WIRELESS LAN

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WIRELESS LAN PDA

• CIS 454 (LAN)
• Prof. Ganesan

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Group members outline

• Belinda
• Wireless LAN
• Anthony Vu
• Topology wireless technology of LAN
• Ka Yan (Susana) Chung
• Implementation of wireless LAN
• Norman-Ngan Vu Lam
• Personal Digital Assistant (PDA)

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WIRELESS LAN

• WIRLESS LOCAL AREA NETWORK

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INTRODUCTION

• It is a flexible data communications system
  implemented as an extension to, or as an
  alternative for, a wired LAN.
• Using radio frequency (RF) technology, wireless
  LANs transmit and receive data over the air,
  minimizing the need for wired connections.
• With wireless LANs, users can access shared
  information without looking for a place to plug
  in, and network managers can set up or augment
  network without installing or moving wires.

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WHY WIRELESS?

• Wireless LANs offer the following
• Productivity, convenience, and cost advantages
  over traditional wired networks
• MOBILITY
• INSTALLATION SPEED AND SIMPLICITY.
• INSTALLATION FLEXIBILITY.
• REDUCED COST-OF-OWNERSHIP.
• SCALABILITY.

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MOBILITY

• Wireless LAN systems can provide LAN users with
  access to real-time information anywhere at work
  and in the home.

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INSTALLATION SPEED AND SIMPLICITY

• Installing a wireless LAN system can be fast and
  easy and can eliminate the need to pull cable
  through walls and ceilings.

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INSTALLATION FLEXIBLITY

• Wireless technology allows the network to go
  where wire cannot go.

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REDUCED COST-OF-OWNERSHIP

• While the initial investment required for
  wireless LAN hardware can be higher than the cost
  of wired LAN hardware, overall installation
  expenses and life-cycle costs can be
  significantly lower. Long-term cost and benefits
  are greatest in dynamic environments requiring
  frequent moves and changes.

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SCALABILITY

• Wireless LAN systems can be configured in a
  variety of topologies to meet the needs of
  specific applications and installations.
  Configurations are easily changed and range from
  peer-to-peer networks suitable for a small number
  of users to full infrastructure networks for
  thousands of users that enable roaming over a
  broad area.

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OVERVIEW BY INDUSTRY

• Currently wireless LAN is not a replacement for
  the wired infrastructure, but it is a significant
  complement to what currently exists. Some
  examples in the industry are
• EDUCATION.
• MANFACTURING COMPANIES.
• HEALTHCARE.
• RETAIL.
• FINANCIAL/OFFICE-AUTOMATION.

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MAJOR FINDINGS IN THE INDUSTRIES

• 89 Of the companies experienced a successful
  implementation.
• 92 of respondents interviewed believe there is a
  definite economic and business benefit after
  installation.
• 92 of respondents reported that they will
  continue to deploy wireless technology in their
  network through 2000 because of the benefits
  experienced by end users and/or IT staff.
• Payback was less than one year, across all
  industries surveyed.

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Cost Chart
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Wireless Topology

• Topologies are architectural drawings
  representing the cable layout for the wireless
  LAN.
• Topologies of a network are the physical
  configuration of the nodes in the network.
• They can be hardware dependent.

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Topologies
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Star Topology (Centralized)

• Star topology is probably the oldest topology
  used for data communication.

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Star Topology (cont)

• Computers are connected through a series of
  point-to-point dedicated circuits.
• Each computer is linked by a separate full-duplex
  point-to-point through the central computer.
• It is easy to set up.

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Bus Topology

• Star topology is sometimes known as the
  linear-bus topology.
• All terminals share a single cable to transmit
  and receive messages.
• There are endpoints to cable segment commonly
  known as terminating points.

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Physical Bus Topology
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Ring Topology

• In the ring topology, all computers are connected
  in a close loop.
• Each computer links to the next one.
• There is no endpoints to this cable topology.
• Messages can travel around the ring in one
  direction.

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Physical Ring Topology
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Speed and Distance

• Transmission speed worsens problems
• Error rates increase because bit periods are
  smaller and are more likely to be damaged by
  brief noise spikes and interference.
• High speeds create high-frequency components in
  the signal that attenuate more rapidly than
  lower-frequency components.
• In general, as speed increases, maximum distance
  decreases, although improving technology can
  lessen the decrease.

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Applications According to Electromagnetic Spectrum
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How cellular phone works ? (cont.)

• This process takes the same amount of time that
  it takes to make a call from a landline phone.
• 
  
• 
  
• 
  

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Solid Objects
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Between Office Buildings
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How Does Satellite Work?

• Communication
• Frequency
• Uplink downlink

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Between Ground Unit and Satellite
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Attenuation

• As signal travels, gets weaker
• If too weak, cannot tell 1s and 0s

Distance
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Distortion

• As signal travels, it become distorted
• Changes shape
• Successive bits may merge, making reception
  difficult

Distance
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Noise

• Unwanted energy on line. Always present
• Noise floor is average level
• Noise spikes will cause problems

Signal
Signal Strength
Spike
Noise
Noise Floor
Time
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Approaching the Noise Floor

• Attenuation will bring signal ever closer to the
  noise floor, creating more errors

Signal Strength
Signal
Noise Floor
Distance
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Interference

• Unwanted signal from outside sources
• Often intermittent, difficult to diagnose

Signal Strength
Signal
Interference
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Implementation of Wireless LAN
by Susana
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Wired Vs. Wireless LAN.

