## 2 The Evolution and Trends of 6G Network Architecture
### Opportunities for Fundamental Change
#### 2.2.5 Human-Centric Networks  
The telecommunications ecosystem has progressed from an initial cell-centric architecture in 2G and 3G, where designs were influenced by cell coverage and base station placements. In contrast, the current device-centric architecture of 4G and 5G is driven by capacity, directly correlated with the number of high-quality links perceived by terminals like smartphones or fixed wireless access modems. High-quality links refer to communication links between devices and the network infrastructure that exhibit strong signal strength, minimal interference, high data rates, low latency, and reliable stability, ensuring seamless performance. However, these designs are static and don't effectively address important societal use cases, where multiple users' user equipment (UE) simultaneously share radio resources with distinct KPIs and quality of service (QoS) requirements. Notably, 6G presents an opportunity to adopt a human-centric approach, characterized by societal awareness and technological adaptability. This would enable more efficient and effective responses to significant societal needs or unforeseen events (Black Swan events). This change is essential because the networking infrastructures in place now are too diverse and fragmented to effectively address societal issues. Adopting an Internet-centric approach, where endpoints connect through any operator, can lead to significant latency due to the extensive fiber networks involved. Signals may need to travel through multiple operators' backhaul networks, increasing the fiber distance by 600-1000 km, which adds 3-6 ms of latency in an uncongested network. In congested networks without a sliced architecture, delays can be even greater. Consequently, in multi-operator environments, 5G struggles to provide the ultra-low latency QoS expected for flexible deployments across different operators. The solution lies in minimizing or eliminating the transport network fiber infrastructure to reduce latency. However, realizing this objective necessitates the broader adaptation or \"sliceability\" of Internet Service Provider (ISP) infrastructure. In 6G, a comprehensive end-to-end orchestration strategy is crucial to enable such a deployment scenario. This orchestrator might be feasibly deployed on a distributed ledger to improve transparency among competing entities, as depicted in Figure 2. Apart from the user and control planes, the AI-Plane (A-Plane) is added. Networking, storage, and computation have all become more simplified. The network of transportation is condensed. Moreover, cloud-centric lambda functions are progressively disaggregating the 3 GPP logical network elements. Figure 2 presents the key components of the 6G network architecture, which include several functions such as user equipment (UE), radio access network (RAN), Slice Management Function (SMF), and others like Network Slice Subnet Management Function (NSSMF), Network Slice Selection Function (NSSF), and Network Exposure Function (NEF), among others. These abbreviations are described below. UE (user equipment): This refers to the devices used by end users to access the network, such as smartphones, tablets, or Internet of Things (IoT) devices. UE acts as the interface between the user and the network, facilitating data transmission. RAN (radio access network): This represents the network segment that connects the user equipment (UE) to the core network via radio communication, including base stations and cell towers that enable wireless connectivity. SMF (Session Management Function): This function is responsible for handling session management tasks in the network, such as maintaining the session state, controlling QoS, and managing IP address allocation for user sessions. NSSMF (Network Slice Subnet Management Function): This function manages the resources and operations of a network slice subnet, which is part of a larger 5G or 6G network slice, ensuring that specific service requirements are met within the slice.