ered as the default. The smallest time-domain scheduling resolution for the MAC scheduler is mini-slot, but it is also possible to schedule users on slot resolution, or on the resolution of multi- ple slots. Thus, dynamic scheduling with different TTI sizes is supported. This enables the MAC scheduler to more efficiently match the radio resource allocations for different users in coherence with the radio condition, QoS requirements, and cell load conditions. The short transmission time is needed for Ultra-Reliable Low Latency Communication (URLLC) use cases, but is not restricted to such traffic. In the frequency domain, the minimum scheduling resolution is one physical resource block of 12 subcarriers, corre- sponding to 180 kHz for 15 kHz subcarrier spacing and 360 kHz for 30 kHz spacing. The MAC scheduler can freely decide how to schedule its different users on the carriers, and it is not visible to the RLC layer how this is done. But it is possible to enforce some restric- tions via higher-layer control signaling to schedule data from certain bearers only on a given physical numerology, and a certain transmission size. Each scheduling allocation is sent to the UE via the downlink control channel carrying the scheduling grant. The downlink control channel is flexibly time-frequency-multiplexed with the other down- link physical channels, and can be mapped contiguously or non-contiguously in the frequency domain. This constitutes a design where the relative downlink control channel overhead can take values from below 1% values if, for example, scheduling few users with a long transmission time, and up to tens of percentages if scheduling a larger number of users with a very short transmission time. The design therefore overcomes the con- trol channel blocking problems. These advantages are achieved by migrating toward a user-centric design, as compared to the predominantly cell-centric LTE design. Another advantage brought about by the more flexible 5G downlink control channel design is the 10 5G Performance su