July 2010
Intermediate to advanced
350 pages
14h 19m
English
Content preview from Smart Phone and Next Generation Mobile Computing
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112 Smart Phone and Next-Generation Mobile Computing
Amplitude-shift keying and PSK can be combined to offer more vari-
ations of phase shifts on the phase domain. Quadrature amplitude
modulation (QAM) is such a scheme in which multiple levels of
amplitudes coupled with several phases provide far more unique sym-
bol shifts over the same bandwidth than used by PSK over the same
bandwidth. QAM is widely used in today’s modems.
Apart from analog and digital modulation, another category of
modulation that should be discussed for wireless communication is
analog-to-digital data modulation, a procedure sometimes referred to
as digitization. Two major digitization schemes are pulse-code mod-
ulation (PCM) and delta modulation. PCM samples an input analog