Wireless LANs Part 1

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Wireless LANsPart 1
Kelvin Hilton K319 k.c.hilton_at_staffs.ac.uk www.soc
.staffs.ac.uk/kch1
(The following is based on material originally
produced by J Champion)
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Objectives

• Network Classifications
• Wired
• Wireless
• Infrastructures
• Technologies
• Infrared
• NFC
• RFID

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Network Classifications

• What is a LAN/WAN
• There are two main types of network
  infrastructures
• Local Area Network (LAN)
• Wide Area Network (WAN)
• The classification for these types of networks is
  the distance that the data has to travel
• There is no exact formula to classify when a LAN
  becomes a WAN in a wired network!
• Consider, is the Staffordshire University email
  server part of a WAN as it is located in Stoke?
• Or a LAN as it is all one network?

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LAN Classifications

• The network servicing this campus is a example of
  a LAN
• All machines are attached and located close to
  each other
• Distance in network terms is classified by the
  number of hops travelled between one device and
  another
• Hops are the stages that information has to
  travel through to get to the destination

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Wireless LAN - Infrastructure

• In wired networks there is always an
  infrastructure
• Even if two people bring together laptops for a
  game, there will be a cable and a device to
  repeat the signal
• A Hub, Router or Switch on Ethernet
• In a Wireless network this may not be the case
• Devices may only be able to communicate for a few
  seconds and then they are out of range
• People may come together for a meeting and then
  move away again

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Wireless LAN - Infrastructure

• Types of wireless networks
• AD-HOC
• No pre planning of the network takes place
• Communications may happen for hours or seconds
• Using the Nokia N-Gage with friends is an example
  of this
• Business men in a meeting exchanging data
• Difficulty in routing data to these devices
• Infrastructured
• The network has been planned
• The structure would not change
• A office would be a good example of this

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Ad-Hoc Infrastructure

• These networks work as the devices come within
  the transmission distance of each other
• When these devices can be used to extend a
  network
• In this diagram Device B can not see the
  printer

Printer
Device B
Device A
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Ad-Hoc Infrastructure

• Ad-Hoc
• One device can be used to reach the device you
  actually require
• The packet is sent from Device B to A and then to
  the printer

Device A
Printer
Device B
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Ad-Hoc Infrastructure

• These networks are an active research area
• The technology works now
• The difficulty is working out a route through the
  network
• The route can change all of the time
• Each time a packet is sent to sort out a route
  this takes battery power on all devices
• With enough devices nothing but routing
  information will be sent
• Ad-Hoc protocol
• Mobile Ad-hoc Networks (MANET)
• This group is standardising the IP routing
  protocols
• (www.ietf.org/html.charters/manet-charter.html)

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Infrastructured

• This would be used to supplement the current
  network
• This allows for laptops (eg hot-desking)
• Reduces the amount of cables
• This reduces infrastructure costs
• Allows workers to operate where they want in the
  building
• Usually combined with wired infrastructure
• Examples would be central high power printers
• Planning is required
• Remember that a radio signal from one device is
  just interfering noise to another device
• The more interfering devices the less successful
  communications that can take place

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Infrastructured

• Planning is required to minimise the amount of
  interference
• This can be done by increasing the distance
  between high users of a system
• Different rooms for the devices
• Some building materials will dampen the signal
• Staffordshire University Octagon is an example of
  this kind building

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The Technologies
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Main Wireless Technologies

• Infrared
• Bluetooth (next week)
• NFC
• RFID
• WiFi

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Infrared
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Infrared (IrDA)

• Large installation base
• Most devices install these ports
• Phones
• Laptops
• Printers
• Not widely used for commercial applications!
• Standards defined by
• Infrared Data Association (IRDA) (www.irda.org)

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Infrared (IrDA)

• Operates by line of sight

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Infrared (IrDA)

• Infrared
• The data is encoded into pulses of Infrared (IR)
  light
• A television remote control works in the same
  manner
• Technology is suited to
• Short distances with all devices within a room
• It is purposely designed to operate at about 1
  meter
• This give IR security built-in as no one can
  listen to that conversion
• Data Rates
• Although IR is considered to be a slow technology
  it is developing (Microsoft are actively pushing
  IR)
• Serial IR 115.2 Kbps
• Medium ID 1.152 Mbps (Rarely Used)
• Fast IR 4 Mbps
• Latest phones, cameras, etc support this standard
• Very Fast IR 16 Mbps
• Microsoft Windows XP supported only

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Infrared (IrDA)

• Advantage of the line of sight problem is that
  the communications are not shared
• The devices need to be within a 300 arc of each
  other
• Once the receiver and sender have agreed a
  transmission speed very little can interfere with
  this
• This reduces the overhead on communications
• Collisions do not need detecting
• Secure communications layer does not need adding

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Infrared (IrDA)

• The IrDA communication model
• Recall the OSI 7 Layer Model
• This is a network standard that defines what
  communications should take place and at which
  stage
• There are 7 layers to the stack
• Each layer carries out a specific task
• Each layer can only communicate with the layer
  above or below
• All other network protocols map (at least
  logically) to this stack

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Infrared (IrDA)

• OSI 7 layer communications model
• Communication between devices using the stack
• Packet of information going from Device 1 to
  Device 2

