DCI — Downlink control information — the assignment itself

5G Systems Notes · Concept map · DCI Route · Hierarchy · Index · All concepts · Hub

Procedures over time

Where it sits

Sits atLevel 9 of the hierarchy · Procedures over time · explained
Learn firstRNTI · PDCCH — 18 concepts in the full chain, see the paths
UnlocksScheduling · PDSCH
Primary clauseTS 38.212 §7.3
Used innr-pdsch 33 · ref-channels 2 · ref-modulation 2 · 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

Downlink control information is the message that schedules everything. PDSCH carries no information about itself — no header, no length, no identifier — so it all arrives first, on PDCCH.

A DCI is Polar-encoded and its CRC is masked with the RNTI of the recipient. There is no address field: a device tries the RNTIs it owns and the one that makes the CRC check out is the answer.

Format 1_0 is the fallback, its size fixed by rule so it can be decoded before configuration exists. Format 1_1 is the working format. Format 1_2 is compressible for low latency.

For a 273-block bandwidth part, a format 1_0 downlink assignment is 44 bits — and more than half of them are about the acknowledgement and retransmission machinery.

Read on

The full treatment is in nr-pdsch — 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 DCI (level 9) you first need 18 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
2 OFDM symbol
3 Cyclic prefix · Resource element · Slot
4 Numerology · Physical layer · Resource block
5 Point A · REG and CCE · Transport block
6 Bandwidth part · CRC
7 CORESET · Polar coding · RNTI
8 PDCCH
Immediately before DCI: PDCCH, RNTI.
Keep going — where this sits on the route
◀Rate matchingstep 92 · level 9
Step 93 of 118level 9 · Procedures over time
AI/ML in the RANstep 94 · level 9▶
Level 9 → 10 · this unlocks
Scheduling · PDSCH level 12
↳ all 6 concepts at level 10 · level 9 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 · DCI Top · Concept map · Hub