Transcript Slide 1

Concepts of 3GPP LTE
RF Parametric Tests
Renaud Duverne
Wireless 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 Authors
460 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+ 2009
LTE 2010+
LTE Work item – OFDMA air interface
SAE Work item New IP core network
Edge Evolution, more HSPA+
Rel-9
2011+
UMTS and LTE minor changes
Rel-10
2012+
LTE-Advanced (4G)
LTE timeline
2005
2006
2007
2008
2009
2010
2011
2012
Rel-7 Feasibility study
Rel-8 Specification development
Rel-8 Test development
GCF Test validation
LSTI Proof of Concept
LSTI IODT
First GCF UE
certification
LSTI IOT
LSTI Friendly
Customer Trials
First Trial
Networks
First
Commercial
Networks
Further
Commercial
Networks
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
Number of DL
Max uplink
Support for uplink
data rate Mbps transmit data streams data rate Mbps
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 subcarriers 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.
This is a sample;
Lower Symbol Rate
FFT(64 samples) gives
SCM:
This is a
symbol
= 6 bits
1 Sym = .083 usec
Data rate
= 54 Mbits/sec
@ ¾ coding = 72 Mbits/sec
@ 64QAM = 12 MSym/sec
1 symbol = one point in time
1 point in time = 1 symbol
OFDM:
64 freq bins (48 carriers
+ 4 pilots + 12 zeros)
1 Sym = 4.0 usec
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 time
1 point in time = ~meaningless
What is OFDM? – Orthogonals
Signals? BW = #sub-Carriers x Spacing
Signal structure:
Advantages of OFDM:
Many closely spaced individual carriers
Carrier spacing insures orthogonality, i.e.
Carrier spectrum = Sin (x)/X shape
Carrier placement = Sin (x)/X nulls
Excellent immunity to multi-path distortion
Excellent 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 Structures
Frame Structure type 1 (FDD)
FDD: Uplink and downlink are transmitted separately
One radio frame = 10 ms
One slot = 0.5 ms
#0
#1
#2
#3
……….
#18
#19
One subframe = 1ms
Subframe 0
Subframe 1
Subframe 9
•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
Frame Structure type 2 (TDD)
One radio frame, Tf = 307200 x Ts = 10 ms
One half-frame, 153600 x Ts = 5 ms
One subframe, 30720 x Ts = 1 ms
#0
#2
#3
DwPTS, T(variable) UpPTS, Ｔ(variable)
Guard period, T(variable)
#4
#5
One slot,
Tslot =15360 x Ts = 0.5 ms
For 5ms switch-point periodicity
#7
#8
#9
For 10ms switch-point periodicity
Downlink frame structure type 1
DL
OFDM symbols (= 7 OFDM symbols @ Normal CP)
Nsymb
160
2048
144
2048
144
2048
144
2048
144
2048
144
2048
144
2048
CP
0
CP
1
CP
2
CP
3
CP
4
CP
5
CP
6
etc.
The Cyclic Prefix is created by prepending each
symbol with a copy of the end of the symbol
0 1 2 3 4 5 6
(x Ts)
1 slot
= 15360 Ts
= 0.5 ms
P-SCH - Primary Synchronization Channel
0 1 2 3 4 5 6
S-SCH - Secondary Synchronization Channel
1 sub-frame
PBCH - Physical Broadcast Channel
= 2 slots
= 1 ms
PDCCH -Physical Downlink Control Channel
PDSCH - Physical Downlink Shared Channel
Reference Signal – (Pilot)
#0
#1
#2
#3
#4
#5
#6
#7
#8
#9
#10
#11
#12
#13
#14
#15
#16
#17
#18
#19
1 frame
= 10 sub-frames
= 10 ms
Downlink mapping
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)
16QAM
64QAM
QPSK
Uplink Frame Structure & PUSCH mapping
UL
OFDM symbols (= 7 SC-FDMA symbols @ Normal CP)
Nsymb
160
2048
144
2048
144
2048
144
2048
144
2048
144
2048
144
2048
CP
0
CP
1
CP
2
CP
3
CP
4
CP
5
CP
6
etc.
