monitor the patient’s symptoms and make appropriate
decision support in real-time. The supervised learning
model learns the representation of clean ECG signal
and corresponding PPG signals (Red and IR) from a
single measured noisy ECG signal. The clean signals
can be used for accurate heart rate and SpO
2
estimation.
The rest of this paper is organized as follows.
Section 2 gives an overview of the related works.
Section 3 offers a description of the proposed
wearable system. In Section 4, we analyze the results
obtained and discuss about the implication of our
work. A conclusion and future perspectives are given
in Section 5.
2 RELATED WORKS
Many researchers in IoT and artificial intelligence
have developed various tools for monitoring and
detection of the virus infection. a number of wearable
systems with tiny sensors integrated into garments or
accessories have been used to measure physiological
parameters (e.g., skin temperature, heart rate, and
SpO
2
) of infected patients (Cacovean, Ioana et al.
2020, Nasajpour, Pouriyeh et al. 2020, Pozo and
Berrezueta Guzman 2020). Skin temperature is
estimated thanks to temperature sensor, SpO
2
level is
estimated from PPG signals (Red and IR) measured
by pulse oximeter sensor, and heart rate is estimated
from ECG signal measured by heart monitor sensor.
These wearable systems will enable the detect the
gravity of symptoms by checking measured
parameters values (e.g., the skin temperature>38°C ,
corresponding to high fever, SpO2<92% associate to
shortness of breath, and heart rate>90 bpm associate
to heart failure). The wearable systems allow a quick
monitoring of infected wearer’s health state with real-
time data acquisition.
Despite these advantages, the current wearable
systems have several drawbacks: 1) Raw ECG signals
and PPG signals are highly sensitive to noises (Chen,
Li et al. 2017, Chatterjee, Thakur et al. 2020) (Motion
artifacts, powerline interference, Baseline wander).
Without a pre-processing step, the signals cannot be
exploited for heart rate and SpO
2
estimation; 2) The
patient daily activities are heavily obstructed by the
positioning of the pulse oximeter sensor (the tip of the
finger is the optimal position for SpO
2
monitoring, the
patient need to stay still for an optimal measurement)
; 3) Wrist-based wearable system, while more robust
and less restraining than traditional wearable systems,
appears to be less accurate (They incorporate wrist-
based pulse oximeter sensor, which are less accurate
than finger-based pulse oximeter (Lee, Ko et al.
2016)) . They are also not easy affordable (the
average smart-watch price is higher than 150$). Since
the peripheral blood volume variation is linked to left
ventricular myocardial activities, it is easy to
establish a correlation between The PPG and ECG
signals. By using GAN, (Zhu, Tian et al. 2019, Sarkar
and Etemad 2021, Vo, Naeini et al. 2021) estimate
the waveform of the ECG signal using PPG
measurements by learning a signal model related to
ECG and PPG. Despite the good results obtained, the
models are not trained to handle noisy PPG signals.
Therefore, generated ECG and PPG signals are still
sensitive to noise.
In this context, the proposed system has been
developed to overcome the daily activities
obstruction caused by the pulse oximeter sensor and
the signals (ECG, PPG
Red
and PPG
IR
) vulnerability
against noise. We propose a low-cost smart textile
coupling with a supervised learning model. Instead of
learning ECG waveform representation from PPG
waveform, the model will learn three waveforms
representation (ECG, PPG
Red
and PPG
IR
) from a noisy
ECG waveform. In the next section, we describe the
overall system, the supervised learning method for
PPG signals generation, and the experimental results.
3 MATERIAL AND METHODS
The architecture of our wearable system is heavily
based on (Tao, Huang et al. 2018). The proposed
electronic textile measured ECG signal and skin
temperature and transmit the data to a mobile
application thanks to the Bluetooth Low Energy
(BLE) protocol. BLE allows a lower power
consumption than other wireless transmissions
protocol (Bluetooth, Zigbee) and improves the system
energetic autonomy. The mobile application by using
the proposed supervised model, reconstruct from the
noisy ECG signal measured by the wearable device,
three clean signals:
- ECG signal: The ECG signal will be use to
estimate the heart rate.
- PPG Red and IR signals: The two signals
will be used to estimate the SpO
2.
By checking the heart rate, SpO
2
and skin temperature
values (skin temperature>38°C, SpO2<92% and
heart rate>90 bpm), the system allow a quick
monitoring of the wearer health state in real-time.
The generated waveforms, heart rate, SpO
2
, skin
temperature and COVID-19 patient state are shown