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# difference between BPSK and 16QAM

Posted on 2011-05-10
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what is the difference between BPSK and 16QAM
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Question by:mc87

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16QAM is a subset of the broader scope - QAM (quadrature amplitude modulation).  Additionally BPSK can be assumed a subset as well, though developed along differing lines over time.  Just gee-wiz info but helpful to put things into scope none the less.

What little I do know conscerning the differences.

BPSK is a subset of PSK (Phase Shift Keying) and uses only a single carrier signal, phasing at 180 degree intervals for data (binary) representation (ex. 0 degees = 1, 180 degrees = 0).  Variants of BPSK are used extensively in 802.11.  Additionally, BPSK in its purest form is presented in a linear time phase model (one dimensional).  Of the two, BPSK and QAM, BPSK offers the highest data reliability rate (lowest receiver data error rate).

16QAM as noted above is a direct subset of QAM.  It is utilized in both digital and analog signal modulation schemes and is most often implemented in hard-line (terrestrial) telecommunications - think digital television and cable modems.  QAM and all its direct variants utilize at least 2 carrier signals for data transmission set at different amplitudes, the two waves being out of phase with each other by 90 degrees (quadrature carriers).  This allows for higher transmission rates, therefore more robust data density rates but at the cost of increased data error rate.  This introduces the major difference between the two (BPSK and QAM).  BPSK uses phase shifting only for data representation whereas QAM utilizes phase shifting as well as amplitude modulation.

The if needed:

http://cnx.org/content/m10280/latest/
http://www.dslreports.com/forum/r21274392-BPSK-QPSK-QAM-16-QAM-64
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