Join Mike Meyers for an in-depth discussion in this video Cellular configuration, part of CompTIA A+ (220-902) Cert Prep: 5 Mobile Devices.
- The CompTIA A+ has tons and tons of cellular terms, like PRL and IMEI and IMSI, and just a whole bunch of alphabet. So in this episode, what we're going to do is get all that knocked out. These terms are used by cellular technicians to get systems up and to maintain them. Now, in order to understand all this stuff we've got to break cellular down a little bit. So the number one thing I want to do for starters, is that we need to break all types of cellular phones down into two types.
There's CDMA and there's GSM. I don't know what those stand for. Put them down there for me. Okay, great. Now, CDMA is a little bit of an older technology. It's really, this was invented in the United States and it's got a lot of presence in the United States and in South America. GSM is a little bit newer, but it pretty much dominates the world right now. I'd say 90% of all cellular phones are GSM.
If you're in Europe, or in Africa or in Asia, you've probably never seen a CDMA phone and you probably never will. So for those of you overseas, sorry, but the A+ covers CDMA and we need to as well. There's a couple of things that separate CDMA from GSM. First of all, GSM phones have the famous SIM card. The SIM card stores personal information about the user themselves and it can be moved from phone to phone if your phones are unlocked, so that you can actually pick up a new phone.
CDMA doesn't have any kind of SIM. Some of the last versions of CDMA had a SIM-like card, but it never really took off. There is no SIM in this particular one. I get the CDMA device from my wireless carrier and that's what I use. Okay, now once you're comfortable with the fact that there's CDMA and GSM, there's a couple terms of terms that don't really mean much to us. Like you'll hear people talk about 3G and 4G and LTE. Now, though are important terms in terms of speed and capability, but as a technician, to get something connected and get it up and running, it's all CDMA and GSM.
So the best way to go about this is let's go through each phone's settings, and we're actually going to show you some scary backdoor configuration stuff. So let's start with CDMA. Here on my CDMA phone, we're going to click on settings, and usually I have to scroll all the way to the bottom. There it is. About Phone. Now, this can be different for different versions. I'm doing Android here and so it can vary. On this one, it's status. Now, the first thing I want you to look at way down here is the PRL version.
What we're looking at here is that these little phones have firmware. They don't have hard drives. They've got firmware, And sometimes this stuff has to be updated. So on a CDMA phone, when you would go through an update what would be updated was known as a product release information, or PRI. Now, there's a lot of stuff that gets updated and that's not covered on the A+, but one thing that is, is that PRL. PRL stands for Preferred Roaming List. When this phone is within his little network, in this case, I think it's Verizon here in the United States, he can just jump from cell to cell happily.
However, if he gets outside of his coverage area, one of two things are going to happen. Either A, you don't get to talk on the phone, or number two, he's made agreements with other wireless carriers that will take on these calls, usually for a slight extra charge, and that's called roaming. Now, if he comes up to a cell tower where he doesn't have his coverage, but there might be two, three, four other carriers, how does he know which one to pick? And that's where the preferred roaming list comes into play, so it's a fixed list on this system.
With these CDMA phones, a bad PRL can be a problem, so it's a very standard thing to update your PRL. So let's update it. Now every phone has a different way to go about this update. On this one particular phone, you actually just dial in, so on this carrier, I have to dial this specific code. Now keep in mind, this may not work for your CDMA phone, but it does for mine. First of all, look how the screen changes. This is not a regular phone. A regular screen.
- [Operator] Wireless programming. (speaking in a foreign language) To program or activate your phone, press one. Update your roaming capabilities, two. - [Mike] So to update my roaming capabilities, I press two. (instrumental music plays while on hold) I love the hold music.
- [Operator] Your roaming capabilities have been updated successfully. - [Mike] Yay. - [Operator] Thank you for calling. - [Mike] You're welcome. (beeping) Okay, well that explains firmware update, but now there's a lot of other stuff to configure. In particular, when you're dealing with cell phones, there are two issues you're always going to have to deal with. Number one, is some identifier that identifies this particular phone and then number two, some identifier that identifies you. Now these differ between CDMA versus GSM, so let's do this first with CDMA.
So let's go back into settings and back down to about phone, and let's take a look at the status on this one. Okay, now there's a number of different values here and I want to go through all of these. First of all, there's your phone number. That's easy, so feel free to call me anytime. I'll probably have this phone gone by the time you read this. Okay, the first one is the ESN. ESN stands for Electronic Serial Number. This was the original way that we identified individual phones.
