WLAN mesh networks are one of the key technologies for upcoming smart city applications and are characterized by a flexible and low-cost deployment. The standard amendment IEEE 802.11s introduces low-level mesh interoperability at the WLAN MAC layer. However, scalability limitations imposed by management traffic overhead, routing delays, medium contention, and interference are common issues in wireless mesh networks and also apply to IEEE 802.11s networks. Possible solutions proposed in the literature recommend a divide-and-conquer scheme that partitions the network into clusters and forms smaller collision and broadcast domains by assigning orthogonal channels. We present CHaChA (Clustering Heuristic and Channel Assignment), a distributed cross-layer approach for cluster formation and channel assignment that directly integrates the default IEEE 802.11s mesh protocol information and operating modes, retaining unrestricted compliance to the WLAN standard. Our concept proposes further mechanisms for dynamic cluster adaptation, including subsequent cluster joining, isolation and fault detection, and node roaming for cluster balancing. The practical performance of CHaChA is demonstrated in a real-world 802.11s testbed. We first investigate clustering reproducibility, duration, and communication overhead in static network scenarios of different sizes. We then validate our concepts for dynamic cluster adaptation, considering topology changes that are likely to occur during long-term network operation and maintenance.

Since the first plasma operation in 2015, the superconducting fusion experiment Wendelstein 7-X has successfully completed 4 experiment campaigns (OP1.1, OP1.2a, OP1.2b, and OP2.1). The machine maintenance phase was completed at the end of January 2024, followed by the commissioning of W7-X. The start of the scientific plasma operation phase OP2.2 is planned for September 2024. The Trigger Time Event (TTE) system is used by the central control systems, the technical components and the diagnostics of W7-X for their time synchronization, for processing events, and for generating and receiving trigger signals. This use cases makes it necessary to adapt the TTE system to the changing requirements of users. After an introduction to the functions and structure of the TTE system, this contribution describes the current expansion status of the TTE system and the planned modifications and expansion of the hardware and software of the TTE system. Finally, the current status of the planned work on the TTE system for the upcoming W7-X operational phase OP2.2 is presented. The contribution ends with a summary.