Wireless LAN, Cell Phones, Bluetooth

1
IT 212 002How Computers WorkMay 3, 2007

• Wireless LAN, Cell Phones, Bluetooth
• Final Review

2
Lecture Agenda

• Chapter 26 How Wireless Sets PCs Free
• Final Exam Review

3
Chapter 26 How Wireless Sets PCs Free
4
Wireless LAN

• A wireless local area network (WLAN) is a LAN
  that does not use wires as a connection medium
• Ethernet example of LAN
• Wi-fi, also known as IEEE 802.11, is an example
  of a WLAN
• There are many versions of the IEEE 802.11
  standard including
• 802.11b
• 802.11a
• 802.11g
• 802.11n (coming soon)

5
Current Flavors of Wi-Fi
Standard 802.11b 802.11a 802.11g
Speed 11Mbps 54Mbps 54Mbps
Speed 100-150 feet 25-75 feet 100-150 feet
Frequency 2.4GHz 5GHz 2.4GHz
Acceptance High Low High (compatible with 802.11b)
6
Wireless Access Points/Routers

• For home use, typically have a wireless router or
  wireless access point (AP)
• Wireless router Wireless access point plus a
  router
• Wireless router allows you to share one DSL/cable
  modem connection among several wireless computers
• Wireless access point needs a separate router to
  share broadband connection
• Wireless router connects directly to DSL/cable
  modem via Ethernet cable
• Also possesses a switch (4-port) which allow you
  to connect wired desktop computers to the network

7
Wireless Stations

• Wireless nodes on the network are called stations
• Laptops, PDAs, printers, digital cameras, etc.
• A wireless network adapter is used to connect to
  the wireless LAN
• PC card adapter
• USB adapter
• PCI adapter (desktops)
• Built-in adapter
• Has unique MAC address

8
Wireless Protocol

• Wireless station broadcasts probe request
• Discovers which 802.11 APs in range
• If an AP is within that range, the AP picks up
  the probe request and broadcasts an
  acknowledgement including its service set
  identifier (SSID)
• The two stations go through a process that
  involves authentication
• The AP and the station send packets to each other
  using specific addresses
• Extension points may be used to extend the
  coverage of a wireless network
• Point-to-point (computer-to-computer) networks
  are also possible for Wi-fi

9
Securing your WLAN Access Point

• The following measures can all be broken, but
  offer a certain measure of security
• Disable broadcast of SSID
• Node must ask Is Bob there? to get a response
• Normally asks Is anyone there?
• Apply MAC filtering
• Limit which MAC addresses can access your network
• Apply encryption with WEP (wired equivalent
  privacy)
• Use highest number of bits (128 bits)
• Encrypts data traveling between station and
  access point

10
Cell Phones

• -1983 Motorola DynaTEC Cell phone
• -Around 38 ounces (1.75 pounds)
• -10 inches tall

• -2007 Motorola Razr
• -Around 3.3 ounces
• -3.8 inches tall

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Cell Phone Operation

• Base station covers a certain area called a cell
• Each base station connected to a switching center
  called the Mobile Terminal Switching Office
  (MTSO)
• MTSO connected to public switched telephone
  network
• When a mobile user turns the cell phone on, the
  cell phone communicates with the base station
  over a channel called the control channel
• The cell phone listens to the System
  Identification Code (SIC) that is broadcast over
  the control channel
• The SIC gives the cell phone information
  regarding the base station
• The cell phone also sends a registration request
  over the control channel which is passed over to
  the MTSO
• The MTSO contains subscriber info
• The MTSO is also responsible for billing the user
• Has the ability to assign which frequencies the
  mobile units may use to communicate with the base
  station

12
Cell Phone Operation

• Neighboring base stations use different
  communication frequencies to avoid garbled
  communications
• As phone moves from one cell to another
• Signal grows weaker
• Neighboring station monitors strength on other
  frequencies, not only its own
• When next station signal is stronger than current
  station, stations coordinate to transfer call on
  new frequency
• Called a handoff

13
Analog versus Digital

• Most cell phones today are digital but earlier
  ones were analog
• Analog send analog signals to base station using
  carrier radio waves
• Digital cell phone digitize audio signals using
  ADC circuits and radio wave carriers to send
  information to base station
• Analog phones higher power than digital

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FDMA vs TDMA vs CDMA
www.owlnet.rice.edu/elec301/Projects01/cdma/compa
re.html

