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Copyright © 2013 Huawei Technologies Co., Ltd. All rights reserved.
LTE Traffic Fault Diagnosis
Copyright © 2013 Huawei Technologies Co., Ltd. All rights reserved.
Objectives
Upon completion of this course, you will be able to: Understand the E2E data transmission upon LTE Describes a roadmap for locating traffic faults Describes the methods of identifying downlink or
uplink traffic faults, basic location and isolation methods, and common fault location process for TCP and air interface problem
Page3
Copyright © 2013 Huawei Technologies Co., Ltd. All rights reserved. Page 4
Contents1. Overview2. Methodology of Traffic Fault Diagnosis3. Air Interface Fault diagnosis4. UDP Fault Diagnosis5. TCP Fault Diagnosis
Copyright © 2013 Huawei Technologies Co., Ltd. All rights reserved.
E2E Data Transmission in LTE
Copyright © 2013 Huawei Technologies Co., Ltd. All rights reserved.
Protocol Stack of E2E Data Transmission
Page 6
Serving GW PDN GW
S5/S8a
GTP-U GTP-U
UDP/IP UDP/IP
L2
Relay
L2
L1 L1
PDCP
RLC
MAC
L1
IP
UDP/IP
L2
L1
GTP-U
IP
S1-U LTE-Uu
eNodeB
RLC UDP/IP
L2
PDCP GTP-U
Relay
MAC
L1 L1
UE
Copyright © 2013 Huawei Technologies Co., Ltd. All rights reserved.
Overhead of Layers
Page 7
Wired transmission Wireless transmission
ETH 14 bytes PDCP 2 bytes
IP 20 bytes RLC 2 bytes
TCP 20 bytes MAC 3 bytes Note: The values of the headers listed in this table do not include the extension.
Data frame format on the PC
Data frame format of the MAC layer on the eNodeB
Copyright © 2013 Huawei Technologies Co., Ltd. All rights reserved.
Key Factors for LTE Throughput
Page 8
[Key factors]: cell bandwidth, modulation & coding scheme (MCS), MIMO mode, and UE capabilities.
MCS Index Modulation Order TBS Index0 2 01 2 12 2 2
.. .. .... .. .... .. ..
19 6 1720 6 1821 6 1922 6 2023 6 2124 6 2225 6 2326 6 2427 6 2528 6 2629 2
reserved30 431 6
Cell bandwidth
Available RBs
MCS
Transport block size (TBS)
MIMO modeNumber of scheduling operations
UE capabilities
Throughput (Mbit/s)
BLER
Copyright © 2013 Huawei Technologies Co., Ltd. All rights reserved.
Key Factors for LTE Throughput (cont_1)
Page 9
91 92 93 94 95 96 97 98 99 100
0 2536 2536 2600 2600 2664 2664 2728 2728 2728 2792
1 3368 3368 3368 3496 3496 3496 3496 3624 3624 3624
2 4136 4136 4136 4264 4264 4264 4392 4392 4392 4584
3 5352 5352 5352 5544 5544 5544 5736 5736 5736 5736
. . . . . . . . . . .
. . . . . . . . . . .
. . . . . . . . . . .19 39232 39232 40576 40576 40576 40576 42368 42368 42368 43816
20 42368 42368 43816 43816 43816 45352 45352 45352 46888 46888
21 45352 46888 46888 46888 46888 48936 48936 48936 48936 51024
22 48936 48936 51024 51024 51024 51024 52752 52752 52752 55056
23 52752 52752 52752 55056 55056 55056 55056 57336 57336 57336
24 55056 57336 57336 57336 57336 59256 59256 59256 61664 61664
25 57336 59256 59256 59256 61664 61664 61664 61664 63776 63776
26 66592 68808 68808 68808 71112 71112 71112 73712 73712 75376
TBSI PRBN
3GPP TS 36.213: Mapping between the PRB and TBS index for the one-codeword case
MIMO mode: determines the transmission mode (one-codeword for TM2 and dual-codeword for TM3.
Copyright © 2013 Huawei Technologies Co., Ltd. All rights reserved.
