1. What is Huawei CHR? Huawei CHR is a trace logging feature in RNC and NodeB. It collects call and cell information, radio measurement and messages for all calls in the network.
2. What does the CHR file contain? The RNC CHR file contains following information: •
User call log—Information about the call messages such as call setup, RAB setup, Handover and Call Release.
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Cell Log—User load and Power measurement of the cell over time which includes RTP% and RTWP.
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Internal RNC log—Internal signaling information which less interesting for RF engineer.
3. Can the CHR collect every call in the RNC? Unlike the normal call trace, the CHR log contains call trace from every call in the RNC.
4. What user call information is captured in the CHR ? The RNC CHR file contains following user call information: •
Call Start information such as RRC Establishment cause, Ec/No, serving cell and propagation delay. It also captured IMSI for user identification and IMEI for phone identification.
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Handover information for Soft-Handover, Hard-Handover and Inter-RAT Handover such as target cell and RF measurement
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Radio Bearer setup information for both CS and PS calls such as RAB type and requested but-rate.
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Call Release information such as release cause, fault description and error codes.
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RF measurement from Measurement Report such as Active Set and Monitored Set Ec/No and RSCP and GSM cell RSSI (Refer Figure 1)
What is Huawei CHR?
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Figure 1 Serving Cell & Neighbours Measurements from CHR data
Figure 2 Layer 3 Messages from CHR
What user call information is captured in the CHR ?
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5. How to enable CHR recording? CHR file is automatically collected in the RNC. The CHR file can be found in the RNC BAM folder /bam/common/fam/famlogfmt. There are two type of logs: DEBUG and UCHR. Only UCHR log contains call trace data. The filename would look like this “BSC0110_[UCHR]00Log20110626170002_20110626170026.log.zip” As for NodeB CHR log, uses "SET CHRSW" MML command to initiate the recording.
6. How can CHR help me to improve the network quality? Since CHR log contains call information from the real users in the network, it allows RF Engineer to perform various optimization tasks. Here is the list of optimization tasks that can be performed through analyzing CHR file: •
Abnormal Call Release analysis—RF Engineer can go through each dropped or blocked call in the network and identify the fault result and call sequences that lead to the abnormal release.
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Missing Neighbour Identification—Using the Detected Set information, RF Engineer can identify any missing neighbour in the network.
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Pilot Pollution Analysis –The measurement report form all UE allow RF Engineer to identify interference in the network.
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Over-shooting cell analysis—Using the propagation delay during the call setup together with the RF measurement, RF Engineer can identify cells that cover too large area.
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VIP Analysis—Using the IMSI, RF Engineer can find out the cause of complain from the VIP customer.
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Phone Model Analysis—Operator can study the performance of each phone in the network.
7. What tool can I use to analyze CHR log? Since CHR file is in a binary format, it requires specialized application to post-process the file before you can analyze the data. Some of these application are as following: •
