CCSK Modulation for Non-Binary Code Transmission in Noise
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Solution Overview
Problem
Existing methods for transmitting non-binary LDPC codes in noisy communication channels, such as those using orthogonal M-ary spread spectrum modulation, are complex and costly due to the need for multiple filters and cross-correlation calculations during demodulation.
Innovation Solution
The use of cyclic code-shift modulation (CCSK) with a pseudo-random sequence and the insertion of a cyclic prefix, allowing for simpler demodulation through fast Fourier transform (FFT) operations and requiring only a single pseudo-random generator.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If orthogonal M-ary spread spectrum modulation is used to transmit non-binary LDPC codes, then noise immunity is improved, but device complexity and implementation cost increase due to multiple filters and cross-correlation calculations
Solution Approach 1:
The patent changes the modulation parameter from orthogonal M-ary spread spectrum to cyclic code-shift keying (CCSK). This parameter change transforms the demodulation process from requiring multiple filters and cross-correlation calculations to using simple FFT-based frequency domain equalization, thereby reducing device complexity while maintaining noise immunity through the cyclic prefix and frequency diversity
Solution Approach 2:
The patent replaces the time-domain correlation-based demodulation mechanism with a frequency-domain FFT-based mechanism. By substituting the mechanical correlation calculation process with FFT operations, the system achieves the same noise immunity function with significantly reduced computational complexity and simpler implementation
2Device complexity
If cyclic code-shift modulation with FFT-based demodulation is used, then device complexity is reduced, but code length must be increased to maintain performance
Solution Approach 1:
The patent moves the signal processing from the time domain to the frequency domain by applying FFT-based demodulation. This dimensional change allows the system to achieve robust performance with simpler operations, and the code length extension is compensated by the frequency domain processing that exploits cyclic properties and frequency diversity
3Ease of manufacture
If a single pseudo-random generator is used for CCSK modulation, then implementation cost is reduced, but sequence design requirements become more stringent
Solution Approach 1:
The patent changes the sequence generation parameter from requiring multiple independent pseudo-random sequences to using a single pseudo-random sequence with cyclic shifts. This parameter change reduces implementation cost by eliminating multiple generators while the cyclic structure provides sufficient sequence diversity through phase rotation in the frequency domain
Data Source
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AI summary
The invention concerns a method for transmitting symbols of non binary error correcting code words via a transmission channel. The method comprises a first modulation (110) associating each code word symbol of p bits with a sequence of at least 2p chips from 2p possible sequences, a second modulation (120) to modulate the phase or amplitude of a carrier signal with the sequences associated with the code words, and a step of transmitting the modulated carrier signal via said transmission channel. According to the invention, the first modulation is a spread spectrum modulation of the cyclic code shift keying type using a basic pseudo-random sequence of at least 2p chips, the possible 2p sequences being obtained by a circular shift of the basic pseudo-random sequence and a cyclic prefix is inserted into each symbol to be transmitted.