Filterbank Multi-Carrier Transmission for Coaxial Cable Interference
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Solution Overview
Problem
Modern cable communication networks using orthogonal frequency division multiplexing (OFDM) face inefficiencies due to non-ideal sub-carrier signal orthogonality, leading to inter-carrier interference and inter-symbol interference, which limits data transmission efficiency and requires the use of cyclic prefixes, increasing overhead.
Innovation Solution
The system individually filters symbols of each input data stream before and after transformation between frequency and time domains at the transmitter and receiver, reducing out-of-band emissions and allowing higher modulation orders without the need for cyclic prefixes, enabling frequency domain equalization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If OFDM is used to transmit data over coaxial cable, then data transmission can be achieved, but inter-carrier interference and inter-symbol interference occur due to non-ideal sub-carrier orthogonality, reducing transmission efficiency
Solution Approach 1:
The patent changes the fundamental transmission approach from traditional OFDM to a filterbank-based multi-carrier system. By modifying the spectral characteristics of individual sub-carriers through specific filtering operations, the system achieves better orthogonality and reduced interference while maintaining data transmission capability.
Solution Approach 2:
The patent divides the transmitted signal into multiple filtered sub-carrier components, each processed independently through filtering operations. This segmentation allows individual optimization of each sub-carrier's spectral properties to minimize interference with adjacent carriers while maintaining overall system performance.
2Reliability
If cyclic prefixes are added to mitigate interference in OFDM systems, then signal reliability improves, but transmission overhead increases and data transmission efficiency decreases
Solution Approach 1:
The patent extracts and eliminates the need for cyclic prefixes by fundamentally changing the modulation approach. The filterbank-based system with properly designed spectral filters provides inherent interference mitigation without requiring the additional time-domain padding that cyclic prefixes impose, thus removing this overhead element entirely.
3Productivity
If higher modulation orders are used to increase data rate, then spectrum efficiency improves, but out-of-band emissions increase causing interference to adjacent channels
Solution Approach 1:
The patent changes the spectral confinement parameters of each sub-carrier through sophisticated filtering operations. By carefully designing the filter responses to provide adequate roll-off and spectral containment, the system can employ higher modulation orders without generating excessive out-of-band emissions, thus resolving the trade-off between data rate and spectral cleanliness.
Data Source
AI summary
A method for transmitting data via a coaxial electrical cable includes (a) converting symbols of each input data stream of a plurality of parallel input data streams from digital form to analog form, (b) individually filtering symbols of each input data stream, (c) transforming symbols of each input data stream from a first frequency-domain to a first time-domain, to generate parallel first time-domain samples, (d) converting the first time-domain samples to a serial multi-carrier signal, and (e) injecting the multi-carrier signal onto the coaxial electrical cable.