  Cellular-connected wireless connectivity provides new opportunities for
virtual reality(VR) to offer seamless user experience from anywhere at anytime.
To realize this vision, the quality-of-service (QoS) for wireless VR needs to
be carefully defined to reflect human perception requirements. In this paper,
we first identify the primary drivers of VR systems, in terms of applications
and use cases. We then map the human perception requirements to corresponding
QoS requirements for four phases of VR technology development. To shed light on
how to provide short/long-range mobility for VR services, we further list four
main use cases for cellular-connected wireless VR and identify their unique
research challenges along with their corresponding enabling technologies and
solutions in 5G systems and beyond. Last but not least, we present a case study
to demonstrate the effectiveness of our proposed solution and the unique QoS
performance requirements of VR transmission compared with that of traditional
video service in cellular networks.
