Activating Wireless Voice for E-Toll Collection Systems with Zero Start-up Cost Zhenlin An*,Qiongzheng Lin*,Lei Yang*and Lei Xiet *Department of Computing,The Hong Kong Polytechnic University,Hong Kong fState Key Laboratory for Novel Software Technology,Nanjing University,China Email:*fan,lin,young}@tagsys.org,TIxie@nju.edu.cn Abstract-This work enhances the machine-to-human commu- nication between electronic toll collection (ETC)systems and drivers by providing an AM broadcast service to deployed ETC systems.This study is the first to show that ultra-high radio frequency identification signals can be received by an AM radio receiver due to the presence of the nonlinearity effect in the AM receiver.Such a phenomenon allows the development of a previously infeasible cross-technology and cross-frequency communication,called Tagcaster,which converts an ETC reader to an AM station for broadcasting short messages (e.g.,charged- fees and traffic forecast)to drivers at tollbooths.The key innovation in this work is the engineering of Tagcaster over 2Rp》 ④isening off-the-shelf ETC systems using shadow carrier and baseband Fig.1:Tagcaster-enhanced wireless voice service for ETC system. whitening without the need for hardware nor firmware changes This feature allows zero-cost rapid deployment in existing ETC 1 The ETC reader queries the transponder attached on the vehicle.2 infrastructure.Two prototypes of Tagcaster are designed,imple- The transponder is identified through its reply.Tagcaster broadcasts mented and evaluated over four general and five vehicle-mounted the wireless voice to the identified vehicle.The driver can listen AM receivers (e.g.,Toyota,Audi,and Jetta).Experiments reveal to the AM radio through the vehicle-mounted radio receiver. that Tagcaster can provide good-quality (PESQ>2)and stable AM broadcasting service with a 30 m coverage range.Tagcaster credit balance,real-time traffic and road condition).Achiev- remarkably improves user experience at ETC stations and two- ing direct machine-to-human (M2H)communication between thirds volunteer drivers rate it with a score of 4+out of 5. drivers and ETC systems requires extra peripherals and efforts. For example,drivers must slow down their cars to view an I.INTRODUCTION LED screen installed at the tollbooth for charge details.The Electronic toll collection(ETC)is a system enabling elec- information acquired by drivers is usually quite limited due to tronic collection of toll payments,thus allowing for near- the small screen size.Slowing down also worsens the conges- nonstop toll collection and traffic monitoring.ETC (e.g., tion during rush hours.Facing this practical issue,we ask "Is Z-Pass and I-PASS)has become the most successful and there any convenient and user-friendly M2H communication widespread application of Radio Frequency IDentification way to provide informative interaction fast?" (RFID).Approximately,70%to 89%of cars are equipped with In this study.we introduce a novel ETC service,called ETC transponders (or tags)in the US.In particular,over 80% Tagcaster,which supplements the function of an AM radio of Illinois'1.4 million daily drivers currently use I-PASS [11. to the existing ETC infrastructure with zero start-up cost. ETC can eliminate delay on toll roads,HOV lanes,and toll Tagcaster can activate a deployed ETC tollbooth to provide the bridge by collecting tolls without requiring cars to stop.Owing wireless voice service for direct M2H communication.Fig.I to this wide adoption,the industry and academia are looking illustrates our service scenario.When a driver passes through a into delivering new services via the currently deployed ETC tollbooth,the ETC reader automatically identifies the vehicle's infrastructure.Examples include paying for food at drive- ID and retrieves its related data from backend servers.Then, through restaurants or parking lots with an e-toll transponder, the reader broadcasts the data in the form of an AM radio.The tracking the number of cars at every road intersection for traffic driver can listen to the broadcast using the vehicle-mounted control,and detecting and ticketing over-speeding cars without radio receiver or smart-phone inside. the need for car-mounted radars and hidden police officers. "Wireless voice"is more user-friendly and spontaneous ETC offers an opportunity for using ETC systems to enable than current interactive medias(e.g.,LED screens or external smart cities in the future [2]. speakers).It provides a new means to deal with the issue As a typical technology of the Internet of Things,ETC of poor visibility in bad weather conditions,such as stormy, systems are designed for machine-to-machine communication foggy or smoggy,when viewing feedback from ETC screens only (e.g.,identifying cars or monitoring traffic).Drivers is difficult for drivers.Such functionality is also useful in cannot directly obtain related information (e.g.,charge amount, a wide range of application scenarios.Apart from chargingActivating Wireless Voice for E-Toll Collection Systems with Zero Start-up Cost Zhenlin An∗ , Qiongzheng Lin∗ , Lei Yang∗ and Lei Xie† ∗Department