The concept map — what this folder must explain

The three states, and what they mean for a reader.

explained — there is a section of its own, in a note that exists, and the link in the table goes straight to it. You can follow it and come back.

partial — it is used and partly explained, but inside another subject's note and from that note's angle only. Good enough to keep reading; not good enough to learn the concept from.

not yet — the notes use it and nothing here defines it. If you hit one of these and are lost, that is the folder's fault, not yours.

There are no not yet entries left, and every concept has a file of its own — true since 26 August 2026, and still true after the core and device layers were added on 28 August 2026, which brought 46 concepts and three themes with their own pages and reference notes. Each row below links to term-<name>.md: the definition, the clause, what must be learned first, what it unlocks, and which notes use it.

The eleven group notes remain as the narrative — they read a group as one argument and link out to the pages. Six on the radio: modulation, the stack, channels, signals, space and system. Five on the rest of the system: the core, sessions, identity, device state and mobility.

That is a floor, not a ceiling. A reference section explains a concept well enough to keep reading; a deep note explains it well enough to work with, the way PDSCH does for the downlink shared channel. The deep notes still to come are on the track page, and when one is written the entry here simply re-points at it.

This page is a map. If you want a road, it is the route.

A map shows the whole shape at once, which is the right thing once you know where you are — but it never says you are here, and it never says now this one. The route takes exactly these concepts, flattens the hierarchy below into one numbered order, and links each entry straight at its own page. Every concept's page then carries its own step number, the two concepts either side of it, and the ones it unlocks a level up, so the walk continues from wherever you happen to be.

Same data, same ordering function — the route is this page's hierarchy read left to right, not a second opinion about it.

What is on this page, in the order it is useful.

Everything here has an address, and the addresses are stable. Link at any of them from a note, from the tracker, or from outside the folder:

The # beside a level, a theme or a term row is that link, ready to copy. Every concept badge in the hierarchy, every entry in the index and every prerequisite in a path is itself a link to the concept's page — nothing on this page is a dead end.

How to read a level. Level 0 needs nothing — those are the places to start. Level 5 means five ideas stacked one on another come first. Nothing on a level depends on anything else on the same level, so a level can be read in any order; but no level before the one above it.

Inside a level, the concepts are split by theme and ordered by how heavily the notes already use them. A level is otherwise a bag of unrelated ideas that happen to be equally deep — level 4 holds a resource block, a modulation scheme and a random-access channel, and reading them as one line teaches nothing. Each level is linkable as terms.md#level-4, and every term page's card links straight at its own level.

The level is the longest chain, not the count. PDSCH is level 12 and has 30 prerequisites in total — 12 is how deep the deepest strand goes, 30 is how many concepts it touches.

The graph is checked, not trusted. The widget reports a cycle, a prerequisite naming a term that does not exist, a term with no needs list at all, and — the pedagogical one — a concept better explained than something it depends on, which is a hole a reader would fall into while following the chain downwards.

What the widget checks on every page load, and reports in red if it fails:

1. A term marked explained or partial must give a where of the form file.md#anchor — and that file must exist and really carry that anchor. Rename a section and the map says so.
2. A term marked not yet must not give a location.
3. Every term in terms.json must be mentioned by at least one note. A term nothing uses is either a mistake or a concept the folder has quietly dropped.
4. The reverse direction too: any acronym the notes use three or more times that is not in terms.json is listed as a candidate. The registry cannot fall behind the writing, because the writing reports itself.

When a note starts using a new idea, add it to terms.json in the same pass — name, full, group, state, spec, why, and note if it deserves a file of its own. Then declare its other names, and mind which of the three keys they belong in: aka for another spelling of the same idea (hybrid ARQ for HARQ), covers for the named members it enumerates (QPSK and 256QAM are two of the six modulations, not two ways of writing the word), and scan for a word that merely proves the idea is in play. All three count as a mention; aka and covers are printed on the concept's card and listed in the index, under labels that say which they are.

When a concept finally gets its section, change state to explained and set where to the anchor. The link on this page starts working; the backlog gets shorter by one.

When the candidate list shows something that is not a concept — a surname printed in capitals inside a citation, a node label from a diagram — add it to NOT_CONCEPTS in ../widgets/fiveg_terms.py rather than inventing a term for it.