Agenda

1. Frequency Agile Spectrum Access TechnologiesThis Presentation was originally made to anFCC Workshop on Cognitive RadiosMay 19, 2003 by one of Bill’s colleagues.(Bill was kind enough to share this information with 802.18 SG1 in the interest of promoting discussion.) Bill Byrnes, Shared Spectrum Co.

2. Requirements Spectrum occupancy characteristics Significant amount of “low hanging fruit” Spectrum access methods Listen-Before Talk “TDMA” spectrum Broadcast spectrum Probe Geo-location/database Agenda Bill Byrnes, Shared Spectrum Co.

3. Create insignificant interference Secondary operation with minimal requirement for coordination with primary system licensees Unlicensed with equipment certifications on a system basis to assure avoidance of interference Operate in multiple bands Assured capacity Offer cost/capacity/link range/deployment benefits Access more (5 X?) spectrum than any current system Operate in VHF/UHF TV band Rapid spectrum agreements for itinerate use Frequency Agile Radio Requirements Bill Byrnes, Shared Spectrum Co.

4. “In many bands, spectrum access is a more significant problem than physical scarcity of spectrum, in large part due to legacy command-and-control regulation that limits the ability of potential spectrum users to obtain such access.”1 Shared Spectrum’s measurements indicate Many bands have no detectable occupancy Some bands have low occupancy Some bands have high occupancy Spectrum Occupancy Is Low Note 1: FCC Spectrum Policy Task Force Report, page 3 Bill Byrnes, Shared Spectrum Co.

5. Typical Spectrum Occupancy Measurement FCC should conduct and publish spectrum occupancy measurements to identify low occupancy bands No signals Medium and short duration signals Bill Byrnes, Shared Spectrum Co.

6. Measurements show a large quantity of long duration, large area spectrum holes “Simple” spectrum access methods are sufficient Minimal coordination between transceivers Moderate computational costs Later evolve algorithms to handle more complex situations Short duration, small spectrum holes Optimize frequency assignments for increased capacity Initially Harvest the Low Hanging Fruit Bill Byrnes, Shared Spectrum Co.

7. Requirements Spectrum occupancy characteristics Significant amount of “low hanging fruit” Spectrum access methods Listen-Before Talk “TDMA” spectrum Broadcast spectrum Probe Geo-location/database Agenda Bill Byrnes, Shared Spectrum Co.

8. Pmax TX = 10*log10(k * T * B) + PPrimary – Pmeasured - Margin Margin = 10 to 20 dB, required for cummulative effects, rapid propagation changes, false alarm minimization T – Interference Noise Temperature, in K B = signal bandwidth, in Hz Adaptive, Receive-Only Spectrum Access Method Bill Byrnes, Shared Spectrum Co.

9. Frequency Agile Transceivers Exclusion Zone Primary Transceivers Interference/Connectivity Limit Frequency Agile Coverage “Morphs” To Fit Primary Users Hidden-node problem overcome by each Frequency Agile transceiver listening to all Primary users within range Bill Byrnes, Shared Spectrum Co.

10. High Sensitivity Receiver Performance Bill Byrnes, Shared Spectrum Co.

11. West Virginia location • 3 m antenna height 10 ground vehicles spread over 25 km moving at 25 km/hr 10 stationary ground vehicles spread over 25 km Simulation Example • Primary users are stationary • XG users are mobile • Omni-directional antennas • 420 MHz signal frequency Bill Byrnes, Shared Spectrum Co.

12. Actual loss Interference Link closure • Longley-Rice Model • 420 MHz Free space loss Propagation Losses Bill Byrnes, Shared Spectrum Co.

13. TX Power and Interference Frequency Agile network reduces TX power automatically XG TX Power (dBm) Network needs switch to another frequency at low TX power levels Target interference level of –100 dBm Primary Interference Level (dBm) Bill Byrnes, Shared Spectrum Co.

14. Listen-Only Method in the Broadcast Bands PT (kW) TV Receiver HAAT (m) L2 TV Transmitter L1 TV Receiver Differential propagation loss = L1-L2 Frequency Agile Transceiver Region of Potential Interference Bill Byrnes, Shared Spectrum Co.

15. Transmit Power Rule • Pmax TX = Po if Primary signal is not detected • = Transmission prohibited if Primary signal is detected • where, Pmax TX = Frequency Agile transmitter power level, in dBm • Po = specified power value, in dBm Bill Byrnes, Shared Spectrum Co.

16. Minimal Interference TV Receiver with Grade B reception LOS Location TV Transmitter LOS to Frequency Agile Transceiver Building Blockage Terrain Blockage Frequency Agile Transceiver Multi-Path Effects • Joint probability of three conditions • Agile Receiver doesn’t detect TV signal • Primary user receives TV signal • D/U < 15 dB Bill Byrnes, Shared Spectrum Co.

17. Maximum Differential Propagation Value Signal level at TV receiver Minimum Signal Strength – “Grade B” (-81 dBm) Received Power (dBm) Min D/U =15 dB Acceptable Interference = Thermal Noise (-96 dBm) 40 dB 25 dB Maximum practical sensitivity improvement due to special detection processing Minimum Detectable Signal (-121 dBm) Signal level at Frequency Agile receiver Maximum differential propagation value = 40 dB Bill Byrnes, Shared Spectrum Co.

18. Simulation of Differential Propagation Scenario – Mid-Atlantic Region Elevation contours TV transmitters Test reception points along a ~ 8 km path Bill Byrnes, Shared Spectrum Co.

19. ~30 dB change in propagation loss over a small distance Signal from TV station A Signal from TV station B Large Change in Propagation Loss over a Short Distance is Rare Bill Byrnes, Shared Spectrum Co.

20. Low Power Transmitters Have a Small Interference Range 1 mW transmit power Maximum interference range of 600 m in obstructed conditions Maximum interference range of 4 km in free-space Noise Free-space propagation Obstructed propagation Bill Byrnes, Shared Spectrum Co.

21. Spectrum Probing Method Frequency Agile monitors 2) Very weak signal doesn’t interfere with primary user Broadcast Receiver 75 km to 200 km spacing 3) Measure Pr of the very weak signal using high processing gain 4) Pt minus Pr is the propagation loss Frequency Agile transceiver 5) Repeat with N nodes to estimate minimum propagation loss into area 1) Transmit (Pt) at a very low power Bill Byrnes, Shared Spectrum Co.

22. Geo-Location Method TV Receiver HAAT (m) PT (kW) Guard Distance Region of Potential Interference TV Transmitter TV Receiver • Position information • GPS, telephone Protected Area Frequency Agile Transceiver • Protected area boundary database information • Telephone, over-the-air, special beacons, Internet, manually entered Beacon TX Bill Byrnes, Shared Spectrum Co.

23. Significant “White Space” Between TV Coverage Areas Grade B 50% and 90% contours Channel 5 and channel 54 Bill Byrnes, Shared Spectrum Co.

24. How Large A Guard Distance? 1 W transmit power Maximum interference range of > 100 km in free-space Noise Maximum interference range of 2 km in obstructed conditions Large guard distances reduce spectrum harvest TV bands: 100 km is too large >> Limit TX power to mW’s Other bands: Max TX power ? Bill Byrnes, Shared Spectrum Co.

25. Multiple, robust spectrum access methods Listen-Before Talk “TDMA” spectrum Broadcast spectrum Geo-location/database FCC should conduct and publish spectrum occupancy measurements Many spectrum holes are large and have long duration FCC should allow experimental interactive operations All access methods including Probe TV and other bands Summary Bill Byrnes, Shared Spectrum Co.