An ATSC Detector using Peak Combining

An ATSC Detector using Peak Combining
March 2007 doc.: IEEE yy/xxxxr0 March 2007 An ATSC Detector using Peak Combining IEEE P Wireless RANs Date: Authors: Notice: This document has been prepared to assist IEEE 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 Patent Policy and Procedures: The contributor is familiar with the IEEE 802 Patent Policy and Procedures 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 Working Group. If you have questions, contact the IEEE Patent Committee Administrator at > Steve Shellhammer, Qualcomm Steve Shellhammer, Qualcomm

New Material Since January
March 2007 doc.: IEEE yy/xxxxr0 March 2007 New Material Since January Added a 6 MHz Digital IF filter to remove adjacent channel signals Added simulation results for a clean laboratory signal This revision has a sorted list of signals from best to worst Add spectrum plots of some of the worst and best signals Added simulations of laboratory signal with PFA = 0.001 Steve Shellhammer, Qualcomm Steve Shellhammer, Qualcomm

March 2007 doc.: IEEE yy/xxxxr0 March 2007 Abstract This presentation introduces an ATSC detector based on combining peaks from the output of a correlator for the ATSC Data Field Sync pattern A special case of this approach is taking the maximum of the correlator output. This will be evaluated first before considering the more general case Probability of misdetection curves are given for the 12 preferred ATSC signal files The results of these curves are averaged to get an average probability of misdetection curve Finally, the results are averaged over the shadow fading probability density function Steve Shellhammer, Qualcomm Steve Shellhammer, Qualcomm

March 2007 doc.: IEEE yy/xxxxr0 March 2007 Background In [1] we evaluated a technique in the working document for ATSC signal detection We suggested a simpler method which actually gave better performance In [1] we only evaluated these methods using one ATSC signal file In this presentation we evaluate the simple method using the 12 preferred signal files Steve Shellhammer, Qualcomm Steve Shellhammer, Qualcomm

A single VSB Data Segment
March 2007 doc.: IEEE yy/xxxxr0 March 2007 ATSC Frame Structure A single VSB Data Segment The Data Field SYNC Steve Shellhammer, Qualcomm Steve Shellhammer, Qualcomm

March 2007 doc.: IEEE yy/xxxxr0 March 2007 Background Convert the receive signal to baseband and then correlate the received baseband signal with the ATSC Field Sync pattern The correlator output is observed for one ATSC Data Field (24.2 ms) Use the simple test statistic, Steve Shellhammer, Qualcomm Steve Shellhammer, Qualcomm

March 2007 doc.: IEEE yy/xxxxr0 March 2007 Peak Combining We will like to be able to combine the peaks from multiple ATSC Data Fields A simple approach is to effectively increase the correlator to cover multiple ATSC Data Fields However, there are two issues with approach Due to clock jitter the peaks shift slightly in each Data Field Due to multipath the polarity of the peak can reverse Also, there are sometime a few peaks due to multipath Can we come up with a method of combining peaks from multiple ATSC Data Fields? Steve Shellhammer, Qualcomm Steve Shellhammer, Qualcomm

March 2007 doc.: IEEE yy/xxxxr0 March 2007 Peak Combining To address the issue of polarity reversal we start by taking the absolute value of the correlator output The next step is to select N possible candidate peaks from each ATSC Data Field. These are the N largest peaks. We generate a table of peaks from each ATSC Data Field. A peak is represented by, A peak index (the sample index starting from the beginning of that ATSC data field) A peak magnitude Steve Shellhammer, Qualcomm Steve Shellhammer, Qualcomm

Peak Combining – Correlator Output
March 2007 doc.: IEEE yy/xxxxr0 March 2007 Peak Combining – Correlator Output Steve Shellhammer, Qualcomm Steve Shellhammer, Qualcomm

Peak Combining – Absolute Value of Correlator Output
March 2007 doc.: IEEE yy/xxxxr0 March 2007 Peak Combining – Absolute Value of Correlator Output Steve Shellhammer, Qualcomm Steve Shellhammer, Qualcomm

Peak Combining – Peak List
March 2007 doc.: IEEE yy/xxxxr0 March 2007 Peak Combining – Peak List Peak Index Peak Magnitude i1 p1 i2 p2 i3 p3 i4 p4 i5 p5 i6 p6 Steve Shellhammer, Qualcomm Steve Shellhammer, Qualcomm

Peak Combining – Overlay Peaks from Multiple ATSC Data Fields
March 2007 doc.: IEEE yy/xxxxr0 March 2007 Peak Combining – Overlay Peaks from Multiple ATSC Data Fields Steve Shellhammer, Qualcomm Steve Shellhammer, Qualcomm

