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Doc.: IEEE 802.18-04-0004-00-000 Submission January 2004 Bill Byrnes, Shared Spectrum Co. Frequency Agile Spectrum Access Technologies This Presentation.

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Presentation on theme: "Doc.: IEEE 802.18-04-0004-00-000 Submission January 2004 Bill Byrnes, Shared Spectrum Co. Frequency Agile Spectrum Access Technologies This Presentation."— Presentation transcript:

1 doc.: IEEE Submission January 2004 Bill Byrnes, Shared Spectrum Co. Frequency Agile Spectrum Access Technologies This Presentation was originally made to an FCC Workshop on Cognitive Radios May 19, 2003 by one of Bills colleagues. (Bill was kind enough to share this information with SG1 in the interest of promoting discussion.)

2 doc.: IEEE Submission January 2004 Bill Byrnes, Shared Spectrum Co. Agenda Requirements Spectrum occupancy characteristics –Significant amount of low hanging fruit Spectrum access methods –Listen-Before Talk TDMA spectrum Broadcast spectrum –Probe –Geo-location/database

3 doc.: IEEE Submission January 2004 Bill Byrnes, Shared Spectrum Co. Frequency Agile Radio Requirements 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

4 doc.: IEEE Submission January 2004 Bill Byrnes, Shared Spectrum Co. Spectrum Occupancy Is Low 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 Spectrums measurements indicate –Many bands have no detectable occupancy –Some bands have low occupancy –Some bands have high occupancy Note 1: FCC Spectrum Policy Task Force Report, page 3

5 doc.: IEEE Submission January 2004 Bill Byrnes, Shared Spectrum Co. Typical Spectrum Occupancy Measurement No signals Medium and short duration signals FCC should conduct and publish spectrum occupancy measurements to identify low occupancy bands

6 doc.: IEEE Submission January 2004 Bill Byrnes, Shared Spectrum Co. Initially Harvest the Low Hanging Fruit 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

7 doc.: IEEE Submission January 2004 Bill Byrnes, Shared Spectrum Co. Agenda Requirements Spectrum occupancy characteristics –Significant amount of low hanging fruit Spectrum access methods –Listen-Before Talk TDMA spectrum Broadcast spectrum –Probe –Geo-location/database

8 doc.: IEEE Submission January 2004 Bill Byrnes, Shared Spectrum Co. Adaptive, Receive-Only Spectrum Access Method P max TX = 10*log10(k * T * B) + P Primary – P measured - 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

9 doc.: IEEE Submission January 2004 Bill Byrnes, Shared Spectrum Co. Primary Transceivers Frequency Agile Transceivers Interference/Connectivity Limit Exclusion Zone Frequency Agile Coverage Morphs To Fit Primary Users Hidden-node problem overcome by each Frequency Agile transceiver listening to all Primary users within range

10 doc.: IEEE Submission January 2004 Bill Byrnes, Shared Spectrum Co. High Sensitivity Receiver Performance

11 doc.: IEEE Submission January 2004 Bill Byrnes, Shared Spectrum Co. 10 ground vehicles spread over 25 km moving at 25 km/hr 10 stationary ground vehicles spread over 25 km West Virginia location 3 m antenna height Simulation Example Primary users are stationary XG users are mobile Omni-directional antennas 420 MHz signal frequency

12 doc.: IEEE Submission January 2004 Bill Byrnes, Shared Spectrum Co. Link closure Interference Longley-Rice Model 420 MHz Free space loss Actual loss Propagation Losses

13 doc.: IEEE Submission January 2004 Bill Byrnes, Shared Spectrum Co. Frequency Agile network reduces TX power automatically Network needs switch to another frequency at low TX power levels XG TX Power (dBm) Target interference level of –100 dBm Primary Interference Level (dBm) TX Power and Interference

