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Further Study on Non-linear Precoding with Guaranteed Gain over Linear Precoding

Document Number:IEEE S802.16m-08-925

Date Submitted:15th Sept 2008

Source: Tsuguhide Aoki, Yong Sun (Toshiba) E-mail: tsuguhide.aoki@toshiba.co.jp, sun@toshiba-trel.com Laurent Marc de Courville, Fred Vook 　　 (Motorola)E-mail: marc.de.courville@motorola.com, fred.vook@motorola.com Ron Porat 　　 (Nextwave)E-mail: RPorat@nextwave.com Isamu Yoshii, Takaaki Kishigami (Panasonic)E-mail: yoshii.isamu@jp.panasonic.com, kishigami.takaaki@jp.panasonic.com*<http://standards.ieee.org/faqs/affiliationFAQ.html>

Venue:Kobe, Japan

Base Contribution:C80216m-08_925.doc

Purpose:Enabling non-linear predocing in SDD document.

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Non linear precoding (NLP)

• We’ve already submitted contributions on LNP, which gives a significant gain over linear precoding.– [4] IEEE C802.16m-08/842r1, – [5] IEEE C802.16m-08/366, – [6] IEEE C802.16m-08/205r2, – [7] IEEE C802.16m-08/058r1,

• We therefore show our further study on NLP with simulation results which is fully much the EMD.

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MU-MIMO precoding is similar to MIMO detection

• MIMO detection– Linear detection

• ZF and MMSE• Suffer from noise

enhancement– Non-linear detection

• Ordered successive interference

• ML (Sphere, Lattice reduction

• MU-MIMO precoding– Linear precoding

• ZF and MMSE• Suffer from power

penalty– Non-linear precoding

• Tomlinson-Harashima Precoding (THP)

• Vector Precoding.

Non-linear precoding has advantageous like non-linear detection on MIMO decoding

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Link-level simulation parametersParameters Values

Bandwidth 10MHz

FFT size 1024

Carrier Frequency 2.5GHz

Subframe structure 16m

Channel Model SCME

Radio environment Urban Micro

Mobile speed 0km/h

Linear precoding schemes ZF, MMSE

Non-linear precoding schemes

Tomlinson-Harashima Precoding (ZF, MMSE)Vector Precoding (ZF, MMSE)

CQI feedback frequency, error, and delay

Assume perfect CSI

Antenna configuration 4x4

BS antenna spacing 10

Receiver algorithm Single antenna and 2 antenna-MMSE

Channelization Localized

Resource allocation size 3RB per user

Channel Coding 16e CTC

Modulation QPSK

Code rate 1/2

Channel Estimation Perfect channel estimation

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Frame Error Rate performance

• Significant gain can be achieved in EMD environment

• The simple THP with MMSE gives almost the same performance of VP.

s

n

Normalized SNR=

;transmit power, ;noise powers n

5 10 15 20 25 3010- 3

10- 2

10- 1

100

Normalized SNR

FER

SCME, QPSK 4x4 CTC(R=1/ 2) 10MHz, 3RU per user, MS has 2 antenna

ZFTHP(ZF)VP(ZF)MMSETHP(MMSE)VP(MMSE)

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NLP has no complexity problem

• THP– Need QR or cholesky decomposition to get up

per triangle matrix.

• VP– Need channel inversion and search algorithm

to search the optimum transmit sequence

• THP is fair complexity compared with SVD based linear precoding

• VP is higher complexity, however, but it is vender dependent.

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NLP is not affected by the scheduling

• Linear precoding could have gain by choose semi-orthogonal users through user scheduling.

• However, the gain is not significant because these users don’t always require connections or transmissions.

• Moreover, the user scheduling bring system complexity.

• NLP is not affected by the scheduling or user allocation.

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NLP is more robust

• The simulation results (842r1) show that NLP is robust for CSI errors at Tx

• Simulation parameters– SCME urban micro channel model @ 2.5GHz, 10

MHz bandwidth 10MHz (FFT size is 1024), 3kmph– Packet composed of 10 PUSC subchannels

• 2 frequency subchannels and 5 time slots– R=1/2 Conv. Code (o133, o171)– 10 OFDM symbol delay between UL CSI estimatio

n and DL, 2D MMSE channel estimator– Pilot pattern: 16e PUSC– 4TX(BS), 4 1RX(MS) served– Normalized energy at TX(BS): not per user(MS)

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Summary

• Non-linear precoding provides high performance gain as we showed in further study.

• SDD should support non-linear precoding.

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Text proposal

• 11.8.2.2.1 Precoding technique

• Non-linear precoding is FFS supported.

• In the non-linear precoding, the value shows the processed transmit signal to reduce the transmit power. The receiver may need Modulo operation.

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