Transmitter Diversity Scheme for Non-Linear CPM Signals
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Solution Overview
Problem
Existing wireless communication systems face challenges in achieving full rate transmit diversity for Continuous Phase Modulation (CPM) signals, especially in non-linear modulation schemes and channels with intersymbol interference, where prior art methods are inadequate or undefined.
Innovation Solution
A full rate transmit diversity scheme is developed, combining novel space-time codes with the Lindskog-Paulraj technique, specifically designed for non-linear CPM signals in inter-symbol interference channels, enhancing spectrum efficiency and link performance without requiring additional RF equipment at the receiver.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If transmit diversity is implemented for CPM signals using prior art methods, then spectral efficiency is improved, but the method is inadequate or undefined for non-linear modulation schemes and channels with intersymbol interference
Solution Approach 1:
The patent transforms the CPM signal into a linear modulation format (QAM or PSK) through preprocessing steps including phase unwrapping and differential decoding, enabling the application of linear transmit diversity techniques like Alamouti coding that were previously inapplicable to non-linear CPM modulation
Solution Approach 2:
The patent introduces an intermediary preprocessing stage between the CPM modulator and the transmit diversity encoder, which converts the non-linear CPM signal into a form suitable for linear diversity processing, thereby bridging the gap between non-linear modulation and linear diversity techniques
2Reliability
If full rate transmit diversity is achieved, then diversity gains are improved, but device complexity increases
Solution Approach 1:
The patent segments the received signal into multiple processing streams corresponding to different transmit antennas, applying separate decoding operations to each stream before combining them, which simplifies the receiver structure while maintaining full diversity performance
Solution Approach 2:
The patent uses copying of the received signal through virtual antenna concepts, where the single receive antenna processes signals that are mathematically separated into multiple virtual streams, avoiding the need for multiple physical receive antennas and reducing hardware complexity
3Productivity
If transmit diversity is applied to CPM signals, then spectral efficiency is improved, but interference impact increases in interference-limited environments
Solution Approach 1:
The patent converts the harmful intersymbol interference inherent in CPM signals into a beneficial structure by exploiting the continuous phase property and using differential encoding, which transforms the interference into predictable phase relationships that can be easily decoded at the receiver
Data Source
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AI summary
A method in a transmitter 110 for transmitting CPM signals to a receiver 120. The transmitter divides bits into first and second sequences; duplicates the sequences into third and fourth sequences. The first and second sequences are mapped into a first layer, and the third fourth sequences are mapped into a second layer. The transmitter time reverses one of the first and second sequences, and one of the third and fourth sequences; and maps1 to 0 and 0 to 1 in one of the time reversed sequence in each layer. The transmitter formats the first and second sequences into a first burst, and the third and fourth sequences into a second burst; and applies differential encoding to the bursts when a modulation index value is a non-integer. The first and second bursts are continuous phase modulated and transmitted as first and second CPM signals through a respective antenna.