Key Factors for LTE Throughput (cont_2)
Page 10
3GPP TS 36.306: Physical parameters of different downlink UE capabilities
UE Category
Maximum number of DL-SCH transport block bits received within a TTI
Maximum number of bits of a DL-SCH transport block received within a TTI
Total number of soft channel bits
Maximum number of supported layers for spatial multiplexing in DL
Category 1 10296 10296 250368 1
Category 2 51024 51024 1237248 2
Category 3 102048 75376 1237248 2Category 4 150752 75376 1827072 2
Category 5 299552 149776 3667200 4
UE Category Maximum number of bits of an UL-SCH transport block transmitted within a TTI Support for 64QAM in UL
Category 1 5160 NoCategory 2 25456 No
Category 3 51024 No
Category 4 51024 No
Category 5 75376 Yes3GPP TS 36.306: Physical parameters of different uplink UE capabilities
UE capabilities: The single-UE peak rate is limited by the UE capabilities.
Copyright © 2013 Huawei Technologies Co., Ltd. All rights reserved.
Theoretical Throughput of the Downlink MAC Layer (20 MHz Bandwidth)
Page 11
subframe0
Guard
interval
subframe1 subframe5 slot0 slot1 slot2 slot3 slot10 slot11 0 1 2 3 4 5 6 7 8 9 10 11 12 13 0 1 2 3 4 5 6 7 8 9 10 11 12 13 0 1 2 3 4 5 6 7 8 9 10 11 12 13
99 98 97 96
.
.
. 52 51 .. 50 49 48 47
.
.
. 3 2 1
0 Legend
DL control channel PDCCH PHICH PCFCH DL shared
channel Broadcast channel Secondary
sync. channel Primary sync. channel
Copyright © 2013 Huawei Technologies Co., Ltd. All rights reserved.
Theoretical Throughput of the Uplink MAC Layer (20 MHz Bandwidth)
Page 12
subframe0 (subframe5)
Guard interva
l
subframe1 subframe2 slot0 slot1 slot2 slot3 slot12 slot13 0 1 2 3 4 5 6 7 8 9 10 11 12 13 0 1 2 3 4 5 6 7 8 9 10 11 12 13 0 1 2 3 4 5 6 7 8 9 10 11 12 13
49 48 47 . . . 11 10
9 8 7 6 5 4 3 2 1 0
Legend
PUSCH PRACH 6 RBs PUCCH SRS
Copyright © 2013 Huawei Technologies Co., Ltd. All rights reserved.
Theoretical Peak Rates of Cell and UE under Different Cell Bandwidth
Page 13
Cell Theoretical Peak Throughput
Bandwidth Category Downlink Theoretical Peak Throughput Uplink Theoretical Peak Throughput
1.4M Cat3 8.784 3.24
3M Cat3 22.128 7.992
5M Cat3 36.672 13.536
10M Cat3 73.392 27.376
15M Cat3 110.112 40.576
20M Cat3 150.752 51.024
Single User Theoretical Peak ThroughputBandwidth Category Downlink Theoretical Peak Throughput Uplink Theoretical Peak Throughput
1.4M Cat3 8.784 3.243M Cat3 22.128 7.9925M Cat3 36.672 13.536
10M Cat3 73.392 27.37615M Cat3 102.048 40.57620M Cat3 102.048 51.024
Copyright © 2013 Huawei Technologies Co., Ltd. All rights reserved. Page 14
Contents1. Overview2. Methodology of Traffic Fault Diagnosis3. Air Interface Fault diagnosis4. UDP Fault Diagnosis5. TCP Fault Diagnosis
Copyright © 2013 Huawei Technologies Co., Ltd. All rights reserved.
Typical Symptoms of Traffic Fault
Page 15
TCP method
UDP method Up link Down link
Stable but lower than peak rate by more than 5%
Fluctuates around the peak rate
Suddenly falls to a low value
Fluctuations
Stable & sub-peak rate
The throughput is stable but lower than the baseline value.
The peak throughput is lower than the reference value.
The stationary throughput under the same path loss is lower than the reference value for more than 10%.
The throughput fluctuates sharply
Throughput fluctuation Long-time
throughput drop Intermittent
throughput drop When a UE is static,
the throughput fluctuates for more than 50%.
Low throughput The peak throughput
is low. The static
throughput is low.
Copyright © 2013 Huawei Technologies Co., Ltd. All rights reserved.
Process of Traffic Fault Locating
Page 16
Copyright © 2013 Huawei Technologies Co., Ltd. All rights reserved.
Air/Non-Air Interface Fault Location
Page 17
Discover abnormal throughput.
Can data be transmitted?