The Cyclic Prefix is created by prepending each
symbol with a copy of the end of the symbol
0 1 2 3 4 5 6
#1
#2
1 slot
= 15360 Ts
= 0.5 ms
0 1 2 3 4 5 6
1 sub-frame
#0
(x Ts)
#3
#4
#5
#6
•••••
#7
#8
#9
#10
#11
#12
#13
PUSCH - Physical Uplink Shared Channel
Demodulation Reference Signal for PUSCH
#14
#15
#16
#17
#18
#19
1 frame
The
Uplink
PUSCH
64QAM
16QAM
QPSK
BPSK(1a)
Demodulation Reference Signal (for PUSCH)
PUCCH
Demodulation Reference Signal
for PUCCH format 1a/1b
Zadoff-Chu QPSK
PUSCH ≥ 3RB
PUSCH < 3RB
or PUCCH
QPSK(1b)
Physical Layer definitions
FS Type 2 Downlink/Uplink assignment
5 ms Switch-point periodicity
#0
#1
DwPTS
#2
#3
#4
#5
#6
DwPTS
UpPTS
GP
#7
#8
#9
UpPTS
GP
10 ms Switch-point periodicity
#0
#1
DwPTS
#2
#3
#4
UpPTS
GP
#5
#6
#7
#8
#9
Subframe number
Configuration
Switch-point
periodicity
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
Physical Layer definitions
Frame Structure (TDD 5ms switch periodicity)
NsymbDL OFDM symbols (=7 OFDM symbols @ Normal CP)
160
2048
144
0
2048
1
Cyclic Prefix
0 1 2 3 4 5 6
144
0 1 2 3 4 5 6
2048
2
144
2048
3
144
2048
4
2048
144
2048
5
6
DwPTS
(3-12 symbols)
0 1 2 3 4 5 6
UpPTS
(1-2 symbols)
0 1 2 3 4 5 6
Downlink
GP(1-10
Uplink symbols)
S-SCH
Reference Signal
(Demodulation)
PBCH
PUSCH
PDCCH
UpPTS
P-SCH
1 subframe
(x Ts)
Ts = 1 / (15000x2048)=32.552nsec
1 slot
0 1 2 3 4 5 6 0 1 2 3 4 5 6
144
1slot = 15360
PDSCH
Reference Signal
DL/UL subframe
Physical Layer definitions Frame Structure
(TDD 10ms switch periodicity)
NsymbDL OFDM symbols (=7 OFDM symbols @ Normal CP)
160
2048
144
0
2048
144
1
Cyclic Prefix
2048
2
144
2048
3
144
2048
4
144
1slot = 15360
2048
144
2048
5
(x Ts)
6
Ts = 1 / (15000x2048)=32.552nsec
1 slot
DwPTS
0 1 2 3 4 5 6
0 1 2 3 4 5 6
0 1 2 3 4 5 6 0 1 2 3 4 5 6
0 1 2 3 4 5 6
0 1 2 3 4 5 6
Downlink
Uplink
S-SCH
Reference Signal
(Demodulation)
PBCH
PUSCH
PDCCH
UpPTS
P-SCH
PDSCH
Reference Signal
DL/UL subframe
Orthogonal Frequency Division Multiplexing
LTE’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:
Time domain
Frequency domain
Time domain
Coded symbol rate= R
DFT
Sub-carrier
Mapping
IFFT
CP
insertion
NTX symbols
Size-NTX
Size-NFFT
TR 25.814 Figure 9.1.1-1 Transmitter structure for SC-FDMA.
