Method, system, and apparatus for wireless power transmission based on power waveforming

1. An apparatus for wireless power transmission, comprising:

at least one antenna configured for receiving at least one wireless signal from a receiver, via a multipath channel between the apparatus and the receiver; and

at least one processor configured for

estimating at least one channel state information (CSI) of the multipath channel based on the at least one wireless signal,

determining a power transmission waveform based on the at least one CSI, and

calculating a power transfer signal based on the power transmission waveform and a reference signal,

wherein the at least one antenna is further configured for wirelessly transmitting the power transfer signal to the receiver,

wherein determining the power transmission waveform comprises jointly designing the power transmission waveform and the reference signal to maximize an efficiency gain that is a ratio between a total harvested energy at the receiver and a total energy expenditure at the apparatus,

wherein jointly designing the power transmission waveform and the reference signal comprises:

initiating an iteration number,

optimizing, based on an initial version of the reference signal or a previous version of the reference signal from previous iteration, the power transmission waveform to maximize the efficiency gain and generate a current version of the power transmission waveform of current iteration,

optimizing, based on the current version of the power transmission waveform of current iteration, the reference signal to maximize the efficiency gain and generate a current version of the reference signal of current iteration,

increasing the iteration number by one, and

repeating the steps of optimizing the power transmission waveform, optimizing the reference signal and increasing the iteration number, until at least one of the following: the iteration number exceeds a first threshold, a difference between the current version of the reference signal of current iteration and the previous version of the reference signal from previous iteration is smaller than a second threshold, and a difference between the current version of the power transmission waveform of current iteration and a previous version of the power transmission waveform from previous iteration is smaller than a third threshold.

2. The apparatus of claim 1 , further comprising:

a digital-to-analog converter configured for converting the power transfer signal having a digital format to an analog power transfer signal; and

an amplifier configured for amplifying the analog power transfer signal to generate an amplified analog power transfer signal, wherein the at least one antenna is configured for wirelessly transmitting the amplified analog power transfer signal to the receiver.

3. The apparatus of claim 1 , wherein determining the power transmission waveform comprises designing the power transmission waveform to maximize an efficiency of energy delivery from the apparatus to the receiver.

4. The apparatus of claim 1 , wherein the initial version of the reference signal is a single-tone signal that has a power spectrum condensed into a single frequency tone that has a largest value of summation of channel power over all transmit antennas on the apparatus.

5. The apparatus of claim 1 , wherein jointly designing the power transmission waveform and the reference signal comprises:

designing the power transmission waveform to be a single-tone waveform regardless of the designing of the reference signal, when the reference signal is periodic and a first length of the power transmission waveform is a multiple of a second length of the reference signal; and

designing the reference signal to be a single-tone signal that has a power spectrum condensed into a single frequency tone that has a largest value of summation of channel power over all transmit antennas on the apparatus, regardless of the designing of the power transmission waveform, when the reference signal is periodic and the second length of the reference signal is larger than or equal to a third length of the multipath channel.

6. The apparatus of claim 1 , wherein the at least one processor is further configured for adjusting at least one of the following parameters: a quantity of transmit antennas on the apparatus for wirelessly transmitting power transfer signals, a quantity of multipaths of the multipath channel, a length of the power transmission waveform, and a length of the reference signal, based on at least one of:

a first relationship between an upper bound of an outage probability and the at least one parameter, wherein the outage probability is a probability that harvested energy at the receiver is smaller than or equal to a predetermined threshold; and

a second relationship between a lower bound of an efficiency gain and the at least one parameter, wherein the efficiency gain is a ratio between a total harvested energy at the receiver and a total energy expenditure at the apparatus.

7. The apparatus of claim 1 , wherein:

the at least one antenna is further configured for receiving a feedback signal from the receiver;

the at least one processor is further configured for

detecting a change of the multipath channel based on the feedback signal;

estimating updated at least one CSI of the multipath channel upon detecting the change of the multipath channel,

updating at least one of the power transmission waveform and the reference signal based on the updated at least one CSI, and

re-calculating the power transfer signal to generate an updated power transfer signal; and

the at least one antenna is further configured for wirelessly transmitting the updated power transfer signal to the receiver.

