1Runcom Technologies Ltd. Submission Eli Sofer, Runcom March 2007 Doc.: IEEE802.22-07/0202r0 Slide 1 Runcom Preamble vs. Phillips Proposed Sequences IEEE

1Runcom Technologies Ltd.Submission Eli Sofer, Runcom

March 2007 Doc.: IEEE802.22-07/0202r0

Slide 1

Runcom Preamble vs. Phillips Proposed Sequences

IEEE P802.22 Wireless RANs Date: 2007-04-18

Name Company Address Phone email Eli Sofer Runcom 2 Hachoma St., 75655

Rishon Lezion, Israel +972 544 997 996 [email protected]

Doron Ezri Runcom 2, Hachoma St. 75655 Rishon Lezion, Israel

+972 3 942 8899 [email protected]

Vadim Neder Runcom 2, Hachoma St. 75655 +972 3 942 8843 [email protected]

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 [email protected].


March 2007 Doc.: IEEE802.22-07/0202r0

Slide 2

Runcom Preamble vs. Phillips Proposed Sequences


March 2007 Doc.: IEEE802.22-07/0202r0

Slide 3

Introduction

• Preamble sequences have to satisfy the following conditions:1. Low PAPR

2. The classic PN properties:

n allfor ,0)(

),()(

nR

nnR

xy

xx

Which means, that the autocorrelation of each sequence should have one peak value and the cross-correlation of two sequences should be approximately zero.


March 2007 Doc.: IEEE802.22-07/0202r0

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


March 2007 Doc.: IEEE802.22-07/0202r0

Slide 5

Frequency shift degradation influence on time domain correlation (no frequency shift)

Sequence without shift


March 2007 Doc.: IEEE802.22-07/0202r0

Slide 6

Frequency shift degradation influence on time domain correlation (1 bin shift)

Sequence with one bin shift


March 2007 Doc.: IEEE802.22-07/0202r0

Slide 7

Frequency shift degradation influence on time domain correlation (10 bin shift)

Not detectable at all


March 2007 Doc.: IEEE802.22-07/0202r0

Slide 8

1 Bin shifted sequence vs. sequence without shift

5 dB worse than the one without frequency shift.


March 2007 Doc.: IEEE802.22-07/0202r0

Slide 9

1 Bin shifted sequence vs. sequence without shift


March 2007 Doc.: IEEE802.22-07/0202r0

Slide 10

• We have received a set of 114 preamble sequences from Phillips for evaluation.

• The 57 of 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.

Frequency Domain Correlation Properties


March 2007 Doc.: IEEE802.22-07/0202r0

Slide 11

Auto-correlation properties (Phillips sequences)

As we from the figures above, the sequences does NOT satisfy the PN sequence condition on Slide 3.


March 2007 Doc.: IEEE802.22-07/0202r0

Slide 12

Auto-correlation properties (WiMax sequences)

As we from the figures above, the 802.16 sequences have almost perfect autocorrelation property.


March 2007 Doc.: IEEE802.22-07/0202r0

Slide 13

The figure shows the autocorrelation of sequence #24 vs. the cross-correlation with sequences #6. Note that these are almost identical modulo a shift of 2 samples.

Cross-correlation vs. Auto-correlation (Phillips sequences)

Autocorrelation of sequence #24 vs .Cross-correlation between sequences #24 and #6


March 2007 Doc.: IEEE802.22-07/0202r0

Slide 14

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


March 2007 Doc.: IEEE802.22-07/0202r0

Slide 15

Remarks• The time correlation for PN detection, as it has been proposed in

Phillips's presentation, requires huge complex multiplications and memory usage. Frequency correlation, for our opinion, is far better than proposed one. Therefore, frequency correlation properties should satisfy the condition on Slide 3 for all lags and not for the limited part of the sequence.

• We don’t agree with assumption, that all synchronizations are made in super-frame and the frame is perfectly synchronized. This issue has to be studied more carefully.

• There is possibility, that from frame to frame the symbol could go out of synchronization. In this case, the time correlation will severely degrade. (Our simulations shows 5-23.8 dB degradation for 1-10 bins shift accordingly)

• We strongly recommend to seek other PN sequences which meet the conditions.


March 2007 Doc.: IEEE802.22-07/0202r0

Slide 16

Conclusions

• Our examinations show that the PAPR of the proposed is not better than WiMax’s.

• The correlation properties exhibit significant flaws. Perhaps the most serious flaw is the auto-correlation/ cross-correlation properties.

• We recommend following actions: Seek other PN sequences which meet the conditions. Perform better simulations with consideration of all possible

scenarios.

Documents

1Runcom Technologies Ltd. Submission Eli Sofer, Runcom March 2007 Doc.: IEEE802.22-07/0202r0 Slide 1 Runcom Preamble vs. Phillips Proposed Sequences IEEE