4.oeo000040 lte traffic fault diagnosis issue 1

LTE Traffic Fault Diagnosis (Drive Test)

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� Insufficient resources for scheduling(RB Number&Grant)


� [Probe] The number downlink/uplink Grant times is less than 0.9 multiplying the

theoretical value.

� [Probe] The number of PDSCH RBs is less than the theoretical RB value for the total

system bandwidth multiplying 0.9.

� Coding with low values (MCS, IBLER, and Rank)

� [Probe] The downlink or uplink IBLER is greater than 12%.

� [U2000] For interference detection monitoring in cell performance monitoring,

there is an interference value of an RB greater than –120 dBm (eRAN3.0) or –110

dBm (eRAN6.0).

� The Rank2 ratio is less than 80%.

� Poor coverage

� [Probe] Downlink: The SINR is lower than 25 dB (in the peak rate test scenario), or

the RSRP difference between the local cell and a neighboring cell is lower than 10

dBm.

� [Probe] Uplink: During the uplink test, the path loss is lower than 100, the PUSCH

power is greater than 20 dBm, the IBLER converges to 10%, and the MCS is low

(the MCS should be greater than 23 according to the peak rate requirement).

� Abnormal receive power

� [Probe] The average difference between RSRPs of two antennas in the downlink is

greater than 3 dB.


� Based on problem scenarios, use different methods to check for operations and external


events that affect the service rate.

� For performance deterioration problems, perform this step first to determine the

correlation between the external events/historical operations and the deterioration events

in terms of time/scope.

� For multiple faulty eNodeBs, focus on operations that affect network performance, such as

EPC or transmission operations. For eNodeB-level operations, select top 10 cells for analysis


� The Hardware Module is faulty:


� ALM-26532 RF Unit Hardware Fault

� ALM-26538 RF Unit Clock Problem

� ALM-26506 RF Unit Optical Interface Performance Degraded

� The coverage shrinks, therefore the service rate is affected:

� ALM-26520 RF Unit TX Channel Gain Out of Range

� Handover failure may happen and the service rate is affected:

� ALM-29204 X2 Interface Fault

� Uplink demodulation performance may be affected:

� ALM-26521 RF Unit RX Channel RTWP/RSSI Too Low

� Uplink coverage shrinks:

� ALM-26522 RF Unit RX Channel RTWP/RSSI Unbalanced

� ALM-26787 RHUB-pRRU CPRI Interface Error

� ALM-26758 TMA Running Data and Configuration Mismatch

� ALM-26755 TMA Bypass

� ALM-26530 RF Unit ALD Current Out of Range


� Influence by PDCCH Symbol Number


� Downlink data transmission throughput strongly associated with the number of

PDCCH symbols. The default is the symbol 3 PDCCH adaptive. When peak test, we

can manually set the initial number of symbols of PDCCH to be 1.

� Influence by fast ANR

� eNodeB will be automatically selected at random to support fast ANR UE. UE will

continue to report neighborhood information to the eNodeB, which would affect

the UE uplink throughput. If the fast ANR is enabled, the rate of the selected UE

will be decreased by 1/4.

� Influence by Frequency Selective Scheduling

� If this scheduling is enabled, the Ues can only part of the frequency instead of all

frequency. Therefore the throughput will be affected.


� -l 1400: Indicates the injected packet length. The default value is 1498 bytes (measured at the IP

layer, including the IP header). This parameter must be set at both the sender and receiver.


layer, including the IP header). This parameter must be set at both the sender and receiver.

� -p 5010: Indicates the injecting port. The default value is 5001. This parameter must be set at both

the sender and receiver. Note that this parameter at the sender indicates the injecting port and the

one at the receiver indicates the receiving port.

� -P 2: Indicates two injecting threads. Assuming that the injecting rate is 1 Mbit/s (indicated by -b 1m),

the injecting rate becomes 2 Mbit/s if two threads are used to inject packets. This parameter is set on

the sender only.

� Injecting TCP packets

� To set up a receiving service in the receiver, run the iperf –s –i 1 –w 512k command,

� Where –s indicates receiving service, –i 1 indicates that the received traffic volume is

displayed once per second, and –w 512k indicates that the receive window of the receiver

is 512 KB. This command lacks the –u option in comparison with the command executed

for UDP at the receiver.

