Page 22 - ITU Journal Future and evolving technologies Volume 2 (2021), Issue 3 – Internet of Bio-Nano Things for health applications

ITU Journal on Future and Evolving Technologies, Volume 2 (2021), Issue 3

the most studied aspect of MC in the literature. system. Accordingly, the stimulation carrying the en‑
Several methods varying in complexity have been coded information is applied at one end of the nerve
proposed to cope with the ISI, noise, and even the cord, and the resulting nerve spikes are recorded at the
nonlinearity of the channel, such as optimal other end. Through the application of different modu‑
Maximum Likelihood (ML)/Maximum A Posteriori lation schemes, e.g., OOK, frequency shift keying (FSK),
(MAP) detection methods, noncoherent detection, the authors demonstrate data rates up to 66.61 bps with
6.8 × 10 −3 bit error rate.
sequence detectors with Viterbi algorithm [86, 87, 63,
In [91], the authors propose to use vagus nerve to deliver
88, 13]. Synchronization problem is addressed by both
instructions to an implanted drug delivery device near the
developing self‑synchronizing mod‑ ulation techniques
brainstem via compound action potentials (CAP) gene-
and asynchronous detection methods. However, these
rated by the application of electrical impulses at the
methods are developed based on existing theoretical
neck, known in the literature as the vagus nerve
models of MC, which largely lack physical
stimulation (VNS). Applying an OOK modulation, the
correspondence. Therefore, the performance of the
authors theoretically show that the vagus nerve can
proposed methods is not validated, which poses a major
support data rates up to 200 bps and unidirectional
problem before practical MC systems and IoBNT applica‑
transmission ranges between 60 mm and 100 mm,
tions.
which is promising for enabling the communication of
distant BNTs at a rate that is much higher than the
3.1.2 Human Body as IoBNT Infrastructure typical MC rates.
A different approach to make use of the natural hu‑
MC can typically support only very low communication
man body networks for IoBNT is investigated in [92],
rates due to the slow diffusion dynamics of molecules.
where authors propose to use Microbiome‑Gut‑Brain‑
Moreover, MC is prone to errors because of high level of Axis (MGBA) to connect distant BNTs. MGBA is a large
noise and molecular interference in crowded physiologi‑ scale heterogeneous intrabody communication system
cal media, as well as due to attenuation of molecular sig‑ composed of the gut microbial community, the gut tis‑
nals as a result of degradation via various biochemical sues, and the enteric nervous system. In MGBA, a bidirec‑
processes, making it reliable only at very short ranges [8]. tional communication between the central nervous sys‑
On the other hand, human body has a large‑scale complex tem and the enteric nervous system surrounding the gas‑
communication network of neurons extending to various trointestinal track (GI track) is realized via the transduc‑
parts of the body and connecting different body parts tion of electrical signals in the nervous system into mole-
with each other through electrical and chemical signaling cular signals in the GI track, and vice versa. The axis
modalities [4]. A part of the nervous system also senses has recently attracted signi icant research interest due to
external stimuli via sensory receptors and transmits the the discoveries underlining the relation of MGBA
sensed information to the central nervous system, where signaling with some neurological and gut disorders
such as depression and irritable bowel syndrome
a reaction is decided [5]. In that regard, the nervous sys‑
(IBS). In the research roadmap proposed in [92], the
tem provides a ready infrastructure that can potentially
authors envision BNTs as electrical biomedical devices,
connect nanomachines in distant parts of the body with
e.g., cardiac pacemaker, brain implants, insulin pumps,
each other and with the external devices. In fact, there
and biological devices, e.g., synthetic gut microbes and
are many proposal in this direction that both theoretically
arti icial organs, interconnected through the MGBA. They
and experimentally investigate the idea of using the ner‑
also investigate the possibility of a link between the
vous system as an IoBNT backbone inside human body.
IoBNT and the external environment via molecular
In [89], authors consider a thru‑body haptic communi‑
(alimentary canal) and electrical (wireless data transfer
cation system, where the information encoded into tac‑
through skin) interfaces.
tile stimulation is transmitted to the brain through the
nervous system, resulting in a discernible brain activity
which is detected by ElectroEncephaloGraphy (EEG) and 3.1.3 Other Nanocommunication Modalities for
IoBNT
used to decode the transmitted information. An analyti‑
cal framework based on the computational neuroscience
models of generation and propagation of somatosensory a) THz‑band Electromagnetic Nanocommunication:
stimulation from skin mechanoreceptors is developed for Conventional electromagnetic (EM) communication is
the analysis of the achievable data rate on this communi‑ not deemed suitable for IoBNT because the size of BNTs
cation system. Authors show that the system can support would demand extremely high operating frequencies
bit rates of 30‑40 bit per second (bps) employing an OOK [93]. Fortunately, graphene‑based nanoantennas based
modulation of tactile stimulation taps at the index inger. on surface plasmon polariton (SPP) waves have been
In [90], the authors practically demonstrate a controlled shown to support frequencies down to 0.1 THz, much
information transfer through the nervous system of a lower than their metallic counterparts, promising for
common earthworm, which stands as a simple model the development of high‑bandwidth EM nanonetworks
system for bilaterian animals including humans. In the of nanomaterial‑based BNTs using the unutilized THz‑
demonstrated setup, authors use external macroscale band (0.1‑10 THz) [94]. In this direction, several plas‑
electrodes to interface with the earthworm’s nervous monic transceiver antenna designs using graphene and

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