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10 Steps to Determine
3G/4G IP DataThroughput
Michael Lawton
Wireless Product Planning Engineer
Marv Wagner
Wireless Applications Engineer
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Agenda
• Introduction• 10 Steps to Data Throughput Testing – building up
complexity
• Case studies – “peeling back the onion”
• Summary
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Technology Drivers for Wireless Networks
• Higher speed,
• Lower latency
• All IP
• Convergence (Radio Access and Core Networks)
– LTE and IMS
• Interworking
E2E IP Throughput Testing is a key performance test whichaligns with these technology drivers
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Mbps ms
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Voice Data
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• Mobile penetration continues to grow: > 5billion subscribers worldwide – more than70% penetration*
• Mobile data traffic is growing exponentially -caused by growing number of mobiledevices such as tablets and smartphonesaccessing high-bandwidth applications.
• More spectrum is being made available
• In addition to subscriber growth, there isparallel growth in cellular peak data rates
It’s All About More Data, Faster!
Source: LTE World Summit presentation 2011
384 kbps 14 Mbps 21-168 Mbps 150-300 Mbps
HSPA+
LTELTE-Advanced
W-CDMA HSPA
1 GbpsGrowth in cellular peak data rates (theoretical) showing more than 2500 times higher data rate over a
period of 10 years* Note some users have multiple subscriptions
42 Mbps
VoLTE
Slide 4
= 1
exabyte!
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IP Multimedia System (IMS) Convergence
Voice Chat Video
FileShare
FindMe
Contacts/Presence
NowMultiple vertical solutions
2013 and on … All IMS/IP
Multiple
AccessNetworks
Multiple
AccessNetworks
Multiple AccessNetworks
Multiple AccessNetworks
CoreNetworks
CoreNetworks
CoreNetworks
CoreNetworks
V o i c e
S M S
I P
Legacy
Multiple
AccessNetworks
IP/ IMSarch.
Multiple AccessNetworks
Multiple AccessNetworks
Multiple AccessNetworks
Applications
Applications
Applications
Applications
IMS
RCSe
IMSVoLTE
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Traditional Data Channel Testing Methods
Physical layer testing – Benefits: Verifies coding and basic performance of L1
– Issues: Does not include higher layers, signaling, or apps
Standards-based testing – Benefits: Industry standard, repeatable, required for conformance
– Issues: Does not include apps, limited configs tested, ideal conditions
Often does not match real user experience
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Traditional Data Channel Testing Methods
Field testing
– Benefits: Real world conditions, can include apps
– Issues: Not repeatable, often requires travel, difficult to troubleshootand time consuming
Proprietary test systems
– Benefits: Repeatable test scenarios, in house 24x7 access
– Issues: Requires large investment $$ and time plus dedicated staff
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E2E IP as a Measurement
• Benefits
– A simple measurement to make yielding quick results – Tests a key performance parameter vs a headline theoretical
limit
– Is a stress test that tests the complete phone
– Excellent at finding if you have a problem• Issues
– Not so good at isolating what your problem is!
– Sometimes finds problems with the test and not the phone
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Agenda
• Introduction• 10 Steps to Data Throughput Testing – building up
complexity
• Case studies – “peeling back the onion”
• Summary
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E2E IP … 10 Step Plan, building up complexity
1. Will my device connect?
2. Do I have a good quality transmitter?
3. Do I have a good quality receiver?
4. Can I achieve max E2E tput under ideal conditions with UDP
5. What about with TCP and simultaneous UL/DL?
6. What happens if I try real application?
7. What happens under non-ideal conditions?
8. Is it robust?
9. Does it work closed loop?
10. How good is my battery life?
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Step 1: Will my device connect?
SIB info provides
capability info
UE/eNB exchange RRC connection
Request/Setup messages
Obtain IP address
Establish Defaultbearer
AAA exchanges with MME
UE/eNB exchange RRC connection
Reconfig/Complete messages
Attach complete
UE sends PRACH using
Zadoff Chu Sequence
If no response UE re-
transmits with higher
power
BS responds addressing MS
with the preamble identifier
and providing an RA-RNTI
BS sends timing
alignment
BS provides UL grant
allocation using TC-
RNTI
U L P o w e
r r a n g i n g & R a n d o m
A c c e s s
Power on
Scan for downlink
channels
Synchronize withDownlink of serving BS
Decode PBCH
Decode
PDCCH/PDSCH to get
SIB data S y n c t o
D L a n d d e c o d e
b r o a d c a s t i n f o
S e c u r i t y ,
b e a r e r e s t a b l i s h m e n t , a n d I P
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1. Will my device connect?
Protocol test
PDCP
RLC
MAC
PHY
RF
UE
IP RRC
PDCP
RLC
MAC
PHY
IPRRC
RRC
• Is the UE able to sync to the DL?
• Can I get through the connection set-up
• Can I ping my UE?
• If not take a log and de-bug message exchange
• Make edits as required with Message editor
NAS
NAS NAS
Protocol Logging and
Analysis Software (N6061A)
DL
UL
Message Editor Software(N6062A)
Script Layer 3 RRC/NASscenarios
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2. Do I have a good quality Transmitter?