•
•
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)
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:
2ik
M
1
z (l  M scPUSCH
 k) 
DFT
PUSCH
sc

1
M scPUSCH
d (l  M scPUSCH
 i )e
j
PUSCH
M sc
i 0
k  0,..., M scPUSCH  1
l  0,..., M symb M scPUSCH  1
Subcarrier
mapping



sb
sb
 n~VRB  f hop i   N RB
mod N RB
 N sb
n~PRB (ns )  
sb
sb
sb
sb
~
~
 nVRB  f hop i   N RB  N RB  1  2 nVRB mod N RB mod N RB  N sb
n 2 inter subframe hopping
i s
intra subframe hopping
 ns
n (n )  n~ (n )  N PUCCH
PRB
s
PRB
s

 

mirroringdisabled
mirroringenabled
RB
PUCCH
n~VRB  nVRB  N RB
IFFT
sl t  
UL RB
N sc / 2  1
N RB


UL RB
k   N RB
N sc / 2
•
a k (  ) ,l  e
j 2 k 1 2 f t  N CP ,l Ts 

Although essential for detailed design, formal definitions like these do not
provide insight to most people of the underlying concepts
Comparing OFDMA and SC-FDMA
QPSK example using M=4 subcarriers
The following graphs show how a
sequence of eight QPSK symbols is
represented in frequency and time
-1,1
Q
1, 1
-1,-1
-1, 1
1, -1
-1,-1
1,1
1, -1
-1,1
Time
1,1
I
-1,-1
1,-1
V
V
CP
fc
Frequency
15 kHz
OFDMA
Data symbols occupy 15 kHz for
one OFDMA symbol period
CP
fc
60 kHz
Frequency
SC-FDMA
Data symbols occupy M*15 kHz for
1/M SC-FDMA symbol periods
SC-FDMA and OFDMA signal
generation and reception
Unique to SC-FDMA
M data
bits in
Map data to
constellation
Generate
time domain
waveform
Common with OFDMA
Perform
M-point DFT
(time to freq)
Time domain
M data
bits out
De-map
constellation
to data
Generate
constellation
Map
symbols to
sub-carriers
Perform
N-point IFFT
N>M
Frequency domain
Perform
M-point IDFT
(freq to time)
De-map subcarriers to
symbols
Upconvert
and transmit
Time domain
Perform
N-point DFT
N>M
Receive and
downconvert
Simplified model of SC-FDMA and OFDMA signal generation and reception
Page 24
Concepts of LTE and LTEAdvanced
Comparing OFDMA and SC-FDMA
PAR and constellation analysis at different BW
V
V
CP
fc
CP
Frequency
60 kHz
Frequency
15 kHz
Transmission scheme
Analysis bandwidth
OFDMA
15 kHz
Peak to average power
Same as data
symbol
ratio (PAR)
Observable IQ
Same as data symbol at
66.7 μs rate
constellation
SC-FDMA
Signal BW
(M x 15 kHz)
15 kHz
Signal BW
(M x 15 kHz)
High PAR
(Gaussian)
< data symbol
(not meaningful)
Same as data symbol
Not meaningful
(Gaussian)
< data symbol
(not meaningful)
. Same as data symbol at
M X 66.7 µs rate
Comparing OFDMA and SC-FDMA
Multipath protection with short data
The subcarriers of each SC-FDMA symbol are not the same across frequency as shown in
symbols
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.
V
V
CP
fc
Frequency
15 kHz
CP
fc
60 kHz
Frequency
OFDMA
SC-FDMA
Data symbols occupy
kHz fornature of the subcarriers
Data symbols
occupy M*15 kHz for
It is the15
constant
throughout
one OFDMA symbol
period symbol that means1/M
SC-FDMA
the SC-FDMA
when
the CP issymbol periods
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 !!
