802.11 Power Management

With transmit and receive currents on the order of 80-200 mA, it is important to understand which options exist both within and beyond the 802.11 standards to power down the transceiver and extend the battery life.

Active Mode

• Transmitting or receiving function is ON
• Few hours of battery life

802.11 PS-Poll Mode

• Only the Power-Saving mode specified in 802.11
• Transceiver function is DUTY-CYCLED
• Function available during Infrastructure mode network configuration only
• Provides virtual always on power-saving capability
• In PS-Poll mode, the station always maintains a connection to the network
• Station periodically POLLs the airwaves for the presence of Delivery Traffic Indication Management (DTIM) packets sent by the AP in its beacon transmissions
• ~200 mS response latency
• Requires PS-supported Access Point (AP) to buffer the packets
• Few days/weeks of battery life

This example shows the best case (lowest latency) DTIM period (n=1 – i.e. every beacon from the AP has a DTIM message).

• Radio automatically wakes just prior to the DTIM beacon.
• DTIM packet is read.
• Bit position is checked to see if there is buffered data at AP.
• If there is no data, then the radio reverts back to sleep.

In this example, the duty cycle = 4/96. So, the 85 mA active RX current drops to 3.5 mA.

Product-Specific Power Save Modes

Refer to specific product documentation for all supported power modes.

For the ATWINC1500, power modes are described in Section 4.4 of the "ATWINC15x0 Wi-Fi® Network Controller Software Design Guide."