We consider the source-channel separation architecture for lossy source
coding in communication networks. It is shown that the separation approach is
optimal in two general scenarios, and is approximately optimal in a third
scenario. The two scenarios for which separation is optimal complement each
other: the first is when the memoryless sources at source nodes are arbitrarily
correlated, each of which is to be reconstructed at possibly multiple
destinations within certain distortions, but the channels in this network are
synchronized, orthogonal and memoryless point-to-point channels; the second is
when the memoryless sources are mutually independent, each of which is to be
reconstructed only at one destination within a certain distortion, but the
channels are general, including multi-user channels such as multiple access,
broadcast, interference and relay channels, possibly with feedback. The third
scenario, for which we demonstrate approximate optimality of source-channel
separation, generalizes the second scenario by allowing each source to be
reconstructed at multiple destinations with different distortions. For this
case, the loss from optimality by using the separation approach can be
upper-bounded when a "difference" distortion measure is taken, and in the
special case of quadratic distortion measure, this leads to universal constant
bounds.

本研究探讨了通信网络中利用源信号 - 信道分离编码进行有损信号编码的架构。结果表明，在两种一般情形下，分离方法是最优的，且在第三种情形下近似最优。

网络中源信号与信道分离的最优性及近似最优性

Optimality and Approximate Optimality of Source-Channel Separation in  Networks

This paper describes universal lossless coding strategies for compressing
sources on countably infinite alphabets. Classes of memoryless sources defined
by an envelope condition on the marginal distribution provide benchmarks for
coding techniques originating from the theory of universal coding over finite
alphabets. We prove general upper-bounds on minimax regret and lower-bounds on
minimax redundancy for such source classes. The general upper bounds emphasize
the role of the Normalized Maximum Likelihood codes with respect to minimax
regret in the infinite alphabet context. Lower bounds are derived by tailoring
sharp bounds on the redundancy of Krichevsky-Trofimov coders for sources over
finite alphabets. Up to logarithmic (resp. constant) factors the bounds are
matching for source classes defined by algebraically declining (resp.
exponentially vanishing) envelopes. Effective and (almost) adaptive coding
techniques are described for the collection of source classes defined by
algebraically vanishing envelopes. Those results extend ourknowledge concerning
universal coding to contexts where the key tools from parametric inference

本文研究了针对可数无限字母表上压缩源的通用无损编码策略，探讨了理论通用编码方法在无限字母表上的适用性，给出了上下界分析与编码技术。