  Guaranteeing fresh and reliable information for augmented reality (AR)
services is a key challenge to enable a real-time experience and sustain a high
quality of physical experience (QoPE) for the users. In this paper, a terahertz
(THz) cellular network is used to exchange rate-hungry AR content. For this
network, guaranteeing an instantaneous low peak age of information (PAoI) is
necessary to overcome the uncertainty stemming from the THz channel. In
particular, a novel economic concept, namely, the risk of ruin is proposed to
examine the probability of occurrence of rare, but extremely high PAoI that can
jeopardize the operation of the AR service. To assess the severity of these
hazards, the cumulative distribution function (CDF) of the PAoI is derived for
two different scheduling policies. This CDF is then used to find the
probability of maximum severity of ruin PAoI. Furthermore, to provide long term
insights about the AR content's age, the average PAoI of the overall system is
also derived. Simulation results show that an increase in the number of users
will positively impact the PAoI in both the expected and worst-case scenarios.
Meanwhile, an increase in the bandwidth reduces the average PAoI but leads to a
decline in the severity of ruin performance. The results also show that a
system with preemptive last come first served (LCFS) queues of limited size
buffers have a better ruin performance (12% increase in the probability of
guaranteeing a less severe PAoI while increasing the number of users), whereas
first come first served (FCFS) queues of limited buffers lead to a better
average PAoI performance (45% lower PAoI as we increase the bandwidth).
