Coded Continuous Phase Modulation for Adjacent Channel Interference
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Solution Overview
Problem
Satellite communication systems face performance degradation due to adjacent channel interference (ACI) in multi-access wireless communication systems, particularly in Frequency Division Multiple Access (FDMA) systems, where reduced frequency separation between channels increases ACI, leading to suboptimal error rate performance and spectral efficiency.
Innovation Solution
A coded Continuous Phase Modulation (CPM) scheme is implemented, utilizing low-complexity binary convolutional codes and S-random bit interleaving, which shapes the power spectrum to enhance resilience to ACI and improves error rate performance by optimizing modulation parameters and pulse shapes, such as raised-cosine and rectangular pulses, to minimize frame error rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If frequency separation between adjacent channels is reduced to achieve high bandwidth efficiency, then spectral efficiency is improved, but adjacent channel interference increases causing performance degradation
Solution Approach 1:
The patent applies continuous phase modulation with specific modulation parameters (modulation index h, pulse shape, pulse width) to change the spectral characteristics of the signal. By carefully selecting these parameters, the power spectrum is shaped to minimize adjacent channel interference while maintaining high spectral efficiency, thus resolving the contradiction between bandwidth efficiency and interference levels
Solution Approach 2:
The patent converts the potential harm of spectral spreading into a benefit by using continuous phase modulation to shape the power spectrum. The modulation scheme transforms the signal in such a way that the spectral energy is concentrated in a controlled manner, turning what would be interference into useful signal energy, thereby improving performance despite reduced frequency separation
2Device complexity
If conventional modulation schemes are used to simplify the system, then device complexity is reduced, but error rate performance deteriorates under adjacent channel interference
Solution Approach 1:
The patent employs a composite approach by combining continuous phase modulation with binary convolutional codes and S-random bit interleaving. This composite scheme integrates multiple techniques to achieve robust error rate performance under adjacent channel interference while keeping the overall system complexity manageable through the use of low-complexity convolutional codes
3Reliability
If binary convolutional codes and S-random bit interleaving are applied to improve error rate performance, then reliability is improved, but device complexity increases
Solution Approach 1:
The patent applies partial action by using low-complexity binary convolutional codes with specific generator polynomials rather than more complex coding schemes. The S-random bit interleaving with a small value of S provides sufficient performance improvement without the excessive complexity of more elaborate interleaving schemes, thus achieving a balance between reliability and complexity
Data Source
AI summary
A new coded continuous phase modulation (CPM) scheme is proposed to enhance physical layer performance of the current DVB-RCS standard for a satellite communication system. The proposed CPM scheme uses a phase pulse design and combination of modulation parameters to shape the power spectrum of CPM signal in order to improve resilience to adjacent channel interference (ACI). Additionally, it improves error rate performance at both high and low frame error rates using low complexity binary convolutional codes and S-random bit interleaving. Phase response using the proposed CPM scheme is a weighted average of the conventional rectangular and raised-cosine responses and provides optimum response to minimize frame error rate for a given data rate.