  Guaranteeing ultra reliable low latency communications (URLLC) with high data
rates for virtual reality (VR) services is a key challenge to enable a dual VR
perception: visual and haptic. In this paper, a terahertz (THz) cellular
network is considered to provide high-rate VR services, thus enabling a
successful visual perception. For this network, guaranteeing URLLC with high
rates requires overcoming the uncertainty stemming from the THz channel. To
this end, the achievable reliability and latency of VR services over THz links
are characterized. In particular, a novel expression for the probability
distribution function of the transmission delay is derived as a function of the
system parameters. Subsequently, the end-to-end (E2E) delay distribution that
takes into account both processing and transmission delay is found and a
tractable expression of the reliability of the system is derived as a function
of the THz network parameters such as the molecular absorption loss and noise,
the transmitted power, and the distance between the VR user and its respective
small base station (SBS). Numerical results show the effects of various system
parameters such as the bandwidth and the region of non-negligible interference
on the reliability of the system. In particular, the results show that THz can
deliver rates up to 16.4 Gbps and a reliability of 99.999% (with a delay
threshold of 30 ms) provided that the impact of the molecular absorption on the
THz links, which substantially limits the communication range of the SBS, is
alleviated by densifying the network accordingly.