14 doc.: IEEE Submission January 2004 Bill Byrnes, Shared Spectrum Co. TV Receiver Frequency Agile Transceiver TV Transmitter Region of Potential Interference P T (kW) HAAT (m) Listen-Only Method in the Broadcast Bands TV Receiver L1 L2 Differential propagation loss = L1-L2

15 doc.: IEEE Submission January 2004 Bill Byrnes, Shared Spectrum Co. Transmit Power Rule P max TX = Po if Primary signal is not detected = Transmission prohibited if Primary signal is detected where, P max TX = Frequency Agile transmitter power level, in dBm Po = specified power value, in dBm

16 doc.: IEEE Submission January 2004 Bill Byrnes, Shared Spectrum Co. TV Receiver with Grade B reception Frequency Agile Transceiver TV Transmitter Terrain Blockage Building Blockage LOS Location LOS to Frequency Agile Transceiver Multi-Path Effects Minimal Interference Joint probability of three conditions –Agile Receiver doesnt detect TV signal –Primary user receives TV signal –D/U < 15 dB

17 doc.: IEEE Submission January 2004 Bill Byrnes, Shared Spectrum Co. Minimum Detectable Signal (-121 dBm) Minimum Signal Strength – Grade B (-81 dBm) Min D/U =15 dB Acceptable Interference = Thermal Noise (-96 dBm) Received Power (dBm) 40 dB 25 dB Maximum Differential Propagation Value Maximum differential propagation value = 40 dB Maximum practical sensitivity improvement due to special detection processing Signal level at TV receiver Signal level at Frequency Agile receiver

18 doc.: IEEE Submission January 2004 Bill Byrnes, Shared Spectrum Co. Simulation of Differential Propagation Test reception points along a ~ 8 km path Scenario – Mid-Atlantic Region Elevation contours TV transmitters

19 doc.: IEEE Submission January 2004 Bill Byrnes, Shared Spectrum Co. Large Change in Propagation Loss over a Short Distance is Rare Signal from TV station A Signal from TV station B ~30 dB change in propagation loss over a small distance

20 doc.: IEEE Submission January 2004 Bill Byrnes, Shared Spectrum Co. Low Power Transmitters Have a Small Interference Range Noise Obstructed propagation Free-space propagation Maximum interference range of 4 km in free- space Maximum interference range of 600 m in obstructed conditions 1 mW transmit power

21 doc.: IEEE Submission January 2004 Bill Byrnes, Shared Spectrum Co. Spectrum Probing Method 75 km to 200 km spacing Frequency Agile transceiver Broadcast Receiver 1) Transmit (Pt) at a very low power 3) Measure Pr of the very weak signal using high processing gain 2) Very weak signal doesnt interfere with primary user 4) Pt minus Pr is the propagation loss 5) Repeat with N nodes to estimate minimum propagation loss into area Frequency Agile monitors

22 doc.: IEEE Submission January 2004 Bill Byrnes, Shared Spectrum Co. Geo-Location Method TV Receiver Frequency Agile Transceiver TV Transmitter Region of Potential Interference P T (kW) HAAT (m) TV Receiver Protected Area Position information GPS, telephone Beacon TX Protected area boundary database information Telephone, over-the-air, special beacons, Internet, manually entered Guard Distance

23 doc.: IEEE Submission January 2004 Bill Byrnes, Shared Spectrum Co. Significant White Space Between TV Coverage Areas Grade B 50% and 90% contours Channel 5 and channel 54

24 doc.: IEEE Submission January 2004 Bill Byrnes, Shared Spectrum Co. How Large A Guard Distance? Noise Maximum interference range of > 100 km in free-space Maximum interference range of 2 km in obstructed conditions 1 W transmit power Large guard distances reduce spectrum harvest TV bands: 100 km is too large >> Limit TX power to mWs Other bands: Max TX power ?

25 doc.: IEEE Submission January 2004 Bill Byrnes, Shared Spectrum Co. Summary 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


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