1. doc.: IEEE 802.22-07/0022r0 Submission January 2007 Wu Yu-Chun, Huawei HisiSlide 1 Enhanced Beacon Sync Frame for the 802.22.1 IEEE P802.22 Wireless RANs Date: 2007-01-08 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 802.22-07/0022r0 Submission January 2007 Wu Yu-Chun, Huawei HisiSlide 2 Abstract An enhanced Beacon Sync Frame scheme for IEEE Std. 802.22.1 is proposed. This new scheme will provide error correction and error detection capability for the Sync Frame. Compared to the previous proposal in [1], the number of parity bits was reduced and Quiet Period information was added so that the WRAN can schedule Quiet Period in advance. We also suggest a sensing method by which, with a 1.6651ms sensing window, the WRAN can sense beacons without affecting its communication.

3. doc.: IEEE 802.22-07/0022r0 Submission January 2007 Wu Yu-Chun, Huawei HisiSlide 3 Content  Enhanced Sync Frame Scheme Proposed  Encoding and Decoding  Simulation Results  Beacon Sensing method of WRAN  Conclusions

4. doc.: IEEE 802.22-07/0022r0 Submission January 2007 Wu Yu-Chun, Huawei HisiSlide 4 Enhanced Sync Frame Scheme Proposed (1/2) The Enhanced Beacon Sync Frame has now 32 bits in total, including 15- bit PN Sequence, 15-bit Information (consisting of 3-bit Quiet Period, 4- bit Index and 8-bit Parity) and 2-bit DTX (Discontinuous Transmission). Sync Frame With Index X Sync Frame With Index X-1 Sync Frame With Index 0 。。。 PSDU Frame Sync Sequence (15 bits) Quiet Period (3 bits) Index (4 bits) Parity (8 bits) Sync Frame Structure Super Frame Structure DTX(2 bits) Figure 1: The Enhanced Beacon Sync Frame structure

5. doc.: IEEE 802.22-07/0022r0 Submission January 2007 Wu Yu-Chun, Huawei HisiSlide 5 Enhanced Sync Frame Scheme Proposed (2/2) Within the Sync Frame, the Quiet Period and Index part need to be decoded successfully with high reliability. Otherwise, the receiver can’t decode the PSDU correctly. So we apply FEC (15, 7) to provide Error Correction and Error Detection capability on the Quiet Period and Index part. Also, for the alignment reason, the Sync Frame should include integral number of bytes. So we add 2 DTX bits at the end of a Sync Frame to make it 32bits or 4 bytes in total. Later, we will see that these 2 DTX bits are also helpful to detect the PN Sequence with a small sensing window size.

6. doc.: IEEE 802.22-07/0022r0 Submission January 2007 Wu Yu-Chun, Huawei HisiSlide 6  The FEC code we select here is a code, which is a (n,k) = (15, 7) linear block code.  In the transmitter side, the encoding is just like adding a CRC. The generator polynomial we are using here is  The 3-bits Quiet Period and 4-bit Index are combined together as a message to be encoded and denoted in a polynomial form as Encoding and Decoding (1/4)

7. doc.: IEEE 802.22-07/0022r0 Submission January 2007 Wu Yu-Chun, Huawei HisiSlide 7  Then The data will be transmitted in the order of where is transmitted first. Encoding and Decoding (2/4)

8. doc.: IEEE 802.22-07/0022r0 Submission January 2007 Wu Yu-Chun, Huawei HisiSlide 8 The Encoding procedure can be implemented as in the following diagram: Encoding and Decoding (3/4) Figure 2: The Encoding Circuit of FEC

9. doc.: IEEE 802.22-07/0022r0 Submission January 2007 Wu Yu-Chun, Huawei HisiSlide 9 … The decoder can be implemented as in the following circuit diagram: Figure 3: The Decoding Circuit of FEC Encoding and Decoding (4/4)

10. doc.: IEEE 802.22-07/0022r0 Submission January 2007 Wu Yu-Chun, Huawei HisiSlide 10 Simulation Results (1/2)  The simulation results of 7-bit message without FEC and 15-bit with FEC(15,7) on the AWGN channel are plotted in the following figure. Figure 4: Simulation Results of Sync Frame

11. doc.: IEEE 802.22-07/0022r0 Submission January 2007 Wu Yu-Chun, Huawei HisiSlide 11 Simulation Results (2/2) From the simulation results, we can see that the gain of the FEC(15,7) over that without FEC is about 4.5dB in SNR sense and 1.5dB in Eb/N0 sense.

