Multi level Multiple Descriptions

Multiple description (MD) source coding is a method to overcome unexpected information loss in a diversity system such as the Internet, or a wireless network. While classic MD coding handles the situation where the rate in some channels drops to zero temporarily, thus causing unexpected packet-loss, it fails to accommodate more subtle changes in link rate such as rate reduction. In such case, a classic scheme can¿t use the link capacity left for information transfer, causing even minor rate reduction to be considered as link failure. In order to accommodate such a frequent situation, we propose a more modular design for transmitting over a diversity system, which can handle unexpected reduction in link¿s rate, by downgrading the original description into a more coarse description, so it would fit to the new link¿s rate. The method is analyzed theoretically, and performance results are presented.