DRX — Discontinuous reception — how a device sleeps
Procedures over time
Where it sits
What it is
What it is. The rules by which a device is allowed to stop listening. TS 38.321 clause 5.7.
The problem. A connected device must monitor PDCCH for a grant that may never come (search space). Monitoring means the receiver is on, and a receiver that is on is the second largest consumer in a handset after the amplifier.
The mechanism is a set of timers. A long cycle and optionally a short one define when the device must be awake; an on-duration timer says how long it listens; an inactivity timer keeps it awake after activity. Outside those windows it may switch the receiver off entirely.
The trade is latency against battery, and it is exactly measurable: a longer cycle saves more
power and adds up to a cycle of delay before a waiting packet can be granted. This is why
RRC_INACTIVE exists as a separate state (ref-stack §6) — it is DRX
taken further, with the connection context preserved so waking is cheap.
Read on
This concept was first written up in ref-system, which reads the whole group as one argument.
Before this concept, the hierarchy says to learn the following — the full chain, in order: