Publications

2024

1. MobiCom’24

   Exploring Biomagnetism for Inclusive Vital Sign Monitoring: Modeling and Implementation

   Xiuzhen Guo, Long Tan , Tao Chen , and 6 more authors

   In ACM International Conference on Mobile Computing and Networking (MobiCom) , Oct 2024

   Abs Bib

   This paper presents the design, implementation, and evaluation of MagWear, a novel biomagnetism-based system that can accurately and inclusively monitor the heart rate and respiration rate of mobile users with diverse skin tones. MagWear’s contributions are twofold. Firstly, we build a mathematical model that characterizes the magnetic coupling effect of blood flow under the influence of an external magnetic field. This model uncovers the variations in accuracy when monitoring vital signs among individuals. Secondly, leveraging insights derived from this mathematical model, we present a softwarehardware co-design that effectively handles the impact of human diversity on the performance of vital sign monitoring, pushing this generic solution one big step closer to real adoptions. We have implemented a prototype of MagWear on a two-layer PCB board and followed IRB protocols to conduct system evaluations. Our extensive experiments involving 30 volunteers demonstrate that MagWear achieves high monitoring accuracy with a mean percentage error (MPE) of 1.55% for heart rate and 1.79% for respiration rate. The head-tohead comparison with Apple Watch 8 further demonstrates MagWear’s consistently high performance in different user conditions.

   @inproceedings{guo24mobicom,
     title = {{Exploring Biomagnetism for Inclusive Vital Sign Monitoring: Modeling and Implementation}},
     author = {Guo, Xiuzhen and Tan, Long and Chen, Tao and Gu, Chaojie and Shu, Yuanchao and He, Shibo and He, Yuan and Chen, Jiming and Shangguan, Longfei},
     booktitle = {ACM International Conference on Mobile Computing and Networking (MobiCom)},
     year = {2024},
     month = oct,
   }

2. INFOCOM’24

   TRIDENT: Interference Avoidance in Multi-reader Backscatter Network via Frequency-space Division

   Yang Zou , Xin Na , Xiuzhen Guo, and 2 more authors

   In Proceedings of IEEE INFOCOM , Oct 2024

   Abs Bib PDF

   Backscatter is an enabling technology for battery-free sensing in industrial IoT applications. For the purpose of full coverage of numerous tags in the deployment area, one often needs to deploy multiple readers, each of which is to communicate with tags within its communication range. But the actual backscattered signals from a tag are likely to reach a reader outside its communication range, causing undesired interference. Conventional approaches for interference avoidance, either TDMA or CSMA based, separate the readers’ media accesses in the time dimension and suffer from limited network throughput. In this paper, we propose TRIDENT, a novel backscatter tag design that enables interference avoidance with frequency-space division. By incorporating a tunable bandpass filter and multiple terminal loads, a TRIDENT tag is able to detect its channel condition and adaptively adjust the frequency band and the power of its backscattered signals, so that all the readers in the network can operate concurrently without being interfered. We implement TRIDENT and evaluate its performance under various settings. The results demonstrate that TRIDENT enhances the network throughput by 3.18×, compared to the TDMA based scheme.

   @inproceedings{yang2024trident,
     title = {TRIDENT: Interference Avoidance in Multi-reader Backscatter Network via Frequency-space Division},
     author = {Zou, Yang and Na, Xin and Guo, Xiuzhen and Sun, Yimiao and He, Yuan},
     booktitle = {Proceedings of IEEE INFOCOM},
     year = {2024},
     doi = {},
   }

3. MobiCom’24

   Exploring the Feasibility of Remote Cardiac Auscultation Using Earphones.

   Tao Chen , Yongjie Yang , Xiaoran Fan , and 3 more authors

   In ACM International Conference on Mobile Computing and Networking (MobiCom) , Oct 2024

   Abs Bib PDF

   The elderly over 65 accounts for 80% of COVID deaths in the United States. In response to the pandemic, the federal, state governments, and commercial insurers are promoting video visits, through which the elderly can access specialists at home over the Internet, without the risk of COVID exposure. However, the current video visit practice barely relies on video observation and talking. The specialist could not assess the patient’s health conditions by performing auscultations. This paper tries to address this key missing component in video visits by proposing Asclepius, a hardware-software solution that turns the patient’s earphones into a stethoscope, allowing the specialist to hear the patient’s fine-grained heart sound (i.e., PCG signals) in video visits. To achieve this goal, we contribute a low-cost plug-in peripheral that repurposes the earphone’s speaker into a microphone and uses it to capture the patient’s minute PCG signals from her ear canal. As the PCG signals suffer from strong attenuation and multi-path effects when propagating from the heart to ear canals, we then propose efficient signal processing algorithms coupled with a data-driven approach to de-reverberate and further correct the amplitude and frequency distortion in raw PCG receptions. We implement Asclepius on a 2-layer PCB board and follow the IRB protocol to evaluate its performance with 30 volunteers. Our extensive experiments show that Asclepius can effectively recover Phonocardiogram (PCG) signals with different types of earphones. The objective blind testing and subjective interview with five cardiologists further confirm the clinical efficacy and efficiency of our system. PCG signal samples, benchmark results, and cardiologist interviews can be found at: https://asclepius-system.github.io/

   @inproceedings{ACMMobiCom2024,
     title = {Exploring the Feasibility of Remote Cardiac Auscultation Using Earphones.},
     author = {Chen, Tao and Yang, Yongjie and Fan, Xiaoran and Guo, Xiuzhen and Xiong, Jie and Shangguan, Longfei},
     booktitle = {ACM International Conference on Mobile Computing and Networking (MobiCom)},
     year = {2024},
   }

2023

1. MobiSys’23

   Leggiero: Analog WiFi Backscatter with Payload Transparency

   Xin Na , Xiuzhen Guo, Zihao Yu , and 3 more authors

   In Proceedings of the 21st Annual International Conference on Mobile Systems, Applications and Services , Oct 2023

   Abs Bib PDF

   Backscatter is an enabling technology for battery-free sensing in today’s Artificial Intelligence of Things (AIOT). Building a backscatter-based sensing system, however, is a daunting task, due to two obstacles: the unaffordable power consumption of the microprocessor and the coexistence with the ambient carrier’s traffic. In order to address the above issues, in this paper, we present Leggiero, the first-of-its-kind analog WiFi backscatter with payload transparency. Leveraging a specially designed circuit with a varactor diode, this design avoids using a microprocessor to interface between the radio and the sensor, and directly converts the analog sensor signal into the phase of RF (radio frequency) signal. By carefully designing the reference circuit on the tag and precisely locating the extra long training field (LTF) section of a WiFi packet, Leggiero embeds the analog phase value into the channel state information (CSI). A commodity WiFi receiver without hardware modification can simultaneously decode the WiFi and the sensor data. We implement Leggiero design and evaluate its performance under varied settings. The results show that the power consumption of the Leggiero tag (excluding the power of the peripheral sensor module) is 30μW at a sampling rate of 400Hz, which is 4.8\texttimes and 4\texttimes lower than the state-of-the-art WiFi backscatter schemes. The uplink throughput of Leggiero is suficient to support a variety of sensing applications, while keeping the WiFi carrier’s throughput performance unaffected.