RF test
UE
DL
UL
• High data throughput testing relies on good quality ULtransmissions
• Look for the following:-
– Ensure you have appropriate power and attenuation settings
– High EVM for high order modulation schemes
– High EVM at the band edge
– Spurs both in band and out of band
– Linearity issues/ spectral growth
– Switching transients, LO settling time
– Repeat tests with any “other” radio’s active
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3GPP Tx MeasurementsTest case
Number 3GPP 36.521 Test Case Description
6.2.2 UE Maximum Output Power
6.2.3 Maximum Power Reduction (MPR)
6.2.4 Additional Maximum Power Reduction (A-MPR)
6.2.5 Configured UE transmitted Output Power
6.3.2 Minimum Output Power
6.3.3 Transmit OFF Power (Covered by 6.3.4.1)
6.3.4.1 General ON/OFF time mask
6.3.4.2.1 PRACH time mask
6.3.4.2.2 SRS time mask
6.3.5.1 Power Control Absolute power tolerance
6.3.5.2 Power Control Relative power tolerance6.3.5.3 Aggregate power control tolerance
6.5.1 Frequency error
6.5.2.1 Error Vector Magnitude (EVM)
6.5.2.1 A PUSCH-EVM with exclusion period
6.5.2.2 Carrier leakage
6.5.2.3 In-band emissions for non allocated RB
6.5.2.4 EVM Equalizer spectrum flatness
6.6.1 Occupied bandwidth
6.6.2.1 Spectrum Emission Mask6.6.2.2 Additional Spectrum Emission Mask
6.6.2.3 Adjacent Channel Leakage power Ratio
6.6.3.1 Transmitter Spurious emissions
6.6.3.2 Spurious emission band UE co-existence
6.6.3.3 Additional spurious emissions
6.7 Transmit intermodulation
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UL RF Measurements
Constellation Channel Power Sub-carrier flatness
SEM ACLR EVM vs symbol
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3. Do I have a good quality receiver?
• High Data throughput testingrelies on good a quality receiver
• Look for the following:-
– sensitivity for different modulation
schemes – Max input level performance
– susceptibility to interference(simultaneous UL/DL, other radios,spurs from digital board, …)
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3. Do I have a good quality receiver?
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Rx Measurements
Section 7 Receiver Characteristics Requires SS Requires SA
7.3 Reference sensitivity level Supported Yes Yes
7.4 Maximum input level Supported Yes Yes
7.5 Adjacent Channel Selectivity (ACS) Supported Yes Yes Y
7.6.1 In-band blocking Supported Yes Yes Y
7.6.2 Out-of-band blocking
Supported Yes Yes Y7.6.3 Narrow band blocking Supported Yes Yes Y
7.7 Spurious response Supported Yes Yes Y
7.8.1 Wideband intermodulation Supported Yes Yes Y x 2
7.9 Spurious emissions Supported Yes Yes Y
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E6621A PXT
DL
UL
• iperf used to provide UDP data stream and measure received throughput
• No IP level ACKs required
• Measure results vs modulation/coding scheme
• Fluctuating BLER may indicate RF issues
• Sudden loss of data may indicate memory loss issues
DL data tput
controlled by iperfReceived DL data
tput for radio link
No Acks reqd at IP layer Tput/BLER
Slide 19
4. Can I achieve max E2E Tput under ideal
conditions with UDP?
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DL Data Throughput for TD LTE(20MHz channel, 2x2 MIMO, UL/DL config 5, special subframe config 6)
Slide 20
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TheoryMAC meas
E2E IP meas
MCS
Mbps
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Measurement Technique: UDP vs FTP (TCP)
+ Unacknowledged
+ removes flow control complexity
+ removes higher layer acks
+ Less susceptible latency
FTP
+Simulates real-world file transfers
+Transferred files can be viewedand/or compared
UDP
- Not the full story for file transfers- Not suitable for used in shared
networks
- Adds flow control complexity- Add higher layer acks and re-
transmissions- TCP Control algorithms sensitiveto multiple parameters
- Test system configuration canaffect results
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E6621A PXT
DL
UL
• TCP adds higher layer support for error detection, re-transmissions, congestion control andflow control
• TCP flow control algorithms interpret “lost” packets as congestion
• Careful consideration of parameters such as window size, number of parallel process,segment size etc. need to be considered
DL data tput
controlled by TCPflow control
Received DL data
tput for radio link
Acks reqd at IP layer
Tput/BLER
Slide 22
5. Can I achieve max E2E tput under ideal conditions with
TCP?
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TCP “Flapping” The same file FTP’d 10 times.
9 times rate is flat and consistent.
1 time there is a TCP slow-start as theflow control algorithm responds to an error
– this is known as a TCP “flap”
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6. What happens if I try a real application? …
(Voice, video, ftp …)
VIDEO
VOICE
E6621A PXT
DL
UL
Received DL data
tput for radio link
Tput/BLER
• This should not add too much complexity
• Most IP applications will typically use UDPor TCP
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7. What happens under non-ideal conditions?
