We present design and implementation of CyPhyS+, a comprehensive, low-cost and standards compliant Cyber-Physical System (CPS) using 6LoWPAN based Internet of Things for remote health monitoring of elderly staying in old-age homes. It is a closed-loop system that incorporates an end-toend reliable message transfer scheme for the resource constrained environment, data security, real-time medical signal processing and data analytics, and FHIR/HL7 compliant web services. The low power operation of CyPhyS+ allows the CPS an extended uptime, ensuring connectivity to the medical sensors, via the Internet, anytime/anywhere. The end-to-end reliable and secure messaging mechanism of CyPhyS+ does not necessitate intermediate application end-points at the old-age homes. This enables easy deployment with low operational overheads, scalability as well as easy introduction of newer applications or application upgrades. The paper describes system architecture, design and implementation details of software and hardware sub-systems. HealthMote, a power efficient Bluetooth-6LoWPAN mote was designed and deployed as a sub-system. We describe the novel low power end-to-end multi-stage message reliability scheme for UDP based sensor applications that does not require intermediate application-aware devices within the network. The experimental results presented show the efficacy of the approach. CyPhyS+ employs an application performance aware SNMP based network monitoring for robust operations of the 6LoWPAN multihop network. It incorporates a 128-bit AES, CBC-MAC based encryption and authentication mechanism for security and privacy. CyPhyS+ is compliant with FHIR/HL7 standards framework, with support for RESTful FHIR, and medical data analytics of ECG. We report on the extensive field trials carried out across a city.

Abstract-Clock synchronization is highly desirable in distributed systems, including many applications in the Internet of Things and Humans (IoTH). It improves the efficiency, modularity and scalability of the system; and optimizes use of event triggers. For IoTH, Bluetooth Low Energy (BLE) -a subset of the recent Bluetooth v4.0 stack -provides a lowpower and loosely coupled mechanism for sensor data collection with ubiquitous units (e.g., smartphones and tablets) carried by humans. This fundamental design paradigm of BLE is enabled by a range of broadcast advertising modes. While its operational benefits are numerous, the lack of a common time reference in the broadcast mode of BLE has been a fundamental limitation. This paper presents and describes CheepSync: a time synchronization service for BLE advertisers, especially tailored for applications requiring high time precision on resource constrained BLE platforms. Designed on top of the existing Bluetooth v4.0 standard, the CheepSync framework utilizes lowlevel timestamping and comprehensive error compensation mechanisms for overcoming uncertainties in message transmission, clock drift and other system specific constraints. CheepSync was implemented on custom designed nRF24Cheep beacon platforms (as broadcasters) and commercial off-the-shelf Android ported smartphones (as passive listeners). We demonstrate the efficacy of CheepSync by numerous empirical evaluations in a variety of experimental setups; and show that its average (single-hop) time synchronization accuracy is in the 10 µs range.