� Run the iperf –c x. x. x. x –t 1000 –i 1 –w 512k command,

� where –c x. x. x. x indicates the IP address that the sender is connected to, -t 1000 indicates

inject duration of 1000 seconds, -i 1 indicates that the injected traffic volume is displayed

once per second, and -w 512k indicates that the receive window of the sender is 512 KB.

� Other parameters are explained as follows:

� -M 1400: Indicates the maximum segment size (MSS) of TCP packets, excluding the IP

header and TCP header. The default value is 1460 bytes. This parameter must be set at both

the sender and receiver.

� -p 5010: Indicates the injecting port. The default value is 5001. This parameter must be set

at both the sender and receiver. Note that this parameter at the sender indicates the

injecting port and the one at the receiver indicates the receiving port.

� -P 2: Indicates two threads for injecting or receiving packets. This parameter is set on the

sender only.


� If no route is configured, run the following command to configure the return route:


� route add [service IP address of the UE] mask [subnet mask] [service IP address of

the server] –p


� If the aggregate maximum bit rate (AMBR) is set to 0, the UE can access the network but


fails in data transmission. In this case, check the AMBR value in the access message.

� View the AMBR in the S1AP_INITIAL_CONTEXT_SETUP_REQ message traced over the S1

interface. If the AMBR value is 0, contact evolved packet core (EPC) personnel to modify

the AMBR.


� The ROHC feature provides an efficient header compression mechanism for RTP, UDP, and


IP packets to improve transmission efficiency and transmission quality and features high

compression ratio and robustness. In ROCH mode, data can be successfully transmitted

only when the ROCH feature is supported on the transmit and receive sides. Currently, only

four ROHC formats are supported by Huawei eNodeBs. Run the following command to

check whether the ROHC is enabled.

� If a commercial UE does not support the ROHC and the ROCH is enabled on the eNodeB,

data transmission will fail. In this case, run the following command to disable the ROHC on

the eNodeB.

� MOD PDCPROHCPARA:ROHCSWITCH=OFF;


� Figure shows injection of a 130 MB packet on the downlink and the ingress traffic on the


eNodeB is 131. 28 Mbit/s (16410349 x 8/1000/1000). The calculation result shows that

the traffic volume from the server to the core network and then to the eNodeB is sufficient.

If the RX traffic is smaller than the egress traffic of the server, the ingress traffic of the

eNodeB is restricted.


� Insufficient traffic volume at the eNodeB ingress is mostly caused by insufficient bandwidth


somewhere in the transmission link.


� UDP loopback working principle is: the peer set UDP loopback, the local sends UDP


packets to the peer. The peer reverses the source address and destination address of the

received packets and sends the UDP packets back to the source station. The local side

makes the statistics by returned UDP packets, thus continuity and quality of transmission

can be detected.


� The channel/interference check is performed only after the association verification is


passed and you determine that the problem is caused by a channel fault or interference.


� Analyze a TCP problem as follows:


� If the throughput is stable but cannot reach the peak value, check the window

parameters and RTT.

� If the throughput can reach the peak value but is unstable and may suddenly fall to

a low value, check for packet loss and disorder.


� Optimization of the sending and receiving windows in Win 7


� In Windows 7, the TCP performance is automatically optimized by the TCP auto

tuning function. Start the Windows command line as an administrator and run the

following commands:

� netsh int tcp set heuristics disabled

� netsh int tcp set global autotuninglevel=normal

� If the command is executed successfully, a confirmation message is returned. The

commands take effect immediately. There is no need to restart the computer. You

can run the following command to check the current system configuration level:

� netsh int tcp show global


� Run the LST TYPDRBPUCCH command to query the SR period of each QCI.



� First start the IFTS trace and then start TCP traffic. Stop IFTS trace upon completion of the


TCP traffic and save the .tmf trace file for analysis.

� IFTS Trace is used to trace information of a UE served by a specified cell, including S1, X2

and Uu interface information at the control plane and data transmission statistics at the

user plane. The traced information can be saved automatically or manually and viewed

online or offline.

� IFTS: Intelligent Field Test System


4.oeo000040 lte traffic fault diagnosis issue 1

Engineering

Transcript of 4.oeo000040 lte traffic fault diagnosis issue 1