September 2008 doc.: IEEE 802.22-08/0251r0 Soo-Young Chang, Huawei Technologies Slide 1 Submission NEW CHIP SPREADING SEQUENCES FOR TG1 MULTIPLE ACCESS IEEE P802.22 Wireless RANs Date: 2008-9-4 N am e C om pany A ddress Phone em ail Soo-Y oung Chang H uaw eiTechnologies D avis, CA , U SA 916 278 6568 sychang@ ecs.csus.edu 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 [email protected]. > Soo-Young Chang, Huawei Technologies Slide 1 Submission
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September 2008doc.: IEEE 802.22-08/0251r0 Soo-Young Chang, Huawei TechnologiesSlide 1Submission NEW CHIP SPREADING SEQUENCES FOR TG1 MULTIPLE ACCESS IEEE.
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NEW CHIP SPREADING SEQUENCES FOR TG1 MULTIPLE ACCESSIEEE P802.22 Wireless RANs Date: 2008-9-4
Name Company Address Phone email
Soo-Young Chang Huawei Technologies Davis, CA, USA 916 278 6568 [email protected]
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 [email protected].>
• In D2 (and D4), one chip sequence was introduced for chip spreading, not for multiple access. [1] [2]
• However, with only one chip sequence multiple networks (or PPDs) in an area can not be facilitated.
• The author has introduced 8 orthogonal codewords (or seuences) in D3 to accommodate this multiple access feature. [3]
• In July 2008 meeting, Steve Kuffner [1] claimed these codewords in D3 do not have good correlation characteristics for chip synchronization and less uniform spectral characteristics.
• In this document, a new set of codewords are being introduced to improve these characteristics and meet the requirements.
• The spreading sequence for 802.22.1 D2 was a complex sequence that was chosen based on its correlation properties.
• Sequence = [1-j -1-j 1+j 1-j 1-j 1-j -1+j -1-
j]
• The figure was imported from [1]. It was plotted with average values with two cases of next bits 1 and -1. It means at one moment, the actual correlations may be larger than those shown in this figure.
• Still the value should be 2 for lags of 4 and -4. (any mistake in [1] ?)
Steve Kuffner claimed that these sequences have poor auto/cross-correlation properties, and are only ensured to be orthogonal when properly time aligned. [1]
• A new set of four 8 chip sequences are being introduced where each element is a complex number.– Four sequences were selected so as for correlations to be less
• Take a block of eight chips randomly from the received chip stream. Calculate a correlation of this block with the assigned receiver sequence.
a1 a2 a3 a4 a5 a6 a7 a8
a1 a2 a3 a4 a5 a6 a7 a8
a1 a2 a3 a4 a5 a6 a7 a8
a1 a2 a3 a4 a5 a6 a7 a8
Calculate two correlations by shifting by one chip at one time and by taking inversion and non-inversion for red chips.
Take the smaller correlation value between two values with inversion and non-inversion for the correlation of the shifted block.
For eight shifted sequences including no shift, get correlation values. The chip sequence with highest correlation value is the right one for bit synch.
• For D2, average values are plotted. It means that actual values can be larger than these values.
– For ex., for lag1, correlation value can be 4 with the probability of ½.
• By applying the procedure to calculate correlations of received sequences introduced in this document, less correlations are taken for unsynchronized sequence.
-8 -6 -4 -2 0 2 4 6 80
1
2
3
4
5
6
7
8
lag
|R(k
)|
Autocorrelation values vs chip lag
Only two non-zero correlations for unsynchronized sequences by proposed procedure
• D2 spectral characteristics– From Steve Kuffner’s document [1], the D2 spreading sequence
spreads the energy out relatively uniformly across the chip rate bandwidth.
– This sequence is exactly the same as Sequence 1 of the new sequences proposed in this document. Therefore the spectrum of D2 sequence is the same as that of Sequence 1 of the new sequences.
• Spectral characteristics of new sequences– Spectra of new sequences are plotted using simulations in the
document, the D2 spreading sequence spreads the energy out relatively uniformly across the chip rate bandwidth. [1]
• This sequence is exactly the same as Sequence 1 of the new sequences proposed in this document. Therefore the spectrum of D2 sequence is the same as that of Sequence 1 of the new sequences.
• In this document, a new set of four sequences is introduced and a new procedure to calculate correlations for bit synchronization is proposed.
– A new set of sequences are selected with a criterion of maximum correlation of 5.6 out of 16.
• With these four sequences, up to four PPDs (or networks) can be operated in an area simultaneously.
– This feature should be implemented.• A new procedure to calculate correlations enables us to have smaller
correlations for unsynchronized and unmatched sequences.• The four sequences proposed have almost the same level of correlations
and spectra as D2 (and D4) sequence has:– Auto-correlation: D2: 4/16 max new sequences: 5.6/16 max– Cross-correlation: 8/16 max– Spectra: almost the same spectrum envelope across the chip rate bandwidth