RF-ECG:Heart Rate Variability Assessment Based on COTS RFID Tag Array CHUYU WANG,Nanjing University,CHN LEI XIE*,Nanjing University,CHN WEI WANG,Nanjing University,CHN YINGYING CHEN,Rutgers University,USA YANLING BU,Nanjing University,CHN SANGLU LU,Nanjing University,CHN As an important indicator of autonomic regulation for circulatory function,Heart Rate Variability(HRV)is widely used for general health evaluation.Apart from using dedicated devices(e.g.ECG)in a wired manner,current methods search for a ubiquitous manner by either using wearable devices,which suffer from low accuracy and limited battery life,or applying wireless techniques(e.g..FMCW),which usually utilize dedicated devices(e.g.,USRP)for the measurement.To address these issues,we present RF-ECG based on Commercial-Off-The-Shelf(COTS)RFID,a wireless approach to sense the human heartbeat through an RFID tag array attached on the chest area in the clothes.In particular,as the RFID reader continuously interrogates the tag array,two main effects are captured by the tag array:the reflection effect representing the RF-signal reflected from the heart movement due to heartbeat;the moving effect representing the tag movement caused by chest movement due to respiration.To extract the reflection signal from the noisy RF-signals,we develop a mechanism to capture the RF-signal variation of the tag array caused by the moving effect,aiming to eliminate the signals related to respiration. To estimate the HRV from the reflection signal,we propose a signal reflection model to depict the relationship between the 85 RF-signal variation from the tag array and the reflection effect associated with the heartbeat.A fusing technique is developed to combine multiple reflection signals from the tag array for accurate estimation of HRV.Experiments with 15 volunteers show that RF-ECG can achieve a median error of 3%of Inter-Beat Interval(IBI),which is comparable to existing wired techniques. CCS Concepts:.Networks-Sensor networks;Mobile networks;.Human-centered computing-Mobile devices; Additional Key Words and Phrases:RFID:Heart rate:HRV ACM Reference Format: Chuyu Wang,Lei Xie,Wei Wang.Yingying Chen,Yanling Bu,and Sanglu Lu.2018.RF-ECG:Heart Rate Variability Assessment Based on COTS RFID Tag Array.Proc.ACM Interact.Mob.Wearable Ubiquitous Technol.2,2,Article 85 (June 2018),26 pages. https:/doiorg/10.1145/3214288 "Lei Xie is the corresponding author,Email:Ixie@nju.edu.cn. Authors'addresses:Chuyu Wang,wangcyu217@dislab.nju.edu.cn,Nanjing University,State Key Laboratory for Novel Software Technology, 163 Xianlin Ave,Nanjing,210046,CHN;Lei Xie,Ixie@nju.edu.cn,Nanjing University,State Key Laboratory for Novel Software Technology, 163 Xianlin Ave,Nanjing,210046,CHN;Wei Wang,Nanjing University,State Key Laboratory for Novel Software Technology,163 Xianlin Ave,Nanjing.210046,CHN:Yingying Chen,Rutgers University,WINLAB,North Brunswick,NJ,08902,USA;Yanling Bu,Nanjing University. State Key Laboratory for Novel Software Technology,163 Xianlin Ave,Nanjing,210046,CHN;Sanglu Lu,Nanjing University,State Key Laboratory for Novel Software Technology,163 Xianlin Ave,Nanjing.210046.CHN. Permission to make digital or hard copies of all or part of this work for personal or classroom use is granted without fee provided that copies are not made or distributed for profit or commercial advantage and that copies bear this notice and the full citation on the first page.Copyrights for components of this work owned by others than ACM must be honored.Abstracting with credit is permitted.To copy otherwise,or republish,to post on servers or to redistribute to lists,requires prior specific permission and/or a fee.Request permissions from permissions@acm.org. 2018 Association for Computing Machinery. 