Concepts of 3GPP LTE RF Parametric Tests Renaud Duverne Wireless R&D Market Initiative Manager ©...
Transcript of Concepts of 3GPP LTE RF Parametric Tests Renaud Duverne Wireless R&D Market Initiative Manager ©...
Concepts of 3GPP LTE RF Parametric Tests
Renaud DuverneWireless R&D Market
Initiative Manager
© Copyright 2009 Agilent Technologies, Inc.
Agilent LTE Book
www.agilent.com/find/ltebook
www.amazon.com In print April 16th
The first LTE book dedicated to design and measurement
30 Authors460 pages
Book overview
Chapter 1 LTE Introduction
Chapter 2 Air Interface Concepts
Chapter 3 Physical Layer
Chapter 4 Upper Layer Signaling
Chapter 5 System Architecture Evolution
Chapter 6 Design and Verification Challenges
Chapter 7 Conformance Test
Chapter 8 Looking Towards 4G: LTE-Advanced
3GPP standards evolution (RAN & GERAN)
1999
2010
Release Commercial introduction
Main feature of Release
Rel-99 2003 Basic 3.84 Mcps W-CDMA (FDD & TDD)
Rel-4 Trials 1.28 Mcps TDD (aka TD-SCDMA)
Rel-5 2006 HSDPA
Rel-6 2007 HSUPA (E-DCH)
Rel-7 2008+ HSPA+ (64QAM DL, MIMO, 16QAM UL). Many small features, LTE & SAE Study items
Rel-8 HSPA+ 2009LTE 2010+
LTE Work item – OFDMA air interfaceSAE Work item New IP core networkEdge Evolution, more HSPA+
Rel-9 2011+ UMTS and LTE minor changes
Rel-10 2012+ LTE-Advanced (4G)
2005 2006 2007 2008 2009 2010
First GCF UE certification
Rel-7 Feasibility study
Rel-8 Test development
2011 2012
Rel-8 Specification development
GCF Test validation
First Trial Networks
FirstCommercial
NetworksFurther
Commercial Networks
LSTI Proof of Concept
LSTI IODT
LSTI IOT
LSTI Friendly Customer Trials
LTE timeline
LSTI = LTE/SAE Trial Initiative GCF = Global Certification Forum
UE categories
• In order to scale the development of equipment, UE categories have been defined to limit certain parameters
• The most significant parameter is the supported data rates:
UE Category
Max downlink data rate Mbps
Number of DL transmit data streams
Max uplink data rate Mbps
Support for uplink 64QAM
1 10.296 1 5.18 No
2 51.024 2 25.456 No
3 102.048 2 51.024 No
4 150.752 2 51.024 No
5 302.752 4 75.376 Yes
The UE category must be the same for downlink and uplink
What is OFDM?•Orthogonal Frequency Division Multiplexing•High data rate Tx using lower symbol rate on tens to thousands of closely spaced overlapping narrowband sub-carriers simultaneously•Applications in:
– Broadcasting: Digital TV (DVB-T/H) and Radio (DAB)– Wireless PAN – Certified Wireless USB™ based on WiMedia
Alliance OFDM technology– Wireless LAN – WiFi™ based on IEEE 802.11a/b/g/n – Wireless MAN – Fixed and Mobile WiMAX™ based on IEEE
802.16d and 802.16e – Adopted for 3.9G (LTE) cellular air interface
What is OFDM?- High Data Rate vs. Lower Symbol Rate
Data rate = 54 Mbits/sec @ ¾ coding = 72 Mbits/sec @ 64QAM = 12 MSym/sec
1 symbol = one point in time1 point in time = 1 symbol
SCM: OFDM:
Data rate = 54 Mbits/sec @ ¾ coding = 72 Mbits/sec @ 48 carriers= 1.5 Mbits/sec @ 64QAM = 250 kSym/sec
1 symbol = 1 point in frequency and time1 point in time = ~meaningless
1 Sym = .083 usec 1 Sym = 4.0 usec
This is a sample;FFT(64 samples) gives
64 freq bins (48 carriers + 4 pilots + 12 zeros)
This is a symbol
= 6 bits
What is OFDM? – Orthogonals Signals?
Signal structure: Many closely spaced individual carriers
Carrier spacing insures orthogonality, i.e. Carrier spectrum = Sin (x)/X shape Carrier placement = Sin (x)/X nulls
BW = #sub-Carriers x Spacing
Advantages of OFDM: Excellent immunity to multi-path distortionExcellent tolerance of single frequency
interferer
Agenda• List of LTE physical layer transmitter tests• LTE modulation quality test requirements
– Downlink– Uplink
• Modulation quality signal analysis and troubleshooting techniques
• Appendix – LTE physical layer RF measurements
FDD and TDD Frame StructuresFrame Structure type 1 (FDD) FDD: Uplink and downlink are transmitted separately
#0 #2 #3 #18#1 ………. #19One subframe = 1ms
One slot = 0.5 msOne radio frame = 10 ms
Subframe 0 Subframe 1 Subframe 9
Frame Structure type 2 (TDD)
DwPTS, T(variable)
One radio frame, Tf = 307200 x Ts = 10 msOne half-frame, 153600 x Ts = 5 ms
#0 #2 #3 #4 #5
One subframe, 30720 x Ts = 1 ms
Guard period, T(variable)
UpPTS, T (variable)
•5ms switch-point periodicity: Subframe 0, 5 and DwPTS for downlink, Subframe 2, 5 and UpPTS for Uplink•10ms switch-point periodicity: Subframe 0, 5,7-9 and DwPTS for downlink, Subframe 2 and UpPTS for Uplink
One slot, Tslot =15360 x Ts = 0.5 ms
#7 #8 #9
For 5ms switch-point periodicity
For 10ms switch-point periodicity
OFDM symbols (= 7 OFDM symbols @ Normal CP)
The Cyclic Prefix is created by prepending each symbol with a copy of the end of the symbol
160 2048 144 2048 144 2048 144 2048 144 2048 144 2048 144 2048 (x Ts)
1 frame= 10 sub-frames= 10 ms
1 sub-frame= 2 slots= 1 ms
1 slot= 15360 Ts= 0.5 ms
0 1 2 3 4 5 6etc.