   @inproceedings{10.1145/3581791.3596835,
     author = {Na, Xin and Guo, Xiuzhen and Yu, Zihao and Zhang, Jia and He, Yuan and Liu, Yunhao},
     title = {Leggiero: Analog WiFi Backscatter with Payload Transparency},
     year = {2023},
     isbn = {9798400701108},
     publisher = {Association for Computing Machinery},
     address = {New York, NY, USA},
     url = {https://doi.org/10.1145/3581791.3596835},
     doi = {10.1145/3581791.3596835},
     booktitle = {Proceedings of the 21st Annual International Conference on Mobile Systems, Applications and Services},
     pages = {436--449},
     numpages = {14},
     keywords = {RF computing, phase, analog, backscatter},
     location = {Helsinki, Finland},
     series = {MobiSys '23},
   }

2022

1. ACM CSUR

   Cross-Technology Communication for the Internet of Things: A Survey

   Yuan He , Xiuzhen Guo, Xiaolong Zheng , and 5 more authors

   ACM Comput. Surv., Dec 2022

   Abs Bib PDF

   The ever-developing Internet of Things (IoT) brings the prosperity of wireless sensing and control applications. In many scenarios, different wireless technologies coexist in the shared frequency medium as well as the physical space. Such wireless coexistence may lead to serious cross-technology interference (CTI) problems, e.g., channel competition, signal collision, and throughput degradation. Compared with traditional methods like interference avoidance, tolerance, and concurrency mechanism, direct and timely information exchange among heterogeneous devices is therefore a fundamental requirement to ensure the usability, inter-operability, and reliability of the IoT. Under this circumstance, Cross-Technology Communication (CTC) technique thus becomes a hot topic in both academic and industrial fields, which aims at directly exchanging data among heterogeneous devices that follow different standards. This paper comprehensively summarizes the CTC techniques and reveals that the key challenge for CTC lies in the heterogeneity of IoT devices, including the incompatibility of technical standards and the asymmetry of connection capability. Based on the above finding, we present a taxonomy of the existing CTC works (packet-level CTCs and physical-level CTCs) and compare the existing CTC techniques in terms of throughput, reliability, hardware modification, and concurrency.

   @article{10.1145/3530049,
     author = {He, Yuan and Guo, Xiuzhen and Zheng, Xiaolong and Yu, Zihao and Zhang, Jia and Jiang, Haotian and Na, Xin and Zhang, Jiacheng},
     title = {Cross-Technology Communication for the Internet of Things: A Survey},
     year = {2022},
     issue_date = {May 2023},
     publisher = {Association for Computing Machinery},
     address = {New York, NY, USA},
     volume = {55},
     number = {5},
     issn = {0360-0300},
     url = {https://doi.org/10.1145/3530049},
     doi = {10.1145/3530049},
     journal = {ACM Comput. Surv.},
     month = dec,
     articleno = {89},
     numpages = {29},
     keywords = {Wireless communication, heterogeneous coexistence, Cross-Technology Communication, research survey},
   }

2. MobiCom’22

   RF-transformer: a unified backscatter radio hardware abstraction

   Xiuzhen Guo, Yuan He , Zihao Yu , and 3 more authors

   In Proceedings of the 28th Annual International Conference on Mobile Computing And Networking , Dec 2022

   Abs Bib PDF

   This paper presents RF-Transformer, a unified backscatter radio hardware abstraction that allows a low-power IoT device to directly communicate with heterogeneous wireless receivers at the minimum power consumption. Unlike existing backscatter systems that are tailored to a specific wireless communication protocol, RF-Transformer provides a programmable interface to the micro-controller, allowing IoT devices to synthesize different types of protocol-compliant backscatter signals sharing radically different PHY-layer designs. To show the efficacy of our design, we implement a PCB prototype of RF-Transformer on 2.4 GHz ISM band and showcase its capability on generating standard ZigBee, Bluetooth, LoRa, and Wi-Fi 802.11b/g/n/ac packets. Our extensive field studies show that RF-Transformer achieves 23.8 Mbps, 247.1 Kbps, 986.5 Kbps, and 27.3 Kbps throughput when generating standard Wi-Fi, ZigBee, Bluetooth, and LoRa signals while consuming 7.6–74.2X less power than their active counterparts. Our ASIC simulation based on the 65-nm CMOS process shows that the power gain of RF-Transformer can further grow to 92–678X. We further integrate RF-Transformer with pressure sensors and present a case study on detecting foot traffic density in hallways. Our 7-day case studies demonstrate RF-Transformer can reliably transmit sensor data to a commodity gateway by synthesizing LoRa packets on top of Wi-Fi signals. Our experimental results also verify the compatibility of RF-Transformer with commodity receivers. Code and hardware schematics can be found at: https://github.com/LeFsCC/RF-Transformer.

   @inproceedings{10.1145/3495243.3560549,
     author = {Guo, Xiuzhen and He, Yuan and Yu, Zihao and Zhang, Jiacheng and Liu, Yunhao and Shangguan, Longfei},
     title = {RF-transformer: a unified backscatter radio hardware abstraction},
     year = {2022},
     isbn = {9781450391818},
     publisher = {Association for Computing Machinery},
     address = {New York, NY, USA},
     url = {https://doi.org/10.1145/3495243.3560549},
     doi = {10.1145/3495243.3560549},
     booktitle = {Proceedings of the 28th Annual International Conference on Mobile Computing And Networking},
     pages = {446–458},
     numpages = {13},
     keywords = {PHY layer design, backscatter technology, internet of things (IoT), wireless communication},
     location = {Sydney, NSW, Australia},
     series = {MobiCom '22},
   }

3. NSDI 22

   Saiyan: Design and Implementation of a Low-power Demodulator for LoRa Backscatter Systems

   Xiuzhen Guo, Longfei Shangguan , Yuan He , and 4 more authors

   In 19th USENIX Symposium on Networked Systems Design and Implementation (NSDI 22) , Apr 2022

   Abs Bib PDF

   The radio range of backscatter systems continues growing as new wireless communication primitives are continuously invented. Nevertheless, both the bit error rate and the packet loss rate of backscatter signals increase rapidly with the radio range, thereby necessitating the cooperation between the access point and the backscatter tags through a feedback loop. Unfortunately, the low-power nature of backscatter tags limits their ability to demodulate feedback signals from a remote access point and scales down to such circumstances. This paper presents Saiyan, an ultra-low-power demodulator for long-range LoRa backscatter systems. With Saiyan, a backscatter tag can demodulate feedback signals from a remote access point with moderate power consumption and then perform an immediate packet re-transmission in the presence of packet loss. Moreover, Saiyan enables rate adaption and channel hopping – two PHY-layer operations that are important to channel efficiency yet unavailable on long-range backscatter systems. We prototype Saiyan on a two-layer PCB board and evaluate its performance in different environments. Results show that Saiyan achieves 3.5–5× gain on the demodulation range, compared with state-of-the-art systems. Our ASIC simulation shows that the power consumption of Saiyan is around 93.2 µW. Code and hardware schematics can be found at: https://github.com/ZangJac/Saiyan.

   @inproceedings{276974,
     author = {Guo, Xiuzhen and Shangguan, Longfei and He, Yuan and Jing, Nan and Zhang, Jiacheng and Jiang, Haotian and Liu, Yunhao},
     title = {Saiyan: Design and Implementation of a Low-power Demodulator for {LoRa} Backscatter Systems},
     booktitle = {19th USENIX Symposium on Networked Systems Design and Implementation (NSDI 22)},
     year = {2022},
     isbn = {978-1-939133-27-4},
     address = {Renton, WA},
     pages = {437--451},
     url = {https://www.usenix.org/conference/nsdi22/presentation/guo},
     publisher = {USENIX Association},
     month = apr,
   }

4. NSDI 22

   CurvingLoRa to Boost LoRa Network Throughput via Concurrent Transmission

   Chenning Li , Xiuzhen Guo, Longfei Shangguan , and 2 more authors

   In 19th USENIX Symposium on Networked Systems Design and Implementation (NSDI 22) , Apr 2022

   Abs Bib PDF Slides

   LoRaWAN has emerged as an appealing technology to connect IoT devices but it functions without explicit coordination among transmitters, which can lead to many packet collisions as the network scales. State-of-the-art work proposes various approaches to deal with these collisions, but most functions only in high signal-to-interference ratio (SIR) conditions and thus does not scale to real scenarios where weak receptions are easily buried by stronger receptions from nearby transmitters. In this paper, we take a fresh look at LoRa’s physical layer, revealing that its underlying linear chirp modulation fundamentally limits the capacity and scalability of concurrent LoRa transmissions. We show that by replacing linear chirps with their non-linear counterparts, we can boost the throughput of concurrent LoRa transmissions and empower the LoRa receiver to successfully receive weak transmissions in the presence of strong colliding signals. Such a non-linear chirp design further enables the receiver to demodulate fully aligned collision symbols — a case where none of the existing approaches can deal with. We implement these ideas in a holistic LoRaWAN stack based on the USRP N210 software-defined radio platform. Our head-to-head comparison with two stateof-the-art research systems and a standard LoRaWAN baseline demonstrates that CurvingLoRa1 improves the network throughput by 1.6–7.6⇥ while simultaneously sacrificing neither power efficiency nor noise resilience.

