# Survey on Quality of Experience Evaluation for Cloud-Based Interactive Applications
## 6 Stages of the Quantification of QoE in CIAs
### Input Stage
These proposals measured the frequency of graphical updates, either when sent by the server or received by the client, as well as the percentage of the user's screen updated by each primitive. Other proposals opted for light-intensity measurements. This source of information was interesting in cases where researchers could not instrument the client, network, or cloud server. Some authors used comparative light-intensity measurements to detect the frequency with which changes occurred on the screen. To obtain metrics or information sources from sound perception, the information sources are the sound content reproduced by the CIA. When the proposals obtained the audio from the client, they obtained information related to the user's final reception. However, proposals that obtained audio from the cloud server extracted information prior to any sound degradation generated by the infrastructure. The authors sometimes chose to use both sources of audio information in combination. \begin{table}
\begin{tabular}{c c c c c c c c c c c c c c c c c c c} \hline \hline  & \multicolumn{10}{c}{**Additional Content**} & \multicolumn{10}{c}{**Device Resource**} & \multicolumn{10}{c}{**Network**} \\ \cline{2-13} \multicolumn{1}{c}{**Ref. **} & \multicolumn{3}{c}{**User Feedback**} & \multicolumn{3}{c}{**User Feedback**} & \multicolumn{3}{c}{**User Feedback**} & \multicolumn{3}{c}{**User Feedback**} & \multicolumn{3}{c}{**User Feedback**} \\ \cline{3-13}  &  
For device resource information, Table 5 groups the eight related input metrics. Some researchers derive metrics from the source information of the computational resources of the architecture elements. The most common metrics are CPU, GPU, RAM, and disk usage. Another source of information is user input. Some researchers obtain metrics related to when the user interacts with their devices via a keyboard or mouse. User input is one source of information that provides metrics on when they occur, how often they occur, the type of action performed (e.g., a mouse click or a key press), and the locations of the interactions (mouse coordinates). Another source of information is the system calls that applications use to communicate with the operating system. Some approaches choose to monitor the input and output (I/O) of these calls to evaluate the content, their frequency, or the time elapsed between the system receiving the input and generating the output. Some researchers use not only these times as a source of information but also the behaviour of the executed processes as input metrics. This source of information is different from I/O calls, as it allows the tools to obtain metrics of applications: the physical resources it uses, the libraries it calls during its operation, and the execution times of its internal processes. Some authors extract the I/O and process information from both the client and cloud server through the APIs of their OS. Another source of information is the source code of the applications that the literature uses to obtain metrics related to their behaviour. Using the source code, some proposals calculate, among other things, metrics such as the rendering time of an element of a web application, the time at which a certain response is sent or received by the client, or when a screen update order is sent or received. This source of information requires instrumenting the applications (APM). The network allows input metrics to be obtained from the traffic generated by the CIA. Some approaches monitored traffic to obtain network traffic metrics, such as bit rate, packet rate, timestamps, or IP addresses present in the traffic. Other proposals used the raw content of network packets. This source of information requires knowledge of the communication protocol in use to extract parameters from the messages exchanged between the client and the cloud server. This enables the determination of the specific packet that contains a screen update, a user action, or the compression codec used in the CIA.