6. Transmitter Characteristics
6.2 Base station output power
6.3.1 Power Control Dynamic Range
6.3.2 Total Power Dynamic Range
6.4 Transmit ON/OFF Power
6.5 Transmitted Signal Quality
6.5.1 Frequency Error
6.5.2 Error Vector Magnitude
6.5.3 Time Alignment Between Transmitter Branches
6.5.4 DL RS power
6.6.1 Occupied Bandwidth
6.6.2 Adjacent Channel Leakage Power Ratio
6.6.3.5.1 Operating Band Unwanted Emissions
Category A
6.6.3.5.2 Operating Band Unwanted Emissions
Category B
6.6.4.5.1 Spurious Emissions Category A
6.6.4.5.2 Spurious Emissions Category B
6.6.4.5.3 Protection of the BS receiver of own or
different BS
6.6.4.5.4 Co-existence with other systems in the same
geographical area
6.6.4.5.5 Co-existence with co-located base stations
6.7 Transmitter Intermodulation
TS36.141 V8.1.0 (2008-12)
Test Requirement
E-TM1.1
E-TM2,3.1,3.2,3.3
E-TM2,3.1
Not defined yet (for TDD)
Not defined yet (apply to the transmitter ON period)
E-TM2,3.1,3.2,3.3
E-TM2,3.1,3.2,3.3
E-TM2,3.1,3.2,3.3? (for MIMO case, specified the delay between the
signals from two antennas, less than 65ns)
E-TM1.1 (deviation between indicated power on BCH and
measured power)
E-TM1.1
E-TM1.1,1.2
E-TM1.1,1.2
E-TM1.1,1.2
E-TM1.1
E-TM1.1
E-TM1.1
E-TM1.1
E-TM1.1
E-TM1.1 with 5MHz
UE Transmitter Characteristics
UE RF conformance test is NOT ready yet
6. Transmitter Characteristics
6.2.2 UE Maximum Output Power
6.2.3 UE Maximum Output Power for modulation/bandwidth
6.2.4 UE Maximum Output Power with additional requirement
6.3.1 Power Control
6.3.2 Minimum output power
6.3.3 Transmit ON/OFF power
6.4.1 Out-of-synchronization handling of output power
6.5.1 Frequency error
6.5.2.1 Error Vector Magnitude
6.5.2.2 IQ-component
6.5.2.3 In-band emissions
6.5.2.4 Spectrum flatness
6.6.1 Occupied bandwidth
6.6.2.1 Spectrum emissions mask
6.6.2.2 Additional spectrum emissions mask
6.6.2.3.1 Adjacent Channel Leakage Ratio (EUTRA)
6.6.2.3.2 Adjacent Channel Leakage Ratio (UTRA)
6.6.2.4.1 Additional ALLR requirements
6.6.3.1 Spurious emissions
6.6.3.2 Spurious emission band UE co-existence
6.6.3.3 Additional spurious emissions
6.7 Transmitter Intermodulation
TS 36.521-1 V8.0.1 (2008-12)
Test Requirement
Only power class3
MPR: less or equal to 1(QPSK), 2(16QAM) at class3
A-MPR: less or equal to 1 (QPSK,16QAM)
Power tolerance is defined (-10.5/-13.5dB)
-40dBm
-50dBm at “OFF”
FFS
+- 0.1PPM
QPSK(17.5%), 16QAM(12.5%), 64QAM(tbd) at slot
Relative carrier leakage power (origin offset) [dBc]
Emission (dB) from allocated RB to non-allocated
RB at slot
Output power of a subcarrier / Average power of
subcarrier
99% of total integrated mean power
Not exceed UE emission power at f_OOB at each
operation BW ;meas BW (30kHz or 1MHz)
Same as the above
30dBc at operation BW (5,10,15,20MHz)
33dBc, 36dBc at operation BW (5,10,15,20MHz)
43dBc at each operation BW (5,10MHz) at
handover/broadcast message
-36dBm/1k,10k,100kHz at <1GHz, -30dBm/1MHz at
<12.75GHz
-50dBm>at each EUTRA Band
-41dBm /300kHz (PHS)
-31,-41dBc at 5MHz, tbd at other,
CW:-40dBc(interferer)
Power class3: 24dBm +1/-3 dB
UE RF conformance test is NOT ready yet
per 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
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
Mar 2009
Taking the journey from WiMAX to LTE
Synchronizing with the Base Station
In LTE downlink, time and frequency synchronization is accomplished by P-SS (subframe) 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 #19
slot #0
slot #10
0 12 345 6
0 12 345 6
S-SS
S-SS
P-SS
P-SS
UE/MS Control
In LTE downlink – PDCCH, PDBCH, PMCH, PCFICH provide cell identification, control
information (RB, power control etc)
slot #0 slot #1
PDCCH (on resources not used by PCFICH/PHICH/RS), PCFICH
PHICH,PMCH – variable resource mapping
PDBCH
Taking the journey from WiMAX to LTE
Channel estimation and training
In LTE downlink, channel estimation and channel equalization is done by RS
(reference signals)
slot #0
slot #19
RS every 6th subcarrier of OFDMA symbols #0 & #4 of every slot, position varies with antenna port,
length of CP
Transferring Payload data
In LTE downlink – PDSCH carries payload data.
