WiFi Networking

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WiFi Networking
LUCID Summer Workshop August 2, 2004
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WiFi

• WiFi is the wireless way to handle networking.
• It is also known as 802.11 networking.
• The big advantage of WiFi is its simplicity.
• You can connect computers anywhere in your home
  or office without the need for wires. The
  computers connect to the network using radio
  signals, and computers can be up to 100 feet or
  so apart.

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Outline for Today

• The next slides, we will discuss the basic
  technology that makes WiFi networking possible.
• Then we will discuss the hardware you need to
  create a WiFi network, and help you understand
  how to set up and access a WiFi hotspot in your
  home.
• Finally, we will look at a demonstration by
  Dimitri Demergis.

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Wireless Networking Standards

• WiFi refers to the protocols that allow wireless
  networking.
• These protocols are codified in standards.
• Standards are mutually agreed upon rules adopted
  by the industry on how the wireless networks
  operate.
• There are several standards that enable wireless
  local area networks (WLANs).

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Wireless Networking Standards

• Some WLAN standards include HiperLAN,
  Bluetooth, HomeRF.
• There are a couple of standards that describe
  Wi-Fi. All of them are part of the 802.11 suite.
• The core protocols are listed in the 802.11
  standards, which was originally available in 1997.

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802.11 Suite

• Since then, several new extensions have been
  added to the core 802.11 protocols.
• The most relevant of these additions are
  802.11a, 802.11b, and 802.11g.
• Next time, we will look at this core protocol
  (802.11) and these three expansions in more
  detail.

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Understanding Wireless Networking
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Walkie-Talkie Network

• If you want to understand wireless networking at
  its simplest level, think about a pair of 5
  walkie-talkies that you might purchase at
  Wal-Mart.
• These are small radios that can transmit and
  receive radio signals.
• Recall, when you talk into a Walkie-Talkie, your
  voice is picked up by a microphone, encoded onto
  a radio frequency and transmitted with the
  antenna.

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Walkie-Talkie Network (Contd)

• Another walkie-talkie can receive the
  transmission with its antenna, decode your voice
  from the radio signal and drive a speaker.
• Simple walkie-talkies like this transmit at a
  signal strength of about 0.25 watts, and they can
  transmit about 500 to 1,000 feet.
• We wish to consider how these walkie-talkies can
  be used to communicate between the two computers.

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Walkie-Talkie Network (Contd)

• In order to do this, we require
• Each computer is equipped with a walkie-talkie.
• We would give each computer a way to set whether
  it wants to transmit or receive.
• And we would give the computer a way to turn its
  binary 1s and 0s into two different beeps that
  the walkie-talkie could transmit and receive and
  convert back and forth between beeps and 1s/0s.

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Walkie-Talkie Network (Contd)

• This would actually work.
• The only problem would be that the data rate
  would be very slow. A 5 walkie-talkie is
  designed to handle the human voice (and it's a
  pretty scratchy rendition at that), so you would
  not be able to send very much data this way.
  Maybe 1,000 bits per second.
• Another problem the walkie-talkies could not be
  used to connect to the internet.

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WiFis Radio Technology

• The radios used in WiFi are not so different from
  the radios used in 5 walkie-talkies.
• They have the ability to transmit and receive.
• They have the ability to convert 1s and 0s into
  radio waves and then back into 1s and 0s.
• There are major differences, of course.

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WiFis Radio Technology (Contd)

• WiFi radios that work with the 802.11b and
  802.11g standards transmit at 2.4 GHz, while
  those that comply with the 802.11a standard
  transmit at 5 GHz.
• Normal walkie-talkies normally operate at 49 MHz.
  The higher frequency allows higher data rates.
• WiFi radios use much more efficient coding
  techniques (process of converting 0s and 1s
  into efficient radio signals) that also
  contribute to the much higher data rates.

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WiFis Radio Technology (Contd)

• The radios used for WiFi have the ability to
  change frequencies.
• For example, 802.11b cards can transmit directly
  on any of three bands, or they can split the
  available radio bandwidth into dozens of channels
  and frequency hop rapidly between them.
• The advantage of frequency hopping is that it is
  much more immune to interference and can allow
  dozens of WiFi cards to talk simultaneously
  without interfering with each other.

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802.11b, 802.11a, and 802.11g

• 802.11b was first to reach the marketplace. It is
  the slowest and least expensive of the three.
  802.11b transmits at 2.4 GHz and go up to 11
  Mbps.
• 802.11a was next. It operates at 5 GHz and can
  handle up to 54 Mbps.
• 802.11g is a mix of both worlds. It operates at
  2.4Ghz (giving it the cost advantage of 802.11b)
  but it has the 54 megabits per second speed of
  802.11a. It is also backward compatible to
  802.11b.
• Most WiFi cards nowadays are capable of all three
  of these radio technologies.