   @inproceedings{278330,
     author = {Li, Chenning and Guo, Xiuzhen and Shangguan, Longfei and Cao, Zhichao and Jamieson, Kyle},
     title = {{CurvingLoRa} to Boost {LoRa} Network Throughput via Concurrent Transmission},
     booktitle = {19th USENIX Symposium on Networked Systems Design and Implementation (NSDI 22)},
     year = {2022},
     isbn = {978-1-939133-27-4},
     address = {Renton, WA},
     pages = {879--895},
     url = {https://www.usenix.org/conference/nsdi22/presentation/li-chenning},
     publisher = {USENIX Association},
     month = apr,
   }

5. ToN’21

   Efficient Ambient LoRa Backscatter With On-Off Keying Modulation

   Xiuzhen Guo, Longfei Shangguan , Yuan He , and 4 more authors

   IEEE/ACM Transactions on Networking, Apr 2022

   Abs Bib PDF

   Backscatter communication holds potential for ubiquitous and low-cost connectivity among low-power IoT devices. To avoid interference between the carrier signal and the backscatter signal, recent works propose a frequency-shifting technique to separate these two signals in the frequency domain. Such proposals, however, have to occupy the precious wireless spectrum that is already overcrowded, and increase the power, cost, and complexity of the backscatter tag. In this paper, we revisit the classic ON-OFF Keying (OOK) modulation and propose Aloba, a backscatter system that takes the ambient LoRa transmissions as the excitation and piggybacks the in-band OOK modulated signals over the LoRa transmissions. Our design enables the backsactter signal to work in the same frequency band of the carrier signal, meanwhile achieving flexible data rate at different transmission range. The key contributions of Aloba include: i) the design of a low-power backscatter tag that can pick up the ambient LoRa signals from other signals; ii) a novel decoding algorithm to demodulate both the carrier signal and the backscatter signal from their superposition. We further adopt link coding mechanism and interleave operation to enhance the reliability of backscatter signal decoding. We implement Aloba and conduct head-to-head comparison with the state-ofthe-art LoRa backscatter system PLoRa in various settings. The experiment results show Aloba can achieve 39.5–199.4 Kbps data rate at various distances, 10.4–52.4× higher than PLoRa.

   @article{9596585,
     author = {Guo, Xiuzhen and Shangguan, Longfei and He, Yuan and Zhang, Jia and Jiang, Haotian and Siddiqi, Awais Ahmad and Liu, Yunhao},
     journal = {IEEE/ACM Transactions on Networking},
     title = {Efficient Ambient LoRa Backscatter With On-Off Keying Modulation},
     year = {2022},
     volume = {30},
     number = {2},
     pages = {641-654},
     keywords = {Backscatter;Chirp;Throughput;Receivers;Modulation;Decoding;Demodulation;Wireless networks;backscatter communication;LoRa},
     doi = {10.1109/TNET.2021.3121787},
   }

6. UbiComp’22

   MotorBeat: Acoustic Communication for Home Appliances via Variable Pulse Width Modulation

   Weiguo Wang , Jinming Li , Yuan He , and 2 more authors

   Proc. ACM Interact. Mob. Wearable Ubiquitous Technol., Mar 2022

   Abs Bib PDF

   More and more home appliances are now connected to the Internet, thus enabling various smart home applications. However, a critical problem that may impede the further development of smart home is overlooked: Small appliances account for the majority of home appliances, but they receive little attention and most of them are cut off from the Internet. To fill this gap, we propose MotorBeat, an acoustic communication approach that connects small appliances to a smart speaker. Our key idea is to exploit direct current (DC) motors, which are common components of small appliances, to transmit acoustic messages. We design a novel scheme named Variable Pulse Width Modulation (V-PWM) to drive DC motors. MotorBeat achieves the following 3C goals: (1) Comfortable to hear, (2) Compatible with multiple motor modes, and (3) Concurrent transmission. We implement MotorBeat with commercial devices and evaluate its performance on three small appliances and ten DC motors. The results show that the communication range can be up to 10 m.

   @article{10.1145/3517255,
     author = {Wang, Weiguo and Li, Jinming and He, Yuan and Guo, Xiuzhen and Liu, Yunhao},
     title = {MotorBeat: Acoustic Communication for Home Appliances via Variable Pulse Width Modulation},
     year = {2022},
     issue_date = {March 2022},
     publisher = {Association for Computing Machinery},
     address = {New York, NY, USA},
     volume = {6},
     number = {1},
     url = {https://doi.org/10.1145/3517255},
     doi = {10.1145/3517255},
     journal = {Proc. ACM Interact. Mob. Wearable Ubiquitous Technol.},
     month = mar,
     articleno = {31},
     numpages = {24},
     keywords = {Acoustic Communication, Electric Motor, Home Appliance, Smart Speaker},
   }

2021

1. SenSys’21

   Sense Me on the Ride: Accurate Mobile Sensing over a LoRa Backscatter Channel

   Haotian Jiang , Jiacheng Zhang , Xiuzhen Guo, and 1 more author

   In Proceedings of the 19th ACM Conference on Embedded Networked Sensor Systems , Mar 2021

   Abs Bib PDF

   Wireless sensing has great significance in Internet of Things (IoT) applications and has attracted substantial research interests in academia. In this study, we propose Palantir, a first-of-its-kind long-range sensing system based on the LoRa backscatter technology. By utilizing the ON-OFF-Keying modulated backscatter signals, Palantir can perform fine-grained long-range cyclist sensing. Our findings show that sensing is more susceptible to channel quality than communication. Hence, the design of Palantir particularly addresses the critical challenges of signal processing, such as amplitude instability, frequency offset, clock drift, spectrum leakage, and multiplicative noise. We implement Palantir and evaluate its performance by conducting comprehensive benchmark experiments. A prototype is also built and a case study of respiration monitoring in the real world is implemented. Results demonstrate that Palantir can perform accurate sensing at a range up to 100 m, which is twice that of state-of-the-art approaches. The median deviation of the detected motion period is as low as 0.2%.

