Toward Predictable Deflection Routing in Routerless NoCs for Real-Time Systems

Contention between packets on shared resources, such as ejection links, causes high latency on routerless Networks-On-Chip. Missing packet timing guarantees due to high latency render a real-time application unschedulable. Deflection routing is a mechanism that addresses contention when multiple packets try to access the same links simultaneously. Despite its benefits, packets may be deflected more than what their timing guarantees allow in the worst-case scenario. To achieve an upper bound of deflections in conjunction with mapping, we proposed two methods: first, a method that increases the deflections of all communication flows, and second, a method that increases the deflections based on selective communication flows. Our findings, based on running both methods in an evolutionary optimisation, show that the latter outperformed the former, with a statistically significant improvement in the maximum deflection.