Diagnose the problem.
No
Yes
YesYes
Is UDP throughput
normal?
Is the UE PC throughput
normal?
Does the Uu interface
work?
NoDiagnose the
problem.
Diagnose the problem.
Is the problem solved?
Diagnose the TCP problem.
EndCollect logs & submit the problem.
Yes
Yes
No
No
YesNo
Diagnose fault based on the UDP method
Copyright © 2013 Huawei Technologies Co., Ltd. All rights reserved.
Checking Alarms and Basic Parameters on the eNB
Page 18
When the throughput becomes faulty, export the alarm log file to check whether there are hardware faults, S1 alarms, or intermittent interruption.
Check basic parameters respectively on the eNB and the UE.
Check basic parameters on the eNB against the baseline parameters. If the basic parameters on the eNB are inconsistent with the baseline values, investigate the reasons.
Copyright © 2013 Huawei Technologies Co., Ltd. All rights reserved. Page 19
Isolating Air-Interface or Non-Air-Interface Faults
1. Turn to simple method: UDP packet transmission If the throughput in UDP transmission is evidently greater than that in TCP
transmission, a TCP fault occurs. Check the reasons of the TCP fault.
If the throughput in UDP transmission almost equals to or is lower than that in TCP
transmission, an air-interface fault occurs. Check the reasons of the air-interface fault.
2. If UDP transmission fails, upload multiple files using multiple threads or
simultaneously. If the throughput in multi-thread-based upload is evidently greater than that in single-
thread-based TCP transmission, a TCP fault occurs. Check the reasons of the TCP
fault.
If the throughput in multi-thread-based upload is almost the same as or lower than that
in single-thread-based TCP transmission, an air-interface fault occurs. Check the
reasons of the air-interface fault.
Copyright © 2013 Huawei Technologies Co., Ltd. All rights reserved. Page 20
Contents1. Overview2. Methodology of Traffic Fault Diagnosis3. Air Interface Fault diagnosis4. UDP Fault Diagnosis5. TCP Fault Diagnosis
Copyright © 2013 Huawei Technologies Co., Ltd. All rights reserved. Page 21
Contents3. Fault diagnosis on Uplink and Downlink
I. Uplink Fault DiagnosisII. Downlink Fault Diagnosis
Copyright © 2013 Huawei Technologies Co., Ltd. All rights reserved. Page 22
Air-Interface Fault Location and Troubleshooting
If UL transmission encounters a throughput fault, that can be identified as an air
interface problem. Identify the problem from the following four perspectives. Of
these, the problems of "insufficient UL scheduling" and "insufficient UL scheduling
RB" can be identified together in a direction from left to right.UL throughput fault
Insufficient UL scheduling
Insufficient UL scheduling RBs
Low UL MCS order
UL IBLER convergence fault
Insu
ffici
ent p
acke
ts
Insu
ffici
ent a
ggre
gate
m
axim
um b
it ra
te
(AM
BR
)
Inva
lid C
L po
wer
co
ntro
l
Traf
fic fr
om o
ther
U
Es
at th
e lo
cal
cell
Inte
rfere
nces
Unb
alan
ce b
etw
een
mai
n an
d di
vers
ity o
f a
UE Lim
ited
UE
ca
pabi
lity
Copyright © 2013 Huawei Technologies Co., Ltd. All rights reserved. Page 23
Air-Interface Fault Location and Troubleshooting
The single-UE UL peak throughput is decided by the following four conditions:
1. The top MCS order is 28 for category 5 UE, is 24 for category 4 UE and category 3 UE in
most cases, and is 23 for category 4 UE and category 3 UE in some cases.
2. The UE is allocated the maximum number of RBs. Maximum number of RBs available to a
single UE = Total number of RBs – Number of PUCCH RBs. The calculation result must
meet rule 2-3-5. Rule 2-3-5 means that the number of RBs for a single UE must be a
multiple of 2, 3, or 5.
3. UL scheduling is sufficient and the UL grants approximate to 1000.
4. The IBLER is less than 1%.
Bandwidth 1.4 3 5 10 15 20
Number of RBs 6 15 25 50 75 100
PUCCH RB 2 2 2 6 8 8Number of PUCCH RBs 2 2 2 2 4 4
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Air-Interface Fault Location and Troubleshooting
Small Number of RBs Small Number of UL Scheduling Times Identify a Low MCS Order Identify an Excessively High BER
Copyright © 2013 Huawei Technologies Co., Ltd. All rights reserved. Page 25
Troubleshooting Methods for Insufficient UL Scheduling RBs/Insufficient UL Scheduling
Top 1: Insufficient Packets (Insufficient Data Sources)
Note that, if the number of UL Grants is smaller than 600, that is caused by
insufficient packets. However, there is a fault which can be hardly detected.
