Integrated Two-way Radar Backscatter Communication and Sensing with Low-power IoT Tags
Title : Integrated Two-way Radar Backscatter Communication and Sensing with Low-power IoT Tags
Authors : Ryu Okubo (University of Illinois Urbana Champaign); Luke Jacobs (University of Illinois Urbana-Champaign); Jinhua Wang, Steven Bowers (University of Virginia); Elahe Soltanaghai (University of Illinois Urbana Champaign)
Scribe: Rulan Yang (Xiamen University)
Introduction
The problem studied is the limitation of existing radar backscatter communication techniques, which only support uplink communication from the tag to the radar and neglect downlink communication. This issue is important and interesting because integrated sensing and communication (ISAC) offers a novel way to enhance spectrum and hardware utilization for both sensing and communication. By enabling both uplink and downlink communication, ISAC can significantly improve the efficiency and functionality of low-power communication systems. Existing systems and tools fall short because they do not address the need for downlink communication, thereby limiting the full potential of radar backscatter communication in practical applications.
Key idea and contribution
BiScatter’s key innovation is the design of a low-power tag structure that leverages the unique shape of radar FMCW waveform to demodulate the radar data with a lowsampling ADC to preserve the tag’s low-power consumption. Specifically, BiScatter introduces: 1) a low-power baseband processing module at the tag that can estimate the radar chirp slopes using two delay lines of different lengths, 2) a Chirp-Slope-Shift Keying (CSSK) modulation scheme that creates multi-bit symbols by varying the FMCW chirp slopes, 3) a fully integrated sensing and communication protocol that offers simultaneous operation of both modes while keeping each functionality transparent to the other ones.
Evaluation
BiScatter supports two-way backscatter communication with a BER lower than 10^-3 up to a 7m range and achieves centimeter-level tag localization accuracy using off-the-shelf FMCW radars. It shows that BisScatter significantly enhances the versatility and efficiency of ISAC for low-power devices.
Q1 : How does the communication scheme decrease the localization error compared to the result without communication? Does this imply that not using communication might maintain certain aspects, aiding in data enhancement for the organization?
A1 : Localization performance with communication and without communication is not significantly different. The statistics may end up showing similar performance. However, using different communication methods could potentially reduce localization errors. The presence of various elements might affect the accuracy, so eliminating them might help improve results
Q2: In your two-way communication setup, do you use any error-checking mechanisms like parity or CRC to ensure the comments are received correctly?
A2: The current work focuses on designing the communication system itself, and higher-level design aspects like acknowledgments and error-checking are not fully addressed yet. These features are considered future work for improving the system.
Q3: Did your experimentation consider scenarios with objects between the receiver and the radar? How does this affect communication and localization?
A3: The experiments were conducted in environments with potential multipath and interfering noise, but not explicitly with objects blocking the signal. The setup involved collecting data in an insightful environment to account for such variables.
Q4 : Could you use alternative methods, like reacting back the signal, instead of standard error-checking, to verify if the reader receives the correct comment?
A4 : This idea could be explored, but it was not part of the current design. Future work might involve developing methods to ensure accurate feedback on received comments.
Personal thoughts
BiScatter is the first integrated two-way radar backscatter system with low-power tags that work with off-the-shelf radar. Novel chirp-slope-shift-keying modulation at the radar and a low-powerdecoder at the tag. There are several future directions including extending BiScatter to multiple radar and multiple tag setup, assessing network throughput and mac layer protocol design.
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