Wifi Fundamentals for Beginners - The complete Guide | Ofer Shmueli | Skillshare

Wifi Fundamentals for Beginners - The complete Guide

Ofer Shmueli, Wi-fi and Security Specialist

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22 Lessons (1h 43m)
    • 1. Course introduction

    • 2. Key terms 2

    • 3. Rf wavw part 1

    • 4. Rf wave part 2

    • 5. Rf properties

    • 6. RF loss part 1

    • 7. Rf loss part 2

    • 8. Dbm part 1

    • 9. Dbm part 2

    • 10. Antennas part 1

    • 11. Antennas part 2

    • 12. Antennas part 3

    • 13. Antennas part 4

    • 14. Basic wi fi process part 1

    • 15. Basic process part 2

    • 16. Mac layer

    • 17. Physical layer

    • 18. Channel access part 1

    • 19. Csma ca 2

    • 20. Frequencies part 1

    • 21. Frequencies part 2 symptoms

    • 22. Frequencies 5ghz


About This Class




if you'd like to learn how your wi-fi network and clients operate in the wireless environment .  then this course is for you. In this  course, i will walk you through Wi-Fi from the core concepts up to RF know-how


Very soon, You will get comfortable with the relationship between access points and stations.

you will understand how an RF signal spreads in the air and attenuates,

why different data rates are chosen in different conditions ?

How stations share the Air ?

how do they talk without interfering each other ?

How stations discover access points ?


  • Anyone who is curious to understand how wi-fi operates and benefit from the location , ranging and analytics part

  • wireless geeks who usually deploy their wi-fi network at home/office or at their friends home

  • IT personals who wish to be more more valuable to their customers in deploying their wi-fi network

  • IT and Network students

  • CCNA and CCNP wireless students who wish to extend their knowledge on wi-fi location and ranging

