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eNodeB LTE V100R007 Antenna & Feeder System Fault Analysis and Troubleshooting Confidential Information of Huawei. No Spreading Without Permission

LTE Interference troubleshooting guide

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Page 1: LTE Interference troubleshooting guide

eNodeB LTE V100R007 Antenna & Feeder System

Fault Analysis and Troubleshooting

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Page 2: LTE Interference troubleshooting guide

� DMRS: demodulation reference signals

eNodeB LTE V100R007 Antenna & Feeder System

Fault Analysis and Troubleshooting

� RSSI: Received Signal Strength Indicator

� In LTE, RSSI is reported by baseband to help judge whether there is UL interference.

� How to start the task in U2000:

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Page 3: LTE Interference troubleshooting guide

� Value range of RSSI can be analyzed in the same way as RTWP.

eNodeB LTE V100R007 Antenna & Feeder System

Fault Analysis and Troubleshooting

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Page 4: LTE Interference troubleshooting guide

� Parameters explanation in ADD CELLSIMULOAD

eNodeB LTE V100R007 Antenna & Feeder System

Fault Analysis and Troubleshooting

� Configure Index:

� Indicates the index of a simulated load configuration. One eNodeB can store a

maximum of 10 simulated load configurations. They are identified by indexes

ranging from 0 to 9 and correspond to RB usage thresholds 10% to 100% at a

step of 10%. For example, the RB usage thresholds for simulated load

configurations 1 and 4 are 20% and 50%, respectively. Alternatively, you can

manually specify the RB usage threshold for a simulated load configuration by

setting the SimuLoadRbThd parameter in MOD SIMULOAD.

� PIM can be troubleshot by adjusting the configure index to adjust the load level.

� SimuLoad transmission mode:

� Indicates the transmission mode adopted by the simulated load configuration. Its

value can be set to TM1, TM2, TM7(TM7), and TM8. For an FDD cell, TM2 is set;

for beamforming in TDD cells, the other transmission mode is used.

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Page 5: LTE Interference troubleshooting guide

� FFT frequency scan can be taken as an assisted way for PIM determination. There is no

eNodeB LTE V100R007 Antenna & Feeder System

Fault Analysis and Troubleshooting

abnormal frequency scan result only belong to PIM, because some other interference

source also will cause the same abnormal frequency scan result as PIM interference.

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Page 6: LTE Interference troubleshooting guide

� How to start the task in Web LMT:

eNodeB LTE V100R007 Antenna & Feeder System

Fault Analysis and Troubleshooting

� Scan mode:

� High-resolution Online Frequency: An online carrier-level scan. Signals in specified

channels are scanned for all established cells on a carrier of a specified radio access

technology (RAT).

� Broadband Online Frequency: An online channel-level scan. Signals in specified channels

are scanned for all established cells.

� Broadband Offline Frequency: An offline channel-level scan. Signals in specified

channels within the bandwidth of the duplexer are scanned.

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Page 7: LTE Interference troubleshooting guide

� Origination of narrow-band interference include:

eNodeB LTE V100R007 Antenna & Feeder System

Fault Analysis and Troubleshooting

� Uplink signals from narrow-band system, e.g, GSM system

� PIM interference caused by narrow-band system

� Other interference source, like the single tone signals generated by some device.

� When channel isn’t configured, BBU itself will generate single tone signal, which isn’t

interference, as the rightest spike in the figure.

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Page 8: LTE Interference troubleshooting guide

� Origination of broad-band interference include:

eNodeB LTE V100R007 Antenna & Feeder System

Fault Analysis and Troubleshooting

� Repeater interference

� barrage jamming

� PIM interference

� Other broad-band interference signals

� Interference caused by repeater is a kind of common broadband interference. It will cause

the power of the whole band rising. As below figure shows:

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Interference caused by repeater in indoor coverage scenario

Page 9: LTE Interference troubleshooting guide

� Interference detection test is a kind of Huawei antenna & feeder system self test. It can be

eNodeB LTE V100R007 Antenna & Feeder System

Fault Analysis and Troubleshooting

used during site deployment as engineering acceptance.

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Page 10: LTE Interference troubleshooting guide

� The antenna channel must be in TX/RX mode, and the RF module transmits two signals with 20 W.

