## 2 Related Work
Implementing GCLs with strict timing constraints reduces the overall solution space, minimizing the bandwidth available for unscheduled traffic and increasing the possibility of mislaying the required determinism for AVB flows. Moreover, such strict timing scheduling methods complicate the GCL synthesis in large-scale use cases. For these reasons, several proposals have been introduced to support soft time traffic, while simultaneously ensuring the QoS requirements for hard real-time flows. [PERSON] et al. [9; 38] proposed a software algorithm based on the greedy randomized adaptive search procedure (GRASP), including the AVB traffic to be scheduled with the TT traffic. The results confirmed that feasible AVB scheduling was performed using the proposed method under a simple use case. However, AVB schedulability cannot be ensured under heavy loading or more complicated networks. [PERSON] et al. [6] proposed combining hard and soft real-time flows simultaneously, leading to reduced computation complexity. The presented approach chooses a proper transmission cycle and scheduling unit to improve the selection process and reduce the higher-priority impact on the lower-priority flows. Others in [7; 39; 40] have introduced formal latency analysis for AVB traffic based on predefined GCLs. However, all the above algorithms were implemented under the assumption of complete isolation between scheduled traffic windows, resulting in less overall solution space. Many scheduling proposals have addressed traffic and window isolations in the GCL design. Here, we discuss studies most related to our work and compare their limitations, as briefly presented in Table 1. [PERSON] et al. [41] presented a scheduling scheme under the assumption that scheduled and unscheduled flows are entirely isolated. Further, the proposed GCL synthesis separates scheduled flows against one another by implementing fully isolated transmission windows and fully synchronized nodes. In [42], [PERSON] et al. used the targeted bounds of end-to-end latencies and the duration of assigned windows for the scheduled traffic to measure the scalability and schedulability of the proposed algorithm. [PERSON] et al. [43] presented relaxed GCL synthesis by allowing scheduled frames to interfere at the same-priority queue. However, the associated queue gates were still in a mutually exclusive fashion. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Reference**} & **Gate Control List** & **Synchronization** & \multicolumn{2}{c}{**Isolation**} & \multirow{2}{*}{
\begin{tabular}{c} **Relative Offsets** \\ **between Nodes** \\ \end{tabular} } & \multirow{2}{*}{**Key Achievement**} \\  & **(GCL) Design** & & & & & \\ \hline
[42] & Off-line & All nodes & Isolated & Isolated & Not considered &
\begin{tabular}{c} Deriving scheduling \\ constraints \\ \end{tabular} \\ \hline
[43] & Off-line & All nodes & Isolated & Isolated & Not considered &
\begin{tabular}{c} Improved scheduling \\ constraints \\ \end{tabular} \\ \hline
[44] & Off-line & All nodes & Interfered & Isolated & Not considered &
\begin{tabular}{c} Improved scheduling \\ constraints \\ \end{tabular} \\ \hline
[10; 45] & Off-line & All switches & Isolated & Isolated & Not considered &
\begin{tabular}{c} More relaxed \\ schedules \\ \end{tabular} \\ \hline
[11] & Off-line & All switches & Isolated & \
\begin{tabular}{c} Overlapped \\ without \\ optimization \\ \end{tabular} & Not considered &
\begin{tabular}{c} Improved solution \\ space \\ \end{tabular} \\ \hline
[12] & Off-line & All switches & Isolated & \
\begin{tabular}{c} Overlapped \\ without \\ optimization \\ \end{tabular} & Not considered &
\begin{tabular}{c} Preemption \\ improvements \\ \end{tabular} \\ \hline
[13] & Off-line & All switches & Isolated & Isolated & Considered &
\begin{tabular}{c} Less pessimistic \\ latencies \\ \end{tabular} \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Design-based differentiation between relevant studies with associated achievements.