# QoE Model

QoE is to measure users’ satisfactory when multimedia services are provided. In this chapter, due to the feature of media cloud, we present a QoE model by defining the obtained cloud processing rate of r, where *Q(r) = h(r).* Moreover, based on [42], we assume that the QoE function has the following properties:

- •
*h(r)*is positive; - •
*h(r)*is concave with respect to*r*; - •
*h(r)*is continuous and twice differentiable for*r*.

Note that user’s QoE follows the logarithmic law and QoE function can be modeled in the logarithmic form for applications of multimedia task [43]. Therefore, we adopt the QoE model as the logarithmic function, which is defined as

where *a* and *в* are two constant parameters. Both of them are positive and can be different for various types of applications. Parameter q_{max} is the maximum of QoE when user obtains the highest processing rate r_{max}, and parameter q_{min} is the minimum of QoE when user obtains the lowest processing rate *r*min.

As QoE function is continuous, r_{min} can be obtained by

Similarly, r_{max} can be obtained by

# Design Goals

Our design goals have two desirable objectives as follows: on one hand, user can obtain sufficient cloud resource from media cloud to achieve a satisfied QoE. On the other hand, media cloud can achieve the maximum profit with an optimal price of cloud price.