# Error Recovery in the Time-Triggered Paradigm with FTT-CAN
## 6 Results and Discussion  
To test the methodology presented in the previous sections we used several benchmarks obtained from the literature. One is the _Updated_SAE_[32], a revised and updated version of the SAE Benchmark [33], which takes into account new modules and functionalities present in 21 st century cars. The SAE benchmark is a well-known reference, used in several projects and tools, for instance, in [13; 34]. We have also used the _PSA_ benchmark [35], and one for an electric prototype vehicle _VEIL_[36]. For the sake of completeness, in Appendix B, the message sets of these three benchmarks are presented.  
The _Updated_SAE_ message set was used to obtain the individual WCRT of all the messages when considering the Aggressive environment, with \(\lambda\) = 0.26 errors per second. The CAN bit rate is 1 Mbps and LEC was set to 2.5 ms, corresponding to half of the period of the fastest messages, to allow time for their retransmission. If the message set is schedulable for this environment, it is also for the other ones, which have a lower \(\lambda\), since the interference due to the server execution is lower.  
Firstly, we compute LSW using Algorithm 5. The Algorithm 5 triggers the execution of the algorithms described in Section 5 that produce values that are interesting to analyze. For instance, the maximum errors in one cycle (_max_Icycle_) and the maximum consecutive cycles with single errors (_max_cycles_) are both 4. In these conditions, Algorithm 1 returns _RepLevel_ = {3, 3, 2, 1}, so the interference pattern array is:  
\[\textit{Interf\_P}=\{\,3,3,\,3,\,3,\,3,\,3,\,6,\,0;\,3,\,6,\,3,\,0;\,3,\,6,\,0, \,0;\,6,\,3,\,3,\,0;\,6,\,6,\,0,\,0;\,6,\,3,\,0,\,0;\,4,\,0,\,0,\,0\,\}\]  
With the error server configured according to the description in Section 4.3, with \(T_{S}=1/\lambda\) seconds (1538 ECs), C\({}_{\rm S}\) equal to 12 \(\times\) 3 \(\times\) _CMAX_ and _RepLevel_, as presented in the previous paragraph, the minimum LSW value is equal to 55.1% of the LEC to schedule the message set, including the error server. This algorithm, implemented in MatLab and using a Pentium i7-2670 QM computer with 6 GB of memory, took less than 1 second to complete, with 0.1% precision as stopping criterion.  
The diverse interference patterns and WCRT for each message are presented in Figure 9, where the \"0 errors\" column is included for reference, presenting the response times in the absence of errors.  
As expected, the results show a degradation of the WCRT in almost all messages, when compared with the no errors scenario. The first eight messages have a penalty of one EC, since they fit in the EC, in which they become ready, even when the server executes. The messages with lower priorities, e.g., 30 to 36, suffer a stronger response time penalty as they are affected by a higher interference level.  
Figure 9 also confirms that Direct Interference normally dominates Indirect Interference. This is the case in our test scenario. However, even with the same message set but with _RepLevel_ equal to  
Figure 9: Response time for every message in the _Updated_SAE_ set, using each possible interference pattern, when considering Indirect and Direct Interference.  
4, 3, 2, 1] there were already cases in which Indirect Interference dominated. This confirms the need to always compute both kinds of interference to determine a safe upper bound to the WCRT.