Combine peaks whose index fall with within a window of size M
March 2007 doc.: IEEE yy/xxxxr0 March 2007 Combine peaks whose index fall with within a window of size M Steve Shellhammer, Qualcomm Steve Shellhammer, Qualcomm

March 2007 doc.: IEEE yy/xxxxr0 March 2007 Final Test Statistic Select the maximum magnitude of the final peak list as the test statistic For the case when we only process for one ATSC Data Field this is the same as the maximum of the absolute value of the correlator output Steve Shellhammer, Qualcomm Steve Shellhammer, Qualcomm

March 2007 doc.: IEEE yy/xxxxr0 March 2007 Observations The actual peaks (the ones due to a correlation with the ATSC Data Field) tend to combine since they are within the window size The false peaks (those due to noise) tend to not combine very often since they tend to occur at different times within the field We do need to increase the detector threshold a bit since observing over a longer time and peak combining does result in a small increase in the test statistic due to noise only Steve Shellhammer, Qualcomm Steve Shellhammer, Qualcomm

Digital IF Filter Signal filtered with a Digital IF Filter
March 2007 doc.: IEEE yy/xxxxr0 March 2007 Digital IF Filter Signal filtered with a Digital IF Filter 256 coefficient FIR filter 6 MHz bandwidth Steve Shellhammer, Qualcomm Steve Shellhammer, Qualcomm

Digital IF Filter March 2007 March 2007 doc.: IEEE 802.22-yy/xxxxr0
Steve Shellhammer, Qualcomm Steve Shellhammer, Qualcomm

Average Probability of Misdetection
March 2007 doc.: IEEE yy/xxxxr0 March 2007 Average Probability of Misdetection Simulated the peak combining technique for all twelve of the preferred ATSC signal files Simulations for three detectors One ATSC Data Field Four ATSC Data Fields Sixteen ATSC Data Fields Show the results for all twelve signal files Added a curve for a Clean Laboratory Signal Thick Black Line on multi-signal plots Averaged the results for all twelve signal files to obtain the average probability of misdetection Steve Shellhammer, Qualcomm Steve Shellhammer, Qualcomm

Clean Laboratory Signal
March 2007 doc.: IEEE yy/xxxxr0 March 2007 Clean Laboratory Signal Steve Shellhammer, Qualcomm Steve Shellhammer, Qualcomm

PMD Curves – 1 ATSC Data Field
March 2007 doc.: IEEE yy/xxxxr0 March 2007 PMD Curves – 1 ATSC Data Field Steve Shellhammer, Qualcomm Steve Shellhammer, Qualcomm

Sorted Signals – Best to Worst
March 2007 doc.: IEEE yy/xxxxr0 March 2007 Sorted Signals – Best to Worst WAS_32_48_ _OPT_short WAS_86_48_ _REF_short WAS_51_35_ _REF_short WAS_68_36_ _REF_short WAS_47_48_ _OPT_short WAS_49_39_ _OPT_short WAS_06_34_ _REF_short WAS_49_34_ _OPT_short WAS_311_35_ _REF_short WAS_3_27_ _REF_short WAS_311_48_ _REF_short WAS_311_36_ _REF_short Steve Shellhammer, Qualcomm Steve Shellhammer, Qualcomm

Spectrum of Best Signal
March 2007 doc.: IEEE yy/xxxxr0 March 2007 Spectrum of Best Signal Steve Shellhammer, Qualcomm Steve Shellhammer, Qualcomm

Spectrum of Worst Signal
March 2007 doc.: IEEE yy/xxxxr0 March 2007 Spectrum of Worst Signal Steve Shellhammer, Qualcomm Steve Shellhammer, Qualcomm

PMD Curves – 4 ATSC Data Fields
March 2007 doc.: IEEE yy/xxxxr0 March 2007 PMD Curves – 4 ATSC Data Fields Steve Shellhammer, Qualcomm Steve Shellhammer, Qualcomm

March 2007 doc.: IEEE yy/xxxxr0 March 2007 Sorted Signals – Best to Worst WAS_68_36_ _REF_short WAS_86_48_ _REF_short WAS_32_48_ _OPT_short WAS_49_39_ _OPT_short WAS_51_35_ _REF_short WAS_06_34_ _REF_short WAS_311_35_ _REF_short WAS_47_48_ _OPT_short WAS_311_48_ _REF_short WAS_49_34_ _OPT_short WAS_3_27_ _REF_short WAS_311_36_ _REF_short Steve Shellhammer, Qualcomm Steve Shellhammer, Qualcomm