   @inproceedings{10.1145/3485730.3485933,
     author = {Jiang, Haotian and Zhang, Jiacheng and Guo, Xiuzhen and He, Yuan},
     title = {Sense Me on the Ride: Accurate Mobile Sensing over a LoRa Backscatter Channel},
     year = {2021},
     isbn = {9781450390972},
     publisher = {Association for Computing Machinery},
     address = {New York, NY, USA},
     url = {https://doi.org/10.1145/3485730.3485933},
     doi = {10.1145/3485730.3485933},
     booktitle = {Proceedings of the 19th ACM Conference on Embedded Networked Sensor Systems},
     pages = {125–137},
     numpages = {13},
     keywords = {Backscatter, LoRa, Sensing},
     location = {Coimbra, Portugal},
     series = {SenSys '21},
   }

2. ToN’21

   WIDE: Physical-Level CTC via Digital Emulation

   Yuan He , Xiuzhen Guo, Jia Zhang , and 1 more author

   IEEE/ACM Transactions on Networking, Mar 2021

   Abs Bib PDF

   Cross-Technology Communication (CTC) is an emerging technique that enables direct communication across different wireless technologies. Recent works achieve physicallevel CTC by emulating the standard time-domain waveform of the receiver. This method faces the challenges of inherent unreliability due to the imperfect emulation. Different from analog emulation, we propose a novel concept named digital emulation, which stems from the following insight: The receiver relies on phase shift rather than the phase itself to decode signals. Instead of emulating the original time-domain waveform, the sender emulates the phase shift associated with the desired signals. Clearly there are multiple different phase sequences that correspond to the same signs of phase shifts. Digital emulation has flexibility in setting the phase values in the emulated signals, which is effective in reducing emulation errors and enhancing the reliability of CTC. The key point of digital emulation is generic and applicable to a set of CTCs, where the transmitter has a wider bandwidth for emulation and the receiver decoding is based on the phase shift. In this paper, we implement our proposal as WIDE, a physical-level CTC via digital emulation from WiFi to ZigBee. We conduct extensive experiments to evaluate the performance of WIDE. The results show that WIDE significantly improves the Packet Reception Ratio (PRR) from 41.7% to 86.2%, which is 2× of WEBee’s, an existing representative physical-level CTC.

   @article{9416311,
     author = {He, Yuan and Guo, Xiuzhen and Zhang, Jia and Jiang, Haotian},
     journal = {IEEE/ACM Transactions on Networking},
     title = {WIDE: Physical-Level CTC via Digital Emulation},
     year = {2021},
     volume = {29},
     number = {4},
     pages = {1567-1579},
     keywords = {Emulation;Zigbee;Wireless fidelity;Receivers;Time-domain analysis;Standards;Reliability;Cross-technology communication;digital emulation},
     doi = {10.1109/TNET.2021.3071782},
   }

3. ToSN’21

   Taming the Errors in Cross-Technology Communication: A Probabilistic Approach

   Xiuzhen Guo, Yuan He , Jia Zhang , and 3 more authors

   ACM Trans. Sen. Netw., Oct 2021

   Abs Bib PDF

   Cross-Technology Communication (CTC) emerges as a technology to enable direct communication across different wireless technologies. The state of the art on CTC employs physical-level emulation. Due to the protocol incompatibility and the hardware restriction, there are intrinsic emulation errors between the emulated signals and the legitimate signals. Unresolved emulation errors hurt the reliability of CTC and the achievable throughput, but how to improve the reliability of CTC remains a challenging problem. Taking the CTC from WiFi to BLE as an example, this work first presents a comprehensive understanding of the emulation errors. We then propose WEB, a practical CTC approach that can be implemented with commercial devices. The core design of WEB is split encoding: based on the probabilistic distribution of emulation errors, the WiFi sender manipulates its payload to maximize the successful decoding rate at the BLE receiver. We implement WEB and evaluate its performance with extensive experiments. Compared to two existing approaches, WEBee and WIDE, WEB reduces the SER (Symbol Error Rate) by 54.6% and 42.2%, respectively. For the first time in the community, WEB achieves practically effective CTC from WiFi to BLE, with an average throughput of 522.2 Kbps.

   @article{10.1145/3469031,
     author = {Guo, Xiuzhen and He, Yuan and Zhang, Jia and Jiang, Haotian and Yu, Zihao and Na, Xin},
     title = {Taming the Errors in Cross-Technology Communication: A Probabilistic Approach},
     year = {2021},
     issue_date = {February 2022},
     publisher = {Association for Computing Machinery},
     address = {New York, NY, USA},
     volume = {18},
     number = {1},
     issn = {1550-4859},
     url = {https://doi.org/10.1145/3469031},
     doi = {10.1145/3469031},
     journal = {ACM Trans. Sen. Netw.},
     month = oct,
     articleno = {3},
     numpages = {20},
     keywords = {Cross-technology, WiFi to BLE, split encoding},
   }

4. IoT Journal ’21

   LEGO-Fi: Transmitter-Transparent CTC With Cross-Demapping

   Xiuzhen Guo, Yuan He , Xiaolong Zheng , and 2 more authors

   IEEE Internet of Things Journal, Apr 2021

   Abs Bib PDF

   Cross-Technology Communication (CTC) is an emerging technique that enables direct communication across different wireless technologies. The state-of-the-art works in this area propose physical-level CTC, in which the transmitters emulate signals that follow the receiver’s standard. Physical-level CTC means considerable processing complexity at the transmitter, which does not apply to the communication from a low-end transmitter to a high-end receiver. This article proposes LEGO-Fi, which supports the CTC from ZigBee to WiFi and Bluetooth to WiFi. LEGO-Fi is a transmitter-transparent CTC technique, which leaves the processing complexity solely at the receiver side and therefore, makes a critical advance toward bidirectional high-throughput CTC. The key technique inside is cross-demapping, which stems from two key technical insights: 1) a ZigBee/Bluetooth packet leaves distinguishable features when passing the WiFi modules and 2) compared to ZigBee’s/Bluetooth’s simple encoding and modulation schemes, the rich processing capacity of WiFi offers extra flexibility to process a ZigBee/Bluetooth packet. The evaluation results show that LEGO-Fi achieves a throughput of 213.6 Kb/s in practice, which is, respectively, 13000×, 1200×, and 7.5× faster than FreeBee, ZigFi, and SymBee, the three existing ZigBee-to-WiFi CTC approaches. For the CTC from Bluetooth to WiFi, LEGO-Fi achieves a throughput of 904.1 Kb/s.

   @article{9344714,
     author = {Guo, Xiuzhen and He, Yuan and Zheng, Xiaolong and Yu, Zihao and Liu, Yunhao},
     journal = {IEEE Internet of Things Journal},
     title = {LEGO-Fi: Transmitter-Transparent CTC With Cross-Demapping},
     year = {2021},
     month = apr,
     volume = {8},
     number = {8},
     pages = {6665-6676},
     keywords = {Zigbee;Wireless fidelity;Throughput;Receivers;Standards;Payloads;Synchronization;Cross-demapping;cross-technology;ZigBee-to-WiFi},
     doi = {10.1109/JIOT.2021.3054669},
   }

5. CWSN 2021

   Location Tracking over a LoRa Backscattering Channel

   Jiacheng Zhang , Xiuzhen Guo, and Yuan He

   CWSN, Apr 2021
6. SECON’21

   Wi-attack: Cross-technology Impersonation Attack against iBeacon Services

   Xin Na , Xiuzhen Guo, Yuan He , and 1 more author

   In 2021 18th Annual IEEE International Conference on Sensing, Communication, and Networking (SECON) , Apr 2021

   Abs Bib PDF

   iBeacon protocol is widely deployed to provide location-based services. By receiving its BLE advertisements, nearby devices can estimate the proximity to the iBeacon or calculate indoor positions. However, the open nature of these advertisements brings vulnerability to impersonation attacks. Such attacks could lead to spam, unreliable positioning, and even security breaches. In this paper, we propose Wi-attack, revealing the feasibility of using WiFi devices to conduct impersonation attacks on iBeacon services. Different from impersonation attacks using BLE compatible hardware, Wi-attack is not restricted by broadcasting intervals and is able to impersonate multiple iBeacons at the same time. Effective attacks can be launched on iBeacon services without modifications to WiFi hardware or firmware. To enable direct communication from WiFi to BLE, we use the digital emulation technique of cross technology communication. To enhance the packet reception along with its stability, we add redundant packets to eliminate cyclic prefix error entirely. The emulation provides an iBeacon packet reception rate up to 66.2%. We conduct attacks on three iBeacon services scenarios, point deployment, multilateration, and fingerprint-based localization. The evaluation results show that Wi-attack can bring an average distance error of more than 20 meters on fingerprint-based localization using only 3 APs.

