# Off-Cloud Anchor Sharing Framework for Multi-User and Multi-Platform Mixed Reality Applications
## 5 Experiments
### Second Experiment: Remote HoloLens-PC Communication  
To further evaluate the robustness and scalability of the proposed framework, a second experiment using a Wide Area Network (WAN) was designed to test the device interactions with less ideal network conditions than in a controlled LAN. The aim of this experiment was--similarly to the first experiment--to measure the time required for transmitting and loading spatial anchors of multiple sizes. In order to achieve this, the experiments were conducted using a Microsoft HoloLens 2 HMD, a Windows 10 desktop computer and TP-LINK and Zte H3600P routers with the following configuration:  
* Microsoft HoloLens 2 (Qualcomm Snapdragon 850, Wi-Fi (IEEE 802.11 ac (2x2)), 4 GB of LPDDR DRAM). * Routter: TP-LINK Archer C5400 (IEEE 802.11 ac), 2.4 GHz connection. * Desktop computer: Windows 10 (Intel Core i7-960 3.20 GHz (4 cores) CPU, 12 GB RAM and graphic card NVIDIA GeForce GTX 660). * Routter: Zte H3600P (IEEE 802.11 a/x), Ethernet connection. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**\# Exp** & **Anchor Size (MB)** & **Server Exporting** & **Anchor Transmission Time (s)** & **Client Loading Time (s)** \\ \hline
1—Small Anchors & 3.40 (\(\pm\)0.21) & 0.4479 (\(\pm\)0.27) & 12.8068 (\(\pm\)0.04) & 0.8019 (\(\pm\)0.10) \\ \hline
2—Medium Anchors & 6.40 (\(\pm\)0.22) & 0.3765 (\(\pm\)0.20) & 26.0065 (\(\pm\)0.05) & 1.5944 (\(\pm\)0.18) \\ \hline
3—Big Anchors & 10.5 (\(\pm\)0.20) & 0.9910 (\(\pm\)0.53) & 43.4579 (\(\pm\)0.07) & 2.7862 (\(\pm\)0.70) \\ \hline
4—Room-Sized Anchors & 20.4 (\(\pm\)0.25) & 1.2923 (\(\pm\)0.31) & 85.7326 (\(\pm\)0.19) & 5.3937 (\(\pm\)0.64) \\ \hline \hline \end{tabular}
\end{table} 
Table 1: First experiment (local): average values and standard deviation for anchor size and operation times for each experiment scenario. Figure 8: Transmission and client loading times regarding anchor size for each experiment execution. Following the same procedure as for the first experiment, four scenarios were created, each one using a different anchor size: small, medium, big and room-sized. For each scenario, the experiment was repeated 20 times, recording the following key metrics: transmission time from server to the client and time taken by the client to load the received anchor into the scene. In this set of experiments, there was no need to create and to export the anchor nor track these times on the server-side because the application was executed on a desktop computer with no MRTK and spatial anchor capabilities. Thus, the task performed by the server was to store an anchor in local memory and to transmit it whenever the client requested a new anchor. For each of the four scenarios, a random anchor created in the first experiment was selected and stored in the server prior to the initiation of each set of tests. The obtained results were analyzed and are summarized in Table 2, where the average times and standard deviations are detailed for each anchor size scenario. For the smallest anchor size (3.0 MB), transmission times ranged between 12.69 and 12.84 s, where the anchor loading time remained below 1 s in most cases. In the next scenarios, as anchor complexity increased, both the transmission and loading times also rose. In the case of medium-sized anchors (6.0 MB), transmission times were required to be from 25.62 to 25.74 s and between 1.39 and 2.13 s to be loaded. For an anchor of 10.1 MB, transmission times ranged between 43.36 and 43.63 s, with loading times from 2.36 to 3.38 s. Finally, room-sized anchors (20.1 MB) required the highest performance demands, with transmission times ranging between 85.57 and 87.18 s and loading times exceeding 4.74 s and even reaching 6.75 s.  
These data can be compared with those obtained during the LAN experiments (Table 1), and it can be concluded that for the same anchor sizes, the response times are very similar. Therefore, not much difference is perceived in the performance of the framework between LAN and WAN execution.