CP CP CP CP CPCPCP
P-SCH - Primary Synchronization Channel S-SCH - Secondary Synchronization Channel
PBCH - Physical Broadcast Channel
PDCCH -Physical Downlink Control Channel
PDSCH - Physical Downlink Shared Channel
Reference Signal – (Pilot)
DLsymbN
#0 #1 #8#2 #3 #4 #5 #6 #7 #9 #10 #11 #12 #19#13 #14 #15 #16 #17 #18
Downlink frame structure type 1
10 2 3 4 5 6 10 2 3 4 5 6
64QAM16QAM QPSK
Downlink mappingP-SCH - Primary Synchronization Channel S-SCH - Secondary Synchronization Channel
PBCH - Physical Broadcast Channel
PDCCH -Physical Downlink Control Channel
PDSCH - Physical Downlink Shared Channel
Reference Signal – (Pilot)
Uplink Frame Structure & PUSCH mapping
10 2 3 4 5 6
#0 #1 #8#2 #3 #4 #5 #6 #7 #9 #10 #11 #12 #19#13 #14 #15 #16 #17 #18
1 frame
10 2 3 4 5 6
1 sub-framePUSCH - Physical Uplink Shared Channel
Demodulation Reference Signal for PUSCH
• • • • •
OFDM symbols (= 7 SC-FDMA symbols @ Normal CP)
The Cyclic Prefix is created by prepending each symbol with a copy of the end of the symbol
160 2048 144 2048 144 2048 144 2048 144 2048 144 2048 144 2048 (x Ts)
1 slot= 15360 Ts= 0.5 ms
0 1 2 3 4 5 6etc.
CP CP CP CP CPCPCP
ULsymbN
PUSCH
Zadoff-ChuPUSCH ≥ 3RB
QPSKPUSCH < 3RB
or PUCCH
Demodulation Reference Signal (for PUSCH)
PUCCH
Demodulation Reference Signalfor PUCCH format 1a/1b
64QAM QPSK BPSK(1a) QPSK(1b)16QAM
TheUplink
Physical Layer definitionsFS Type 2 Downlink/Uplink assignment
DwPTSGP
UpPTS DwPTSGP
UpPTS
#0 #2 #3 #4 #5 #7 #8 #9
DwPTSGP
UpPTS
5 ms Switch-point periodicity
10 ms Switch-point periodicity
#1 #6
#0 #2 #3 #4 #5 #7 #8 #9#1 #6
ConfigurationSwitch-point periodicity
Subframe number
0 1 2 3 4 5 6 7 8 9
0 5 ms D S U U U D S U U U
1 5 ms D S U U D D S U U D
2 5 ms D S U D D D S U D D
3 10 ms D S U U U D D D D D
4 10 ms D S U U D D D D D D
5 10 ms D S U D D D D D D D
6 5 ms D S U U U D S U U D
Downlink
P-SCH
S-SCH
PBCH
PDCCH
PDSCH
Reference Signal DL/UL subframe
Uplink
Reference Signal(Demodulation)
PUSCH
UpPTS
Physical Layer definitionsFrame Structure (TDD 5ms switch periodicity)
10 2 3 4 5 6 10 2 3 4 5 6 10 2 3 4 5 6 10 2 3 4 5 6 10 2 3 4 5 6 10 2 3 4 5 6
DwPTS(3-12 symbols)
UpPTS(1-2 symbols)
NsymbDL OFDM symbols (=7 OFDM symbols @ Normal CP)
Cyclic Prefix
160 2048 144 2048 144 2048 144 2048 144 2048 144 2048 144 2048 (x Ts)
1slot = 15360
0 1 2 3 4 5 6
Ts = 1 / (15000x2048)=32.552nsec1 slot
1 subframe
GP(1-10 symbols)
Downlink
P-SCH
S-SCH
PBCH
PDCCH
PDSCH
Reference Signal
Physical Layer definitions Frame Structure (TDD 10ms switch periodicity)
10 2 3 4 5 6 10 2 3 4 5 6 10 2 3 4 5 6 10 2 3 4 5 6 10 2 3 4 5 6 10 2 3 4 5 6DwPTS
NsymbDL OFDM symbols (=7 OFDM symbols @ Normal CP)
Cyclic Prefix
160 2048 144 2048 144 2048 144 2048 144 2048 144 2048 144 2048 (x Ts)
1slot = 15360
0 1 2 3 4 5 6
Ts = 1 / (15000x2048)=32.552nsec1 slot
DL/UL subframe
Uplink
Reference Signal(Demodulation)
PUSCH
UpPTS
Orthogonal Frequency Division MultiplexingLTE’s downlink and some uplink transmissions
• OFDM already widely used in non-cellular technologies only recently usable in cellular due to improved processing power
• OFDM advantages– Wide channels are more resistant to fading and OFDM equalizers are much
simpler to implement than CDMA
– Almost completely resistant to multi-path due to very long symbols
– Well suited to MIMO with easy matching of signals to uncorrelated RF channels
– It’s use of lower rate modulated subcarriers makes it scalable in terms of B/W
• OFDM disadvantages– Sensitive to frequency errors and phase noise due to close subcarrier spacing
– Sensitive to Doppler shift which creates interference between subcarriers
– Pure OFDM creates high PAR which is why SC-FDMA is used on UL
– More complex than CDMA for handling inter-cell interference at cell edge
Single Carrier FDMA:The new LTE uplink transmission scheme
• SC-FDMA is a new concept in transmission and it is important to understand how it works
• When a new concept comes along no single explanation will work for everyone
• To help put SC-FDMA in context we will use six different ways of explaining what SCFDMA is all about
• In summary: SC-FDMA is a hybrid transmission scheme combining the low peak to average (PAR) of single carrier schemes with the frequency allocation flexibility and multipath protection provided by OFDMA
Explaining SC-FDMA• The first explanation of SC-FDMA comes from the LTE physical layer “study phase” report
(3GPP TR 25.814) which had the following diagram:
• Colour coding has been added here to show the change from time to frequency and back again. This diagram is not in the final specifications.
