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 hop-distance 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 offers new challenges. In particular, how to distribute the traffic among the hierarchy levels to effectively utilize 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 packet-accurate simulations and show that it enables to realize the potential of hierarchical NoCs in latency reduction under both light and heavy traffic loads.