# ATWin: An Improved and Detailed Startup Model of TTP/C
## 2 Background Work and Literature Review
### Existing Problems  
References [18; 19; 20] verify the correctness of the standard startup model through various model-checking methods, albeit with a limited number of nodes. Reference [14] analyzes the principles and limitations of different methods of model checking  
Through careful analysis, we find that there are two primary problems in the standard startup model when we implement it. One is that the standard startup model in AS6003 is by no means an effort to cover its implementation in detail, but it only gives a high-level description. The other one is that the contention-eliminating strategy mandates the removal of the first valid cold-start frame in all cases, without any provision for detecting contention. This may lead to increased time consumption. The two aforementioned problems have been depicted in Figure 4. Marks 1 through 5 in Figure 4 highlight several crucial details that must be considered in the actual implementation of the model, which are not addressed in the standard startup model. Mark 6 in Figure 4 indicates that the contention-removing mechanism that can be improved is employed in the standard startup model. Node \(i\) and \(j\) in Figure 4 start concurrently. AS6003 supposes that they start to transmit the cold-start frame at the same time. However, in a real physical environment, the concurrent startup does not absolutely simultaneous startup. There may be a time deviation in the startup time of concurrent nodes, as depicted in Mark 2. The standard startup model of AS6003 does not provide a formal expression of this time deviation and does not offer the bound of the deviation time under which the system can start correctly, which is critical for evaluating the correctness of the startup model. Mark 3 and Mark 4 in Figure 4 indicate the time interval between two frames, where Mark 3 sends the nodes and Mark 4 receives the nodes. The determination of these time intervals is essential for analyzing the types of contention scenarios and determining at which specific scenario the first valid cold-start frame can be retained. Mark 5 signifies the time when a receiving node receives a complete cold-start frame, after which it is unclear whether the node can complete synchronization. The standard startup model does not define the necessary actions that a node needs to take if synchronization is not achieved, and no existing studies provide a solution to this issue. The shaded portion denoted as Mark 1 in Figure 4 represents the observation window, which can monitor the activity of the entire channel over a specified time frame. The determination of both the start and end times of this window is essential in actual implementation. However, the standard startup model in AS6003 lacks clarity in this regard. Furthermore, Mark 6 represents the time when the contention-removing mechanism of the startup model discards frames. The startup model prescribed by AS6003 does not include a mechanism to detect contention, but instead mandates the implementation of  
Figure 4: The listed six problems in standard startup model. The black box represents the sending frame, while the gray box represents the receiving frame in this figure. The listed six problems are indicated in red numbers in this figure. a priority back-off strategy to eliminate potential contention. However, the contention removing of the standard startup model only makes sense when the contention has already occurred. In some cases, the system can achieve synchronization without discarding frames, which reduces the startup time. To solve the above problems, this paper gives a detailed and improved startup model with a contention-detection strategy based on the top-level standard AS6003. The proposed startup model is named ATWin because an arrival time window (ATW) is added to detect the contention as each node's local observation window and to determine whether the first cold-start frame should be discarded, thus reducing the startup time caused by the mandatory frame-dropping mechanism in AS6003.