• The processing steps explain why SC-FDMA is sometimes described in the specs as Discrete Fourier Transform Spread OFDM (DFT-SOFDM)
TR 25.814 Figure 9.1.1-1 Transmitter structure for SC-FDMA.
DFT Sub-carrier
Mapping
CP insertion
Size-NTX Size-NFFT
Coded symbol rate= R
NTX symbols
IFFT
Frequency domain Time domainTime domain
Explaining SC-FDMA• The three key processing steps shown in 25.814 are formally defined in the physical
layer specification 36.211 v8.1.0 as:
• Although essential for detailed design, formal definitions like these do not provide insight to most people of the underlying concepts
12/
2/
212,
RBsc
ULRB
RBsc
ULRB
s,CP)(
NN
NNk
TNtfkjlkl
leats
1,...,0
1,...,0
)(1
)(
PUSCHscsymb
PUSCHsc
1
0
2
PUSCHsc
PUSCHsc
PUSCHsc
PUSCHsc
PUSCHsc
MMl
Mk
eiMldM
kMlzM
i
M
ikj
PUCCHRBVRBVRB
PUCCHRBsPRBsPRB
s
s
sbsbRB
sbRBVRB
sbRB
sbRBhopVRB
sbsbRB
sbRBhopVRB
sPRB
~)(~)(
hopping subframeintra
hopping subframeinter2
enabled mirroringmodmod~21~disabled mirroringmod~
)(~
Nnn
Nnnnn
n
ni
NNNnNNifn
NNNifnnn
DFT
Subcarrier mapping
IFFT
Comparing OFDMA and SC-FDMAQPSK example using M=4 subcarriers
The following graphs show how a sequence of eight QPSK symbols is represented in frequency and time
15 kHzFrequency
fc
V
Time
OFDMA
sym
bol
OFDMA
sym
bol
CP
OFDMAData symbols occupy 15 kHz for
one OFDMA symbol period
SC-FDMAData symbols occupy M*15 kHz for
1/M SC-FDMA symbol periods
60 kHz Frequency
fc
V
Time
SC-FDM
A
sym
bol
SC-FDM
A
sym
bol
CP
1, 1 -1,-1 -1, 1 1, -1 1,1 1, -1 -1,1 -1,-1
1,1-1,1
1,-1-1,-1
I
Q Time
Page 24
Map data to constellation
Generate time domain
waveformM databits in
Perform M-point DFT (time to freq)
Map symbols to sub-carriers
Perform N-point IFFT
N > M
Upconvert and transmit
De-map constellation
to data
Generate constellation
Perform M-point IDFT(freq to time)
De-map sub-carriers to symbols
Perform N-point DFT
N > M
Receive and downconvert
Time domain Time domainFrequency domain
M databits out
Simplified model of SC-FDMA and OFDMA signal generation and reception
Unique to SC-FDMA Common with OFDMA
SC-FDMA and OFDMA signal generation and reception
Concepts of LTE and LTE-Advanced
Moray Rumney16th March 2009
Comparing OFDMA and SC-FDMAPAR and constellation analysis at different BW
15 kHzFrequency
fc
V
Time
OFDMA
sym
bol
OFDMA
sym
bol
CP
Transmission scheme OFDMA SC-FDMA
Analysis bandwidth 15 kHz Signal BW(M x 15 kHz) 15 kHz Signal BW
(M x 15 kHz)
Peak to average power ratio (PAR)
Same as datasymbol
High PAR (Gaussian)
< data symbol (not meaningful) Same as data symbol
Observable IQ constellation
Same as data symbol at 66.7 μs rate
Not meaningful (Gaussian)
< data symbol (not meaningful)
. Same as data symbol at M X 66.7 µs rate
60 kHz Frequency
V
Time
SC-FDM
A
sym
bol
SC-FDM
A
sym
bol
CP
Comparing OFDMA and SC-FDMAMultipath protection with short data symbols
15 kHzFrequency
fc
V
Time
OFDMA
sym
bol
OFDMA
sym
bol
CP
OFDMAData symbols occupy 15 kHz for
one OFDMA symbol period
SC-FDMAData symbols occupy M*15 kHz for
1/M SC-FDMA symbol periods
fc
The subcarriers of each SC-FDMA symbol are not the same across frequency as shown in earlier graphs but have their own fixed amplitude & phase for the SC-FDMA symbol duration.
