IEEE Circuits and Systems Magazine - Q1 2022 - 11

everyday objects, giving rise to the so-called Internet of
Things (IoT) as one of the key technology players in the
virtualization process. IoT implies the interconnection
of billions of cyberphysical entities, which can either be
physical or virtual, with a hybrid software/hardware
structure, capable of communicating with each other,
sometimes without the need of human intervention
thanks to Machine-to-Machine (M2M) communication
protocols. Moreover, IoT is expected to have a potential
impact on the global economy of 11.1 trillion dollars
in 2025, what means above 10% of the gross domestic
product globally, about 30 billion connected devices in
2023 and 350 billion by 2030 [3], [4].
virtualized version. Efficient IoT nodes will require also
the development of hybrid software/hardware platforms,
new computation paradigms and communication
protocols, as well as highly adaptive and programmable
circuitry, and very specially in the analog side of the
system and the analog/digital interface [2], [3], [5], [6].
One of the main bottlenecks associated to the increasingly
number of IoT devices which will have an impact of
the design of end-devices is the increasingly shared use
of the electromagnetic spectrum. Although new bands-
such as millimeter wavelengths (mm-Wave or mm-W)-
are being incorporated in the latest generations of mobile
networks (5G and the incoming 6G), they will also
keep increasing the traffic of data [7]- [13]. The so-called
Cognitive Radio (CR) [14] allows communication systems
to make a more efficient use of the frequency spectrum,
by dynamically modifying the transceiver specifications
according to the information sensed from the electromagnetic
environment [15]. An efficient implementation
of CR-based terminals may benefit from embedding AI
engines in their main building blocks, which in turn will
need new Circuits and Systems strategies with a high degree
of programmability and reconfigurability in order to
dynamically select the optimum set of performance metrics
and transmission bands [3], [9], [3], [16-19].
Fig. 1 shows the conceptual diagram of a CR-based
transceiver, where the operation of its main building
blocks is controlled by an AI engine. CR-based mobile
terminals would require also that the analog/digital (A/D)
interfaces should be placed as close as possible to the
antenna, so that most of the hardware can be essentially
digital, thus being easier to program its functionality by
software. Another key technology enabler is related to the
use of AI-managed Analog Signal Processing (ASP) and
Radio-Frequency (RF) front-ends, so that they can set
their best specifications in an autonomous way, according
to the environment conditions (communication coverage,
band occupancy, noise and interferences, etc.), battery
status and energy consumption. However, the practical
realization of CR-based IoT devices requires highly programmable
digital-friendly analog/RF front-ends [20].
In this context, this paper surveys some emerging
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IoT devices need to be equipped with a certain level
of intelligence, so that they can make decisions in real
time, and locally, i.e. without being connected to remote
servers. It is therefore necessary to address a number
of design challenges in order to build a solid bridge between
the physical environment and its corresponding
strategies-including telecom systems and computing
architectures, AI algorithms based on neural networks,
as well mostly-digital/digital-assisted analog circuit techniques-intended
for energy-efficient CR-based end-devices.
A survey of the most important technology enablers
is given to set the application scenario and define the main
objetives that should be addressed by AI-managed CAS for
CR-based IoT nodes, by focusing on the Analog-to-Digital
José M. de la Rosa is with the Institute of Microelectronics of Seville, IMSE-CNM (CSIC/University of Seville), Parque Tecnológico de la Cartuja,
C/Américo Vespuccio 28, 41092 Sevilla, SPAIN, e-mail: jrosa@imse-cnm.csic.es.
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IEEE Circuits and Systems Magazine - Q1 2022

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