1 / 20

Detecting Primary Receivers for Cognitive Radio Applications

Detecting Primary Receivers for Cognitive Radio Applications. Ben Wild, Kannan Ramchandran UC Berkeley Dept. of Electrical Engineering and Computer Science 11/9/2005. Work funded by NSF ITR 3R Spectrum Sharing grant. Why Detect Receivers?.

shawna
Download Presentation

Detecting Primary Receivers for Cognitive Radio Applications

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Detecting Primary Receivers for Cognitive Radio Applications Ben Wild, Kannan Ramchandran UC Berkeley Dept. of Electrical Engineering and Computer Science 11/9/2005 Work funded by NSF ITR 3R Spectrum Sharing grant

  2. Why Detect Receivers? • FCC Interference temperature proposal not well defined without knowing where receiver located. • Interference happens at the receiver!. • Many Applications.. we will discuss re-use of TV band for unlicensed use in this talk.

  3. Detection of Transmitters • Shadowed CR could mistakenly use channel • CR must be able to detect weaker signals, making the no-talk zone larger. TV decodability region CR

  4. Detecting Receivers • Allow secondary users in licensed bands if they can guarantee that they do not interfere with primary receivers. Ch. 3,4,5,6,7 Ch.5 Ch.9 Ch.3 shadower Ch.5 Ch.4 Ch.7 Ch.6

  5. Detecting “Passive” Receivers • Legacy receivers must be able to function interference free. • All RF receivers leak local oscillator out of antenna. • Solution: Low cost sensors to detect leakage. Reverse LO leakage

  6. LO Leakage versus Model Year Figure 2: TV LO Leakage Power versus Year [3]

  7. TV Detector Vans • Used in Britain since 1920s

  8. Cognisensor • Optimal to connect sensor directly between receiver and antenna. • Increases LO power coupled to sensor, reduces interference. • Allows sensor to reuse receive antenna for transmission. Cognisensor, close up Antenna input CR Duplexer cognisensor Transmitter Directional Coupler LO Detector Receiver Input

  9. Detector Architectures Envelope Detector Decision IF cos(ot)+n(t) cos((0+)t+) PLL Non-Coherent LPF v(t) Decision cos(ot)+n(t) cos(0t) PLL Coherent

  10. Detection Time (coherent) For 10-4 probability of error For -120dbm coupled LO leakage power

  11. Experimental Results Frequency Synthesizer Mixer TV Tuner Amplifiers IF filter Envelope Detector Amplifier Non-coherent detector prototype

  12. System Considerations • How to best combine information from primary receivers with information from transmitters? • How do CRs collaborate to switch to unused channel when channel becomes occupied? • How to make the system scalable to many CRs?

  13. Interference Avoidance • Primary receivers communicate channel usage information over a control channel to any secondary user that is within its interference radius. • Secondary user must switch to unused channel fast enough to cause negligible interference. Available channels Available channels Ch. 7 Ch. 13 UHF 2-12 UHF 2-6,8-13 Interference radius Ch. 2 CR

  14. Interference Avoidance • Secondary user must switch to unused channel fast enough to cause negligible interference. Available channels Available channels Ch. 2 Ch. 13 UHF 3-13 UHF 2-12 Interference radius Ch. 3 Request Ch.3-13 CR Approve Ch.3

  15. Applicability • Television receivers. • Cable headend receivers. • Wireless microphone receivers. • Public safety receivers. • Many other types of receivers.

  16. Concerns with Approach • Who will pay for them? • Cost (TV):  ($5/each)(30M) = ($150M), projected Wi-Fi sales in 2009  $8B (probably much larger once TV band is opened). Government will spend > $1B on D/A conversion boxes. • Will sensor impact receiver reception quality? • Negligible 0.5dB decrease in SNR. Can recover by increasing transmit power by 10%. • How often do batteries of sensors need to be replaced? • 10 years. Assuming 1km range, 25% on, 1 D battery.

  17. Conclusions and Future Work • Detecting primary receivers solves the hidden node problem, and could be more efficient than detecting transmitters alone. • Showed with this approach, interference temperature could become simple to estimate, is not ill-defined anymore. • Demonstrated prototype sensor node to detect primary receiver channel usage. Future Work: • Analyze scalability issues. • Build system around this concept.

  18. References [1] A. Sahai, N. Hoven, and R. Tandra, “Some Fundamental Limits on Cognitive Radio” Allerton Conference on Communication, Control, and Computing, October 2004. [2] N. Hoven, "On the feasibility of Cognitive Radio”, Master's thesis, University of California at Berkeley, Berkeley, CA, 2005. [3] Weiss, S. Merrill, Weller, Robert D., Driscoll Sean D. “New measurements and predictions of UHF television receiver local oscillator radiation interference” [online]. Available: h-e.com/pdfs/rw_bts03.pdf

  19. Backup Slides

  20. Spectrum Allocation vs. Usage • Perceived Scarcity vs. Actual Utilization

More Related