science

Reverse power feeding

Reverse power feeding is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Reverse power feeding rather than just read about it. In short: Reverse power feeding (RPF) is a technology being standardized by ETSI and the Broadband Forum in 2020. It allows sending power from the customer premises to a distribution point (DP), in order to power the distribution point unit (DPU).

Key takeaways

Reverse power feeding belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Reverse power feeding to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Reverse power feeding from memory before moving on to harder problems.

Reference excerpt

Reverse power feeding (RPF) is a technology being standardized by ETSI and the Broadband Forum in 2020. It allows sending power from the customer premises to a distribution point (DP), in order to power the distribution point unit (DPU). The DPU includes typically a DSL access multiplexer (DSLAM) that can support up to 24 users and an optical network terminator (ONT), which connects the DPU to a central office (CO) where the optical line terminator (OLT) is located. This topology is also known as fiber to the distribution point (FTTdp). RPF is a critical technology for the upgrade of VDSL2 subscribers to the new G.fast standard, which has a maximum range (at high speeds) of 250m. Given that only a small number of subscribers is located at a radius of 250m from a DPU, the number of DPUs required to deploy G.fast infrastructure greatly increases, compared to VDSL2 and older xDSL technologies. RPF reduces installation cost by removing the need to connect the DPU locally to the power grid, as well as the need to monitor its power consumption with a smart meter. Unlike PoE, which defines worst case power losses on a cable that is well defined, RPF defines a maximum safety power envelope, and allows implementations to squeeze as much power as possible from the line. This important difference comes from the fact that PoE was defined with enterprise networks in mind (where the maker of the powered device (PD) needs to interoperate with any power sourcing equipment (PSE)), while RPF is defined for networks that are closed by nature, deployed by a service provider.

References

Worked examples

Example 1 — a first encounter with Reverse power feeding

Start with the simplest possible case. Write down what Reverse power feeding claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Reverse power feeding before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Reverse power feeding ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Reverse power feeding

In research: Reverse power feeding appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Reverse power feeding in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Reverse power feeding is common in secondary-school and first-year university syllabi. It links to neighbouring topics Digital subscriber line, so understanding it makes those chapters shorter.
In everyday life: Look for Reverse power feeding outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Reverse power feeding in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Reverse power feeding means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Reverse power feeding out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Reverse power feeding in simple terms?

Why does Reverse power feeding matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Reverse power feeding?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Reverse power feeding.