slot #0
PDSCH - Physical DL Shared Channel [Available Slots]
Mar 2009
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
If the frequency error is larger than a
few sub-carriers, the receiver demod
may not operate, and could cause
network interference
• 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
eNB Transmitted Signal Quality:
EVM Measurement Block
Pre-/post FFT
time/frequency
synchronization
BS TX
Remove
CP
FFT
Per-subcarrier
Amplitude/phase
correction
Symbol
detection
/decoding
Reference point
for EVM
measurement
TS 36.104 V8.4.0 FigureE.1-1: Reference point for EVM measurement
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)
Measurement Block: EVM is
measured after the FFT and a
zero-forcing (ZF) constrained
equalizer in the receiver
Downlink EVM Equalizer Definition
 For the downlink, the EVM equalizer has been constrained
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 subsequent 7
subcarriers are averaged
over 5, 7 .. 17 subcarriers
Agilent 89600 VSA EVM Setting
The second
reference
subcarrier is the
average of the
first three
subcarriers
The first
reference
subcarrier
is not
averaged
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
Important notes on EVM (DL and UL)
No transmit/receive filter will be defined
•
In UMTS a transmit/receive filter was defined
–
•
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:
–
–
•
Root raised cosine α = 0.22
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
Important notes on EVM
EVM vs. time – impact on CP reduction
• 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
EVM
Usable ISI free period
Impact of time domain
distortion induced by shaping
of the transmit signal in the
frequency domain
CP length
For this reason EVM is defined across a window at two points in time
either side of the nominal symbol centre
Important Notes on EVM
EVM Window Length
CP Len
FFT Size
EVM Window
FFT Size aligned with EVM Window End
FFT Size aligned with EVM Window Center
Agilent VSA EVM Setting
FFT Size aligned with EVM Window Start
EVM is measured at two locations in time and
the maximum of the two EVM is reported. i.e.
EVM1 measured at EVM Window Start
EVM2 measured at EVM Window End
Reported EVM = max(EVM1, EVM2)
(Per the Std.)
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
Agilent Signal Analyzer EVM Performance – DL
Signal BW
5 MHz
10 MHz
20 MHz
89650S
(typ)
0.35 %
0.40 %
0.45 %
MXA
(typ)
0.45 %
0.45 %
0.50 %
Basic channel access modes
Transmit
Antennas
The Radio
Channel
Receive
Antennas
SISO
Transmit
Antennas
The Radio
Channel
Receive
Antennas
SIMO
Single Input Single Output
Single Input Multiple Output
(Receive diversity)
MISO
Multiple Input Single Output
(Transmit diversity)
MIMO
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 LTE
Transmit
Antennas
The Radio Channel
Receive
Antennas
SU-MIMO
Concept
•
Σ
Σ
eNB 1
UE 1
MU-MIMO
•
•
UE 1
Σ
UE 2
•
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
eNB 1
•
Co-MIMO
eNB 1
Σ
Σ
eNB 2
UE 1
•
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
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
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.
Minimum requirement:
< 65 ns
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
If the frequency error is larger than a
few sub-carriers, the receiver demod
may not operate
• 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
UE Transmit Modulation:
Measurement Block
EVM is made after ZF
equalization filter and IDFT.
This is “OFDM Meas” trace
in 89601A and N9080A LTE
application
Modulated
symbols
Test equipment
DUT
Tx-Rx chain
equalizer
DFT
0
FFT
TX
Front-end
Channel
RF
correction
FFT
0
I/Q origin offset (LO Leakage) must
be removed from the evaluated
signal before calculating EVM and
In-band emissions.
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
In-band
emissions
Meas.
IDFT
EVM
meas.
UE Transmit Modulation:
EVM – For allocated resource blocks
Minimum Requirement
For signals > -40 dBm,
Parameter
EVM for individual
channels & signals
Unit
Level
QPSK
%
17.5
16QAM
%
12.5
64QAM
%
[tbd]
TS 36.101 v8.4.0 Table 6.5.2.1.1-1:
Minimum requirements for Error Vector Magnitude
Agilent Signal Analyzer EVM Performance – UL
Composite
EVM plus
Data only and
RS only EVM
Signal BW
5 MHz
10 MHz
20 MHz
89650S
(typ)
0.35 %
0.40 %
0.45 %
MXA
(typ)
0.56 %
0.56 %
0.63 %
•It is not expected that 64QAM will be allocated at the edge of the signal
UE Transmit Modulation:
I/Q Component
 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
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
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 subcarriers and as a function of the RB offset from
the edge of the allocated UL block.
