When a CBSD registers with the SAS, its installation parameters need to be verified and signed by a CPI. We have noticed some inaccuracies in some of the installation parameters, and this list summarizes some of the most common mistakes.
We suggest you double check your existing devices, and pay close attention when installing new devices, as future changes of any of these parameters requires a re-registration of the device with the SAS.
- A negative number means that the device is tilted up; a positive number means that the device is tilted down
- The 450i integrated and 450m APs have a built-in 2 degrees electrical downtilt
- If you install the 450i/450m AP with a 0-degree mechanical downtilt, enter 2 degrees in the field (this accounts for the electrical downtilt)
- If you install the 450i/450m AP with a 2-degree mechanical uptilt, enter 0 degree in the field (the mechanical uptilt compensates for the electrical downtilt)
- If you install the 450i/450m AP with a 2-degree mechanical downtilt, enter 4 degrees in this field (the mechanical and electrical downtilts add up)
- The limit of the mechanical uptilt of 450i/450m is 5 degrees; this means that no values should be lower than -3 degrees in this field
- Antenna height
- Double check the height type and height value: a common mistake is to select AMSL (Above Mean Sea Level) as antenna height type, but enter the numerical value as if it was AGL (Above Ground Level).
- When calculating the height as AMSL do not forget to add the mast height
- Note that AMSL is the default value in the Excel spreadsheet. If you want to enter the value as AGL, do not forget to change the height type
- For some devices, the antenna beamwidth and gain depend on the actual device (if it is connectorized or integrated, if it has an additional reflector or not, etc.), but for some devices there is only one correct option:
- For the 450m the beamwidth is 90 degrees, the integrated gain is 16 dBi, and the external gain is 0dBi.
- For the 450b high-gain SM the beamwidth is 12 degrees, the integrated gain is 20 dBi, and the external gain is 0dBi.
- For the 450i integrated AP or SM the beamwidth is 17 degrees, the integrated gain is 19 dBi, and the external gain is 0dBi.
- For the 450 integrated SM with no reflector the beamwidth is 55 degrees, the integrated gain is 8 dBi, and the external gain is 0dBi.
These and more antenna options are either automatically populated in the spreadsheet when a device is selected, or they are listed on the right-hand side in the gray section.
- Sanity check the antenna parameters. For example, an antenna cannot have a 55-degree beamwidth and a 20 dBi gain.
- The antenna gain the device registers with is the sum of the integrated gain and the external gain. The integrated gain is always automatically populated in the spreadsheet when a device type is selected; the external gain is manually entered, because a device could be connectorized, or a reflector could be added. Do not copy the internal gain in the external gain option; a common mistake is for example with the 450b SM copying the 20 dBi gain automatically populated in the integrated antenna column into the external gain column. The device would then register with a 40 dBi antenna gain instead of the 20 dBi correct value.
Note that reporting the wrong antenna gain not only violates the CPI responsibilities, but it also may limit spectrum availability when the SAS calculates the possible interference footprint of a device. The SAS may reduce the grant’s EIRP if it calculates the device transmission with an incorrect (higher) antenna gain.
- Double check the accuracy values. Any value is valid here, as long as it is lower than the actual delta from the reported coordinates.
As a reminder, if the coordinates are accurately know, it is more beneficial to have the accuracy values as small as possible, as the SAS is going to assume the worst case propagation scenario within the circle created by the accuracy values.
However, if a device is registered with the tool a day ahead of installation, using larger accuracy values gives the installer more flexibility in where to actually install the device. The grant would still be valid (no re-registration is required) if the device coordinates are slightly off compared to the ones used for registration, but still within the accuracy limits.