1. Modulation is the process of putting binary bits (0s and 1s)
onto a sine wave
There are 3 basic ways of modulating a sine wave:
◦ Amplitude
Changing the height of the peaks of the waves to represent the binary
values
◦ Frequency
Changing the frequency of the waves (the number of waves generated
per second) to represent the value
◦ Phase
Turning the wave off and on to represent the value (like Morse code)
As wireless speeds increase more efficient ways of
modulating the wave and encoding the bits are needed
Fast modulation techniques use combinations of 2 or 3
basic methods
2. OFDM Orthogonal frequency division multiplexing
◦ Divides the transmission channel into sub-channels
◦ The digital data is divided and sent in parallel along sub-channels
◦ Modulation techniques such as BPSK, QPSK and QAM are used
for each sub-channel
QPSK and BPSK
◦ These techniques change the phase
of the wave when the binary value changes
16-QAM,64-QAM, 256-QAM
◦ Uses amplitude and phase to signal symbols
◦ Each symbol represents a code group: 4 bits (16-QAM) are
signalled at the same time using 1 symbol or 6 bits for 64 QAM or
◦ 8 bits for 256 QAM