# 6G Cognitive Information Theory: A Mailbox Perspective
###### Abstract
Therefore, in a 6G network, it is necessary to realize an initial interaction of information [8]. Namely, in a 6G communication system, intelligent devices should cognize a user's demands using AI algorithms and collect valuable information of the user, and finally realize initial interaction with the user. Thus, the future network will have the following features: (i) customized services: demands on network resources can be customized based on the needs of an intelligent service; (ii) value transmission: the future network is capable of realizing the transition from content transmission to value transmission; (iii) proactive interaction: the network system in the future will analyze human needs and interact with humans proactively and, thus, transmit both information and value while interacting. However, the question is how to realize transmission and interaction of information value. The transmission of information can be realized based on the traditional Shannon information theory, i.e., the original information is transmitted after being coded, and it is decoded into the original information after being transmitted. Next, the question of how to realize the transmission of information value arises. Thus, it is necessary to measure information value. To address these challenges, in this paper we propose the 6G MailBox Theory, namely, a cognitive information carrier to enable distributed algorithm embedding for intelligent networking, as shown in Figure 1. There are some variations that include the word \"cognitive information\" and/or the word \"mailbox\". Therefore, Cognitive Information Theory and Mailbox Theory are widely accepted too. Compared with the traditional mailbox, our proposed mailbox is an intelligent agent carrying information. Using mailbox theory, a smaller amount of data is required for transmission and higher reliability of decision-making can be achieved. Thus, with the information cognition based on the mailbox theory, the network will not only overcome the time and space constraints for information transmission in a traditional network, but will also realize the optimal joint decision-making. In summary, the contributions of this paper are included as follows:  
* 6G _Network Architecture_: In order to meet the requirements of intelligence, customization, and value transmission of a 6G network, a new type of network integrating distributed intelligent network, active interactive network, and cognitive information transmission have been proposed. The distributed intelligent network, proactive interaction network, and cognitive information transmission are introduced in detail. * 6G _Mailbox Theory_: We propose the 6G mailbox theory and introduce its features, including polarity, traceability, dynamics, convergence, figurability, and dependence. Furthermore, the key technologies in realizing 6G mailbox theory are introduced, including extraction of information value based on knowledge graph, information cognition based on embedding distribution learning and blockchain-based safe transmission of cognitive information. * _Performance Evaluation_: In order to verify the proposed 6G mailbox theory, we establish a cognitive communication system assisted by deep learning, and the information is cognized and encoded by it with deep learning. The experimental results show that, compared with encoding of a traditional communication system, less data can be transmitted with the proposed cognitive communication system, while the transmission error is relatively small. Driven by the three design issues of 6G cognitive information theory, the following sections are associated with three contributions of this article and are organized as Figure 2. Sections 2 and 3 summarize the evolution of 5G and 6G networking. On this basis, Sections 4 and 5 propose an integration network architecture of distributed intelligent, active interact, and cognitive information transmission. Based on the new designed 6G network architecture, we introduced our novel 6G MailBox theory.