1. 5211 Data Comm 1 Paul Weingartner 7-2004 Presentation #2

2. Cabling & Coax Termination is a very important topic often not covered. When signals are sent down a wire/cable if they are not fully absorbed in the load at the end, they can be reflected back. This reflected signal will collide with other signals coming down the line. The result is garbled data. Which has to be re-transmitted

3. The problem Is called SWR – Standing Wave Ratio People in RF communications know it as VSWR (voltage SWR) and use RF devices to match the impedance

4. The fix Many devices have the appropriate termination (resistors) included in them. Other times a “terminator” must be installed. Terminators are also in unused Rambus memory slots, some mother board expansion busses, etc.

5. Fiber optic cable Laser light emitters generate light at a very narrow wave length White light has all colors (wavelengths in it) – play with a prism Secure communications Impervious to noise (RF)

6. Fiber modulation techniques Single mode (wave length) Wave division multiplexing (WDM) Dense WDM (DWDM)

7. Wireless comm Simply put, speed is bandwidth To send high speed data, you need wide channels to transmit the data. This effectively means VHF and above 800 MHz is the lower limit of what is considered “microwave”

8. Point to point links Bell telephone has used microwave links for many years. Referred to as “Terrestrial” links

9. Satellite comm There are two popular flavors that are being used –For home/small biz users, “Direct PC” is an option –For businesses, VSAT (Very Small Aperature Terminal Sat equipment) Issues

10. Cellular phones Analog Digital

11. Analog cell Who cares!

12. Digital cell – mod types TDMA CDMA GSM

13. Cell – data speeds Analog – 14,400 b/s (good day) Digital – 1 st gen – 14.4k Dig – 3 rd gen – 144k –What is the real throughput??? Future – 1Mb/s

14. Wi-fi – Wireless computer access There are a series of standards –802.11a 54Mb –802.11b Wi-fi 11Mb –802.11g 54Mb –802.11i (find out) –802.16 – Wi-Max Range – up to 1000’ with standard antennas (2+ miles with beams)

15. Bluetooth Short range – up to 30 ft 2.45 GHz How fast?

16. MODEM – Chap 4 The only way to send data over any distance is to use some type of modulation technique Audio – Acoustic can be used with telephones Signals are often converted to different levels (voltages/currents) in order to send them over long distances)

17. Devices Analog modems Cable modems CSU/DSU FRAD ISDN