# Survey on Quality of Experience Evaluation for Cloud-Based Interactive Applications
## 1 Introduction  
Cloud computing is a growing computing paradigm [1] that promises on-demand computing resources. It is possible to differentiate between three types of cloud deployments: public clouds, private clouds, and hybrid clouds. In the public cloud, an off-site third-party provider offers computing resources and management. These resources are accessed through the Internet. In this paradigm, there are new billing schemes whereby customers pay for the use of the infrastructure. Users can access high-power computational resources from client machines, with the only requirement being a connection to the Internet. Thus, individuals and companies can reduce the cost of deploying and maintaining their computing infrastructures by delegating system maintenance to the cloud service provider, which offers infrastructures with high bandwidth and low latency [2]. In contrast, the private cloud refers to computing resources within a private network. Private clouds are for the exclusive use of a single customer, and the customer's service administrators manage computational resources. On the other hand, hybrid cloud computing offers an infrastructure in which public and private clouds communicate with each other, sharing data and applications between them. Although the use of private clouds has been widespread within the industry, the migration from private clouds to hybrid or public clouds is booming. In particular, the costs associated with the public cloud and the data protection policies of each country make the hybrid cloud option attractive [3]. In this article, we focus on cloud-based interactive applications(CIAs) [4], also known as cloud-based distributed interactive applications (CDIAs) [5] or real-time interactiveapplications (RIAs) [6]. CIAs are applications running in the cloud with strict interactivity requirements. Users expect a near real-time response to their actions, which occur through keystrokes or mouse clicks. The response leads to a screen update so fast that the user cannot perceive that the application is not running locally. CIAs can be deployed on any type of cloud. The existing literature identifies three types of CIAs: remote desktop services, cloud gaming services, and interactive web applications [5]. Services such as video on demand or voice over IP are not considered CIAs because they do not involve interactions as defined above. They use streams of audio/video data with temporal requirements but without requirements about how the user interacts with the service. The International Telecommunication Union (ITU-T) defines quality of experience (QoE) as \"the overall acceptability of an application or service, as perceived subjectively by the end-user\" [7]. [PERSON] et al. defined QoE as \"a blueprint of all human subjective and objective quality needs and experiences arising from the interaction of a person with technology and with business entities in a particular context\" [8]. One of the main network metrics related to the QoE in CIAs is the time elapsed from when the user interacts with the application until receiving a graphical response. This metric is called the interactivity time [9] or responsiveness [10]. Increased interactivity time can reduce the usability of a CIA. In traditional desktop applications or local services not deployed in the cloud, interactivity time is important. However, in the case of CIAs, servers can be located further away from the user, thus increasing interactivity time, at least on a scale directly proportional to the round-trip time (RTT). In addition, the sharing of remote servers can lead to slow applications. These services can be considered elastic because the perception of interactivity time is gradual and influenced by network and service conditions [11]. Other metrics that influence the QoE are the quality of the video image and, to a lesser extent, audio quality. Ensuring quality of experience (QoE) in interactive services is of great interest to service providers.