High-speed mmWave WiFi backscatter using commodity WiFi devices
High-speed
WiFi compatibility
Backscatter Beamforming (High SINR)
High-speed connectivity is key to enabling a range of novel IoT applications. Millimeter-wave (mmWave) backscatter has emerged as a possible solution to create high-speed, low-power IoT networks. However, state-of-the-art mmWave backscatter systems are costly due to the need for dedicated mmWave reader devices. This paper presents mmComb, a mmWave backscatter system that is built to operate on commodity mmWave WiFi. mmComb is developed with the aim that mmWave backscatter tags can be directly integrated into 802.11ad/ay mmWave WiFi networks. mmComb makes two key contributions. First, We propose a technique to communicate with backscatter tags using existing beamforming protocol frames from mmWave WiFi devices, without any protocol modification. Second, we develop a self-interference suppression solution that intelligently uses receive beamforming to extract weak mmWave backscatter signal even in indoor multipath-rich channels. We implement our solution with a tag prototype and 60 GHz commodity WiFi devices. Our results show that mmComb can achieve a maximum data rate of 55 Mbps just by leveraging 802.11ad/ay control frames while consuming 87.3 μW with BER lower than 10−3 up to 5.5 m range. This work will be presented in NSDI '24.
Selected Publications: NSDI '24, WiNTECH '20.
Extreme sensitivity massive mmWave backscatter
Millimeter-wave networking for high-speed CPS
Massive connectivity is a key to the success of the Internet of Things. While mmWave backscatter has great potential, substantial signal attenuation and overwhelming ambient reflections impose significant challenges. We present OmniScatter, a practical mmWave backscatter with an extreme sensitivity of -115 dBm. The performance is theoretically comparable to the popular commodity RFID EPC Gen2 (900 MHz), and is empirically validated via evaluations under various practical settings with abundant ambient reflections and blockages – e.g., In an office where a tag is locked in a wooden closet 6m away, as well in libraries and retail stores where a tag is placed across two rows of metal shelves. At the heart of OmniScatter is the new High Definition FMCW (HDFMCW), which interplays with the tag (FSK) signal to disentangle the ambient reflections from the tag signal in the frequency domain, essentially offering immunity to ambient reflections. To further support practical deployment, OmniScatter offers coordination-free Frequency Division Multiple Access (FDMA) that effortlessly scales to thousands of concurrent tags. The readers were built on commodity radars and the tags were prototyped on PCB. The trace-driven evaluation demonstrates concurrent communication of 1100 tags with the BER < 1.5%, paving a pathway towards practical mmWave backscatter for everyday and anywhere use. This work was presented in MobiSys '22.
​
Selected Publications: MobiSys '22. [Best Paper Award, SIGMOBILE Research Highlight]
Seamless high-speed CPS connectivity with low beamforming overhead
A seamless connectivity
Environment-driven efficient beamforming via 3D material map
As we move towards a future of connected and autonomous vehicles, high-speed and low-latency connectivity between vehicles is becoming increasingly important. This paper investigates enabling high data rate mmWave links in vehicle-to-vehicle (V2V) scenarios using street view images. We find that mmWave V2V links in urban settings suffer from frequent and prolonged blockages, resulting in unreliable connection and high beamforming overhead. Our work proposes mmSV, a system that creates 3D reflection profiles from street view images to assist vehicles in findingmmWave reflections from the environment in real-time. mmSV consists of two key components: material identification which identifies materials from street view images to determine their reflectivity and create 3D reflection map, and environment-driven raytracing and beamsearching which finds a high-SNR beam using predicted 3D material maps. Our extensive experimental results on the mmWave testbed show that mmSV can provide highly reliable V2V mmWave connectivity with low beamforming overhead. This work was presented in MobCom '23.
​
Selected Publications: Mobicom '23.
Protected reliable low-power IoT communication via WiFi guard band
Reliable low power communication
Improved energy efficiency
Under significant co-existence, the impact of cross-technology interference (CTI) has become a major threat to low-power IoT. This paper presents G-Bee, a CTI avoidance technique that uniquely places ZigBee packets on the guard band of ongoing WiFi traffic, which effectively safeguards the packet from WiFi interference. Such design ensures reliable ZigBee communication even under saturated WiFi traffic where traditional ZigBee is considered inoperable. A technical highlight is in lightweight WiFi guard band capture mechanism using ZigBee PHY layer samples directly accessible in various commercial ZigBee chips. Another exclusive feature of G-Bee is spectrum-synchronized low-duty cycling – by utilizing guard bands of periodic WiFi beacons, active slots are effectively synchronized to spectrum availability (i.e., guard band) for significant delay improvement. Extensive evaluations of our prototype system demonstrate G-Bee PRR over 95% where legacy ZigBee drops to below 15% under significant interference with hundreds of WiFi users and reduction of low-duty cycle delay by 87.5%, all of which are achieved with a light computational overhead of 0.3%. This work was presented in SenSys '18.
​
Selected Publications: SenSys'18.