Modulation involves encoding binary data onto a sine wave by changing the wave's amplitude, frequency, or phase. Common modulation techniques include amplitude shift keying, frequency shift keying, and phase shift keying. More advanced techniques like orthogonal frequency-division multiplexing divide the channel into sub-channels and use modulation such as BPSK, QPSK, and QAM to send data in parallel across sub-channels. Higher order QAM encodings use amplitude and phase to represent more bits per symbol.

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