12. doc.: IEEE 802.22-07/0022r0 Submission January 2007 Wu Yu-Chun, Huawei HisiSlide 12 Beacon Sensing method of WRAN (1/5) As analyzed in [2], a small sensing window is very important for the WRAN not to affect its communication while sensing. To make the sensing window as small as possible, we propose the use of QPSK modulation. Then the time duration of one Sync Frame is 1.6651 ms (corresponding to 32 bits or 16 QPSK symbols). The time duration of the PN sequence is 0.8325ms, which is half of the total Sync Frame.

13. doc.: IEEE 802.22-07/0022r0 Submission January 2007 Wu Yu-Chun, Huawei HisiSlide 13 Beacon Sensing method of WRAN (2/5) Here we introduce a sensing method based on two properties of the Sync Frame:  Good correlation property of the Fixed PN Sequence.  The 2 bits of DTX (1 QPSK symbol) at the end of each Sync Frame notifies that the Beacon stops its transmission.

14. doc.: IEEE 802.22-07/0022r0 Submission January 2007 Wu Yu-Chun, Huawei HisiSlide 14 Beacon Senseing method of WRAN (3/5) 1) Find the DTX symbol. This can be done in a very simple way by finding a symbol position with the lowest energy. 2)Rearrange the saved data properly as illustrated in Figures 5 and 6 to get a continuous and complete PN Sequence. 3)Calculate the correlation value of the PN Sequence. As illustrated in Figures 5 and 6 in the following slide, suppose we have saved 16 QPSK symbols. Then the sensing procedure is as following:

15. doc.: IEEE 802.22-07/0022r0 Submission January 2007 Wu Yu-Chun, Huawei HisiSlide 15 Beacon Senseing method of WRAN (4/5) 4)Judge whether there is a beacon signal or not: if the lowest energy detected meets a certain criterion (for example, the lowest energy is below 1/5 of the average energy) and the correlation value meets with another criterion (for example, the auto-correlation value is more than 5 times of cross-correlation value), then we judge that there is a Beacon Sync Frame. Otherwise, there is not. 5)If, after Step4, the WRAN judges there is a beacon and knows the start position of the Sync Frame, it can decode the Sync Frame to get the Quiet Period and Index information in the next shot. 6)After getting Quiet Period and Index information, the WRAN can schedule proper Quiet Period to listen to the PSDU of that beacon.

16. doc.: IEEE 802.22-07/0022r0 Submission January 2007 Wu Yu-Chun, Huawei HisiSlide 16 Beacon Senseing method of WRAN (5/5) Figure 5: The data WRAN saved starts in the PN part PN D Saved Data PN Information D (a) Original received data (b) Data after rearrangement Rearranged data PN D Saved Data Information (a) Original received data Information Figure 6: The data WRAN saved starts in the Information part

17. doc.: IEEE 802.22-07/0022r0 Submission January 2007 Wu Yu-Chun, Huawei HisiSlide 17 Conclusions (1/2) From the previous slides, we can see that the Enhanced Sync Frame Scheme has following advantages:  The Enhanced scheme provides error correction capability, which greatly improves the Sync performance (about 4.5dB in SNR sense and 1.5dB in Eb/N0 sense).  The FEC also provides error detection capability. This is very important to ensure that the WRAN does not waste a long Quiet Period to decode the PSDU when it did not get the correct start position of the PSDU.

18. doc.: IEEE 802.22-07/0022r0 Submission January 2007 Wu Yu-Chun, Huawei HisiSlide 18 Conclusions (2/2)  The FEC used here has a very simple encoding algorithm as well as a very simple decoding algorithm. The encoding procedure is just like adding a CRC. Regarding decoding complexity, only three XOR operations, one addition operation, and one comparison operation are needed for each bit.  We also introduce a sensing method by which with the sensing window size of 1.6651ms, the WRAN can sense beacons without interruption of its communications.

19. doc.: IEEE 802.22-07/0022r0 Submission January 2007 Wu Yu-Chun, Huawei HisiSlide 19 References 1. 《 22-06-0226-00-0001_Huawei_Beacon_Sync_Frame_Proposal 》. 2. 《 22-06-0245-05-0000_WRAN_Sensing_Window 》

20. doc.: IEEE 802.22-07/0022r0 Submission January 2007 Wu Yu-Chun, Huawei HisiSlide 20 Thank you! Any comments and questions will be highly appreciated!