• Multiple access method to share a resource over
  many users
• FDMA frequency division multiple access
• Users are separated in frequency i.e. mobile
  phones communicate at different frequencies than
  the others within each cell.
• Analog phones
• TDMA time division multiple access
• User are separate in time slots, can only
  communicate in allotted time slot
• Used by GSM (Global System for Mobile
  Communication) phones
• US Carriers Cingular, T-Mobile
• CDMA code division multiple access
• Users simultaneously use all frequencies and time
  slots available, assigned codes which do not
  interfere with one another
• US Carriers Verizon, Sprint

15
GSM versus CDMA

• Most of the world uses GSM
• SIM (subscriber identity module) card contains
  user account information, address book, etc.
• To use phone overseas
• Phone must be unlocked (i.e. can use any SIM
  card)
• Make sure frequencies compatible quad-band phone
• US 850 MHz,1900 MHz
• Europe 900 MHz, 1800 MHz
• Next generation, moving to 3G (currently 2G or
  2.5G) data services
• Three competitors, all based on CDMA
• CDMA2000 based on 2G CDMA
• WCDMA Wide-band CDMA new European standard
• TD-SCDMA Time-division Synchronous Code-Division
  Multiple Access, in China
• 3G networks have potential transfer speeds of up
  to 3 Mbps

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Bluetooth

• Bluetooth is a standard protocol for connecting
  wireless devices to each other located within a
  close vicinity
• Harald Bluetooth is a Danish king who unified
  Scandinavia
• Bluetooth devices comprise a radio module that
  incorporates the Bluetooth protocol
• The range is limited to about 30 feet and data
  rate to a maximum of around 1Mbps
• The link manager is a piece of software in the
  Bluetooth device to set up communications with
  other devices and to send/receive signals to/from
  them
• Bluetooth devices may operate in a variety of
  modes including
• Standby, Page, Inquiry, Park and Hold
• Bluetooth security issues

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Bluetooth

• Uses Frequency Hopping Spread Spectrum
• Radio transmissions between devices hop between
  79 different frequencies
• Change frequencies 1,600 times per second
• Hopping done to minimize interference
• Transmit at 1 mW
• Killer app Bluetooth headsets

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Final Exam Review
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Final Exam

• Open book, open notes
• True/false, multiple choice, short answer
• Students required to bring scantron form 882-E
  and a number 2 pencil!!!

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Chapters from book to review

• How Computers Works, 8th Edition
• This semester we covered
• Chapters 1-19
• Chapters 21-22
• Chapters 24-27
• You are responsible for textbook material for
  topics covered in class

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Review of lecture topics
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Goals of the course

• Upon the successful completion of this course,
  the student will be able to
• Describe the basic components of todays personal
  computer and how they function together
• Understand some of the historical developments
  that have resulted in todays personal computers
• Understand the basic operation and function of
  todays personal computer
• Understand what the Internet is and some of the
  historical developments that resulted in its
  creation

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Jan 25Introduction Syllabus, History

• Define computer
• A programmable machine that inputs, processes and
  outputs data.
• Any device capable of processing information to
  produce a desired result. No matter how large or
  small they are, computers typically perform their
  work in three well-defined steps (1) accepting
  input, (2) processing the input according to
  predefined rules (programs), and (3) producing
  output.
• In general, a device that uses digital technology
  to process and manipulate information.
• An electronic device that stores, retrieves, and
  processes data, and can be programmed with
  instructions. A computer is composed of hardware
  and software, and can exist in a variety of sizes
  and configurations. 

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Four Functions of a Computer
A computer has four functions
a. accepts data Input                                   The Information Processing Cycle
b. processes data Processing                                   The Information Processing Cycle
c. produces output Output                                   The Information Processing Cycle
d. stores results Storage                                   The Information Processing Cycle

Storage
Input
Processor
Output
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History of computers

• In 1837, Charles Babbage designed a fully
  programmable mechanical computer that he called
  "The Analytical Engine".
• Large-scale automated data processing of punched
  cards was performed for the US Census in 1890
• A succession of steadily more powerful and
  flexible computing devices were constructed in
  the 1930s and 1940s, adding key features seen in
  modern computers.
• The use of digital electronics (largely invented
  by Claude Shannon in 1937), more flexible
  programmability were vitally important steps
• The US Army's Ballistics Research Laboratory
  ENIAC (1946)
• EDSAC first computer to implement the stored
  program (von Neumann) architecture (1952).
• Vacuum tube-based computers were in use
  throughout the 1950s,
• Replaced in the 1960s by transistor-based devices
• Smaller, faster, cheaper, less power and more
  reliable
• By the 1970s, integrated circuit technology
• Creation of microprocessors such as the Intel
  4004
• By the 1980s, computers became sufficiently small
  and cheap to replace simple mechanical controls
  in domestic appliances
• Computers became widely accessible for personal
  use by individuals
• Home computers and personal computers.
• Widespread growth of the Internet since the 1990s

