## 1 Introduction
### Related Work
#### 1.1.2 Experimental Studies and Wireless VR Testbeds  
In [9], a multi-path multi-tier 360\({}^{\circ}\) video streaming technique is proposed taking into account the dynamics of the network bandwidth as well as the user viewing direction. In this work, video encoding is performed at multi-tiers, i.e., the base-tier encoded with a basic rate, enhancement-tier coded with multiple rates and assisting view prediction accuracy, and correction-tier carrying information about the predicted view direction. A 5G wireless research platform is used to collect real bandwidth traces over a WiGig testbed which, in combination with a Wi-Fi component, allows for studying the multi-path approach. In addition, real user field of view traces with diverse head movement patterns are used for the assessment of the multi-tier approach. The analytical and experimental performance assessment in terms of optimal rate allocation, throughput, latency, and network utilization demonstrated that a high level of QoE can be achieved. The experimental study reported in [10] assesses the IEEE 802.11 ad performance on a smartphone regarding throughput, coverage, mobility, and power consumption. The experimental setup focused on an indoor environment using an Asus Republic of Gamers (ROG) Android gaming smartphone which is equipped with an IEEE 802.11 ad chip set. All measurements were performed with a Netgear Nighthawk X10 Smart WiFi Router which allows for 4K streaming, VR gaming, and instant downloads. In this context, the ROG smartphone was assessed as a general purpose IEEE 802.11 ad smartphone. The measurement campaign revealed that the ROG smartphone was able to support Gbps throughput while power consumption was less of an issue than originally expected. However, the results suggest that the beamforming protocol on the smartphone performs suboptimally and affects the network performance. Overall, it was concluded that IEEE 802.11 ad is a promising technology for upcoming bandwidth-intensive applications on smartphones. Building on [10], a more comprehensive performance assessment of IEEE 802.11 ad on smartphones is provided in [11]. The experimental study presented in this work considers the following three experimental setups. First, the IEEE 802.11 ad setup operating at the 60 GHz band comprises of an Asus ROG Android gaming smartphone and a Netgear Nighthawk X10 Smart WiFi Router. Physical layer data rates range from 1.65 Gbps to 2.3 Gbps depending on the scenario. Second, a Samsung Galaxy S10 and Xiaomi Mi 10 phone and an ASUS RT-AX88U router constitute the IEEE 802.11 ax-2021 or IEEE 802.11 ax setup operating at the 5 GHz band. In this setup, the smartphones constrained the maximum physical layer data rate to 1.2 Gbps. Third, the state-of-the-art IEEE 802.11 ac setup operating at the 5 GHz band, was used for comparison with the IEEE 802.11 ad scenario, also using the Netgear Nighthawk router with the ROG phone. The physical layer data rate of this setup was limited to 866 Mbps. The performance of these setups were evaluated with respect to range, coverage, mobility, blockage, and power consumption. The measurement data allowed to assess the impact of smartphone features such as antenna array placements as well as performance comparisons among members of the family of IEEE 802.11 standards. Although inferior to an IEEE 802.11 ad-enabled laptop, it was shown that an IEEE 802.11 ad-enabled smartphone can sustain Gbps data rates given that the range to the access point is kept within a few tens of ft. Overall, it was found that the IEEE 802.11 adsetup, which is placed at the 60 GHz band, outperforms the 5 GHz counterparts associated with IEEE 802.11 ac and IEEE 802.11 ax. However, challenges faced with the IEEE 802.11 ad setup include performance degradation due to the beamforming protocol, antenna array placement, and human blockage. In [12], an extensive measurement study is reported focusing on the predictability of throughput of an IEEE 802.11 ad system on the downlink to an IEEE 802.11 ad-enabled mobile device.