The network delay upper-bound analysis problem is of fundamental importance to real-time applications in Networkon-Chip (NoC). In the paper, we revisit a state-of-the-art analysis model for real-time communication in wormhole NoC with priority-based preemptive arbitration and show that the model may provide pessimistic or even incorrect network delay upper-bound. We then propose a revised analysis model to correct the flaws in the previous model by further classifying indirect interference as upstream and downstream indirect interferences according to the relative positions of traffic flows and taking buffer influence into consideration. Simulated evaluations show that our model provides tighter and correct network delay upper-bound compared with the state-of-the-art model.
A novel method is proposed for simulating free-space diffraction propagation. This method is an improvement of the angular spectrum (AS) method and the band-limited angular spectrum (BLAS) method. Due to the sampling problem about the transfer function, AS is not suited for the long-distance propagation. For BLAS, the calculation accuracy would decrease when the propagation distance is relatively large. Using a wide calculation window can largely reduce the numerical error of AS and BLAS. However, a wide calculation window generally causes a huge calculation burden in the simulation. For the proposed method, the calculation window size is chosen to make sure all the sampling points in the frequency domain are effective in the sense of Nyquist theorem. The calculation complexity is independent of the calculation window size because of the use of the linear convolution. The linear convolution can be evaluated effectively by fast Fourier transform. This method can produce simulation results with high accuracy for far and near field propagation.
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