System and method for low-power wireless beacon monitor
Selectively enabling an amplitude processing circuit and a phase processing circuit of a wireless station's polar receiver with respect to reception of a beacon signal. Such systems and methods may include sequentially demodulating symbols of the received beacon signal using at least the phase processing circuit to detect a traffic indication signal value in a data payload portion of the received beacon signal. Upon detecting a condition indicating no data traffic for the wireless station, the phase processing circuit may be turned off. The polar receiver may demodulate symbols of the received beacon signal and upon detecting a beacon preamble symbol sequence, shut off the amplitude processing circuit and set the amplitude to a fixed value. The phase processing circuit in conjunction with the fixed amplitude value may be used to demodulate symbols of the beacon signal.
1. A method comprising:
enabling, at an estimated time of a beacon signaling interval, an amplitude processing circuit, a phase processing circuit, and a medium access control (MAC) coprocessor of a polar receiver of a wireless station;
demodulating symbols of a received beacon signal by processing amplitude values from the amplitude processing circuit and phase values from the phase processing circuit;
responsive to detecting a beacon detection signal, turning off the amplitude processing circuit;
sequentially demodulating additional symbols of the received beacon signal by processing the phase values in combination with a fixed amplitude value;
processing the sequentially demodulated additional symbols using the MAC coprocessor;
detecting a traffic indication signal value in a data payload portion of the received beacon signal; and
turning off the phase processing circuit upon detecting a traffic indication signal value indicating no data traffic for the wireless station.
2. The method of claim 1 , further comprising:
enabling, at the estimated time of the beacon signaling interval, a crystal oscillator with a bias current;
generating, by the crystal oscillator, a timing reference for the polar receiver to process the beacon signal; and
upon detecting a traffic indication signal value indicating a presence of data traffic for the wireless station, increasing the bias current to the crystal oscillator.
3. The method of claim 1 , further comprising:
enabling with a bias current, at the estimated time of the beacon signaling interval, a wideband gain stage of a low noise amplifier (LNA);
amplifying, by the LNA, the received beacon signal; and
upon detecting a traffic indication signal value indicating the presence of traffic data for the wireless station, increasing the bias current to the LNA.
4. The method of claim 1 , wherein the beacon detection signal is one of the group consisting of an automatic gain control adjustment signal and a beacon preamble symbol sequence detection signal.
5. The method of claim 1 ,
wherein shutting off the amplitude processing circuit is performed using the MAC coprocessor, and
wherein shutting off the amplitude processing circuit comprises either turning off a power supply to the amplitude processing circuit or turning off one or more bias currents of the amplitude processing circuit.
6. The method of claim 1 , further comprising inhibiting further AGC adjustment after shutting off the amplitude processing circuit.
7. The method of claim 1 , wherein processing the sequentially demodulated additional symbols using the MAC coprocessor is performed in real-time.
8. The method of claim 1 , further comprising shutting off the coprocessor upon detecting the traffic indication signal value indicating no data traffic for the wireless station.
9. The method of claim 1 , wherein detecting the traffic indication signal value indicating no data traffic for the wireless station comprises one of the group consisting of: (i) detecting a TIM value indicating no unicast traffic for the wireless station, (ii) detecting a TIM value indicating no unicast traffic for the wireless station in combination with a broadcast D value indicating no broadcast traffic, and (iii) detecting a TIM value indicating no unicast traffic for the wireless station in combination with a broadcast D value indicating the presence of broadcast traffic in combination with a broadcast ignore condition.
10. The method of claim 1 , further comprising:
comparing a prior estimated time of the beacon signal interval with an actual time of the beacon signal interval to generate an estimated time adjustment; and
updating the estimated time of the beacon signaling interval using the estimated time adjustment.
11. An apparatus comprising:
a polar receiver of a wireless station, the polar receiver configured to periodically receive beacon signals and configured to:
enable, at an estimated time of a beacon signaling interval, an amplitude processing circuit, a phase processing circuit, and a medium access control (MAC) coprocessor of the polar receiver;
demodulate symbols of a received beacon signal by processing amplitude values from the amplitude processing circuit and phase values from the phase processing circuit;
responsive to detecting a beacon detection signal, turn off the amplitude processing circuit;
sequentially demodulate additional symbols of the received beacon signal by processing the phase values in combination with a fixed amplitude value;
process the sequentially demodulated additional symbols using the MAC coprocessor;
detect a traffic indication signal value in a data payload portion of the received beacon signal; and
turn off the phase processing circuit upon detecting a traffic indication signal value indicating no data traffic for the wireless station.
12. The apparatus of claim 11 , wherein the polar receiver comprises:
an events circuit configured to detect the traffic indication signal value in the data payload portion of the received beacon signal and send the traffic indication signal value to the MAC coprocessor of the polar receiver.