Wi-Fi Power Save Simulator
A Wi-Fi radio that stays awake drains a battery in hours; one that sleeps well lasts for months. Compare staying awake, legacy power save, U-APSD and Target Wake Time: see when the radio wakes, what it costs in battery life, and how long frames wait.
How it works
A sleeping client (in the doze state) can't receive anything, so the AP holds its frames and announces them in the TIM of each beacon. In legacy power save the client wakes for DTIM beacons and fetches each frame with a PS-Poll. With U-APSD any frame the client sends works as a trigger, and the AP returns everything it holds in one service period. With TWT (Wi-Fi 6) the client and AP agree on wake times, and the client may skip beacons entirely. Broadcast and multicast frames (ARP, mDNS) are held until after the next DTIM beacon, whatever the client does.
4 · All four methods compared
Same device, traffic and settings. Battery life counts only the Wi-Fi radio.
5 · Radio power and battery
Typical figures; your chip's datasheet has the real ones. Times include the wake-up before each beacon or service period.
Definitions
↗ opens a term's full entry in the Wi-Fi Glossary, which explains over 400 Wi-Fi terms with their IEEE 802.11 references.
Notes
- Broadcasts wait for the DTIM. As long as any client is in power save, the AP holds broadcast and multicast frames until just after the next DTIM beacon (IEEE 802.11-2024, 11.2.3). A longer DTIM period saves battery but delays ARP, mDNS and multicast for everyone, including clients that are awake.
- TWT clients may skip beacons. A client with an individual TWT agreement is exempt from receiving beacons but still follows the DTIM rules for group-addressed frames (26.8.2). If it sleeps through DTIMs it misses broadcasts, so networks often answer ARP for it (proxy ARP, 11.21.14) or send multicast to it as unicast (DMS, 11.21.16).
- Real phones mix these methods: many stay awake for a short time after any traffic and use power save only when idle, and some skip DTIM beacons when the screen is off. The model sends each frame as a short exchange at a fixed time and ignores retries and contention.
- Sources: power management and APSD in IEEE 802.11-2024 clause 11.2.3 (PS-Poll 9.3.1.5, EOSP 9.2.4.5.3, TIM 9.4.2.5), TWT in 10.46 and 26.8. Power figures are typical of current phone and IoT Wi-Fi chips and vary widely.