Signalling channel and radio system for power saving in wireless devices
View Patent ↗Wireless devices, transmitters, systems and methods are provided that have a narrow band signalling channel and a wide band channel, for example an OFDM channel. In order to save power, the wireless device is nominally powered down with the exception of a receiver specific to the narrow band signalling channel. Once instructed to do so over the narrow band signalling channel, the wireless device wakes up the rest of its wide band receive circuitry.
1. A wireless device comprising:
a wide band receiver configured to receive a wide band signal; and
a narrow band receiver configured to receive a narrow band signal, and to process the narrow band signal to determine whether or not to wake up the wide band receiver, and to wake up the wide band receiver if so determined;
the wireless comprising a power supply and a switch connecting the power supply to the wide band receiver under control of the narrow band receiver, wherein waking up the wide band receiver comprises controlling the switch to supply power to the wide band receiver,
wherein the wide band signal comprises an OFDM signal with zeros inserted at sub-carrier location(s) where the narrow band signal is to reside.
2. The wireless device of claim 1 wherein the narrow band receiver is a passive device.
3. The wireless device of claim 1 wherein the narrow band receiver is a semi-passive device.
4. The wireless device of claim 1 wherein the wide band receiver is an OFDM receiver.
5. The wireless device of claim 1 wherein processing the narrow band signal to determine whether or not to wake up the wide band receiver comprises demodulating and decoding the narrow band signal and checking if the narrow band signal has a message for this wireless device or not.
6. The wireless device of claim 1 wherein the narrowband receiver wakes itself up on a periodic basis.
7. A transmitter comprising a signal generator configured to generate a signal containing a wide band signal and a narrow band signal, wherein the narrow band signal contains information instructing particular wireless devices to wake up to receive the wide band signal, the transmitter comprising:
a first IFFT function having a plurality of data inputs, and at least one zero input in a frequency location(s) where the narrow band signal is to reside;
a second IFFT function having zero inputs at frequency locations corresponding to the plurality of data inputs, and at least one signalling channel input in the frequency location(s) where the narrow band signal is to reside.
8. A transmitter comprising a signal generator configured to generate a signal containing a wide band signal and a narrow band signal, wherein the narrow band signal contains information instructing particular wireless devices to wake up to receive the wide band signal, the transmitter comprising:
an IFFT function having a plurality of data inputs, and at least one zero input in a frequency location(s) where the narrow band signal is to reside;
a narrow band modulator for generating the narrow band signal operating at a signalling channel frequency where the zeros were inserted.