Coded digital modulation method for communication system

• US 20030223507A1
• Filed: 06/04/2002
• Published: 12/04/2003
• Est. Priority Date: 06/04/2002
• Status: Active Grant

• Current Assignee: Mudalla Technology, Inc.
• Original Assignee: Agence Spatiale Europeenne
• Inventors: De Gaudenzi, Riccardo, Ponticelli, Beatrice, Martinez Vicente, Alfonso, Guillen i Fabregas, Alberto
• Granted Patent: US 7,123,663 B2
• Time in Patent Office: Days
• US Class Current: 375/279
• CPC Class Codes: H04L 27/3411 reducing the peak to average power ratio or the mean power of the constellation; Arrangements for increasing the shape gain of a signal set

Abstract

A new class of 16-ary Amplitude and Phase Shift Keying (APSK) coded modulations, called double-ring APSK modulation, based on an amplitude and phase shift keying constellation in which the locations of the digital signals to be encoded are placed on two concentric rings of equally spaced signal points. The APSK constellation parameters are optimised so as to pre-compensate the impact of non-linearities. The new modulation scheme is suited for being used with different coding schemes. It is shown that, for the same coding scheme, pre-distorted double-ring APSK modulation significantly outperforms classical 16-QAM and 16-PSK over a typical satellite channel, due to its intrinsic robustness against the high power amplifier non-linear characteristics. The proposed coded modulation scheme is shown to provide a considerable performance advantage for future satellite multi-media and broadcasting systems.

Claims

1. A coded digital modulation and demodulation method based on amplitude phase shift keying, said digital modulation method comprising the steps of:

generating a digital signal constellation in which the digital signal points are located on two concentric rings of equally spaced signal points having respective predetermined radii,

said digital signal points on one of said concentric rings having a predetermined relative phase shift in relation to the signal points on the other of said concentric rings,

code modulating the selected constellation digital signal using an amplitude phase shift keying scheme, and

said digital demodulation method for demodulating the modulated signals obtained by said digital modulation method, said digital demodulation method comprising the steps of;

receiving said digital modulated signal, and

decoding said received digital modulated signal using a selected decoding code.

2. A coded digital modulation method as claimed in claim 1, wherein the total number of points on said concentric rings is 16.

3. A coded digital modulation and demodulation method as claimed in claim 1, wherein the radii of the concentric rings and the relative phase shift between the signal points on said concentric rings are selected so as to pre-compensate the distortion effects of a high power amplifier used in a chain.

4. A coded digital modulation and demodulation method as claimed in claim 1, wherein the step of code modulating the selected constellation digital signal comprises the step of mapping a binary code onto the constellation signals.

5. A coded digital modulation and demodulation method as claimed in claim 1, wherein the step of code modulating the selected constellation digital signal comprises the steps of coupling a binary turbo code to a modulator unit through a block interleaver and mapping the code output onto the constellation signals through Gray mapping.

6. A coded digital modulation and demodulation method as claimed in claim 1, wherein the step of code modulating the selected constellation digital signal comprises the steps of combining a binary convolution code concatenated through a random block interleaver to an accumulator to generate a first code block, repeating the operation to generate a number of second code blocks, adding said second code blocks to said first code block and mapping the code output onto the constellation signals through Gray mapping.

7. A coded digital modulation and demodulation method as claimed in claim 6, wherein said code blocks are generated by a turbo convolutional encoder having a number of states sized according to the required bit error rate performance.

8. A coded digital modulation and demodulation method as claimed in claim 1, wherein step of demodulating the modulated signal obtained by said modulation method further comprises the step of performing a coherent synchronization process on the symbol signals.

9. A coded digital modulation and demodulation method as claimed in claim 8, wherein the step of performing a coherent synchronization process consists in performing a digital blind carrier phase estimation based on four quadrant phase averaging of the constellation samples.