  • Anyone who wishes to build indoor navigation capabilities in their app/service


1. Course introduction: in this course, I will walk you through WiFi from the core concept up to the latest location and ranging techniques. Very soon you will get comfortable with the relationship between access point and stations . We will put on our glasses and understand how in r f signal spreads in the air and the 10 you weights and why different decorates are chosen in different conditions. How stations shared the air, How do they talk without interfering each other? How stations discover access point and when do they choose to be passive or active? And this is me, you will get to know me later. We will analyze the traffic that is in our network and what can we make out off it? And we will look at ranging and positioning. Starting from the classic propagation based methods is our society moving to the new high definition location, technique, round trip, time off flight, WiFi location and ranging is starting to make a huge difference and this scores is all about it. 2. Key terms 2: Hey, everyone, thanks for coming back to WiFi fundamentals with location and analytics. This course will help you to muster the air before we dive in into the basic WiFi process and understand how it all works. I decided to give you a head start on the key terms there are related directly to location and ranging. Let's start. The station is a client device connected to your WiFi network. It can be your smartphone, your laptop or just about any WiFi equipped device. An excess point is a networking device that allows a station to connect to the wire network , and Access Point actually acts as a breach. It bridges between two main protocols. The 1st 1 you know to 11 is deep protocol that every WiFi device uses. The 2nd 1802 point tree is the Ethernet Protocol. Our society stands for the received signal strength indicator. In other words, it actually means how much signal power amplitude is received at the other side. Our society indicates power in a DBM scale. Ranging is the method that determines the distance between one device and the other. We will look at different ranging techniques starting from basic equations at to round trip time off flight line. Off site is something that is rare and WiFi deployment. It actually means that the signal propagates with no obstacles around. GPS is one technology that works within a line off site. In WiFi. Radio signal usually moves around through obstacles to reach the other side, which recites in multiple and other interferences. Free space Bath loss describes the signal off as it travels along the path. Attenuation is the signal intensity reduction as it moves in space. Location out the rhythm is the function that converts the arranging the measurements to an estimated location. We will walk through different location algorithms from triangulation to try alliteration. Proximity is actually the nearness, their nearest in space word that shoe devices the station and the AP can still hear each other. Next up are F Wave 3. Rf wavw part 1: one. Things were coming back to WiFi fundamentals. Would location and an electrics. This course will help you to mustered the air. WiFi is puzzling. It's in the air, yet you can't see it. It is possessed with the mystery of physics. Sign ways. Reflections, reflections. In this lecture, we will look at WiFi at its basic form. How it evolved its physical properties, what makes attenuation and why different radio frequencies are preferred. By the end of this video, serious, you will be able to understand, waves their behavior and plan your network more effectively. What will you learn? We will take a look at waves. What are waves? Why do we use waves To represent WiFi energy? We will focus on one type off a wave. The sine wave its properties and why in different frequencies wave tend to function differently. We will also take a look at the different frequency used to send WiFi signals at the relationship between access point and waves. And we will take a look at our if loss. Why does it happen and how can we avoid it? Wave is a disturbance propagating in space or any other medium. We're all familiar with different types of waves. A stone that is thrown into the water with create wave. Not that wave. That kind of wave a wave usually transfers energy from one side of the medium to the other . It can be represented in different forms and shapes. Usually we do it using a sine wave. I know it looks scary, but trust me, it is simple. We will not get into the geometry of shapes. But remember this signs are just a mathematical function that helps us describe a smooth Oska waiting wave. And if you want to make things more simple, think about it that way. Sinus to a circle. The same is a lying to a rectangle. It makes the circle circular sine waves have properties that characterize the way they move , react to obstacles, attenuate and deliver data. We will dive into each in the next lecture sealed, then 4. Rf wave part 2: Hey, guys, Thanks for coming back to WiFi fundamentals, location and analytics. This course will help you to mustered the air at the end off ARF wave part one. We describe the R F energy as it spreads in the air in the form off a sine wave. We have also mentioned its properties period, frequency, wavelength, amplitude and phase. But before we dive in into each, I want to give you another view of a sine wave that I believe will make it clear and simple to understand. We've mentioned the signs are related to circle. All right, so how do you measure the distance around the circle? Well, it seems that if you draw a line from the circles outer edge through its centre to the opposite outer edge, which is the diameter and multiply it times pi, which is a constant equal to treat 0.14 you will get the distance around the circle, which is also called the circumference. It doesn't matter if your circle is huge or small. You can also measure the distance around the circle using the grease. A full circle, everyone knows, is 360 degrees. If we cut a circle toe, half with actually stepped 180 degrees from zero degrees origin. If we continue to cut the circle into four pieces half off one eighties, 90 degrees and so we have the circle, split it into degrees from 0 to 90 and then tow 182 170 tree 60. Now let's tear down the circle to two pieces. Andrew T. The bottom half What do we get? Do you see? That's a sine wave. It's the same circle circumference just differently. If we start to measure it, we start with that Syria degrees. Move along to 90 degrees up to 360 degrees. You'll very soon learned that a WiFi signal that starts from the origin in different degree , which we also call a phase, is the basis for higher decorate. Okay, now let's understand our waves. Property 5. Rf properties: guys. Thanks for coming back to WiFi fundamentals with location and analytics. This course will help you to muster the air. It's time to take a deep look at waves properties. And trust me, it is a key topic. What? Because everything in WiFi is somehow related to waves. Properties? Let's start. Our first property is actually a measure of time. How long does it take for a wave to complete one cycle? Our second property wavelength is the distance between the pics or one trough off the wave to the other. It is expressed as the Greek letter lumber frequency is the amount off cycles away finishes in one second. We measure it using the unit hurts. So a 10 Hertz wave is actually a wave that finishes 10 cycles s second. You will see that the high frequency wave results in a short wavelength and vice versa. Amplitude is the amount off energy the signal has or in other words, how strong is my signal. It is measured from the resting point towards the pig and that the wave moves along over time and distance. It loses energy and its amplitude, its power decreases due to free space. packed loss and interferences. We measure amplitude in absolute units such as a but or a minimum, or in a DBM scale, which we were looking to very soon. Alas, property is faith. Remember that a sine wave is a periodic wave that repeats itself over time. In its nature form. It starts in zero degrees and finishes a full cycle when it reaches 360. The grease, we say a wave isn't phase if it is either zero degrees or 3 60 degrees a part. When two way forms are not synchronized, there is a phase shift. Their picks and zero points do not match up the same points in time. And this is this truck tive. The result is a loss or even zero amplitude, zero power. On the other hand, when both off the waves are in phase and in the same amplitude and frequency, the two waves reaching the antenna will look like a single wave. It is what we know as a gain, a constructive interference. Our access point believes that it is receiving a stronger wave. It's time to summarize, as our access point and station transmits our energy into the air it is represented graphically as a sine wave. A sine wave has all the properties to represent R F signal as wave