Anritsu Spectrum Master MS2720T, Руководство пользователя

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3-9 EVDO Measurement Descriptions EVDO Signal Analyzer
3-16 PN: 10580-00235 Rev. D 3GPP2 MG
3-9 EVDO Measurement Descriptions
Pilot & MAC Power
The Pilot & MAC power shows the average power of the Pilot and MAC Channels. It is an
absolute number that is expressed in dBm or Watts.
Active Data Power
Active Data Power is the average power of the Data Channel. When the slot is active, the data
power should be very similar to the MAC & Pilot power (less than 2.5 dB difference). When
the slot is idle, the Active Data Power should be at least 7 dB below the MAC & Pilot power if
the instrument is connected directly to a base station.
Channel Power
During an active slot, Channel Power should be similar to Pilot & MAC power and should
also be similar to Active Data Power. During an idle slot, channel power should be somewhere
between the Pilot & MAC power and Data Power, because it is a weighted average of the two.
When measuring an EVDO station with live traffic, channel power will vary according to how
busy the downlink is, because channel power also depends upon the percentage of idle slots
and active slots in the captured sample.
Noise Floor
Noise floor is the average power of the inactive MAC channels, relative to the total MAC
channel power. It is expressed in dB. When connected to a good EVDO source, the noise floor
should be -31.5 dB or below. When noise or distortion is present (for example, in an
over-the-air measurement), the noise floor can be considerably higher.
Freq Error
Frequency error is the difference between the received center frequency and the specified
center frequency. This is only as accurate as the frequency reference that is being used and is
typically more useful with a good external frequency reference or GPS.
Data Modulation
The instrument can determine the data channel modulation type automatically. EVDO data
channel has three modulation types: QPSK, 8PSK, and 16QAM. “Idle” is displayed when the
slot is idle.
PN Offset
Each EVDO base station is identified by a unique PN Offset in its pilot signal. This is similar
to CDMA.
Tau
Tau measures the time delay from the input trigger to the “start of a slot.” This means that
Tau can be much larger than what is commonly seen in CDMA if the signal is not
synchronized to the trigger.
Note
The EVDO PN must be aligned with the start of an EVDO slot, in addition to
referencing the external trigger or GPS signal. Therefore, when the user connects
an external trigger that is poorly aligned with the EVDO signal slots, the instrument
may report a Tau value that is very large in magnitude, in order to give the best
possible PN Offset estimation.
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