This paper deals with the study of the uplink mechanisms of medium access within a UTRA system, which offers the possibility of holding on to voice and data services. The voice service is beamed off through a dedicated channel whereas a common channel is used for a very widespread service nowadays like the web traffic. The first investigations on homogeneous systems reveal that the access channel is longer occupied in the data system than in the voice system. The simulations related to the integrated voice and data system show that, in spite of the fact that the voice experiences a greater delay than in the homogeneous system, the QoS parameters for voice and data are guaranteed with no need to use all the available system resources. Following this, the integrated system allows for certain losses in the common RACH (Random Access Channel).