meet obstacles in their space day, lose power amplitude and in several cases, reflect back and different faith, which sometimes caused phase shift in real deployment are access. Point antenna will get different types of wave, some of them destructive and some in phase. All right, that's all for today. Next up, our F loss. 6. RF loss part 1: Hey, guys, Thanks for coming back to WiFi fundamentals, location and analytics. This course will help you to muster the air. We have spoken off waves and waves tend to lose their power and faith. This is our topic today are if loss our flaws is something you want to avoid in your network. But it happens as a second nature toe. R f behavior. Two facts that are good to remember. Three Space path loss is the number one reason for signal loss. Interferences are everywhere, and you can do a lot to avoid them when planning your WiFi network. So what will you learn? We will look at what causes a loss. What is the free space path loss? Theoretical model? We will look at different types off interferences that you are about to witness on your WiFi network. What is the receiver sensitivity and what does it have in relation with data rate? What is our sasae and what is signal to noise ratio? When Aref wave spreads in the air, it will most often meet obstacles. It can be trees, people walls just about anything. Depending on the type off the obstacle, it will be reflected refracted and sometimes even observed some off. The signal will arrive in short delay, and some will have a phase shift. This phenomenon is called Multi path. Many times do it to not receiving the signal. Our station. Will Richmond's Make the Friends over and over again. Free Space Path Loss This is a key topic that we will dedicate a tree part video. But in short, when your WiFi signal goes into space 80 10 you it's just like your sound wave. When we talk the father you are the weaker the energy carried by waves. Free space path loss is based on the inverse square law and frequency propagation. I promise you we will deal with each, respectively, assuming the same transmission power. Higher frequency waves tend to attenuate more than lower frequency. You will see it all over when 2.4 gigahertz transmits. They're much more immune to interferences than the five gigahertz Frequency Devices winner Flosses witnessed in the air due to interferences or free space bath loss. Our signal degrades, and we can't achieve high data rates. There is the receiver sensitivity, the minimum loss acceptable in order to achieve a good data rate a station that is close to the excess point can use high data rate as it gets far away. It has to use lower data rate. Vendors tend to report receiver sensitivity in there's product spec sheet. Look for that. Different devices have different receiver sensitivity. And when you plan your network for location and analytics, think always about your weakest receiver sensitivity devices. Next up are if loss part to see you then. 7. Rf loss part 2: Thank you guys. Thanks for coming back to WiFi fundamentals with location and analytics. This course will help you to muster the air. All right, so we are continuing our adventure in the air, and in this part we will look at the phenomenons that happens to our wave as it hits physical objects. The first phenomenon is reflection. It happens when Aref wave is being reflected from different services. In its surrounding reflection happens when the signal bounces off, a matter that is none absorptive as metal, it is quite common, and furniture, windows, walls and mirror the signal will change its direction. Absorption happens when the signal hits a dense object and gets absorbed in it. It is common and concrete walls, bricks, different types of doors and even in people, the signal's amplitude is reduced. Another phenomenon is scattering. It happens when the signal hits a surface that is not even and is being reflected all over . It is quite common, and furniture, roofs and metal object. The result is increased past. It is more common in high frequency waves. Do it to their short wavelength. Another phenomenon refraction. It happens when the signal hits a surface with a different density, then the air that will bend its path as it moves in it. It is very common in glass water, and the result is a changing path and attenuation. So what is the outcome? Well, the outcome off away that changes his path and comes in different direction. Polarity and time is face shift. Remember, we have spoken off faith shift off the wave. It causes it sometimes to be cancelled and sometimes to be a stronger, vital wave. So what do we do? Well, we're quite a head off. Our learning curve on this topic is an invest topic, But just very mind that in today's WiFi network, we use different techniques to deal with such phenomenons. One of them is guards. WiFi friends are actually sliced into tiny symbols, tiny frames they're sending with a bit off a delay, one after the other, why it is done to compensate the delay between the time of the transmitted signal and the reflected signal as it approached an obstacle. In its way. Our flaws can also happen with interferences that come from other Aref sources in our surrounding. It doesn't always happens due to physical phenomenons or obstacles. It can come from other idol to 11 devices or other Arafat emitting devices such as a microwave or a Cordless phone. The result is the same frames are lost and damaged. So our signal has lost its power due to interferences and path lof. And when it hits our device, we would like to know how much power is left. So we use a measurement known as the RSS. I received signal strength indicator. It is expressed in a DBM format which we will look into in the coming course. It usually starts from zero to minus 100. The closer the value to zero, the stronger the signal. Another term that you may have heard off is snr signal to noise ratio and it is directly related to our F loss. It is actually the measurement off the intended signal are Aref signal in relation to the background noise. What is the background noise? It is actually any electrical device that radius in the air. Our signal has to be at least 20 to 25 db higher than the noise in our surrounding. Otherwise we will suffer from frame loss and our data rate will decrease Next up are f met in the form off dbm 8. Dbm part 1: Hey, everyone, thanks for coming back to WiFi and fundamentals with location and an electrics. This course will help you to muster the air. The common topic is one of the most fundamental stuff you need to know. Decibels and DBM. This is the unit we measure signal strength for it. But as you will see, it is nothing absolute. Unit DP's are used to measure the relative power between two devices. Why do you need to know that? Because it influences everything. If you want to double your access point coverage, you can do it. Knowing Deby's rule. If you want to calculate ranging, you will need to muster the DBM language. And if you are reading a spec sheet off an access point and even an external antenna, you will want to understand its gain, which is also in DP's. Decibels are everywhere in WiFi. What will you learn where we will take a look at DP's that their basic form, How do we use it? When do we use it? We will look at them in WiFi networks and we will learn the bees must know rules. We will also take a look at the six db room most of her life. We use absolute units we measured power using but and Mileva? We measure length using centimeters and meters. We measure awake using grams and kilograms. DP's are relative. They measured the difference or the changing power between two sources. Why do we use DP's? Because it is much more simple to express the ratio between two power levels, then doing all the complicated mathematical function that is involved. Let's see an example. Let's assume that we have a signal sent with a power off eight. But instead of calculating increase off 4000 times single, we can say that it has been increased in 36 dp or that the antenna off the transmitting device has a 36 db gain. If the signal has been decreased due toa continuation in the skin off 100,000 times, we can just say that it had been decreased in minus 50. Db that simple db Zehr used in different flavors in WiFi but net on Lee. We use them also to describe a cables loss or antenna's gain. When it transmits in WiFi, we used the D B M scale, a decibel relative to one millibar one minute but equals zero d b. M. There is a reference remembering. So in the case where you see a plus sign or no sign at all, it indicates that the output signal is larger than their reference then zero dbm if you see the minus, sign that in the case that the output signal is less than the reference. So in our case, our access point has 20 DBM transmission power which is 20 db m stronger than the reference our access. Our station has a loss off minus 70 d b m in relation to the reference which is zero tbm or one millisievert. Is there an easy way to calculate DBM And what is the