Shifted backscattering-based channel estimation for wireless power transfer to passive devices
Disclosed are systems, apparatuses, processes, and computer-readable media for wireless communications. For example, a network device can transmit, to a group of passive devices, a continuous wave (CW) signal. The network device can receive, from each passive device of the group of passive devices, at least one backscatter signal, based on the CW signal, at a respective frequency shift. The network device can estimate, based on the at least one backscatter signal, channel information for each passive device of the group of passive devices. The network device can then determine, based on the channel information, a channel for transmitting an energy signal to at least one passive device of the group of passive devices for energy harvesting.
1 . A network device for wireless communication, the network device comprising:
at least one memory; and
at least one processor coupled to the at least one memory and configured to:
output, for transmission to a group of passive devices, a continuous wave (CW) signal;
receive, from each passive device of the group of passive devices, at least one backscatter signal, based on the CW signal, at a respective frequency shift;
estimate, based on the at least one backscatter signal, channel information for each passive device of the group of passive devices; and
determine, based on the channel information, a frequency of a channel for transmitting an energy signal to at least one passive device of the group of passive devices for energy harvesting.
2 . The network device of claim 1 , wherein the network device is a base station.
3 . The network device of claim 1 , wherein each passive device of the group of passive devices is a radio frequency identification (RFID) tag.
4 . The network device of claim 1 , wherein the at least one processor is configured to output the CW signal for transmission in one or more channels at one or more times.
5 . The network device of claim 1 , wherein the at least one processor is configured to determine the respective frequency shift for each passive device of the group of passive devices based on a parts per million (PPM) requirement for each passive device.
6 . The network device of claim 1 , wherein the at least one processor is configured to determine the respective frequency shift for each passive device of the group of passive devices based on a frequency shift capability for each passive device.
7 . The network device of claim 1 , wherein the at least one processor is configured to output, for transmission to each passive device in the group of passive devices, a signal comprising the respective frequency shift for each passive device of the group of passive devices.
8 . The network device of claim 1 , wherein the at least one processor is configured to output the energy signal on the channel for transmission to the at least one passive device of the group of passive devices.
9 . The network device of claim 1 , wherein the at least one processor is configured to determine that the at least one passive device of the group of passive devices needs energy harvesting based on the channel information.
10 . The network device of claim 1 , wherein the respective frequency shift is caused by each passive device.
11 . The network device of claim 1 , wherein the at least one processor is configured to output a backscattering threshold value for transmission to at least one passive device of the group of passive devices, the backscattering threshold value indicating a maximum level for transmitting a backscatter signal.
12 . The network device of claim 11 , wherein the maximum level for transmitting the backscatter signal is a maximum gain value of the CW signal received by the at least one passive device.
13 . The network device of claim 1 , wherein the at least one processor is configured to output, for transmission to at least one passive device of the group of passive devices, an indication of a number of channels for which the channel information is estimated.
14 . A passive device for wireless communication, the passive device comprising:
at least one memory; and
at least one processor coupled to the at least one memory and configured to:
receive, from a network device, a continuous wave (CW) signal;
output, for transmission to the network device based on the CW signal, a backscatter signal at a frequency shift for estimating channel information for the passive device; and
receive, from the network device via a channel based on a channel frequency determined based on the estimated channel information, an energy harvesting signal based on the estimated channel information.
15 . The passive device of claim 14 , wherein to output the backscatter signal at a frequency shift, the at least one processor is configured to adjust the backscatter signal.
16 . The passive device of claim 14 , wherein the passive device is a radio frequency identification (RFID) tag.
17 . The passive device of claim 14 , wherein the network device is a base station.
18 . The passive device of claim 14 , wherein the at least one processor is configured to output, for transmission to the network device, a parts per million (PPM) requirement for the passive device.
19 . The passive device of claim 14 , wherein the at least one processor is configured to output, for transmission to the network device, a number of frequency shifts supported by the passive device.
20 . The passive device of claim 14 , wherein the at least one processor is configured to receive, from the network device, a signal comprising the frequency shift for the passive device.
21 . The passive device of claim 14 , wherein the channel information comprises channel state information (CSI).
22 . The passive device of claim 14 , wherein the at least one processor is configured to:
receive, from the network device, a backscattering threshold value, the backscattering threshold value indicating a maximum level for transmitting a backscatter signal; and
determine, based on the backscattering threshold value, to transmit the backscatter signal to the network device.
23 . The passive device of claim 22 , wherein the maximum level for transmitting the backscatter signal is a maximum gain value of the received CW signal.
24 . The passive device of claim 14 , wherein the at least one processor is configured to:
receive, from the network device, an indication of a number of channels for which the channel information is estimated.
25 . A method of wireless communication performed by a network device, comprising:
transmitting, by the network device to a group of passive devices, a continuous wave (CW) signal;
receiving, by the network device from each passive device of the group of passive devices, at least one backscatter signal, based on the CW signal, at a respective frequency shift;
estimating, by the network device based on the at least one backscatter signal, channel information for each passive device of the group of passive devices; and
determining, by the network device based on the channel information, a frequency of a channel for transmitting an energy signal to at least one passive device of the group of passive devices for energy harvesting.
26 . The method of claim 25 , further comprising determining, by the network device, the respective frequency shift for each passive device of the group of passive devices based on a parts per million (PPM) requirement for each passive device.
27 . The method of claim 25 , further comprising determining, by the network device, the respective frequency shift for each passive device of the group of passive devices based on a frequency shift capability for each passive device.
28 . The method of claim 25 , further comprising transmitting a backscattering threshold value to at least one passive device of the group of passive devices, the backscattering threshold value indicating a maximum level for transmitting a backscatter signal.
29 . The method of claim 25 , further comprising transmitting, to at least one passive device of the group of passive devices, an indication of a number of channels for which the channel information is estimated.
30 . A method of wireless communication performed by a passive device, comprising:
receiving, by the passive device from a network device, a continuous wave (CW) signal;
transmitting, by the passive device to the network device based on the CW signal, a backscatter signal at a frequency shift for estimating channel information for the passive device; and
receiving, from the network device via a channel based on a channel frequency determined based on the estimated channel information, an energy harvesting signal based on the estimated channel information.