   @inproceedings{9491605,
     author = {Na, Xin and Guo, Xiuzhen and He, Yuan and Xi, Rui},
     booktitle = {2021 18th Annual IEEE International Conference on Sensing, Communication, and Networking (SECON)},
     title = {Wi-attack: Cross-technology Impersonation Attack against iBeacon Services},
     year = {2021},
     volume = {},
     number = {},
     pages = {1-9},
     keywords = {Location awareness;Meters;Protocols;Emulation;Fingerprint recognition;Hardware;Sensors},
     doi = {10.1109/SECON52354.2021.9491605},
   }

7. ICDCS’21

   BiCord: Bidirectional Coordination among Coexisting Wireless Devices

   Zihao Yu , Pengyu Li , Carlo Alberto Boano , and 4 more authors

   In 2021 IEEE 41st International Conference on Distributed Computing Systems (ICDCS) , Apr 2021

   Abs Bib PDF

   Cross-technology interference is a major threat to the dependability of low-power wireless communications. Due to power and bandwidth asymmetries, technologies such as Wi-Fi tend to dominate the RF channel and unintentionally destroy low-power wireless communications from resource-constrained technologies such as ZigBee, leading to severe coexistence issues. To address these issues, existing schemes make ZigBee nodes individually assess the RF channel’s availability or let Wi-Fi appliances blindly reserve the medium for the transmissions of low-power devices. Without a two-way interaction between devices making use of different wireless technologies, these approaches have limited scenarios or achieve inefficient network performance. This paper presents BiCord, a bidirectional coordination scheme in which resource-constrained wireless devices such as ZigBee nodes and powerful Wi-Fi appliances coordinate their activities to increase coexistence and enhance network performance. Specifically, in BiCord, ZigBee nodes directly request channel resources from Wi-Fi devices, who then reserve the channel for ZigBee transmissions on-demand. This interaction continues until the transmission requirement of ZigBee nodes is both fulfilled and understood by Wi-Fi devices. This way, BiCord avoids unnecessary channel allocations, maximizes the availability of the spectrum, and minimizes transmission delays. We evaluate BiCord on off-the-shelf Wi-Fi and ZigBee devices, demonstrating its effectiveness experimentally. Among others, our results show that BiCord increases channel utilization by up to 50.6% and reduces the average transmission delay of ZigBee nodes by 84.2% compared to state-of-the-art approaches.

   @inproceedings{9546454,
     author = {Yu, Zihao and Li, Pengyu and Boano, Carlo Alberto and He, Yuan and Jin, Meng and Guo, Xiuzhen and Zheng, Xiaolong},
     booktitle = {2021 IEEE 41st International Conference on Distributed Computing Systems (ICDCS)},
     title = {BiCord: Bidirectional Coordination among Coexisting Wireless Devices},
     year = {2021},
     volume = {},
     number = {},
     pages = {304-314},
     keywords = {Wireless communication;Performance evaluation;Radio frequency;Zigbee;Interference;White spaces;Delays;Coexistence;Cross-technology interference;Cross-technology communication;Device coordination},
     doi = {10.1109/ICDCS51616.2021.00037},
   }

2020

1. SenSys’20

   Aloba: rethinking ON-OFF keying modulation for ambient LoRa backscatter

   Xiuzhen Guo, Longfei Shangguan , Yuan He , and 4 more authors

   In Proceedings of the 18th Conference on Embedded Networked Sensor Systems , Apr 2020

   Abs Bib PDF

   Backscatter communication holds potential for ubiquitous and low-cost connectivity among low-power IoT devices. To avoid interference between the carrier signal and the backscatter signal, recent works propose a frequency-shifting technique to separate these two signals in the frequency domain. Such proposals, however, have to occupy the precious wireless spectrum that is already overcrowded, and increase the power, cost, and complexity of the backscatter tag. In this paper, we revisit the classic ON-OFF Keying (OOK) modulation and propose Aloba, a backscatter system that takes the ambient LoRa transmissions as the excitation and piggybacks the in-band OOK modulated signals over the LoRa transmissions. Our design enables the backsactter signal to work in the same frequency band of the carrier signal, meanwhile achieving good tradeoff between transmission range and link throughput. The key contributions of Aloba include: i) the design of a low-power backscatter tag that can pick up the ambient LoRa signals from other signals; ii) a novel decoding algorithm to demodulate both the carrier signal and the backscatter signal from their superposition. The design of Aloba completely unleashes the backscatter tag’s ability in OOK modulation and achieves flexible data rate at different transmission range. We implement Aloba and conduct head-to-head comparison with the state-of-the-art LoRa backscatter system PLoRa in various settings. The experiment results show Aloba can achieve 39.5–199.4 Kbps data rate at various distances, 10.4–52.4X higher than PLoRa.

   @inproceedings{10.1145/3384419.3430719,
     author = {Guo, Xiuzhen and Shangguan, Longfei and He, Yuan and Zhang, Jia and Jiang, Haotian and Siddiqi, Awais Ahmad and Liu, Yunhao},
     title = {Aloba: rethinking ON-OFF keying modulation for ambient LoRa backscatter},
     year = {2020},
     isbn = {9781450375900},
     publisher = {Association for Computing Machinery},
     address = {New York, NY, USA},
     url = {https://doi.org/10.1145/3384419.3430719},
     doi = {10.1145/3384419.3430719},
     booktitle = {Proceedings of the 18th Conference on Embedded Networked Sensor Systems},
     pages = {192–204},
     numpages = {13},
     keywords = {on-off keying modulation, ambient lora backscatter},
     location = {Virtual Event, Japan},
     series = {SenSys '20},
   }

2. ToN’20

   WiZig: Cross-Technology Energy Communication Over a Noisy Channel

   Xiuzhen Guo, Yuan He , and Xiaolong Zheng

   IEEE/ACM Transactions on Networking, Apr 2020

   Abs Bib PDF

   The proliferation of IoT applications brings the demand of ubiquitous connections among heterogeneous wireless devices. Cross-Technology Communication (CTC) is a significant technique to directly exchange data among heterogeneous devices that follow different standards. By exploiting a side-channel like frequency, amplitude, or temporal modulation, the existing works enable CTC but have limited performance under channel noise. In this article, we propose WiZig, a novel CTC technique from WiFi to ZigBee that employs modulations in both the amplitude and temporal dimensions to optimize the throughput over a noisy channel. We establish a theoretical model of the energy communication channel to clearly understand the channel capacity. We then devise an online rate adaptation algorithm to adjust the modulation strategy according to the channel condition. Based on the theoretical model, WiZig controls the number of encoded energy amplitudes and the length of a receiving window, so as to optimize the CTC throughput. We implement a prototype of WiZig on a software radio platform and a commercial ZigBee device. The evaluation shows that WiZig achieves a throughput of 153.85bps with less than 1% symbol error rate in a real environment.