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Adding WiFi to Your Computer

• One of the best things about WiFi is how simple
  it is.
• Many new laptops already come with a WiFi card
  built in -- in many cases you don't have to do
  anything to start using WiFi.
• It is also easy to add a WiFi card to an older
  laptop or a desktop PC.

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Adding WiFi to an Older Computer

• Buy a 802.11a, 802.11b or 802.11g network card.
• For a laptop, this card will normally be a PCMCIA
  card that you slide into a PCMCIA slot on your
  laptop. Or you can buy a small external adapter
  and plug it into a USB port.
• For a desktop machine, you can buy a PCI card
  that you install inside the machine, or a small
  external adapter that you connect to the computer
  with a USB cable.
• Install the card

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Adding WiFi to an Older Computer

• Install the drivers for the card
• Find an 802.11 hotspot.
• Access the hotspot.
• Hotspot a connection point for a WiFi network.
  It is a small box that is hardwired into the
  Internet. The box contains an 802.11 radio that
  can simultaneously talk to up to 100 or so 802.11
  cards.

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Locating Hotspots

• There are many WiFi hotspots now available in
  public places like restaurants, hotels, libraries
  and airports. For example, Starbucks.
• The number of hotspots in the world is growing
  daily.
• You can also create your own hotspot in your
  home, as we will see in a little bit.
• One way to find a hotspot is to go on-line.

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Finding Hotspots O-Line
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Connecting to a Hotspot

• There are actually two steps to making a
  connection.
• The first is to have your notebook "talk" to the
  hotspot, which means that the hardware and
  hotspot must recognize each other. This should
  happen automatically as long as your wireless
  hardware is turned on and new.

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Connecting to a Hotspot (Contd)

• On the newest machines, an 802.11 card will
  automatically connect with an 802.11 hotspot and
  a network connection will be established. As soon
  as you turn on your machine, it will connect and
  you will be able to browse the Web, send email,
  etc. using WiFi.
• On older machines you often have to go through a
  simple 3-step process to connect to a hotspot.

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Connecting to a Hotspot (Contd)

• Access the software for the 802.11 card --
  normally there is an icon for the card down in
  the system tray at the bottom right of the
  screen.
• Click the "Search button" in the software. The
  card will search for all of the available
  hotspots in the area and show you a list.
• Double-click on one of the hotspots to connect to
  it.

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Connecting to a Hotspot (Contd)

• On ancient 802.11 equipment (more than 2-3 years
  old), there is no automatic search feature.
• You have to find what is known as the SSID of the
  hotspot (usually a short word of 10 characters or
  less) as well as the channel number (an integer
  between 1 and 11) and type these two pieces of
  information in manually.
• All the search feature (in newer equipment) is
  doing is grabbing these two pieces of information
  from the radio signals generated by the hotspot
  and displaying them for you.

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Connecting to a Hotspot (Contd)

• On most notebook models, you will see some sort
  of signal icon on the bottom right hand corner of
  your screen or a lit indicator on the notebook
  itself, which will give you feedback for "On" and
  signal strength (a red screen means your radio is
  Off a green screen indicates it is On).

OFF
ON
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Connecting to a Hotspot (Contd)

• You can also see the quality of the signal by
  clicking on the radio icon (may vary by system)
  

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Connecting to a Hotspot (Contd)

• Your next step is to sign up with a wireless
  Internet service provider and configure your
  notebook according to their instructions.
• Most of the time, this is a matter of simply
  launching your web browser. It will automatically
  go to the wireless service provider's sign-in
  page.
• Keep in mind that different hotspot locations
  work with different service providers, but each
  hotspot location should provide easy and clear
  instructions on how to connect.

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Connecting to a Hotspot (Contd)

• If you don't subscribe to a service, chances are
  you will need to use your credit card to pay for
  access every time you want to connect.
• Always make sure you know what the service
  provider charges, as there can be a wide range of
  prices.
• After this, you will end up at the log-on page of
  the wireless provider (or, in some cases, the
  wireless location).

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Connecting to a Hotspot (Contd)

• If so, simply follow the instructions to sign up
  for the service, or enter your user name and
  password if you are already a customer.
• Once you successfully log on, you should see the
  following icon in your tool bar, indicating the
  connection has been made

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WiFi Security

• WiFi hotspots can be open or secure.
• If a hotspot is open, then anyone with a WiFi
  card can access the hotspot.
• If it is secure, then the user needs to know a
  WEP key to connect.
• WEP stands for Wired Equivalent Privacy

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WiFi Security (Contd)

• WEP is an encryption system for the data that
  802.11 sends through the air.
• Encryption system prevents any non-authorized
  party from reading or changing data.
• Specifically, it is the process of encoding bit
  stream in such a way that only the person (or
  computer) with the key (a digital sequence) can
  decode it.

