  In this paper, we introduce the Age of Incorrect Information (AoII) as an
enabler for semantics-empowered communication, a newly advocated communication
paradigm centered around data's role and its usefulness to the communication's
goal. First, we shed light on how the traditional communication paradigm, with
its role-blind approach to data, is vulnerable to performance bottlenecks.
Next, we highlight the shortcomings of several proposed performance measures
destined to deal with the traditional communication paradigm's limitations,
namely the Age of Information (AoI) and the error-based metrics. We also show
how the AoII addresses these shortcomings and captures more meaningfully the
purpose of data. Afterward, we consider the problem of minimizing the average
AoII in a transmitter-receiver pair scenario where packets are sent over an
unreliable channel subject to a transmission rate constraint. We prove that the
optimal transmission strategy is a randomized threshold policy, and we propose
a low complexity algorithm that finds both the optimal threshold and the
randomization parameter. Furthermore, we provide a theoretical comparison
between the AoII framework and the standard error-based metrics counterpart.
Interestingly, we show that the AoII-optimal policy is also error-optimal for
the adopted information source model. At the same time, the converse is not
necessarily true. Finally, we implement our proposed policy in various
real-life applications, such as video streaming, and we showcase its
performance advantages compared to both the error-optimal and the AoI-optimal
policies.