six db rule that we have mentioned before? All of that is coming in part two. 9. Dbm part 2: a lot of sense for coming back to WiFi fundamentals, location and analytics. This course will help you to muster the air in part one off Aref Math We have learned off DBS decibels. We have seen that there used as a relative measure between two power units. They measure the change. The difference. The next thing to do is to take a look at our WiFi network and find out where it is used and how. First, the antenna, which is the next topic that we will learn on 10 other old over in our stations and access point there, gain the way they focus. The radio energy is calculated using DP's, but it is DB in relation to an easier tropic antenna. We will look at it in more detail in our next lesson. But remember, when you see an intent again, remember that the reference model that changing power is in relation to an optimal is a tropic on terror. Dp's are also used to find out the relation between two devices that transmit, so if we say that one access point transmits in 10 minutes and the other transmits in 20 minutes, the power difference between the two access points is actually treat DPM. Why? Because as you will see very soon, Treaty B M is actually doubling the power signal to noise ratio. Is another place where we see DP's. We have mentioned it before. It is a measure to compare the signal that our station or access point, has received compared to the background noise that comes from other electrical devices. The outcome is the snr. How do you calculate it? Very simple. You take the noise minus the signal and that is the S. And our another good usage of Debbie's is when you want to find out the loss or to describe the loss in power from the access point to the station. So we for access point transmits a signal in turn me liver and their stations receives it as a five million. But signal we say that the loss can be described as a minus tree DBM loss. Remember three D B doubles. The output power minus treaty be represents a loss of 50% off your power. You confined up the relation between DP and fact in this table. But trust me, the principles are easy. We say that in a DP World, they're actually two main rules treaty be rule and the 10 db rule. A treaty be raise is toppling the power treating be lost half the power 10 db raise 10 times the power 10 db loss 10 times less The power. You can calculate just about anything using this rules. If one I p transmit in 10 million and the other in 20 million votes which is double, I will say that the transmit power is strange Is treat db stronger Remember, treaty be is double the power The next Truell I want you to remember is very practical. Every time you wish to double the coverage off your access point, add six deep be to its transmission power. The reasons are beyond this part. Off the course we will look at them later on. But remember this six db doubles the coverage off your access point Next up, a whole new topic on tennis. That's the place where really a waste propagates towards their destination. See you soon 10. Antennas part 1: Thanks, guys. Thanks for coming back to WiFi fundamentals, location and analytics. This course will help you to muster the air. We have come to one of the most intimidating stuff in WiFi networks and tennis. Why do I need to learn if antennas it's there and it works well, no antennas are key to your understanding off the wireless environment. Just think about it. Without antennas, wireless communications could not be born. Their wealth work is fascinating and they're everywhere, internal and external. The intense where the radio waves hit the air for the very first time. Setting the stage for our F performance on tennis pattern are crucial to your wife. I deployment. If you want to cover a whole way, you will probably use a directional antenna. If you wish to cover a hotel lobby, you will use an only directional antenna. A few facts that are good to know antennas don't add power to the Aref single. They focus it in different directions. We call it a game and fact number two. If you wish to double the range off your antenna, you have to quandary. Pull it at six db I. What will you learn We will see how antenna works, how they're built. We will learn off key terms, gain direction, polarization. We will also learn off the easier Tropic antenna, which is the theoretical and 10 a model that every antenna down nowadays relates to it. We will look at different antenna types, the only directional, the directional and the diable antenna. And we will also take a look at how antennas are used in penetration tests. Do you remember pendulum? While pendulum is a device that when you apply very small force in a specific frequency, it induces a very large motion that we pits itself. This phenomenon is known as a residence. That's exactly what on Turner's are doing. They have a resonant, an optimal frequency until his role is quite simple. They turn electromagnetic wave to electric energy and the opposite. You can think of antennas as a metal road that is connected to an electrical source. That source usually uses alternating current a C. As the electrons move Indian tenor, an electric current is induced and the lines off magnetic flux are created and radiated into the air. The frequency at which the current goes in and out goes in and out into the antenna is actually the frequency off the antenna. And remember, frequency and wavelength are related until his length has a direct linkage to its ability to tune. Receiving. Transmit different frequency. A bigger antenna will soon lower frequency. Make it small. It will have a higher resonate frequency. The size off the antenna has to be proportional to its way feeling If the wave produced by the transmitter that is at the right frequency, it will resonate, and the signal received will act to that off the antenna, and you will get a stronger signal if I want you to remember. One thing is that wavelength equals antenna size until it's by design are created to support different frequencies. This is why they're usually 1/4 or 1/2 wavelength off the frequency for which they are designed. The signal will have a larger pick at the chosen frequency. It will resonate. Better antennas are built to support certain frequencies. Their physical length is built upon the proportions off the frequencies. Wave length. One example that is very colon is the di pull antenna. It is also called the half Wave Die Poll, as its length is half the frequencies. Wavelengths coming up, part two off on tennis 11. Antennas part 2: Hey, guys, Thanks for coming back to WiFi fundamentals with location and analytics. This course will help you to muster the air. All right, we have reached on tennis part two, and until NAS actually provides three things to a radio, it doesn't matter which radio is it. WiFi ham radio, whatever gain direction and polarization. To understand it better, we have to go back and understand the easy tropic antenna model. And I'm telling their exit signal in different directions. Everything is relative to an is a tropic antenna. It is a theoretical model, often intern in that sense, energy equally in all directions, a perfect fair all on tennis. Every untenable in the world takes easy tropic antennas. That reference, and there again, is compared to an is the Tropic radio toe. Take a look at In tennis beckoned. You will see that their gain is mentioned with the DP I Value DB versus is a tropic until let's see how it works. Let's assume that their A P has an easy tropic antenna and let's pretend that it transmits power in eight. But it signaled this press is equally in all directions. The red dot is the received power one meter from the easy Tropic Antenna transmitter. It is a lower signal than the A region. Do it to attenuation, and let's assume that the power measured is to that. Now let's imagine that we have a really directional and tenor Instead, a real antenna has the same power off. Eight that but contrast or is a tropic antenna. We have different parents to the signal. We have the main love where most of the energy is focused. We have the back. Loeb were signals a lot weaker, and we have the side lobes off the far field and usually represents unwanted radiation in undesired directions. Power is concentrated in different directions. Now let's assume that one meter away are directional. Antenna has more power than the to. What opposed to our is a tropic antenna. Let's assume that it has for about one meter away. Power, as we say, is concentrated in a specific direction. You can see the main love is directed towards the far, and the power received is for what one meter away. So actually, where we have the easy tropic antenna power received the two back. We have our directional and tennis power received at four. But so now we say that the gain one meter away off the green antenna relative to our is a tropic antenna is two times stronger. If you convert it to db I, it is Euro said it right, a treat db I gain. And that actually