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Cognitive Radio in a Frequency-Planned Environment: Can it Work? Erik Axell

Cognitive Radio in a Frequency-Planned Environment: Can it Work? Erik Axell. Erik G. Larsson and Mikael Skoglund, IEEE GLOBECOM, 2007. SENDORA – SEnsor Network for Dynamic and cOgnitive Radio Access. Linköping University THALES Communications Institut Eurocom Kungliga Tekniska Högskolan

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Cognitive Radio in a Frequency-Planned Environment: Can it Work? Erik Axell

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  1. Cognitive Radio in a Frequency-Planned Environment: Can it Work?Erik Axell Erik G. Larsson and Mikael Skoglund, IEEE GLOBECOM, 2007

  2. SENDORA – SEnsor Network for Dynamic and cOgnitive Radio Access • Linköping University • THALES Communications • Institut Eurocom • Kungliga Tekniska Högskolan • Helsinki University of Technology • Norwegian University of Science and Technology • Telenor ASA • Universitat de València • Università degli Studi di Roma

  3. The Scenario

  4. Some Fundamental Questions • Cognitive radios must transmit at very low power. How low must it be? • Cognitive radios must expect very low C/(I+N) from primary system. What orders of magnitude? • At an acceptable loss in primary system coverage, how large is the “area of cognitive operation”?

  5. Basic Assumptions and Some Terminology • Path loss and lognormal fading • n-reuse frequency planning for primary system • SINR for primary system, with primary base station power P0 •  -SINR is the SINR achieved with probability 1-

  6. Primary System Operating Point • Primary system is either noise limited, interference limited, or in-between. Quantify this in terms of ratio between noise and co-channel interference at the primary cell border: •  - [dB]: purely noise limited •   [dB]: purely interference limited

  7. With Cognitive Users • SINR is now • Suppose we can accept reduction in primary cell radius from r to r’. Then assume M cognitive users, each with power P, uniformly distributed in circular ring. How large can the circular ring, the ”area of cognitive operation,” be?

  8. Feasible Operating Regions, with 7-reuse

  9. Feasible Operating Regions, with 21-reuse

  10. “Forbidden Region,” 12-reuse

  11. Asymptotic Sensitivity Requirements • The additional (compared to primary receivers) sensitivity requirement  isand satisfies

  12. Main Conclusions • If cognitive users are to be introduced, they must • Be few in numbers, since the aggregate power scales with the number of devices • Transmit with extremely low power, such as -30 dB below the primary system • Have very sensitive radios, in the order of 20-30 dB more sensitive than the primary system radios.

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