  In the past few decades, optical transport networks (OTNs) have undergone
significant evolution, from the earliest wavelength-division multiplexing (WDM)
OTNs to elastic optical networks (EONs) and later to space-division
multiplexing (SDM) OTNs, to address the continuous growth of Internet traffic.
By 2024, Pbps-level OTNs are expected, far exceeding the capacity limit of
single-mode fibers. The massive SDM era is on the horizon. In this context,
newly designed OTNs called spatial channel networks (SCNs), which achieve high
cost efficiency by means of practical hierarchical optical cross-connects, have
recently been proposed. However, the evolution of OTNs will simultaneously
present challenges related to resource allocation in networking. For instance,
with the evolution from WDM-OTNs to EONs, the resource allocation problem was
transformed from the routing and wavelength assignment (RWA) problem to the
routing and spectrum assignment (RSA) problem due to the additionally
introduced constraint of spectrum contiguity. Similarly, specially designed
algorithms are also expected to be essential for addressing the resource
allocation problem in SCNs. In this paper, we define this new problem as the
routing, spatial channel, and spectrum assignment (RSCSA) problem. We propose
an integer linear programming (ILP) model and a heuristic algorithm to solve
the RSCSA problem. We examine the performance of the proposed approaches via
simulation experiments. The results show that both proposed approaches are
effective in finding the optimal solutions or solutions close to the lower
bounds. To the best of our knowledge, this is the first work to focus on the
problem of resource allocation in SCNs.
