Technical data

112 Chapter 3
1xEV-DO Analyzer and Over Air Test
Interpretation of 1xEV-DO Tx and Over Air Analyzer Measurement
Results
1xEV-DO Analyzer and Over Air
Test
Est MAC Rho
The 1xEV-DO access network standard specifies that Rho must be greater than
0.912. Typical values for a healthy access network are greater than 0.94.
Rho failures can indicate problems in:
• Compression in linear amplifiers
• Magnitude and phase errors in the IQ modulator
• Phase non-linearity (group delay)
• Spurious signals in the transmission path
• Carrier feedthrough
Because the uncorrelated power appears as interference to the access terminals, poor
Rho performance will affect the sector's capacity. The added interference can
require that the signal on traffic channels be raised to overcome the interference.
This may, in turn, be seen as further interference. At some point, the site will have to
shed calls in order to supply the remaining calls with enough signal versus the
interference in the system.
Max Inactive Ch
According to the 1xEV-DO standard, the CDP in all inactive channels must be at
least 27 dB below the total MAC power.
If this value exceeds 27 dBc, compression may be occurring in the base station
power amplifier or there may be errors in the base station IQ modulator.
Noise Floor
The light gray bars on the CDP trace display are noise. While they appear to be
channels on the trace and are referred to as noise channels, they are not real
1xEVDO channels. They represent the noise energy in the inactive displayed code
channel. The average level of the top of these noise bars represents the CDP Trace
noise floor, and is the figure reported here.
The noise floor level can be influenced by many conditions one of which can be the
existence of high power from another CDMA base station or such things as loose
RF connections. It is desirable to reduce the noise floor as much as possible before
making measurements. If you have a strong signal on the metrics display but still
show a high noise floor, then a problem may exist in the base station.
Data Modulation Type
The Data Modulation Type measurement returns the highest modulation detected