Device 1
Logically
Device 2
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Infrared (IrDA)

• Infrared Communication Stack
• Only the layer above and below can communicate
  with a point in the stack

IAS
irLAN
OBEX
irCOMM
TinyTP
Optional
irLMP
Required
irLAP
Physical
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Infrared (IrDA)

• Physical
• Defines encoding/decoding of data and
  transmission of the signal
• IRLAP
• Link Access Protocol
• Responsible for ensuring a reliable transport of
  data
• IRLMP
• Link Management Protocol
• Multiplexes services and applications together to
  use the one connection for transport
• IAS
• Information Access Service
• Allows knowledge of the capabilities/services of
  the device

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Infrared (IrDA)

• Optional uses of IR
• TinyTP
• This is a version of transport protocol designed
  specifically for IR
• Flow control is offered ensuring that device
  buffers do not overflow
• Maximum packet sizes are agreed by devices
• Large packets can be broken into smaller parts
• irOBEX
• Object exchange protocol
• Allows transfer of files easily between devices
• irCOMM
• Allows emulation of serial and parallel ports
• The applications do not need to know that they
  are using IR
• Legacy applications will work with this a printer
  is an example
• irLAN
• Allows LAN access for the devices
• Mainly used to allow LAN access through a device
  which is already connected to the network

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Infrared (IrDA)

• So why is not widely used?
• Although newer versions of the technology are
  fast the image is still for a slow technology
• Sun light
• The sun gives off IR and as such in bright light
  this will effect the operation
• Makes operation in the open awkward
• Positioning
• The devices need to be in line of sight, which
  means that they need moving from there normal
  position
• The distance between the devices can effect the
  rate of transfer
• Too close can be as bad as too far!

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NFC
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Near Field Communication (NFC)

• Problem with most network technologies is setup
• Non-techies struggle with configuring connections
• Not really suitable for consumer electronics
• Near Field Communication Interface and Protocol
  (NFCIP-1)
• Targeted at removing the need for expert
  knowledge to establish wireless comms
• Idea is for a short range technology that
  automatically handles all communication set-up,
  hand-shakes, etc
• Facilitate connection to other wireless
  technologies
• Eg Bluetooth

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NFC Properties (1)

• Short-range peer-to-peer protocol (0 - 20cm)
• Operates on 13.56 MHz unregulated frequency so no
  license required
• Half-duplex
• Listen before talk policy
• Two logical entities
• Initiator
• Initiates and controls data exchange
• Target
• Responds to Initiator

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NFC Properties (2)

• Two modes of operation
• Active mode
• Both devices generate radio signal to carry data
• Passive mode
• Only one device generates the signal (the
  Initiator)
• Save power on limited energy devices such as
  mobile phones
• Four transfer rates have been specified
• 106, 212 or 424 kbit/s
• Adaptive
• Capability dependent
• Terminated on command or if distance gt 20 cm

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NFC Properties (3)

• Short-range provides two inherent benefits
• Security from interference
• Common connection metaphor
• Designed to be used with other protocols and thus
  automate their connection process
• Inherent support for contactless Smart Card
  protocols
• Supports both cards and readers

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NFC Management

• Being developed by ECMA International
• (www.ecma-international.org)
• Including partnerships with many industry leaders
• Eg Sony, Phillips
• Insinuated into ISO/IEC and ETSI standards
• NCFIP-1 published 2003 (ECMA-340)
• NCFIP-2 (ECMA-352)
• Adopted by ISO/IEC JTC1 as ECMA-340

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NFC Example 1 Data Transfer
Source ECMA/TC32-TG19/2004/1
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NFC Example 1 Data Transfer
Source ECMA/TC32-TG19/2004/1
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RFID
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Introduction

• Ever wondered what one of these may be?
• Books
• Videos
• CDs
• DVDs
• Games
• Clothing

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Origins of RFID

• Radio Frequency IDentification is a means of
  automatically identifying something by means of
  radio frequency transmission
• Multiple sources
• Espionage in 1945
• 1939 used to identify aircraft
• Harry Stockman Communication by Means of
  Reflected Power (Proceedings of the IRE, 1948)

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Fundamentals of RFID

• Tag aka transponder
• Scanner aka interrogator

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Fundamentals of RFID Cont
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Classifications of Tags

• Three classes
• Passive RFID
• Tag has no internal power
• Minute electrical current provided by incoming
  radio signal
• Small devices (0.4mm x 0.4 mm)
• Semi-passive RFID
• Integrate small battery for powering CMOS
• Active RFID
• Longer range, larger memories
• Battery life of up to 10 years

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Basic Tag Architecture
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Security

• Major concerns
• Illicit tracking
• Cloning/duplication
• Industrial Sabotage/Espionage
• Jamming
• Cryptography
• Rolling code scheme
• Challenge-Response
• Increased costs/weak encryption

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The Future?

• Implanted RFID
• Animal tracking
• Identity Fraud
• Secure Building Access
• Computer Access
• Medical
• Anti-Kidnapping
• Law Enforcement

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The Bourne Identity

• 2005 Washington business person has tag inserted
  for personal use

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Review

• Network Classifications
• Wired
• Wireless
• Infrastructures
• Technologies
• Infrared
• NFC
• RFID

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Questions?