  In this paper, we explore the information-theoretic optimality of treating
interference as noise (TIN) in cellular networks. We focus on uplink scenarios
modeled by the Gaussian interfering multiple access channel (IMAC), comprising
$K$ mutually interfering multiple access channels (MACs), each formed by an
arbitrary number of transmitters communicating independent messages to one
receiver. We define TIN for this setting as a scheme in which each MAC (or
cell) performs a power-controlled version of its capacity-achieving strategy,
with Gaussian codebooks and successive decoding, while treating interference
from all other MACs (i.e. inter-cell interference) as noise. We characterize
the generalized degrees-of-freedom (GDoF) region achieved through the proposed
TIN scheme, and then identify conditions under which this achievable region is
convex without the need for time-sharing. We then tighten these convexity
conditions and identify a regime in which the proposed TIN scheme achieves the
entire GDoF region of the IMAC and is within a constant gap of the entire
capacity region.
