# ATWin: An Improved and Detailed Startup Model of TTP/C
## 3 The Proposed Startup Model ATWin
### The Startup Model ATWin  
**A. The startup process of ATWin**  
The state transition diagram of the ATWin model is presented in Figure 5. For the different contention scenarios, the proposed startup model innovatively subdivides the LISTEN state and the COLDSTART state into multiple sub-states based on the standard startup model. Specifically, the LISTEN state is partitioned into four sub-states, while the COLDSTART state is divided into six sub-states. The specific meaning, action and duration of the sub-states proposed in this paper are provided in Table 3. \begin{table}
\begin{tabular}{p{42.7 pt} p{113.8 pt} p{113.8 pt}} \hline \hline
**Category** & **Annotation** & **Explanation** \\ \hline C1 & The node receives only one frame within the ATW, and the frame is a valid cold-start frame. & The node cannot determine whether contention has occurred or not. \\ \hline C2 & The node receives multiple frames within the ATW, and the first one is a valid cold-start frame. & The node can determine the occurrence of contention. \\ \hline C3 & The node receives overlapping frames within the ATW and then turns off its receiver because the first frame is invalid. & The node can determine the occurrence of contention. \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Contention scenarios from the perspective of a node in a TTP/C cluster during startup. The time duration of ATW is denoted as \(\Delta_{window}\), and the contention flag is denoted as \(cflag\). When the ATWin model starts, the value of \(cflag\) defaults to 1, indicating that there is contention. When its value becomes 0, it indicates that there is no contention. In Figure 5, the two states highlighted in gray are the INIT state and the SYNC state. The INIT state represents the system initialization phase and marks the beginning of the TTP/C cluster startup cycle. The SYNC state denotes the state where the system achieves complete startup. The upper identifier of each state indicates its running duration. A value of 0 indicates that the state is merely judged, and its running time can be ignored. The fixed time identifier, such as \(\Delta_{PRP}\) above the state of \(CS_{5}\), indicates that nodes in this state run for a predetermined time, even if the action has already been completed. The predetermined time must be greater than the worst-case execution time of the state action. An identifier with an unequal sign in the figure, such as \(\leq\)\(n\Delta_{slot}\), indicates that the state's duration is at most \(n\Delta_{slot}\), where \(n\) is a statically specified value according to the configuration parameter of the node, and the variation of the duration is in units of slots. The identifier \(\infty\) represents that the state can theoretically last for an infinite amount of time. Table 3 provides the states of the ATWIN startup model, the specific actions to be performed for each state, and the duration. All actions of a state should be completed within the duration of the state. The states marked with diagonal lines in Figure 5 indicate the unconditional transition states. **B. The contention-detecting strategy in ATWin**  
The mandatory contention-eliminating strategy in the standard startup model forces the node to discard the first valid frame according to AS6003, even in the absence of contention. Unfortunately, there is no contention-detecting strategy in the standard startup model. However, under some contention scenarios, there may be no need to discard the first valid frame. Therefore, this paper proposes a novel contention-detection strategy to detect these types of contention scenarios to improve the standard startup model's shortcomings. In our contention-detecting strategy, when a node starts, the listening process is first performed to determine whether it is a sending node or a receiving node. If it is a sending node, it marks the current round of startup as contention and enters the sending process.