Rapid-acquisition access channel scheme for CDMA systems
First Claim
1. In a spread spectrum CDMA communication system in which a station transmits a short synchronization signal to allow a second station to (1) recognize that a signal is present, (2) resolve frequency uncertainty, (3) acquire the spreading code timing, (4) acquire frame and symbol synchronization, and (5) demodulate data which may contain user identification and other data, the improvement comprising:
- means for generating and transmitting a burst signal comprising an Acquisition Field during which the carrier is biphase modulated with a pseudo-noise (PN) sequence, a Sync Field during which a synchronization sequence is mod-2 added to the PN sequence with one chip of the sync sequence equal to one or more periods of the PN sequence, and a data field with m-ary orthogonal code words mod-2 added to the PN sequence with one chip of the code word equal to one or more periods of the PN sequence.
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Abstract
A spread spectrum CDMA communication system in which a station transmits a short synchronization signal to allow a second station to (1) recognize that a signal is present, (2) resolve frequency uncertainty, (3) acquire the spreading code timing, (4) acquire frame and symbol synchronization, and (5) demodulate data which may contain user identification and other data. The rapid acquisition channel (RAC) includes a burst signal comprising of an Acquisition Field during which the carrier is biphase modulated with a pseudo-noise (PN) sequence, a Sync Field during which a synchronization sequence is mod-2 added to the PN sequence with one chip of the sync sequence equal to one or more periods of the PN sequence, and a data field with m-ary orthogonal code words mod-2 added to the PN sequence with one chip of the code word equal to one or more periods of the PN sequence.
83 Citations
8 Claims
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1. In a spread spectrum CDMA communication system in which a station transmits a short synchronization signal to allow a second station to (1) recognize that a signal is present, (2) resolve frequency uncertainty, (3) acquire the spreading code timing, (4) acquire frame and symbol synchronization, and (5) demodulate data which may contain user identification and other data, the improvement comprising:
means for generating and transmitting a burst signal comprising an Acquisition Field during which the carrier is biphase modulated with a pseudo-noise (PN) sequence, a Sync Field during which a synchronization sequence is mod-2 added to the PN sequence with one chip of the sync sequence equal to one or more periods of the PN sequence, and a data field with m-ary orthogonal code words mod-2 added to the PN sequence with one chip of the code word equal to one or more periods of the PN sequence. - View Dependent Claims (2, 3)
- 4. An orthogonal CDMA (OCDMA) communication system comprising a base station receiver means for receiving a plurality of spread spectrum signals from a corresponding plurality of subscriber stations on a selected frequency channel, each signal from a subscriber station being composed of data symbols overlaid with one set of orthogonal functions and a PN sequence, the signals from subscriber stations being synchronized to arrive at the base station in time and frequency synchronism, a subscriber station Return Access Channel (RAC) comprised of a transmitter means at the subscriber station for transmitting a spread spectrum RAC burst signal in an assigned frequency band to allow the base station to (1) recognize that a signal is present, (2) resolve frequency uncertainty, (3) acquire the spreading code timing, (4) acquire frame and symbol synchronization, and (5) demodulate data which may contain user identification and other data, and means for transmitting a burst signal consisting of an Acquisition Field during which the carrier is biphase modulated with a pseudo-noise (PN)sequence, a Sync Field during which a synchronization sequence is mod-2 added to the PN sequence with one chip of the sync sequence equal to one or more periods of the PN sequence, and a data field with m-ary orthogonal code words mod-2 added to the PN sequence with one chip of the code word equal to one or more periods of the PN sequence.
Specification