Gateway Optimization for an Heterogeneous avionics network AFDX-CAN

The gateway impact on the end to end system performances is a major challenge in the design process of heterogeneous embedded systems. In this paper, this problem is tackled for a specific avionics network AFDX with CAN to identify the main interconnection issues. The results herein show the possible enhancements of the system performances thanks to an optimized gateway based on a frames pooling strategy, compared to a basic gateway. Keywords-heterogeneous embedded networks; CAN; AFDX; gateway; performance analysis; optimization I. CONTEXT AND RELATED WORKS During the last few decades, many specific data buses have been successfully implemented in various critical embedded applications like CAN [1] for automotive and ARINC 429 [2] for civil avionics. However, with the increasing complexity of interconnected subsystems and the expansion of exchanged data quantity, these data buses may be no longer effective in meeting the emerging requirements of the new embedded applications in terms of bandwidth and latency. In order to handle this problem, the current solution consists in increasing the number of used data buses and integrating dedicated data buses with higher rates like FlexRay [3] for automotive and AFDX [2] for civil avionics. Using these different data buses makes global interconnection system heterogeneous and requires special gateways to handle the problem of existent dissimilarities between the subnetworks. This clearly leads to increasing communication latencies and making real-time constraints guarantees difficult to prove. Hence, the gateways characteristics analysis and their impact on the end-to-end performances become one of the major challenges in the design process of multi-cluster embedded systems. Various approaches are recently offered to handle the problem of design space exploration and optimization of heterogeneous embedded networks. Nevertheless, these proposed approaches have often ignored the gateways impacts on the systems performances. In this specific topic, the approach of Pop et al. [4] focuses on the optimization of multi-cluster embedded systems interconnected via gateways to find a system configuration satisfying the different temporal constraints. The gateway was considered as a simple frames converter and the issue of optimizing this interconnection function was not tackled. Another paper [5] deals with the same problem in the specific case of Ethernet and CAN interconnection by predicting average flows latencies using simulation. The aim of this paper is first to identify the main challenges concerning the interconnection function in heterogeneous embedded systems and its impacts on the end to end system performances, through a representative avionics case study which consists in interconnecting an AFDX network with CAN buses. Then, in order to enhance the bandwidth utilization and delivered Quality of Service on the AFDX network, we proceed to the interconnection function optimization to determine an accurate frames pooling strategy that fulfills the system requirements. In the next section, the avionics case study is described and the main interconnection function issues are detailed. Then, in section 3, the definition of a basic gateway and the end-to-end performance analysis are presented. The obtained results through the case study lead to some identified limitation of this proposal towards the bandwidth utilization on the AFDX and to overcome this problem a gateway optimization process is proposed in section 4. II. AVIONICS CASE STUDY: AFDX-CAN