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Feb 1Hardware, Wake-up Process, Boot-Up,
Operating Systems

• Inside a PC case
• Motherboard (see textbook for contents)
• Power supply
• Hard Disk Drive
• Media Drives CD ROM, DVD ROM, Tape, USB Flash,
  Floppy
• IDE Controller disk drives
• AGP, PCI-E
• Video Card
• Sound Card
• RAM
• Clock
• BIOS
• Microprocessor (CPU)
• Heat Sink and Fan
• Buses
• USB
• Keyboard
• Network Controller
• Parallel Port

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Operating Systems

• An operating system (OS) is a computer program
  that manages the hardware and software resources
  of a computer. Performs basic tasks such as
• controlling and allocating memory
• prioritizing system requests
• controlling input and output devices
• facilitating networking
• managing files
• May provide a graphical user interface for higher
  level functions
• It forms a platform for other software
• Discussed Windows, Mac, Unix/Linux

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How a PC Wakes Up 2 steps

• Power-On Self Test (textbook pp. 24-25)
• From turn on of power switch to transferring
  control from BIOS to operating system (OS) on
  hard disk
• Disk Boot (textbook pp. 26-27)
• After POST, processor executes program contained
  on hard drives boot sector for OS to take
  control
• Continues until Windows logon screen

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Hardware and Software Work Together

• The operating system quickly evolved into an
  all-encompassing bridge between your PC and the
  software you run on it
• Device driver
• A device driver is a specific type of computer
  software, typically developed to allow
  interaction with hardware devices.
• EIDEhard disk driver
• Hardware interrupts
• How Plug and Play Works

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Feb 8Semiconductors, Transistors, RAM,
Microprocessors
Video Card

• North Bridge
• Memory (RAM)
• CPU
• Video Card
• Frontside Bus (FSB) fast between RAM and CPU
• Backside Bus, not shown, connects CPU to L2 cache
• South Bridge connects other I/O such as disk
  drives, sound cards, Ethernet, etc.

CPU
Hard Drive
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Plug and Play Rules
Devices on These Buses or Connectors Can Be Added to or Removed from a Running System? System Must be Turned Off Before Device is Added to or Removed from System?
USB, IEEE 1394, PC Card devices, CardBus devices Yes. Remove hardware by using the Safely Remove Hardware application if it appears in the notification area. No.
PCI, ISA, EISA No. Yes.
Docking station Varies among computer manufacturers most support docking and undocking while the computer is running. Varies among computer manufacturers most support docking and undocking while the computer is running.
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Windows Registry

• Every operating system and application needs a
  place to store configuration settings and user
  preferences
• MS-DOS uses CONFIG.SYS
• DOS programs made own arrangements for user
  settings
• Windows originally used INI files
• Read and written using special routines
• Windows had one configuration file, SYSTEM.INI,
  used for all the internal settings
• Plus another, WIN.INI, for user preferences
• Each application had an INI file
• INI files were slow to access and limited to 64Kb
• Unsuited for the 32-bit versions of Windows
• So for Windows NT and Windows 95 Microsoft
  introduced the Registry
• A database for storing and accessing
  configuration data
• Organized for fast and efficient access
• Data is stored in a hierarchical manner like the
  folders on a hard disk
• Registry data that is currently in use is cached
  to provide better performance

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Binary Arithmetic, Transistors

• The simplest arithmetic operation in binary is
  addition. Adding two single-digit binary numbers
  is relatively simple
• 0 0 0
• 0 1 1
• 1 0 1
• 1 1 10 (carry1)
• Multiple bits
• 1 1 1 1 1 (carry)
• 0 1 1 0 1
• 1 0 1 1 1
• -------------
• 1 0 0 1 0 0
• A transistor is the basis of integrated circuits,
  works as a switch

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Feb 15Programming Languages, How Windows Works,
How Applications Work

• PC computer memory is divided into segments,
• 64 kilobytes each (65,536 bytes, to be exact)
• Segment register in microprocessor indicates
  segment is to be accessed
• Segment 0
• Contains memory pointers, device drivers,
  buffers, input/output ports, and other essential
  information required by the computer and its
  operating system
• Segment 0 contains 65,536 memory addresses

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Memory Map of Segment 0
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Mar 1, Mar 22Long Term Memory, Disk Drives,
Optical Storage

• Volatile vs Non-Volatile memory
• Volatile memory does not retain its information
  without constant power
• Non-Volatile maintains information indefinitely
• Magnetic Storage/Hard drives
• Chapters 9-11 in textbook
• Optical drives
• Chapter 12 in textbook

