Frame format and design of wake-up frame for a wake-up receiver
Methods and systems for providing a low-rate data signal. Received input data bits are Manchester modulated onto successive multicarrier symbols in the time domain. Each multicarrier symbol includes orthogonal sub-carrier and a null sub-carrier. A stored waveform can be retrieved to code the sub-carriers. The successive multicarrier symbols are up-converted to a carrier frequency to provide the low-rate data signal, and the low-rate data signal is transmitted.
1. A method of providing a low-rate data signal, the method comprising:
receiving input data bits;
retrieving a stored multicarrier waveform for a multicarrier symbol, the multicarrier symbol including a null sub-carrier;
Manchester modulating the input data bits onto successive multicarrier symbols in time domain, each multicarrier symbol being encoded as two sub-symbols of equal length, each multicarrier symbol having one sub-symbol encoded and stored with a corresponding half of the multicarrier waveform and one sub-symbol encoded and stored with a zero energy waveform;
up-converting the successive multicarrier symbols to a carrier frequency to provide the low-rate data signal; and
transmitting the low-rate data signal over a wireless channel.
2. The method of claim 1 , wherein the multicarrier waveform is generated using inverse fast Fourier transform (IFFT) and stored in advance, and the multicarrier waveform is retrieved before each transmission.
3. The method of claim 1 further comprising:
generating the multicarrier waveform using inverse fast Fourier transform (IFFT); and
storing the multicarrier waveform.
4. The method of claim 1 wherein the input data bits are mapped using on-off keying (OOK).
5. The method of claim 1 wherein the multicarrier symbol comprises M orthogonal sub-carriers, wherein for each successive multicarrier symbol the corresponding data bit is modulated onto each of M−1 of the orthogonal sub-carriers.
6. The method of claim 5 wherein for each successive multicarrier symbol the corresponding data bit is modulated as “on” and “off” periods of equal duration.
7. The method of claim 5 wherein M equals 16 and the sub-carriers have an inter-carrier spacing (SS) of 312.5 KHz.
8. The method of claim 1 further comprising inserting a guard interval period into each of the successive multicarrier symbols.
9. The method of claim 1 wherein the input data bits are data bits of a wake-up packet and the low-rate data signal is a wake-up signal.
10. The method of claim 9 wherein the wake-up packet comprises a short training field, the short training field comprising a short training sequence enabling detection of the wake-up packet distinct from other signals.
11. A method at a receiver, the method comprising:
receiving a low-rate data signal transmitted over a wireless channel;
down-converting the low-rate data signal to recover successive multicarrier symbols, each multicarrier symbol comprising a set of orthogonal sub-carriers and a null sub-carrier, each multicarrier symbol having been encoded as two sub-symbols of equal length, each multicarrier symbol having one sub-symbol encoded with a corresponding half of a multicarrier waveform and one sub-symbol encoded with a zero energy waveform; and
extracting data bits from each of the multicarrier symbols to recover the data bits of the low-rate data.
12. The method of claim 11 , wherein extracting data bits comprises, for each received multicarrier symbol:
applying an envelope detection operation to the received multicarrier symbol; and
applying a decision threshold to the output of envelope detection operation.
13. The method of claim 11 , wherein extracting data bits comprises, for each received multicarrier symbol:
measuring power distribution of the received multicarrier symbol; and
comparing power distribution between first and second halves of the received multicarrier symbol and determining the corresponding data bit to be a “1” or a “0” based on the comparison.