1. 1Runcom Technologies Ltd. Submission Eli Sofer, Runcom April 2007 Doc.: IEEE802.22-07/0164r0 Slide 1 Runcom Preamble vs. Phillips Proposed Sequences IEEE P802.22 Wireless RANs Date: 2007-04-04 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 Carl R. StevensonCarl 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. patcom@iee.org

2. 2Runcom Technologies Ltd. Submission Eli Sofer, Runcom April 2007 Doc.: IEEE802.22-07/0164r0 Slide 2 Runcom Preamble vs. Phillips Proposed Sequences

3. 3Runcom Technologies Ltd. Submission Eli Sofer, Runcom April 2007 Doc.: IEEE802.22-07/0164r0 Slide 3 Introduction Preamble sequences have to satisfy the following conditions: 1.Low PAPR 2.The classic PN properties: Which means, that the autocorrelation of each sequence should have one peak value and the cross-correlation of two sequences should be approximately zero.

4. 4Runcom Technologies Ltd. Submission Eli Sofer, Runcom April 2007 Doc.: IEEE802.22-07/0164r0 Slide 4 PAPR Our simulations show, that the PAPR of Phillips sequences is about 0.5 dB worse about then the PAPR of the 802.16. 802.16 PAPR = 4.2 – 4.7 dB Phillips PAPR = 4.74 to 5.07 dB

5. 5Runcom Technologies Ltd. Submission Eli Sofer, Runcom April 2007 Doc.: IEEE802.22-07/0164r0 Slide 5 We have received a set of 54 preamble sequences from Phillips for evaluation. The sequences were made from a single sequence generator with cycle of 511 samples. Many sequences suffer from cross-correlation that is nearly identical to the auto-correlation of one of them. This flaw prohibits the use of the proposed PN sequences as Preambles. Frequency Domain Correlation Properties

6. 6Runcom Technologies Ltd. Submission Eli Sofer, Runcom April 2007 Doc.: IEEE802.22-07/0164r0 Slide 6 Auto-correlation properties ( Phillips sequences ) As we from the figures above, the sequences does NOT satisfy the PN sequence condition on Slide 3.

7. 7Runcom Technologies Ltd. Submission Eli Sofer, Runcom April 2007 Doc.: IEEE802.22-07/0164r0 Slide 7 Auto-correlation properties ( 802.16 ) As we from the figures above, the 802.16 sequences have almost perfect autocorrelation property.

8. 8Runcom Technologies Ltd. Submission Eli Sofer, Runcom April 2007 Doc.: IEEE802.22-07/0164r0 Slide 8 The figure shows the autocorrelation of sequence #1 vs. the cross-correlation with sequences #7. Note that these are almost identical modulo a shift of 2 samples. Cross-correlation vs. Auto-correlation ( Phillips sequences ) Autocorrelation of sequence #1 vs. Cross-correlation between sequences #1 and #7

9. 9Runcom Technologies Ltd. Submission Eli Sofer, Runcom April 2007 Doc.: IEEE802.22-07/0164r0 Slide 9 This figure shows the autocorrelation for 802.16 sequence #1 vs. cross- correlation with sequences #7. Sequence Detection ( 802.16 sequences ) Autocorrelation of sequence #1 vs. Cross-correlation between sequences #1 and #7

10. 10Runcom Technologies Ltd. Submission Eli Sofer, Runcom April 2007 Doc.: IEEE802.22-07/0164r0 Slide 10 Conclusions Our examinations show that the PAPR of the proposed sequences is sufficient. However, the correlation properties exhibit significant flaws. Perhaps the most serious flaw is the auto-correlation/ cross-correlation properties. If used, the above flaw would significantly degrade the performance of the all-important frequency synchronization mechanism at the receiver. We strongly suggest to seek other PN sequences which meet the conditions. The 802.16 sequences seem as promising candidates for use in WRAN.