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Interpretation of Over the Air Measurement Results

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This section contains expected result values and possible causes of error if the expected results are not met.

Freq (Frequency)

If you are in the channel mode, verify that the correct channelization and channel number are set.

Freq Error (Frequency Error)

The frequency error of the analyzer should be <1 kHz. If the frequency error is greater than this, there could be a possible malfunction in the base station equipment. Other possible explanations for Frequency Error include:
the effects of multipath transmission
pilot dominance
failure of the base station to lock onto a GPS signal
Before performing a procedure to check the base station equipment, check to ensure that the test set is performing a correct measurement. You can do this by reviewing the frequency reference settings for the test set (refer to "Setting the Transmitter Reference")
Ensure that these settings are correct, and that the test set shows reference lock. Lastly, make sure the test set has been powered on, and has been locked for at least 15 minutes.
If the error is still occurring after performing the above procedures, you will need to check the Base Station equipment for a source of the error. You can also verify that the base station is malfunctioning by turning off its modulation hardware and performing a frequency measurement on the Base Station carrier signal in the spectrum analyzer mode of the test set (refer to "Performing a Basic Spectrum Analyzer Measurement")
You can use the Frequency Limits setting to make your analyzer indicate automatically whether or not a signal has exceeded the pre-defined limits you set.

Scramble Code

If the Scramble code is not as expected, it could be due to an incorrect Base Station setting or to incorrect positioning of the test set. Use of the "strongest pilot" display to position the test set. If the correct Scrambling code cannot be located, check the base station settings.

Noise Floor

An unexpectedly high noise floor could be due to interfering signals.
If you have not already done so, you can reduce the noise floor by activating the IF Equalizer (See "Setting the IF Equalizer" on page 516.)

Carr Feedthru (Carrier Feedthrough)

A good Carrier Feedthrough level is less than -25 dBc. The 3GPP standard does not specify Carrier Feedthrough; however, this measurement provides an additional tool to troubleshoot the base station's transmitter.
In the frequency domain, Carrier Feedthrough can show up as an energy spike that can be seen on the spectrum analyzer by closely spanning into the top of the W-CDMA or W-CDMA (with HSDPA) signal. The effects of Carrier Feedthrough can also show up as higher noise levels on the Code Domain Power screen. Carrier Feedthrough can be caused by the lack of isolation across the mixer and cavity of the transmitter's I/Q modulator.

EVM Pilot and EVM Comp (Pilot (CPICH) and Composite Error Vector Magnitude

An unexpectedly high EVM could be due to interfering signals, carrier feedthrough, transmitter I/Q modulator, or signal path problems.
If you have not already done so, you can reduce the noise floor by activating the IF Equalizer (See "Setting the IF Equalizer" on page 516.)

PCDE (Peak Code Domain Error)

An unexpectedly high PCDE could be due to interfering signals, carrier feedthrough, pilot dominance, or multipath power. If these are all correct, check for transmitter I/Q modulator or signal path problems.

Utilization

The Utilization metric provides an instantaneous reading of the percentage of the traffic channels currently being used. More meaningful information is provided by the Peak and Average Utilization metrics gathered over a 10 to 15 minute interval.

Pk Util (Peak Utilization)

If the Peak Utilization of this base station is greater than 65%, this is a warning that peak traffic rates at this base station are getting very high. It is possible that calls could be getting blocked or dropped.

Avg Util (Average Utilization)

If the Average Utilization of this base station is greater than 45%, the base station is carrying a great deal of traffic. Service providers may want to consider expanding their network infrastructure to support higher system (call) demands.

Chan Pwr (Channel Power)

If the Channel Power level is not as expected, check pilot dominance and the number of Scramble codes visible. All visible sectors will contribute to channel power. Also, check Amplifier Capacity and Utilization as they could have exceeded the maximum capacity. A high power data call could be indicated by a very wide and tall bar.

CPICH (Common Pilot Channel)

CPICH will vary with distance from the base station and clear line of sight to the antenna. If the CPICH is not as expected, check pilot dominance and base station settings (ratio to other control channels should be good).

Amp Cap (Amplifier Capacity)

The Amplifier Capacity metric provides an instantaneous reading of how much of the amplifier's capacity is currently being used. More meaningful information is provided by the Peak and Average Amplifier Capacity metrics gathered over a 10 to 15 minute interval.

Pk Amp Cap (Peak Amplifier Capacity)

If the Peak Amplifier Capacity is greater than 100%, the traffic at this base station has caused the base station amplifier to exceed its maximum power rating. This is not desirable as this problem can result in system degradation or damage to the amplifier.
You can get an indication of how often the amplifier capacity is being exceeded by watching the Amplifier Capacity measurement. This is an instantaneous measurement of the amplifier capacity.

Avg Amp Cap (Average Amplifier Capacity)

If the Average Amplifier Capacity is greater than 85%, the base station power amplifier is close to its maximum power limit. Further increase in traffic on this base station could cause system performance problems or damage to the power amplifier. You should notify your RF Engineering Department as soon as possible.

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