Active RFID Contact Tracing System
Contact tracing has always been important as a process employed by health
authorities in the control of communicable diseases. The main purposes of contact
tracing are to confirm the diagnosis, determine the extent of secondary transmission
and identify control measures. The outbreak of Severe Acute Respiratory Syndrome
(SARS) reported worldwide in 2003 is one example of an urgent need to trace the
contact history of an infected person for a prolonged period.
Most of the contact tracing methods practiced are manual and very time consuming.
There were couples of electronic automated schemes introduced during the SARS
period. They were not very popular due to some of the limitations such as increased
cost, complexity, difficulty in installation, reduced battery life etc. These limitations
prevented them from being widely deployed in spite of the fact that contact tracing is
a very critical requirement towards containment of diseases such as SARS.
Active RFID Contact Tracing System
Active RFID Contact Tracing System was designed and developed with these
limitations in mind so as to provide viable alternative to the current systems. So, the
team came up with novel techniques to design mobile tags that could operate on coin-
sized battery consuming very low power. It is very efficient in its operation and easy
to install. It consists of three functional modules – a reader, beacons and mobile active
RFID tags. Tags are worn by personnel and can exchange information among them. A
tag is carefully designed with low power circuitry and protocols to provide long
battery life and small size. Beacons provide location information to the tags. The
reader is used to activate (issue) and deactivate (return) tags, and to download
information from the tags. All the processes such as tag activation/deactivation,
tracking and information downloading are done wirelessly. These features make the
system very easy to install and use. Reducing power consumption in the tags is a very
challenging task when the tags have to receive information in addition to transmitting
it. Our tags can operate efficiently with off-the-shelf button cells for many months. As
long as the persons to be traced are wearing a tag each, their contact information such
as identity and time of contact will be exchanged and recorded in their respective tag.
This can happen anywhere and anytime as far as they are in proximity, with no other
Active RFID Contract Tracing System is a system that can be applied to other areas
also where short range proximity-based contact tracing is needed. It can be applied to
a supermarket environment to study consumer browsing pattern in supermarket. It can
also be applied to study the interaction behavior of wild animals in nature.
In the context of SARS, contact tracing for medical surveillance proved fundamental
as a control measure in facilitating early diagnosis and treatment of disease among
contacts and preventing disease spread in the community. Most of the contact tracing
is done manually and is very time consuming. For example, in the case of a hospital,
contact tracing involves asking the patient, visitor or healthcare worker later
diagnosed with SARS to recall where in a hospital he had been to and when. This has
to be compared with other similar records in order to come out with conclusions. This
is tedious, time consuming and not very reliable in many cases. There are limited
automated techniques using electronic tags for contact tracing. But these systems
either require prior installation and wiring or the battery for the tag lasts only a few
The current innovation makes the installation process easy and fast. By issuing an
electronic communicating tag to all the visitors coming to the hospital the contacts
they have made and the information about locations they had been are automatically
captured. This information can be retrieved very fast just by the issue of a command
to the system. The system can be installed in an ad hoc manner even under emergency
conditions, as no wiring is required. All the critical units of the system including the
tags and beacons operate wirelessly. The battery for the tag can last for a few months.
In general, the system can be applied to any scenario requiring contact tracing, more
so for the communicable diseases. It can play a significant role in preventing the
diseases from further spreading and causing loss of lives, revenues and jobs.
Figure 1: An
illustration of how
the system works
Beacon Figure 2 : Prototype of the
Mobile StarTrack Contact Tracing
A field trail in a local hospital Accidents and Emergency (A&E) Department was
conducted to test the performance of the Active RFID Contact Tracing System. Other
than I2R as the technology provider, ETPL has pulled in System Integrator, Hardware
Solution Provider and Software Solution provider as partners in this trial.
Challenges faced and Solutions
The Active RFID Contact Tracing System employs Radio Frequency (RF) technology
to perform the task. Challenges in such systems include unpredictability of RF
propagation in different indoor environment.
RF signal is easily affected by large liquid and metal objects, including the human
body. This posed a challenge to ensure the contact information is captured when two
persons were positioned back to back. In such condition, the human bodies blocked
the signal from the two tags from reaching each other. This prevented the exchange of
information between tags.
Additional functionality was implemented in the backend system to address this issue.
Coverage of beacons was enhanced and number of beacons were increased to improve
the system. The backend database system could analyse the data collected and do
extrapolation to obtain missing contact information. This can be done based on
information gathered from tags, beacons and time stamp.
Full coverage by the beacons over the entire area was implemented to ensure the
reliability of the scheme. Ensuring the full coverage posed new challenges.
The large open spaces in the waiting areas posed an issue when deploying the beacons.
The beacons must not be deployed in the middle of the open space, because it would
obstruct the traffic flow and it may affect the physical look of the environment. The
beacons had to be re-designed to be mounted at the ceiling. I2R’s antenna team
designed a ceiling mount antenna to address this. The new beacon antenna helped
enhance coverage without causing obstruction as well as retaining the aesthetics.
The original system, together with the enhancements, had achieved high level of
accuracy and reliability. However, for a mission critical task, the hospital’s A&E
department expects zero error. To achieve this zero error, the system requires further
enhancements as well as some re-design.
The Active RFID Contract Tracing System greatly reduces the manual work required
for the tracing of contact history of patients, staff and visitors in a hospital. A field
trial was conducted in a realistic environment. Through this trial, valuable experiences
were gained in terms of real-time practical issues and challenges, as well as having a
better understanding of the users’ requirement.