In-band
emission
Measurement is made at the output of the frontend FFT, prior to equalization.
Minimum requirements
Relative emissions (dB)
In-band emission
max 25, (20 log10 EVM)  3 10 (RB 1) / NRB)
TS 36.101 v8.4.0 Table 6.5.2.3.1-1: Minimum requirements for in-band emissions
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]
and
If FUL_high - FUL_measurement ≥ [3 MHz]
[+2/-2]
If FUL_measurement - FUL_low < [3 MHz]
or
If 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 5.2-1
2. 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
Measurement & Troubleshooting Trilogy
Three Steps to successful Signal Analysis
Step 1
Step 2
Step 3
Frequency,
Basic
Advanced &
Frequency & Time
Digital Demod
Specific Demod
Get basics right,
find major problems
Signal quality
numbers, constellation,
basic error vector meas.
Find specific
problems & causes
Component design - R&D
Base station and receiver
design - R&D
Component design - R&D
Base station and receiver
design - R&D
Base station and
receiver design - R&D
 The Spectrogram
shows how the
spectrum varies with
time
See entire LTE
frame in frequency
and time
simultaneously
Find subtle
patterns, errors
Time
Spectrogram
Spectrogram
marker
P-SS,S-SS occupying
center 6 RBs
RS transmitted every 6 sub-carrier
Frequency
RS sub-carriers as selected by
the spectrogram marker
Basic Demodulation
Basic Demodulation – Constellation Diagram
Constellation Diagram
Demodulates and displays all
active channels and signals
within the measurement
interval. Color coded by
channel type
All active
channels and
signals are
included
Only control channels
and signals are
included. (QPSK, 16
QAM and 64QAM data
channels are disabled)
Basic Demodulation: Error Summary
EVM parameters: composite, peak, data and
RS EVM
Sync correlation: How well the signal is
synchronized to either RS or P-SS (user selected)
I/Q impairments
Auto detects CP Length, Cell ID, Cell ID
Group/Sector and RS sequence
EVM of individual active channels and
signals
Advanced Demodulation:
Measure EVM in Time, Frequency, Slot and RB domain
EVM per Sub-Carrier
EVM per RB
EVM per Symbol
EVM per Slot
Error Vector Spectrum :
EVM vs. Time and Frequency
Normal view
Zoomed on 72 Center Sub-Carriers (6 RB) to show
P-SS, S-SS & PBCH
vertical bars show EVM for
individual symbols contained
In each sub-carrier
 Y-Axis is EVM in %
RMS EVM
EVM
Error Vector Spectrum:
 Shows error in %EVM for
each of 300 subcarriers
(excluding DC) of 5MHz DL
BW.
 X-Axis is sub-carrier
DC sub-carrier
not used for DL
Sub-Carrier
 Color code relates EVM
reading to channel/signal type
Error Vector Time:
EVM vs. Time and Frequency
EVM
Error Vector Time:
 Shows error in %EVM for each of
140 OFDM symbols (Normal CP) of
radio frame
• X-Axis is symbol
OFDM Symbol
Turned off the PDSCH (user data) channel
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, SSS 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)
RB Error Magnitude Spectrum:
EVM vs. RB and Slot
EVM Window set to “Max of EVM
Window Start/End”
BB Filter characteristics
RB Error Magnitude Spectrum
 Shows error in %EVM for
each of 25 RB of 5MHz DL BW.
 X-Axis is RB
EVM
vertical bars show EVM for
individual slots contained
in each RB
RB
EVM Window set to “Center”
 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.
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.
2.
Occupied Bandwidth: Emission within the occupied
bandwidth
Out-of-Band (OOB) Emissions
–
–
3.
Adjacent Channel Leakage Power Ratio (ACLR)
Spectrum Emission Mask (SEM)
Spurious Emissions: Far out emissions
Occupied Bandwidth Requirement
“Does most UE energy reside within its channel BW?”
