1. 1 IEEE 802.16m Synchronization Channel IEEE 802.16 Presentation Submission Template (Rev. 9) Document Number: IEEE C802.16m-08/823r3 Date Submitted: 2008-07-09 Source: Sungho Moon, Seunghee Han, Jin Sam Kwak, Young-Hyoun Kwon Voice: +82-31-450-1935 e-mail : {msungho; dondai; samji; wishwill}@lge.comsamji; wishwill}@lge.com LG Electronics LG R&D Complex, 533 Hogye-1dong, Dongan-gu, Anyang, 431-749, Korea Venue: Call for Comments on 16m Preamble Related Documents C80216m-08/634 and C8016m-08/636 Purpose: For discussion in TGm (Preamble Rapporteur Group) Notice: This document does not represent the agreed views of the IEEE 802.16 Working Group or any of its subgroups. It represents only the views of the participants listed in the “Source(s)” field above. It is offered as a basis for discussion. It is not binding on the contributor(s), who 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 802.16. Patent Policy: The contributor is familiar with the IEEE-SA Patent Policy and Procedures: and.http://standards.ieee.org/guides/bylaws/sect6-7.html#6http://standards.ieee.org/guides/opman/sect6.html#6.3 Further information is located at and.http://standards.ieee.org/board/pat/pat-material.htmlhttp://standards.ieee.org/board/pat

2. 2 IEEE 802.16m Synchronization Channel

3. 3 Contents  Synchronization Channel (SCH) Functionalities  General Terms and Relationships  Non-Hierarchical vs. Hierarchical

4. 4 SCH Functionality  Synchronization  Timing synchronization  Symbol, frame, and super-frame  Carrier frequency and frequency offset  Cell Identification and Additional Information  Cell or sector ID distinction  Essential information for BCH decoding should be detected during cell search.  CP information  # of transmit antennas for BCH  Etc.  Channel Estimation  Allow estimation of channels for multiple transmit antennas  Measurement Functions  RSSI measurement  Noise power estimation

5. 5 General Terms and Relationships  Symbol Timing Detection Algorithms and Signal Forms  Hierarchy and Signal Forms  Possible Structures  NH structure: (Non-Hierarchical, Repeated signal form, Auto-correlation based algorithm)  H structure 1 : (Hierarchical, Non-repeated signal form, Cross-correlation based algorithm)  H structure 2 : (Hierarchical, Repeated signal form for P-SCH, Auto-correlation based algorithm)  Hybrid Type  Hierarchical with one symbol Signal Forms Detection algorithm Repeated SignalNon-Repeated Signal Auto-correlation based algorithmWell-MatchedN/A Cross-correlation based algorithm Not recommended due to ambiguous peaks & complexity Well-Matched Signal Forms Hierarchy Repeated SignalNon-Repeated Signal Hierarchical (two symbols) MatchedWell-Matched Non-Hierarchical (one symbol) Well-Matched Not recommended due to complexity

6. 6 Non-Hierarchical Structure  Definition  Only a single type of 16m synchronization symbol which may be in addition to the legacy 16e preamble  No needs of 16e preamble as part of the SCH functionality  Main Features  One OFDM symbol through multiple antennas (CDD, FSTD, or TSTD)  Every other subcarrier : Null  2x repeated signal in time  Auto-correlation based detection algorithm  Sector/cell-common allocation (due to maintain the 2x repeated signal in the cell- edge)  For Example,

7. 7 Hierarchical Structures  Definition  More than one type of SCH symbols exist within a super-frame.  This may or may not use the legacy 16e preamble as one level of hierarchy.  Main Features  The P-SCH can be used for initial acquisition.  Hierarchical structure 1 : Cross-correlation based detection algorithm  Hierarchical structure 2 : Auto-correlation based detection algorithm  The S-SCH can be used for fine synchronization, cell/sector identification (ID), and channel measurements.  The P-SCH can be used as a phase reference for S-SCH detection.

8. 8 Problem of Hierarchical Structure 1  Overhead  Additional resource (secondary sync. channel) compared to the non-hierarchical structure  # of symbols for SCH (16e + 16m) in a super-frame  Total 8 symbols in the legacy-disabled mode  Total 12 symbols in the legacy-support mode without reusing of 16e preamble  Complexity in Timing Detection  Cross-correlation based algorithm  Sharpen peak in the condition of very small frequency offsets  Require separate step only for updating correlation metric every sample  Comparisons (# of multiplications and additions) [1]  Replica-based detection (cross-correlation based)  Auto-correlation based detection  50,000 samples during a radio frame Cross-correlation basedAuto-correlation basedRatio # of complex multiplications51,200,000100,512509 times # of complex additions51,150,000100,511509 times

9. 9 Problem of Hierarchical Structure 2  Overhead  Additional resource (secondary sync. channel) compared to the non- hierarchical structure  # of symbols for SCH (16e + 16m) in a super-frame  Total 8 symbols in the legacy-disabled mode  Total 12 symbols in the legacy-support mode without reusing of 16e preamble  Performance  Double energy should be required for the same performance as non- hierarchical one.  With coherent detections of S-SCH using P-SCH, the performance will be degraded due to  Frequency offsets in practical environments  Composite channel from adjacent cells at cell edge  The only benefit of coherent detection will disappear.

10. 10 Reuse of 16e Preamble in Hierarchical Structures  16e preamble can be used for hierarchical structures:  When P-SCH reuses 16e preamble,  Ambiguity problem in the cell edge  When P-SCH has a non-repeated signal form (H structure 1)  Cross-correlation based detection (complexity)  When P-SCH has a repeated signal form (H structure 2)  Need two symbols in the Greenfield mode = double energy compared to the non-hierarchical structure  No need to reuse 16e preamble for any combinations

11. 11 Problem of Hybrid Structure  Complexity  With non-repeated P-SCH (cross-correlation based algorithm)  Require separate steps only for updating correlation metrics every sample  large complexity  Multiplexing of Data Channel with SCH  Separate processing for multiplexing will be required (e.g. 2 times of 256FFT for SCH and a single 512FFT for data in the 5MHz)  A number of guard subcarriers will be required due to orthogonality destruction.  Performance Degradation in Cell ID Detection  The sequence length will become half in a given amount of information.  it will result in an increase of detection error rate and false alarm rate.  Similar performance degradation to the previous Hierarchical 1 and 2 structures

12. 12 Text Proposal for IEEE802.16m SDD ============ Start of text proposal for C80216m-08/634 ============== [Remove all options and sentences related to "hierarchical structure" throughout the document, and adopt option 1 in Section 11.x.2.1.2.1.1.] =================== End of text proposal ======================

13. 13 References [1] IEEE80216m-08/478r3, Design on the Synchronization Channel for IEEE802.16m.