gmu it 212 - spring 20071 wireless lan, cell phones, bluetooth final review it 212 002 how computers...

GMU IT 212 - Spring 2007 1

Wireless LAN, Cell Phones, Bluetooth

Final Review

IT 212 002How Computers Work

May 3, 2007


Lecture Agenda Chapter 26: How Wireless Sets PCs Free Final Exam Review


Chapter 26: How Wireless Sets PCs Free


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)


Current Flavors of Wi-FiStandard 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)


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


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


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


Securing your WLAN Access Point The following measures can all be broken, but offer

a certain measure of security

1. Disable broadcast of SSID Node must ask “Is Bob there?” to get a response Normally asks “Is anyone there?”

2. Apply MAC filtering Limit which MAC addresses can access your network

3. Apply encryption with WEP (wired equivalent privacy)

Use highest number of bits (128 bits) Encrypts data traveling between station and access point


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


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

MTSOMobile Telephone Switching Office

PSTNPublic Switched

Telephone Network


Cell Phone Operation

Base stationMobile user

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


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


FDMA vs TDMA vs CDMA

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

www.owlnet.rice.edu/~elec301/Projects01/cdma/compare.html


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


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


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


Final Exam Review


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!!!


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


Review of lecture topics


Goals of the course Upon the successful completion of this course,

the student will be able to: Describe the basic components of today’s personal

computer and how they function together Understand some of the historical developments that

have resulted in today’s personal computers Understand the basic operation and function of

today’s personal computer Understand what the Internet is and some of the

historical developments that resulted in its creation


Jan 25—Introduction & 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.


Four Functions of a ComputerA computer has four functions:

a. accepts data Input

The Information Processing

Cycle

b. processes data ProcessingProcessing c. produces output Output d. stores results Storage

ProcessorInput Output

Storage


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


Feb 1—Hardware, 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 Serial Port Modem


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


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 drive’s boot sector for OS to take control

Continues until Windows logon screen


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.

EIDE—hard disk driver Hardware interrupts How Plug and Play Works


Feb 8—Semiconductors, Transistors, RAM, Microprocessors

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

Video Card

Hard Drive


Plug and Play RulesDevices 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.


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


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 (carry:1)

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


Feb 15—Programming 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


Memory Map of Segment 0


Mar 1, Mar 22—Long 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


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


Mar 29—Kernels 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.


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


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.


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


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


Apr 19—LAN, 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


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)


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)


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 provider’s 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


The Internet History of the Internet An interconnected system of networks that

connects computers around the world via the TCP/IP protocol

Interconnected networks


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


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


Protocol layers and Encapsulation

ApplicationLayer

TransportLayer

InternetLayer

Data LinkLayer

PhysicalLayer

Layer 1

Layer 2

Layer 3

Layer 4

Layer 5Allows applications to work together-Example: HTTP, FTP

Ensures reliable transmission, error control-Example: Transmission Control Protocol (TCP)

Moves data between networks using routers using an addressExample: Internet Protocol (IP) uses IP address

Moves data within a network using switches using an address-Example: Ethernet (Data Link Layer) uses MAC address

Physical connection between machines includingelectrical signaling and wiringExample: Ethernet (Physical Layer)


Following an IP packet

ApplicationLayer

TransportLayer

InternetLayer

Data LinkLayer

PhysicalLayer

InternetLayer

Data LinkLayer

PhysicalLayer

InternetLayer

Data LinkLayer

PhysicalLayer

InternetLayer

Data LinkLayer

PhysicalLayer

InternetLayer

Data LinkLayer

PhysicalLayer

InternetLayer

Data LinkLayer

PhysicalLayer

InternetLayer

Data LinkLayer

PhysicalLayer

ApplicationLayer

TransportLayer

InternetLayer

Data LinkLayer

PhysicalLayer

You inVirginia

ServerIn Australia

You inVirginia

Router 1

Router 2

Router 3

Router 4

Router 5

ServerIn Australia

Router 1 Router 2 Router 3 Router 4 Router 5

Router 6

Router 6

-Routers do not alter IP datagrams-Network interface layer headersand footer change from router to router


Apr 26—Displays, 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


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


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


Multimedia Sound card

MIDI—only instructions on how to play the audio file is stored, not the audio recordings themselves

MP3—two 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

gmu it 212 - spring 20071 wireless lan, cell phones, bluetooth final review it 212 002 how computers...

Documents

wireless network adapter

router wireless router

wireless access pointsrouters

network slide

access point slide

wireless sets pcs free

b slide

wlan access