1. A method of estimating the quality of speech information associated with a voice call over a communication system comprising a core network and an access network wherein speech information is carried in frames between the access network and the core network and within the access network, the method comprising the steps of: considering only frames containing speech and ignoring silent frames; determining a rate of frame loss for the considered frames transported between the access network and the core network or within the core network: and, mapping the rate of frame loss to a subjective speech quality estimation value using data collected by simulating frame loss on representative speech samples and determining quality estimation values for the damaged speech samples; wherein said communication system is a Universal Mobile Telecommunications System network; and, wherein the method is implemented at the Radio Network Controller of the access network, wherein said frames are lu frames received from a Media Gateway of the core network.