8. The apparatus of claim 1 , wherein:

the at least one antenna is further configured for receiving a feedback signal from the receiver;

the at least one processor is further configured for

determining that harvested energy at the receiver is smaller than or equal to a predetermined threshold based on the feedback signal;

updating at least one of: a first length of the power transmission waveform, a second length of the reference signal, a third length of the multipath channel, and a quantity of transmit antennas, and

re-calculating the power transfer signal to generate an updated power transfer signal; and

one or more of the at least one antenna, according to the quantity of transmit antennas, is further configured for wirelessly transmitting the updated power transfer signal to the receiver.

9. The apparatus of claim 1 , wherein:

the at least one processor is further configured for

determining a first narrow band power transmission waveform having a first frequency that is selected based on at least one characteristic associated with wireless power transmission to the receiver, the first frequency being within a first frequency range,

determining a second narrow band power transmission waveform having a second frequency that is selected based on the at least one characteristic, the second frequency being within a second frequency range that does not overlap the first frequency range,

determining a composite narrow band power transmission waveform based on a combination of the first and second narrow band power transmission waveforms, and

calculating a composite narrow band power transfer signal based on the composite narrow band power transmission waveform; and

the at least one antenna is further configured for wirelessly transmitting the composite narrow band power transfer signal to the receiver.

10. The apparatus of claim 1 , wherein:

the power transmission waveform is a narrowband frequency tone waveform;

the at least one antenna includes at least one of: an omni-directional antenna and a dipole antenna;

the at least one wireless signal has an auto-correlation function that is a delta function;

the at least one CSI includes at least one of: a channel impulse response (CIR) of the multipath channel and a channel frequency response (CFR) of the multipath channel; and

the at least one wireless signal includes at least one of: a wireless signal having a center frequency between 2 GHz and 3 GHz and a wireless signal having a center frequency between 5 GHz and 7 GHz.

11. An apparatus for wireless power transmission, comprising:

at least one antenna configured for receiving at least one wireless signal from a receiver, via a multipath channel between the apparatus and the receiver; and

at least one processor configured for

estimating at least one channel state information (CSI) of the multipath channel based on the at least one wireless signal,

determining a power transmission waveform based on the at least one CSI, and

calculating a power transfer signal based on the power transmission waveform and a reference signal,

wherein the at least one antenna is further configured for wirelessly transmitting the power transfer signal to the receiver,

wherein determining the power transmission waveform comprises jointly designing the power transmission waveform and the reference signal to maximize an efficiency gain that is a ratio between a total harvested energy at the receiver and a total energy expenditure at the apparatus,

wherein jointly designing the power transmission waveform and the reference signal comprises:

designing the power transmission waveform to be a single-tone waveform regardless of the designing of the reference signal, when the reference signal is periodic and a first length of the power transmission waveform is a multiple of a second length of the reference signal, and

designing the reference signal to be a single-tone signal that has a power spectrum condensed into a single frequency tone that has a largest value of summation of channel power over all transmit antennas on the apparatus, regardless of the designing of the power transmission waveform, when the reference signal is periodic and the second length of the reference signal is larger than or equal to a third length of the multipath channel.

12. The apparatus of claim 11 , further comprising:

a digital-to-analog converter configured for converting the power transfer signal having a digital format to an analog power transfer signal; and

an amplifier configured for amplifying the analog power transfer signal to generate an amplified analog power transfer signal, wherein the at least one antenna is configured for wirelessly transmitting the amplified analog power transfer signal to the receiver.

13. The apparatus of claim 11 , wherein determining the power transmission waveform comprises designing the power transmission waveform to maximize an efficiency of energy delivery from the apparatus to the receiver.

14. The apparatus of claim 11 , wherein the initial version of the reference signal is a single-tone signal that has a power spectrum condensed into a single frequency tone that has a largest value of summation of channel power over all transmit antennas on the apparatus.

15. The apparatus of claim 11 , wherein:

the at least one antenna is further configured for receiving a feedback signal from the receiver;

the at least one processor is further configured for

detecting a change of the multipath channel based on the feedback signal;

estimating updated at least one CSI of the multipath channel upon detecting the change of the multipath channel,

updating at least one of the power transmission waveform and the reference signal based on the updated at least one CSI, and

re-calculating the power transfer signal to generate an updated power transfer signal; and

the at least one antenna is further configured for wirelessly transmitting the updated power transfer signal to the receiver.

