Page:Wireless Networking in the Developing World (WNDW) Third Edition.pdf/31

 1. RADIO PHYSICS

5

SI symbols atto

10−18

1/1000000000000000000

a

femto

10−15

1/1000000000000000

f

pico

10−12

1/1000000000000

p

nano

10−9

1/1000000000

n

micro

10−6

1/1000000

µ

milli

10−3

1/1000

m

centi

10−2

1/100

c

kilo

10 3

1000

k

mega

10 6

1000000

M

giga

10 9

1000000000

G

tera

10 12

1000000000000

T

peta

10 15

1000000000000000

P

exa

10 18

1000000000000000000

E

Knowing the speed of light, we can calculate the wavelength for a given frequency. Let us take the example of the frequency of 802.11b wireless networking, which is: f = 2.4 GHz = 2,400,000,000 cycles / second wavelength (λ) = c / f = 3*108 / 2.4*109 = 1.25*10-1 m = 12.5 cm Frequency and therefore wavelength determine most of an electromagnetic wave’s behaviour. It governs the dimensions of the antennas that we build as well as the effect of the interactions with objects that are in the propagation path, including the biological effects in living beings. Wireless standards of course are distinguished by more than just the frequency they are working at - for example, 802.11b, 802.11g, 802.11n and 802.16 can all work at 2.4 GHz -, yet they are very different from one another.