  The resource allocation in SC-FDMA is constrained by the condition that
multiple subchannels should be allocated to a single user only if they are
adjacent. Therefore, the scheduling scheme of a D2D-cellular system that uses
SC-FDMA must also conform to the so-called adjacency constraint. This paper
proposes a heuristic algorithm with low computational complexity that applies
proportional fair (PF) scheduling in the D2D-cellular system. The proposed
algorithm consists of two main phases: i) subchannel allocation and ii)
adjustment of data rates, which are executed for both CUEs and DUEs. In the
subchannel allocation phase for CUEs (or D2D pairs), the users' data rates are
maximized via optimal power allocation to frequency-contiguous subchannels. In
the second phase, a PF scheduling problem is solved to decide the modulation
and coding scheme (MCS) of both CUEs and D2D pairs. Both phases of the proposed
algorithm benefit from the Water-Filling (WF) technique. The simulation results
suggest that the proposed scheme performs similarly to optimal PF scheduling
from the perspective of users' data rate and their logarithmic sum. An
additional benefit of the proposed scheme is its low computational overhead.
