PoE Power Allocation via Cable Resistance Measurement
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Solution Overview
Problem
In power over Ethernet (PoE) systems, managing power budgets efficiently is challenging, especially in applications where devices are connected using Ethernet cables longer than 100 meters, as existing methods rely on worst-case assumptions that lead to unnecessary power waste and reduced capacity, particularly when using Category 3 cables.
Innovation Solution
A system and method that measure electrical characteristics of Ethernet cables, such as insertion loss and cross-talk, to determine the cable type and length, allowing for accurate power budget allocation based on the specific cable properties, thereby reducing power loss and increasing the capacity of Power Source Equipment (PSE) ports.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If worst-case assumptions are used for power budget allocation, then power delivery reliability is ensured, but power efficiency deteriorates due to unnecessary power waste
Solution Approach 1:
The system dynamically changes the power allocation parameter based on measured cable characteristics. Instead of using a fixed worst-case power budget, the PSE measures insertion loss, cross-talk, and length to determine actual cable type and quality, then adjusts the power allocation parameter accordingly. This resolves the contradiction by making power allocation adaptive to actual conditions rather than static based on worst-case assumptions.
2Adaptability or versatility
If default maximum power allocation is used, then device compatibility is improved, but power budget management efficiency deteriorates
Solution Approach 1:
The power allocation system transitions from a static default maximum power approach to a dynamic adaptive approach. The PSE continuously measures cable characteristics and adjusts power allocation in real-time based on actual cable performance. This maintains device compatibility by ensuring sufficient power is always allocated while improving power budget management efficiency by avoiding unnecessary power reservation.
3Device complexity
If cable type is not identified, then system complexity is reduced, but power allocation precision deteriorates
Solution Approach 1:
The system performs preliminary cable characterization measurements (insertion loss, cross-talk, length) before power allocation. By conducting these measurements in advance during the link establishment phase, the system gathers necessary cable type information without adding complexity to the power allocation process itself. This preliminary action enables precise power allocation while keeping the overall system manageable.
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 approach enables more precise power allocation, reducing power waste and increasing the capacity of PSE ports by accurately assessing power loss based on the type and length of Ethernet cables, particularly benefiting PoE+ and PoE Broad Reach applications by extending cable length and supporting higher-power devices.
Implementation Method 1
said cable detection component measures insertion loss of said Ethernet cable
Implementation Method 2
said cable detection component measures cross talk of said Ethernet cable
Implementation Method 3
a powered device detection component that detects a presence of a powered device, said powered device coupled to a power source equipment port via an Ethernet cable; a cable detection component that measures an electrical characteristic of said Ethernet cable
Data Source
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AI summary
A system and method for discovering a cable type and resistance for Power over Ethernet (PoE) applications. Cabling power loss in PoE applications is related to the resistance of the cable itself. A PHY (110) can be designed to measure electrical characteristics (e.g., insertion loss, cross talk, length, etc.) of the Ethernet cable to enable determination of the cable resistance. The determined resistance can be used in powering decisions and in adjusting power budgets allocated to power source equipment ports (120).