That is, when the number of UL grants is 1000, the number of RBs
scheduled at some transmission timing intervals (TTIs) drops substantially.
This fault occurs in a peak throughout test at a high bandwidth.
Solution: Perform packet transmission based on multiple threads or replace a laptop
with better performance..
Copyright © 2013 Huawei Technologies Co., Ltd. All rights reserved. Page 26
Troubleshooting Methods for Insufficient UL Scheduling RBs/Insufficient UL Scheduling
Top 2: Insufficient AMBR Query the AMBR to check whether the throughput problem is caused by an
excessively low AMBR. The transmission rate for a new UE must be greater than
expected. You can consult the personnel responsible for the EPC to check the
subscriber information and use the trace function on the LMT to check the S1
interface. As shown in the following figure, the UL AMBR and DL AMBR are 20
kbit/s, which is too low to meet the LTE requirements. Observe the AMBR on the
UE.
Unit: bit/s
S1 tracing dataHuawei UE data
displayed on the OMT
Copyright © 2013 Huawei Technologies Co., Ltd. All rights reserved. Page 27
Troubleshooting Methods for Insufficient UL Scheduling RBs/Insufficient UL Scheduling
Top 3: Invalid CL power control Fault DescriptionThe UE that is located at a medium or far point away from the cell center has low throughput. The number of RBs is much smaller than the theoretical value in CL power control mode. However, the throughput of a UE close to the cell center can reach the peak.
When the RSRP is –100 dBm, if the CL power control is enabled, the UE at the bandwidth of 20 MHz has more than 90 RBs, and the UE at the bandwidth of 10 MHz has about 40 RBs. In comparison, the UE in OL power control mode has a maximum of 10 RBs.
Copyright © 2013 Huawei Technologies Co., Ltd. All rights reserved. Page 28
Troubleshooting Methods for Insufficient UL Scheduling RBs/Insufficient UL Scheduling
Top 4: Traffic from other UEs at the local cell Run the hidden MML
command: dsp
cellusercntstats:localcellid=4;
Monitor the number of UEs by using the User Statistics Monitoring on the M2000.
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Troubleshooting Methods for a Low MCS Order
Top 1: Interference
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Troubleshooting Methods for a Low MCS Order
Top 2: Unbalance between main and diversity of a UE
Main and diversity RSRP of a Huawei UE on
the Probe
Main and diversity RSRP of a
Samsung UE on the X-Cal
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Troubleshooting Methods for a Low MCS Order
Top 3: UE capability restrictions
CAT 4 displayed on the OMT for Huawei
test UE CAT 3 displayed in the tracing information on the
Uu interface
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RF Fault Location and Troubleshooting
The stationary RSRP in an outdoor test fluctuates for more than 6 dB. This problem is caused by deteriorating radio environment. You are advised to perform
the test in another area or adjust the UE location or antenna.
The RSRP in an outdoor test fluctuates slightly while the throughput
fluctuates sharply. Check whether the interference changes or other UEs in the cell are using
services.
Throughput performance under interference Check the interference to observe how many dBs are increased in
comparison to the back noise. This increase can be regarded as an increase
in path loss.
Copyright © 2013 Huawei Technologies Co., Ltd. All rights reserved. Page 33
Contents3. Fault diagnosis on Uplink and Downlink
I. Uplink Fault DiagnosisII. Downlink Fault Diagnosis
Copyright © 2013 Huawei Technologies Co., Ltd. All rights reserved.
Typical Air-Interface Fault Location
If a DL throughput fault occurs and can be identified to be an air-interface problem, investigate the reasons of the fault from the following five perspectives in a direction from left to right.
Page 34
DL throughput fault
Insufficient DL scheduling
Insufficient DL scheduling RBs
Downlink MIMO fault
DL IBLER convergence fault
Low DL MCS Order
UL Feedback Fault
Copyright © 2013 Huawei Technologies Co., Ltd. All rights reserved.