• Wired LAN transmit data in cables such as twisted
  pair, coaxial, and fiber optic cable.

• Wireless LAN transmit data in air, it use
  infrared (IR) or radio frequency (RF) to transmit
  data on air.

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Radio Frequency (RF)

• Microwave transmission - high frequency, narrow
  band radio waves that require special license.
• Spread spectrum - spread signal over a range of
  frequency, therefore, harder to intercept

• RF electromagnetic wave can easily pass through
  ordinary wall, it needs to implement with heavy
  concrete or metal screening.

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Infrared (IR)

• Indoor infrared is the most secure wireless LAN,
  its the easiest types of wireless signal to
  contain with a certain location. Also, no
  license needed.
• Use to connect nodes over small distance.

• Point-to-point infrared must be within sight of
  each other with no obstacles in the path of
  signal.
• Signal would be weaken by moist environment,
  dusty environment, person in signal path, and
  sheet of plastic.

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Wireless LAN Hardware Implementation

• A wireless NIC - connect nodes to transmission
  medium. Allow communication between node and
  network. Consist of on board transceiver,
  fix/external antenna.
• For PC, wireless NIC are either PCI/ISA, for
  laptop, it uses PCMCIA type II card.
• Installs driver to configure NIC.
• Another option of wireless LAN implementation is
  wireless LAN adapter - external desktop
  transceiver and antenna connect to PC through
  parallel port and it function like a NIC.

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Wire Replacement System

• It use wireless transmission instead of cabling
  to communicate with backbone.
• Make use of existing Ethernet .
• Use device called user modules and control
  modules.
• User module is a desktop transceiver and antenna
  can be shared with up to 8 nodes with Ethernet
  cards that are individually wired to the user
  module.
• Control modules are similar to AP, it allow
  communication with wired backbone through control
  modules.

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Data-link Layer
OSI 7 layers

• Data-link layer of the OSI model governs a nodes
  access to a shared medium.
• Logical link control (LLC) layer deal with
  communication between nodes over a single link of
  network.
• Media access control (MAC) layer which define how
  user obtain access to the shared medium when they
  need it.

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Different Types of MAC

• Random Access MAC
• Ordered MAC
• Deterministic MAC

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Random Access MAC

• Simple to implement
• Offer fast response time under light network
  traffic
• Offer effective throughput under heavy traffic
• Wired network use CSMA/CD protocol to ensure data
  transmit efficiently (it checks if line is free,
  then transmits and listen if theres collision,
  if collision, it stops and waits for re-send)
• Wireless NICs cant transmit and receive on the
  same frequency at the same time, therefore, it
  cant detect collisions.

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Random Access MAC (continue)

• Wireless NIC might not aware of all other node on
  network - known as hidden node (a node outside
  of coverage area) Wireless network use CSMA/CA -
  Carrier sense multiply access with collision
  avoidance. Also known as LBT - Listen before you
  talk. (Check if line I free, if yes, send and
  wait for acknowledgment for receiving node, if no
  acknowledgement receive within set period of
  time, it assume a collision occur and wait to
  re-send)
• CSMA/CA cant be use when theres hidden node
• CSMA/CA cam be adapted to use with hidden node
  with the use of RTS/CTS/ACK - request to
  send/clear to send/acknowledge.

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Ordered MAC

• Ordered MAC is unsuitable for wireless LAN
  because it is possible for a node to leave the
  bus or ring and break the orders

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Deterministic MAC (3 types)

• 1) Time division multiple access (TDMA) - each
  node given the same set amount of time to
  transmit data.
• -Another type of TDMA is reservation/polling MAC
  - node sends request to control point to request
  channel, channels are issue on a first come
  first serve base.
• 2) Frequency division multiple access (FDMA) -
  available bandwidth is divide into channels of
  different frequency and nodes allocate a
  particular frequency.
• 3) Code division multiple access (CDMA) - nodes
  share same channel bandwidth but use different
  spreading code to prevent interference.

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Deterministic MAC (continue)

• Deterministic MAC provide effective throughout
  and response time when network traffic is heavy.
  
• Each node must request access from control point
  before transmitting, therefore, deterministic MAC
  have slower response time than Random Access MACs
  in light traffic conditions.

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CSMA/TDMA

• Combination of random-access MAC and
  deterministic MAC technique is called CSMA/TDMA.
  It offers fast response time in light traffic
  effective throughout under heavy, but more
  complexes to administer on the network
• CSMA/CA, RTS/CTS/ACK and CSMA/TDMS are suitable
  for wireless networks.

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Access Point (AP)

• Access Point are consists of
• 1) A wired NIC to communicate with wired backbone
• 2) A transceiver and antenna to communicate with
  wireless node within range
• 3) MAC-layer bridging software.
• AP can be use to extend the range of a wireless
  network or connect an existing wired LAN to a
  wireless LAN.

