Figure 5-1: Local wireless Technologies, Continued ·802.11 Wireless lans oday, mostly speeds of tens of megabits per second with distances of 30 to 100 meters or more Can serve many users in a home or office Increasingly, 100 Mbps to 600 Mbps with 802. 11n Organizations can provide coverage throughout a building or a university campus by installing many access points 5-6
5-6 Figure 5-1: Local Wireless Technologies, Continued • 802.11 Wireless LANs – Today, mostly speeds of tens of megabits per second with distances of 30 to 100 meters or more • Can serve many users in a home or office – Increasingly, 100 Mbps to 600 Mbps with 802.11n – Organizations can provide coverage throughout a building or a university campus by installing many access points
Radio Propagation
Radio Propagation
Figure 5-5: Frequency Measurement Frequency Light waves are measured in wavelengths( Ch 3) Radio waves are measured in terms of frequency Measured in hertz(Hz)-the number of complete cycles per second 1 Second Two cycles in 1 second, so frequency is two Hertz(Hz) 5-8
5-8 Figure 5-5: Frequency Measurement • Frequency – Light waves are measured in wavelengths (Ch. 3) – Radio waves are measured in terms of frequency – Measured in hertz (Hz)—the number of complete cycles per second 1 Second Two cycles in 1 second, so frequency is two Hertz (Hz)
Figure 5-5: Frequency Measurement, Continued Measuring frequencies Frequency measures increases by factors of 1,000(not 1,024) Kilohertz( kHz) [Note the lower-case k MegahertZ(MHz) Gigahertz(GHz) 5-9
5-9 Figure 5-5: Frequency Measurement, Continued • Measuring Frequencies – Frequency measures increases by factors of 1,000 (not 1,024) – Kilohertz (kHz) [Note the lower-case k] – Megahertz (MHz) – Gigahertz (GHz)
Figure 5-6: Omnidirectional and dish Antennas Dish Antenna Om nidirectional Antenna Focuses signals in a narrow range spread signals in all directions Signals can be sent over long distances Rapid signal attenuation Must point at the sender No need to point at receiver Good for fixed subscribers Good for mobile subscribers 5-10
5-10 Figure 5-6: Omnidirectional and Dish Antennas Omnidirectional Antenna Spread signals in all directions Rapid signal attenuation ----- No need to point at receiver Good for mobile subscribers Dish Antenna Focuses signals in a narrow range Signals can be sent over long distances ----- Must point at the sender Good for fixed subscribers