Apparatus and method for digital data transmission using orthogonal cyclic codes

A receiver for a code division multiplexed system, comprising:

• a demodulator including one or more mixers for receiving digital samples of one or more radio frequency carrier signals modulated with code division multiplexed data and mixing said samples with one or more local carrier signals to generate mix products including sidebands, and including filters for filtering out one or more sidebands which include spread spectrum chip data and recovering said spread spectrum chip data;
• a code division demultiplexer for receiving said chip data and organizing said chip data into frames comprised of a plurality of symbols and including matrix multiplication circuitry for multiplying said symbols times a spreading code matrix which is the inverse of the spreading code matrix used to spread the spectrum of said chip data at a transmitter to recover received chip data which may be corrupted by noise effects during transmission from the actual transmitted chip data, each received chip having been encoded at the transmitter which transmitted said chip with one or more redundant bits useful to a Viterbi decoder;
• a detector coupled to received said received chip data including a slicer circuit and a memory for comparing each received chip against the closest legitimate chip values in a received chip space representing the values of all possible chip s that could have been transmitted to cause said received chip, and for making preliminary determinations as to what the actual transmitted chip was for each received chip ;
• a Viterbi decoder having a memory, for receiving said preliminary determinations and using said one or more redundant bits and data stored in said memory regarding previous states to make detect and correct errors made by said detector and for outputting for each chip a multibit value representing the original data transmitted;
• and
• deframer circuitry for reassembling the original data stream received as said transmitter using said multibit values.

A receiver for a code divsion multiplexed system, comprising:

• a demodulator including circuitry to mix local carrier signals with spread spectrum input signals;
• a code division multiple access demultiplexer coupled to an output of said demodulator including circuitry to despread the spectrum of signals from said demodulator;
• a detector including a slicer circuit coupled to an output of said code division multiple access demultiplexer for making preliminary decisions as to what data was sent;
• a Viterbi decoder coupled to said detector including a memory for using redundant bits in the data received to detect and correct errors made by said slicer circuit to output corrected received chip corresponding to the data which was transmitted.

A process for code division multiplexing of digital data, comprising:

• receiving data from a plurality of sources and reorganizing said data by interleaving some data from each source into each of a plurality of symbols of a frame each symbol comprising an information vector;
• code division multiplexing said chip by multiplying each information vector times a code matrix comprised of orthogonal spreading codes to generate spread spectrum data;
• and
• modulating said spread spectrum chip onto one or more radio frequency carriers.

A process of receiving code division multiplexed data, comprising:

• receiving spread spectrum radio frequency signals having data from different sources encoded therein, and mixing said signals with local carrier signals to demodulate said spread spectrum radio frequency signals;
• demultiplexing the demodulated signal using an inverse code matrix of the spreading code matrix used at the transmitter to spread the spectrum of the chip being transmitted;
• using a slicer detector to make preliminary determinations from the received, noise corrupted data what data was sent;
• and
• using a Viterbi decoder to detect and correct errors in the preliminary determinations to recover the transmitted data.