Insufficient DL Scheduling (1) Insufficient DL scheduling can be detected by using the
monitoring tool on the UE or on the eNodeB. The measurement is performed every one second. The number of scheduling attempts can be calculated as follows: Number of scheduling attempts of a UE = 1000/Number of UEs in the cell. If the total number of DL grants in the monitoring period is less than 95% of the UE scheduling attempts, the DL scheduling is insufficient.
Page 35
Insufficient DL scheduling also occurs if the number of UE scheduling attempts fluctuates for 50%.
Copyright © 2013 Huawei Technologies Co., Ltd. All rights reserved.
Insufficient DL Scheduling (2)
Page 36
Check the aggregate maximum bit rate (AMBR) and guaranteed bit rate (GBR). If the configured AMBR and GBR are greater than the data rate on the air interface, insufficient DL scheduling is not caused by insufficient data transmitted by the EPC
Message
Then, check whether the data received from the S1 interface is sufficient as follows:
Copyright © 2013 Huawei Technologies Co., Ltd. All rights reserved.
Insufficient DL Scheduling (3)
If the problem persists, perform the following operations:
Page 37
No
Yes
Check whether the number of DL
scheduling on the eNodeB is sufficient.
In case of a UE PDCCH demodulation problem (the following solution applies to a single UE), set the CFI to 3 and increase the PDCCH TX power for workaround. collect and send TTI tracing data on the eNodeB and the UE to Huawei headquarters for analysis.
In case of a scheduling priority problem on the eNodeB, collect and send TTI data of the eNodeB and UE to Huawei headquarters for analysis.
Copyright © 2013 Huawei Technologies Co., Ltd. All rights reserved.
Insufficient DL Scheduling RBs
Page 38
identification----Average number of UE scheduling RBs per second < Number of RBs in the cell at the bandwidth/Number of UEs in the cell.
(1) The figure on he left shows the query result on the Probe. Number of RBs = Total Code0RBCount/Code0Count(2) The preceding figure shows how to query the number of RBs on the Web LMT. Query the number of DL equivalent RBs under Trace Indicator(s).
Copyright © 2013 Huawei Technologies Co., Ltd. All rights reserved.
Insufficient DL Scheduling RBs (Cont.)
Page 39
• Check the information about UE capability on the air interface, different UE support different number of RBs
Search for the RRC Connection Reconfiguration message containing MeasurementConfig, if the value of reportOnLeave is True, the ICIC A3 measurement is used.
• Check whether the frequency selection scheduling or DL inter-cell interference coordination (ICIC) is enabled.
Copyright © 2013 Huawei Technologies Co., Ltd. All rights reserved.
DL MIMO Fault
Page 40
• To check if the MIMO mode is correctly applied or not
Copyright © 2013 Huawei Technologies Co., Ltd. All rights reserved.
Diverged DL BLER Diverged BLER in a non-peak-throughput scenario can be identified based
on the following flow chart.
Page 41
No
Yes
YesNo
Is the problem solved when UL response packet transmission is stopped (for UDP
packet injection)?
Fix the PUCCH TX power and send collected data to Huawei headquarters (If the TX power cannot be fixed, report the data directly.)
Fix the PUSCH TX power and send collected data to Huawei headquarters (If the TX power cannot be fixed, report the data directly.)
Normal
NoYes
Yes
NoDoes the MCS fluctuate
for 15 orders?Send collected data to Huawei headquarters
Does the reported CQI fluctuate for more than 5
orders?
No
Yes
Diverged BLER
Is the MCS adjusted to order 0?
Normal
Does the SNR on the air interface fluctuate for more
than 5 dB?
Send collected data to Huawei headquarters (CQI measurement on the UE may encounter a fault.)
Copyright © 2013 Huawei Technologies Co., Ltd. All rights reserved.
Low DL MCS Order A low DL MCS order is caused by the following three
reasons: The DL SINR after MIMO equalization is low, resulting in a low DL
throughput. The DL CRC becomes faulty, resulting in a low DL MCS order in
the adaptive modulation and coding (AMC) adjustment. In an outdoor test, if the DL MCS order is low, the problem may
be caused by inaccurate time and frequency tracing. UL feedback is faulty, resulting in abnormal AMC adjustment and
a low DL MCS order. The first two reasons cannot be separated. For
example, if the DL SNR after MIMO equalization is low, the DL CRC becomes faulty and therefore the DL MCS order is low.
