Battery-less Passive Sensing System for Human Activity Monitoring

What is our design idea?

Modernization, industrialization, and urbanization have become the major themes of our society. Studies show that by the year 2050, 67% of the world’s population will live in cities. High population density brings convenience to people’s life, but will also make us more vulnerable. “Thanos’ finger snap” may be fictional, but the desires to live healthier, more secure and more convenient are real.

To satisfy these demands, we propose a “smart jacket” that is powered by fully textile-based embroidered sensors. This jacket can collect human health conditions, activities data and locate people’s whereabouts. The sensors on the jacket can harvest energy to provide a self-sustained power source and transmit the data to the cloud wirelessly, thus the jacket can work perpetually without the needs of replacing batteries. Besides, the embroidered device fabrication techniques can seamlessly integrate sensors with the fabrics, and provide a nonintrusive and aesthetic experience when wearing it. With this smart jacket, we will construct a human activity monitoring system/network that can be used for human health monitoring, movement detection, and indoor navigation. The successful deployment of the system will provide assisted living, surveillance-based security, sports and fitness activities, healthcare of everyone.

How will our idea make urban living healthier around the globe?

To be specific, our proposal can serve as a solution to alleviate the following aspects.

  1. People Are Aging. In the future, most senior-aged people may live by themselves, however, the shortage of labor will make it impractical and impossible to take care of everyone in the empty-nest. A large-scale, real-time “home alert” system should be implemented to monitor these elders’ daily activities as well as their health conditions. With the full implementation of such systems in those empty-nests, future cities can achieve 24-7-365, real-time health and activities monitoring for the elders.
  2. Living Space is Packing. Urbanization force the city planners to exploit every square inch of the living space. Maga-building will become most people’s hive and habitat. Indoor navigation will be a “must-have” for everyone, just like today’s GPS for every driver. RFID tags can be served as “tokens” so that we can utilize the transmission signal to determine the location around the buildings to achieve indoor navigation.
  3. Resources are limited: population distribution around the city is the critical information for the city’s management to allocate limited public resources. This problem becomes increasingly significant when large crowds of dwellers move around the cities. With RFID based crowd density monitor, it can achieve low cost and real-time monitoring.

How does it work?

The system is performed in three steps: 1) the acquisition of body signals, 2) the preprocessing of the signal and 3) the analysis of the data. Figure 2 shows the architecture of the proposed human activity monitoring system. The sensors using novel embroidered fabrication techniques which is suitable for wearable application and are made as RFID tags placed on the human body. The raw data from the RFID sensors are collected by an RFID reader which is implemented in the FPGA board. The data are processed and then send to a local processor such as Raspberry Pi or PC. Due to the complexity, the data may not be completely processed by the local processor. The device can send the data to a cloud platform to further analysis. The result will send back to the local processor.

The system is based on RFID technology. Passive UHF RFID already allows inexpensive tags to be remotely powered and interrogated for identifiers and other information at a range of more than 30 feet. The tags can be small as they are powered by the RF signal transmitted from a reader rather than an onboard battery. The RFID Sensor Networks we focus on this project extend RFID beyond simple identification to in-depth sensing. Now, each tag could be viewed as a sensor. This design could take with lots of advantages such as small size, long-lived, no battery (Tags), inexpensive and so on. During the communication of reader and tags, tags need backscatters electromagnetic wave. If we analyze information (phase, amplitude) of replies, then we can get the sensing parameters.

We implement the signal processing part of the reader on FPGA because of its flexibility and programmability. Figure 3 depicts a basic block diagram of its architecture.

Why should our idea win?

  1. The sensors or RFID antennas can be directly embroidered with conductive yarns on clothes using standard embroidery processes, which can achieve seamlessly and aesthetically embedded property.
  2. The cost of manufacturing can be very cheap and easy to be implemented because it can utilize mature fabrication technology.
  3. The smart jacket is working under the passive mode, which means we don’t need to consider the battery life or charging problem.


wearable electronics is a hot topic.


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