# Metaverse Meets Smart Cities--Applications, Benefits, and Challenges
## 2 Metaverse Technology Stack  
The metaverse requires various technical components to operate. These can be described in different models. The term technology stack combines computer science and software development terms to describe a collection of technologies, frameworks, and tools [20]. It shows which components are necessary and how they work together to create a specific application or platform. In the context of the metaverse, the technology stack refers to the various technologies used to support the virtual ecosystem of the metaverse and enable the activities within it [21]. In this study, we mainly build on a technology stack introduced by [PERSON] et al. [1], with additions based on an article by [PERSON] [22]. Our depiction of the relevant layers is presented in Figure 1.  
The individual components of the stack are explained below:  
* Infrastructure and Hardware: The metaverse's infrastructure and hardware comprise the physical layer required to operate and interact with virtual worlds. This includes powerful servers, network connections, and specialized technology, such as high-performance computing cores like Graphics processing units (GPUs) or Tensor processing units (TPUs). to enable reliable and low-latency experiences [19].
* Network and Communication: Networks and reliable data protocols that enable high data quality are required to provide enormous amounts of data with low latency. Wireless networks play a vital role here, as they significantly increase the quality of experience (QoE) compared to wired networks due to freedom of movement and availability. In addition to the data rate and throughput, the networks' scalability plays a key role in enabling low latency [8].  
Figure 1: Metaverse technology stack layer (own presentation based on the contents of [1; 22]).  
* Cloud Computing and Distributed Ledger Technology: Distributed Ledger Technology (DLT) in the metaverse refers to technologies such as blockchain that enable decentralized data management. DLT secures digital assets, authenticates users, and creates a trusted environment for transactions within the metaverse [22].
* AI, Machine Learning, and IoT: Artificial intelligence and machine learning are crucial elements in the metaverse, as they enable dynamic and interactive design of the virtual worlds. AI enables personalized experiences, intelligent avatars, and non-player characters (NPCs) with real-time translation over natural language processing (NLP), and it adapts the virtual environment to user behavior. However, the provision of real-time data via efficient IoT sensors also enhances a feeling of immersion by creating real-life conditions [1].
* User Interactivity and Extended Reality: People can use different types of interfaces to interact with the metaverse environment. These include intuitive input devices such as hand and gesture recognition, data glasses for immersion in virtual worlds, and spatial computing applications that enable people to move freely in the virtual world and interact with digital objects [23].
* To demonstrate the interaction of the individual layers and the need for interaction, an example application from the smart city context is explained: various technologies from the metaverse stack are required to provide a metaverse citizen platform for digital events. The infrastructure and hardware include potent servers, GPUs, and TPUs to ensure a smooth experience at digital events. Wireless networks enable improved freedom of movement and availability for participants, while cloud computing and distributed ledger technology ensure the security of digital assets and transactions. AI and machine learning provide personalized experiences and interactive virtual environments, while IoT sensors provide real-time data to enhance immersion. Intuitive input devices and augmented reality options allow users to interact freely in the virtual world and experience digital events in an immersive way.