Quadrature Phase Shift Keying (QPSK) is a form of Phase Shift Keying in which dibits are modulated at once, selecting one of four possible carrier phase shifts (0, 90, 180, or 270 degrees). As a symbol is transmitted by two bits it carries twice as much information as ordinary PSK using the same bandwidth. QPSK is used for satellite transmission of MPEG2 video, cable modems, videoconferencing, cellular phone systems, and other forms of digital communication over an RF carrier.
Published in Chapter:
Modulation Recognition for Software Defined Radio Signal
Sudhar Sophia (Sri Krishna College of Engineering & Technology, India), M. Madheswaran (Muthayammal College of Engineering, India), and S. Sasikumar (Hindustan College of Engineering & Technology, India)
Copyright: © 2012
|Pages: 15
DOI: 10.4018/978-1-61520-655-1.ch023
Abstract
Software Defined Radio (SDR) is the foundation for universal wireless devices. To realize SDR system, the parameters like carrier frequency, symbol rate, and modulation scheme should be reconfigured by the adaptive receiver. Automatic modulation recognition (AMR) algorithm has to identify the modulation scheme of a transmitted signal with a high probability of success within a short observation time. Blind recognition algorithms are useful in identifying the modulation type without any prior knowledge of the transmitted signal parameters. The blind modulation detection determines the type of modulation within the information conveyed by the least possible number of received samples. Therefore, the objective is to make use of the distribution of data or errors to make a statistical inference about type of modulation used.