Results on Downlink Pilot Structures

IEEE 802.16 Presentation Submission Template (Rev. 9) Document Number:

IEEE S802.16m-08/762Date Submitted:

2008-07-16Source:

Havish Koorapaty, Jiann-Ching Guey Voice:Ericsson Inc. E-mail: Havish.Koorapaty@ericsson.com8001 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.

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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

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.

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)

Noise limited QPSK rate ½, VehA, 120 kmph

Noise limited 16 QAM rate ½, VehA, 120 kmph

Noise limited 16 QAM rate ½, VehA, 350 kmph

Interference limited scenario with pilot boostPilots interfere with data only

Interference limited scenario with pilot boostPilots interfere with pilots

Interference limited scenarioPerformance comparison