Editing Pulse-position modulation (section)

{{Short description|Form of signal modulation using time shifts}}
{{more footnotes|date=November 2013}}
{{Modulation techniques}}

'''Pulse-position modulation''' ('''PPM''') is a form of signal [[modulation]] in which ''M'' message bits are encoded by transmitting a single pulse in one of <math>2^M</math> possible required time shifts.<ref>{{cite journal|author=K. T. Wong|title=Narrowband PPM Semi-Blind Spatial-Rake Receiver & Co-Channel Interference Suppression|url=http://www.eie.polyu.edu.hk/~enktwong/ktw/WongKT_ETT0307.pdf|publisher=The Hong Kong Polytechnic University|journal=European Transactions on Telecommunications|volume=18|issue=2|doi=10.1002/ett.1147|pages=193–197|date=March 2007|access-date=2013-09-26|archive-url=https://web.archive.org/web/20150923234515/http://www.eie.polyu.edu.hk/~enktwong/ktw/WongKT_ETT0307.pdf|archive-date=2015-09-23|url-status=dead}}</ref><ref>{{cite journal|author=Yuichiro Fujiwara|title=Self-synchronizing pulse position modulation with error tolerance|arxiv=1301.3369|journal=IEEE Transactions on Information Theory|volume=59|year=2013|doi=10.1109/TIT.2013.2262094|pages=5352–5362}}</ref>  This is repeated every ''T'' seconds, such that the transmitted bit rate is <math>M/T</math> bits per second. It is primarily useful for [[optical communication]]s systems, which tend to have little or no [[Multipath propagation|multipath]] interference.