Hi there, nice to see you again. I'm Kate Harrison, and you should settle in and get comfy, because we're going to be learning a lot in this lesson. So far, we've learned all about the Citizens Broadband Radio Service, also known as CBRS, and we've learned how a Spectrum Access System, or SAS, manages CBRS Devices, which we call CBSDs. We've also learned that a Certified Professional Installer, or CPI, verifies the CBSD's installation parameters, and we've learned how it's absolutely crucial that a SAS has fully correct information from a CPI. Now we're going to get into the nitty-gritty details of how to find out the installation parameters of a CBSD. First, let's talk about when a CPI is required. Like, how do you know when a CPI is required to install a particular CBSD and what are the prerequisites for installing that CBSD? Remember the FCC, who created the CBRS band? Well, the FCC has also defined two categories of CBSDs: Category A CBSDs and category B CBSDs. A certain CBSD model might fall into either category depending on the installation situation. If a CBSD meets the category A requirements, then you can declare it as a category A. Otherwise, you'll need to declare it as a category B. Both categories of CBSDs have to register and regularly communicate with the SAS if they want to transmit in the CBRS band, and neither type can be used on a moving object, like a plane or a car. CBSDs need to always stay in the location that's reported to the SAS. Here are the key differences. Category A CBSDs only require CPI installation if the CBSD can't determine its own location, like if there is no built-in GPS or the GPS signal is weak, whereas a category B CBSD needs the CPI to install it no matter what. Category A CBSDs can be used indoors, but category B CBSDs are outdoor-only. You can install a category A CBSD outside, but only if it's below a certain height limit. If it's too tall, it'll have to be considered a category B CBSD because category B CBSDs have no height limit. Category A CBSDs operating outdoors have a height limit of six meters. But what do we mean by height in this case? Height here means the H-A-A-T or HAAT, which stands for height above average terrain. It's a measure of how high an antenna site is above the landscape around it. The larger the HAAT, the more interference the device can cause, so we need CPIs to ensure that the SAS has the most accurate information about those CBSDs. Note that the HAAT is computed by looking at the far-away surroundings of the CBSD between 3 kilometers and 16 kilometers in all directions. The actual immediate surroundings of the CBSD aren't as important, so they're not part of how the HAAT is calculated. Category B CBSDs have no height restrictions, but it's important to note that a CBSD that's mounted at a higher location might get less spectrum granted from the SAS. A CPI is not actually reporting the device's HAAT to the SAS. The CPI reports the device's location and height above ground level, and the SAS does its own calculation of the HAAT. But the CPI needs to know a device's HAAT in order to know whether to register it as a category A or B. There is no actual penalty for trying to register a device with a HAAT over six meters as a category A CBSD. But the SAS will reject the registration request and it'll have to try registering the CBSD again as a category B CBSD, even if it would otherwise be considered a category A CBSD. Let's take a look at this drawing for some examples. If you place the CBSD at the bottom of a valley, you'll probably get a negative HAAT. If you place it on the top of a mountain, it's going to come out with a positive one. So how do we calculate the height above average terrain? Well the good news is, this is one you don't have to do all on your own. There are online calculators, like the one on the FCC's website, that you can use when you're estimating the HAAT for a CBSD. The first step in calculating the HAAT is to determine the elevation above sea level of the location at which you are installing the antenna. The easiest way to do this is to use an online tool, such as the one that we've linked on this slide, which takes the latitude and longitude as its input. But these tools will only tell you the elevation of the ground at this location. In order to determine the elevation of the antenna, you need to add its height above ground level to the result that you get from the calculator. If you're unsure, we'll have some tips on how to measure this later since you'll also be providing the height above ground level to the SAS. Now you have the height above mean sea level and you're ready to plug that into the FCC's calculator. If you get a value less than six meters, you may be able to classify the CBSD as a category A device. Otherwise, you'll need to classify it as a category B CBSD. Keep in mind that the SAS may be using slightly different terrain data in its calculations, so it may reach a slightly different conclusion. In most cases, the difference won't affect the device category, but the worst thing that's going to happen is having to start a category A registration over as a category B.
