# From Cyber-Physical Convergence to Digital Twins: A Review on Edge Computing Use Case Designs
## 6 The Digital Twin Technology
### The Digital Transformation
#### 6.2.2 End-to-End Wireless Network Digital Twin  
Wireless networks are designed according to the principle of end-to-end architecture in order to guarantee certain application-specific features such as reliability and security [104]. The expectation for 6G networks is that they will be more reliable and fast and be able to support a large number of ultra-low latency devices. For this to be possible, network agility is very key, as network providers will need to look beyond connectivity and complexity but towards new opportunities for growth in order to offer end-to-end solutions for both individual and enterprise consumers [105]. Some identified areas of interest where network DTs have interesting use cases are shown in Figure 4 below. In Figure 4 above, the twins of the different network substrates are shown: (i) the RAN, (ii) the edge network, (iii) the backhaul or transport network, and (iv) the network core. The positioning of the network functions (NFs), i.e., baseband units (BBU), user plane function (UPF), session management function (SMF), and application (App), is only for illustration purposes--it does not depict any form of new radio (NR) functional split. * Cell Site Digital Twin: Since the process of installing, inspecting, and maintaining cellular towers is difficult and costly, the AR functionality can be enabled to visualize the cell tower. There is a plethora of use cases where the cell site DT can support MNOs or tower companies, i.e., (i) rollouts of new generation technology such as 6G, (ii) site survey on existing sites, (iii) upgrades, and (iv) maintenance activities [106]. Based on the assumption of perfect spectrum sensing in dynamic spectrum access (DSA), the information exchange that takes place between SUs and the gNBs is according to peer-to-peer information exchange. 1. Infrastructure Digital Twin: Based on the specified kind of information exchange between the users and the network, the programmability of the network can allow for enhanced data management tasks (load management, compression, and data reduction). A programmable framework for advanced IoT and data-driven automation also allows for virtualized resource provisioning. The most prominent resource provisioning of this kind is known as containerization. Containers are created as images and allow users to package application code, dependencies, and configuration into a single object that can be deployed in any environment. However, they are only considered containers when they are running. 2. Device Digital Twin: On the other hand, information exchange between users is governed by transfer learning and cooperation management, which considers source agent selection and target agent training. Information fidelity technologies such as federated learning and blockchain are incorporated with digital twinning to provide security for targeted services and advanced testing and facilitate deployment. * Edge Site Digital Twin: Due to the use of higher frequencies, which are vulnerable to absorption, 6G networks will be limited in terms of transmission range. This means that edge platforms or sites will be a perfect solution to counteract this limitation, and computational resources will be docked at an aggregation site and launched on-demand to each edge site. However, it must be noted that the DT of the edge site includes both the access network and the backhaul network (transport). In order to meet the high computing demand of edge computing networks, new enabling technologies such as (i) the air interface and the transmission technologies as well as the novel network architecture, (ii) advanced multi-antenna technologies, (iii) network  
Figure 4: The different areas of interest and interesting use cases for digital twins in wireless networks. slicing, (iv) cell-free architecture, and (v) cloud/fog/edge computing are already being developed [107].