Abstract :
Private Mobile Radio PMR the traditional two way radio service provides a vital communication service for government and professional users. Some PMR services are similar to those provided by cellular telephony systems, such as GSM. However, some services are very different; and this leads to differences in the way that security needs to be implemented to protect the services, and ultimately the network itself. This paper explores the similarities and differences between PMR systems and telephony services. It uses TETRA, the European standard for digital PMR systems, as its model, and compares this where relevant with the security mechanisms in GSM.