brings us to our first term game gang is the power output in a particular direction Compared to the power that is produced, Bang is a tropic antenna. So if the power is one but in an is a tropical container and in our intent of the power is too bad, then we say that gain is twice as strong. Gain actually focuses the Aref energy. It doesn't add power to it. It focuses it as if you are playing with a balloon and stretching it into one direction. Lo gain transmits in all directions. Hi again usually transmits in one particular direction. Gain is bi directional. Higher gain also helps us to receive better, since the beam is stretched farther. If we look at Antenna Perkins, we can see that low gain and tennis have a beam that is more spherical in its nature. High gain antennas have a beam that is more narrow and directional. Next up on tennis part tree, where we will see how polarization and their activity, our attitude, the antennas See you soon. 12. Antennas part 3: everyone. Thanks for coming back to another video off WiFi fundamentals with location and analytics. This course will help you to mustered the air. We are advancing and poetry often tenants. We will look at directive ity and polarization. Their activity is the shape off the being. It can be narrow or white. Its shape is measured in degrees, and in most cases it is related directly to the antenna's gain. A low gain antenna has wider being a high gain antenna as a narrow beam. But be aware, although it seems as if we can control the direction off, are being and aim it at specific location. Our environment is full off physical objects, which, as we have seen in the IRA Flosses video, can change your single faith pass and amplitude. Polarization is known mostly for its usage in the sunglasses industry, and it's quite the same. Our waves are actually comprised off two main forces, the electric field and its opponent. The magnetic field polarization is determined by the electric field. It is the orientation off the signal as it leaves the antenna. The electrical portion off the waves will always live the antenna in certain orientation usually vertically when we hold our smartphones or tablets in a different orientation. They're actually in different polarization plane than the transmitting device that can happen from time to time, and the result can be a bad signal next up on tennis, part for seal them. 13. Antennas part 4: Hey, everyone, thanks for joining back to WiFi fundamentals with location and analytics. This course will help you to mustered the air work part for far antennas. Serious. And this one is the last checked er, What are we up to? Well, we will look at antenna types. We will learn how to calculate E i. R P, which is the effective power transmitted from your WiFi access point. We will also take a look at them tennis being patterns, which is something you need to know. It influences your coverage area and why hackers air using high gain on tennis. There are several types, often tennis, but in general there is the only directional and the directional antenna. Different types, different focus. Oh, Minis has 360 degrees coverage when you look at its beam from the top view. But take a look at its side. You. It's far from being spherical. Reminds me of something. Yep, it's a doughnut shape. Only directional is vertical. Coverage will arise with its antenna gain. Usually it is between 7 to 80 d Greece. Their power. Their gain is usually between two db I, for a 2.4 gigahertz access point and five TB for a five gigahertz access point. Directional antenna is another story. Look at its main low. It's beam is squeezed into one narrow direction. The pros, its signal coverage and sensitivity are way bigger than only directional in tennis. The cones, because of the narrowness off the signal, the area beside and above stays uncovered. A young he is unknown directional antenna, and so is the dish antenna on tennis coverage rise. Different types, different coverage areas. We can represent the courage to its being patterns from above, which is the H plain and only has a full coverage 360 degrees from the side view the vertical view. We can see that not all of the area is covered, so we have our access point power. It is connected to an electrical source, and we have our intent again, which is also something that adds to its power. And in some cases, when we use external antennas, we also have cables and connectors. How much power do we send out off our access point? Well, that is, the effective is the tropic radiated power. The bottom line. Quite simple. The equation is simple E i. R P in DPM is the transmission power minus the cable loss plus the antennas game. So if we have a 14 DBM access point power and a connector or a cable, that makes it lose another to DP ended antenna's gain that is equal to four db I. The summer fall is 16 DPM power and if we're into equations, another equations, which is quite interesting, although we will not get into the numbers. This is the equation that shows us that there is a relationship between the effective area or the size off the antenna, and it's a game. Gain is equal to four pi, the effective area divided by Lambda Squared The bottom line. If you want more gain, use bigger area and tennis and use lower frequencies. This course is not about hacking, but know that high gain and directive ity are used by hackers to attract WiFi stations to connect to them. They do it usually in two steps. One the associate, the user from their safe access point and re associate them using a soft AP of virtual one with the same s society, the same WiFi network name and the stronger signal. Do it to their high gain antenna. All right, next up the needy, greedy. We will learn off. Basic WiFi process sealed. 14. Basic wi fi process part 1: Hey, everyone, thanks for coming back to another checked ER and WiFi fundamentals with location and analytics. This course will help you to muster the air. We finally laid the foundation. We understand now how weight is created, how it is being propagated in the air, how it reacts to interferences. We will keep on discussing waves and Aref theory as we continue. But now it is time to understand the basic WiFi process. Basic WiFi connection process is like seeking a job. There's the active job seeker who was always looking continuously for jobs and there's that passes. One was waiting for job proposals we will keep on developing the sin ology as we go on. So what is ahead? We will extend our key terms knowledge. We will also look at the anatomy off a job seeker, which is actually our station, our station looking for the access point. We will look at the different Discovery technics, the passives can and the active scan. And how do devices connect and share the air? Everyone in your WiFi network wants to talk. We have already discussed what is an access point and what is the station and the group off stations connected to one access point is called a BSS. In your house, you probably have a BSS, but if you have a bunch off BSS is that are connected to the same distribution system to the same switch and gateway as you probably doing your work or office, you have an extended service set. There is also the S s I D, which is the name off the wireless network and the Beer Society, which is the Mac address off the access point. We will look at Mac addresses as we go on. So we have arrived to an area where access points are all around. And now our station, our smartphone, needs to discover them. How do they get acquainted? Well, discovery, the way station locates an access point can happen in two ways. The passive way and the active way. The passive way, very much like the person who's passive when looking for a job is done, using a beacon frame become frame is like job proposals. It is a frame that is sent as a broadcast frame. A Brooklyn's frame is a friend that anyone can hear in the network. It is sent that the lowest decorate, usually each 100 milli. Second, a bigger frame holds information on the access point, such as its name. It's Bs Assaidi, the supported data rate. It's security and encryption capabilities such as W. P. A two and tree. The channel. It works in the frequency the AP works on and the channel with 20 or 40 megahertz or even 80 and 160 megahertz if it is an A C access point. And then there's the active way. The guy who is always looking for and shop in the active discovery phase. Our stations sense another frame. The probe requests Train Singh. Is there anyone out there? It is sent in every channel that the station supports and what it is sent. It waits a while. If there is no answer, it moves to another channel and transmit. Every AP that receives the proper request must respond. They're actually two types off probe request. There's a now probe request that is sent to anyone with no specific s society. And there's the direct one that described contains the SS I. D name. So we've had a problem request sent by our station asking Is there anyone out there and our access point responds. They