Apparatus for and method of adaptive synchronization in a spread spectrum communications receiver
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United States of America Patent
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Sep 2, 2003
Grant Date -
N/A
app pub date -
Oct 12, 1999
filing date -
Oct 12, 1999
priority date (Note) -
Expired
status (Latency Note)
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Abstract
An apparatus for and method for acquiring synchronization for use in communications systems, i.e., acquiring the presence of a packet of data and associated timing information. A sequence of symbols having known rotation and phase is transmitted to the receiver. The receiver attempts to match the received vectors in a predefined manner in order to determine whether a signal or noise is being received. CSK modulation is used for the synchronization acquisition stage and, any desired data carrying modulation may be switched to once synchronization is obtained, which may or may not be CSK. The transmitter transmits data in the form of packets to the receiver, wherein each packet is preceded by a preamble comprising a number of symbols. The length of the preamble can be any suitable number of symbols such that the receiver is able to synchronize with the transmitter. The preamble comprises a sequence of rotated or non-rotated symbols, inverted or non-inverted (or generally phase-rotated by some amount). In some embodiments, the preamble comprises a sequence of non-rotated symbols (or symbols with a constant fixed rotation) followed by one or more symbols with a known random shift, the rotation applied to each rotated symbol being independent of the rotation applied to other symbols.
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