  A way to break supersymmetry in perturbative superstring theory is the string
version of the Scherk-Schwarz mechanism. There, the fermions and bosons have
mass splitting due to different compactification boundary conditions. We
consider the implementation of this mechanism in abelian orbifold
compactifications with Wilson line backgrounds. For $Z_N$ and $Z_N\times Z_M$
orbifolds, we give the possible $U(1)$ R-symmetries which determine the mass
splitting, and thus, the supersymmetry breaking at the perturbative level. The
phenomenlogical viability of this mechanism implies some dimension(s) to be as
large as the TeV scale. We explain how the lighter Kaluza-Klein states
associated with the extra-dimension(s) have quantum numbers depending on the
Wilson lines used.
