Frame structure supporting multiple CP sizes Document Number: IEEE S802.16m-08/436, Frame structure supporting multiple CP sizes Date Submitted: 2008-5-11 Source: Hongwei YANG, Dong LI, Liyu CAI, Keying WU, Xiaolong ZHU Voice: +86 21 58541240 Ext 7796 E-mail: Hongwei.yang@alcatel-sbell.com.cn *<http://standards.ieee.org/faqs/affiliationFAQ.html> Venue: IEEE 802.16m-08/016r1 Call for Contributions on Project 802.16mSystem Description Document (SDD) Target topic: Comments to IEEE 802.16m-08/003r1 Base Contribution: IEEE C802.16m-08/436r2 Purpose: For 802.16m discussion, adoption into the SDD and eventual adoption for standardization 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: <http://standards.ieee.org/guides/bylaws/sect6-7.html#6> and <http://standards.ieee.org/guides/opman/sect6.html#6.3>. Further information is located at <http://standards.ieee.org/board/pat/pat-material.html> and <http://standards.ieee.org/board/pat >.

Introduction In the latest SDD (IEEE 802.16m-08/003r1), two CP sizes are defined 1/8 and 1/16 ratio. But there are some big issues: Not sufficient for supporting various environments and MBS service. For 1/16 CP, the number of OFDM symbols (51) within one frame cannot be distributed into 8 subframes evenly, resulting in unfixed subframe duration. Unfixed subframe duration leads to the fact that the CP size can only change frame by frame, which disables Co-existence of unicast and MBS service within one carrier Legacy support with 1/8 CP size In this contribution, we proposed the frame structure with fixed subframe duration for supporting multiple CP sizes.

Proposed frame structure supporting multiple CP sizes Normal CP: 11.43us, 128 samples Short CP: 3.21us, 36 samples Long CP: 18.93us, 212 samples Half OFDM used for long and short CP to fit the fixed subframe duration

Numerology for the proposed frame structure Nominal Channel Bandwidth (MHz) 5 7 8.75 10 20 Over-sampling Factor 28/25 8/7 Sampling Frequency (MHz) 5.6 8 11.2 22.4 FFT Size 512 1024 2048 Sub-Carrier Spacing(kHz) 10.94 7.81 9.77 Tu ((s) 91.4 128 102.4 Cyclic Prefix (CP) Number of samples per each OFDM symbol per sub-frame[1] Idle Time(s) 1 2 3 4 6 Normal CP 128/1024[2] 128/1024 N/A 62.86 Short CP 36/1024 40/512 Long CP 214/1024 212/1024 212/512 Note: 1) These values are for sampling frequency of 10MHz BW and can be extended straightforwardly to BWs of 5MHz and 20MHz. 2) A/B: A denotes the CP length and B denotes the useful OFDM symbol length, both in samples.

Summary of the proposed solution Advantages and notes of the frame structure supporting multiple CP sizes with fixed subframe duration Advantage: CP size can change subframe by subframe, that is, multiple CP sizes can be flexibly configured within one frame, which enables within one frame multiple CP sizes adaptation to co-existence of unicast and MBS services and legacy support with 1/8 CP size Notes: the utilization of half OFDM symbol doesn’t increase the complexity apparently (in details, only simple half symbol extraction at transmitter and half symbol duplication at the receiver are required). Suggest to adopt the text proposal in base contributions.