  The rapid growth in the number and variety of connected devices requires 5G
wireless systems to cope with a very heterogeneous traffic mix. As a
consequence, the use of a fixed TTI during transmission is not necessarily the
most efficacious method when heterogeneous traffic types need to be
simultaneously serviced.This work analyzes the benefits of scheduling based on
exploiting scalable TTI, where the channel assignment and the TTI duration are
adapted to the deadlines and requirements of different services. We formulate
an optimization problem by taking individual service requirements into
consideration. We then prove that the optimization problem is NP-hard and
provide a heuristic algorithm, which provides an effective solution to the
problem. Numerical results show that our proposed algorithm is capable of
finding near-optimal solutions to meet the latency requirements of mission
critical communication services, while providing a good throughput performance
for mobile broadband services.
