## 2 System Model
### System Overview and Assumptions  
The TSN model developed and analyzed in this study operates under several foundational assumptions to ensure a well-defined framework for scheduling:  
* Known Network Topology: The physical and logical topology of the in-vehicle network, including the interconnection of TSN switches and end-stations, as well as critical parameters like the bandwidth of each communication link, is considered known and defined prior to the scheduling process. Furthermore, this network topology is assumed to remain static after the Gate Control Lists (GCLs) are computed and deployed, meaning no dynamic changes to links or devices are considered during the operational phase governed by a specific GCL.
* Defined Data Stream Attributes: All relevant attributes of the data streams requiring deterministic transmission are known in advance. These attributes are crucial for scheduling and include, but are not limited to, the cycle period at which each stream is generated, its assigned Priority Code Point (PCP) value (which maps to a specific queue), and the length (in bytes or transmission time at a given link speed) of its data frames or packets.
* Centralized Network Configuration Paradigm: The network model adheres to the fully centralized configuration paradigm, as outlined in the IEEE 802.1 Qcc standard for TSN. In this model, a Centralized Network Configuration (CNC) entity has a global view of the network and is responsible for all aspects of network configuration, including the collection of stream requirements, computation of schedules (GCLs), and their distribution to the relevant TSN switches.
* Predictable Interferences and Underlying Fault Tolerance: While real-world networks are subject to various interferences, it is assumed for the scheduling model that either such interferences are predictable and accounted for, or that underlying fault tolerance mechanisms (e.g., frame replication and elimination for reliability as per IEEE 802.1 CB [26], not explicitly modeled here but assumed to be complementary) manage transient errors or link failures. The scheduling algorithm itself focuses on conflict-free transmission paths under normal operating conditions.
* Sufficient Buffer Capacity: It is assumed that the memory buffers within the TSN switches are sufficiently sized to handle the transient storage of frames. The primary goal of the offline GCL scheduling is to prevent the formation of persistent queues by ensuring that frames are forwarded shortly after their arrival, thereby precluding the possibility of buffer overflow under normal, scheduled operation.
* Sub-flow Capability (for Baseline Algorithm): The baseline scheduling algorithm incorporates a sub-flow division mechanism. Therefore, TSN transceivers (end-stations) are assumed to be capable of segmenting original data streams into smaller sub-flows before transmission and reassembling these sub-flows at the receiving end-station. This segmentation and reassembly process is assumed to be transparent and not compromise the integrity or informational content of the original data stream.
* Fine-grained Time Slotting (for Acceleration Algorithm): The scheduling computation acceleration algorithm, introduced later as an optimization, conceptualizes the scheduling hyperperiod as being divisible into fine-grained discrete time slots (e.g., 1 us). It is assumed that the TSN switches support GCL operations with a temporal granularity compatible with this slot size.