1. doc.: IEEE 802.22-06/0107r2 Submission July 2006 Baowei Ji, SamsungSlide 1 Uninterrupted Frame Synchronization and Channel Estimation after a Quiet Period/Frame IEEE P802.22 Wireless RANs Date: 2006-07-14 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 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. doc.: IEEE 802.22-06/0107r2 Submission July 2006 Baowei Ji, SamsungSlide 2 Abstract Samsung raised the issue of the interruption of some system operation (e.g., frame sync., channel est., etc.) due to quiet period/frame. This was echoed by the proposers group, and some message is added in the joint proposal before. We suggest to create a separate section to reflect the contribution. Short Training SequenceLong Training Sequence

3. doc.: IEEE 802.22-06/0107r2 Submission July 2006 Baowei Ji, SamsungSlide 3 DVB vs. 802.11/802.15 vs. 802.16/802.22 DVB is of one-way broadcast. No preamble is used. Subscriber station can acquire and synchronize with the BS through the periodicity of OFDMA CP. 802.11/802.15 are contention-based systems, where long preambles (12 OFDM symbols) are used for one-shot frame detection and channel estimation. 802.16/802.22 are PMP systems using framed-PHY scheme. The periodicity of the preamble is critical for network acquisition and channel estimation.

4. doc.: IEEE 802.22-06/0107r2 Submission July 2006 Baowei Ji, SamsungSlide 4 Impact of Quiet Period/Frame (1/3) Channel Estimation –The more accurate, the better performance. –A typical receiver improves the channel estimation by interpolating, accumulating and/or averaging the preceding and/or succeeding channel estimates of the coherent frames. –A missed preamble interrupts this process, and would reduce the accuracy of channel estimation. Preamble Acc.& Avg. Interpolate Receiving Interpolate Tc

5. doc.: IEEE 802.22-06/0107r2 Submission July 2006 Baowei Ji, SamsungSlide 5 Impact of Quiet Period/Frame (2/3) Frame Synchronization –Frame timing (frame synchronization) is crucial for modem design –One of the key considerations for the design of the frame synchronization scheme: Availability of the periodic preambles –Quiet frame w/o preamble destroys the preamble periodicity. –The updating gap results in larger frame synchronization error residual Preamble

6. doc.: IEEE 802.22-06/0107r2 Submission July 2006 Baowei Ji, SamsungSlide 6 Impact of Quiet Period/Frame (3/3) Use of quiet frames/periods has been proposed for in-band channel sensing. For a typical receiver, the insertion of quiet frames would create gaps in the estimation process of key parameters. –Reduce the accuracy of frame synchronization. –Reduce the accuracy of channel estimation. –Affect the estimation of key parameter statistics.

7. doc.: IEEE 802.22-06/0107r2 Submission July 2006 Baowei Ji, SamsungSlide 7 Section 6.21.3 Quiet Periods and Sensing (page 186 of the Version 67 of the joint proposal) Immediately after the end of a quiet period longer than one frame size, the BS shall transmit a preamble* for the purpose of resynchronization of all CPEs in the cell and for channel estimation (see 8 for further details). * Both the short and long training sequences

8. doc.: IEEE 802.22-06/0107r2 Submission July 2006 Baowei Ji, SamsungSlide 8 Section 8.3.1.2 Frame Preamble (page 228 of the Version 67 of the joint proposal) In addition to the superframe preamble, the use of the short and long preamble* is mandatory immediately after the end of a quiet period whenever the size of this quiet period is longer than one frame size. This implies that after a quiet period longer than one frame size, a new superframe or frame transmission is always initiated**. * Sequences ** Remove the sentence (redundancy/confusing message)

9. doc.: IEEE 802.22-06/0107r2 Submission July 2006 Baowei Ji, SamsungSlide 9 Suggestion: A Separate Section Section 6.21.3 Quiet Periods and Sensing Section 6.21.3.1 Uninterrupted Frame Synchronization and Channel Estimation with Quiet Periods When a quiet frame is opportunistically scheduled (Refer to 6.21.3.3), –The regular preamble (i.e., the long training sequence) shall be sent as well as FCH and MAPs. The associated CPEs can infer from the MAPs the empty spot in the frame for opportunistic channel sensing. When a quiet period of one frame is scheduled and broadcast to the associated CPEs in advance, –The regular preamble (i.e., the long training sequence) shall be sent in the beginning of the quiet period to avoid interrupting the periodicity of the fundamental framed PHY operation. When a quiet period of more than one frame is scheduled and broadcast to the associated CPEs in advance : –The use of the short training sequence, besides the long training sequence (Refer to 8.3.1.2), is mandatory for the first frame immediately after the quiet period for the purpose of resynchronization of all CPEs in the cell and for channel estimation.