The sum of M time-invariant subcarriers represents the M time-varying data symbols.
60 kHz Frequency
V
Time
SC-FDM
A
sym
bol
SC-FDM
A
sym
bol
CP
It is the constant nature of the subcarriers throughout the SC-FDMA symbol that means when the CP is
inserted, multipath protection is achieved despite the modulating data symbols being much shorter.
eNB (DL) Transmitter Characteristics eNB RF conformance test is ready to go !!eNB RF conformance test is ready to go !!
6. Transmitter Characteristics Test Requirement 6.2 Base station output power E-TM1.1 6.3.1 Power Control Dynamic Range E-TM2,3.1,3.2,3.3 6.3.2 Total Power Dynamic Range E-TM2,3.1 6.4 Transmit ON/OFF Power Not defined yet (for TDD) 6.5 Transmitted Signal Quality Not defined yet (apply to the transmitter ON period) 6.5.1 Frequency Error E-TM2,3.1,3.2,3.3 6.5.2 Error Vector Magnitude E-TM2,3.1,3.2,3.3 6.5.3 Time Alignment Between Transmitter Branches E-TM2,3.1,3.2,3.3? (for MIMO case, specified the delay between the
signals from two antennas, less than 65ns)
6.5.4 DL RS power E-TM1.1 (deviation between indicated power on BCH and measured power)
6.6.1 Occupied Bandwidth E-TM1.1 6.6.2 Adjacent Channel Leakage Power Ratio E-TM1.1,1.2 6.6.3.5.1 Operating Band Unwanted Emissions Category A
E-TM1.1,1.2
6.6.3.5.2 Operating Band Unwanted Emissions Category B
E-TM1.1,1.2
6.6.4.5.1 Spurious Emissions Category A E-TM1.1 6.6.4.5.2 Spurious Emissions Category B E-TM1.1 6.6.4.5.3 Protection of the BS receiver of own or different BS
E-TM1.1
6.6.4.5.4 Co-existence with other systems in the same geographical area
E-TM1.1
6.6.4.5.5 Co-existence with co-located base stations E-TM1.1 6.7 Transmitter Intermodulation E-TM1.1 with 5MHz
TS36.141 V8.1.0 (2008-12)
UE Transmitter Characteristics UE RF conformance test is NOT ready yetUE RF conformance test is NOT ready yet 6. Transmitter Characteristics Test Requirement 6.2.2 UE Maximum Output Power Only power class3 6.2.3 UE Maximum Output Power for modulation/bandwidth MPR: less or equal to 1(QPSK), 2(16QAM) at class3 6.2.4 UE Maximum Output Power with additional requirement A-MPR: less or equal to 1 (QPSK,16QAM) 6.3.1 Power Control Power tolerance is defined (-10.5/-13.5dB) 6.3.2 Minimum output power -40dBm 6.3.3 Transmit ON/OFF power -50dBm at “OFF” 6.4.1 Out-of-synchronization handling of output power FFS 6.5.1 Frequency error +- 0.1PPM 6.5.2.1 Error Vector Magnitude QPSK(17.5%), 16QAM(12.5%), 64QAM(tbd) at slot 6.5.2.2 IQ-component Relative carrier leakage power (origin offset) [dBc] 6.5.2.3 In-band emissions Emission (dB) from allocated RB to non-allocated
RB at slot 6.5.2.4 Spectrum flatness Output power of a subcarrier / Average power of
subcarrier 6.6.1 Occupied bandwidth 99% of total integrated mean power 6.6.2.1 Spectrum emissions mask Not exceed UE emission power at f_OOB at each
operation BW ;meas BW (30kHz or 1MHz) 6.6.2.2 Additional spectrum emissions mask Same as the above 6.6.2.3.1 Adjacent Channel Leakage Ratio (EUTRA) 30dBc at operation BW (5,10,15,20MHz) 6.6.2.3.2 Adjacent Channel Leakage Ratio (UTRA) 33dBc, 36dBc at operation BW (5,10,15,20MHz) 6.6.2.4.1 Additional ALLR requirements 43dBc at each operation BW (5,10MHz) at
handover/broadcast message 6.6.3.1 Spurious emissions -36dBm/1k,10k,100kHz at <1GHz, -30dBm/1MHz at
<12.75GHz 6.6.3.2 Spurious emission band UE co-existence -50dBm>at each EUTRA Band 6.6.3.3 Additional spurious emissions -41dBm /300kHz (PHS) 6.7 Transmitter Intermodulation -31,-41dBc at 5MHz, tbd at other,
CW:-40dBc(interferer)TS 36.521-1 V8.0.1 (2008-12) Power class3: 24dBm +1/-3 dB
UE RF conformance test is NOT ready yetper 3GPP TS 36.521-1 V8.0.1 (2008-12)
6.5 Transmit signal quality
Editor’s note: The test cases for Frequency error, EVM, IQ-component and In-band emission are incomplete. The following aspects are either missing or not yet determined:
FDD aspects missing or not yet determined:
• Reference Measurement Channels are undefined• The fixed power allocation for the RB(s) is undefined• The UE call setup details are undefined• The details on how to move from the different measurement points are undefined• The Test system uncertainties and test tolerance applicable to this test are not confirmed• Global In-Channel Tx-Test is not complete• Measurement points (test vectors) are missing • Downlink Cell power levels for the frequency error test procedure are not defined• Test case is not complete for FDD
TDD aspects missing or not yet determined:
Test case is not complete for TDD
• The transmission signal test cases descriptions have been verified to apply for both FDD and TDD exactly as they are
Agenda• List of LTE physical layer transmitter tests• LTE modulation quality test requirements
– Downlink– Uplink
• Modulation quality signal analysis and troubleshooting techniques
• Appendix – LTE physical layer RF measurements
Taking the journey from WiMAX to LTEMar 2009
Key functions between the mobile (UE) and base station (eNB)
o Synchronizing with the base station
o UE/MS Control
o Channel estimation and training
o Transferring Payload data
Taking the journey from WiMAX to LTE
Synchronizing with the Base Station In LTE downlink, time and frequency synchronization is accomplished by P-SS (sub-frame) and S-SS (frame) in the last two symbols of slot #0 and #10. Aligns OFDM symbols to timing reference in eNB using timing advance (TA)
slot #0 slot #10
S-SS S-SS
P-SS
slot #19
P-SS
0 1 2 3 4 5 6 0 1 2 3 4 5 6
UE/MS Control
In LTE downlink – PDCCH, PDBCH, PMCH, PCFICH provide cell identification, control information (RB, power control etc)
slot #1
PDBCH
slot #0
PDCCH (on resources not used by PCFICH/PHICH/RS), PCFICH
PHICH,PMCH – variable resource mapping
Mar 2009
Channel estimation and training In LTE downlink, channel estimation and channel equalization is done by RS
(reference signals)
RS every 6th subcarrier of OFDMA symbols #0 & #4 of every slot, position varies with antenna port, length of CP
slot #0 slot #19
Transferring Payload data In LTE downlink – PDSCH carries payload data.
