Ethernet Line Timing for Wireless Base Station Clock Recovery
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Solution Overview
Problem
Conventional wireless telephone systems face challenges in achieving accurate clock signals for base stations, as GPS receivers and free-running oscillators are expensive, and existing Ethernet standards provide clock signal accuracies insufficient for wireless communications, especially with the transition to higher data rates over packet-based Ethernet connections.
Innovation Solution
Implementing line timing in a packet-based communications system where Ethernet signals from central offices to base stations are generated with sufficient accuracy to recover a reference clock for wireless transmissions, using a node with receivers, a clock selector, and transmitters to select and utilize accurate clock signals, eliminating the need for GPS receivers or expensive oscillators.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If GPS receivers or free-running oscillators are deployed at base stations to achieve accurate clock signals, then clock signal accuracy is improved, but system cost increases significantly
Solution Approach 1:
The patent introduces Ethernet facilities as an intermediary medium to transmit timing signals from central offices to base stations. Instead of equipping each base station with expensive GPS receivers or oscillators, the timing signal is conveyed through the existing Ethernet infrastructure, which acts as a mediator to deliver accurate clock signals at lower cost.
Solution Approach 2:
The patent creates a copied version of the accurate clock signal by recovering it from Ethernet transmissions. Rather than generating original accurate clock signals at each base station using expensive hardware, the system copies the timing information from central office transmissions embedded in Ethernet packets, achieving the same functional result more economically.
2Productivity
If conventional Ethernet facilities are used between base stations and central offices, then data transmission capability is improved, but clock signal accuracy deteriorates to levels insufficient for wireless communications
Solution Approach 1:
The patent applies preliminary action by embedding timing information in advance within the Ethernet transmissions from central offices. The clock signal is pre-prepared and incorporated into the data transmissions, so that base stations can recover accurate timing without requiring separate dedicated timing channels or modifying the Ethernet protocol structure.
Solution Approach 2:
The patent makes the Ethernet facility multi-functional by using it simultaneously for both data transmission and clock signal distribution. The same Ethernet infrastructure that carries wireless backhaul traffic also conveys timing information, eliminating the need for separate dedicated timing channels and achieving dual purposes with a single system.
Data Source
AI summary
In a packet-based (e.g., Ethernet) network, such as the network of central offices and base stations of a wireless telephone system, a node receives one or more incoming packet-based signals from one or more other nodes of the network and recovers a clock signal from each incoming packet-based signal. The node selects one of the recovered clock signals as the node's reference clock signal. When the node is part of a base station, the node uses the selected clock to generate and transmit one or more outgoing packet-based signals to one or more central offices. The node also uses the selected clock to generate the base station's wireless transmissions. In one implementation, the base stations and central offices are connected by Ethernet facilities.