   @article{9177325,
     author = {Guo, Xiuzhen and He, Yuan and Zheng, Xiaolong},
     journal = {IEEE/ACM Transactions on Networking},
     title = {WiZig: Cross-Technology Energy Communication Over a Noisy Channel},
     year = {2020},
     volume = {28},
     number = {6},
     pages = {2449-2460},
     keywords = {Signal to noise ratio;ZigBee;Energy states;Wireless fidelity;Bit error rate;Wireless communication;Noise measurement;Wireless communication;cross-technology;protocol},
     doi = {10.1109/TNET.2020.3013921},
   }

3. ToN’20

   ZigFi: Harnessing Channel State Information for Cross-Technology Communication

   Xiuzhen Guo, Yuan He , Xiaolong Zheng , and 2 more authors

   IEEE/ACM Transactions on Networking, Apr 2020

   Abs Bib PDF

   Cross-technology communication (CTC) is a technique that enables direct communication among different wireless technologies. Recent works in this area have made substantial progress, but CTC from ZigBee to WiFi remains an open problem. In this paper, we propose ZigFi, a novel CTC framework that enables communication from ZigBee to WiFi. ZigFi carefully overlaps ZigBee packets with WiFi packets. Through experiments we show that Channel State Information (CSI) of the overlapped packets can be used to convey data from ZigBee to WiFi. Based on this finding, we propose a receiver-initiated protocol and translate the decoding problem into a problem of CSI classification with Support Vector Machine. We further build a generic model through experiments, which describes the relationship between the Signal to Interference and Noise Ratio (SINR) and the symbol error rate (SER). Moreover, we extend ZigFi to multiple-to-one concurrent transmissions. We implement ZigFi on commercial-off-the-shelf WiFi and ZigBee devices. We evaluate the performance of ZigFi under different experimental settings. The results demonstrate that ZigFi achieves a throughput of 215.9bps, which is 18X faster than the state of the arts.

   @article{8970452,
     author = {Guo, Xiuzhen and He, Yuan and Zheng, Xiaolong and Yu, Liangcheng and Gnawali, Omprakash},
     journal = {IEEE/ACM Transactions on Networking},
     title = {ZigFi: Harnessing Channel State Information for Cross-Technology Communication},
     year = {2020},
     volume = {28},
     number = {1},
     pages = {301-311},
     keywords = {Zigbee;Wireless fidelity;Interference;Wireless communication;Receivers;Throughput;Protocols;Cross-technology;ZigBee to WiFi;Channel State Information},
     doi = {10.1109/TNET.2019.2962707},
   }

4. INFOCOM’20

   Link Quality Estimation of Cross-Technology Communication

   Jia Zhang , Xiuzhen Guo, Haotian Jiang , and 2 more authors

   In IEEE INFOCOM 2020 - IEEE Conference on Computer Communications , Apr 2020

   Abs Bib PDF

   Research on Cross-technology communication (CTC) has made rapid progress in recent years, but how to estimate the quality of a CTC link remains an open and challenging problem. Through our observation and study, we find that none of the existing approaches can be applied to estimate the link quality of CTC. Built upon the physical-level emulation, transmission over a CTC link is jointly affected by two factors: the emulation error and the channel distortion. We in this paper propose a new link metric called C-LQI and a joint link model that simultaneously takes into account the emulation error and the channel distortion in the process of CTC. We further design a light-weight link estimation approach to estimate C-LQI and in turn the PRR over the CTC link. We implement C-LQI and compare it with two representative link estimation approaches. The results demonstrate that C-LQI reduces the relative error of link estimation respectively by 46% and 53% and saves the communication cost by 90%.

   @inproceedings{9155437,
     author = {Zhang, Jia and Guo, Xiuzhen and Jiang, Haotian and Zheng, Xiaolong and He, Yuan},
     booktitle = {IEEE INFOCOM 2020 - IEEE Conference on Computer Communications},
     title = {Link Quality Estimation of Cross-Technology Communication},
     year = {2020},
     volume = {},
     number = {},
     pages = {496-505},
     keywords = {Emulation;Distortion;Receivers;Measurement;ZigBee;Estimation;Wireless communication;cross technology communication;link quality estimation},
     doi = {10.1109/INFOCOM41043.2020.9155437},
   }

5. MobiHoc 2020

   Link Quality Estimation of Cross Technology Communication

   Xiaolong Zheng , Dan Xia , Xiuzhen Guo, and 3 more authors

   MobiHoc, Apr 2020

2019

1. IPSN’19

   WIDE: Physical-level CTC via Digital Emulation

   Xiuzhen Guo, Yuan He , Jia Zhang , and 1 more author

   In 2019 18th ACM/IEEE International Conference on Information Processing in Sensor Networks (IPSN) , Apr 2019

   Abs Bib PDF

   Cross-Technology Communication (CTC) is an emerging technique that enables direct communication across different wireless technologies. Recent works achieve physical-level CTC by emulating the standard time-domain waveform of the receiver. This method faces the challenges of inherent unreliability due to the imperfect emulation. Different from analog emulation, we propose a novel concept named digital emulation, which stems from the following insight: The receiver relies on the phase shift to decode symbols rather than the shape of analog time-domain waveform. There are lots of phase sequences which satisfy the requirement of phase shift. The distortions of these phase sequences after WiFi emulation are different. We have the opportunity to select an appropriate phase sequence with the relatively small emulation errors to achieve a reliable CTC. The key point of digital emulation is generic and applicable to a set of CTCs, where the transmitter has a wider bandwidth for emulation and the receiver decoding is based on the phase shift. In this paper, we implement our proposal as WIDE, a physical-level CTC via digital emulation from WiFi to ZigBee. We conduct extensive experiments to evaluate the performance of WIDE. The results show that WIDE significantly improves the Packet Reception Ratio (PRR) from 41.7% to 86.2%, which is 2× of WEBee’s, an existing representative physical-level CTC.

   @inproceedings{8732556,
     author = {Guo, Xiuzhen and He, Yuan and Zhang, Jia and Jiang, Haotian},
     booktitle = {2019 18th ACM/IEEE International Conference on Information Processing in Sensor Networks (IPSN)},
     title = {WIDE: Physical-level CTC via Digital Emulation},
     year = {2019},
     volume = {},
     number = {},
     pages = {49-60},
     keywords = {Emulation;Zigbee;Wireless fidelity;Receivers;Standards;Reliability;Payloads;Cross-Technology Communication;Digital emulation},
     doi = {10.1145/3302506.3310388},
   }

2. INFOCOM’19

   LEGO-Fi: Transmitter-Transparent CTC with Cross-Demapping

   Xiuzhen Guo, Yuan He , Xiaolong Zheng , and 2 more authors

   In IEEE INFOCOM 2019 - IEEE Conference on Computer Communications , Apr 2019

   Abs Bib PDF

   Cross-Technology Communication (CTC) is an emerging technique that enables direct communication across different wireless technologies. The state-of-the-art works in this area propose physical-level CTC, in which the transmitters emulate signals that follow the receiver’s standard. Physical-level CTC means considerable processing complexity at the transmitter, which doesn’t apply to the communication from a low-end transmitter to a high-end receiver, e.g. from ZigBee to WiFi. This paper presents transmitter-transparent cross-technology communication, which leaves the processing complexity solely at the receiver side and therefore makes a critical advance toward bidirectional high-throughput CTC. We implement our proposal as LEGO-Fi, the communication from ZigBee to WiFi. The key technique inside is cross-demapping, which stems from two key technical insights: (1) A ZigBee packet leaves distinguishable features when passing the WiFi modules. (2) Compared to ZigBee’s simple encoding and modulation schemes, the rich processing capacity of WiFi offers extra flexibility to process a ZigBee packet. The evaluation results show that LEGO-Fi achieves a throughput of 213.6Kbps, which is respectively 13000× and 1200× faster than FreeBee and ZigFi, the two existing ZigBee-to-WiFi CTC approaches.

   @inproceedings{8737659,
     author = {Guo, Xiuzhen and He, Yuan and Zheng, Xiaolong and Yu, Zihao and Liu, Yunhao},
     booktitle = {IEEE INFOCOM 2019 - IEEE Conference on Computer Communications},
     title = {LEGO-Fi: Transmitter-Transparent CTC with Cross-Demapping},
     year = {2019},
     volume = {},
     number = {},
     pages = {2125-2133},
     keywords = {Zigbee;Wireless fidelity;Receivers;Synchronization;Throughput;Wireless communication;Standards},
     doi = {10.1109/INFOCOM.2019.8737659},
   }

3. EWSN 2019

   Cross Technology Communication in Heterogeneous Wireless Networks

   Xiuzhen Guo

   EWSN, Apr 2019

   Abs PDF

   The proliferation of IoT applications brings the demand of ubiquitous connections among heterogeneous wireless devices. Cross-Technology Communication (CTC) is a significant technique to directly exchange data among heterogeneous devices that follow different standards. We focus on achieving the packet-level CTC and the physical-level CTC between WiFi and ZigBee.