PDSCH - Physical DL Shared Channel [Available Slots]
slot #0 slot #19
Transmitted Signal Quality – eNB (Downlink)
Currently there are four requirements under the transmitted signal quality category for an eNB:
• Frequency error• EVM • Time alignment between transmitter
branches• DL RS Power
eNB Transmitted Signal Quality: Frequency Error
• A quick test is use the Occupied BW measurement
• An accurate measurement can then be made using the demodulation process
•Minimum Requirement (observed over 1 ms):
±0.05 PPM
If the frequency error is larger than a few sub-carriers, the receiver demod may not operate, and could cause network interference
eNB Transmitted Signal Quality:EVM Measurement Block
TS 36.104 V8.4.0 FigureE.1-1: Reference point for EVM measurement
Pre-/post FFTtime/frequencysynchronization
BS TX Remove CP
FFTPer-subcarrierAmplitude/phasecorrection
Symbol detection/decoding
Reference pointfor EVMmeasurement
Measurement Block: EVM is measured after the FFT and a zero-forcing (ZF) constrained equalizer in the receiver
EVM measurement is defined over one sub-frame (1ms) in the time domain and 12 subcarriers (180kHz) in the frequency domain. However equalizer
is calculated over full frame (10 sub-frames)
Downlink EVM Equalizer Definition
The subsequent 7 subcarriers are averaged over 5, 7 .. 17 subcarriers
From the 10th subcarrier onwards the window size is 19 until the upper edge of the channel is reached and the window size reduces back to 1
The first reference subcarrier is not averaged
The second reference subcarrier is the average of the first three subcarriers
Reference subcarriers TS 36.104 V8.4.0 Figure E.6-1: Reference subcarrier
smoothing in the frequency domain
Rather than use all the RS data to correct the received signal a moving average is performed in the frequency domain across the channel which limits the rate of change of correction
For the downlink, the EVM equalizer has been constrained
Agilent 89600 VSA EVM Setting
Important notes on EVM (DL and UL)No transmit/receive filter will be defined
• In UMTS a transmit/receive filter was defined– Root raised cosine α = 0.22
• This filter was also used to make EVM measurements– Deviations from the ideal filter increased the measured EVM
• In LTE with OFDMA/SC-FDMA no TX/RX filter is defined• The lack of a filter creates opportunities and problems:
– Signal generation can be optimized to meet in-channel and out of channel requirements– Signal reception and measurement have no standard reference
• It is expected that real receivers will use the downlink reference signals (pilots) to correct for frequency and phase
– But no standard for how to do this will be specified
• The lack of a defined transmit filter means that trade-offs can be made between in-channel performance and out of channel performance (ACLR, Spectrum emission mask)
• But applying too aggressive filtering can introduce delays to the signal which appear like multipath and reduce the effective length of the CP
For this reason EVM is defined across a window at two points in time either side of the nominal symbol centre
Important notes on EVMEVM vs. time – impact on CP reduction
Usable ISI free period
CP length
EV
M
Impact of time domain distortion induced by shaping of the transmit signal in the frequency domain
CP Len FFT Size
EVM Window
FFT Size aligned with EVM Window End
EVM is measured at two locations in time and the maximum of the two EVM is reported. i.e.
EVM1 measured at EVM Window StartEVM2 measured at EVM Window EndReported EVM = max(EVM1, EVM2)(Per the Std.)
