Waveform design for time-reversal systems

A method of communication between a transmitter and multiple receivers using multi-path signals, the method comprising:

• at the transmitter, iteratively determining downlink waveforms and determining virtual uplink power allocation coefficients to increase a weighted sum-rate under a total power constraint until a predetermined condition is met, the determination of downlink waveforms and the virtual uplink power allocation coefficients being based on virtual uplink signal-to-interference-and-noise ratios (SINRs) that take into account both inter-symbol interference (ISI) and inter-user interference (IUI), wherein the downlink waveforms and virtual uplink power allocation coefficients are selected to reduce a combination of inter-symbol interference and inter-user interference;
• determining downlink power allocation coefficients based on the downlink waveforms and the virtual uplink power allocation coefficients;
• and
• allocating power to the downlink waveforms according to the downlink power allocation coefficients,
• wherein determining downlink power allocation coefficients and allocating power to the downlink waveforms are performed before the downlink waveforms or a signal derived from the downlink waveforms is transmitted from the transmitter to the receivers.

An apparatus comprising:

• a time-reversed response unit to receive channel impulse response signals and generate respectively time-reversed channel impulse response signals;
• and
• a waveform design unit configured to
• determine downlink waveforms for two or more receivers to increase a weighted sum-rate under a total power constraint, the downlink waveforms being determined based on the time-reversed channel impulse response signals and initial virtual uplink power allocation coefficients,
• determine updated virtual uplink power allocation coefficients based on the downlink waveforms,
• determine downlink power allocation coefficients based on the downlink waveforms and the updated virtual uplink power allocation coefficients,
• allocate power to the downlink waveforms according to the downlink power allocation coefficients, and
• generate a downlink signal derived from the downlink waveforms, the downlink power allocation coefficients, and intended data for respective receivers,
• wherein determining downlink power allocation coefficients and allocating power to the downlink waveforms are performed before the downlink waveforms or the downlink signal is transmitted from the apparatus to the receivers.

An apparatus comprising:

• a storage device to store instructions;
• and
• a data processor to execute the instructions to implement a process comprising:
• receiving channel impulse response signals,
• generating time-reversed channel impulse response signals based on the channel impulse response signals,
• determining downlink waveforms for two or more receivers to increase a weighted sum-rate under a total power constraint, the downlink waveforms being determined based on the time-reversed channel impulse response signals and initial virtual uplink power allocation coefficients,
• determining updated virtual uplink power allocation coefficients based on the downlink waveforms,
• determining downlink power allocation coefficients based on the downlink waveforms and the updated virtual uplink power allocation coefficients,
• allocating power to the downlink waveforms according to the downlink power allocation coefficients, and
• generating a downlink signal derived from the downlink waveforms, the downlink power allocation coefficients, and intended data for respective receivers,
• wherein determining downlink power allocation coefficients and allocating power to the downlink waveforms are performed before the downlink waveforms or the downlink signal is transmitted to the receivers.

A non-transitory machine-readable medium storing instructions that when read by a machine causes the machine to perform operations comprising:

• receiving channel impulse response signals derived from impulse signals sent from two or more receivers, each impulse signal being sent from one of the receivers to a transmitter through multiple propagation paths;
• determining downlink waveforms for the two or more receivers to increase a weighted sum-rate under a total power constraint, the downlink waveforms being determined based on the time-reversed channel impulse response signals and initial virtual uplink power allocation coefficients;
• determining updated virtual uplink power allocation coefficients based on the downlink waveforms;
• determining downlink power allocation coefficients based on the downlink waveforms and the updated virtual uplink power allocation coefficients;
• and
• allocating power to the downlink waveforms according to the downlink power allocation coefficients,
• wherein determining downlink power allocation coefficients and allocating power to the downlink waveforms are performed before the downlink waveforms or a signal derived from the downlink waveforms is transmitted to the receivers.

A method comprising:

• at a transmitter having multiple transmit antennas, receiving channel impulse response signals derived from impulse signals sent from two or more receivers, each impulse signal being sent from one of the receivers to the transmitter through multiple propagation paths;
• determining virtual uplink waveforms based on initial virtual uplink power allocation coefficients and initial downlink waveforms;
• determining updated virtual uplink power allocation coefficients based on the virtual uplink waveforms, the initial downlink waveforms, and initial downlink power allocation coefficients;
• determining updated downlink waveforms based on the virtual uplink waveforms and the updated virtual uplink power allocation coefficients;
• determining updated downlink power allocation coefficients based on the updated downlink waveforms, the virtual uplink waveforms, and the updated virtual uplink power allocation coefficients, and
• allocating power to the updated downlink waveforms according to the updated downlink power allocation coefficients,
• wherein determining updated downlink power allocation coefficients and allocating power to the downlink waveforms are performed before the updated downlink waveforms or a signal derived from the updated downlink waveforms is transmitted to the receivers.

