  The algebraic formulation for linear network coding in acyclic networks with
the links having integer delay is well known. Based on this formulation, for a
given set of connections over an arbitrary acyclic network with integer delay
assumed for the links, the output symbols at the sink nodes, at any given time
instant, is a \mathbb{F}_{q}$-linear combination of the input symbols across
different generations, where $\mathbb{F}_{q}$ denotes the field over which the
network operates. We use finite-field discrete fourier transform (DFT) to
convert the output symbols at the sink nodes, at any given time instant, into a
$\mathbb{F}_{q}$-linear combination of the input symbols generated during the
same generation. We call this as transforming the acyclic network with delay
into {\em $n$-instantaneous networks} ($n$ is sufficiently large). We show that
under certain conditions, there exists a network code satisfying sink demands
in the usual (non-transform) approach if and only if there exists a network
code satisfying sink demands in the transform approach. Furthermore, we show
that the transform method (along with the use of alignment strategies) can be
employed to achieve half the rate corresponding to the individual
source-destination min-cut (which are assumed to be equal to 1) for some
classes of three-source three-destination unicast network with delays, when the
zero-interference conditions are not satisfied.
