1wimax air interface measurements
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WiMAX Air Interface MeasurementsTRANSCRIPT
WiMAX Air Interface Measurements©2007 Rohde & Schwarz
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WiMAX Air Interface Measurements
Heinz MELLEIN, R&STechnology Management Systems & [email protected]
WiMAX Air Interface Measurements©2007 Rohde & Schwarz
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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
WiMAX Air Interface Measurements©2007 Rohde & Schwarz
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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
WiMAX Air Interface Measurements©2007 Rohde & Schwarz
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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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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
WiMAX Air Interface Measurements©2007 Rohde & Schwarz
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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“)
WiMAX Air Interface Measurements©2007 Rohde & Schwarz
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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
WiMAX Air Interface Measurements©2007 Rohde & Schwarz
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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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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
WiMAX Air Interface Measurements©2007 Rohde & Schwarz
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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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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
WiMAX Air Interface Measurements©2007 Rohde & Schwarz
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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
−=
>−
==
=
>−=
=
−=
∑
∑−
=
−
=
WiMAX Air Interface Measurements©2007 Rohde & Schwarz
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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
WiMAX Air Interface Measurements©2007 Rohde & Schwarz
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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!