Receiver for bandspread signals
Spread spectrum correlator
Method and apparatus for increasing the data rate for a given symbol rate in a spread spectrum system
Multiple-signal spread-spectrum transceiver
CDMA subtractive demodulation
Signal analysis technique for determining a subject of binary sequences most likely to have been transmitted in a multi-node communication network
Data recovery technique for asynchronous CDMA systems
Multi-rate spread system Patent #: 5341396
ApplicationNo. 196577 filed on 02/15/1994
US Classes:375/150, Correlation-type receiver380/34Plural carrier frequencies
ExaminersPrimary: Swann, Tod R.
Attorney, Agent or Firm
International ClassH04B 001/69
AbstractA detector of a multiple-sequence spread spectrum signal uses a Hadamard transform (106) to simultaneously correlate a received signal comprising two sequences (64) with a plurality of candidate sequences. The received signal is stripped of the first sequence (65, 66), and the signal is permuted (via a table lookup) (104). A Hadamard transform is performed on the permuted data and the candidate sequences (106). After transformation, the data is permuted again (112 ) to determine the symbol (sequence) transmitted. Alternatively, Fast Fourier Transforms (FFTs) (FIG. 3), Winograd Fourier Transform Algorithms (WFTA), or other cyclic correlation algorithms (FIG. 5) may be used to compute the transformation. In a preferred embodiment, a "pilot" signal is transmitted in quadrature (90 degrees phase offset) with an information-bearing signal. And, a block error correcting code (150) (e.g., a modified Reed-Solomon code) is transmitted with the information-bearing signal a(t). The block length of the block error correcting code (150) is equal to an integral multiple of the period of the pilot signal. The period of the pilot signal is an integral multiple of the information bearing signal. Thus, carrier recovery, sequence synchronization, and block code synchronization are all achieved simultaneously by correlating (synchronizing) the received signal with a baseband version of the pilot signal.
Field of SearchPlural carrier frequencies