respond with appropriate response, which is a frame that is actually very much alike. That beacon frame it contains all off the eighties capabilities supported data rates, frequencies, used encryption and security and so on. Up until now, we have seen the discovery process. It started out with a passive skin. Our station. Here's a beacon frame sent by the AP describing its capabilities and active skin, the station describes his capabilities and asking, Is there anyone out there? We will continue with the association process in the next part, see them. 15. Basic process part 2: Hey, everyone, thanks for coming back to WiFi fundamentals with location and analytics. This course will help you to muster the air. Up until now, we have seen the discovery process. We have had the bacon frame sent Former Access Point and the probe requests. And former station Discovery is you will see is happening all the time. As our station picks the probe response from the access point he chooses, one that is most compatible. Comparability can be based on its security encryption schemes or supported data Rick. And now our station begins what is known as an authentication process, the first step to actually join the network. If a station wants to send traffic through the access point, it must be in the appropriate connection state, which is authenticated and associate ID authentication requests. Training is the first step when our station attempts to join the WiFi network, but nowadays it has nothing to do with security. It is an automatic procedure for the two parties to start a negotiation process. Our access point responds its acceptance most of the time, and it is now authenticated but not associating up until now. Our station is doing this process with multiple excess part. If you remember our previous video, it is an enough to checking out different joke proposals. Our station has chosen its access point off choice and Sense and association request rain with its supported data rate and encryption. If our excess points is a match, it will respond with an association response frame, indicating acceptance or rejection. It will also send the station and a I D association idea. Every access point holds its able off its stations with their unique identity. Fire. Now that they're station is authenticated and associate ID, our access point will actually start to check its security credentials. If all goes well, we are connected. So we're finally connected. And we had started with the discovery process. The pro brick was the probe response and went through authentication and association frames . We haven't touched on frames, but these are all management frames, frames that takes care of the initial set up off our WiFi network. We will look into frames in a dedicated video. Our station is connected now, and yet it's still sense. Probe requests and listens to beacon frames, always looking for new opportunities. It does so because it is more by. It always moves its signal the grades, and it has to be ready to connect to another access point. It is a survival impulse. We are reaching the end, and the last key concept to remember from the basic WiFi process is states. Our station can be in different states dure ing the connection process the 1st 1 unauthenticated and unassociated. It is still in Discovery mode, the second state authenticated and unassociated. The third state is authenticated and associate ID. But still it hasn't started this security process, and state for our machine is authenticated, and associate ID station can now send data frames. Yet if the A P is sends at the association request to the station or for any other reason the station disconnect, it goes all the way to state one, that's all for now. Next up, where does WiFi fits in the O assigned layer 16. Mac layer: everyone. Thanks for coming back to another checked er off WiFi fundamentals with location and analytics. This course will help you to muster the air in our basic WiFi process. We saw the exchange off management frames sent to our access point and back to the station as they both try to establish a connection. The language WiFi speaks. It's for Oracle can be better understood. Once you're familiar with the OS side layer, it will help you in troubleshooting and will position WiFi in the context off every network that you're a part off. What will you learn? We will understand the OS. I layer the theoretical layer that shows how it data moves along. We will focus on the two main layers, which are related directly to WiFi, the Met clear and the physical layer. The OS Tsai layer is a theoretical model that helps us to understand how a data moves along from one side to the other. It starts in the application side where it all begins Your browser, your email client down to the physical layer, the cables or, in our case, the air, which is our medium. Always. I Layer has several representations, some include several years, but most of us tend to look at things through a five layer model. WiFi happens at the bottom layers, the Mac and the physical. Let's look at the process. Data can move along in any direction. We will look at it from top to bottom in our application. There, the first layer. We have protocols as http. We use it in our browsers to get re sources as you are ales for it to get from our browser to the resource it uses the TCP stack that every operating system has. It allows it to transfer the data using internal ports and sessions. There is the second layer TCP relies on the I player, which gets us I p addresses and is responsible that the data will move along between routers. The I P layer relies on the data link layer, which is actually the Mac layer to shift that data on to the physical layer, which in turn is responsible to send it into the air or into an Internet cable. As data moves on, it dresses up in different forms as it gets the I P address. It is called a packet, as it moves to the MEC. Clear and the physical. It is called an M. Stu MPD, you and PSD, you, respectively. Complicated. Don't worry. It is just a way to describe data in a different form. In different layers. Own WiFi particles have the same McLear almost the same. We have seen some changes in the latest standards, but the difference lies mostly at the physical layer. So rest go ahead and see what does the Mac layer actually do? Well, the McClair provides a variety of functions that supports the operation off your WiFi network. As its name implies, it is responsible to coordinate access to the shared physical air interface so both the station and the access point can communicate effectively. You can think of it as the brains off your WiFi network. We actually see the Mac operations just about everywhere. When our access points sends a destination broadcast frame as in a beacon frame, it is processed at the stations, receiving it in the Meckler. The same goes for the probe request, and in times when the frames received with an error, which is something that happens all the time due to interferences or back signal, the Max responsibility is to retransmit the frames again. It also adds a physical hardware address to each frame. That is the Mac address. We have said that the McClair is our control tower. It controls the traffic endear, and that is exactly what it is. Dude, it is responsible for the discovery process. The management Fred's nearly to establish the connection. And once everyone is connected, who gets to transmit and even managing the power saving or first station? The McClair is also responsible for the physical hardware address. Without it, our planes could not reach their destination. Mac address is used in location in electrics as a unique identity fire, though in recent years vendors are implementing mech address randomize ing algorithms. Next up, the physical layer seems, um 17. Physical layer: everyone. Thanks for coming back to another chapter in WiFi fundamentals with location and analytics . This course will help you to muster the air. We are continuing with the OS. I layer the theoretical model that describes how data moves from the application side to the physical layer. In WiFi, everything happens in the bottom up two layers. The physical and the data link de McLear, which is actually the data link layer, as we saw previously, is the brains it controls and manages the data that arrives and passes it to the physical air or from the physical layer towards the application side. The physical air is responsible for the transmission and reception off frames. Let's see how it works. The physical layer is the bread and meat off our WiFi standards Whenever you hear or read on your access point box that it supports 802 11 a. C a. D. It is the physical layer standard that your access point supports. The different standards dictate the operating frequencies off your WiFi station supported data rate modulation and more in eternity. The responsibility off the physical layer is to carry the media over the physical hardware . The cables in WiFi. We are dealing