1wimax air interface measurements

WiMAX Air Interface Measurements©2007 Rohde & Schwarz

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WiMAX Air Interface Measurements

Heinz MELLEIN, R&STechnology Management Systems & [email protected]


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List of content

� Description of OFDMA signals

� WiMAX Transmitter� Adaptive Modulation� Time and frequency domain power

� WiMAX Receiver� PER, BLER, BER etc.

� WiMAX operational measurements� Ranging� RSSI and CQI

� RF certification measurements


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c+9

c+8

c+7

c+6

c+5

c+4

c+2

c+1

c

k+8k+7k+6k+5k+4k+3k+2k+1k

OFDM(A) signal description

Numberof sub

channels

Number of OFDMsymbols

Dataregion“Burst”

symboloffset

sub channeloffset

DL PUSC SLOT:Minimum possible data unit:2 symbols x 1 subchannel= 48 symbols= 96 Bits (QPSK)= 192 Bits (16QAM)= 288 Bits (64QAM)

symbolindex

subchannel index

Reminder: 1 subchannel = 24 not necessarily adjacent frequency carriers


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Symbol 1

Symbol 2

OFDM signal analysis

Symbol 1e.g. DL OFDM Preamble

Symbol 2e.g. DL OFDM data


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90°

cq(t)

FIR

Phasenoise

Clock rate(jitter)

Orthogonality

Compression

Compression

LOfeedthrough

h(t)

h(t)

Frequency error

cI(t)

Amplification IAmplification Q

Factors Affecting Modulation Quality


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Adaptive Modulation

1/√2 1-1 1/√10

3/√10

I

Q

QPSK

BPSK

Factors 1/√2 (QPSK) resp. 1/√10 (16-QAM) to maintain constant total transmit power.Factor 1/√42 for optional 64-QAM.

16-QAM

64-QAM


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Adaptive Modulation

QPSK

16-QAM

64-QAM

BPSK


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Quadraturecomponent

Idealsymbol point Error

vector Measuredsymbol point

Phaseerror

In phasecomponent

Iref

Qref

Refere

nce

Vecto

r

Error vectorshifted to origin

Phase oferror vector

Measured

vectorAmplitude (magnitude)error

Errorvectormagnitude

Definition of Modulation Errors


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S/N = 20 dB S/N = 30 dB


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Modulation Symbol Power

},Re{ QPSKdata

},Im{ QPSKdata

1

21

21

−},Re{ BPSKpreamble

},Im{ BPSKpreamble

24

24

−

},Re{ BPSKpilot

},Im{ BPSKpilot

11−},Re{ BPSKpilot

},Im{ BPSKpilot

34

34

−

−⋅= kwpilot

212}Re{

−⋅⋅= kwBPSKpreamble

2124},Re{

−⋅= kwpilot

21

38}Re{

−⋅= kwQPSKdata

212},Re{

−⋅= kwQPSKdata

212},Im{ 0}Im{ =preamble

0}Im{ =pilot0}Im{ =pilot

wk = {0,1}k = carrier index

DL pilotBoost 2.5 dB

PreambleBoost 9 dB


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Time domain power ≠ frequency domain power !

∑=subcarrier

subcarrierFDsymbolTD PP ,,

preambleFDpreambleFDWiBropreambleTD

preambleFDFFT

usedpreambleTD

PdBPP

PNNP

,,,,

,,

7.5)1024284log(10

)log(10

+−=+=

+=Example:Preamble powerProfile 1A („Wibro“)


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Frequency domain power aspects

dBP

dBPdBP

P

PilotsData

Pilots

Data

PP

PilotsData

PilotsData

19,0)7

10106log(10

85.166.0

)7

10106log(10

185,0066,0

&

1010

&

−=+⋅

=

=−=

+⋅=

−

Example:Data carrier powervs. Pilot carrier power

Pilot Boostfactor


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Time domain power aspects

)11010log(10

1010Pr

++⋅

=N

NPeambleZone PP

Subframe

Subframe

Zone with N symbolsTim

e do

mai

npo

wer

time

TD PowerZone

TD PowerPreamble

TD power subframe


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OFDM specific: Spectral flatness


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Time

Am

plitu

de

1.00e-07

1.00e-06

1.00e-05

1.00e-04

1.00e-03

1.00e-02

1.00e-01

1.00e+00

+ 10 dB + 20 dB

Prob

a bili

ty

Power above Average

� Only values above mean are considered.

� Probability of peaks above mean value.

� High Peak values appear less frequently.

