Distributed Digital Antenna System via Fiber Optic Daisy-Chaining
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Solution Overview
Problem
Existing cellular communication systems face challenges in providing coverage in areas where RF signals are blocked, such as tunnels and valleys, due to signal attenuation and high costs associated with installing additional base stations, which limits the feasibility of using coaxial cables and repeaters.
Innovation Solution
A distributed digital antenna system utilizing a host unit that converts RF signals to digital optical signals for transmission over an optical medium to remote units, allowing for daisy-chaining along the fiber optic cable, thereby providing coverage without the need for additional base stations and overcoming attenuation issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If additional base stations are installed to provide coverage in blocked areas, then coverage reliability is improved, but system cost and complexity increase
Solution Approach 1:
The system divides the base station functionality into a central host unit and multiple distributed remote units. Each remote unit is a simplified segment that can be deployed in coverage holes without requiring full base station infrastructure, thus improving coverage reliability while keeping individual units simple and cost-effective.
Solution Approach 2:
The patent introduces remote units as intermediary components between the host unit and mobile devices in coverage blocked areas. These remote units receive digital signals from the host unit via optical fiber and convert them to RF signals locally, providing coverage in blocked areas without requiring full base stations at each location.
2Ease of manufacture
If coaxial cable is used to connect remote antennas, then installation is simplified, but signal attenuation increases with distance
Solution Approach 1:
The patent replaces the electrical coaxial cable transmission system with an optical fiber transmission system. Optical fibers substitute for coaxial cables, providing immunity to signal attenuation over long distances while maintaining ease of installation through daisy-chaining. The optical medium eliminates the energy loss problems inherent in electrical transmission over long distances.
3Length of stationary object
If repeaters are added to overcome attenuation, then signal transmission distance is extended, but system expense and complexity increase
Solution Approach 1:
The patent eliminates the need for repeaters by substituting electrical signal transmission with optical signal transmission through fiber optic cables. Optical signals can travel long distances without regeneration, removing the need for intermediate repeater stations and the associated complexity and expense while extending transmission distance.
4Reliability
If base stations are installed in blocked areas, then coverage holes are filled, but land acquisition and equipment costs increase
Solution Approach 1:
The system segments base station functionality into a centralized host unit and distributed remote units. The remote units are simplified, low-cost devices that can be installed in coverage holes without requiring expensive land acquisition or full base station equipment, thus filling coverage holes cost-effectively while maintaining reliability through digital signal distribution.
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
This solution enables cost-effective and efficient coverage in areas with signal blockages by using fiber optics to connect remote units to a host unit, reducing installation complexity and costs, while maintaining reliable communication.
Implementation Method 1
a host unit for converting radio frequency signals to digital optical signals and digital optical signals to radio frequency signals
Implementation Method 2
The digital optical signals are transmitted over an optical medium to a plurality of remote units
Data Source
AI summary
An optical medium, such as fiber, is tapped to provide an antenna port wherever radio service coverage is desired. Each antenna port is a bi-directional remote unit that receives a digital optical signal from a host unit and transforms the signal to a radio frequency signal for transmission by the remote unit. The remote unit receives radio frequency signals that are converted to digital signals and summed with signals from other remote units and converted to an optical signal for transmission to the host unit.