OFDM symbol — One time step of the grid, plus its cyclic prefix

5G Systems Notes · Concept map · OFDM symbol Route · Live ↗ · Hierarchy · Index · All concepts · Hub

The grid and its units

This page is the explanation. ofdm symbol, 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

Sits atLevel 2 of the hierarchy · The grid and its units · explained
Learn firstOFDM — 2 concepts in the full chain, see the paths
UnlocksResource element · Cyclic prefix · Slot · PRACH · PRS · REG and CCE · SS/PBCH block · PUCCH
Primary clauseTS 38.211 §4.3.2, §5.3.1
Used innr-srs 6 · nr-frame-structure 4 · nr-pdsch 4 · index 1
Scanned from the notes at page load and joined with terms.json; nothing on this card is typed by hand.

What it is

An OFDM symbol is one time step of the grid — one useful symbol period plus its cyclic prefix. It is the unit the standard counts time in below the slot.

Its duration halves at every numerology: 71.35 µs at 15 kHz down to 1.11 µs at 960 kHz, computed from the constants of TS 38.211 clause 4.1.

Not every symbol is the same length. The first symbol of every half-subframe carries a longer cyclic prefix, so that an integer number of symbols fits exactly into a subframe.

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.

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Before this concept, the hierarchy says to learn the following — the full chain, in order:

To understand OFDM symbol (level 2) you first need 2 other concepts. Read them in this order — everything on one line can be read in any order, but no line before the one above it:
Level Learn these
0 Subcarrier
1 OFDM
Immediately before OFDM symbol: OFDM.
Keep going — where this sits on the route
◀USIMstep 10 · level 1
Step 11 of 118level 2 · The grid and its units
PAPRstep 12 · level 2▶
Level 2 → 3 · this unlocks
Slot · Cyclic prefix · Resource element · PRACH level 4 · PRS level 4 · SS/PBCH block level 5 · REG and CCE level 5 · PUCCH level 11
↳ all 9 concepts at level 3 · level 2 in full · the whole route
The route is every concept in the folder ordered by level, so nothing here needs anything after it. Computed at page load from terms.json; the same numbering as the route page.
5G Systems Notes · Concept map · OFDM symbol Top · Concept map · Hub