Crest factor ≈ 15 dB

Power Amplifier Design: Crest Factor


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WiMAX receiver performance

Sensitivity (AWGN, Fading)Selectivity (interferer)

Sensitivity (AWGN, Fading)Selectivity (interferer)

SNRCIR

BERBLERPER

PingER

BER: Bit Error RateBLER: Block Error RatePER: Packet Error RatePingER: Ping Error Rate

AWGN: Additive White Gaussian NoiseSNR: Signal to Noise Ratio

CIR: Carrier to Interference Ratio


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WiMAX receiver measurement methods

Paket Error Rate(PER)

Block Error Rate(BLER)

Bit Error Rate(BER)

ConvergenceLayer

MAC LayerARQ Process

ChannelCodec

ConvergenceLayer

MAC LayerARQ Process

ChannelCodec

„Ping“ Error Rate

PHY LayerHARQ Process

PHY LayerHARQ Process

ICMP/IP Layer ICMP/IP Layer


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Receiver Sensitivity Evaluation

( )

( )

RMHz

FNNSNRdBmR

dBdBRSNRFNNK

HzdBmR

impLossNFRSNRFNNkTR

S

FFT

usedRXSS

RXSFFT

usedSS

RXSFFT

usedSS

log10log10log10101

58log10log10log10)290(@174

log10log10log10

−

+

++−=

++−++

+−=

++−+

+=

k = Boltzmann constant factor (1.3806·10-23 J/K)Nused = Number of occupied subcarriersNFFT = FFT size (e.g. 1024)FS = Sampling FrequencySNRRX = Modulation & Coding specific reference SNRR = Repetition factor {1,2,4,6}NF = Noise Figure: 8 dB as defined by IEEE 802.16e-2005impLoss = Implementation Loss: 5 dB as defined by IEEE 802.16e-2005


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Example: Preamble Sensitivity

BPSKRXSS

S

FFT

used

S

FFT

usedRXSS

SNRdBmdBdBSNRdBmRMHzF

RNN

RMHz

FNNSNRdBmR

+−=−+−+−===

==

−

+

++−=

6,960106,510110

11024284

log10log10log10101

SNRBPSK

BER


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ARQ and HARQ


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Ranging procedureBROADCAST: FP, UCD, DCD, DL-MAP, UL-MAP

RNG-RSPRNG-REQ BASIC MANAGEMENT

Description of downlink and uplink

Ranging to determine power, frequency, timing

RNG-REQCDMA code

RNG-RSPPower offset

Frequency offsetTiming offset

Ranging typesInitial Ranging (IR)Periodic RangingHandoff Ranging


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Ranging Region


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Ranging parametersBROADCAST: FP, UCD, DCD, DL-MAP, UL-MAP

DCDBS_EIRP

EIRxPIR,maxUCD

Backoff windowRanging codes

Power steps…

UL-MAPRangingregion

allocation

RSSEIRPBSEIRxPP IRMAXIRTX −+= _max,__


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Ranging channel

41

subc

hann

el =

6 ti

les

= 24

sub

carri

ers

144

Bits

repr

esen

ting

the

Ran

ging

Cod

e X


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Ranging opportunities


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Initial ranging power

RSSEIRPBSEIRxPP IRMAXIRTX −+= _max,__


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Received Signal Strength Indication� Estimates of mean and standard deviation of RSSI required from MSS by BS� No demodulation required: Measurement in time domain (index k) only� However, for BS related measurements preamble demodulation is required!� Method of estimation is vendor specific (e.g. selection of ADC resolution etc.)� Range -123 dBm (0x00) .. -40 dBm (0x53) in steps of 1 dB� Absolute accuracy requirement: ± 4 dB, Relative accuracy requirement: ± 2 dB� Reporting towards BS using REP_RSP message

REP_RSP = Report Response Message (SS � BS))])[ˆ(][ˆlog(|5][ˆ

0,])0[(]1[ˆ)1(0,])0[(

][ˆ

])[ˆlog(10][ˆ

0],[]1[ˆ)1(0],0[

][ˆ

22,

22

22

,

kkxk

kRkxkR

kx

kk

kkRkkR

k

RSSIRSSIdBmRSSI

avgRSSIavg

RSSI

RSSIdBmRSSI

avgRSSIavgRSSI

µσ

αα

µµ

αµαµ

−=

>+−−

==

=

>+−−=

=Mean Value

Standard Deviation

Averaging Factorprovided by BS


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Carrier to Interference & Noise Ratio� Estimates of mean and standard deviation of CINR required from MSS by BS� Demodulation required for reference signal re-calculation:

