Handshaking protocol for time-reversal system
A handshaking process for time-reversal wireless communication is provided. A first device receives a handshake signal transmitted from a second device through multiple propagation paths, the handshake signal including a preamble and a training sequence, in which the training sequence includes a sequence of symbols known to the first and second devices. A synchronization index is determined based on the preamble, and the training sequence in the handshake signal is identified based on the synchronization index. A channel response signal is determined based on the received training sequence, and a signature waveform that is a time-reversed signal of the channel response signal is generated. A transmission signal is generated based on transmit data and the signature waveform, in which the transmit data are data configured to be transmitted to the second device.
1. An apparatus for use in a time-reversal communication system, the apparatus comprising:
a first device comprising:
a first input circuit configured to receive a handshake signal including a channel probing signal transmitted from a second device through multiple propagation paths, the channel probing signal including a code known to the first and second devices;
a memory unit configured to store instructions; and
a first data processor configured to execute the instructions to:
perform at least one cross correlation operation on the code and the received channel probing signal to determine cross correlation values;
determine a synchronization index based on the cross correlation values; and
determine an estimated channel response signal based on the synchronization index and the cross correlation values; and
wherein the memory unit is further configured to:
store the estimated channel response signal.
2. The apparatus of claim 1 in which the length of the code is 60.
3. The apparatus of claim 1 in which the length of the code is greater than 60.
4. The apparatus of claim 1 in which the estimated channel response is determined by truncating a cross correlation function.
5. The apparatus of claim 1 including a channel probing signal transmitted from a third device through multiple propagation paths, the channel probing signal including a code known to the first and third devices.
6. The apparatus of claim 5 in which the code known to the first, second and third devices is the same code.
7. The apparatus of claim 1 in which the estimated channel response includes a real part of an estimated channel response and an imaginary part of an estimated channel response.
8. The apparatus of claim 1 further comprising a second data processor to generate a data signal for transmission to the second device.
9. The apparatus of claim 8 in which the data signal comprises a code and data bits.
10. The apparatus of claim 8 wherein the first data processor and the second data processor are the same processor.
11. The apparatus of claim 5 further comprising a third data processor to generate a data signal for transmission to the third device.
12. The apparatus of claim 11 wherein the first data processor and the third data processor are the same processor.
13. The apparatus of claim 1 further comprising a first output circuit configured to transmit a data signal from a first device through multiple propagation paths to the second device.
14. The apparatus of claim 5 further comprising a second output circuit configured to transmit a data signal from a first device through multiple propagation paths to the third device.
15. The apparatus of claim 11 wherein the first output circuit and the second output circuit are the same circuit.
16. An apparatus for use in a time-reversal communication system, the apparatus comprising:
a first device comprising:
a first input circuit configured to receive a handshake signal including a channel probing signal transmitted from a second device through multiple propagation paths, the channel probing signal including a code known to the first and second devices;
a memory unit configured to store instructions; and
a first data processor configured to execute the instructions to:
perform at least one cross correlation operation on the code and the received channel probing signal to determine cross correlation values;
determine a synchronization index based on the cross correlation values;
determine an estimated channel response signal based on the synchronization index and the cross correlation values; and
generate a transmit signal for communicating data between the first device and the second device, in which the transmit signal is generated based at least in part on the estimated channel response signal.
17. The apparatus of claim 16 wherein the transmit signal comprises a data signal convolved with a time-reversed version of the estimated channel response.
18. The apparatus of claim 16 wherein the transmit signal further comprises the code.
19. The apparatus of claim 16 wherein the transmit signal comprises a data signal convolved with a waveform designed to increase the signal-to-interference-and-noise ratio at the second device.
20. The apparatus of claim 19 wherein the transmit signal further comprises the code.
21. A time-reversal communication system comprising:
a first device comprising:
an first input circuit configured to receive a handshake signal including a channel probing signal transmitted from a second device through multiple propagation paths, the channel probing signal including a first code known to the first and second devices; and
a second input circuit configured to receive a handshake signal including a channel probing signal transmitted from a third device through multiple propagation paths, the channel probing signal including a second code known to the first and third devices;
a memory unit configured to store instructions; and
a first data processor configured to execute the instructions to:
perform at least one cross correlation operation on the first code and the received channel probing signal from the second device to determine first cross correlation values, a first synchronization index, and a first estimated channel response signal; and
perform at least one cross correlation operation on the second code and the received channel probing signal from the third device to determine second cross correlation values, a second synchronization index and a second estimated channel response signal; and
wherein the memory unit is further configured to:
store a first estimated channel response signal and a second estimated response signal.