The Sum Rate of Vector Gaussian Multiple Description Coding with   Tree-Structured Covariance Distortion Constraints
  A single-letter lower bound on the sum rate of multiple description coding with tree-structured distortion constraints is established by generalizing Ozarow's celebrated converse argument through the introduction of auxiliary random variables that form a Markov tree. For the quadratic vector Gaussian case, this lower bound is shown to be achievable by an extended version of the El Gamal-Cover scheme, yielding a complete sum-rate characterization. 
Yinfei Xu, Jun Chen and Qiao Wang
cs.IT math.IT