Important Notes on EVMEVM Window Length
Agilent VSA EVM SettingFFT Size aligned with EVM Window Center
FFT Size aligned with EVM Window Start
eNB Transmitted Signal Quality:Error Vector Magnitude (EVM)
EVM measurement requires the signal to be correctly demodulated
EVM specification differs for each modulation scheme
Minimum Requirement:
Parameter Unit Level
QPSK % 17.5
16QAM % 12.5
64QAM % 8
Signal BW 89650S(typ)
MXA (typ)
5 MHz 0.35 % 0.45 %10 MHz 0.40 % 0.45 %20 MHz 0.45 % 0.50 %
Agilent Signal Analyzer EVM Performance – DL
Basic channel access modesTransmitAntennas
ReceiveAntennas
SISO
The Radio Channel
MISO
Single Input Single Output
Multiple Input Single Output
(Transmit diversity)
ReceiveAntennas
TransmitAntennas
MIMO
The Radio Channel
SIMO
Single Input Multiple Output
(Receive diversity)
Multiple Input Multiple Output(Multiple stream)
MIMO operation
• MIMO gain comes from spatial diversity in the channel• The performance can be optimized using precoding• Depending on noise levels, the rank (number of parallel
streams) can be varied
• The principles of spatial diversity, precoding and rank adaptation can seem complex but can be readily explained by reference to well-known acoustic principles
MIMO in LTETransmitAntennas
ReceiveAntennas
The Radio Channel
SU-MIMO
eNB 1 UE 1
UE 2
UE 1
eNB 1
MU-MIMO
Co-MIMO
eNB 2
eNB 1
UE 1
Σ Σ
Σ
ΣΣ
• Single User: “Conventional” MIMO One user gets the full benefit of the increased capacity
• Example: Downlink in LTE
• Multi-User: The Base Station schedules two mobiles to transmit their own data streams, but as a MIMO signal.
• Example: Uplink in LTE
• Cooperative MIMO: Co-MIMO involves two separate entities at the transmission end. The example here is a downlink case in which two eNB “collaborate” by sharing data streams to precode the spatially separate antennas for optimal communication with at least one UE.
• Example: Part of Advanced LTE
Concept
eNB Transmitted Signal Quality:Time alignment between transmitter branches
• This test is required for eNB supporting TX diversity or spatial multiplexing transmission
• Purpose is to measure time delay between the signals from two transmit antennas
Minimum requirement: < 65 ns
It is RS based measurement. Measures relative timing error between RS on antenna port 0 and RS on antenna port 1. It is one of the many metrics reported under MIMO Info trace.
eNB Transmitted Signal Quality:DL RS Power
Measures RS transmitted power
Test requirement:
DL RS power shall be within [+/- 2.1] dB of the DL RS power indicated on the BCH
RS power, as well as EVM, measured at base station RF output is reported under Frame Summary trace
Agenda• List of LTE physical layer transmitter tests• LTE modulation quality test requirements
– Downlink– Uplink
• Modulation quality signal analysis and troubleshooting techniques
• Appendix – LTE physical layer RF measurements
Transmitted Signal Quality – UE (Uplink)
Frequency error Transmit modulation
Currently there are four requirements under the transmit modulation category for a UE:
1. EVM for allocated resource blocks 2. I/Q Component (also known as carrier leakage power or
I/Q origin offset)3. In-Band Emission for non-allocated resource blocks 4. Spectrum flatness for allocated RB
UE Transmitted Signal Quality: Frequency Error
• A quick test is use the Occupied BW measurement
• An accurate measurement can then be made using the demodulation process
•Minimum Requirement (observed over 1 ms):
UE: ±0.1 PPM
If the frequency error is larger than a few sub-carriers, the receiver demod may not operate
UE Transmit Modulation:Measurement Block
Modulated symbols
DFT
FFT TX Front-end
Channel RF correction FFT
Tx-Rx chainequalizer
In-bandemissions
Meas.
IDFTEVM
meas.
DUT Test equipment
0
0
In-band emissions measurement is made in frequency domain, after FFT, with no equalizer filter. This is “OFDM Freq Meas” trace in 89601A & N9080A LTE application
EVM is made after ZF equalization filter and IDFT. This is “OFDM Meas” trace in 89601A and N9080A LTE application
I/Q origin offset (LO Leakage) must be removed from the evaluated
signal before calculating EVM and In-band emissions.
UE Transmit Modulation:EVM – For allocated resource blocks
Minimum Requirement For signals > -40 dBm,
Parameter Unit Level
QPSK % 17.5
16QAM % 12.5
64QAM % [tbd]
•It is not expected that 64QAM will be allocated at the edge of the signal
TS 36.101 v8.4.0 Table 6.5.2.1.1-1: Minimum requirements for Error Vector Magnitude
Signal BW 89650S(typ)
MXA (typ)
5 MHz 0.35 % 0.56 %10 MHz 0.40 % 0.56 %20 MHz 0.45 % 0.63 %
Agilent Signal Analyzer EVM Performance – UL
EVM for individual channels & signals
Composite EVM plus Data only and RS only EVM
UE Transmit Modulation:I/Q Component
LO Leakage Parameters Relative Limit (dBc)
Output power >0 dBm -25
- 30 dBm ≤ Output power ≤0 dBm -20
-40 dBm Output power < -30 dBm -10
TS 36.101 v8.4.0 Table 6.5.2.2.1-1: Minimum requirements for Relative Carrier Leakage Power
I/Q Component (LO Leakage or IQ Offset) revels the magnitude of the carrier feedthrough present in the signal
I/Q Component is removed from EVM result
Minimum requirements
UE Transmit Modulation:In-band Emission – For non-allocated RBs
The in-band emission is measured as the relative UE output power of any non –allocated RB(s) and the total UE output power of all the allocated RB(s)
It is defined as an average across 12 sub-carriers and as a function of the RB offset from the edge of the allocated UL block.
Measurement is made at the output of the front-end FFT, prior to equalization.
