Spatially disjoint source channel coding: taking advantage of the current dial-up architecture for video over the Internet

We present a new and powerful approach for transmitting video over the Internet via dial-up modem links. Currently, the source and channel coding are both done in the user PC. In fact, joint source channel coding has become quite popular. In strong contrast to this, we propose to spatially separate the source and channel coding so that the source coding is performed in the user PC and the channel coding is performed in the remote access concentrator. This results in significantly improved video quality since the modem connection has a very small packet loss rate compared to the Internet. In addition, the bit rate of the modem connection is fixed and much lower than the potentially available bit rate of the Internet. Clearly, using a channel coding scheme powerful enough to protect against the high packet loss rate of the Internet is not necessary for the modem connection, and in fact, it is a waste of the already very constrained modem connection bandwidth. By moving the channel coding from the user PC to the remote access concentrator, we free up bits on the highly reliable modem link for the source coding, which in turn results in a compressed video of higher quality. In the remote access concentrator we then employ a channel coding scheme which increases the overall bit rate but also makes the real time stream robust to the highly likely packet drops in the Internet.