Multi-User Preemptive Scheduling For Critical Low Latency Communications in 5G Networks

5G new radio is envisioned to support three major
service classes: enhanced mobile broadband (eMBB), ultrareliable low-latency communications (URLLC), and massive machine type communications. Emerging URLLC services require
up to one millisecond of communication latency with 99.999%
success probability. Though, there is a fundamental trade-off
between system spectral efficiency (SE) and achievable latency.
This calls for novel scheduling protocols which cross-optimize
system performance on user-centric; instead of network-centric
basis. In this paper, we develop a joint multi-user preemptive
scheduling strategy to simultaneously cross-optimize system SE
and URLLC latency. At each scheduling opportunity, available
URLLC traffic is always given higher priority. When sporadic
URLLC traffic appears during a transmission time interval
(TTI), proposed scheduler seeks for fitting the URLLC-eMBB
traffic in a multi-user transmission. If the available spatial
degrees of freedom are limited within a TTI, the URLLC traffic
instantly overwrites part of the ongoing eMBB transmissions
to satisfy the URLLC latency requirements, at the expense of
minimal eMBB throughput loss. Extensive dynamic system level
simulations show that proposed scheduler provides significant
performance gain in terms of eMBB SE and URLLC latency.