Multi-Band Faster-Than-Nyquist Communication System
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Solution Overview
Problem
Current communication systems face challenges in increasing spectral efficiency and bandwidth utilization without resorting to higher order modulation, which leads to increased non-linearity and complexity due to higher symbol rates and optical impairments.
Innovation Solution
A Multi-Band Faster-than-Nyquist scheme-based communication system that splits symbol datasets into subsets, uses root raised cosine pulse generators with different sub-carriers and time acceleration factors, and employs pre-equalization, frequency shifting, and power scaling to generate a digital multiband signal, along with a receiver that processes signals using MMSE and matched filter-based receivers to reduce inter-symbol interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If higher order modulation formats are used to increase spectral efficiency, then spectral efficiency is improved, but non-linearity induced in the optical fiber increases and implementation complexity increases
Solution Approach 1:
The invention divides the single high-order modulation stream into multiple parallel lower-order modulation streams (e.g., splitting 16QAM into multiple QPSK streams). Each sub-carrier uses simpler modulation, reducing non-linearity and implementation complexity while maintaining overall spectral efficiency through parallel transmission.
Solution Approach 2:
The invention transitions from a single-dimensional high-order modulation approach to a multi-dimensional parallel transmission approach using multiple sub-carriers. By distributing data across multiple dimensions (sub-carriers) with lower-order modulation, the system achieves the same spectral efficiency with reduced complexity and non-linearity.
2Productivity
If symbol rate is increased to increase data rate, then data rate is improved, but bandwidth requirements increase and filtering effects increase
Solution Approach 1:
The invention segments the high symbol rate transmission into multiple parallel lower symbol rate sub-carriers. Each sub-carrier transmits at a lower symbol rate with relaxed bandwidth requirements, while the aggregate data rate is maintained through parallel transmission. This reduces the impact of filtering effects and relaxes bandwidth constraints on individual components.
3Productivity
If symbol rate is increased to increase data rate, then data rate is improved, but receiver processing complexity increases
Solution Approach 1:
The receiver processes each sub-carrier independently at lower symbol rates, dividing the complex high-speed processing task into multiple simpler parallel processing streams. This segmentation reduces the computational burden on timing recovery, polarization de-multiplexing, and equalization algorithms, making receiver processing more manageable.
Solution Approach 2:
The invention applies partial processing to each sub-carrier independently rather than processing the entire high-rate signal at once. By handling each sub-carrier with partial processing (independent equalization, timing recovery), the overall processing complexity is reduced while maintaining data rate throughput.
4Productivity
If higher resolution ADC and DAC are used to reduce implementation loss, then spectral efficiency is improved, but device complexity and cost increase
Solution Approach 1:
The invention segments the high-resolution conversion requirement into multiple lower-resolution conversions across parallel sub-carriers. Each ADC and DAC operates at lower resolution (e.g., 2-4 bits instead of 8+ bits) while the aggregate system maintains spectral efficiency through parallel transmission, significantly reducing converter complexity and cost.
Data Source
AI summary
The disclosed systems and methods are directed to transmitting and receiving symbols. In particular, splitting, a symbol dataset into symbol subsets, modulating, the symbol subsets using different sub-carriers, roll off factors and time acceleration factors, performing frequency shifting and combining the frequency shifted and modulated symbol subsets to generate a digital multiband (DMB) signal, transmitting and receiving the DMB signal, down converting the received DMB signal into a plurality of baseband signals, segregating the plurality of baseband signals in accordance with a manner by which the symbol subsets have been processed before transmission, forwarding a first portion of the plurality of baseband signals to a minimum mean square error (MMSE) based receiver, forwarding a second portion of the plurality of baseband signals to a matched filter-based receiver, and combining the output of the MMSE based receiver and matched filter-based receiver to generate an equivalent symbol dataset.