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Magnetic Storage

• Media used in removable magnetic-storage devices
  is coated with iron oxide
• A ferromagnetic material
• If you expose it to a magnetic field it is
  permanently magnetized
• The media is typically called a disk or a
  cartridge
• The drive uses a motor to rotate the media at a
  high speed
• Accesses (reads) the stored information using
  small devices called heads
• Each head has a tiny electromagnet (an iron core
  wrapped with wire)
• The electromagnet applies a magnetic flux to the
  oxide on the media
• The oxide permanently "remembers" the flux last
  saw
• During writing, data signal sent through a coil
  to create a magnetic field
• At the gap, the magnetic flux forms a fringe
  pattern
• The flux magnetizes the oxide on the media
• During reading, the read head pulls a varying
  magnetic field across the gap
• Creates a varying magnetic field in the core and
  a signal in the coil

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Mar 29Kernels and Routines,Bandwidth, UPS,
Ports, SATA, USB

• DLL Dynamic-Link Library
• A library of executable functions or data that
  can be used by a Windows application
• A DLL provides one or more functions
• A program accesses the functions by creating a
  static or a dynamic link to the DLL
• A static link remains constant during program
  execution
• A dynamic link is created by the program as
  needed
• A DLL can be used by several applications at the
  same time
• Some DLLs are provided with the Windows operating
  system and available for any Windows application
• Other DLLs are written for a particular
  application and are loaded with the application
• DLL is Microsoft's implementation of the shared
  library concept in the Microsoft Windows and OS/2
  operating systems
• Usually have the file extension DLL, OCX (for
  libraries containing ActiveX controls), or DRV
  (for legacy system drivers)
• DLL file formats are the same as for Windows EXE
  files
• DLLs can contain code, data, and resources, in
  any combination.

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Application Program Interface (API)

• A set of routines, protocols, and tools for
  building software applications
• A good API makes it easier to develop a program
  by providing all the building blocks
• A programmer puts the blocks together
• Most operating environments, such as MS-Windows,
  provide an API
• Programmers can write applications consistent
  with the operating environment
• Guarantee that all programs using a common API
  will have similar interfaces

40
Registry

• A database used by the Windows operating system
  to store configuration information
• The Registry consists of the following major
  sections
• Roots - file associations and OLE information
  (Object Linking and Embedding)
• Users Preferences - all preferences set for
  current user
• User Information - all the current user
  information for each user of the system
• Local Machine Settings - settings for hardware,
  operating system, and installed applications
• Current Configuration - settings for the display
  and printers and other devices
• Dynamic Data - performance data
• Most Windows applications write data to the
  Registry
• You can edit the Registry directly by using the
  Registry Editor
• regedit.exe provided with the operating system
• Errors in the Registry could disable your
  computer.

41
Bandwidth, UPS

• Analog to digital converters
• Digital to analog converters
• Uninterruptable Power Supplies
• Voltage surges and spikes - Times when the
  voltage on the line is greater than it should be
• Voltage sags - Times when the voltage on the line
  is less than it should be
• Total power failure - Times when a line goes down
  or a fuse blows somewhere on the grid or in the
  building
• Frequency differences - Times when the power is
  oscillating at something other than 60 Hertz

42
Ports

• A port serves as an interface between the
  computer and other computers or devices
• Physically, a port is a specialized outlet to
  which a plug or cable connects
• Serial
• Parallel
• SATA
• USB

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Apr 19LAN, Internet, TCP/IP, DSL, Cable Modems

• Local area network (LAN)
• A network which connects computers together in a
  small geographic region (office, home, etc.)
• Designed to share resources on a network
• Example sharing a printer at home
• Can be wired or wireless
• Topology bus, ring, or star
• Network model client/server or peer-to-peer
• Physical components NIC card, wiring

44
Ethernet

• Ethernet is the most common LAN today
• Ethernet operates on the physical layer (layer 1)
  and data link layer (layer 2)
• Most common installations of Ethernet (home,
  office) use
• CAT5/6 twisted pair cable
• RJ-45 connectors
• Communicate via Ethernet packets
• NIC card has MAC address
• 48 bit, represented in Hex 02608CBBDCA7
• IEEE assigns unique address
• Permanently attached
• This is a layer 2 address
• Ethernet Packet
• Protocol called Carrier Sense Multiple Access
  with Collision Detection (CSMA/CD)