4. SECON’19

   AdaComm: Tracing Channel Dynamics for Reliable Cross-Technology Communication

   Weiguo Wang , Xiaolong Zheng , Yuan He , and 1 more author

   In 2019 16th Annual IEEE International Conference on Sensing, Communication, and Networking (SECON) , Apr 2019

   Abs Bib PDF

   Cross-Technology Communication (CTC) is an emerging technology to support direct communication between wireless devices that follow different standards. In spite of the many different proposals from the community to enable CTC, the performance aspect of CTC is an equally important problem but has seldom been studied before. We find this problem is extremely challenging, due to the following reasons: on one hand, a link for CTC is essentially different from a conventional wireless link. The conventional link indicators like RSSI (received signal strength indicator) and SNR (signal to noise ratio) cannot be used to directly characterize a CTC link. On the other hand, the indirect indicators like PER (packet error rate), which is adopted by many existing CTC proposals, cannot capture the short-term link behavior. As a result, the existing CTC proposals fail to keep reliable performance under dynamic channel conditions. In order to address the above challenge, we in this paper propose AdaComm, a generic framework to achieve self-adaptive CTC in dynamic channels. Instead of reactively adjusting the CTC sender, AdaComm adopts online learning mechanism to adaptively adjust the decoding model at the CTC receiver. The self-adaptive decoding model automatically learns the effective features directly from the raw received signals that are embedded with the current channel state. With the lossless channel information, AdaComm further adopts the fine tuning and full training modes to cope with the continuous and abrupt channel dynamics. We implement AdaComm and integrate it with two existing CTC approaches that respectively employ CSI (channel state information) and RSSI as the information carrier. The evaluation results demonstrate that AdaComm can significantly reduce the SER (symbol error rate) by 72.9% and 49.2%, respectively, compared with the existing approaches.

   @inproceedings{8824843,
     author = {Wang, Weiguo and Zheng, Xiaolong and He, Yuan and Guo, Xiuzhen},
     booktitle = {2019 16th Annual IEEE International Conference on Sensing, Communication, and Networking (SECON)},
     title = {AdaComm: Tracing Channel Dynamics for Reliable Cross-Technology Communication},
     year = {2019},
     volume = {},
     number = {},
     pages = {1-9},
     keywords = {Decoding;Training;Zigbee;Wireless fidelity;Reliability;Adaptation models;Receivers},
     doi = {10.1109/SAHCN.2019.8824843},
   }

2018

1. INFOCOM’18

   ZIGFI: Harnessing Channel State Information for Cross-Technology Communication

   Xiuzhen Guo, Yuan He , Xiaolong Zheng , and 2 more authors

   In IEEE INFOCOM 2018 - IEEE Conference on Computer Communications , Apr 2018

   Abs Bib PDF

   Cross-technology communication (CTC) is a technique that enables direct communication among different wireless technologies. Recent works in this area have made positive progress, but high-throughput CTC from ZigBee to WiFi remains an open problem. In this paper, we propose ZigFi, a novel CTC framework that enables direct communication from ZigBee to WiFi. Without impacting the ongoing WiFi transmissions, ZigFi carefully overlaps ZigBee packets with WiFi packets. Through experiments we show that Channel State Information (CSI) of the overlapped packets can be used to convey data from ZigBee to WiFi. Based on this finding, we propose a receiver-initiated protocol and translate the decoding problem into a problem of CSI classification with Support Vector Machine. We further build a generic model through experiments, which describes the relationship between the Signal to Interference and Noise Ratio (SINR) and the symbol error rate (SER). We implement ZigFi on commercial-off-the-shelf WiFi and ZigBee devices. We evaluate the performance of ZigFi under different experimental settings. The results demonstrate that ZigFi achieves a throughput of 215.9bps, which is 18X faster than the state-of-the-art.

   @inproceedings{8486364,
     author = {Guo, Xiuzhen and He, Yuan and Zheng, Xiaolong and Yu, Liangcheng and Gnawali, Omprakash},
     booktitle = {IEEE INFOCOM 2018 - IEEE Conference on Computer Communications},
     title = {ZIGFI: Harnessing Channel State Information for Cross-Technology Communication},
     year = {2018},
     volume = {},
     number = {},
     pages = {360-368},
     keywords = {ZigBee;Wireless fidelity;Wireless communication;Throughput;Interference;Bandwidth;Conferences},
     doi = {10.1109/INFOCOM.2018.8486364},
   }

2. INFOCOM’18

   StripComm: Interference-Resilient Cross-Technology Communication in Coexisting Environments

   Xiaolong Zheng , Yuan He , and Xiuzhen Guo

   In IEEE INFOCOM 2018 - IEEE Conference on Computer Communications , Apr 2018

   Abs Bib PDF

   Cross- Technology Communication (CTC) is an emerging technique to enable the direct communication among different wireless technologies. A main category of the existing proposals on CTC propose to modulate packets at the sender side, and demodulate them into 1 and 0 bits at the receiver side. The performance of those proposals is likely to degrade in a densely coexisting environment. Solely judged according to the received signal strength, a symbol 0 that is modulated as packet absence is generally indistinguishable from dynamic interference. In this paper, we propose StripComm, interference-resilient CTC in coexisting environments. A sender in StripComm adopts an interference-resilient coding scheme that contains both presence and absence of packets in one symbol. The receiver strips the interference from the interested signal by exploiting the self-similarity of StripComm signals. We prototype StripComm with commercial WiFi, ZigBee devices and a software radio platform. The theoretical and experimental evaluation demonstrate that StripComm offers a data rate up to 1.1K bps with a SER (Symbol Error Rate) lower than 0.01 and a data rate of 0.89K bps even against strong interference.

   @inproceedings{8486374,
     author = {Zheng, Xiaolong and He, Yuan and Guo, Xiuzhen},
     booktitle = {IEEE INFOCOM 2018 - IEEE Conference on Computer Communications},
     title = {StripComm: Interference-Resilient Cross-Technology Communication in Coexisting Environments},
     year = {2018},
     volume = {},
     number = {},
     pages = {171-179},
     keywords = {Interference;Wireless fidelity;Receivers;ZigBee;Wireless communication;Encoding;Signal to noise ratio},
     doi = {10.1109/INFOCOM.2018.8486374},
     issn = {},
     month = apr,
     address = {Honolulu, HI, USA},
   }

3. EWSN’18

   Crocs: Cross-Technology Clock Synchronization for WiFi and ZigBee

   Zihao Yu , Chengkun Jiang , Yuan He , and 2 more authors

   In Proceedings of the 2018 International Conference on Embedded Wireless Systems and Networks , Apr 2018

   Abs Bib PDF

   Clock synchronization is a key function in embedded wireless systems and networks. This issue is equally important and more challenging in IoT systems nowadays, which often include heterogeneous wireless devices that follow different wireless standards. Conventional solutions to this problem employ gateway-based indirect synchronization, which suffer low accuracy. This paper for the first time studies the problem of cross-technology clock synchronization. Our proposal called Crocs synchronizes WiFi and ZigBee devices by direct cross-technology communication. Crocs decouples the synchronization signal from the transmission of a timestamp. By incorporating a barker-code based beacon for time alignment and cross-technology transmission of timestamps, Crocs achieves robust and accurate synchronization among WiFi and ZigBee devices, with the synchronization error lower than 1 millisecond. We further make attempts to implement different cross-technology communication methods in Crocs and provide insight findings with regard to the achievable accuracy and expected overhead.

