Encrypted video over TETRA

The Terrestrial Trunked Radio (TETRA) system uses end-to-end encryption in addition to the air interface encryption to provide enhanced security. End-to-end encrypted continuous data, such as video, requires synchronisation of the key stream at the receiver to the incoming encrypted data stream from the transmitter. The TETRA system uses a synchronisation technique known as frame stealing to provide synchronisation to end-to-end encrypted data. However, the frame stealing process degrades the quality of video and is not suitable for transmission of secure video. This paper proposes an alternative technique called frame insertion, which is more suitable for video. A technique known as fly wheeling is used to recover from synchronisation problems due to dropped data packets. Further, a method of reducing the synchronisation delay in a video stream is also discussed.