Technical data

Chapter 8 221
CDMA Over Air
Using the CDMA Over Air Tool
CDMA Over Air
Criteria for Making Valid CDMA Over Air Measurements
The first step in making valid CDMA over air measurements is to identify a target
base station to measure. Then, for your measurements to be valid, you must find a
location near the target base station with a sufficiently strong CDMA signal. CDMA
over air measurements will experience interference from other CDMA signals on
the same RF channel and from multipath echoes. The code domain power view
measures two key parameters to indicate these effects:
• Pilot dominance—The difference between the energy of the strongest pilot
channel and the combined energy in the second and third strongest pilot
channels (expressed in dB). Ideally, this value should be very large (> 16 dB)
• Multipath power—The amount of power, of the dominant pilot signal, that is
dispersed outside the main correlation peak due to multipath echoes (expressed
in dB). Ideally, this value should be very small (< 0.1 dB). Multipath power is
the result of portions of the original broadcast signal arriving at the receiving
antenna out of phase with the main power of the original signal. This can be
caused by the signal being reflected off objects, such as buildings, or being
refracted through the atmosphere differently from the main signal. These out of
phase signals can cancel power from the main signal or appear as noise
interference at the receiver.
The table below shows the quality of the over air code domain measurements with
respect to pilot dominance and multipath power.
The default measurement limits for pilot dominance and multipath power are set to
give “fair” measurement quality. If these limits are met, the pilot dominance and
multipath power values will be displayed in green. When the pilot dominance and
multipath power parameters are outside the acceptable limits, the parameters will
turn red. If this occurs, you must move to a different location that meets the “fair”
criteria defined above.
Table 8-1 Over Air Code Domain Measurement Quality
Measurement Quality Pilot Dominance Multipath Power
Very good > 16 dB < 0.1 dB
Fair > 10 dB < 0.4 dB
Marginal > 8dB < 0.7dB