45
Hub vs. Switch vs. Router

• Hub
• Broadcasts what it receives on one port to all
  ports within a single network
• Dumb device
• Physical layer device (layer 1)
• Switch
• A smart hub performs same function of a hub,
  just does the job better
• A switch reads the MAC address of the packet and
  transmits the packet to the port that leads to
  the node it is addressed to (or can broadcast
  also)
• Data Link layer device (layer 2)
• Router
• Connects different networks (i.e. different LANs
  together) by reading IP address
• Often, when you buy a router it includes a switch
• Internet layer device (layer 3)

46
Connecting to the Internet

• Modems
• Most recent type of modems are 56K, or V.90 that
  are able to carry data at a maximum data rate of
  56Kbps
• Digital Subscriber Line (DSL) or xDSL is a
  technology for sending high speed digital data
  across analog telephone lines
• Unlike regular dial-up modems, you do not need to
  dial up, the connection is always on
• Also, the phone lines is not held up when
  connected unlike a modem ? voice and DSL data
  occupy different frequency bands
• The Ethernet NIC in your computer interfaces to a
  DSL modem
• Cable Modems Data is carried over fiber optic
  cables from the cable provider to the providers
  distribution hub and then over standard coaxial
  cable from the hub to your cable modem
• Both TV signals as well as computer data are
  carried over the same cable
• A coupler/splitter routes TV data to TV set and
  computer data to the cable modem

47
The Internet

• History of the Internet
• An interconnected system of networks that
  connects computers around the world via the
  TCP/IP protocol
• Interconnected networks

48
Circuit Switching

• Public switched telephone network (PSTN) uses
  circuit switching
• Dedicated resources are allocated along the
  network for that particular call
• No one else can use those resources, even if
  communication is inactive

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Packing Switching

• Internet uses packet switching
• No dedicated resources allocated
• Sender breaks data into packets
• Packets sent across network, may go different
  routes
• Receiver reassembles packets
• Simultaneously, many other senders and receivers
  using the same resources

http//williamstallings.com/DCC/DCC7e.html
50
Protocol layers and Encapsulation
Application Layer
Allows applications to work together -Example
HTTP, FTP
Layer 5
Transport Layer
Ensures reliable transmission, error
control -Example Transmission Control Protocol
(TCP)
Layer 4
Internet Layer
Moves data between networks using routers using
an address Example Internet Protocol (IP) uses
IP address
Layer 3
Data Link Layer
Moves data within a network using switches using
an address -Example Ethernet (Data Link Layer)
uses MAC address
Layer 2
Physical Layer
Physical connection between machines
including electrical signaling and
wiring Example Ethernet (Physical Layer)
Layer 1
51
Following an IP packet
Router 2
Router 4
You in Virginia
Router 1
Router 6
Server In Australia
Router 3
Router 5
-Routers do not alter IP datagrams -Network
interface layer headers and footer change from
router to router
You in Virginia
Server In Australia
Router 1
Router 2
Router 3
Router 4
Router 5
Router 6
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Apr 26Displays, I/O, Portable Computers,
Multimedia

• CRT vs LCD vs Plasma
• CRT uses electron gun which hits phosphor-coated
  screen
• LCD uses liquid crystals which twist light
  depending on electric field light passes through
  polarizing filters
• Plasma uses gas which emit photons excited by
  electric field photons hit phosphors to produce
  colors
• DLP uses a spinning wheel with micro-mirrors for
  projection

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Input/Output Devices

• Keyboard
• Scan codes
• Mouse
• Mechanical Mouse
• Optical Mouse
• Touchpad
• Pointing Stick
• Speech recognition
• Enrollment of phonemes
• Two steps acoustic recognizer, then natural
  language component
• Scanners
• Use CCDs
• OCR character recognition software

54
Notebook PCs

• Objectives
• Minimize size, weight, power consumption for
  portability
• Constraints viewing area, keyboard, mouse, power
  capacity
• Realities
• Typically 2x cost of comparable PC
• lags desktop capabilities
• Upgrading is difficult, if not impossible
• economically practical?
• Heat Dissipation Is a Problem
• Battery heats up during use
• Fan cools electronic components
• Components switched off or clock speed lowered to
  reduce power consumption
• PC Cards expandability, upgradeability
• PDAs input interface issues

55
Multimedia

• Sound card
• MIDIonly instructions on how to play the audio
  file is stored, not the audio recordings
  themselves
• MP3two steps to reduce file size perceptual
  coding then lossless compression
• Video card
• AVI format interweave video and audio
• DVDs in MPEG format
• Intraframe complete data image for that frame
• Predicted frame the difference between current
  frame and last predicted frame or intraframe
• Bidirectional frame using data from closest
  frames, interpolates to get frame