Occupied bandwidth
Measure the bandwidth of the LTE
signal that contains 99% of the
channel power
Minimum Requirement: The
occupied bandwidth shall be less than
the channel bandwidth specified in the
table below
Occupied channel bandwidth
Channel Bandwidth [MHz] 1.4
3.0
5
10
15
20
Occupied Bandwidth
1.08
2.7
4.5
9.0 MHz 13.5 MHz 18 MHz
(MHZ)
(6 RB) (15 RB) (25 RB) (50 RB) (75 RB) (100 RB)
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
Channel bandwidth
ACLR measurement
BWChannel [MHz]
1.4
3
5
10
15
20
6
15
25
50
75
100
1.08
2.7
4.5
9.0
13.5
18
Transmission bandwidth
configuration NRB
Transmission bandwidth
•
RBW(MHz)
Channel bandwidth E-UTRA (eNB, UE)
RBW
Frequency offset1 Frequency offset2
RBW
•
RBW
RBW
RBW
Channel bandwidth UTRA (eNB, UE)
RBW
Frequency
offset1
RBW=3.84MHz
RBW=3.84MHz
Frequency
offset2
RBW=3.84MHz
RBW=3.84MHz
Spectrum Emission Mask (SEM)
“Does the eNB/UE leak RF onto neighbor channels?”
Spectrum emissions mask is also known as “Operating Band Unwanted
emissions”
These unwanted emissions are resulting from the modulation process and nonlinearity 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
Carrier
Limits in
spurious domain
must be
consistent with
SM.329 [4]
10 MHz
10 MHz
Operating Band (BS transmit)
OOB domain
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.
Operating Band Unwanted emissions limit
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).
Spectrum Emission Mask– UE Example
20MHz Mask
Regulatory Masks + Proposed 20MHz LTE Mask
10
0
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
level (dBm/100kHz)
-10
-20
-30
-40
-50
-24
-22
-20
-18
-16
-14
-12
-10
-8
-6
-4
-2
offset (MHz)
TR 36.803 v1.1.0 Figure 6.6.2.1 -1: Regulatory mask and proposed E-UTRA masks
0
2
Spurious Emission Requirements
“How much power does UE leak well beyond neighbor?”
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
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
TS 36.101 v8.2.0 table 6.6.3.1-2: Spurious emissions limits
LTE at a Glance
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 Efficiency
3-4x HSDPA (downlink)
2-3x HSUPA (uplink)
3
5
10
15
20
S
SPEED!
Downlink peak data rates
(64QAM)
Peak data
rate Mbps
Multiple Input Multiple Output
1.4
Latency
Idle  active < 100 ms
Small packets < 5 ms
Antenna
config
MIMO
MHz
SISO
2x2
MIMO
4x4
MIMO
100
172.8
326.4
Uplink peak data rates
(Single antenna)
Modulation QPSK
16
QAM
64
QAM
Peak data
rate Mbps
57.6
86.4
50
Mobility
Optimized: 0–15 km/h
High performance: 15120 km/h
Functional: 120–350 km/h
Under consideration:
350–500 km/h
LTE Lifecycle
LTE VSA SW
Spectrum and signal
Analyzers, Scopes, LA and
ADS
Signal Studio
Logic Analyzers
& Scopes
Battery Drain
Characterization
Signal
Generators
ADS and
SystemVue
PXB MIMO
Rx Tester
RDX for
DigRF v4
RF Module Development
RF Proto
Design
Simulation
RF Chip/Module
RF and BB
Design
Integration
L1/PHY
BTS and Mobile
BB Chipset Development
L1/PHY
DigRF v4
FPGA and ASIC
BTS or
Mobile
System
Design
Validation
System Level
RF Testing
Protocol Development
L2/L3
Agilent/Anite SAT
Protocol
Development
Toolset
E6620A Wireless
Communications Platform
N9912A RF
Analyzer
Spectrum Analyzers
PreConformance
Conformance
Manufacturing
Network Deployment
Systems for RF and
Protocol Conformance
Drive Test
Distributed Network
Analyzers
Learn more at
www.agilent.com/find/lte LTE Poster (5989-7646EN)
Brochure (5989-7817EN)
Webcasts on LTE
• LTE Concepts
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Application Note coming