Measurement in time (index k) and frequency domain (sub carrier index n )� Method of estimation is vendor specific� Range -10 dB .. +53 dB in steps of 1 dB� Reporting towards BS using REP_RSP message

REP_RSP = Report Response Message (SS � BS)

)])[ˆ(][ˆlog(|5][ˆ

0,])[(]1[ˆ)1(0,|]0[|

][ˆ

])[ˆlog(10][ˆ

0],[]1[ˆ)1(0],0[

][ˆ

),(),(

),(][

22,

22

22

,

1

0

2

1

0

2

kkxk

kkCINRkxkCINR

kx

kk

kkCINRkkCINR

k

nksnkr

nkskCINR

CINRCINRdBCINR

avgCINRavg

CINR

CINRdBCINR

avgCINRavgCINR

N

n

N

n

µσ

αα

µµ

αµαµ

−=

>+−−

==

=

>+−−=

=

−=

∑

∑−

=

−

=

Mean Value

Standard Deviation

Re-calculated reference signal(„ideal“ signal)

Received signal

Averaging Factorprovided by BS


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Measurements w/o averaging factor

)])[ˆ(][ˆlog(|5][ˆ

0],1[ˆ0,])0[(

][ˆ

])[ˆlog(10][ˆ0],1[ˆ

0],0[][ˆ

22,

2

22

,

kkxk

kkxkR

kx

kkkk

kRk

RSSIRSSIdBmRSSI

RSSIRSSI

RSSIdBmRSSI

RSSIRSSI

µσ

µµµ

µ

−=

>−

==

=

>−=

=

Meas period [k] Meas period [k+1] Meas Period [k+2]

Reportµ(k),σ(k)

Meas Period [k+2]

Reportµ(k),σ(k)

Reportµ(k+1),σ(k)

Reporting period t)])[ˆ(][ˆlog(|5][ˆ

0],1[ˆ0,|]0[|

][ˆ

])[ˆlog(10][ˆ0],1[ˆ

0],0[][ˆ

),(),(

),(][

22,

2

22

,

1

0

2

1

0

2

kkxk

kkxkCINR

kx

kkkk

kCINRk

nksnkr

nkskCINR

CINRCINRdBCINR

CINRCINR

CINRdBCINR

CINRCINR

N

n

N

n

µσ

µµµ

µ

−=

>−

==

=

>−=

=

−=

∑

∑−

=

−

=


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List of content







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Wave 1 MSS test cases

DevelopmentMS Transmit/Receive switching gapMS-20.1DeliveredMS Transmit SynchronisationMS-19.1DeliveredMS Transmitter Relative Constellation ErrorMS-18.1DeliveredMS Transmitter Spectral FlatnessMS-17.1

Missing SignalingMS Transmit Power Control SupportMS-16.1DeliveredMS Transmit Power Dynamic Range and relative step acc.MS-15.1

Missing Meas FunctionMS Transmit Ranging SupportMS-13.1DeliveredMS Transmitter Modulation & Coding, CP and Frame TimingMS-12.1

Missing DUT supportMS Receiver Support for HandoffMS-11.1Missing DUT supportMS Transmit and Receive HARQMS-10.1

DevelopmentMS Receiver SensitivityMS-09.1DeliveredMS Receiver Maximum Input SignalMS-08.1DeliveredMS Receiver SelectivityMS-07.1

DevelopmentMS Receiver Physical CINR MeasurementMS-05.1DeliveredMS Receiver RSSI MeasurementMS-04.1DeliveredMS Receiver PreambleMS-02.1

Open Spec IssuesMS Receiver Maximum Tolerable SignalMS-01.1StatusDescriptionMRCT REF


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WiMAX BS Wave 1 test cases� BS-01.1 RX maximum tolerable signal� BS-03.1 RX ranging support� BS-04.1 RX adjacent and non-adjacent channel selectivity� BS-05.1 RX maximum input level on-channel reception tolerance� BS-06.1 RX sensitivity� BS-07.1 TX Modulation and Coding� BS-08.1 TX CP, Symbol Timing and Frame Duration Timing� BS-09.1 TX Preambles� BS-10.1 TX Power Range� BS-11.1 TX Spectral Flatness� BS-12.1 TX Relative Constellation Error� BS-13.1 Synchronisation� BS-14.1 Receive and Transmit HARQ� BS-16.1 Receive and Transmit switching gaps


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Thank You!Thank You!

1wimax air interface measurements

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