Otilia Popescu and Christopher Rose, "Sum Capacity and TSC Bounds in Collaborative Multibase Wireless Systems," IEEE Transactions on Information Theory, Vol. 50, No. 1, pp. 2433-2438, October 2004. [PDF]

Otilia Popescu and Christopher Rose, "Waterfilling May Not Good Neighbors Make", Proceedings of IEEE Globecom '03, San Francisco, CA, December 2003, pp. 1766-1770. [PDF]


Dynamic Spectrum Management

Project Objectives:
The establishment of unlicensed communication bands has successfully encouraged innovation, most recently in wireless devices and infrastructure that use unlicensed spectrum to provide connections to the Internet. A key aspect of Internet usage is an almost unlimited capacity for growth. While the overload of any finite band may be inevitable, the goals of this project are to increase the capacity of the available unlicensed bands as much as possible, and to develop approaches that can predict overloads and prevent sudden, unexpected failure modes.

Technology Rationale:
For unlicensed wireless, the transition from 11 Mb/s 802.11b to 54 Mb/s 802.11a marks the start of an industry race toward ever-higher data rates. These high rate internet services will need to coexist with the emergence of wide variety of wireless devices, ranging from low bit rate sensors to high resolution full motion video cameras. The combination of increasing data rates and the proliferation of devices could easily lead to inefficiency in the use of unlicensed spectrum due to a combination of overuse and failure to develop mechanisms for efficient sharing of this resource. Results from the project are expected tobe of value to both policy makers and emerging unlicensed band wireless Internet providers as well as wireless technologists.

Technical Approach:
We seek to promote efficient use of unlicensed spectrum by combining an engineering and technology perspective with insights from the literatures on regulation, property rights, and economic coordination. The team, including researchers from Michigan State and Cornell with expertise in property rights and networking fairness, is developing a general framework for understanding cooperation in unlicensed band wireless networks by studying the following issues:

  • Property rights as applied to spectrum management
  • Protocols for collaboration between technology neutral wireless devices
  • Pricing mechanisms for efficient and fair sharing of congested unlicensed spectrum
  • Radio-level interference avoidance techniques

The above problems are being studied with a combination of formal and conceptual analysis, simulation and experimental methods, including a dynamic spectrum management testbed which implements potential collaboration protocols and cooperation models. The goal is to preserve the “creative chaos” of the unlicensed bands while creating a degree of long term stability and predictability that is appropriate to the size of the investments being made and the strategic importance of these uses to the nation.

Results To Date and Future Work Plan:
Funded by the NSF, this project began in Fall 2002. Ongoing research efforts at WINLAB include:

  • Interference Avoidance for Multiple Basestation Systems (C. Rose)
  • Pricing Mechanisms as Enablers for Forwarding in Wireless Networks (N. Mandayam, S.C. Mau)
  • Cooperative Diversity with Distributed Codes (P. Spasojevic)
  • Spectrum Etiquette Protocol for Coordination of Radio Devices in Unlicensed Bands (D. Raychaudhuri)
  • Dynamic Spectrum Management (D. Raychaudhuri)

The common theme of these projects is the use of sharing mechanisms such as power control, pricing, etiquette protocols, and transmitter optimization. In addition to various simulation and analysis models, a proof-of-concept unlicensed band spectrum etiquette prototype has been demonstrated as part of this project. An informal spectrum workshop was held at WINLAB in November 2003 with preliminary results reported on all the above projects.

The spectrum project at WINLAB has led to new NSF funded projects on the related topic of cognitive radio

Prof. Roy D. Yates

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