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Communication System Planning: Lab Report 3

The document discusses several questions related to communication system planning and GSM network monitoring. It addresses topics like co-channel interference, carrier-to-adjacent ratio (C/A), scanner bar charts, system information messages, call setup messages, measurement reports, and handovers. Key points include that high co-channel interference decreases speech quality (SQI) and increases RxQual, C/A measures adjacent channel interference which can be avoided using sharp filters and channel separation, and decreasing RxLev FULL serving leads to handover with the value increasing after a successful handover.

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77 views14 pages

Communication System Planning: Lab Report 3

The document discusses several questions related to communication system planning and GSM network monitoring. It addresses topics like co-channel interference, carrier-to-adjacent ratio (C/A), scanner bar charts, system information messages, call setup messages, measurement reports, and handovers. Key points include that high co-channel interference decreases speech quality (SQI) and increases RxQual, C/A measures adjacent channel interference which can be avoided using sharp filters and channel separation, and decreasing RxLev FULL serving leads to handover with the value increasing after a successful handover.

Uploaded by

Aqsa_Malik_3765
Copyright
© Attribution Non-Commercial (BY-NC)
We take content rights seriously. If you suspect this is your content, claim it here.
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COMMUNICATION SYSTEM PLANNING

LAB REPORT 3
NC AQSA MALIK NC MARYAM TANVEER NC MARIAM TARIQ NC SARAH MAHMOOD

QUESTION NO.1 : What is the most common indicator of co channel interference? Take a snapshot of GSM line chart showing this scenario. How SQI and RxQual is affected if the interference is high. The most common and general indicator of co channel interference is carrier-over- interference ratio C/I. It is the ratio between the signal strength of the current serving cell and the signal strength of undesired (interfering) signal components. The C/I measurement function enables the identification of frequencies that are exposed to particularly high levels of interference, which comes in useful in the verification and optimization of frequency plans.

If the interference is high, speech quality index SQI will be low since it is based on BER, FER, handover and codec. However RxQual will be high indicating high BER. QUESTION NO.2: What is C/A? How adjacent channel interference can be avoided? C/A is the measure of adjacent channel interference. The carrier-to-adjacent ratio is defined as the signal-strength ratio between a serving carrier and an adjacent carrier. It is calculated according to the following formula: C/A (dB) = Serving signal strength (dBm) Adjacent signal strength (dBm) For example, if the serving carrier ARFCN is 20 and the adjacent ARFCN is 19, the corresponding C/A value is called C/A-1.

It can be avoided by: -using sharp cut off filters - Maximize channel separation by not assigning adjacent channels in a cell QUESTION NO.3: Open the GSM scanner bar chart and event window. What does the scanner bar chart is showing? When a hand over occur note down the RxLev of the current channel and the one to which the call is handed over to. The scanner bar chart is showing Strongest Scanned RxLevel and Scanned RxLevel in dbm.

QUESTION NO.4: Analyze the system info messages. Type 1: Transmitted on BCCH to all the MS in a cell, Giving RACH info and ARFCN available in a cell

Type 2: Transmitted on BCCH to all the channels in the cell giving the BCCH info of neighboring cells and
RACH control parameters

Type 3/4: Transmitted on the BCCH channel to all MS in a cell giving Info about location area identification and cell id, cell options and RACH data

Type 5: Transmitted on SACCH by the network to all the MS in the cell telling the BCCH ARFCN of the
neighboring cells to be monitored by the MS

Type 6: Transmitted on SACCH by the network to all the MS in the cell telling cell info and DTX indicator

QUESTION NO.5: Open the event window and the layer 3 messages window list down all the messages exchanged between MS and the BTS when a call is set up start from the idle mode to the call established event.

It can be seen that there are 5 events from idle mode to call established mode. Idle mode layer 3 messages:

Call attempt mode layer 3 messages:

Dedicated mode layer 3 messages:

Call setup and call established mode layer 3 messages:

Handover: Handover event has four layer 3 messages.

QUESTION NO.6: Open up a measure report being transmitted , what information does it contain?

QUESTION NO.7: Monitor the RxLev FULL serving and the neighbor values, in 4,5 consecutive measurement reports, what happens when the RxLev FULL serving value decreases?
When the RxLevel FULL serving decreases it shows the need of handover. After a successful handover the RxLevel FULL serving increases than its value before the handover. It is shown in following screenshots.

Measurement report before handover:

Measurement report after handover:

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