Point A — The origin all frequency numbering is measured from
The grid and its units
This page is the explanation. point a, live is the working
half — the same quantities computed by 5G Simulation/ while the page loads, so they cannot
drift from what is written here.
Where it sits
What it is
Point A is the origin all frequency numbering is measured from — a single reference point from which common resource block 0 begins.
It matters because 5G numbers frequency in four different ways at once: absolute radio-frequency channel numbers, common resource blocks from point A, physical resource blocks within a bandwidth part, and virtual resource blocks within an allocation. A field in a specification always means exactly one of them.
A device learns where point A is from offsetToPointA in the MIB, which is why PBCH must be decoded before the grid can be addressed at all.
Read on
The full treatment is in nr-frame-structure — this page is the definition and the map reference; that note is where the subject is actually developed.
Before this concept, the hierarchy says to learn the following — the full chain, in order: