1. A New Preamble Structure for Robust Timing/Frequency Synchronization in IEEE 802.16m System Document Number: S802.16m-08/320 Date Submitted: May 05, 2008 Source: Pei-Kai Liao (pk.liao@mediatek.com), Chih-Yuan Lin, Ciou-Ping Wu and Paul Cheng (paul.cheng@mediatek.com)pk.liao@mediatek.compaul.cheng@mediatek.com MediaTek Inc. No. 1 Dusing Rd. 1 Hsinchu Science Park Hsinchu City 300 Taiwan; Yih-Guang Jan (yihjan@ee.tku.edu) and Yang-Han Lee (yhlee@ee.tku.edu.tw)yihjan@ee.tku.eduyhlee@ee.tku.edu.tw Tamkang University; Shiann-Tsong Sheu (stsheu@ce.ncu.edu.tw)stsheu@ce.ncu.edu.tw National Central Univeristy Venue: Macao, China Base Contribution: IEEE C802.16m-08/320r1 Purpose: Propose to be discussed and adopted by TGm for the use in Project 802.16m SDD. 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 S802.16m-08/320

2. Introduction Motivation –Problems in preamble for 802.16e system Poor synchronization performance for cell-edge/segment-edge users Sensitive to Doppler spread due to high mobility –Preamble structure to resolve problems with low overhead is desirable Purpose and Summary –Propose to be discussed and included in 802.16m SDD –A new preamble structure is proposed for robust synchronization

3. Design Considerations Low overhead Improved synchronization performance for cell/segment-edge users Robustness to Doppler spread induced by high mobility –Preamble structure which is robust to large Doppler spread is desired so as to keep MS synchronized with BS to maintain network connection under high-mobility environment (up to 350 km/hr) Fast temporal-domain preamble detection –Fast temporal domain preamble detection without decoding preamble code sequence can largely decrease the number of failure trials and thus speed up the synchronization process

4. Temporal-Domain Illustration of Proposed Preamble Structure

5. Frequency-Domain Illustration of Proposed Preamble Structure

6. Detail Design of Proposed Preamble Structure One OFDM symbol is used for new preamble –Total length: N + CP length The OFDM symbol is divided into two parts: –First preamble Along the time domain, N/2 samples only, no CP is applied Along the frequency domain, N/2 sub-carriers over the whole bandwidth DC sub-carrier is a null tone –Second preamble Along the time domain, (N/2 + CP length) samples, CP is applied Along the frequency domain, N/2 sub-carriers over the whole bandwidth DC sub-carrier is a null tone

7. Detail Design of Proposed Preamble Structure First Preamble: –Interleaved by K 1 over sub-carriers –The number of K 1 is limited by the following condition K 1 ≦ N/(2*CP_length); K 1 ≦ 4, if CP_length=N/8 –The first duplicate in time domain functions as a CP Second Preamble: –Can be interleaved by K 2 or not interleaved –The number of K 2 depends on K 1 and frequency reuse factor

8. Arrangement of Preamble Code Sequences Separate structure –Code sequences applied to first and second preamble are two independent codewords –Code sequence used in first preamble are the same in all cells For amplifier gain training, coarse synchronization and synchronization parameters estimation –Code sequences used in second preamble are different between segments For fine synchronization, channel estimation and segment identification Joint structure –Code sequences applied to first and second preamble are two partitions of one codeword –The combined codeword from two partitions is used for amplifier gain training, synchronization, channel estimation and segment identification

9. Properties of Proposed Preamble Structure Synchronization performance enhancement for users at the cell edge due to the utilization of macro diversity Preamble collision avoidance between segments can be achieved by FDM/CDM The proposed structure can be applied to any existing code sequence such as PRBS, Zadoff-Chu sequence and QCCC Robust to Doppler spread induced by high mobility The same overhead as that in IEEE 802.16e system Periodical structure along the time domain enables fast temporal-domain preamble detection FFT/IFFT with size N can be reused for preamble decoding