September 2006

Steve Shellhammer, Qualcomm

Slide 1

doc.: IEEE 802.22-06/XXXXr0

Submission

An Evaluation of DTV Pilot Power Detection

IEEE P802.22 Wireless RANs Date: 2006-09-18

Name Company Address Phone email Steve Shellhammer Qualcomm 5775 Morehouse Dr

San Diego, CA 92121 (858) 658-1874 Shellhammer@ieee.org

Rahul Tandra Qualcomm 5775 Morehouse Dr San Diego, CA 92121

(858) 845-1970 rtandra@qualcomm.com

Authors:

Notice: This document has been prepared to assist IEEE 802.22. It is offered as a basis for discussion and is not binding on the contributing individual(s) or organization(s). The material in this document is subject to change in form and content after further study. The contributor(s) reserve(s) the right to add, amend or withdraw material contained herein.

Release: The contributor grants a free, irrevocable license to the IEEE to incorporate material contained in this contribution, and any modifications thereof, in the creation of an IEEE Standards publication; to copyright in the IEEE’s name any IEEE Standards publication even though it may include portions of this contribution; and at the IEEE’s sole discretion to permit others to reproduce in whole or in part the resulting IEEE Standards publication. The contributor also acknowledges and accepts that this contribution may be made public by IEEE 802.22.

Patent Policy and Procedures: The contributor is familiar with the IEEE 802 Patent Policy and Procedures http://standards.ieee.org/guides/bylaws/sb-bylaws.pdf including the statement "IEEE standards may include the known use of patent(s), including patent applications, provided the IEEE receives assurance from the patent holder or applicant with respect to patents essential for compliance with both mandatory and optional portions of the standard." Early disclosure to the Working Group of patent information that might be relevant to the standard is essential to reduce the possibility for delays in the development process and increase the likelihood that the draft publication will be approved for publication. Please notify the Chair Carl R. Stevenson as early as possible, in written or electronic form, if patented technology (or technology under patent application) might be incorporated into a draft standard being developed within the IEEE 802.22 Working Group. If you have questions, contact the IEEE Patent Committee Administrator at patcom@iee.org.>

September 2006

Steve Shellhammer, Qualcomm

Slide 2

doc.: IEEE 802.22-06/XXXXr0

Submission

Introduction

• During the Study Group phase of this project the proposed method for detection of a DTV signal was to detect the power in a narrow band around the pilot location [1].

• This presentation evaluates this technique using the DTV signal files provided by MSTV [2].

September 2006

Steve Shellhammer, Qualcomm

Slide 3

doc.: IEEE 802.22-06/XXXXr0

Submission

Observations About Pilot Power Detection

• The Pilot is a very narrowband feature which occurs is one of several well defined frequencies, which make it a strong feature for detection

• Since the pilot is in a narrow bandwidth it is susceptible to multipath (Rayleigh) fading, which makes detection more difficult

• Since there are multiple pilot locations that makes detection more difficult

• Since this feature is unique to ATSC DTV it can potentially also be used for signal classification

September 2006

Steve Shellhammer, Qualcomm

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Submission

Pilot Locations

• This table is from the Draft [3]

September 2006

Steve Shellhammer, Qualcomm

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Submission

September 2006

Steve Shellhammer, Qualcomm

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Submission

Observations on Pilot Locations

• In [1] it was suggested that a 10 KHz filter be used• However, the range of possible pilot locations span over

59 KHz• In addition the accuracy of the local oscillator (LO)

must be considered when setting the filter bandwidth• Based on all these observations a filter of more than 60

KHz (probably more like 70 KHz) would need to be used.

• None the less, we performed our simulations using only a 10 KHz filter, as proposed in [1]

• If a 70 KHz filter were used the results would be approximately 8.5 dB worse

September 2006

Steve Shellhammer, Qualcomm

Slide 7

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Submission

Detector Summary

• Down convert IF signal to bring the pilot close to DC• Filter with 10 KHz lowpass filter• Reduce sampling rate to 10 KHz• The test statistic is the estimate of the power in this

10 KHz band• Set the detector threshold so that we have a 10% false

alarm rate• Include the effects of noise uncertainty• 30 samples = 3 ms• 60 samples = 6 ms

September 2006

Steve Shellhammer, Qualcomm

Slide 8

doc.: IEEE 802.22-06/XXXXr0

Submission

Expectations for this Detector

• The power in the pilot is 11.3 dB less than the power in the data portion of the signal.– The signal power is 11.3 dB lower

• The noise in 10 KHz is 28 dB less than in 6 MHz– The noise power is 28 dB lower

• The combined effect of these two factors is an increase of approximately 17 dB. That is huge!

• We get flat Rayleigh fading in the 10 KHz band– This is going to have a strong negative effect on the detector– Since this is fixed wireless we cannot just wait around for the

channel to get better – Not too much benefit from time diversity

September 2006

Steve Shellhammer, Qualcomm

Slide 9

doc.: IEEE 802.22-06/XXXXr0

Submission

Strong Pilot

September 2006

Steve Shellhammer, Qualcomm

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Submission

Strong Pilot

September 2006

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Submission

Strong Pilot

September 2006

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Submission

Average Pilot

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Submission

Average Pilot

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Submission

Average Pilot

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Submission

Weak Pilot

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Submission

Weak Pilot

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Submission

Weak Pilot

September 2006

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Submission

Very Weak Pilot

September 2006

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Submission

Very Weak Pilot

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Submission

Very Weak Pilot

September 2006

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Submission

Pilot Outside Filter Bandwidth

September 2006

Steve Shellhammer, Qualcomm

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Submission

Pilot Outside Filter Bandwidth

September 2006

Steve Shellhammer, Qualcomm

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Submission

Pilot Outside Filter Bandwidth

September 2006

Steve Shellhammer, Qualcomm

Slide 24

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Submission

Average over 48 Signal Files

• 48 out of 50 of the files had their pilot within the filter bandwidth

• So we averaged the PMD curves over all these 48 files

• By averaging over all these files we effectively average over the effects of Rayleigh fading

September 2006

Steve Shellhammer, Qualcomm

Slide 25

doc.: IEEE 802.22-06/XXXXr0

Submission

Average over 48 Signal Files

September 2006

Steve Shellhammer, Qualcomm

Slide 26

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Submission

Average over 48 Signal Files

September 2006

Steve Shellhammer, Qualcomm

Slide 27

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Submission

Conclusions

• Even if we do not consider the effects of noise uncertainty the simulation results show that the effects of Rayleigh fading prevent this detector from meeting the -116 dB detection requirement

• In addition the possible pilot locations span about 60 KHz

• If we consider after the cut over date to DTV the span of the pilot locations is reduced to around 20 KHz

September 2006

Steve Shellhammer, Qualcomm

Slide 28

doc.: IEEE 802.22-06/XXXXr0

Submission

1. John Notor, Proposal for Part 15.244 Cognitive Radio Operation in the TV Band, IEEE 802.18-04/30r2, July 2004

2. Advanced Television Standards Committee, ATSC Recommended Practice: Receiver Performance Guidelines, A/74, June 2004

3. IEEE P802.22™/D0.1, Draft Standard for Wireless Regional Area Networks Part 22: Cognitive Wireless RAN Medium Access Control (MAC) and Physical Layer (PHY) specifications: Policies and procedures for operation in the TV Bands, Version 0.1, May 2006

References