1. Agenda Last class: Network Protocols Today: Wireless Technology –How do computers talk to each other… with no wire connecting them?

2. Wireless Technology Examples you already know:

4. Wireless Technology Uses radio waves, infrared, microwaves to send signals (0 and 1’s)

5. Wireless Technology Issues Range – short vs long Line of sight – walls? –Why does the car radio not work in a tunnel? –Why do people go outside to talk on cell phone? One-way or two-way –Talk & listen? –Download & Upload?

6. Radio A radio station is a big antenna that sends out radio waves Wavelength ~10 m Frequency ~ 100 MHz Radio channels! –AM 1320 or 101.3 FM

7. Radio Short range – only in one city One way: only receives signals from one radio station (only 1 frequency) Mobile – can move anywhere

8. Cell Phones The city is divided into CELLS Each cell has a station within line of sight The stations talk to each other and also to your cell phone (by using radio waves) If you move to another cell, the stations know this.

9. Cell Phones So when you call your friend –You send a signal to the nearest station –The station talks to other stations to find your friend. If your friend’s cell phone is on, it will find it. –When you talk, your voice is DIGITIZED and sent as radio waves from station to station to your friend’s phone. –At your friend’s phone, the radio waves are Reconstructed into voice. All this happens in seconds!

10. 0110000101011100101… DIGITIZATION RECONSTRUCTION How Cell Phones Work:

11. WIFI WIFI = Wireless Fidelity Wireless Networks –Laptop computer to printer –IPhone to internet in the city –Need a Wireless Access Point (WAP) nearby (usually a router)

12. Questions?

13. Almost Finished What you WANT to learn –How to make your computer faster? –How to fix your computer?

14. How to make computer faster? Run the Disk Cleaner –Delete files that you don’t use or don’t need –Free up space Run the Disk Defragmenter –Put blocks of memory together –Computer only needs to search one place for files

15. How to fix your computer? Find the problem –Hardware? Test it with other hardware –Software? Re-install, download updates –Virus? uh oh, re-install operating system or load a back-up Double check and try again BING the problem, search for a solution Call for help