Faster-Than-Nyquist Transmission for Spectral Efficiency
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Solution Overview
Problem
Current communication systems face challenges in increasing spectral efficiency without increasing modulation order or transmission bandwidth, as higher order modulation and baud rate techniques lead to impairments such as non-linearity, inter-symbol interference, and sensitivity to power imbalance and skew in optical networks.
Innovation Solution
The implementation of Faster-than-Nyquist (FTN) transmission systems, which partition bits into multiple streams, apply different power factors to each stream, and use sequential switching and power scaling to combine them, allowing for increased spectral efficiency by reducing time and frequency spacing between pulses, while mitigating interference through symbol-by-symbol detection and soft-symbol interference cancellation at the receiver.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If higher order modulation is used to increase spectral efficiency, then data rate increases, but non-linearity impairment and sensitivity to power imbalance increase
Solution Approach 1:
The transmitted signal is segmented into multiple independent streams (e.g., X and Y streams) that are multiplexed in the time domain. Each stream is transmitted separately with its own power level, allowing independent optimization and reducing the non-linear interaction between signal components that causes impairment in higher order modulation schemes.
2Productivity
If baud rate is increased to increase data rate, then spectral efficiency improves, but inter-symbol interference and sensitivity to filter impairments increase
Solution Approach 1:
The high data rate is achieved by segmenting the signal into multiple lower baud rate streams transmitted sequentially in time. This segmentation in the time domain allows each stream to be transmitted at a lower baud rate, reducing inter-symbol interference and making the system more tolerant of filter impairments while still achieving high overall data throughput through multiplexing.
3Productivity
If multiple streams with different power factors are transmitted, then spectral efficiency increases, but receiver complexity increases
Solution Approach 1:
The receiver performs preliminary action by sequentially detecting and decoding streams in order of their power factors (from highest to lowest). By detecting the highest power stream first and using its decoded information to cancel interference before detecting lower power streams, the receiver simplifies the detection process for subsequent streams and reduces overall computational complexity compared to joint detection methods.
Data Source
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AI summary
Systems and methods are disclosed that attempt to increase spectral efficiency by using Faster- than-Nyquist (FTN) transmission. In one embodiment, a method at a transmitter includes partitioning bits into K bit streams, obtaining K power scaled symbol streams, combining the K power scaled symbol streams to obtain a stream of transmission symbols, and transmitting the stream of transmission symbols using FTN signaling. At the receiver, the received symbols are partitioned into K symbol streams, and demodulation and decoding is performed by: (i) demodulating and decoding the K th symbol stream of the K symbol streams to obtain a K th set of bits; (ii) mapping the K th set of bits to a K th set of symbols; and (iii) for each one of k = K— 1,...,1: demodulating and decoding a k th symbol stream of the K symbol streams to obtain a k th set of bits. The demodulating and decoding includes performing interference cancellation.