Walsh function signal scrambler
Programmable time invariant coherent spread symbol correlator
Asynchronous digital correlator and demodulators including a correlator of this type Patent #: 4933952
ApplicationNo. 543496 filed on 06/25/1990
US Classes:370/206, Quadrature carriers370/209, Walsh functions370/335, Combining or distributing information via code word channels using multiple access techniques (e.g., CDMA)370/342, Combining or distributing information via code word channels using multiple access techniques (e.g., CDMA)375/142, Having correlation-type receiver375/150, Correlation-type receiver375/309, Keying circuits380/34Plural carrier frequencies
ExaminersPrimary: Gregory, Bernarr E.
Attorney, Agent or Firm
International ClassH04L 027/30
AbstractA system and method for communicating information signals using spread spectrum communication techniques. PN sequences are constructed that provide orthogonality between the users so that mutual interference will be reduced, allowing higher capacity and better link performance. With orthogonal PN codes, the cross-correlation is zero over a predetermined time interval, resulting in no interference between the orthogonal codes, provided only that the code time frames are time aligned with each other. In an exemplary embodiment, signals are communicated between a cell-site and mobile units using direct sequence spread spectrum communication signals. In the cell-to-mobile link, pilot, sync, paging and voice channels are defined. Information communicated on the cell-to-mobile link channels are, in general, encoded, interleaved, bi-phase shift key (BPSK) modulated with orthogonal covering of each BPSK symbol along with quadrature phase shift key (QPSK) spreading of the covered symbols. In the mobile-to-cell link, access and voice channels are defined. Information communicated on the mobile-to-cell link channels are, in general, encoded, interleaved, orthogonal signalling along with QPSK spreading.