16. The apparatus of claim 11 , wherein:

the at least one antenna is further configured for receiving a feedback signal from the receiver;

the at least one processor is further configured for

determining that harvested energy at the receiver is smaller than or equal to a predetermined threshold based on the feedback signal;

updating at least one of: a first length of the power transmission waveform, a second length of the reference signal, a third length of the multipath channel, and a quantity of transmit antennas, and

re-calculating the power transfer signal to generate an updated power transfer signal; and

one or more of the at least one antenna, according to the quantity of transmit antennas, is further configured for wirelessly transmitting the updated power transfer signal to the receiver.

17. The apparatus of claim 11 , wherein:

the at least one processor is further configured for

determining a first narrow band power transmission waveform having a first frequency that is selected based on at least one characteristic associated with wireless power transmission to the receiver, the first frequency being within a first frequency range,

determining a second narrow band power transmission waveform having a second frequency that is selected based on the at least one characteristic, the second frequency being within a second frequency range that does not overlap the first frequency range,

determining a composite narrow band power transmission waveform based on a combination of the first and second narrow band power transmission waveforms, and

calculating a composite narrow band power transfer signal based on the composite narrow band power transmission waveform; and

the at least one antenna is further configured for wirelessly transmitting the composite narrow band power transfer signal to the receiver.

18. An apparatus for wireless power transmission, comprising:

at least one antenna configured for receiving at least one wireless signal from a receiver, via a multipath channel between the apparatus and the receiver; and

at least one processor configured for

estimating at least one channel state information (CSI) of the multipath channel based on the at least one wireless signal,

determining a power transmission waveform based on the at least one CSI, and

calculating a power transfer signal based on the power transmission waveform and a reference signal,

wherein the at least one antenna is further configured for wirelessly transmitting the power transfer signal to the receiver,

wherein the power transmission waveform is a narrowband frequency tone waveform,

wherein the at least one antenna includes at least one of: an omni-directional antenna and a dipole antenna,

wherein the at least one wireless signal has an auto-correlation function that is a delta function,

wherein the at least one CSI includes at least one of: a channel impulse response (CIR) of the multipath channel and a channel frequency response (CFR) of the multipath channel, and

wherein the at least one wireless signal includes at least one of: a wireless signal having a center frequency between 2 GHz and 3 GHz and a wireless signal having a center frequency between 5 GHz and 7 GHz.

19. The apparatus of claim 18 , further comprising:

a digital-to-analog converter configured for converting the power transfer signal having a digital format to an analog power transfer signal; and

an amplifier configured for amplifying the analog power transfer signal to generate an amplified analog power transfer signal, wherein the at least one antenna is configured for wirelessly transmitting the amplified analog power transfer signal to the receiver.

20. The apparatus of claim 18 , wherein determining the power transmission waveform comprises designing the power transmission waveform to maximize an efficiency of energy delivery from the apparatus to the receiver.

21. The apparatus of claim 18 , wherein the initial version of the reference signal is a single-tone signal that has a power spectrum condensed into a single frequency tone that has a largest value of summation of channel power over all transmit antennas on the apparatus.

22. The apparatus of claim 18 , wherein the at least one processor is further configured for adjusting at least one of the following parameters: a quantity of transmit antennas on the apparatus for wirelessly transmitting power transfer signals, a quantity of multipaths of the multipath channel, a length of the power transmission waveform, and a length of the reference signal, based on at least one of:

a first relationship between an upper bound of an outage probability and the at least one parameter, wherein the outage probability is a probability that harvested energy at the receiver is smaller than or equal to a predetermined threshold; and

a second relationship between a lower bound of an efficiency gain and the at least one parameter, wherein the efficiency gain is a ratio between a total harvested energy at the receiver and a total energy expenditure at the apparatus.

23. The apparatus of claim 18 , wherein:

the at least one processor is further configured for

determining a first narrow band power transmission waveform having a first frequency that is selected based on at least one characteristic associated with wireless power transmission to the receiver, the first frequency being within a first frequency range,

determining a second narrow band power transmission waveform having a second frequency that is selected based on the at least one characteristic, the second frequency being within a second frequency range that does not overlap the first frequency range,

determining a composite narrow band power transmission waveform based on a combination of the first and second narrow band power transmission waveforms, and

calculating a composite narrow band power transfer signal based on the composite narrow band power transmission waveform; and

the at least one antenna is further configured for wirelessly transmitting the composite narrow band power transfer signal to the receiver.