Let's now take a look at the technical WiFi deployment and the text and terms
that we see when we look at deployment. So, we'll refer to this diagram
throughout this slide. So, the first thing we'll see is what's
called a basic service set and we can draw analogies here to sign their
networks because though WiFi and cellular have very different ways of actually
sharing the medium and different devices when we look at the technical way of that
It's done. Their topology is the way that they're
laid out are actually very similar. So a basic service set is similar to the
idea of a cell. And we call that a BSS for short.
And Basic Service Set has a bunch of components in it.
So this is a BSS, one of these circles in here.
obviously devices like your laptops, or Your smartphone which can access the
internet. An Access Point or an AP, we call it for
short, that's similar to the idea of a bay station.
So that's what's going to actually give your device access to the internet
through WiFi. And each access point is identified by
what's called a service set identifier or an SSID.
And what an SSID really is or those things that you see on your screen like
when you go into your settings, you know to connect to your WiFi network you may
see some different SSIDs and if your in public you'll see Probably more of them
than if you're sitting in your house you're probably going to see one or maybe
your neighbor's as well. But when you see these names, these catch
phrase names like Optimum WiFi or other network and then you see your signal
strength next to it. And so you could connect to these SSIDs
and it'll put you on a different access This point so which access point will
have a different SSID. And some of those SSIDs are locked so,
you can't get on a network if it's protected and you don't have a password
if you're not a paying subscriber of whatever network it is that you're
looking at. So then there's the idea beyond just the
basic service set, which just practice out is that in general we can also have
what are called extended service sets or ESSs.
So, we still have your basic service set. An ESS is you can look at it like a
collection of basic service sets which have more than one access point within
them. And they support roaming capabilities.
So, if your device could maybe move from here into here and then it could also
access, get onto this access point. or that access point would actually
broadcast the same SSID. So, these two if they were going to form
an extended service set. And ESS, they would broadcast the SSID.
And so in a house or in a home you would only have one basic service set typically
or in a Starbucks or anywhere that you're going to go.
'Cause there's probably only one access point.
But if you go to a hotel or a large building there may be multiple access
points that support roaming, so you don't actually notice even when you switch
between them. But then if you move over to this service
set over here, which is an extended service set you can actually then connect
to this other device. So, an ESS is a collection of basic
service sets that readily support roaming capabilities, and then beyond the basic
service sets they're all really tethered to the backhaul.
And there's a backhaul network up there, that's typically ethernet, that's
probably a common name that you hear for a backhaul network which then goes up
into what's called the access network and the access network is the bridge between
the backhaul and the rest of the internet.
So we won't really distinguish, right now at least, between the backhaul, and the
access, and we won't look at that much in this course.
But we will focus a lot on the internet in later chapters, and just know that
between the basic service sets, there's a few more sets that you'd go before you
get to the quote, unquote. Internet cloud up here and, so now where
is WiFi? Lets, lets take a look at a few examples
and first is in a home and we can look at a typical home declaimer just to give you
more of an idea what do these terms really mean, so in your house you Have a
router. And it's your router if it supports WiFi
it was called to the via Wifi Router or Wireless Router.
And then basically you form a BSS of all the devices in your house that have WiFi
on it. So, any device that's connected to the
WiFi will become part of this basic service set.
And then this is the access point. The WiFi Router becomes the access point.
This point and all your devices in here and the WiFi Router itself though it may
also not just have wireless devices like your desktop computers or if your laptop
if it's connected directly in would be over ethernet or a wired connection.
So, Ethernet the standard wired protocol. And that's roughly speaking you would say
that the ethernet protocol runs on the wires.
But we really call them Ethernet cables and common speech, and then beyond the
Wifi router it connects back to a modem. And actually more and more today even
routers and modems are in one device, so you may actually have one of these boxes,
but then you're connecting to a modem, and then outside of your house you have
the access network then, and the access network would be for instance cable, or
it could be fiber so fiber is common. For instance, if you have FIOS or you
could have DSL or anything along those lines.
So, those are all access network names. So another place beyond the home is in
hotspots. For instance in June 2012 something,
interesting, US providers, five major cable providers in the US.
Agree to quote unquote join forces and actually connect all their hotspots into
a single service. You can actually look more up on that if
you want and you can blog or write a Wikipedia article on it, that would be a
good thing to look into, and in addition to hotspots even street corners nowadays
in certain countries. For instance, in Korea, Seoul plans to
have their entire city covered, the entire city of Seoul, all the street
corners, everywhere that you go should be able to have WiFi they claim by 2015.
So we em at home, we see them at hotspots, even more and more now we're
seeing them at street corners. Eventually you have to wonder will
everywhere be covered by WiFi if we wanted.
So will we have the choice between WiFi or cellular where ever we go.
[BLANK_AUDIO]
Christopher BrintonLecturer
Mung ChiangProfessor
