on using Orthogonal Frequency Division Modulation (OFDM) to provide distinct orthogonal signals. OFDM is a mechanism that splits the available spectrum into a number of orthogonal non-interfering subchannels. Being orthogonal, each of the subcarriers can be treated as an information carrying medium without significant interference with another subcarrier. In our protocol, since we only need to transmit a “yes” or “no” for an acknowledgment, we assign subcarriers to individual nodes. Using multicarrier modulation techniques, the AP receives ACKs from a greater number of clients in the shortest possible time, dramatically reducing the time to gather reliable acknowledgments for broadcasts.

Variation of Spectrum over Time, while transmitting SMACK

We exploit a programmable physical layer and SMACK to have clients signal whether they have packets to send. By detecting the high energy at the simultaneous transmission, the AP gets the following information: a) which stations have packets to send and b) whether the traffic load is high, medium or low. The AP schedules clients efficiently while wasting little of the spectrum on signaling overhead. The proposed protocol is a) fast, since no packet transmission is required for polling responses and all clients respond concurrently; b) reliable, as the poll response is contention free and c) scalable. We term this MAC protocol as PHY Aided MAC or PAMAC in short.

Publications

Wireless

Wireless Networking Research

Non-Contiguous OFDM

Spectrogram using Non-Contiguous OFDM

Wireless networks provide data networking for more people than any other network technology. At Colorado, we’re focused on technologies that allow software defined cognitive radios to enhance spectrum use. Our research focuses on prototypes, technical mechanisms and analysis. We’ve developed a series of prototype systems based on FPGA’s for signal processing. We have developed a sophisticated software stack that lets us easily manipulate an OFDM waveform for real-time, high-bandwidth application.Earlier systems used devies from Nallatech and Fidelity Comtech. We’ve also done substantial work towards investigating the efficacy of directional and phased-array antenna technology in optimizing wireless networks and adhoc unmanned aerial networks, have developed more robust and realistic simulation techniques, and have done some work towards investigating coverage mapping strategies for large area wireless networks.

Active Projects

Hardware & Systems

  • NallaTech/Fidelity Comtech Software Defined Radio
  • GENI Cognitive Radio
  • Directional Antenna Radio

Recent Publications

  • Eric Anderson, Caleb Phillips, Douglas Sicker, and Dirk Grunwald. Signal Quality Pricing: Decomposition for Spectrum Scheduling and System Configuration. IEEE Dynamic Spectrum Access Networks 2011 (DySPAN2011). Aachen, Germany. May 3-6, 2011.
  • Aveek Dutta, Dola Saha, Dirk Grunwald, Douglas Sicker, SMACK – A SMart ACKnowledgment Scheme for Broadcast Messages in Wireless Networks,  ACM SIGCOMM, Barcelona, Spain, August 2009
  • Eric Anderson, Caleb Phillips, Douglas Sicker, and Dirk Grunwald. Modeling Environmental Effects on Directionality. Mathematical and Computer Modeling Journal. Special Issue on Modeling and Simulation of Wireless Networks. June, 2010. Elsevier.
  • Caleb Phillips, Douglas Sicker, and Dirk Grunwald. Bounding the Practical Error of Path Loss Models in Urban Environments. IEEE Dynamic Spectrum Access Networks 2011 (DySPAN 2011). Aachen, Germany. May 3-6, 2011.