• Wireless subnets are connected to a wired
  backbone through AP.
• AP bridging ensure only packet destined for
  wireless nodes within its service are forwarded
  to the wireless subnet.

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Bridging

• Bridging - device that filters traffic between
  different section of the same network, of
  different LAN
• It acts like a repeater, sends data to both
  wired and wireless network.

1) Bridging software processes data and analyzes
address info on packet. 2) It construct a table
indicate location of each node. 3) Each time it
receives packet, it checks if destination address
is in table 4) If address to wired LAN, it checks
if on table, if yes, only forward to wired LAN,
if not, it forward to both wired and wireless.
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Bridging (continue)

• There are 2 ways to create table
• 1) Source route algorithm - entire path of the
  package is included in each frame and bridge
  record information, most of the routing work is
  performed by nodes.
• 2) Spanning tree algorithm - used by most
  network, bridge notes the direction from which it
  receives each packet and concludes source node
  can be reach by sending packet in that direction
  and record it in table. It regularly exchange
  configuration message with other bridge, if one
  fails, network can adjust routing accordingly.
• Bridge-to-bridge protocol ensures each network
  section can only access through a designated
  bridge.
• Table is not permanent. For wired LAN, entries
  age out in hours in wireless LAN, entries age
  out in minutes.

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Mobile IP

• Wired nodes IP address associate with a
  particular physical location wireless node is
  addressed by a protocol called Mobile IP.
• Mobile IP allows nodes to take an IP address with
  them when they move.
• Wireless node using mobile IP is known as a
  mobile host.
• Mobile host can have 2 IP address at a time, one
  is home address which is permanent the other is
  care of address which is temporary.
• Foreign agents provide mobile host with care of
  address and home agents redirect package from
  home network to care of address.

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Security

• Encryption is an effective security technique,
  there are 2 types of encryption technique.
• 1) DES chip - is a symmetric encryption method,
  use same key for encrypting and decrypting.
• 2) RSA - is an asymmetric encryption method, use
  different key encode and decode. Data is
  encoded using public encryption key, and
  decoded using private key.
• Symmetric encryption is faster than asymmetric,
  but possible security risk.
• Only encrypting sensitive message at higher
  application level before transmitting can reduce
  processing time.

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PERSONAL DIGITAL ASSISTANT(PDA)

• By
• Norman-Ngan Vu Lam

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What is PDA?

• Personal Digital Assistant
• A handheld PC that is capable of handling all the
  normal task of the organizer and more.

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Features of PDA

• All Palm organizers include the following
  features
• Applications Date Book, Address Book, To Do
  List, Memo Pad, Expense, Calculator, desktop
  e-mail connectivity, Security, Games, and
  HotSync software for local and remote
  synchronization
• Modem-enabled and Internet-ready with TCP/IP
  software
• An infrared port
• Windows and Macintosh compatibility

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Palm VII

• Check stock quotes from the airport. Send e-mail
  from a taxi. Book a flight, get directions and
  read the news virtually anywhere, anytime.
• Wireless

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Features of Palm VII

• AAA bateries
• Data transfer rate at 8kbps
• 2 MB of RAM
• Web clipping
• Palm Query Application (PQA)

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Web Clipping Apps

• Financial
• Bank of America
• Fidelity Investments
• ETrade
• News
• ABCNEWS.com
• ESPN.com
• USATODAY.com
• Reference and Directory
• Merriam-Webster
• US WEST Dex
• Yahoo! People Search
• Travel and Entertainment
• MapQuest.com
• Moviefone.com
• The Weather Channel

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iMessenger

• Receiving messages
• Through your user_at_Palm.net account
• Only first 500 characters are being sent
• Sending messages
• There are 3 ways to compose text to send.

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3 ways to enter data

• Graffiti
• Only display lower case
• Onscreen keyboard
• Both lower and upper case
• Desktop keyboard
• Hotsync technology

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Graffiti Characters
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On screen keyboard
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Area coverage for PDA
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Whats new?

• Unlimited plan
• Download web clipping apps at

http//www.palm.net/apps/
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PDA service plan
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Strengths and weaknesses

• Pros
• Webclipping PQA
• iMessaging
• Cons
• Coverage for wireless services too limited
• Only 2MB of storage space
• Expensive monthly service charges too high

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References

• Shelly, Cashman, and Serwatka. Business Data
  Communications International Thomson Publishing,
  1998.
• Naugle, G Mathew. Local Area Networking
  McGraw-Hill, Inc. New York, 1991.
• FitzGerald, Jerry Dennis, Allen. Business Data
  Communications and Networking. John Wiley
  Sons, Inc. New York, 1999.
• Robinson, Teri. Mobile Computing Micro Times.
  No 203, pg137-39. Feb 8, 2000.
• www.blackbox.com
• www.calstatela.edu/cbtweb/curicula/courses/lant01e
  /lant01e.htm

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References

• www.palm.net
• www.palm.com
• Hudson, I.J. Intranet Access In the Palm of your
  hand TechWeb www.techweb.com August 23, 1999
• The PC technology guide www.pctechguide.com/25mob2
  .htm