Minimum requirements
In-band emissionRelative emissions (dB)
TS 36.101 v8.4.0 Table 6.5.2.3.1-1: Minimum requirements for in-band emissions
)/)1(103)log20(,25max 10 RBRB NEVM
In-band emission
UE Transmit Modulation:Spectrum flatness
The spectrum flatness is defined as a relative power variation across the subcarrier of all RB of the allocated UL block
Minimum requirements for spectrum flatness (normal conditions)
Spectrum Flatness Relative Limit (dB)
If FUL_measurement - FUL_low ≥ [3MHz]
andIf FUL_high - FUL_measurement ≥ [3 MHz]
[+2/-2]
If FUL_measurement - FUL_low < [3 MHz]
orIf FUL_high - FUL_measurement < [3 MHz]
[+3/-5]
NOTE:1. FUL_low and FUL_high refers to each E-UTRA frequency band specified in Table 5.2-12. FUL_measurement refers to frequency tone being evaluated
Example for LTE UL band 1:
FUL_low – FUL_high
1920 MHz – 1980 MHz
Agenda• List of LTE physical layer transmitter tests• LTE modulation quality test requirements
– Downlink– Uplink
• Modulation quality signal analysis and troubleshooting techniques
• Appendix – LTE physical layer RF measurements
Get basics right,find major problems
Find specificproblems & causes
Signal qualitynumbers, constellation,basic error vector meas.
Frequency,
Frequency & Time
Advanced &
Specific Demod
Basic
Digital Demod
Component design - R&DBase station and receiver
design - R&D
Component design - R&DBase station and receiver
design - R&D
Base station and receiver design - R&D
Measurement & Troubleshooting TrilogyThree Steps to successful Signal Analysis
Step 1 Step 3Step 2
Spectrogram
Tim
e RS transmitted every 6 sub-carrier
P-SS,S-SS occupying center 6 RBs
RS sub-carriers as selected by the spectrogram marker
The Spectrogram shows how the spectrum varies with timeSee entire LTE frame in frequency and time simultaneouslyFind subtle patterns, errors
Spectrogram marker
Frequency
Basic Demodulation
Basic Demodulation – Constellation DiagramConstellation Diagram Demodulates and displays all active channels and signals within the measurement interval. Color coded by channel type
Only control channels and signals are included. (QPSK, 16 QAM and 64QAM data channels are disabled)
All active channels and signals are included
Basic Demodulation: Error Summary
EVM parameters: composite, peak, data and RS EVM
Auto detects CP Length, Cell ID, Cell ID Group/Sector and RS sequence
I/Q impairments
Sync correlation: How well the signal is synchronized to either RS or P-SS (user selected)
EVM of individual active channels and signals
Advanced Demodulation:Measure EVM in Time, Frequency, Slot and RB domain
EVM per Sub-CarrierEVM per Symbol
EVM per RB EVM per Slot
Normal view
Zoomed on 72 Center Sub-Carriers (6 RB) to show P-SS, S-SS & PBCH
EV
M
Sub-Carrier
DC sub-carrier not used for
DL
Error Vector Spectrum: Shows error in %EVM for each of 300 subcarriers (excluding DC) of 5MHz DL BW.
X-Axis is sub-carrier vertical bars show EVM for individual symbols contained In each sub-carrier
Y-Axis is EVM in % Color code relates EVM reading to channel/signal type
Error Vector Spectrum :EVM vs. Time and Frequency
RMS EVM
Error Vector Time:EVM vs. Time and Frequency
Turned off the PDSCH (user data) channel
Error Vector Time: Shows error in %EVM for each of 140 OFDM symbols (Normal CP) of radio frame
• X-Axis is symbol vertical bars show EVM for individual sub-carriers contained
in each symbol
• Y-Axis is EVM in %Color coding makes it easy to visualize which channels/ signals have high EVM. In this example, S-SS and P-SS transmitted on symbols 5 and 6 of slots #1& #10 have the highest EVM (Marker can also be used to identify the channel type as well as EVM values)
EV
M
OFDM Symbol
RB Error Magnitude Spectrum:EVM vs. RB and Slot
BB Filter characteristics
RB Error Magnitude Spectrum Shows error in %EVM for each of 25 RB of 5MHz DL BW.
X-Axis is RB vertical bars show EVM for individual slots contained in each RB
Y-Axis is EVM in %Best EVM trace to view the characteristics of transmit filter or any other impairment that affect the edges of the band.Since data is allocated to each user based on RB, best way to look at performance per each RB.
EVM Window set to “Center”
EVM Window set to “Max of EVM Window Start/End”
EV
M
RB
Agenda• List of LTE physical layer transmitter tests• LTE modulation quality test requirements
– Downlink– Uplink
• LTE signal generation techniques– Testing amplifiers– Testing receivers
• Modulation quality signal analysis and troubleshooting techniques
• Appendix – LTE physical layer RF measurements
Transmit Power – UE“Does the UE transmit too much or too little?”
• MOP (Maximum Output Power)– Method: broadband power
measurement (No change from UMTS)
• MPR (Maximum Power Reduction)– Definition: Power reduction due to higher
order modulation and transmit bandwidth (RB) – this is for UE power class 3
• A-MPR (Additional MPR)– Definition: Power reduction capability to meet
ACLR and SEM requirements
Power measurement for each active channel after demodulation
Channel power measurement using swept spectrum analyzer
Output RF Spectrum Emissions Unwanted emissions consist of:1. Occupied Bandwidth: Emission within the occupied
bandwidth
2. Out-of-Band (OOB) Emissions– Adjacent Channel Leakage Power Ratio (ACLR)– Spectrum Emission Mask (SEM)
3. Spurious Emissions: Far out emissions
Occupied Bandwidth Requirement“Does most UE energy reside within its channel BW?”
