1. doc.: IEEE 802.22-11/26r0 SubmissionSlide 1 Comparison of DVB-T Sensing Techniques IEEE P802.22 Wireless RANs Date: 2011-02-14 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 IEEEs name any IEEE Standards publication even though it may include portions of this contribution; and at the IEEEs 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 Chairhttp://standards.ieee.org/guides/bylaws/sb-bylaws.pdf Apurva Mody 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.apurva.mody@ieee.orgpatcom@iee.org M. Azizur Rahman, NICT February, 2011

2. doc.: IEEE 802.22-11/26r0 SubmissionSlide 2 Abstract This contribution compares three techniques of DVB-T signal sensing. This is submitted as a supporting document to 802.22- 11-15r0. This document addresses the comments on 802.22-11- 15r0 in Feb 2, 2011, 8 PM ET Systems teleconference (the minutes are listed in 802.22-11-16r0). –The main technical comment was from Apurva Mody on the applicability of Combined Feature and Energy Detection Technique

3. doc.: IEEE 802.22-11/26r0 SubmissionSlide 3 Simulation Setup DVB-T signal uses OFDM. Here, simple OFDM signal is simulated –Random data sequence, Pilot in place as 2K mode of DVB-T –Pilot SCs that are 10% in number of all SC and 2.5 dB boosted. This makes it containing 15% of the total energy. SNR= -15 dB 2K FFT size, 1/8 CP Programs are given at the end Note: The results of 802.22-11-15r0 uses samples DVB-T data from signal generator.

4. doc.: IEEE 802.22-11/26r0 Submission Pilot (Time Domain) Correlation Technique Blue: abs. (corr. out) of pilot with signal plus noise Red: abs (corr.) of pilot with noise Synchronization at samples 256, 1*2304, 2*2304, 3*2304 Reference: Pilot SCs that are 10% in number of all SC and 2.5 dB boosted. This makes it containing 18% of the energy By setting threshold for any false alarm, it may not be possible to sense reliably if synchronization is not achieved. The reason behind it is Pilot only carries a fraction of total energy. Slide 4 samples Normalized decision stat./threshold

5. doc.: IEEE 802.22-11/26r0 Submission Energy Detection Technique Slide 5 Blue: sum (square) of signal plus noise Red: sum (square) of noise By setting threshold for any false alarm, it may not possible to sense reliably samples Normalized decision stat./threshold

6. doc.: IEEE 802.22-11/26r0 Submission Combined Feature and Energy Detection Technique Slide 6 samples Normalized decision stat./threshold Blue: sum (abs. (multiply)) of pilot with signal plus noise Red: sum (abs. (multiply)) of pilot with noise Synchronization at samples 256, 1*2304, 2*2304, 3*2304 Reference: Pilot SCs that are 10% in number of all SC and 2.5 dB boosted. This makes it containing 15% of the energy The decision statistic is higher than potential threshold By carefully setting threshold for low false alarm, it is possible to sense reliably

7. doc.: IEEE 802.22-11/26r0 Submission Matlab Program (1/3) %PROGRAM BY. AZIZ RAHMAN @NICT TO COMPARE THREE METHODS OF SENSING DVB-T as in 802.22-11-14r0. clear all %OFDM FFTsize=2048; %2K mode bit=[+1,-1]; stream = randsrc(1,FFTsize,bit); %random data % stream2 = randsrc(1,FFTsize,bit); %random data % stream3 = randsrc(1,FFTsize,bit); %random data % stream4 = randsrc(1,FFTsize,bit); %random data % ContiPilotPosition=[54 87 141 201 255 279 282 333 450 483 525 531 618 714 759 765 873 918 939 942 969 1050 1101 1107 1110 1137 1146 1206 1269 1323 1377 1491 1683]; OtherPilotPosition= 0:12:1705; PilotPositions=[ContiPilotPosition OtherPilotPosition]; %Total 33+143=176; %2.5 dB UP means 1.78 times higher power %Pilot Reference reference=zeros(1,FFTsize); for i=1:length(ContiPilotPosition)+length(OtherPilotPosition) reference(PilotPositions(i)+171)=sqrt(1.78)*stream(PilotPositions(i)+171); stream2(PilotPositions(i)+171)=sqrt(1.78)*stream(PilotPositions(i)+171); stream3(PilotPositions(i)+171)=sqrt(1.78)*stream(PilotPositions(i)+171); stream4(PilotPositions(i)+171)=sqrt(1.78)*stream(PilotPositions(i)+171); End stream(FFTsize/2)=0; stream2(FFTsize/2)=0;stream3(FFTsize/2)=0;stream(FFTsize/2)=0;stream4(FFTsize/2)=0; Slide 7

8. doc.: IEEE 802.22-11/26r0 Submission Matlab Program (2/3) x=ifft(reference); %PILOT in FD x=[x(FFTsize-FFTsize/8+1:FFTsize) x]; % Cyclic Prefix 1/8 y=ifft(stream); %DATA+PILOT in FD y=[y(FFTsize-FFTsize/8+1:FFTsize) y];% Cyclic Prefix 1/8 %SIGNAL % It consists of 10% OFDM SC as PILOT. In power PILOT 15% and DATA 85% power y2=ifft(stream2); %DATA+PILOT in FD y2=[y2(FFTsize-FFTsize/8+1:FFTsize) y2];% Cyclic Prefix 1/8 y3=ifft(stream3); %DATA+PILOT in FD y3=[y3(FFTsize-FFTsize/8+1:FFTsize) y3];% Cyclic Prefix 1/8 y4=ifft(stream4); %DATA+PILOT in FD y4=[y4(FFTsize-FFTsize/8+1:FFTsize) y4];% Cyclic Prefix 1/8 s=[y y2 y3 y4]; %consider datasequence sn=awgn(s,-15,'measured'); %ADD AWGN %SNR=-15 dB %======CORRELATION WITH PILOT====== zn=xcorr(x,sn); %DECEISON STAT. n=sn-s; %NOISE th=xcorr(x,n); % FOR THRESHOLD figure(1) plot(abs(zn(100:400)),'b') hold on; grid on; plot(abs(th(100:400)),'r) Slide 8

9. doc.: IEEE 802.22-11/26r0 Submission Matlab Program (3/3) %======COMBINED FEATURE AND ENERGY DETECTION METHOD BY C. SONG @NICT====== for i = 1 : length(s)-length(x) z2n(i)=sum(abs(sn(i:i+length(x)-1).*x)); %DECEISON STAT. th2(i)=sum(abs(n(i:i+length(x)-1).*x)); % FOR THRESHOLD end figure(2) plot(z2n) grid on; hold on; plot(th2,'r') %======ENERGY DETECTION====== figure(3) plot(abs(sn).^2) %DECEISON STAT. grid on hold on plot(abs(n).^2,'r') % FOR THRESHOLD Slide 9

10. doc.: IEEE 802.22-11/26r0 SubmissionSlide 10 Conclusion This contribution demonstrated the better performance of the Combined Feature and Energy Detection Technique of DVB-T sensing as proposed in 802.22-11- 15r0.

11. doc.: IEEE 802.22-11/26r0 SubmissionSlide 11 References 802.22-11-15r0 802.22-11-16r0