US 5,416,797 A · System and method for generating signal waveforms in a CDMA cellular telephone system

Abstract

A 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, hi-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.

Claims36

Dependent claims

A spread spectrum modulator for modulating variable rate input digital data for transmission, said input digital data being provided in data frames of a predetermined time duration with each frame of input digital data having a number of data bits corresponding to one of several predetermined frame bit counts, said modulator comprising:

a convolutional encoder having an input receiving said frames of input digital data and an output;
a data interleaver having an input coupled to said convolutional encoder output and an output;
a Walsh function encoder having an input coupled to said interleaver output and an output;
a first pseudorandom noise (PN) code generator having an output;
a first exclusive-OR gate having a pair of inputs and an output, one of said first exclusive-OR gate inputs coupled to said first PN code generator output and another of said first exclusive-OR gate inputs coupled to said Walsh encoder output;
a second PN code generator having an output;
a third PN code generator having an output;
a second exclusive-OR gate having a pair of inputs and an output, one of said second exclusive-OR gate inputs coupled to said second PN code generator output and another of said second exclusive-OR gate inputs coupled to said first exclusive-OR gate output;
and
a third exclusive-OR gate having a pair of inputs and an output, one of said third exclusive-OR gate inputs coupled to said third PN code generator output and another of said third exclusive-OR gate inputs coupled to said first exclusive-OR gate output.

7 more elements

A method for spread spectrum modulating digital data for transmission, comprising:

convolutional encoding digital data to produce symbol data in a first ordered sequence;
reordering said symbol data of said first ordered sequence to a second ordered sequence;
grouping symbols of said second ordered sequence of symbol data into corresponding symbol groups;
determining from a binary value formed by said symbol data in each symbol group a respective Walsh function symbol of a plurality of Walsh function symbols;
generating a first pseudorandom noise (PN) code;
and
combining said Walsh function symbols with said first PN code to produce first PN spread data.

4 more elements

Dependencies are inferred from the claim text.

System and method for generating signal waveforms in a CDMA cellular telephone system

Life of this patent

System and method for generating signal waveforms in a CDMA cellular telephone system

Life of this patent

Abstract

Claims36