Acquisition method for DSSS communications

摘要

Method for indicating the end of an acquisition procedure between a transmitter and receiver in a direct sequence spread spectrum communications system. At a transmitter, a first acquisition code having a first acquisition code period and comprised of digital bits at a first bit rate is generated. The first digital acquisition code is modulated by a pseudo-noise code repeating at a pseudo-noise code period and consisting of a sequence of chips at a chip rate greater than the first bit rate, and wherein the first acquisition code period is an integer multiple of the pseudo-noise code period. A carrier frequency is modulated by the first digital acquisition code modulated by the pseudo-noise code. The carrier is modulated by the first digital acquisition code modulated by the pseudo-noise code is transmitted for a first period of time. A receiver is synchronized to the chip rate and carrier frequency, then to the pseudo-noise code period, next to the period of the data bit rate, and then to the first acquisition code period. At the transmitter a second acquisition code is generated having a second acquisition code period and comprised of digital bits at a second bit rate, the second bit rate equal to the bit rate of the first acquisition code period. The second digital acquisition code is modulated by the pseudo-noise code. The carrier frequency is modulated by the second digital acquisition code modulated by the pseudo-noise code. The carrier modulated by the second acquisition code modulated by the pseudo-noise code is transmitted for a second period of time equal to the second acquisition code period. The receiver is sychronized to the second acquisition code, the end of the second acquisition code indicating the end of the acquisition procedure.