Enhancement of motion feedback latency for wireless virtual reality in IEEE 802.11 WLANs

Wireless virtual reality (VR) that offloads VR processing to a powerful PC and streams rendered VR image frames to a VR headset wirelessly is a promising technology for high-quality interactive VR experiences with free mobility and high immersiveness. Realizing wireless VR in IEEE 802.11 WLANs is feasible when combined with the Timewarp technique, but minimal latency is still of importance for higher quality of VR service. In this paper, we reveal that the bi-directional transmission nature of wireless VR (VR frame data in downlink and motion-feedback data in uplink) and the resulting delay of motion feedback is a major challenge of wireless VR in IEEE 802.11 WLANs. To combat this challenge, we propose three basic methods-(1) prioritizing aged motion data, (2) using reverse direction, and (3) limiting the aggregation size of downlink transmission-and demonstrate that all enhance the latency and jitter of motion feedback, and, among these, limiting the aggregation size is most effective. We then design a scheme to adjust the aggregation size of downlink transmission in conjunction with the use of reverse direction to best support responsive and frequent motion feedback while preserving the downlink transmission of VR frame data.