A method of communication between a transmitter and multiple receivers using multi-path signals, the transmitter having multiple transmit antennas, each receiver having multiple receive antennas, the method comprising:

• at the transmitter, receiving channel impulse response signals derived from impulse signals sent from two or more receivers, each impulse signal being sent from one of the receivers to a transmitter through multiple propagation paths,
• iteratively determining virtual uplink waveforms, determining virtual uplink power allocation coefficients, determining downlink waveforms, and determining downlink power allocation coefficients until a predetermined condition is met,
• wherein the virtual uplink waveforms, the virtual uplink power allocation coefficients, the downlink waveforms, and the downlink power allocation coefficients are selected to reduce a combination of inter-symbol interference and inter-user interference;
• allocating power to the downlink waveforms according to the downlink power allocation coefficients;
• and
• transmitting, from the multiple transmit antennas to the multiple receive antennas of the multiple receivers, downlink signals each derived from a combination of the downlink waveforms, each downlink signal being transmitted from a respective transmit antenna to each of the receive antennas through multiple propagation paths,
• wherein determining downlink power allocation coefficients and allocating power to the downlink waveforms are performed before transmitting the downlink signals.

An apparatus comprising:

• multiple transmit antennas;
• a time-reversed response unit to receive channel impulse response signals and generate respectively time-reversed channel impulse response signals;
• and
• a waveform design unit configured to
• determine virtual uplink waveforms based on initial virtual uplink power allocation coefficients and initial downlink waveforms;
• determine updated virtual uplink power allocation coefficients based on the virtual uplink waveforms, the initial downlink waveforms, and initial downlink power allocation coefficients;
• determine updated downlink waveforms based on the virtual uplink waveforms and the updated virtual uplink power allocation coefficients;
• determine updated downlink power allocation coefficients based on the updated downlink waveforms, the virtual uplink waveforms, and the updated virtual uplink power allocation coefficients, and
• allocate power to the downlink waveforms according to the updated downlink power allocation coefficients,
• wherein determining updated downlink power allocation coefficients and allocating power to the downlink waveforms are performed before the downlink waveforms or a signal derived from the downlink waveforms is transmitted from the apparatus.

An apparatus comprising:

• a storage device to store instructions;
• and
• a data processor to execute the instructions to implement a process comprising:
• receiving channel impulse response signals derived from impulse signals sent from two or more receivers, each impulse signal being sent from one of the receivers to the transmitter through multiple propagation paths;
• determining virtual uplink waveforms based on initial virtual uplink power allocation coefficients and initial downlink waveforms;
• determining updated virtual uplink power allocation coefficients based on the virtual uplink waveforms, the initial downlink waveforms, and initial downlink power allocation coefficients;
• determining updated downlink waveforms based on the virtual uplink waveforms and the updated virtual uplink power allocation coefficients;
• determining updated downlink power allocation coefficients based on the updated downlink waveforms, the virtual uplink waveforms, and the updated virtual uplink power allocation coefficients;
• and
• allocating power to the downlink waveforms according to the updated downlink power allocation coefficients,
• wherein determining updated downlink power allocation coefficients and allocating power to the downlink waveforms are performed before the downlink waveforms or a signal derived from the downlink waveforms is transmitted to the receivers.

A non-transitory machine-readable medium storing instructions that when read by a machine causes the machine to perform operations comprising:

• receiving channel impulse response signals derived from impulse signals sent from two or more receivers, each impulse signal being sent from one of the receivers to the transmitter through multiple propagation paths;
• determining virtual uplink waveforms based on initial virtual uplink power allocation coefficients and initial downlink waveforms;
• determining updated virtual uplink power allocation coefficients based on the virtual uplink waveforms, the initial downlink waveforms, and initial downlink power allocation coefficients;
• determining updated downlink waveforms based on the virtual uplink waveforms and the updated virtual uplink power allocation coefficients;
• determining updated downlink power allocation coefficients based on the updated downlink waveforms, the virtual uplink waveforms, and the updated virtual uplink power allocation coefficients;
• and
• allocating power to the downlink waveforms according to the updated downlink power allocation coefficients,
• wherein determining updated downlink power allocation coefficients and allocating power to the downlink waveforms are performed before the downlink waveforms or a signal derived from the downlink waveforms is transmitted to the receivers.