Sparse Code Multiple Access Pulse Shaping for Low Data Rate Transmission
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Solution Overview
Problem
Existing wireless communication technologies face challenges in efficiently transmitting low data rate signals, particularly for machine-type devices, due to high peak-to-average power ratio (PAPR) and resource overloading, which affects signal amplification and power efficiency.
Innovation Solution
The method involves encoding binary data into sparse modulated sequences using sparse code multiple access (SCMA) and performing pulse shaping to create spectrally localized signals with reduced bandwidth, combined with techniques like frequency division multiplexing (FDM) or filter bank multi-carrier (FBMC), and applying transformations such as QAM, π/4 QAM, or offset QAM to reduce PAPR and remove time domain tails.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If traditional encoding techniques are used for low data rate transmission, then data can be transmitted, but the peak-to-average power ratio (PAPR) becomes high which reduces signal amplification efficiency
Solution Approach 1:
The patent changes the encoding parameters by using sparse code multiple access (SCMA) with optimized codebooks that have lower PAPR characteristics. The binary data is encoded to sparse modulated sequences with controlled peak power, transforming the statistical properties of the transmitted signal to improve amplification efficiency while maintaining acceptable complexity through structured codebook designs.
2Loss of energy
If sparse code multiple access (SCMA) is used to reduce PAPR, then signal amplification efficiency improves, but the bandwidth of the transmitted signal increases
Solution Approach 1:
The patent segments the sparse modulated sequence into multiple parts and applies pulse shaping to each segment. This segmentation allows the signal energy to be concentrated in specific frequency regions through tailored pulse shapes, reducing the overall bandwidth occupation while maintaining the low PAPR benefits of SCMA encoding.
Solution Approach 2:
The patent applies different pulse shaping filters to different parts of the signal spectrum, optimizing the spectral distribution locally. This allows the signal to have compact spectral support in critical frequency regions while maintaining the sparse structure needed for low PAPR, effectively managing the bandwidth-power efficiency tradeoff.
3Area of stationary object
If pulse shaping is applied to reduce bandwidth, then spectral efficiency improves, but time domain tails are introduced which require additional processing
Solution Approach 1:
The patent applies preliminary windowing or truncation to the time domain signal before pulse shaping to minimize the extent of time domain tails. This preliminary action reduces the amount of additional processing needed later and allows for more effective pulse shaping with controlled spectral leakage, balancing bandwidth reduction with processing complexity.
Data Source
AI summary
Methods and devices are disclosed for encoding and transmitting data sequences for low data rate applications. An encoded data sequence is transformed and used to shape a multi-carrier pulse to create a narrow-band signal for transmission. Time domain tails of the narrow-band signal may be removed to decrease overhead. The data may be first encoded to create a sparse modulated data sequence. Multi-carrier pulse shaping may be carried out using frequency division multiplexing (FDM) or filter bank multi-carrier (FBMC) techniques. Alternatively, single carrier pulse shaping may be used to create the narrow-band signal.