Occupied bandwidthMeasure the bandwidth of the LTE signal that contains 99% of the channel power
Occupied channel bandwidthChannel Bandwidth [MHz] 1.4 3.0 5 10 15 20Occupied Bandwidth (MHZ)
1.08(6 RB)
2.7(15 RB)
4.5(25 RB)
9.0 MHz(50 RB)
13.5 MHz(75 RB)
18 MHz(100 RB)
Minimum Requirement: The occupied bandwidth shall be less than the channel bandwidth specified in the table below
ACLR Requirements – eNB case“Does the eNB transmit in adjacent channels?”
ACLR (Adjacent Channel Leakage Ratio) measurement:
Measure the channel power at the carrier frequency
Measure the channel power at the required adjacent channels
Ensure the eNB power at adjacent channels meets specs
ACLR defined for two cases
• E-UTRA (LTE) ACLR 1 and ACLR 2 with square measurement filter
• UTRA (W-CDMA) ACLR 1 and ACLR 2 with 3.84 MHz RRC measurement filter with roll-off factor =0.22.
ACLR limits defined for adjacent LTE carriers
ACLR limits defined for adjacent UTRA carriers
ACLR measurementACLR measurement
• Channel bandwidth E-UTRA (eNB, UE)
• Channel bandwidth UTRA (eNB, UE)
RBW
Frequency offset1 Frequency offset2
RBW RBW RBW RBW
RBW
Frequency offset2
RBW=3.84MHz
Frequency offset1
RBW=3.84MHzRBW=3.84MHzRBW=3.84MHz
Channel bandwidth
BWChannel [MHz] 1.4 3 5 10 15 20
Transmission bandwidth
configuration NRB 6 15 25 50 75 100
Transmission bandwidth
RBW(MHz) 1.08 2.7 4.5 9.0 13.5 18
Spectrum Emission Mask (SEM)“Does the eNB/UE leak RF onto neighbor channels?”
Operating Band (BS transmit)
10 MHz 10 MHz
Operating Band Unwanted emissions limit
CarrierLimits in
spurious domain must be
consistent with SM.329 [4]
OOB domain
Spectrum emissions mask is also known as “Operating Band Unwanted emissions”
These unwanted emissions are resulting from the modulation process and non-linearity in the transmitter but excluding spurious emissions
Measure the Tx power at specific frequency offsets from the carrier frequency and ensure the power at the offsets is within specifications
TR 36.804 v1.2.0 figure 6.6.2.2-1 Defined frequency range for Operating band unwanted emissions with an example RF carrier and related mask shape (actual limits are TBD).
eNB example:Base station SEM limits are defined from 10 MHz below the lowest frequency of the BS transmitter operating band up to 10 MHz above the highest frequency of the BS transmitter operating band.
20MHz MaskRegulatory Masks + Proposed 20MHz LTE Mask
-50
-40
-30
-20
-10
0
10
-24 -22 -20 -18 -16 -14 -12 -10 -8 -6 -4 -2 0 2
offset (MHz)
lev
el
(dB
m/1
00
kH
z)
WCDMA
FCC band 5
FCC band 2
FCC band 7
Ofcom
Japan PHS
mask 6/7 RBs
mask 15/16 RBs
mask 25 RBs
mask 50 RBs
mask 75 RBs
mask 100 RBs
Spectrum Emission Mask– UE Example
TR 36.803 v1.1.0 Figure 6.6.2.1 -1: Regulatory mask and proposed E-UTRA masks
Spurious Emission Requirements“How much power does UE leak well beyond neighbor?”
Frequency Range Maximum Level Measurement Bandwidth
9 kHz f < 150 kHz -36 dBm 1 kHz
150 kHz f < 30 MHz -36 dBm 10 kHz
30 MHz f < 1000 MHz -36 dBm 100 kHz
1 GHz f < 12.75 GHz -30 dBm 1 MHz
Spurious emissions are emissions caused by unwanted transmitter effects such as harmonics emission & intermodulation products but exclude out of band emissions
Example of spurious emissions limit for a UE
TS 36.101 v8.2.0 table 6.6.3.1-2: Spurious emissions limits
S
SPEED! S
SPEED!
Nov 2004 LTE/SAE High level requirements
Reduced cost per bit
More lower cost services with better user experience
Flexible use of new and existing frequency bands
Simplified lower cost network with open interfaces
Reduced terminal complexity and reasonable power consumption
Nov 2004 LTE/SAE High level requirements
Reduced cost per bit
More lower cost services with better user experience
Flexible use of new and existing frequency bands
Simplified lower cost network with open interfaces
Reduced terminal complexity and reasonable power consumption
Spectral Efficiency3-4x HSDPA (downlink)2-3x HSUPA (uplink)
LatencyIdle active < 100 msSmall packets < 5 ms
Spectral Efficiency3-4x HSDPA (downlink)2-3x HSUPA (uplink)
LatencyIdle active < 100 msSmall packets < 5 ms
Downlink peak data rates(64QAM)
Antenna config
SISO2x2
MIMO4x4
MIMO
Peak data rate Mbps
100 172.8 326.4
Uplink peak data rates(Single antenna)
Modulation QPSK16
QAM64
QAM
Peak data rate Mbps
50 57.6 86.4
MHz
1.4
3
5
10
15
20
Optimized: 0–15 km/hHigh performance: 15-120 km/hFunctional: 120–350 km/hUnder consideration: 350–500 km/h
Optimized: 0–15 km/hHigh performance: 15-120 km/hFunctional: 120–350 km/hUnder consideration: 350–500 km/h
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