Page 42
Copyright © 2013 Huawei Technologies Co., Ltd. All rights reserved.
Low DL SNR and CRC Fault Reasons A low DL SNR and CRC fault may be caused by the following five
reasons. Identify the problems in a direction from left to right.
Page 43
Inap
prop
riate
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twor
king
Inap
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False
PDC
CH a
larm
an
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spec
tion
erro
r
PDCC
H an
d PD
SCH
not m
atch
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Low DL SNR and abnormal CRC
High
DL
corre
latio
n
Inte
rfere
nce
from
a
neig
hbor
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cell
Time/
frequ
ency
ad
just
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RRU
Sign
al
proc
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g fa
ult o
n th
e RR
U
PDCC
H pr
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sin
g fa
ult
Copyright © 2013 Huawei Technologies Co., Ltd. All rights reserved.
Low DL SNR or CRC Fault Identification (1) High DL correlation
Page 44
Copyright © 2013 Huawei Technologies Co., Ltd. All rights reserved.
Interference from a neighboring cell
Page 45
Low DL SNR or CRC Fault Identification (2)
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Signal processing fault on the RRU
Page 46
(1) Unbalanced channels on the RRU make the UE demodulation capability deteriorate, resulting in a low MCS order. The observation method is as follows:
(2) The UE receiving power generally ranges from –50 dBm to –90 dBm. A receiving power greater than –50 dBm may cause a clipping and then a low DL SNR. A receiving power lower than – 90 dBm may lead to a low DL SNR, affecting the DL transmission performance. Observer the UE receiving power with the following methods:
(3) In cases of inconsistent TX delay on the RRU, spectrum leakage, local oscillation leakage, and faults in internal modules of the RRU, collect and send baseband data to Huawei headquarters for analysis.
Low DL SNR or CRC Fault Identification (3)
Copyright © 2013 Huawei Technologies Co., Ltd. All rights reserved.
A PDCCH processing fault may lead to a DL CRC fault.
The PDCCH processing fault can be caused by false inspection of DL PDCCH, inspection error, or non-matched PDCCH and PDSCH.
False PDCCH inspection may lead to a virtual DCI that does not exist. When PDSCH demodulation is performed based on signaling messages out of false inspection, CRC faults occur. In case of non-matched PDCCH and PDSCH, a PDCCH is allocated on the eNodeB but the corresponding PDSCH is not, or the PDCCH and PDSCH data is inconsistent, resulting in CRC faults.
Page 47
Low DL SNR or CRC Fault Identification (4)
Copyright © 2013 Huawei Technologies Co., Ltd. All rights reserved.
UL Feedback Fault The problem of DL traffic volume may persist as shown in the
following figure even if no problem is found in the number of DL scheduling attempts, number of scheduling RBs, MIMO mode, IBLER convergence, and MCS order.
Page 48
In this case, this problem can be considered as a feedback channel fault. That is, ACK/NACK messages are interpreted as NACK/ACK/DTX messages. For details about data collection of feedback channel problems, see the UL PUCCH and PUSCH fault location methods.
Copyright © 2013 Huawei Technologies Co., Ltd. All rights reserved. Page 49
Contents1. Overview2. Methodology of Traffic Fault Diagnosis3. Air Interface Fault diagnosis4. UDP Fault Diagnosis5. TCP Fault Diagnosis
Copyright © 2013 Huawei Technologies Co., Ltd. All rights reserved. Page 50
Typical UDP Fault Diagnosis – Insufficient Throughput at Server Egress
[Symptom]During a UDP packet injection test, the egress throughput is lower
than the specification.
[Diagnosis procedure]1. Check the server performance & operating system.2. Check whether the version & parameters of the packet injection
tool iperf are correct.
Copyright © 2013 Huawei Technologies Co., Ltd. All rights reserved. Page 51
Typical UDP Fault Diagnosis– Insufficient Throughput at eNB IngressThe eNodeB ingress throughput can be queried by running the DSP ETHPORT or DSP IPPATH command, or the DRB Static Monitoring interface of the M2000 cell performance trace function.
DSP ETHPORT command output.
DRB Static Monitoring interface.
