Interference Canceler for Bidirectional HFC Signal Equalization
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Solution Overview
Problem
Conventional digital transmission systems face significant challenges with multipath linear distortion, inter-symbol interference, and high costs in amplification due to the need for complex and power-hungry equalization techniques, particularly in hybrid fiber coaxial (HFC) networks, where echoes and reflections cause signal distortion and require costly cyclic prefix usage.
Innovation Solution
An interference canceling subsystem is introduced for bidirectional communications networks, utilizing a simplified architecture that includes an interference canceler capable of removing transmitted signals from received signals in both optical and wireless channels without the need for cyclic prefixes, enabling efficient signal equalization and amplification across various transmission modes, including Time Division Duplex (TDD) and Frequency Division Duplex (FDD).
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional equalization techniques are used to eliminate multipath distortion and inter-symbol interference, then signal quality is improved, but system complexity and power consumption increase significantly
Solution Approach 1:
The patent extracts and removes the transmitted signal component from the received signal to eliminate multipath distortion and inter-symbol interference. By separating the desired signal from the interfering echoes and reflections, the system achieves signal equalization without requiring complex conventional equalization algorithms, thus improving signal quality while reducing system complexity
Solution Approach 2:
The patent creates a copy of the transmitted signal and uses it to generate an estimate of the multipath distortion. This copied signal is then subtracted from the received signal to remove the distortion, providing a simpler alternative to complex equalization techniques while maintaining signal quality
2Reliability
If cyclic prefix is used to combat inter-symbol interference, then signal reliability is improved, but transmission efficiency and bandwidth utilization deteriorate
Solution Approach 1:
Instead of adding a cyclic prefix to protect against inter-symbol interference, the patent extracts and removes the interfering components from the received signal. This approach maintains transmission efficiency by not wasting bandwidth on redundant prefix symbols while still achieving signal reliability through active interference removal
Solution Approach 2:
The patent converts the harmful effect of multipath distortion into a beneficial process by using the known transmitted signal to predict and remove the distortion. The same multipath channels that cause interference are exploited to generate accurate estimates of the distortion for removal, improving transmission efficiency while maintaining signal reliability
3Reliability
If complex equalization algorithms are implemented to remove echoes and reflections, then signal quality is improved, but energy consumption increases
Solution Approach 1:
The patent uses a simple copying approach where the transmitted signal is replicated and processed to generate distortion estimates. This copying method requires minimal computational resources compared to complex equalization algorithms, thereby reducing power consumption while maintaining signal quality through effective echo and reflection removal
Solution Approach 2:
The system performs self-service equalization by using its own transmitted signal to generate the distortion estimates needed for cancellation. This self-contained approach eliminates the need for complex external equalization processing, reducing computational complexity and power consumption while maintaining signal quality
4Productivity
If bidirectional amplification is implemented in HFC networks, then network capacity is improved, but signal interference from opposite direction increases
Solution Approach 1:
The patent extracts and removes the transmitted signal from the received signal in bidirectional amplification systems. By separating the desired signal from the interfering signal traveling in the opposite direction, the system achieves network capacity improvement through full-duplex operation while eliminating harmful interference through active cancellation
Solution Approach 2:
The patent introduces an interference cancellation mechanism that acts as an intermediary between the bidirectional signals. This intermediary process generates and subtracts estimates of the opposite-direction signals, allowing high network capacity through bidirectional amplification while removing the harmful interference that would otherwise limit system performance
Data Source
AI summary
An interference canceling subsystem for a bidirectional communications network includes an input interface configured to receive a first data signal from a first transceiver of the network, an output portion configured to receive a second data signal from a second transceiver of the network, a first signal path connecting the input interface to the output portion, a second signal path connecting the output portion to the input interface, and a first interference canceler disposed between the output portion and the input interface along the second signal path. The first signal path is configured to relay the first data signal from the input interface to the output portion. The interference canceler is configured to (i) relay the second data signal from the output portion to the input interface, and (ii) remove portions of the first data signal from the relayed second data signal prior to reaching the input interface.