Hello and welcome. My name is Tyler McMinn with Aruba, a Hewlett Packard Enterprise company, and this is the Aruba Mobility Essentials series of videos. The first part we're on the sixth video covering an RF Signal Propagation. In the last video we talked about antennas. And in this video, we're going to look at sealant signal to noise ratio as well as some of the deployment options that might impact your signal in a bad way and how you can fix that. So without further ado, let's get started. [MUSIC] All right, so RF signal propagation. What is it? Well, signal to noise is a good place to start when we talk about describing a good signal versus a bad signal. Signal to noise takes your received signal strength indicator value. What is the signal strength that your device is actually enjoying, this is usually measured in radio waves in the corner of your device. So this can be described in, an example, on a lab device here where if I open up windows on the wireless you'll see a bunch of different service that identifiers or different broadcasted SSIDs and their signal strength indicated by this little kind of snow cone icon here. Theoretically the less the waves and the snow cone, the worse the signal is, there you go. So here's an example of some weaker signals that were being picked up. That disappeared for some reason. There we go, versus one that's stronger. However, if I want to get the actual number value, numeric value, I may need to run an application like this insider application on Windows or on a Mac. If you hold the Option key down and you click on your little Wireless icon. It'll give you information about your current connection as far as its received signal strength indicator. That is this number right here in the signal column and an insider, they show it as this kind of green line, and they can see some weaker signals here. I've sorted it by signal level. So the strongest signal is this minus 25. That's, like right next to us all the way to an acceptable minus 48, minus 50. Those are really strong to a weaker minus 58, minus 70 is okay for data, but anything beyond like minus 76 or whatever and you're having a lot of interruptions. You haven't a lot of drops, anything minus 80, you're probably not connected. So it does drop off pretty quickly. We want to keep our signal really around, minus 50s or below, minus 60s are probably okay as well. But I say minus 50s and below are, what we're shooting for. So yeah, really nice tool to be able to give you your view of what you have running, or we could look at a Wi-Fi analyzer on a mobile device and that would give you the same. Let me bring this up and I'll show it on screen. All right. So this Wi-Fi analyzer, this is on my phone right now. And what it is, is a free Android app that you can download from the Google play store, fire up. What it shows is the signal here in the 2.4 gigahertz around my house. You can see some of these SSIDs are very strong that's because they're mine and others are coming up from my neighbors here. And the signal level from minus 90, minus 80, minus 78 increases the higher up that y-axis you go. To the left or right is the channel itself, starting with channel 1 all the way to channel 13. No channel 14, bonus points if you can guess why, I'm going to explain in another video here. But yeah, all in all, nice little tool. If you kind of want to play around with this, we're looking at the channels. I could flip this over to a few adjustments here, but I can click on the 2.4 and change it to the 5GHz and I can look across the entire spectrum of the 5GHz and you can see some of these SSIDs, so the first thing you might notice is no neighbors. That's pretty cool. There are some like I think this purple is somebody else. But these two broadcasts on channel 36 and on channel 42, starting right there, centered on 38 and 46. These are mine. These are my McMahon family, APS that I'm running and I've got another one running over here as well. So I've got a couple access points that are running in my house, keep all the family happy there. But that is a quick way to kind of see what your signal level is. So the signal to noise what it does is it compares what your received signal strength is say minus 50 compared to your background noise, which might be say minus 100. The overall background noise not interferes that are stronger than that but just general background noise. If you fall under that background noise or start hitting up against that background noise, you're going to start to suffer. So what we're really looking for is how far away off of that background noise level are you. And that's what the SNR represents. It represents the difference between the wanted signal at minus 50 and any noise or major interference that's consistent in the background. So it's one of the most important factors we'll use where the signal to noise in this case would be a positive 50 milliwatt decibels or dBm. The greater this number the better and 50 is pretty good, that's a pretty good number that you should be shooting for. So the higher the number the better and that you have a clearer signal, which means your laptop and your access point can negotiate a faster data modulation rate which means faster speed and the sooner you get your data out the faster somebody else can jump on that channel and get their data out, which is better for everybody. So it's kind of a win win if you're looking at this measurement. A lower Signal to Noise means that you're suffering more interference. You're having to resend your frames over and over again, you have to negotiate slower data modulation rates and overall everybody starts to suffer on this wireless space. So another thing that might impact your RF signal other than interference that you can look at through Signal to Noise is your Free Space Path Loss. This is an inevitability, the further away you get from the AP eventually, no matter how strong that AP is, you're going to lose your signal. So the closer you are, the stronger the signal even to a moderate range you can still get a pretty decent signal here. But as you start to really get some distance Free Path Loss will creep in even if your access point was sitting in the middle of an open field with no interference whatsoever. Eventually that signal is going to attenuate and impact, and weaken the overall power or amplitude you're experiencing at that distance. So this is your amplitude, the height of the wave, and you can see it start to creep lower and lower and lower until eventually it's going to fall into the background noise that surrounds us all. I know, pretty uplifting thoughts, right? So what do we want to do? To fix this, you want to make sure you're close to your access point. Another factor that can cause a loss of amplitude, even if the distance is close, is if you're going through a wall or some other obstruction if that exists between the access point that's broadcasting and the station that's receiving. Normally the station would have a really good signal, but instead it might be a fairly weak signal only because a lot of your amplitude is being absorbed by the materials of that wall or that source of interference. As the electrons go through that the radio goes through that wall, the thicker the material, the more it takes energy from that wave and results in a lower or even non existent waveform or amplitude level as it leaves the other side of that wall. So absorption is another big concern. What can we do about it well, try and place your APS where they have clear line of sight, like your ceiling instead of below your desk where you've got your feet and you've got your bottom of your desk and outlets and a printer down there and bookshelves and whatever else. If you can get up on the ceiling high enough, you're likely going to have a really nice experience for users that are at their desk trying to work or users in your own home. Walls in your house will typically drop the signal by about 3 to 6 RSSI, every wall that they go through, but it really just depends on the materials. If you're dealing with drywall versus brick, you're going to obviously have a much different experience, brick will drop at about 18 milliwatt decibels. So those are the two things you want to look out for, distance and absorption and this can be measured in your Signal to Noise ratio or signal to noise rate. Ratio, I had it right. All right, well that's it for this video and the next video we're going to jump in on RF power and actually break down that RSSI value. Look at something called the effective isotropic radiated value and how the FCC measures signal strength and all that. We'll get into the rules of 3s and 10s and all sorts of stuff. So I hope you guys enjoyed this video. I'll see you in the next one.
