Criteria for Making Valid 1xEV-DO Over Air Measurements
The first step in making valid 1xEV-DO 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 1xEV-DO signal. 1xEV-DO over air measurements will experience interference from other 1xEV-DO signals on the same RF channel and from multipath echoes. The code domain power view measures two key parameters to indicate these effects:
NOTE It is important to remember that the pilot dominance is always measured against the strongest signal. If you have specified your channel of interest manually, this channel might not necessarily be the strongest.
- Pilot dominance-The difference between the useful energy of the strongest pilot channel and the combined energy of the lower energy active pilot channels (expressed in dB). Ideally, this value should be very large ( 16 dB).
- The E7495A/B test set includes up to nine lower energy active pilots in the pilot dominance calculation. In live testing of 1xEV-DO networks, however, it is unlikely that you will have as many as nine interfering pilots.
The table below shows the quality of the over air code domain measurements with respect to pilot dominance and multipath power.
- 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.
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
> 8 dB
< 0.7 dB
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.
In general, you should always use a preselector filter for the band of interest to prevent strong signals from swamping out the signal of interest. Agilent offers these preselectors and antennas:
- Option 810-Cellular downlink band preselector and antenna
- Option 811-PCS downlink band preselector and antenna
- Option 812-Korean PCS downlink band preselector and antenna