1. CS541 Advanced Networking 1 Cognitive Radio Networks Neil Tang 1/28/2009

2. CS541 Advanced Networking 2 Outline  Motivation  Definition  Network Architecture  Characteristics  Critical Issues  MAC layer Challenges  Upper Layer Challenges  Cross-layer Optimization

3. CS541 Advanced Networking 3 Motivation If the static approach is used to manage the spectrum:  On one hand, certain parts of the spectrum, such as the 2.4GHz band and the 5GHz band, are heavily used by various wireless devices.  On the other hand, a significant amount of spectrum remains under- utilized or even not utilized at all.

4. CS541 Advanced Networking 4 Cognitive Radio  “A Cognitive Radio is a radio that can change its transmitter parameters based on interaction with the environment in which it operates.”  A cognitive radio is able to sense and analyze the spectrum, and make a decision on the selection of the spectrum band, data rate and so on.

5. CS541 Advanced Networking 5 Network Architecture

6. CS541 Advanced Networking 6 Characteristics  Dynamic spectrum availability  Spectrum heterogeneity

7. CS541 Advanced Networking 7 Critical Issues  Spectrum sensing  Spectrum analysis: Characterize each spectrum band (transmission range, data rate, packet loss ratio, etc).  Spectrum mobility/handoff  Spectrum sharing: Spectrum allocation and access  Upper layer issues: routing and transport layer

8. CS541 Advanced Networking 8 MAC Layer Challenges  Centralized VS. distributed  Inter-network interference  Spectrum heterogeneity  Common Control Channel (CCC) and message exchange  Maximize throughput and achieve fairness  Minimize power consumption

9. CS541 Advanced Networking 9 Upper Layer Challenges  Route discovery: broadcast on a common channel or a set of channels.  Route selection is coupled with spectrum selection.  Re-route scheme  End-to-end rate depends on spectrum allocation.

10. CS541 Advanced Networking 10 Cross-layer Optimization Joint routing and spectrum sharing  Maximize the end-to-end rate.  Minimize the end-to-end delay and satisfy a given end-to-end rate requirement.