In methods and devices for providing a guaranteed quality of service to a subscriber of a service in a cellular radio system, a start position and an end position are received along with a required quality of service, QoS. Cell site positions are associated with possible user geographical/street paths that will take the subscriber from the start position to the end position and search for paths that will guarantee the required QoS. Based on the search the path that best satisfies the entered input criteria is selected and output to the subscriber.