Resource Allocation in Time-Division-Multiplexed Networks on Chip

O ne of the challenges of engineering is to make the best possible use of the available resources, or in other words allocating the resources in such a way as to maximize the overall profit. In the context of networks on chip the resources are represented by the communication bandwidth and the final profit is the performance of an application supported by the network on chip. In this thesis we focus on networks on chip providing guaranteed performance, i.e. guaranteeing for each application the delivery of a requested bandwidth. In these networks, hardware resources are allocated and assigned to each application for its entire lifetime. We discuss several solutions for delivering the allocated bandwidth, and we propose models which allow us to evaluate the performance of these solutions. Starting from a general, rate-based allocation model we gradually add more architectural restrictions that lower the implementation cost, but at the same time sacrifice some performance. NoCs with allocation based on discrete rates are very common and include priority-based, TDM, SDM, FDM, and other NoCs. They all partition the bandwidth available on the network links into discrete units. In the case of TDM NoCs these units are called time slots. The problem of resource allocation in TDM NoCs consists of finding paths through the network between the nodes that wish to communicate, and selecting along these paths a set of free time slots that is sufficiently large to fulfill the application requirements. After allocation the bandwidth is guaranteed. In this thesis, we propose, implement and evaluate allocation algorithms for all the proposed performance models. Particular effort is dedicated to allocation algorithms for the contention-free routing model, a restrictive, but low-cost form of TDM where allocation is particularly challenging. Our allocation algorithms deal both with spatial allocation, i.e., the selection of a specific path out of the available paths through the network, and temporal allocation,