Periodic · Semi-persistent · Aperiodic
All three carry the same quantities (CRI/RI/PMI/CQI/LI, or L1-RSRP). They differ in how they start and where they ride. Click a card.
Periodic (P-CSI)
Configured by RRC, fires at a fixed period with no extra signalling. Rides PUCCH. Cheap heartbeat of channel state.
Semi-persistent
Periodic once activated by MAC-CE (PUCCH) or DCI (PUSCH); deactivated the same way. Periodic without the always-on cost.
Aperiodic (A-CSI)
Summoned by a DCI CSI-request field → a trigger state. One-shot, rides PUSCH. The scheduler's on-demand probe.
DCI bit-field → trigger state
The CSI request field in DCI 0_1 is up to 6 bits. A non-zero codepoint selects one entry of the aperiodic trigger-state list — and that entry bundles the CSI-RS resources to measure and the report config(s) to send. Set the field and watch the chain resolve.
Slot timeline: DCI → CSI-RS → report
Aperiodic CSI is a three-beat sequence across slots: the DCI arrives, the aperiodic CSI-RS is sent after aperiodicTriggeringOffset, the UE measures, and the report lands on the scheduled PUSCH — provided enough processing time (the Z/Z′ requirement) has elapsed. Press play.
CSI processing units
Computing a report costs CPUs for a span of symbols. The UE can only run so many at once (simultaneousCSI-Reports); if triggers overlap and exhaust the budget, lower-priority reports are dropped. Add reports and watch occupancy.