• Typically fade the DL and use
robust UL
• Perform test mode and E2E
testing
• Measure MAC (BLER & Tput) and
IP layer throughput
• Use TCP with care!
AWGN
CHANNELEMULATOR
OCNG
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8. Is it robust? …
• E2E IP tests PHY, MAC, PDCP, and IP layers all working together at full rate
• Check processor can handle multiple real time activities – add SMS and voicecalls during E2E IP
• Check there are no memory overflow/leakage issues
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9. Does it work closed loop?
• BLER/Tput Testing
• Supports Test Mode and E2E Testing
CQIPMI
RI
1
RI
AUTO
2
QPSKMCS 0-9
16QAMMCS 10-16
64QAMMCS 17-25
DL MCS
AUTO
CHANNELEMULATOR
0
PMI
AUTO
1
3
2
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10. How good is my battery life?
Client:•Interactive Functional Test (IFT)•Wireless Protocol Advisor •License Keys•Modem drivers
Server:•FTP server •UDP Server • Apache HTTP server •MMS/SMS server
PSU:•Current monitoring
8960:•2G/3G BS emulation
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Agenda
• Introduction
• 10 Steps to Data Throughput Testing – building up
complexity
• Case studies – “peeling back the onion”
• Summary
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Automated Measurements Give Repeatable 21Mbps Results!
DLUDP
ULUDP
Simul UL/DL
UDP
DLFTP
UL
FTP
Simul UL/DL FTP
Consistent UL UDPOver-flood issues
Occasional TCP“flapping” (2 of 23)
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Device Performance: MIPS Matter!
This comparison was made with avery early Cat 8 HSDPA phone.
When the MAC-d block size issmaller, the device doesn’t have the
MIPS to sustain the high rate.
MAC-d PDU Size Comparison with UDP
PDU = 336 bits, Average = 497 kBytes/s (3.98 Mbps)
PDU = 656 bits, Average = 792 kBytes/s (6.34 Mbps)
UDP UDPFTP FTP
656 bit PDU
336 bit PDU
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Cat14 (21Mbps) Devices – Better the second time around
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Dual-Carrier HSDPA (42Mbps) – Diversity Matters!
Throughput for Rx Power = -20dBm to -85dBm
2nd
RF Connector terminated(or connected via a splitter)
Same device with 2nd RFconnector left “floating”
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Dual-Carrier HSDPA (42Mbps) – Diversity Matters!
Slide 34
Throughput for Rx Power = -20dBm to -85dBm
Same device with 2nd RFconnector left “floating”
Device with only 1 RFconnector available
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Not All HSDPA Cat 6 Devices Have the Same Throughput
Slide 35
TCP Flap
S C S
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Slide 36
It’s really hard to tell when
individual FTP transfers start andstop (there are 10 on this screencapture). You can see the“clean” FTP is the high data rate
on the Ch 10677 trace.
Not All HSDPA Cat 6 Devices Have the Same Throughput
N t All HSDPA C t 6 D i H th S Th h t
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Slide 37
Not All HSDPA Cat 6 Devices Have the Same Throughput
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Data Throughput Across Input Power Level
Slide 38
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6.00
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D a t a T h r o u g h p u t (
M b p s )
Received Power (dBm)
Data Throughput vs RF Input Level
Ch 10637
Classic digital modulationperformance. Consistent
performance up to sensitivity
threshold with very quick
rolloff at power levels below
threshold.
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Slide 39
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5.00
5.50
6.00
-100 -90 -80 -70 -60 -50 -40
D a t a T h r o u g h p u t
( M b p s )
Received Power (dBm)
Data Throughput vs RF Input Level
Ch 10637
Ch 10562
Data throughput roll off at
high input, low band edge
Data Throughput Across Input Power Level
D t Th h t A Ch l d RF I t L l
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Data Throughput Across Channels and RF Input Levels
Slide 40
Data Throughput vs Channel and RF Input Level - Phone A
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Received Power (dBm)
D a t a T h r o u g h p u t ( M b p s )
Ch 10562
Ch 10587
Ch 10612
Ch 10637
Ch 10662
Ch 10687
Ch 10712
Ch 10737
Ch 10762
Ch 10787
Ch 10812
Ch 10837
Very consistent sensitivityacross all RF Channels.
D t Th h t A Ch l d RF I t L l
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D a t a T h r o u g
h p u t ( M b p s )
Received Power (dBm)
Data Throughput vs Channel and RF Input Level - Phone B
Ch 10562
Ch 10585
Ch 10608
Ch 10631
Ch 10654
Ch 10677
Ch 10700Ch 10723
Ch 10746
Ch 10769
Ch 10792
Ch 10815
Ch 10838Sensitivity Issue at high band edge
(approx 10dB)
Data Throughput Across Channels and RF Input Levels
A d
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Agenda
• Introduction
• 10 Steps to Data Throughput Testing – building up
complexity
• Case studies – “peeling back the onion”
• Summary
Slide 42
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Summary
• E2E IP Data throughput is a very useful measurement
which stress tests the device against a key specification
• The measurement is good for finding problems
• Troubleshooting the problem requires you to peel back the
onion
• We have looked at examples of E2E IP issues found
testing 3G/4G commercial UEs