  Over-the-air computation (AirComp) leverages the signal-superposition
characteristic of wireless multiple access channels to perform mathematical
computations. Initially introduced to enhance communication reliability in
interference channels and wireless sensor networks, AirComp has more recently
found applications in task-oriented communications, namely, for wireless
distributed learning and in wireless control systems. Its adoption aims to
address latency challenges arising from an increased number of edge devices or
IoT devices accessing the constrained wireless spectrum. This paper focuses on
the physical layer of these systems, specifically on the waveform and the
signal processing aspects at the transmitter and receiver to meet the
challenges that AirComp presents within the different contexts and use cases.