of Computing,The Hong Kong Polytechnic University, Hong Kong †State Key Laboratory for Novel Software Technology, Nanjing University, China Email: ∗{an, lin, young}@tagsys.org, † lxie@nju.edu.cn Abstract—This work enhances the machine-to-human commu￾nication between electronic toll collection (ETC) systems and drivers by providing an AM broadcast service to deployed ETC systems. This study is the first to show that ultra-high radio frequency identification signals can be received by an AM radio receiver due to the presence of the nonlinearity effect in the AM receiver. Such a phenomenon allows the development of a previously infeasible cross-technology and cross-frequency communication, called Tagcaster, which converts an ETC reader to an AM station for broadcasting short messages (e.g., charged￾fees and traffic forecast) to drivers at tollbooths. The key innovation in this work is the engineering of Tagcaster over off-the-shelf ETC systems using shadow carrier and baseband whitening without the need for hardware nor firmware changes. This feature allows zero-cost rapid deployment in existing ETC infrastructure. Two prototypes of Tagcaster are designed, imple￾mented and evaluated over four general and five vehicle-mounted AM receivers (e.g., Toyota, Audi, and Jetta). Experiments reveal that Tagcaster can provide good-quality (PESQ> 2) and stable AM broadcasting service with a 30 m coverage range. Tagcaster remarkably improves user experience at ETC stations and two￾thirds volunteer drivers rate it with a score of 4+ out of 5. I. INTRODUCTION Electronic toll collection (ETC) is a system enabling elec￾tronic collection of toll payments, thus allowing for near￾nonstop toll collection and traffic monitoring. ETC (e.g., Z-Pass and I-PASS) has become the most successful and widespread application of Radio Frequency IDentification (RFID). Approximately, 70% to 89% of cars are equipped with ETC transponders (or tags) in the US. In particular, over 80% of Illinois’ 1.4 million daily drivers currently use I-PASS [1]. ETC can eliminate delay on toll roads, HOV lanes, and toll bridge by collecting tolls without requiring cars to stop. Owing to this wide adoption, the industry and academia are looking into delivering new services via the currently deployed ETC infrastructure. Examples include paying for food at drive￾through restaurants or parking lots with an e-toll transponder, tracking the number of cars at every road intersection for traffic control, and detecting and ticketing over-speeding cars without the need for car-mounted radars and hidden police officers. ETC offers an opportunity for using ETC systems to enable smart cities in the future [2]. As a typical technology of the Internet of Things, ETC systems are designed for machine-to-machine communication only (e.g., identifying cars or monitoring traffic). Drivers cannot directly obtain related information (e.g., charge amount, !"#$%&$'()*+,-./( 1 3 2 ETC READER ETC READER Vehicle-mounted AM Radio Good morning, sir. Charging fee is 5$. Notice the road ahead is under maintenance. Have a nice day! 4 Reply 1 Query Broadcasting 2 3 4 Listening Fig. 1: Tagcaster-enhanced wireless voice service for ETC system. ❶ The ETC reader queries the transponder attached on the vehicle. ❷ The transponder is identified through its reply. ❸ Tagcaster broadcasts the wireless voice to the identified vehicle. ❹ The driver can listen to the AM radio through the vehicle-mounted radio receiver. credit balance, real-time traffic and road condition). Achiev￾ing direct machine-to-human (M2H) communication between drivers and ETC systems requires extra peripherals and efforts. For example, drivers must slow down their cars to view an LED screen installed at the tollbooth for charge details. The information acquired by drivers is usually quite limited due to the small screen size. Slowing down also worsens the conges￾tion during rush hours. Facing this practical issue, we ask “Is there any convenient and user-friendly M2H communication way to provide informative interaction fast?” In this study, we introduce a novel ETC service, called Tagcaster, which supplements the function of an AM radio to the existing ETC infrastructure with zero start-up cost. Tagcaster can activate a deployed ETC tollbooth to provide the wireless voice service for direct M2H communication. Fig. 1 illustrates our service scenario. When a driver passes through a tollbooth, the ETC reader automatically identifies the vehicle’s ID and retrieves its related data from backend servers. Then, the reader broadcasts the data in the form of an AM radio. The driver can listen to the broadcast using the vehicle-mounted radio receiver or smart-phone inside. “Wireless voice” is more user-friendly and spontaneous than current interactive medias (e.g., LED screens or external speakers). It provides a new means to deal with the issue of poor visibility in bad weather conditions, such as stormy, foggy or smoggy, when viewing feedback from ETC screens is difficult for drivers. Such functionality is also useful in a wide range of application scenarios. Apart from charging