## 2 Experimental Setup
### TPCAST VR Testbed  
Figures 3 and 4, respectively, show a block diagram and photos of the typical placement of the hardware components of the TPCAST wireless VR testbed. In the following, detailed descriptions of the different blocks of our TPCAST VR testbed that were used in this work are provided. The interested reader is referred to [19] for further details of the TPCAST VR testbed and its complete monitoring capabilities that may be used to pursue experimental studies on other challenges of wireless VR. Figure 1: Multi-purpose lecture hall with the transmitter (foreground) which is moved to six different distances away from the receiver (background) during the measurement campaign. Figure 2: Floor plan of the multi-purpose lecture hall including placement of the measurement equipment and introducing a room partitioning into quadrants around the receiver (Tx,v: Transmitter of the 60 GHz video link; Rx,v: Receiver of the 60 GHz video link; Q1-4: Quadrants; IR: Infrared; HMD: Head-mounted display). * **TPCAST transmitter and receiver:** The TPCAST wireless adapter was specifically developed for the HTC Vive HMD. The main components of this system include an HMD receiver, personal computer (PC) transmitter, and a router. TPCAST is designed for an intended transmitter-receiver distance of above 5 m allowing a footprint of 80-100 m\({}^{2}\) with a 360\({}^{\circ}\) degree freedom of movement. TPCAST operates in the 57-66 GHz frequency band using the carrier frequencies of 60.48 GHz and 62.64 GHz with a channel spacing of 2.16 GHz. The modulation types follow the WirelessHD1.1 specifications [7] allowing for binary phase shift keying (BPSK), QPSK, and 16-QAM. The HMD receiver is equipped with a phase array antenna to compensate for the translational and rotational movements of the users such that a directional communication link to the PC transmitter is maintained. It receives the WirelessHD signal and recodes it into an HDMI video signal for further processing and display at the HMD. This setting provides a data rate of up to 28 Gbps for high quality 2K (2160 \(\times\) 1200 pixels) video transmission with ultra-low latency of below 2 ms. In addition, a wireless link in the 5 GHz band is used with the AP to relay control data between PC transmitter and HMD receiver. * **Server:** An Alienware 17 R4 gaming laptop with an Intel Core i7-7820 HK CPU of 2.90 GHz clock rate, 32 GB RAM and a GeForce GTX 1080 GPU was used as server. The WirelessHD video signal of the 2K video at an actual rate of 89.53 frames per second (fps) is produced at the server to be transmitted to the HMD. * **Splitter:** The ATEN 4K HDMI splitter devides the HDMI signal released by the TPCAST receiver into two data streams for distribution to the HMD and the monitoring unit. The splitter ensures that both units receive the same signal, one processed at the HMD for video diplay and the other used for video freeze detection at the monitoring unit. Figure 4: Hardware components of the TPCAST wireless VR testbed: (**a**) Transmitter and IR tracking (top) and server along with operators (right), (**b**) HMD holding the TPCAST receiver and splitter mounted on the full-swived chair, (**c**) Monitoring equipment (top) and full-swived chair placement (bottom). Figure 3: Block diagram of the TPCAST wireless VR testbed (Tx,v: Transmitter of the 60 GHz video link, Rx,v: Receiver of the 60 GHz video link, Tx,c: Transmitter of the 5 GHz control link, Rx,c: Receiver of the 5 GHz control link). * **HMD:** The video test stimuli were shown on an HTC Vive HMD which provides a resolution of \(1080\times 1200\) pixels per eye, a \(110^{\circ}\) field of view, and runs at a refresh rate of \(90\,\mathrm{Hz}\). * **IR tracking:** In this experimental study, the SteamVR tracking with Vive base stations 1.0 was used for the HMD to position itself in the 3D space. * **Monitoring:** The HTC Vive HMD is equipped with a TPCAST wireless adapter that releases the HDMI signal needed for the identification of video freezes.