The aim of this paper is to empirically evaluate a framework that we have developed on the use of the software quality standard ISO 9126 with the Differentiated Services (DiffServ) Quality of Service (QoS) model to assess the software quality of mobile applications, especially the software usability characteristic. To do that, firstly we have carried out an empirical evaluation of the influence of mobile limitations on Diffserv classes by means of the Sensorly tool. Thereafter, a correlation between the influence of mobile limitations on DiffServ classes and its effects on usability characteristic is discussed. As a result of this empirical study, the usability is less correlated with Diffserv classes in terms of influence of mobile limitations given that this characteristic corresponds to the presentation layer unlike the Diffserv model which would focus on the network level quality.