Techniques and systems for wireless communications
Techniques, apparatus and systems for providing radio frequency wireless communications based on time reversal of the channel impulse response of an RF pulse in a transmission channel between an RF transmitter and an RF receiver to enhance reception and detection of an RF pulse at the RF receiver against various effects that can adversely affect and complicate the reception and detection of the RF pulse at the RF receiver.
1. A radio frequency (RF) wireless communication system, comprising:
a first wireless transceiver at a first location to transmit and receive wireless RF signals and a second wireless transceiver at a second location separate from the first location to pair with the first wireless transceiver to transmit and receive wireless RF signals in wireless communication with the first wireless transceiver, the first wireless transceiver comprising:
a monitor pulse transmitter to wirelessly transmit periodic monitor RF pulses for monitoring signal degradation in a transmission channel between the first and second wireless transceivers in which a wireless RF signal produced by the first wireless transceiver propagates to the second wireless transceiver; and
a signal receiver that receives wireless RF signals generated by the second wireless transceiver based on information in the periodic monitor RF pulses and is operable to process the received wireless RF signals for extracting data or information in the received wireless RF signals from the second wireless transceiver; and
the second wireless transceiver comprising:
a monitor pulse receiver to receive and detect the monitor RF pulses from the first wireless transceiver to obtain specific signal degradation information in the transmission channel;
a signal transmitter that transmits wireless RF signals comprising RF pulses carrying data or information to be transmitted to the first wireless transceiver, the signal transmitter operable to generate the wireless RF signals to the first wireless transceiver based on information in the monitor RF pulses received by the monitor pulse receiver; and
a transmission control circuit that processes one or more received monitor RF pulses from the first wireless transceiver to produce a time reversal of an impulse function of the one or more received monitor RF pulses, and multiplexes each RF pulse carrying data or information to be transmitted with the time reversed impulse function as part of each wireless RF signal to be transmitted out by the signal transmitter to reduce the signal degradation at the first location after a wireless RF signal from the second wireless transceiver reaches the first wireless transceiver via the transmission channel, wherein the transmission control circuit stores an impulse function of the one or more received monitor RF pulses, compares an impulse function of one or more most recently received monitor RF pulses with the stored impulse function to determine a difference, and operates to select one of the stored impulse function and the impulse function of one or more most recently received monitor RF pulses for the multiplexing based on whether the difference is greater or less than a first threshold.
2. The system as in claim 1 , wherein:
the transmission control circuit sends to the first wireless transceiver a command to change a time period between two sequential monitor RF pulses produced by the monitor pulse transmitter based on the difference between the impulse function of one or more most recently received monitor RF pulses and the stored impulse function.
3. The system as in claim 2 , wherein:
the transmission control circuit sends a command to increase the time between two sequential monitor RF pulses produced by the monitor pulse transmitter when the difference is below the first threshold and to decrease the time between two sequential monitor RF pulses produced by the monitor pulse transmitter when the difference is above the first threshold.
4. The system as in claim 1 , wherein:
the signal receiver of the first wireless transceiver at the first location is configured to monitor a parameter indicative of reception performance, and the monitor pulse transmitter of the first wireless transceiver at the first location is configured to change how often sequential monitor RF pulses are emitted based on whether the parameter indicative of reception performance is greater or less than a second threshold.
5. The system as in claim 4 , wherein the parameter indicative of reception performance measured at the signal receiver of the first wireless transceiver is a bit-error-rate or an eye diagram.
6. The system as in claim 5 , wherein:
the monitor pulse transmitter of the first wireless transceiver at the first location is configured to increase a time period between two sequential monitor RF pulses when the parameter indicative of reception performance is below the second threshold and to decrease the time period between two sequential monitor RF pulses when the parameter indicative of reception performance is above the threshold.
7. A system for providing radio frequency (RF) communications comprising:
a target comprising:
a target-transmitter to repeatedly emit RF impulse-pulses; and
a target-receiver to detect RF data signals;
a base in communication with the target, the base comprising:
a base-detector configured to detect a channel impulse response of the RF impulse-pulses emitted by the target, wherein the base-detector comprises an analog-to-digital converter to digitize the detected channel impulse response into a detected channel impulse response waveform;
a waveform processing unit comprising:
a temporary memory configured to store the detected channel impulse response waveform;
a first memory configured to store and reverse in time domain a previously detected channel impulse response waveform;
a comparator unit to obtain a difference between the channel impulse response waveform in the temporary memory and the channel impulse response waveform in the first memory; and
a switch coupled to the temporary memory, the first memory and the comparator unit to control replacing the channel impulse response waveform stored in the first memory with the channel impulse response waveform stored in the temporary memory, the replacing based on a comparison of the obtained difference from the comparator unit against a predefined threshold;
a multiplexer that adds a copy of the time reversed channel impulse response waveform from the first memory at each bit of an RF data stream to produce an output signal; and
a transmitter to emit the output signal.
8. The system as in claim 7 , wherein operation modes of the first memory comprise first-in-first-out and last-in-last-out.
9. The system as in claim 7 , wherein
the first memory is a buffer, wherein operation modes of the buffer comprise first-in-first-out and last-in-last-out.
10. The system as in claim 7 , wherein
an operation mode of the temporary memory comprises first-in-first-out.
11. The system as in claim 10 , wherein
an operation mode of the temporary memory comprises last-in-last-out.
12. The system as in claim 7 , wherein
the temporary memory is a temporary buffer, wherein operation modes of the temporary buffer comprise first-in-first-out and last-in-last-out.
13. The system as in claim 7 , wherein the multiplexer comprises one of digital circuitry or analog circuitry.