GI and P hase I mpairments - PowerPoint Presentation

Slide1

GI and Phase Impairments Impact on Open-Loop SU-MIMO

Date: 2016-11-04

Slide 1

Authors:

Introduction

In [1], 11ay has agreed to have multiple options of GI

In [4], simulation results suggested GI=32 symbols was sufficient for up to MCS 12 in a NLOS cubicle scenario. During the September meeting, there were suggestions to further investigate the impacts of phase noise impairments with a shorter GI.

This contribution investigates the use of shorter GI in specific scenarios.

CFO and/or phase noise with realistic channel estimationPerformance results show that in certain scenarios the use of a shorter GI is justified.

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2

PPDU Format in 802.11ayCurrent EDMG PPDU format for SC PHY[1]:EDMG preamble part introduces extra overhead

Even though multi data stream transmissions can be applied to data part, EDMG transmission may not be always be as efficient as legacy DMG transmission. Overhead reduction is desirable for EDMG PPDU

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3

Guard IntervalIn 802.11ad, SC data blocks (448 symbols ) are separated by guard intervals (64 symbols).

The 64 GI symbols are modulated symbols from a Golay sequence. The usage of GI:GI is a time period to mitigate inter-block interference GI functions

as a cyclic prefix which allows the use of frequency domain equalizer (FDE) at

the receiverGI is a periodic known sequence to assist with AGC and phase trackingHowever, GI is extra overhead for data transmission. Is 64 GI always necessary?In this contribution,

a different GI size is evaluated using link level simulation.We focus on the impact from the phase-related impairments and how GI length impacts the effectiveness of mitigation mechanisms.

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4

64

448 symbols

64

448 symbols

64

448 symbols

64

Simulation AssumptionsBased on 11ad SC PHY Spatial stream parser:

MCS index is the same for all streams per PPDU, and a single CRC is used per PPDU2 spatial streams, configuration 4 in [2]MMSE receiver with FDE

realistic channel estimation at

receiver based on the agreed EDMG CEF [1]Enterprise cubicle scenario in 11ay/ad channel model [2]STAs are randomly placed

in the cubicle 1 in the center of the CR, 0.9m above the floorAP is positioned at x=2.8, y=6, z=2.9m on the ceiling

Detailed assumptions can be found in the appendix

PSDU size is 8192 bytes

b1

b2

b3

b4

b5

b6

b1

b3

b5

b2

b4

b6

Encoder Output Bits

Stream 1

Stream 2

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Phase Noise Model & CFOPhase noise modelAs in [5]

All rx antennas share the same noise with

PSD(0) =

-

90

dBc

/Hz

Pole frequency

f

p

= 1 MHz

I

ndependent

white noise with

PSD

=

-

130

dBc

/Hz for each

rx

antenna

CFO is assumed to be

13.675 ppm at the receiver, shared by all antennas

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6

Source: [5]

Phase correction

Equalized GI from previous block k-1 and current block k are compared to GI to acquire

and

Equalized data symbol j at block

k

is

corrected

by

,

N

= 512 –

Same phase correction method is used for both residual CFO and phase noise mitigation

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7

PER performance (MCS12) Slide 8

CFO error-onlyPHN error-only

PER performance (MCS12)-cont’dSlide 9Phase noise has

large impactsTracking mechanism improves performance to some degree, but not sufficient in NLOS channel with a small GIShorter GI length has almost no impact on CFO correction

CFO+PHN

errors

PER performance (MCS9) Slide 10

CFO error-onlyPHN error-only

PER performance (MCS9)-cont’dSlide 11

Phase noise has small impact regardless of GI length, or tracking Shorter GI length has almost no impact on CFO correction

CFO+PHN

errors

PER performance (MCS5) Slide 12

CFO error-onlyPHN error-only

PER performance (MCS5)-cont’dSlide 13

Phase noise has almost no impact regardless of GI length, or tracking Shorter GI length has almost no impact on CFO correction

CFO+PHN

errors

Slide 14Conclusions

In [4], GI overhead analysis shows ~7% of gains of GI=32 over GI=64

Phase noise has small impact on BPSK/QPSK MCSs regardless of GI length and with or without correction

Phase noise has impact on MCS12 or higher order modulations at least in a NLOS channel with a small GI

GI=32 has similar performance as GI=64 up to MCS9(QPSK)

Straw PollDo you agree to add the following block format in 11ay SFD:(32 GI,480 data) symbols per SC block for a 2.16GHz channel is an option for SC PHY in QPSK/BPSK MCSSlide

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Slide 16References

Carlos Cordeiro, “Specification Framework for TGay”, IEEE 802.11-15/01358r6

A.

Maltsev, et al, “Channel models for

ieee 802 11ay”, IEEE doc. 11-15/1150r7 R.

Maslennikov

,

et al

,

“

Implementation of 60 GHz WLAN Channel Model

,

”

IEEE doc.

11-10/0854r3.

L. Sun

et al

, “

GI Overhead/Performance Impact on Open-Loop SU-MIMO

”

IEEE doc. 11-16/1172r1.

K. Zeng et al, “Considerations on Phase Noise Model for 802.11ay ”

IEEE doc. 11-16/0390r1

AppendixSlide 17

Channel parametersFor channel with LOS components [3], TX/RX analog beamforming

for both polarizations of PAA#i are based on the LOS direction between TX PAA#i ↔ RX PAA#i

For channel without LOS componentsBeam forming based on the

AoD/AoA of strongest signal path between TX PAA#i ↔ RX PAA#i

Channel bandwidth 2.64 GHz, center frequency 60.48 GHzEach PAA has 2 elementsDistance between antenna elements 0.0025mDistance between center of PAAs 10cm

For AP-STA scenario, STA is placed at a plane 2m below AP in the cubicle 1. Random rotation around z-axis between STA/AP

.

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