Spectrum of Best Signal
March 2007 doc.: IEEE yy/xxxxr0 March 2007 Spectrum of Best Signal Steve Shellhammer, Qualcomm Steve Shellhammer, Qualcomm

Spectrum of Worst Signal
March 2007 doc.: IEEE yy/xxxxr0 March 2007 Spectrum of Worst Signal Steve Shellhammer, Qualcomm Steve Shellhammer, Qualcomm

PMD Curves – 16 ATSC Data Fields
March 2007 doc.: IEEE yy/xxxxr0 March 2007 PMD Curves – 16 ATSC Data Fields Steve Shellhammer, Qualcomm Steve Shellhammer, Qualcomm

March 2007 doc.: IEEE yy/xxxxr0 March 2007 Sorted Signals – Best to Worst WAS_86_48_ _REF_short WAS_68_36_ _REF_short WAS_47_48_ _OPT_short WAS_51_35_ _REF_short WAS_49_34_ _OPT_short WAS_49_39_ _OPT_short WAS_06_34_ _REF_short WAS_32_48_ _OPT_short WAS_3_27_ _REF_short WAS_311_48_ _REF_short WAS_311_35_ _REF_short WAS_311_36_ _REF_short Steve Shellhammer, Qualcomm Steve Shellhammer, Qualcomm

PMD Averaged over all 12 ATSC Data Files
March 2007 doc.: IEEE yy/xxxxr0 March 2007 PMD Averaged over all 12 ATSC Data Files Steve Shellhammer, Qualcomm Steve Shellhammer, Qualcomm

Average over Shadow Fading
March 2007 doc.: IEEE yy/xxxxr0 March 2007 Average over Shadow Fading We can now average over the PDF of the shadow fading to obtain the average probability of misdetection at the edge of the keep-out region Mean signal power = dBm [2] Standard deviation of the signal power = 5.5 dB [2] Noise Power = dBm [2] Combining we get Average SNR = 1.3 dB Standard deviation of SNR = 5.5 dB Steve Shellhammer, Qualcomm Steve Shellhammer, Qualcomm

Shadow Fading PDF March 2007 March 2007 doc.: IEEE 802.22-yy/xxxxr0
Steve Shellhammer, Qualcomm Steve Shellhammer, Qualcomm

Number of ATSC Data Fields
March 2007 doc.: IEEE yy/xxxxr0 March 2007 Average PMD We can average the PMD functions by numerically integrating over the shadow fading PDF Number of ATSC Data Fields PMD 1 0.032 4 0.014 16 0.005 Steve Shellhammer, Qualcomm Steve Shellhammer, Qualcomm

Modified Threshold for Lower PFA
March 2007 Modified Threshold for Lower PFA Modified the threshold to get a probability of false alarm of 0.001 Did this only for the case of one ATSC Data Field Ran simulation only for the laboratory signal Probability of misdetection curve approximately one dB worse – See figure Steve Shellhammer, Qualcomm

Laboratory Signal – Different PFA
March 2007 Laboratory Signal – Different PFA Steve Shellhammer, Qualcomm

Different Detection Threshold
March 2007 Different Detection Threshold The detection threshold was increased by 15% PFA decreased from 0.1 to 0.001 PMD increased by approximately 1 dB An addition to seeing the effect of lower PFA we also get an indication of the sensitivity of this sensing technique to small changes in the detector threshold Steve Shellhammer, Qualcomm

March 2007 doc.: IEEE yy/xxxxr0 March 2007 Conclusions A new technique for detection of ATSC signals was proposed utilizing the unique ATSC Data Field Sync pattern The results give reasonable results but do not yet reach the sensing requirements for ATSC Averaging over the ATSC signal files and the shadow fading gives the average probability of misdetection at the edge of the keep-out region, which is a excellent summary of a detectors performance The time required for detection using the ATSC Data Sync is in the tens or hundreds of ms since the pattern occurs every 24.2 ms Steve Shellhammer, Qualcomm Steve Shellhammer, Qualcomm

March 2007 doc.: IEEE yy/xxxxr0 March 2007 References Suhas Mathur and Steve Shellhammer, An Evaluation of the PN Sequence based detection of DTV Signals in the Draft, IEEE /0189r0, September 2006 Steve Shellhammer, Victor Tawil, Gerald Chouinard, Max Muterspaugh and Monisha Ghosh, Spectrum Sensing Simulation Model, IEEE /0028r10, August 2006 Steve Shellhammer, Qualcomm Steve Shellhammer, Qualcomm

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