NETWORKING WIRELESS MEDIA

COMMON NETWORK CABLESThe connection between the source and destination may either be direct or indirect, and may span multiple media types.

• Copper Media

• Optical Media

• Wireless Media

WIRELESS FREQUENCYWireless APs operate at:

• 2.4 GHz• 5 GHz

2 GHZ! That’s the same as my microwave oven, isn’t that dangerous?

Answer: No.

• Electromagnetic waves happen naturally.• Light is an electromagnetic wave

• It is not the frequency, but the wattage, the power.• Any electromagnetic wave can be dangerous with too much power.• A 25 watt light bulb is safe, but it wouldn’t be safe at 250,000 watts

• Wireless access points generate signals at 1/10th of a watt.• Like all electromagnetic waves, the signal does not fade in a linear

manner, but inversely as the square of the distance.

Rick Graziani graziani@cabrillo.edu 4

INVERSE SQUARE LAW

Double the distance of the wireless link, we receive only ¼ of the original power.

Triple the distance of the wireless link, we receive only 1/9 the original power.

Move 5 times the distance, signal decreases by 1/25.

Point A

2 times the distance ¼ the power of Point A

10 20 30 40 50 100

3 times the distance 1/9 the power of Point A

5 times the distance 1/25 the power of Point A

10 times the distance 1/100 the power of A

PUTTING IT IN SOME PERSPECTIVEMeasurements from an antenna transmitting 100mW at 1 inch

Remember a milliwatt is 1/1,000th of a Watt

Microwave oven typically operates at 1,000 watts in a confined space.

1” 100 mW 1/10th watt

2” 25 mW 1/40th watt

4” 6.25 mW 1/166th watt

8” 1.56 mW 1/1000th watt

16” 0.39 mW 4/10,000th watt

32” 0.097 mW 1/10,000th watt

64” (5.3 ft) 0.024 mW 2/100,000th watt

128” (10.6 ft) 0.006 mW 6/1,000,000th watt

256” (21.3 ft) 0.0015 mW 15/10,000,000th watt

Light bulbs would also be dangerous the were 10,000 to 1,000,000,000,000 stronger.

A 250,000 watt up to a 250,000,000,000,000 watt light bulb would also be dangerous.

WIRELESS 802.11

Wireless N provides better speeds (bandwidth) and better range by utilizing multiple antennas.

Backwards compatible with 802.11 b and g.

n

802.11n

WIRELESS 802.11 aco More reliableo Better Speedo Better Rangeo Steady Connectiono Ideal for video steaming or gaming

WIRELESS 802.11 ac

Key advantages of 802.11ac over 802.11n:o Gigabit speed wireless with approximately 3 times the

performance of 802.11no Better performance at any range with fewer dead spotso More reliable connections for media streaming with

beam-formingo More Wi-Fi bandwidth on your mobileo Only utilizes the 5 GHz Band, which is less prone to interferenceo Backward compatible to 802.11 a & n, which also use the 5 GHz

band

Next Generation Gigabit Wi-Fi