   @inproceedings{10.5555/3234847.3234865,
     author = {Yu, Zihao and Jiang, Chengkun and He, Yuan and Zheng, Xiaolong and Guo, Xiuzhen},
     title = {Crocs: Cross-Technology Clock Synchronization for WiFi and ZigBee},
     year = {2018},
     isbn = {9780994988621},
     publisher = {Junction Publishing},
     address = {Madrid, Spain},
     booktitle = {Proceedings of the 2018 International Conference on Embedded Wireless Systems and Networks},
     pages = {135--144},
     numpages = {10},
     keywords = {Cross technology communication, Clock synchronization},
     location = {Madrid, Spain},
     series = {EWSN '18},
   }

2017

1. INFOCOM’17

   WiZig: Cross-technology energy communication over a noisy channel

   Xiuzhen Guo, Xiaolong Zheng , and Yuan He

   In IEEE INFOCOM 2017 - IEEE Conference on Computer Communications , Apr 2017

   Abs Bib PDF

   The proliferation of loT applications drives the need of ubiquitous connections among heterogeneous wireless devices. Cross-Technology Communication (CTC) is a significant technique to directly exchange information among heterogeneous devices that follow different standards. By exploiting a side-channel like frequency, amplitude or temporal modulation, the existing works enable CTC but have limited performance under channel noise. In this paper, we propose WiZig, a novel CTC technique that employs modulation techniques in both the amplitude and temporal dimensions to optimize the throughput over a noisy channel. We establish a theoretical model of the energy communication channel to clearly understand the channel capacity. We then devise an online rate adaptation algorithm to adjust the modulation strategy according to the channel condition. Based on the theoretical model, WiZig can accurately control the number of encoded energy amplitudes and the length of a receiving window, so as to optimize the CTC throughput. We implement a prototype of WiZig on a software radio platform and a commercial ZigBee device. The evaluation show that WiZig achieves a throughput of 153.85 bps with less than 1 % symbol error rate in a real environment. The results demonstrate that WiZig realizes efficient and reliable CTC under varied channel conditions.

   @inproceedings{8057108,
     author = {Guo, Xiuzhen and Zheng, Xiaolong and He, Yuan},
     booktitle = {IEEE INFOCOM 2017 - IEEE Conference on Computer Communications},
     title = {WiZig: Cross-technology energy communication over a noisy channel},
     year = {2017},
     volume = {},
     number = {},
     pages = {1-9},
     keywords = {Receivers;Wireless communication;Throughput;Error analysis;Noise measurement;Wireless sensor networks;Modulation},
     doi = {10.1109/INFOCOM.2017.8057108},
   }

2016

1. MSN’16

   Error Scene Restoration with Runtime Logs of Wireless Sensor Networks

   Shuo Lian , Xiuzhen Guo, Zhenge Guo , and 1 more author

   In 2016 12th International Conference on Mobile Ad-Hoc and Sensor Networks (MSN) , Dec 2016

   Abs Bib PDF

   The application of Wireless Sensor Networks (WSNs) often falls into unexpected poor performance conditions due to many factors such as complex network interactions, software bugs and incorrect configurations. Diagnosing such a network is challenging since it is difficult to obtain information from the network due to factors including (1) non-deterministic network interactions among motes, (2) difficulties in reconstructing the status of each individual mote, and (3) unavailability of the real environment information. To address these problems, we propose a diagnosis tool called ALog which analyzes the local logs and the source code to infer what happens in network. Based on the analysis, we further derive the states and possible problems accordingly. We implement ALog and evaluate its efficiency with two real case studies. The results demonstrate that ALog is accurate and applicable for diagnosing real sensor networks.

   @inproceedings{7950252,
     author = {Lian, Shuo and Guo, Xiuzhen and Guo, Zhenge and Zhao, Xu},
     booktitle = {2016 12th International Conference on Mobile Ad-Hoc and Sensor Networks (MSN)},
     title = {Error Scene Restoration with Runtime Logs of Wireless Sensor Networks},
     year = {2016},
     volume = {},
     number = {},
     pages = {320-324},
     keywords = {Wireless sensor networks;Context;Flow graphs;Software;Runtime;Tools;Radiation detectors;Wireless Sensor Networks;Error Diagnose;Log},
     doi = {10.1109/MSN.2016.058},
     issn = {},
     month = dec,
     address = {Hefei, China},
   }

2015

1. Sensors

   A Novel Feature Extraction Approach Using Window Function Capturing and QPSO-SVM for Enhancing Electronic Nose Performance

   Xiuzhen Guo, Chao Peng , Songlin Zhang , and 5 more authors

   Sensors, Jun 2015

   Abs Bib PDF

   In this paper, a novel feature extraction approach which can be referred to as moving window function capturing (MWFC) has been proposed to analyze signals of an electronic nose (E-nose) used for detecting types of infectious pathogens in rat wounds. Meanwhile, a quantum-behaved particle swarm optimization (QPSO) algorithm is implemented in conjunction with support vector machine (SVM) for realizing a synchronization optimization of the sensor array and SVM model parameters. The results prove the efficacy of the proposed method for E-nose feature extraction, which can lead to a higher classification accuracy rate compared to other established techniques. Meanwhile it is interesting to note that different classification results can be obtained by changing the types, widths or positions of windows. By selecting the optimum window function for the sensor response, the performance of an E-nose can be enhanced.

   @article{s150715198,
     author = {Guo, Xiuzhen and Peng, Chao and Zhang, Songlin and Yan, Jia and Duan, Shukai and Wang, Lidan and Jia, Pengfei and Tian, Fengchun},
     title = {A Novel Feature Extraction Approach Using Window Function Capturing and QPSO-SVM for Enhancing Electronic Nose Performance},
     journal = {Sensors},
     volume = {15},
     year = {2015},
     number = {7},
     pages = {15198--15217},
     url = {https://www.mdpi.com/1424-8220/15/7/15198},
     pubmedid = {26131672},
     issn = {1424-8220},
     doi = {10.3390/s150715198},
     month = jun,
   }

2. Sensors

   Electronic Nose Feature Extraction Methods: A Review

   Jia Yan , Xiuzhen Guo, Shukai Duan , and 4 more authors

   Sensors, Nov 2015

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   Many research groups in academia and industry are focusing on the performance improvement of electronic nose (E-nose) systems mainly involving three optimizations, which are sensitive material selection and sensor array optimization, enhanced feature extraction methods and pattern recognition method selection. For a specific application, the feature extraction method is a basic part of these three optimizations and a key point in E-nose system performance improvement. The aim of a feature extraction method is to extract robust information from the sensor response with less redundancy to ensure the effectiveness of the subsequent pattern recognition algorithm. Many kinds of feature extraction methods have been used in E-nose applications, such as extraction from the original response curves, curve fitting parameters, transform domains, phase space (PS) and dynamic moments (DM), parallel factor analysis (PARAFAC), energy vector (EV), power density spectrum (PSD), window time slicing (WTS) and moving window time slicing (MWTS), moving window function capture (MWFC), etc. The object of this review is to provide a summary of the various feature extraction methods used in E-noses in recent years, as well as to give some suggestions and new inspiration to propose more effective feature extraction methods for the development of E-nose technology.

   @article{s151127804,
     author = {Yan, Jia and Guo, Xiuzhen and Duan, Shukai and Jia, Pengfei and Wang, Lidan and Peng, Chao and Zhang, Songlin},
     title = {Electronic Nose Feature Extraction Methods: A Review},
     journal = {Sensors},
     volume = {15},
     year = {2015},
     number = {11},
     pages = {27804--27831},
     url = {https://www.mdpi.com/1424-8220/15/11/27804},
     pubmedid = {26540056},
     issn = {1424-8220},
     doi = {10.3390/s151127804},
     month = nov,
   }