Frequency Shifted Feedback Path for Radio over Fiber Links
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Solution Overview
Problem
The increasing separation distance between base stations and cell towers in next-generation wireless networks introduces additional distortions and impairments in Radio over Fiber (RoF) links, which existing technologies fail to adequately address, especially as the length of these links grows.
Innovation Solution
A system and method incorporating an optical feedback path with a frequency shifter that converts feedback signals to a frequency range less susceptible to impairments, coupled with a pre-distorter and controller to compensate for distortions introduced by RoF links, allowing for improved signal integrity and distortion correction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the separation distance between base station and cell tower is increased, then network virtualization flexibility and flexible cell tower placement are improved, but signal distortion and impairments in RoF links worsen
Solution Approach 1:
The patent changes the frequency parameter of the feedback signal by using a frequency shifter to convert the feedback signal to a different frequency range that is less susceptible to RoF link impairments. This allows the system to maintain signal integrity over longer distances while supporting increased separation between base stations and cell towers.
2Length of moving object
If the length of RoF links is increased, then distance between base station and cell tower is improved, but distortion and impairments in the link worsen
Solution Approach 1:
The patent applies frequency shifting to transform the feedback signal to a frequency range where RoF links exhibit better performance characteristics. This parameter transformation enables the system to extend RoF link lengths while maintaining acceptable signal quality by operating in a more favorable frequency regime.
Solution Approach 2:
The patent implements a feedback mechanism where a portion of the output signal is routed back through the RoF link to the input side. This feedback loop allows the system to monitor and compensate for distortions accumulated over long RoF link distances, enabling extended link lengths while maintaining signal integrity.
3Reliability
If frequency shifting is applied to feedback signal, then susceptibility to RoF link impairments is reduced, but device complexity increases
Solution Approach 1:
The patent introduces a frequency shifter as an intermediary device in the feedback path that converts the feedback signal to a different frequency. This intermediary component simplifies the overall system by enabling the use of standard RoF infrastructure while achieving improved signal quality through frequency transformation, rather than requiring complex specialized equipment.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively enhances signal integrity by reducing impairments in the feedback path, enabling more accurate distortion compensation and maintaining high performance over longer distances without requiring expensive or complex optical components.
Implementation Method 1
The feedback path includes a frequency shifter for shifting the frequency of the feedback signal to a feedback frequency different than the transmission frequency
Implementation Method 2
the optical transmission path converts the RF signal into an optical RF signal which is transmitted via an optical waveguide towards the destination
Implementation Method 3
an optical receiver which converts the RF optical signal into an RF electrical signal
Data Source
AI summary
An aspect of the disclosure provides a system for transmitting a radio frequency (RF) signal from a source to a destination. Such a system includes an RF signal source configured to produce an RF signal at a transmission frequency. The system further includes an optical transmission path for optically transmitting the RF signal towards the destination. The system also includes a feedback path for transmitting a feedback signal received proximate the destination towards the RF signal source. The feedback path includes a frequency shifter for shifting the frequency of the feedback signal to a feedback frequency different than the transmission frequency.