Copyright © 2013 Huawei Technologies Co., Ltd. All rights reserved. Page 52
Typical UDP Fault Diagnosis – Too High Packet Loss Rate
Normally we can Start UDP Test Monitoring on the M2000 to check the packet loss rate
Packet loss rate 67%
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Typical UDP Fault Diagnosis – Uu Interface ProblemCheck the air interface as chapter before
Copyright © 2013 Huawei Technologies Co., Ltd. All rights reserved. Page 54
Typical UDP Fault Diagnosis - UE PC Problem[Symptom] Data packets can be injected to the server and transmitted normally. But the rate measured at the UE PC is low.
[Diagnosis procedure] A low rate measured at the UE PC can be caused by the UE or UE PC. 1. Replace the UE and check whether the problem is solved. 2. Check the UE PC.
A. Check the hardware configuration of the PC. B. Check the programs installed on the PC. You are advised to delete or close other programs except the test program, close the Windows firewall and the firewalls of other anti-virus software. C. Check the CPU usage. If the CPU usage exceeds 80%, the CPU is overloaded. Close programs and services that are unrelated to the test, or use a PC of better performance. Note: The PC must be connected to the mains power supply.
Copyright © 2013 Huawei Technologies Co., Ltd. All rights reserved. Page 55
Contents1. Overview2. Methodology of Traffic Fault Diagnosis3. Air Interface Fault diagnosis4. UDP Fault Diagnosis5. TCP Fault Diagnosis
Copyright © 2013 Huawei Technologies Co., Ltd. All rights reserved. Page 56
Checking TCP Parameters1. Operating system: If the PC runs in Windows XP, continue with this step. If the PC runs in Vista,
Windows 7, or other operating systems, skip this step.2. Checking and setting of TCP parametersa. Use the DrTCP tool to find corresponding network adapters under Adapter Settings on the
transmitting and receiving sides respectively. Then, set the parameters as shown in the following figure:
b. Use the TCP parameter setting.reg tool to modify parameters on the transmitting side and import the parameters.
c. After completing the preceding two operations, restart the PC to activate the modified configurations. If the parameters cannot be modified on the server, modify the configurations only on the PC connecting to the UE.
3. If the problem persists after parameter modification, go to the next step.
Copyright © 2013 Huawei Technologies Co., Ltd. All rights reserved. Page 57
TTI tracing
Perform TTI trace Interpret the traced data Results analysis If the problem persists after recommended
operations are performed, collect and send related data to Huawei headquarters for further analysis.
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Further TCP Fault Diagnosis
[Diagnosis flowchart]
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TCP Fault Diagnosis – Possible Causes of Large RTT over the Uu InterfaceUEs generate additional overhead when processing encrypted data, affecting the RTT & throughput.The default values of BSR and SR periods are 5 ms and 20 ms, respectively, different value also affect the throughput.
Copyright © 2013 Huawei Technologies Co., Ltd. All rights reserved. Page 61
TCP performance enhancer (TPE) is located on the PDCP layer of the eNB and is responsible for processing the TCP data received & transmitted by the eNB. TPE is used to preliminarily analyze the problems of packet loss, disorder, and window shrinkage.
TCP Fault Diagnosis – TPE Log Collection with M2000(1)
1. Start the M2000 and choose Monitor > Signaling Trace > Signaling Trace Management > Information Collection > IFTS Trace.
2. Select an NE.
To collect the TPE log on the M2000, perform the following operations:
Copyright © 2013 Huawei Technologies Co., Ltd. All rights reserved. Page 62
TCP Fault Diagnosis –TPE Log Collection with M2000(2)3. In the Trace Layer box of the IFTS Trace dialog box, select L1, L1 DOWN, L1 UP, and L2 Performance. In the MAC Layer Trace Field box, fill in 33/49/132.
NoteCollect the TPE log in the following sequence:1. Start IFTS Trace and select the traced items according to the preceding description.2. Disconnect and then connect the UE to the network. For E398, you need to remove and then insert this UE again. 3. To avoid adding any TPE port, you are advised to set the packet injection port to 20. A monitoring port can be added by running the MOD TPEALGO command.
Copyright © 2013 Huawei Technologies Co., Ltd. All rights reserved. Page 63
TCP Fault Diagnosis – TPE Log Collection with LMT1. Choose Trace > IFTS Trace to enter the IFTS Trace dialog box.2. In the Basic tab page, choose L1, L1 DOWN, L1 UP, and L2 Performance in the Trace Module box. 3. In the Other tab page, fill in 33/49/132 in the MAC Inner Data Trace Num box.
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