Method and device for performing communication based on backscatter in wireless communication system
View Patent ↗A communication device includes an interrogator configured to output interrogation signals including consecutive unit chirp signals that change from a first frequency to a second frequency, and a backscatter tag configured to receive the interrogation signals and frequency-modulate the interrogation signals to generate and provide tag signals, wherein the interrogator is further configured to receive the tag signals and demodulate the tag signals.
1 . A communication device comprising:
an interrogator configured to output interrogation signals including N consecutive unit chirp signals repeated for a predetermined period T and connected to each other to maintain continuous phase, and
a backscatter tag, included in Internet-of-Things (IoT) equipment, configured to provide tag signals which are generated by frequency-modulating the interrogation signals,
wherein the interrogator is further configured to receive the tag signals and demodulate the tag signals,
wherein the backscatter tag is configured to frequency-modulate the interrogation signals with data collected by the Internet-of-Things equipment, without information about a channel allocated to the backscatter tag, provide the frequency-modulated interrogation signals as the tag signals, and communicate with the interrogator over the channel determined by a distance between the interrogator and the backscatter tag,
wherein a signal generated by demodulating the tag signals is in N−1 discrete frequency components per channel,
wherein the signal generated by demodulating the tag signals comprises a frequency component corresponding to a moving distance of the interrogation signals between the interrogator and the backscatter tag and a frequency component corresponding to a frequency modulating the interrogation signals, and
wherein the backscatter tag operates without a battery by using power collected by energy harvesting.
2 . The communication device of claim 1 , wherein the interrogation signals belong to a millimeter-wave band.
3 . The communication device of claim 1 , wherein the interrogator comprises
a demodulation unit configured to demodulate the tag signals, and
the demodulation unit comprises:
a mixer configured to mix the interrogation signals with the tag signals to generate an intermediate signal; and
a fast Fourier transform (FFT) unit configured to fast Fourier-transform the intermediate signal.
4 . The communication device of claim 3 , wherein the demodulation unit further comprises a low-pass filter configured to receive the intermediate signal and pass a signal component having a frequency corresponding to a difference between frequencies of the interrogation signals and the tag signals.
5 . The communication device of claim 3 , wherein the fast Fourier-transformed intermediate signal includes clutter noises, which are periodically positioned, and components of the tag signals, which are positioned without overlapping with the clutter noises in a frequency domain.
6 . The communication device of claim 3 , wherein, in the fast Fourier-transformed intermediate signal, clutter noises are in noise bins of a discrete frequency domain,
components of the tag signals are in tag bins of the discrete frequency domain, and
the tag bins and the noise bins do not overlap with each other in the discrete frequency domain.
7 . The communication device of claim 6 , wherein the tag signals are in one or more tag bins, and are spaced a frequency at which the backscatter tag modulates, from a plurality of noise bins respectively adjacent to the one or more tag bins.
8 . The communication device of claim 7 , wherein, when the backscatter tag is moving, the demodulation unit tracks signals of the moving backscatter tag by tracking signals spaced the frequency modulated by the backscatter tag, from the plurality of noise bins.
9 . The communication device of claim 1 , wherein the interrogator is configured to provide a single interrogation signal,
wherein the communication device includes a plurality of backscatter tags, and
wherein the interrogator is further configured to receive a plurality of tag signals generated by the plurality of backscatter tags modulating the single interrogation signal so as to perform simultaneous communication.