2474-9567/2018/6-ART85$15.00 https:/doi.org/10.1145/3214288 Proc.ACM Interact.Mob.Wearable Ubiquitous Technol,Vol.2,No.2,Article 85.Publication date:June 2018.85 RF-ECG: Heart Rate Variability Assessment Based on COTS RFID Tag Array CHUYU WANG, Nanjing University, CHN LEI XIE∗ , Nanjing University, CHN WEI WANG, Nanjing University, CHN YINGYING CHEN, Rutgers University, USA YANLING BU, Nanjing University, CHN SANGLU LU, Nanjing University, CHN As an important indicator of autonomic regulation for circulatory function, Heart Rate Variability (HRV) is widely used for general health evaluation. Apart from using dedicated devices (e.g, ECG) in a wired manner, current methods search for a ubiquitous manner by either using wearable devices, which suffer from low accuracy and limited battery life, or applying wireless techniques (e.g., FMCW), which usually utilize dedicated devices (e.g., USRP) for the measurement. To address these issues, we present RF-ECG based on Commercial-Off-The-Shelf (COTS) RFID, a wireless approach to sense the human heartbeat through an RFID tag array attached on the chest area in the clothes. In particular, as the RFID reader continuously interrogates the tag array, two main effects are captured by the tag array: the reflection effect representing the RF-signal reflected from the heart movement due to heartbeat; the moving effect representing the tag movement caused by chest movement due to respiration. To extract the reflection signal from the noisy RF-signals, we develop a mechanism to capture the RF-signal variation of the tag array caused by the moving effect, aiming to eliminate the signals related to respiration. To estimate the HRV from the reflection signal, we propose a signal reflection model to depict the relationship between the RF-signal variation from the tag array and the reflection effect associated with the heartbeat. A fusing technique is developed to combine multiple reflection signals from the tag array for accurate estimation of HRV. Experiments with 15 volunteers show that RF-ECG can achieve a median error of 3% of Inter-Beat Interval (IBI), which is comparable to existing wired techniques. CCS Concepts: • Networks → Sensor networks; Mobile networks; • Human-centered computing → Mobile devices; Additional Key Words and Phrases: RFID; Heart rate; HRV ACM Reference Format: Chuyu Wang, Lei Xie, Wei Wang, Yingying Chen, Yanling Bu, and Sanglu Lu. 2018. RF-ECG: Heart Rate Variability Assessment Based on COTS RFID Tag Array. Proc. ACM Interact. Mob. Wearable Ubiquitous Technol. 2, 2, Article 85 (June 2018), 26 pages. https://doi.org/10.1145/3214288 ∗Lei Xie is the corresponding author, Email: lxie@nju.edu.cn. Authors’ addresses: Chuyu Wang, wangcyu217@dislab.nju.edu.cn, Nanjing University, State Key Laboratory for Novel Software Technology, 163 Xianlin Ave, Nanjing, 210046, CHN; Lei Xie, lxie@nju.edu.cn, Nanjing University, State Key Laboratory for Novel Software Technology, 163 Xianlin Ave, Nanjing, 210046, CHN; Wei Wang, Nanjing University, State Key Laboratory for Novel Software Technology, 163 Xianlin Ave, Nanjing, 210046, CHN; Yingying Chen, Rutgers University, WINLAB, North Brunswick, NJ, 08902, USA; Yanling Bu, Nanjing University, State Key Laboratory for Novel Software Technology, 163 Xianlin Ave, Nanjing, 210046, CHN; Sanglu Lu, Nanjing University, State Key Laboratory for Novel Software Technology, 163 Xianlin Ave, Nanjing, 210046, CHN. Permission to make digital or hard copies of all or part of this work for personal or classroom use is granted without fee provided that copies are not made or distributed for profit or commercial advantage and that copies bear this notice and the full citation on the first page. Copyrights for components of this work owned by others than ACM must be honored. Abstracting with credit is permitted. To copy otherwise, or republish, to post on servers or to redistribute to lists, requires prior specific permission and/or a fee. Request permissions from permissions@acm.org. © 2018 Association for Computing Machinery. 2474-9567/2018/6-ART85 $15.00 https://doi.org/10.1145/3214288 Proc. ACM Interact. Mob. Wearable Ubiquitous Technol., Vol. 2, No. 2, Article 85. Publication date: June 2018