  Motivated by streaming multi-view video coding and wireless sensor networks,
we consider the problem of blockwise streaming compression of a pair of
correlated sources, which we term streaming Slepian-Wolf coding. We study the
moderate deviations regime in which the rate pairs of a sequence of codes
converge, along a straight line, to various points on the boundary of the
Slepian-Wolf region at a speed slower than the inverse square root of the
blocklength $n$, while the error probability decays subexponentially fast in
$n$. Our main result focuses on directions of approaches to corner points of
the Slepian-Wolf region. It states that for each correlated source and all
corner points, there exists a non-empty subset of directions of approaches such
that the moderate deviations constant (the constant of proportionality for the
subexponential decay of the error probability) is enhanced (over the
non-streaming case) by at least a factor of $T$, the block delay of decoding
source block pairs. We specialize our main result to the setting of streaming
lossless source coding and generalize this result to the setting where we have
different delay requirements for each of the two source blocks. The proof of
our main result involves the use of various analytical tools and amalgamates
several ideas from the recent information-theoretic streaming literature. We
adapt the so-called truncated memory encoding idea from Draper and Khisti
(2011) and Lee, Tan, and Khisti (2016) to ensure that the effect of error
accumulation is nullified in the limit of large blocklengths. We also adapt the
use of the so-called minimum weighted empirical suffix entropy decoder which
was used by Draper, Chang, and Sahai (2014) to derive achievable error
exponents for symbolwise streaming Slepian-Wolf coding.
