# 6G Cognitive Information Theory: A Mailbox Perspective
## 4 Distributed Intelligent Network
### Fusion of Terminal Caching, Communication and Computing  
The fusion of terminal caching, communication, and computing is also known as terminal 3C fusion. This means that data fusion and analysis are conducted on caching, communication, and computing resources on the user side (sensors and devices), which provides the best resource-allocation scheme to achieve the optimal network experience to users. Since the terminal devices are dispersed, two scenarios (i.e., single end-user and multiple end-users) are considered, and either a distributed or centralized 3C fusion model is established when the data transmission or network communication is conducted. _(1) 3C fusion for a single terminal_. In 3C fusion for a single user device, computing tasks or services are targeted. First, a task that a user is executing is described at the current moment, and then 3C resource modeling is optimized based on the task data. For intelligent services, the key performance indicators include channel capacity, transmission delay, transmission reliability, number of connected devices, and the cost-effectiveness of the transmission. The user's service quality refers to the user's satisfaction with a certain service. However, the satisfaction level depends on the user's expectation of the service, which is related to the user's personal preferences, environment, and data related to the task. Specifically, the 3C fusion process for a single terminal can be divided into the following steps: (1) User experience and service modeling. The modeling function between the user's experience (quality of service) and services provided by the edge-cloud server is a non-linear function, which can be modeled by a neural network. (2) Service and 3C fusion modeling: The demand for a service (i.e., requirements of computing tasks on caching, computing, and communication resources) can be described as a relation function between the service and amount of computation, transmission, and caching. At this point, the relationship between each of the key performance indicators of a task (such as transmission  
Figure 4: Wireless-communication enabling technology, transmission fusion, and optimization process. delay) and 3C can be obtained. (3) Optimal 3C fusion and configuration: The configuration problems of terminal 3C resources, computing, storage, and communication resources are allocated to the terminal to make the service quality at the terminal as high as possible. To achieve this goal, a mathematical description of the terminal performance (e.g., communication capacity, computing capacity, storage capacity, service demand, dump energy, and user data) should be determined first. In practice, due to the wide time variability and complexity in the service demand, link state, channel capacity, equipment load, and other parameters of a terminal, an on-line dynamic adaptive algorithm can be adopted in the mobile terminals to realize real-time configuration of caching, communication, and computing resources. Specifically, the goal of optimal 3C fusion and configurations is to minimize the task delay. The constraint is that the energy consumed by a terminal should not exceed the battery capacity, caching should not exceed the caching capacity, and the computing capacity should not exceed the remaining maximum amount of computing. To ensure the user experience in the process of iterative optimization, the pre-computing mechanism can be used; the requirements of a task and ability of network node for 3C resources at the next time can be predicted according to the status of the terminal equipment at the current time, and then the preliminary matching can be performed. (4) 3C offloading at a single terminal. When a terminal fails to meet the requirements of a task, a collaboration between the fusion of 3C terminal resources and edge cloud should be considered, i.e., the terminal meets the requirements through the transformation of caching, communication, and computing resources.