A non-stationary relay-based 3D MIMO channel model with time-variant path gains for human activity recognition in indoor environments
Peer reviewed, Journal article
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2021Metadata
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Original version
Hicheri, R. Abdelgawwad, A. Pätzold, M. U. (2021). A non-stationary relay-based 3D MIMO channel model with time-variant path gains for human activity recognition in indoor environments. Annales des télécommunications, 76, 827-837. https://doi.org/10.1007/s12243-021-00844-0Abstract
Extensive research showed that the physiological response of human tissue to exposure to low-frequency electromagnetic
fields is the induction of an electric current in the body segments. As a result, each segment of the human body behaves as
a relay, which retransmits the radio-frequency (RF) signal. To investigate the impact of this phenomenon on the Doppler
characteristics of the received RF signal, we introduce a new three-dimensional (3D) non-stationary channel model to
describe the propagation phenomenon taking place in an indoor environment. Here, the indoor space is equipped with a
multiple-input multiple-output (MIMO) system. A single person is moving in the indoor space and is modelled by a cluster
of synchronized moving point scatterers, which behave as relays. We derive the time-variant (TV) channel transfer function
(CTF) with TV path gains and TV path delays. The expression of the TV path gains is obtained from the instantaneous total
received power at the receiver side. This TV total received power is expressed as the product of the TV power of the RF signal
initially transmitted and received by a body segment and the TV received power of the redirected signal. These TV powers
are determined according the free-space path-loss model. Also, a closed-form approximate solution to the spectrogram of
the TVCTF is derived. Here, we analyse the effect of the motion of the person and the validity of the relay assumption on
the spectrogram, the TV mean Doppler shift (MDS), and the TV Doppler shift (DS) of the TVCTF. Simulation results are
presented to illustrate the proposed channel model.