with frequencies, bends and channels. Air is our medium physical layer is responsible for many operations in your WiFi network. Part of them is to prepare the friends for transmission. Use different modulation according to the nearness, off to your station and access point. Change the radio channels according to the environment condition. If their trial did, we can see that the different standards way back up until nowadays supports different data rates. Number off available channels channels with different techniques that spreads the signal in the air as oh ftm, which we will look at them as we continue in this course and collusion avoidance techniques . Remember that wife eyes over the air. It must avoid interferences in different conditions. We can see clearly the you can use high decorates at a short range. You can use low data rate at the longer range. Decorate is correlated directly to distance and signals condition. The farther you are, the higher the RSS sigh and the smaller the signal to noise ratio and the smaller decorate . All right, we're progressing and next up is channel access. How your WiFi network manages each station and AP is turned to transmit frames in the air using C. S. M. A c A. See you soon 18. Channel access part 1: Hey, everyone, Thanks for coming back to another. Checked her off WiFi fundamentals with location and analytics. This course will help you to muster the air in a previous part. We have seen the basic WiFi process throughout the exchange of management frames how a station connects to the access port. We've also discussed the roll off the McClair and the physical air, each with huge responsibility for the operation off your network. But hey, our wife and networks are crowded. Everyone wants to talk. Who takes care of their If one station starts to transmit slowly and the other consumes a lot of Ben with, that is a mystery for the most of us. What actually happens in the air whose turn is to transmit data and who just wait for the others? This is our topic today. How air is shared between our station whose turn is to tuck and how fair is WiFi to legacy clients. So what are we up to today? We will learn off C S m. A. C. A wife finds mechanism to sense and avoid collusions in the air. And we will also understand and see how time is coordinated between stations through the usage of D. C F. Scary words, it will all be clear soon. Ethernet has no issue with collusions. It's used to be an issue in the old days when haps transfer their data, but it switches replaced hubs. Collusions air dealt in a very effective way. Wireless is another story. Clients operate under a medium that is available to everyone. The air two major things must happen. There has to be a mechanism that will avoid collusions and second, shared the air time to every stations around. How do we do it? The C F A distributed coordination function this year grants access control to the physical medium. He is actually your doorman. He's doing so by setting a period of time. But the station is to wait in different scenarios. So this half is actually that time period. There are several types of time periods, but for now we will look a tree off them, which are the most dominate DFS DCF Inter frame space is the most used yet. It's the lowest priority Time period s I fest is a shorter period of time, used mostly by our access points as it transmits back an acknowledgment free and if s, which is used before quality of service frames with high priority, such as in voice over P applications and video. C S M a C A. Wood stands for carrier sense. Multiple access with collusion of Boykins happens in two steps. The first part physical carrier says Our station detects energy in the air. It can be wife or even an energy that comes from other sources. Such a czar microwave. We will assume that it senses another WiFi stationed that transmits, and there comes the second part. The virtual carrier sense. With each WiFi framed there is a duration value, the tells stations how much they have to wait for the end off the transmission. So if a station is in the middle of a transmission, station, B will read its duration value and set up what is cold enough and network application vector that only after it it can starts. The steps needed to send its frame now is actually a period of time that is equal to good aeration value off station A. But that's not all as enough ends. Our station will wait another time and ifs an inter frame space as defense. It will start another short time called the back off timer. The station actually generates a random number number off lots time, period that the station is to wait after def, so has ended. It is also called the Contention Window. The number of slots is derived from the modulation type for their success modulation, a topic we haven't touched yet. Contention windows can be up to 31 slots. And for all if the M and more advanced modulation techniques, it is up to 15. Now, Station B can trust me. So if we try to summarize, the first thing is to sense the air redid, aeration value set up. And now wait some time. Usually dips generate a back off timer and transmit. But that's only the beginning. Next up, C S m a c a part to see that 19. Csma ca 2: Hey, everyone, Thanks for coming back to WiFi fundamentals with location and analytics. This course will help you to muster the air in the first part off C S m a c A. We saw how d C f actually coordinates the time between transmissions off every station in your BSS. DCF is based on this rules before every transmission, the station has to wait a period off time. DFS is used almost always. The rule is if you are not sure it is your turn to transmit. But you want to transmit Wait at DFS. If you are sure that it is your turn to transmit use s I f s, which is a shorter period. So let's see it in action. Our station in the top sensitive data free Every other station around, including her access point turns their physical carrier since remember that in our stations dead a frame header There is a duration value which are second station can hear and set up its own nev timer throughout the nef time. Our access point Wait a sifs. It is a short period when you are sure that you need to transmit and then sense the acknowledgement frame to our station. You're dead. A framed arrived As the enough timer ends, our station waits at gifts, an inter space frame that is used mostly between stations, who are not sure if it is their turn. As the defends, the contention window starts and our station generates a back off timer this time off. Three time periods, slots. Each slot is in microsecond a very short time, and now it can transmit. Now let's zoom that another station wants to transmit instead of our access point so the other station would weight. The same is our previous station at Nef time at def so and will generate four time periods . Loss. So who's to win our station? It sends again the data frame and when. Since the data frame the other station weights in their turn and turn on, their physical carrier, says rescinded duration value and waits at this next up frequencies. See you soon 20. Frequencies part 1: everyone. Thanks for coming back to another chapter of WiFi fundamentals with location and analytics . This course will help you to mustered the air one off. The key topics and WiFi understanding is frequencies. It is the media where your network operates, and although it seems as if it comes is a second nature to your deployment. The choice between the right frequency, the channel and it's switch is crucial to a lasting good experience. WiFi operates mostly under the 2.4 gigahertz band and the five gigahertz back. The reason is regulation WiFi is aimed that used within the Iast Sam Bends, an unlicensed spectrum that enables user to access the radio spectrum without the need for the regulation and restrictions. The ASEM Ben, the industrial, scientific and medical bends are reserved worldwide for the use off radio frequency energy for industrial, scientific and medical purposes. By choosing the right frequency, you're actually saying this is the highway where my data will travel. The would fall off the roads, the faster it is. But, hey, there still could be traffic jams if not planned, right? Let's see which highways and roads are around. I'm using WiFi Explorer, a free great tool for Mac users. We can see the s s a these the name off the wireless networks. And there's their signal strength. There are rhesus I, and even the signal to noise ratio. The difference between the signal's strength and the noise around. And then the right there is the frequency band. And guess what? Most of the networks, at least where I live, operate under the 2.4 gigahertz band. They're channel number of Arise, but the whiff stays mostly the same. 20 megahertz. Let's go back and understand what we have just seen. So what are we up to today? We will look at the different techniques used to spread. This signals your WiFi signals in the air. We will look at the GOODlE 2.4 gigahertz band, which