Efficient quadrature code position modulation
OwnerPaul Edward Gorday, Edgar Herbert Callaway JR. +1inventors
InventorsPaul Edward Gorday, Edgar Herbert Callaway JR., Geetha Benamanahalli Nagaraj
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Abstract
A technique and apparatus for implementing code position modulation (CPM) on in-phase and quadrature-phase components of a radio frequency (RF) carrier. The technique simplifies the modulation/demodulation process by requiring only one pseudo-noise (PN) sequence to be stored in the transceiver device. As a consequence, only a single unique PN sequence needs to be stored in the transceiver, thus resulting in a reduction of circuit complexity.
Claims21
A transmitter for generating first and second modulation signals in response to first and second input data symbols in a communication system, said transmitter comprising:
- a transmitter memory for storing a code sequence;
- a first time shifting means for time-shifting said code sequence by a first time-shift, said first time-shift being determined by said first data symbol, said first shifting means being coupled to said transmitter memory and generating a first encoded sequence;
- and
- a second time shifting means for reversing and time-shifting said code sequence by a second time-shift, said second time-shift being determined by said second data symbol, said second shifting means being coupled to said transmitter memory and generating a second encoded sequence.
A receiver for decoding a complex modulated signal, said receiver comprising:
- a receiver memory for storing a code sequence;
- a first correlator coupled to said receiver memory for determining the correlation between a time-shifted version of said code sequence and said complex modulated signal;
- and
- a second correlator coupled to said receiver memory for determining the correlation between a time-shifted and time-reversed version of said code sequence and said complex modulated signal.
A communication system, comprising:
- a transmitter for generating first and second modulation signals in response to first and second input data symbols, said transmitter comprising:
- a transmitter memory for storing a code sequence;
- a first time shifting means for time-shifting said code sequence by a first time-shift, said first time-shift being determined by said first data symbol, said first shifting means being coupled to said transmitter memory and generating a first encoded sequence;
- and
- a second time shifting means for reversing and time-shifting said code sequence by a second time-shift, said second time-shift being determined by said second data symbol, said second shifting means being coupled to said transmitter memory and generating a second encoded sequence;
- a receiver for decoding a complex modulated signal, said receiver comprising:
- a receiver memory for storing a code sequence;
- a first correlator coupled to said receiver memory for determining the correlation between a time-shifted version of said code sequence and said complex modulated signal;
- and
- a second correlator coupled to said receiver memory for determining the correlation between a time-shifted and time-reversed version of said code sequence and said complex modulated signal.
A communication transmitter for generating first and second modulation signals in response to first and second input data symbols, said transmitter comprising:
- a transmitter memory for storing a code sequence;
- a time-shifting means for time-shifting said code sequence by a time-shift, said time-shift being determined by said first or second data symbol, said shifting means being coupled to said transmitter memory and generating an encoded sequence corresponding to said first or second data symbol;
- a bi-directional register operable to store said encoded sequence, said bi-directional register having first and second read directions;
- and
- a selector operable to select said first or second read directions according to whether said encoded sequence corresponds to said first or second data symbol;
- wherein said first modulation signal is generated when said first read direction is selected and said second modulation signal is generated when said second read direction is selected.
A receiver for decoding a complex modulation signal in a communication receiver to recover a data value, said receiver comprising:
- an M-chip shift register for storing and time shifting an M-chip code sequence;
- a bi-directional register operable to store said complex modulation sequence, said bi-directional register having first and second write directions;
- a selector coupled to said bi-directional register and operable to select between said first and second write directions;
- a correlator coupled to said bi-directional register and said M-chip shift register and operable to correlate said complex modulation signal with said M-chip code sequence to produce a correlation signal;
- a peak detector for detecting a peak in said correlation signal;
- and
- means responsive to said peak detector and said M-chip shift register for recovering said data value.
A method for encoding first and second input data symbols, each input data symbol having one of N values, said method comprising:
- storing a pseudo-noise code sequence in a memory;
- time-shifting said pseudo-noise code sequence by an amount determined by the first input symbol to obtain M chips of an in-phase encoded digital signal;
- and
- time-shifting the time-reversal of said pseudo-noise code sequence by an amount determined by the second input symbol to obtain M chips of a quadrature encoded digital signal;
A method for decoding a complex code position modulated signal, said signal representing in-phase and quadrature encoded symbols, said method comprising:
- storing a pseudo-noise code sequence in a memory;
- generating time-shifted versions of said pseudo-noise code sequence;
- determining a first correlation between the time-shifted versions of the pseudo-noise code sequence and the complex code position modulated signal;
- determining the time shift that satisfies a first predetermined correlation criteria, thereby decoding said in-phase encoded symbol;
- determining a second correlation between the time-shifted versions of the time reversal of the pseudo-noise code sequence and the complex code position modulated signal;
- and
- determining the time shift that satisfies a second predetermined correlation criteria, thereby decoding said quadrature encoded symbol.
Dependencies are inferred from the claim text.