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doc.: IEEE 802.22-07/0206r1 Submission April 2007 Baowei Ji, SamsungSlide 1 Improper to Limit Long Quiet Period at the end of a Superframe IEEE P802.22 Wireless RANs Date: 2007-04-26 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 firstname.lastname@example.org@iee.org >
doc.: IEEE 802.22-07/0206r1 Submission April 2007 Baowei Ji, SamsungSlide 2 Abstract Long quiet period (a.k.a., inter-frame sensing) is used for fine inband channel sensing. There are many concerns for limiting the inter-frame sensing only at the end of a superframe.
doc.: IEEE 802.22-07/0206r1 Submission April 2007 Baowei Ji, SamsungSlide 3 Consensus so far It is good to have two-stage sensing: intra-frame and inter-frame. Intra-frame SHOULD be less than one frame, so that at least the frame preamble is transmitted for all CPEs to maintain synchronization to the BS. A robust preamble (i.e., superframe preamble) SHALL be used after inter-frame sensing, so that all CPEs can immediately re-synchronize to the BS after this long quiet period.
doc.: IEEE 802.22-07/0206r1 Submission April 2007 Baowei Ji, SamsungSlide 4 Discussion on the Location of Inter-Frame Sensing If inter-frame sensing is always put at the end of a superframe, the preamble following the long quiet period is, naturally, the superframe preamble. But, there are many concerns on making such kind of constraints in a standard: –It is premature to set this hard limit while there are many things uncertain about channel sensing. –At least, it cannot schedule inter-frame sensing TIMELY. –At least, it cannot support more than one inter-frame sensing period in a superframe. –It could hurt the goal of avoiding synchronized long quiet periods during out-of-band sensing.
doc.: IEEE 802.22-07/0206r1 Submission April 2007 Baowei Ji, SamsungSlide 5 The Hard Constraint cannot Schedule Inter-frame Sensing TIMELY Suppose intra-frame sensing in the 1 st frame of a superframe reports something suspicious, which implies inter-frame sensing is needed. Suppose the inter-frame sensing requires 2 frames. Given the hard constrain, the earliest time to schedule the inter-frame sensing is 13 frames later. Why not schedule the long quiet period earlier?
doc.: IEEE 802.22-07/0206r1 Submission April 2007 Baowei Ji, SamsungSlide 6 The Hard Constraint cannot Support more than One Inter-frame Sensing Period in a Superframe Imagine, some CPEs report something in the 1 st frame which triggers an inter-frame sensing. Then, some CPEs report something in 10 th frame which should triggers another inter-frame sensing.
doc.: IEEE 802.22-07/0206r1 Submission April 2007 Baowei Ji, SamsungSlide 7 The Hard Constraint could Result in Undesirable Synchronized Quiet Periods for Out-of-band Sensing. Given the hard constraint, any long quiet period must be at the end of a superframe. There are 12 superframes in 2 seconds. A BS using channel N may have to be quiet at least 3 times for sensing channels N+1, N, N-1. Neighbor cells have high probability of scheduling long quiet period at the same time, even when they are using different channels. In practice, some CPEs should be scheduled to do out-of-band sensing, while some CPEs are doing inband sensing. But, during those long quiet periods, out-of-band sensing cannot detect neighbors.
doc.: IEEE 802.22-07/0206r1 Submission April 2007 Baowei Ji, SamsungSlide 8 Two Paths Path I: Problematic Hard Constraint –There SHALL be at most one inter-frame sensing in a superframe. Inter-frame sensing SHALL be scheduled at the end of a superframe. –Redesign inter-frame sensing, either frame offset or duration of quiet period is not necessary. or Path II: Flexible but support re-synch –A superframe preamble SHALL be used after inter-frame sensing, so that all CPEs can immediately re-synchronize to the BS after this long quiet period.
doc.: IEEE 802.22-07/0206r1 Submission April 2007 Baowei Ji, SamsungSlide 9 Suggestions Use Path II, i.e., without the hard constraint. Use the same superframe preamble. A CPE ignores the extra superframe preamble.
doc.: IEEE 802.22-07/0206r1 Submission April 2007 Baowei Ji, SamsungSlide 10 No Impact to Normal Operations For CPEs already associated with the BS, the extra superframe preamble is designed for them to re- synchronize to the BS after inter-frame sensing. For a CPE just powered on and being looking for a BS, it should ignore the extra preamble and keeps on looking for the BS. The reasons are as follows. –During initial network acquisition, it is normal for a CPE to encounter an un-decodable SCH, and keep on searching. –We talked about to find a way for the CPE to differentiate SCH and FCH. But, it is not necessary because, anyway, the CPE has to use SCH for initial network acquisition. –It does not help to use new PN sequences either, again because the CPE has to use SCH for initial network acquisition. –Path II resolves comments 224, 93 and 522 all together.
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