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WEP

• WEP has two variations 64-bit encryption (really
  40-bit) and 128-bit encryption (really 104-bit).
• 40-bit encryption was the original standard but
  was found to be easily broken.
• 128-bit encryption is more secure and is what
  most people use if they enable WEP.
• For a casual user, any hotspot that is using WEP
  is inaccessible unless you know this WEP key.

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WEP (Contd)

• If you are setting up a hotspot in your home, you
  may want to create and use a 128-bit WEP key to
  prevent the neighbors from casually eavesdropping
  on your network.
• Whether at home or on the road, you need to know
  the WEP key, and then enter it into the WiFi
  card's software, to gain access to the network.

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Setting up a Hotspot at Home

• If you already have several computers hooked
  together on an Ethernet network and want to add a
  wireless hotspot to the mix, you can purchase a
  Wireless Access Point and plug it into the
  Ethernet network.

Wireless Access Point
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Setup 1
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Alternate Setup using a Wireless Router

• If you are setting up a network in your home for
  the first time, or if you are upgrading, you can
  buy a Wireless Access Point Router.
• This is a single box that contains
• 1) a port to connect to your cable modem or DSL
  modem,
• 2) a router,
• 3) an Ethernet hub,
• 4) a firewall and
• 5) a wireless access point.
• You can connect the computers in your home to
  this box either with traditional Ethernet cables
  or with wireless cards.

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Alternate Setup (Contd)
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WiFi Range

• Regardless of which setup you use, once you turn
  your Wireless Access Point on, you will have a
  WiFi hotspot in your house.
• In a typical home, this hotspot will provide
  coverage for about 100 feet (30.5 meters) in all
  directions, although walls and floors do cut down
  on the range.
• Even so, you should get good coverage throughout
  a typical home. For a large home, you can buy
  inexpensive signal boosters to increase the range
  of the Hotspot.

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One Type of Amplifier
Or a directional antenna can be used to
give better range in a particular direction.
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Another Way to Amplify WiFi Signals
A WiFi repeater is installed to extend coverage.
Wireless Access Point
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Configuring a Hotspot

• Most wireless access points come with default
  values built-in.
• Once you plug them in, they start working with
  these default values.
• However, you may want to change things.
• You normally get to set three things on your
  access point.

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Things to Configure in a Hotspot

• The SSID -- Service Set IDentifier is a sequence
  of charactersthat uniquely names a WLAN.
• It will normally default to the manufacturer's
  name (e.g. "Linksys" or "Netgear").
• You can set it to any word or phrase you like.
• The channel the radio link used by access
  point/router to communicate to wireless devices.
• Normally it will default to channel 6.
• However, if a nearby neighbor is also using an
  access point and it is set to channel 6, there
  can be interference. Choose any other channel
  between 1 and 11.

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Things to Configure (Contd)

• The WEP key -- The default is to disable WEP.
• If you want to turn it on, you have to enter a
  WEP key and turn on 128-bit encryption.
• WEP can be in text format.
• Access points come with simple instructions
  for changing these three values. Normally you do
  it with a Web browser. Once it is configured
  properly, you can use your new hotspot to access
  the Internet from anywhere in your home.

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Infrastructure versus Ad Hoc

• All the connections that we have talked about
  today require a connection from a device equipped
  with a wireless network interface card (NIC) to a
  wireless access point.
• Generally, all such connections are operating in
  what is known as the infrastructure mode. Here
  the wireless network resembles a cellular
  architecture.
• Wireless devices can also communicate directly
  with each other, i.e., it is not required that
  they communicate with an access point first.

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Infrastructure versus Ad Hoc

• When devices with NIC cards communicate directly
  with each other, the wireless network operates in
  ad hoc mode.
• Essentially peer-to-peer communication is
  enabled.

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Ad Hoc Mode

• Ad Hoc connections can be used to share
  information directly between devices. This mode
  is also useful for establishing a network where
  wireless infrastructure does not exist.
• Some uses,
• Synchronize data between devices.
• Retrieve multimedia files from one device and
  play them on another device.
• Print from a computer to a printer without wires.
• There are many applications of ad hoc networking
  in the military and in specialized networks.

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Demo and Next Time

• Next, we will look at some demonstrations of WiFi
  networks operating in infrastructure mode.
• Next time, we will look at a demonstration of the
  ad hoc mode.
• Next time, we will also look at the protocols
  that enable all this WiFi networking.