Welcome to CMPE003 Personal Computer Concepts: Hardware and Software

1. Welcome to CMPE003 Personal Computer Concepts: Hardware and Software Winter 2003 UC Santa Cruz Instructor: Guy Cox

2. Class Information • Midterm #2 • Monday – February 24, 2002. • ID required. • Covers Chapters 5, 7, 9, 10 and 12. • Book reading plus lectures. • Multiple choice • Requires Scantron #F-1712-ERI-L (pink) • ~50 questions • No make-ups after the fact

3. Assignments • Assignment #5 – Due February 28, 2003 • Programming • Edit a Java Script program file • If you want more information about javascript, • visit http://www.htmlgoodies.com. http://www.soe.ucsc.edu/classes/cmpe003/Winter03/hw5_javascript.html

4. Networking: Computer Connections Chapter 7 Part A

5. Objectives • Describe the basic components of a network • Explain the methods of data transmission, including types of signals, modulation, and choices among transmission modes • Differentiate among the various kinds of communications links and appreciate the need for protocols • Describe various network configurations • List the components, types, and protocols of a local area network • Appreciate the complexity of networking • Describe some examples of networking

6. Data Communications Send and receive information over communications lines

7. Centralized Data Processing • All processing, hardware, software in one central location • Inefficient • Inconvenient

8. Distributed Data Processing • Computers at a distance from central computer • Can do some processing on their own • Can access the central computer

9. Networking • Uses communication equipment to connect two or more computers and their resources • Can be PC based • Allows connected users to share data and resources • LAN – Local Area Network • shares among users in close proximity • WAN – Wide Area Network • shares among users who are geographically distant

10. Basic Components Sending device Communications link Receiving device

11. Network Design • Transmission speed (ie, data rate) • Medium (wired, wireless….) • Topology – Physical layout of components • Protocol – Rules governing communication • Distance • LAN • MAN • WAN • Technology • Peer-to-peer • File server • Client/server

12. Data Transmission • Digital lines • Sends data as distinct pulses • Need digital line • Analog lines • Sends a continuous electrical signal in the form of a wave • Conversion from digital to analog needed • Telephone lines, coaxial cables, microwave circuits

13. Signals on Wires • An electrical signal reflects from the end of a metal wire the same way that light reflects from a mirror. • Signals: • Lose strength as they pass across the wire. • Emit electromagnetic radiation that interferes with nearby wires.

14. Modulation • Modulation means imposing information on an electrical signal (called the carrier) Amplitude Modulation Frequency Modulation Phase Modulation

15. Analog Transmission Alter the carrier wave • Amplitude Modulation (AM)– • height of the wave is increased to represent 1 • Frequency Modulation (FM)– • number of times wave repeats during a specific time interval can be increased to represent a 1

16. Dialup Modem • MODEM -- Mo(dulator)/Dem(odulator) • Modulate • Convert from digital to analog • Demodulate • Convert from analog to digital • Speeds up to 56,000 bps (56K)

17. Modem Transmission process • Modulation – Computer digital signals converted to analog • Sent over analog phone line • Demodulation – Analog signal converted back to digital

18. Modems • Modems … • Allows two-way communication • Designed to either use two different signals or • Agree to take turns sending data • In either case, data appears to flow simultaneously in both directions. • Dial-up modems • Can dial the phone line and set up call • Talk only to other modems • Newer modems can talk to older slower modems

19. Types of Modems • Direct-connect • External • Internal • PCMCIA • Personal Computer Memory Card International Association • Notebook and laptop computers

20. (A)DSL(Asymmetric) Digital Subscriber Line • Uses conventional telephone lines • Uses multiple frequencies to simulate many modems transmitting at once • No industry standard • Equipment • Speed • Phone line shared between computer and voice

21. Cable Modem • Coaxial cables • Does not interfere with cable TV reception • Up to 10 million bits per second (mbps) • Always on • Shared capacity with neighbors • Security problem • Sniffing the the wire is easy…

22. Cellular Modems • Uses cellular telephone system • Slow speed (9600 bps)

23. ISDN: Integrated Services Digital Network • Digital transmission • Speeds of 128 kbps • Connect and talk at same time • Need • Adapter • Upgraded phone service • Initial costs high • Ongoing monthly fees may be high • Not available in all areas • Old technology -- almost dead… • OBE – like DSL

24. Transmission: Asynchronous and Synchronous Sending and receiving devices must work together to communicate

25. Asynchronous Transmission • Start/stop transmission • Start signal • Group – generally one character • Stop signal • Low-speed communications

26. Synchronous Transmission • Blocks of data transmitted at a time • Send bit pattern • Align internal clock of sending / receiving devices • Send data • Send error-check bits • More complex • More expensive • Faster transmission

27. Transmission Types • Identifies direction of data flow • Simplex • One direction • Television broadcasting • Arrival/departure screens at airport • Half-duplex • Either direction, but one way at a time • CB radio • Message sent, confirmation received • Full-duplex • Both directions at once • Telephone conversation

28. Communications Media • Physical means of transmission • Bandwidth • Range of frequencies that the medium can carry • Measure of capacity

29. Network Cable • Twisted pair • Coaxial cable • Fiber optic cable • Wireless • Uses infrared or low-power radio wave transmissions • No cables • Easy to set up and reconfigure • Slower transmission rates • Small distance between nodes

30. Twisted Pair: Wire Pair • Inexpensive • Susceptible to electrical interference (noise) • Telephone systems • Physical characteristics • Requires two conductors • Twisted around each other to reduce electrical interference • Plastic sheath • Shielded twisted pair • Metallic protective sheath • Reduces noise • Increases speed

31. Coaxial Cable • Higher bandwidth • Less susceptible to noise • Used in cable systems • Physical characteristics • Center conductor wire • Surrounded by a layer of insulation • Surrounded by a braided outer conductor • Encased in a protective sheath

32. Fiber Optics • Transmits using light • Higher bandwidth • Less expensive • Immune to electrical noise • More secure – easy to notice an attempt to intercept signal • Physical characterizes • Glass or plastic fibers • Very thin (thinner than human hair) • Material is light

33. Microwave Transmission • Line-of-site • High speed • Cost effective • Easy to implement • Weather can cause interference • Physical characteristics • Data signals sent through atmosphere • Signals cannot bend of follow curvature of earth • Relay stations required

34. Satellite Transmission • Microwave transmission with a satellite acting as a relay • Long distance • Incurs longer delay -- ~2.5 secs rtt • Components • Earth stations – send and receive signals • Transponder – satellite • Receives signal from earth station (uplink) • Amplifies signal • Changes the frequency • Retransmits the data to a receiving earth station (downlink)

35. Satellite Transmission

36. Mixed & Matched…. Example – East and West coast: • Request made • Twisted pair in the phone lines on the East Coast • Microwave and satellite transmission across the country • Twisted pair in the phone lines on the West coast • Data transferred • Twisted pair in the phone lines on the West Coast • Microwave and satellite transmission across the country • Twisted pair in the phone lines on the East coast

37. Have a nice day