CDMA Uplink Waveform Design for Satellite Control Network Interference
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Solution Overview
Problem
Current satellite control network (SCN) systems face inefficiencies due to severe carrier and subcarrier modulation losses, cross-modulation, and harmonics losses in Frequency Division Multiple Access (FDMA/PM), which degrade system performance and hinder spectrum sharing capabilities.
Innovation Solution
The implementation of a code division multiple access (CDMA) based uplink multiple access method using pseudorandom sequences, such as Walsh code and Gold code, to design a practical uplink spreading waveform, optimize frequency sub-band division, and configure the control system for improved performance and interference mitigation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If Frequency Division Multiple Access with Phase Modulation (FDMA/PM) is used for multiple satellite reception, then the satellite control network can support multiple satellites, but severe carrier and subcarrier modulation losses, cross-modulation and harmonics losses occur which degrade system performance and cause spectrum inefficiency
Solution Approach 1:
The patent transitions from FDMA/PM to CDMA by changing the fundamental access method parameters. CDMA uses code-based separation instead of frequency division, employing pseudorandom codes (Walsh codes, Gold codes) to differentiate satellite signals. This parameter change eliminates carrier modulation losses and cross-modulation issues inherent in FDMA/PM while maintaining multiple satellite reception capability.
2Adaptability or versatility
If Frequency Division Multiple Access with Phase Modulation (FDMA/PM) is used for multiple satellite reception, then the satellite control network can support multiple satellites, but spectrum inefficiency occurs due to modulation losses and inability to provide interference mitigation capability
Solution Approach 1:
The patent changes the multiple access method from frequency-based FDMA to code-based CDMA. This parameter change enables more efficient spectrum utilization by allowing overlapping frequency usage through code orthogonality, eliminating the spectrum waste caused by guard bands and modulation losses in FDMA/PM.
Solution Approach 2:
The patent converts the traditionally harmful pseudorandom interference in CDMA into a beneficial feature. By using carefully designed pseudorandom codes (Walsh codes for orthogonal channels, Gold codes for non-orthogonal channels), the system transforms what would be random noise into structured, manageable interference that can be separated through correlation processing, thereby improving spectrum efficiency.
3Ease of manufacture
If FDMA/PM is used in the satellite control network, then existing phase modulation modules can be utilized, but the technology cannot provide interference mitigation capability required for spectrum sharing
Solution Approach 1:
The patent changes the fundamental access method from FDMA to CDMA, which fundamentally alters how interference is handled. Instead of frequency isolation, CDMA uses code-based separation with pseudorandom sequences that provide inherent interference mitigation through processing gain and code orthogonality, enabling spectrum sharing capabilities that FDMA/PM cannot provide.
Data Source
AI summary
In accordance with various embodiments, a method for uplink multiple accessing based on code division multiple access (CDMA) technology and a related system are provided. The method comprises: designing a practical uplink spreading waveform for a code division multiple access (CDMA) based SCN by leveraging a plurality of pseudorandom sequences and investigating a channel coding block and a modulation block for the CDMA based SCN; determining an uplink frequency sub-band division for the CDMA based SCN to optimize a tradeoff between a performance and an implementation cost of CDMA based SCN; and specifying a configuration of a control system of the CDMA based SCN.