1. Results on Downlink Pilot Structures IEEE 802.16 Presentation Submission Template (Rev. 9) Document Number: IEEE S802.16m-08/762 Date Submitted: 2008-07-16 Source: Havish Koorapaty, Jiann-Ching GueyVoice: Ericsson Inc.E-mail:Havish.Koorapaty@ericsson.com 8001 Development Drive RTP, NC 27709 * http://standards.ieee.org/faqs/affiliationFAQ.html Venue: IEEE 802.16 Session #56, Denver, US Base Contribution: IEEE C802.16m-08/762r1 Purpose: Presentation of results on Downlink Pilot Structures in support of changes to the 802.16m proposed in IEEE C802.16m-08/763. 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. Introduction Simulation results have been submitted by a number of companies The performance differences between different patterns are generally very small (excluding a few patterns that are not robust against high speeds) The only significant difference appears in the interference limited scenario when pilot boosting is used Here pilot patterns that allow non-overlapping pilots in different cells, outperform fixed patterns. The reason is that inter-cell pilot-to-pilot interference is avoided

3. Proposal Thus, a pattern allowing non-overlapping pilots in different cells should be selected The pattern should have many non-overlapping realizations to allow a high pilot pattern re-use factor, and thus minimizing inter cell pilot-to-pilot interference The pilot pattern in C802.16m-08/763 support the largest number of non-overlapping realizations, and in the four antenna case it is the only pattern proposed that allow pilot pattern re-use. The pilot pattern in C802.16m-08/763 is therefore proposed to be selected for 16m.

4. Simulation assumptions Antenna configuration –Single transmit and receive antenna Channel estimation –MMSE estimator with knowledge of the noise covariance Block size –18 subcarriers by 6 symbols Encoding –Turbocoding Pilots –6 pilots per block –Position varied according to pattern Scenarios –Interference Limited Environment (Two equal strength interferers) –Noise Limited Environment (AWGN)

5. Noise limited QPSK rate ½, VehA, 120 kmph

6. Noise limited 16 QAM rate ½, VehA, 120 kmph

7. Noise limited 16 QAM rate ½, VehA, 350 kmph

8. Interference limited scenario with pilot boost Pilots interfere with data only

9. Interference limited scenario with pilot boost Pilots interfere with pilots

10. Interference limited scenario Performance comparison