  This paper addresses the problem of worst-case timing analysis of
heterogeneous wormhole NoCs, i.e., routers with different buffer sizes and
transmission speeds, when consecutive packet queuing (CPQ) occurs. The latter
means that there are several consecutive packets of one flow queuing in the
network. This scenario happens in the case of bursty traffic but also for
non-schedulable traffic. Conducting such an analysis is known to be a
challenging issue due to the sophisticated congestion patterns when enabling
backpressure mechanisms. We tackle this problem through extending the
applicability domain of our previous work for computing maximum delay bounds
using Network Calculus, called Buffer-aware worst-case Timing Analysis (BATA).
We propose a new Graph-based approach to improve the analysis of indirect
blocking due to backpressure, while capturing the CPQ effect and keeping the
information about dependencies between flows. Furthermore, the introduced
approach improves the computation of indirect-blocking delay bounds in terms of
complexity and ensures the safety of these bounds even for non-schedulable
traffic. We provide further insights into the tightness and complexity issues
of worst-case delay bounds yielded by the extended BATA with the Graph-based
approach, denoted G-BATA. Our assessments show that the complexity has
decreased by up to 100 times while offering an average tightness ratio of 71%,
with reference to the basic BATA. Finally, we evaluate the yielded improvements
with G-BATA for a realistic use case against a recent state-of-the-art
approach. This evaluation shows the applicability of G-BATA under more general
assumptions and the impact of such a feature on the tightness and computation
time.
