Method and apparatus for efficient bandwidth communication
First Claim
1. A method for improving the bandwidth efficiency of a continuous phase modulation signal comprised of plural symbols over a communication channel comprising the steps of:
- coding an input data stream;
modulating a carrier frequency with the coded input data stream as a constant envelope continuous phase modulation waveform; and
converting the constant envelope continuous phase modulation waveform into a non-constant envelope continuous phase modulation waveform thereby improving the bandwidth of the signal,wherein the step of converting includes interpolation of a path between constellation points along a chord connecting successive constellation points.
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Abstract
A method and apparatus for improving the bandwidth efficiency of a constant envelope continuous phase modulation waveform and transmitting data in a bandwidth efficient manner is disclosed. The method and apparatus utilizes a non-constant envelope continuous phase modulation signal which possesses many of the advantages of a multiple modulation index continuous phase modulation signal. One such advantage is the natural trellis structure of a multiple modulation index continuous phase modulation signal. In comparison to a constant envelope continuous phase modulation waveform, the non-constant envelope continuous phase modulation signal possesses a reduced transmit signal spectra and may also be demodulated by a standard maximum likelihood demodulator without any loss of performance.
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Citations
30 Claims
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1. A method for improving the bandwidth efficiency of a continuous phase modulation signal comprised of plural symbols over a communication channel comprising the steps of:
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coding an input data stream; modulating a carrier frequency with the coded input data stream as a constant envelope continuous phase modulation waveform; and converting the constant envelope continuous phase modulation waveform into a non-constant envelope continuous phase modulation waveform thereby improving the bandwidth of the signal, wherein the step of converting includes interpolation of a path between constellation points along a chord connecting successive constellation points. - View Dependent Claims (2, 3, 4, 5, 6)
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- 7. A method for improving the bandwidth efficiency of a constant envelope continuous phase modulated waveform signal encoded with data symbols, comprising the steps of varying a complex amplitude of the signal between successive constellation points prior to transmission and controlling the complex amplitude of the signal to follow a path between successive constellation points that is more direct than the arc of a unit circle circumscribing the constellation points.
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11. A method of transmitting data as a non-constant envelope continuous phase modulation signal comprised of a plurality of symbols in a constellation comprising the steps of:
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coding the plurality of symbols into a plurality of CPM symbols; and transecting ones of said CPM symbols by a direct path during modulation of the coded plurality of symbols thereby enabling the transmission of a non-constant envelope continuous phase modulation waveform. - View Dependent Claims (12, 13, 14, 15)
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- 16. A method for modulating an input data stream wherein said input data stream is comprised of a plurality of symbols, said symbols represented as constellation positions in a complex plane comprising the steps of generating a continuous phase modulation waveform modulated with the plurality of symbols, and modifying the complex amplitude between the successive constellation positions to traverse the complex plane in a straight path from one of said constellation positions to another of said constellation positions.
- 20. In a constant envelope continuous phase modulation waveform communication system including a transmitter for transmitting data as continuous phase modulation symbols and a receiver with a constant envelope continuous phase modulation demodulator, the improvement comprising a conversion means for converting a constant envelope continuous phase modulation waveform into a non-constant continuous phase modulation waveform prior to transmission such that the complex amplitude of the waveform between successive constellation points is less than the complex amplitude at each of the constellation points.
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26. A method for transmitting an input data stream as phase locations in a complex plane in a continuous phase modulation waveform, comprising the steps of:
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modulating the continuous phase modulation waveform with the input data stream; transecting the complex plane between successive phase locations in a substantially straight path.
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27. A method for communicating data comprising the steps of:
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transmitting data as a plurality of symbols within a complex plane as a continuous phase modulated waveform; and varying the magnitude of the waveform in the complex plane during the transition between ones of said symbols. - View Dependent Claims (28, 29, 30)
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Specification