Power Saving Mechanisms in IEEE 802.11e protocol
What power saving mechanisms does IEEE 802.11e support?
It supports enhanced Power Save Mode (PSM) and Automatic Power Save Delivery (APSD) for efficient energy use.
What is Automatic Power Save Delivery (APSD)?
APSD allows devices to schedule when they wake up to receive buffered data, reducing power consumption.
How does 802.11e improve over legacy power saving?
By introducing APSD, it reduces the need for frequent wake-ups and polling, enhancing battery life for QoS devices.
What is the role of Traffic Indication Map (TIM) in power saving?
TIM in beacon frames indicates which clients have buffered data waiting at the AP.
Does 802.11e support Power Save Mode (PSM)?
Yes, it supports legacy PSM with enhancements for QoS traffic delivery.
What types of APSD does 802.11e define?
It defines both Scheduled APSD (S-APSD) and Unscheduled APSD (U-APSD).
How does Unscheduled APSD (U-APSD) work?
The client triggers delivery of buffered frames by sending uplink frames, allowing efficient, on-demand data retrieval.
What is Scheduled APSD (S-APSD)?
S-APSD allows devices to wake up at scheduled intervals to receive buffered data, optimizing power use.
How does 802.11e handle multicast/broadcast power saving?
Delivery Traffic Indication Message (DTIM) informs clients of multicast/broadcast frames buffered at the AP.
Does 802.11e require AP support for power saving?
Yes, APs buffer frames and manage delivery timing for sleeping clients.
Can power saving mechanisms affect latency?
Yes, sleeping devices may experience some latency while waking to receive buffered data.
How does QoS interact with power saving in 802.11e?
APSD prioritizes QoS traffic, ensuring timely delivery while minimizing power use.
What kind of devices benefit most from 802.11e power saving?
Mobile and multimedia devices requiring both QoS and extended battery life.
Does 802.11e support power saving in both 2.4 GHz and 5 GHz bands?
Yes, power saving features operate regardless of frequency band.
Can legacy clients use 802.11e power saving features?
Legacy clients use traditional PSM, but not APSD introduced by 802.11e.
How do devices signal their power saving capabilities?
Via capability information elements during association and QoS setup.
What is the impact of power saving on throughput?
Power saving may reduce throughput slightly due to sleep/wake transitions.
Does 802.11e support selective delivery of QoS traffic during power saving?
Yes, APSD can prioritize which frames to deliver upon wake.
How does 802.11e power saving improve battery life?
By reducing the time clients spend awake waiting for data, using efficient delivery scheduling.
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