1. doc.: IEEE 802.22-07/0520r1 Submission November 2007 Soo-Young Chang, Huawei TechnologiesSlide 1 New Code for RTS/ANP for Lower Probability of Collision IEEE P802.22 Wireless RANs Date: 2007-11-10 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 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. doc.: IEEE 802.22-07/0520r1 Submission November 2007 Soo-Young Chang, Huawei TechnologiesSlide 2 Abstract In the current TG1 draft, a code is being used for RTS and ACK/NACK codewords. However there can be only 15 codewords applied. Therefore when multiple SPDs select one of them for their RTS codeword, the probability to collide with RTS codewords for other SPDs will be relatively high. In this document, to lower this probability of collision a new code is being introduced for the RTS and ACK/NACK codewords. It improves probability of collision while it lowers processing complexity.

3. doc.: IEEE 802.22-07/0520r1 Submission November 2007 Soo-Young Chang, Huawei TechnologiesSlide 3 CURRENT CODE NPD NACK Go-On

4. doc.: IEEE 802.22-07/0520r1 Submission November 2007 Soo-Young Chang, Huawei TechnologiesSlide 4 NEW CODE DESIGN Cascading two identical 8-bit orthogonal codes Received data: divided into two subcodewords Each subcodeword is compared with 8 8-bit codewords. 8x8=64 codewords realized –Among these codewords, three codewords are assigned to NPD, Go-On, and NACK. Subcodeword 1Subcodeword 2 Received 16 bit RTS/ACK codeword

5. doc.: IEEE 802.22-07/0520r1 Submission November 2007 Soo-Young Chang, Huawei TechnologiesSlide 5 ORTHOGONAL 8 BIT CODE RTS/ANP index r0r1r2r3r4r5r6r7 100000000 201010101 300110011 401100110 500001111 601011010 700111100 801101001

6. doc.: IEEE 802.22-07/0520r1 Submission November 2007 Soo-Young Chang, Huawei TechnologiesSlide 6 NEW CODE FOR 16 BITS RTS/AC K index r0r1r2r3r3 r4r5r5 r6r7 100000000 201010101 300110011 401100110 500001111 601011010 700111100 801101001 RTS/AC K index r8r9r1 0 r1 1 r1 2 r1 3 r1 4 r1 5 100000000 201010101 300110011 401100110 500001111 601011010 700111100 801101001 For subcodeword 1For subcodeword 2

7. doc.: IEEE 802.22-07/0520r1 Submission November 2007 Soo-Young Chang, Huawei TechnologiesSlide 7 ASSIGNMENT OF A CODEWORD TO EACH SPD Method 1 –Assign a codeword to an SPD randomly –Still has a probability of collision Method 2 –Assign a codeword to an SPD corresponding to its subchannel number. –In this method the subchannel number means a subchannel in a TV channel where its lowest subchannel among subchannels it is protecting (or its protected devices cover) if it has multiple subchannels covered by itself. –This method can guarantee that in the next step no collision occurs.

8. doc.: IEEE 802.22-07/0520r1 Submission November 2007 Soo-Young Chang, Huawei TechnologiesSlide 8 ADVANTAGES OVER CURRENT CODE New codeCurrent code Low complexity –a simpler look-up table required: less memory needed :needs 8 8-bit codewords:needs 15 16-bit codewords –Computational complexity :16 8-bit comparisons :15 16-bit comparisons More codeword combinations –64 combinations15 codewords lower prob. of collision:1/62higher prob. of collision:1/12

9. doc.: IEEE 802.22-07/0520r1 Submission November 2007 Soo-Young Chang, Huawei TechnologiesSlide 9 DISADVANTAGE OVER CURRENT CODE New codeCurrent code Less Hamming distance –Slightly lower error control capacity: Hamming distance: 4+4=8 Hamming distance: 8 : error detection: up to 6 bits: up to 7 bits : error correction: up to 2 bits: up to 3 bits This can be interpreted as an E b /N 0 difference. –6/7 and 2/3 error control ratio can be < 0.5 dB E b /N o difference for the same error control capability.

10. doc.: IEEE 802.22-07/0520r1 Submission November 2007 Soo-Young Chang, Huawei TechnologiesSlide 10 CONCLUSIONS In the document, 22-07-0xxxx-01- 0001_Sensing_Beacons_Using_Short_Quiet_Periods, a new code is being proposed for RTS/ACK codewords. With the new code design for RTS/ACK, –lower processing complexity and probability of collision can be achieved with the same length of codewords as that introduced in the 22.1 current draft. –To achieve the same error control capability, the new code needs a little bit higher E b /N o value than the current code by <0.5 dB.

11. doc.: IEEE 802.22-07/0520r1 Submission November 2007 Soo-Young Chang, Huawei TechnologiesSlide 11 References 22-07-0xxxx-01- 0001_Sensing_Beacons_Using_Short_Quiet_Periods

12. doc.: IEEE 802.22-07/0520r1 Submission November 2007 Soo-Young Chang, Huawei TechnologiesSlide 12 Lecture notes in computer science edited by G. Goos

13. doc.: IEEE 802.22-07/0520r1 Submission November 2007 Soo-Young Chang, Huawei TechnologiesSlide 13

14. doc.: IEEE 802.22-07/0520r1 Submission November 2007 Soo-Young Chang, Huawei TechnologiesSlide 14 Tao Jiang lecture note