Dynamic Traffic Distribution Among Hierarchy Levels in Hierarchical Networks-on-Chip (NoCs)

As the number of modules grows, performance scalability of planar topology networks-on-chip (NoCs) becomes limited due to the increasing hop-distances. The growing hopdistance affects both end-to-end network latency and overall network saturation. Hierarchical topologies provide better traffic hop distance and therefore are more adequate for large systems. However, the introduction of hierarchical NoCs introduces new challenges, in particular, how to distribute the traffic among the hierarchy levels. An efficient traffic distribution mechanism is essential for effective utilization of the hierarchical structure. In this paper we propose a dynamic traffic distribution scheme that adapts traffic distribution among the hierarchy levels to the changing traffic conditions. We evaluate our scheme with packetaccurate simulations and show that it enables to realize the potential of hierarchical NoCs in latency reduction under both light and heavy traffic loads. Keywords—Hierarchical networks on chip; Adaptive routing;