The frequencies of the two signals are test frequency f1 and test frequency f2.

eNodeB LTE V100R007 Antenna & Feeder System

Fault Analysis and Troubleshooting

The frequencies of the two signals are test frequency f1 and test frequency f2.

� f1 and f2 can be determined in the following ways:

� If f1 and f2 are set manually, it is recommended that f1 and f2 be set as the highest and

lowest frequencies of the transmit frequency band allocated by the operator.

� If they are not set manually, the system will choose two frequencies for them according to

the capacity of the RF module.

� Either way should enable the generated 3-order, 5-order, 7-order and higher order IMPs within the

RX band allocated by the operator. The detection is started based on f1, f2, and the thresholds for

the IMPs. The thresholds can be set according to the requirements for inter-modulation.

� 2-Tone Measurement

� Two signals with the power of 20 W are transmitted from the channel of a specified antenna on

frequencies f1 and f2. Check whether the level of PIMs within the RX band meets the requirement

of intermodulation suppression.

� Duration: Detection on each antenna port takes 95 seconds.

� Sweep Measurement

� The principle of this method is the same with 2-tone measurement, but multiple pairs of frequencies

are used. Assume that the start test frequency (f1) is the lowest and the end test frequency (f2) is

highest of the test bandwidth. Frequencies are selected as follows:

� Step1: fix f1, the paired frequencies are: f1, f1+∆f; f1, f1+2∆f; f1, f1+3∆f; …; f1, f1+n∆f.

� Step2: fix f2, the paired frequencies are: f2-∆f, f2; f2-2∆f, f2; f2-3∆f, f2; …; f2-n∆f, f2.

� Duration: It depends on the detection bandwidth and ∆f. For example, if the maximum

instantaneous bandwidth (IBW) is 35 MHz and ∆f is 0.5 MHz, the duration is about 20 minutes.

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Page 11: LTE Interference troubleshooting guide

� Service-based IM detection takes samples of six periods, which alternate between

eNodeB LTE V100R007 Antenna & Feeder System

Fault Analysis and Troubleshooting

transmitting simulated load status and non-transmitting simulated load status.

� Totally there are 3 groups of test. Each group is composed of one simulated load status

and one non-simulated status, between which wait 3 seconds until the transmit power of

RF modules decreases to a stable value.

� Delta threshold (parameter “Delta threshold” in MML) indicates the difference of the

RTWP between full power and no power during the test in UMTS and LTE modes. If the

difference is greater than this threshold, IM interference exists.

� Service rate threshold (parameter “Duty threshold” in MML) Indicates the threshold of the

current transmit power to the maximum transmit power for starting an online IM

interference test. For RF module that works in UMTS or LTE mode, when the ratio of the

current transmit power to the maximum transmit power in a cell exceeds this threshold, a

failure message is returned, if the online IM interference test is started on.

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Page 12: LTE Interference troubleshooting guide

� How to start on U2000:

eNodeB LTE V100R007 Antenna & Feeder System

Fault Analysis and Troubleshooting

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Page 13: LTE Interference troubleshooting guide

� How to start monitoring interface:

64eNodeB LTE V100R007 Antenna & Feeder System Fault Analysis

and Troubleshooting

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Page 14: LTE Interference troubleshooting guide

� DTP test is used after PIM interference is confirmed. This test can help to determine

eNodeB LTE V100R007 Antenna & Feeder System

Fault Analysis and Troubleshooting

whether the faulty connection is on or below the antenna tower, to eliminates the need

for unnecessary maintenance on the tower and therefore reduces the maintenance cost.

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Page 15: LTE Interference troubleshooting guide

� FDR (Frequency Domain Reflectometer) is originally an application in military, nowadays, it

eNodeB LTE V100R007 Antenna & Feeder System

Fault Analysis and Troubleshooting

is applied to the filed of commercial communication test.

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Page 16: LTE Interference troubleshooting guide

� How to start DTP test on Web LMT

eNodeB LTE V100R007 Antenna & Feeder System

Fault Analysis and Troubleshooting

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Step 2. DTP test task selection

Step 3. Parameter setting

Step 1. enter Web LMT monitor interface