Now the problem with ESN, if you take a look at that value, you'll see it's relatively short and that was a problem. We literally ran out of ESNs, so starting oh, I guess, 10 years ago or so, we came up instead with the MEID. MEID stands for Mobile Equipment Identifier and that is really the value that these phones use to identify themselves to the network. The reason they keep ESN in there is for backward compatibility, if they're roaming in an old network in the middle of Nebraska or something, sorry Nebraska, and they don't have the latest equipment they can be backwardly compatible with it.
So the MEID is shown in two values here, both in HEX and in Decimal. Okay, so the last value to talk about is MIN. MIN stands for the Mobile Identification Number. The MIN value is what your phone uses to identify itself once it gets within a certain geographical area. So once it gets within a geographical area, it kind of introduces itself and says, "Hi, this is my MEID," but from then on, as long as it stays in this certain geographical area, it's going to identify itself, not by the MEID, but instead, by the MIN.
Now, the important thing to all these settings is that more than anything else, you're going to be dealing with activation of these phones and you're going to have to deal with occasional firmware updates. Now, we've done the firmware update. Activation is done almost the exact same way on a CDMA phone. The important thing here is that you're probably going to need that MEID. It's actually important to store that MEID. In fact, it's so important that it's actually inside the phone. If I pull this off and lifted the battery, you'd see the MEID is there as well. So when you're working with CDMA, keep that MEID.
Okay. Now, you'll notice, I didn't say anything about your personal identification. There is a way to deal with this, but keep in mind that personal identification of phones is really important. That's what we call the IMSI. Now, the IMSI value identifies you, and people want to be secure about that, so what will happen with this phone is there is an IMSI value in here, but I can't show you. In fact, only the phone company can access it, and we want them to, because if I know your IMSI, I can track you. I know exactly where you are.
I can intercept every one of your phone calls. So we're a little bit careful with the IMSI. All right. That was fun. Now, what we're going to do is we're going to do it all over again with the GSM phone. Now, a GSM automates a lot of stuff in here, so there's really only one value to worry about, and as opposed to me telling you, let me show you. On this particular phone, I'm going to go to settings, and I locate about device, which by lucky coincidence, popped right up. Now, this is going to vary for different systems but on this particular one, I know to look on status, and if you look here, you'll see something called IMEI information and we click on that, and there is my IMEI value.
IMEI, which stands for International Mobile Station Equipment Identity, is the identifier for this phone on a GSM network, so, all GSM phones have an IMEI. You need that IMEI number. We use it for activation, if you're ever having problems over the phone, you have to give your IMEI number, so it's very, very important that you have that IMEI. Now you look there, you go, "Well Mike, I've got it right here." Yeah, well what if the phone goes down, okay? So what we do is we keep backup copies of this.
We write it down. It's actually on the back of the phone, but prying open this Galaxy is not something that I would recommend to the faint-hearted, so you document your IMEI before you have trouble. Now, you'd say, "Well, Mike, on my phone, I can't find the IMEI." No problem. Let me show you a little trick you can do to get this information on just about any GSM phone. So you just go up to your dialer, and you type this in. Now watch what happens.
Ta-dah! So it instantaneously gives me the information for my phone, and this works pretty much on any GSM phone. That stuff I was showing you for CDMA, that's going to vary from carrier to carrier, but that works on pretty much any GSM phone and it works out really, really well. Now again, we still have that IMSI number. IMSI stands for International Mobile Subscriber Identity, and the IMSI, you can't get to it, and that's good. We don't want people to get to it.
In fact, with the IMSI, when you walk into a geographical area, a cluster of cells, you give your IMSI once, and from there on in, you actually use a temporary IMSI. The phone company is thinking about people trying to capture this information. They're trying to help you. It's not a perfect tool, though. Temporary IMSIs can be beat. There are these IMSI sniffers out there. Here in the United States, we have the infamous stingray systems that law enforcement use.
They basically put up a temporary tower and they can use that to figure that type of information out. The CompTIA A+ is not going to try to turn you into a cell phone tech wizard, but it does have all of these terms. Make sure you're comfortable with all these, because you know why? You're going to see it on the exam. (upbeat instrumental music)
Join Mike Meyers for this installment, which covers everything an IT pro needs to support, secure, and manage mobile devices, including Android, iOS, and Windows Phone. Learn how to configure cellular plans, connect to wireless networks, set up email, sync devices, and secure Android and iOS phones. These topics map to the "Other Technologies" domain—an estimated 12% of the exam.
Details about the certification and the exam blueprints can be found at https://certification.comptia.org/certifications/a.