Error Resilient Transmission of Video over Mobile Networks

The deployment of third generation mobile networks enabled new real-time multimedia services like video call, conferencing and streaming. The real-time nature of these services excludes the possibility of end-to-end retransmissions. Therefore, errors affecting the quality of the received service are inevitable. The aim of error resilience methods is to minimize the impact of errors on the end-user quality. In this talk, the effect of errors at different positions in the video stream and the possibility of their detection will be discussed. Typically, within an IP video stream, the presence of errors in one IP packet can be detected by means of a simple checksum. Thus, the IP packet size determines the resolution of the error detection. In order to reduce the rate increase due to packet headers, the IP packets are rather large and their loss results in a loss of a considerable part of a picture. Currently, the erroneous IP packets are discarded at the receiver and the corresponding missing parts of the video sequence are concealed. However, the discarded IP packets may still contain correctly received information. If this information is used additionally, an essential improvement in the end-user quality can be obtained. If the access network technology is known, an appropriate cross-layer design enables easier error detection and allows for further improvements of error resilience. In this talk, the UMTS access network is focused. Error resilience methods can be further improved by an appropriate scheduling of the video stream. Here, link-error aware and distortion-aware concepts and their combinations will be discussed and their performance demonstrated.