is still used today, as you've just seen widely in access points in just about any WiFi product. There are some symptoms related directly to the 2.4 gigahertz band, and we will understand them. We will also look at the five gigahertz band, which is for the last couple of years became the standard. The five gigahertz band is the highway with an unlimited roads, and we will look at DFS and TPC built in mechanism that helps our network in different five gigahertz situations. We will start with a 2.4 gigahertz band, which is probably the most widely used. And let's understand some key terms. The 2.4 gigahertz frequency band starts from 2.4 gigahertz actitud 0.5 gears. The bed is actually a small section off the spectrum frequency. It is divided into portions, each five megahertz wide. In WiFi, we use channels which are actually aggregated portions. The band is divided into 13 channels. Each is 20 to 22 megahertz white. We represent channels by their center frequency. So, for example, Channel six, which is a 20 megahertz white Shano, an aggregated channel, is represented as 2437 megahertz. That is it. Speak frequency. And as you can see, it is actually spreading all over, starting from the fourth up to the eighth for portion off the band. So if we have turning channels occupying the band, you will see that only tree are not overlapping. So we have our WiFi signal sent in the 2.4 gigahertz frequency band to the air and how it is being spread it over the there. Well, as you will see, it is also a crucial criteria. The way they spread can be seen. There's a truck and is a racing car, the first spread spectrum technology that was used for many years. Instead, enders as 8 to 11 b was, he insists their success is like a truck. If a channel is the road in our highway, then the assistance is a truck that occupies the road from one side to the other. The signal is spreading over a range of frequencies. In the latest WiFi technologies we use always. Bm oh FGM is like a racing car. We don't just send the signal over the entire spectrum as DSF. Rather, it is being split ID to suck carriers 52 narrow bend with chunks, each on a different frequency. Oh, if the end is key to my mom, which is a topic we will deal in another video signals air scenting parlor and over a much longer time, sending so much sub carrier mixed decoding the signal much more reliable. Even if the signal is, we know the greats over distance you have a lot more signals that can be recovered. The 2.4 gigahertz frequency band is a narrow and so has its own symptoms as co channel interference and more Monda in the next chapter. 21. Frequencies part 2 symptoms: everyone. Thanks for coming back to WiFi fundamentals with location and analytics. This course will help you to muster the air in the first part. Off frequencies. We have mentioned that the 2.4 gigahertz band is narrow. It is narrow and it is used widely in many products and their symptoms. One of them is co channel interference. What is it? Well, imagine that you're in an area were to access points operate in 2.4 gigahertz under the same channel. Let's assume that is Channel One. What happens will think off the stations on each access points BSS they sense the air. Remember C S M A c A on Channel one. And although the stations on the second i p is not on their BSS, they hear their transmissions and have to wait. So the two access points area have become one which makes air time much smaller for each station. When co channel interference happens, old stations, as we know, listens to the direction value in its channel area. When deploying access points the shared the same channel, you should have a to least and minus 20 DBM or greater off separation to minimize the same channel interferes. Plan your channels effectively. Another bat symptom of the 2.4 gigahertz band is a Giessen Channel interferes dill, not on the same channel. We have to access point each operate under another channel, Let's assume is Channel one and Channel treat as Justin. Channel interference is one of the worst interferences out there. Imagine trying to talk in a coffee bar in a table near a rock band who placed the music very loud. They're noise will make your voice garbled and not understood. The same happens when two WiFi access point transmit they're noise will make frames damage . In return, we will have more rich transmissions, which means a slower decorate. The third symptom is that it is just crowded. 2.4 gigahertz is old over Bluetooth microwaves, Cordless phones, wireless camera, baby monitors all uses 2.4 gigahertz. Band and interferences can come from none able to 11 devices. None WiFi devices, which would make eventually you're single to noise ratio low. Let's try to recap. Frequency is our highway. The more wider, the more capacity it is, split it into rose. We call them channels the way we deliver goods on it is crucial. Is it on a semitrailer, a. D a success or a racing car? And oh, FTM and lust be aware that the highway roads are not overlapping. Next part moving to five gigahertz. See you then. 22. Frequencies 5ghz: everyone. Thanks for coming back to WiFi fundamentals with location and analytics. This course will help you to muster the air. We are moving to the five gigahertz band, and this one is a beast. Five gigahertz provides faster decorate at a shorter distance. Remember that the higher frequency, the shorter wavelength and attenuation is faster, but it's WiFi bend. The location is way bigger than two point for so much more bandwidth can be occupied, and the amount of devices using them is rare. Most Isom Ben Devices supports 2.4. We can see that it's in frequency band. There are so many 20 megahertz channels to choose from or to bond them together for a wider channel. It actually has six times capacity than the 2.4 and so 8 to 11 n and A C standards. Both introduce changes in the McClair that allows them to add bonded channels 8 to 11 and introduced High Truthful Channel A maximum off 40 megahertz channels able to 11. A see also supports very high triple channels up to 160 megahertz. Shano bonding is quite an amazing way to gain throughput, but being where at least 88 to 11. And when it comes to 2.4 gigahertz, band 40 megahertz channel will overlap with just about any other channel in your surrounding the NATO to 11 a. C. It is not an issue. You can use 40 megahertz channels. You can use 80 megahertz channels. Old oh is you will see in most cases in dense area. We used 20 to 40 megahertz channels and you can even use up to 160 megahertz. Channel 8 to 11 A see also applied a new channel naming They're numbered by their center channel in a 40 megahertz channels. That is the result Off Channel 36 40. The new channel will be called Channel 38 and when it comes to an 80 megahertz channel, there is the result off Channel 36 40 44 48. The new channel will be called Channel 42. Is there a good reason to use Weitz channels? Well, yes, it has much more true put but be aware 80 megahertz channels makes much more noise in the air than a 40 or 20 megahertz channel and co channel interference can still exist. If you're in high density area with a lot off 80 or 160 megahertz channels around, you're better to plan around the nun overlapping 40 megahertz channels and even 20 megahertz channels in an enterprise conditions. While I'm in the able to 11 a.m. 20 megahertz channels, my noise level is minus 96. Moving on to the 802 11 a C 80 megahertz white channels. We can see that my noise level actually increased twice. Minus 90. Tree a tree. TBN difference When we looked at their frequency table before we saw that they're part of it, were none. DFS Benz. What is the DFS? Well, five gigahertz is also the frequency off choice for radars. DFS is a dynamic frequency shift. Whenever access points senses that there is a raider around it, it looks for a new channel, and let's every station in its area know about it through the usage. Often 802 11 age message. It applies to the 50 to 50 up to the 57 50 megahertz band. Another mechanism is TPC, but this one is all about power management. It can work out when there is a raider around, or in case our excess point is in a very congested area, and it wants the stations to lower their power. So which one? To choose the 2.4 or the five gigahertz band? Well, there is no straight answer. Most access point nowadays are jewel bent. Just think of it as two cells in your environment. Each takes its own air time. Most station nowadays will prefer to connect to the five gigahertz frequency as it allows them. More throughput. We will see in many cases, that are a piece. Transmission power for the five gigahertz band is stronger from the 2.4 gigahertz. The reason is the short range of the five gigahertz frequency. Another popular feature of access points is Ben Steering Rx Respond detects five gigahertz supporting device and steer them to that frequency instead of the 2.4 gigahertz, which they probably would connect because off it's stronger signal. That's all. Next stop frames. See you soon