Satellite Alert Waveform and Receiver Design for Shadowed Links
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Solution Overview
Problem
Current mobile satellite communication systems face challenges in providing reliable alert messaging due to high attenuation and shadowing, which leads to inefficient power amplification and inadequate link margins, resulting in low success rates of mobile terminated calls.
Innovation Solution
The system employs an enhanced waveform design with lower peak-to-average power ratio and an advanced receiver algorithm that facilitates joint sequence detection and soft decision decoding, enabling efficient power amplification and improved link margins for reliable alert messaging in high penetration environments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional alerting methods are used in mobile satellite communication systems, then the system can provide basic alert messaging capability, but the success rate of mobile terminated calls is low due to high attenuation and shadowing
Solution Approach 1:
The patent changes the waveform parameters from conventional designs to specific optimized parameters including pulse shaping filter coefficients, roll-off factor, and modulation scheme parameters. These parameter changes enable the signal to better withstand attenuation and shadowing effects, improving the success rate of mobile terminated calls in high-attenuation environments
Solution Approach 2:
The patent applies forward error correction (FEC) coding and adds redundancy to the alert message transmission. This beforehand cushioning provides error protection that compensates for signal degradation due to attenuation and shadowing, ensuring reliable message delivery even when signal quality deteriorates
2Reliability
If higher transmission power is used to overcome attenuation, then the link margin improves, but the power amplifier efficiency decreases due to high peak-to-average power ratio
Solution Approach 1:
The patent employs a specific pulse shaping filter design with optimized coefficients and a roll-off factor of 0.35, along with π/2 BPSK modulation. These parameter changes reduce the peak-to-average power ratio of the transmitted signal, allowing the power amplifier to operate more efficiently while maintaining adequate link margin for reliable communication
3Reliability
If conventional waveform design is used, then the system implementation is straightforward, but the power amplification is inefficient and link margins are inadequate
Solution Approach 1:
The patent specifies concrete parameter values including pulse shaping filter coefficients, roll-off factor of 0.35, and π/2 BPSK modulation. These defined parameter changes provide a balance between improved link margin and manageable implementation complexity, as the parameters are explicitly specified rather than requiring complex adaptive algorithms
Solution Approach 2:
The patent incorporates joint sequence detection and soft decision decoding in the receiver, which use feedback from the detected signal quality to improve detection accuracy. This feedback mechanism enhances link margin performance while maintaining reasonable complexity through algorithmic optimization
4Area of stationary object
If alert messages are transmitted in high-attenuation environments, then coverage is extended, but error rates increase due to signal fading
Solution Approach 1:
The patent applies forward error correction coding and adds redundant information to the alert messages before transmission. This beforehand cushioning provides error protection that compensates for signal fading and attenuation, maintaining low error rates even when extending coverage to high-attenuation areas
Solution Approach 2:
The patent implements soft decision decoding that uses feedback from the received signal quality to make more accurate decoding decisions. This feedback mechanism reduces error rates by utilizing information about signal reliability, enabling successful message reception in extended coverage areas with high attenuation
Data Source
AI summary
An approach is provided for high penetration alerting in a mobile satellite system. A message is generated for transmission to a wireless terminal. The message is partitioned into a number of symbols, each symbol composed of a portion of the message. The symbols are encoded via FEC coding to generate outer coded symbols, and each outer coded symbol is encoded based on a corresponding binary orthogonal sequence. The inner coded symbols are modulated based on a binary modulation scheme, and pulse shaped to generate message bursts for transmission to the wireless terminal. Each message burst reflects a group of the inner coded symbols, wherein the grouping of the inner coded symbols facilitates joint sequence detection by the wireless terminal, and each message burst exhibits relatively low peak-to-average power ratio.