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Robust WIrelesS Caching for Mobile NEtworks (RISE)

Periodic Reporting for period 1 - RISE (Robust WIrelesS Caching for Mobile NEtworks (RISE))

Reporting period: 2018-09-01 to 2020-08-31

With the development of smart terminals and emerging new applications (high-resolution multimedia, social networks, big data analysis etc), current mobile infrastructure (the 3G or 4G mobile networks) cannot gradually meet fast-increasing user requirements. Thus, radical and new technologies are needed for wireless communications, in addition to other candidate technologies, e.g. massive MIMO, wireless caching, etc. Among them, wireless caching increases the system performance with a new strategy. The main idea of wireless caching is to pre-store popular user data near end terminals, e.g. at base stations or the storage memory of user terminals. Thus, the request can be satisfied locally, rather than from remote servers. Then, the network throughput is improved and the response latency is reduced, especially for the multimedia transmission, which will be the dominant application in the 5G mobile.
However, the applications of wireless caching to mobile networks still face many challenges, e.g. impacts of user mobility, reliable transmission in multiple users/nodes, unreliable channels and information security. For instance, since the terminal is moving (as mobiles), the users may have to retrieve data from multiple nodes. Thus, the optimal caching for one node may not be optimal for another node in terms of rates. Moreover, the users may by multiple-accessed by non-orthogonal signals. This will lead to catastrophe. Meanwhile, the transmission medium of wireless communications is time-variant fading channels, which affect download bandwidth and capacity. Also, wireless transmission is unreliable, and efficient error control methods should be taken to fight against transmission errors. The mobility results in uncertainty, and the random in/out network and locations changes of mobile nodes may be frequent and lead to the uncertainty for downloading requested files. The variances of network topology, especially with mmWave communication, cooperative relaying and the integration of heterogeneous networks etc., render the structure of network topology complex. Because of the open air transmission and distributed caching, the security of caching data is also an important problem.
From an overview aspect, we studied information-theoretical performance limits and coding schemes to improve transmission rates, the reliability of transmission, and security. Except the theoretical analysis, we implemented our results in simulation testbed.
The overview of main results achieved can be summarized as follows:
(1). We investigate the ergodic rate and average service delay for typical user terminal (UT) in the clustered cacheenabled small cell networks (SCN) and ultra dense networks (UDN) with mmWave channels.
(2)We focus on a downlink multicarrier (MC) NOMA network, where a single base station serves a set of users through multiple subchannels. A novel greedy subcarrier assignment scheme based on the worst-user first principle is proposed.
(3)We review the various application scenarios, fundamental performance limits, and potential technical solutions for high-reliability and lowlatency (HRLL) wireless IoT networks.
(4)A general framework for enhancing the physical layer security (PLS) in the Internet of Things (IoT) systems via channel feedback is established.
(5)We studies how to enhance the already existing secrecy rate region of the BC-MSR-R via receivers’ feedback. Specifically, we propose two feedback strategies for the BC-MSR-R, where one uses the feedback to generate pure secret keys protecting the transmitted messages, and the other uses the feedback to generate not only keys but also cooperative messages helping the receivers to improve their decoding performance.
(6)We study a mobility prediction based proactive wireless caching scheme for two-tier cellular networks consisting of a base station (BS) tier and a device-to-device (D2D) tier. Two scenarios are considered: popular contents cached only at BSs, and popular contents cached at both BSs and MTs. Then we analyse the hit-rate performance to evaluate the presented schemes.
(7)We propose an indoor lightwave downlink wireless communication network with the non-orthogonal multiple access (NOMA) technology, that consists of one visible light communication (VLC) access point (AP) and a pair of randomly located users.
(8)We investigate the communication efficiency and running time of ADMM in solving the consensus optimization problem over decentralized networks. We propose the parallel random walk ADMM (PW-ADMM) algorithm, where multiple random walks are active at the same time.
The dissemination tasks aim at achieving the broadest audience and the highest impact of the scientific results in the research community and industry. One of the most important dissemination channels is the scientific community, which has been achieved through the publication of our contributions in high-impact journals in the area of information theory, coding theory, and wireless networking. The project has published 7 papers in prestigious journals including IEEE Transactions (for a specialized audience). On the other hand, considering timely dissemination through scientific and technical presentations to international conferences and workshops, a conference paper has also be published for the project.
This project has communicated to expert audience, general audience and public. For expert audience, in addition to publications in journals and conferences, we organized special seminars and lectures twice (one was in Linköping University and one was in KTH) in the research area of this project, with speakers selected from collaboration networks and scientific society. In order to increase the visibility of the project, the fellow and the supervisor jointly edited IEEE Internet of Things Journal Special Issue on Low-latency High-reliability Communications for IoT. In this special issue, we invited Dr.Yue Xiao from University of Electronic Science and Technology of China, Dr. Zhibo Pang from ABB Research, Dr. Branka Vucetic from University of Sydney and Dr. H. Vincent Poor from Princeton University as co-editors. Thus the visibility has been increased not only from the academic aspect, but also the industrial. Meaning while, the international collaborative network has been extended and strengthened. For a more general audience, we also has published two survey papers on IEEE VT Magazine and IEEE JIOT. Our testbed ran open to general public on lab-open days to help freshmen and publics better understand this promising technology. A project webpage has been established according to the latest progress.

This fellowship also leads to opportunities to develop other research projects from Sweden and China research councils, e.g. in 2020, the coordinator Dr. Ming Xiao obtained a joint STINT (Sweden)-NSFC (China) project with a Chinese partner from Southwest Jiaotong University where the fellow was original from. This is important for Sweden and China research community, because China and Sweden are the very advanced in communication technology, and China is fast developing and also the biggest market. Thus, the success of the project benefited European research community, and European education to increase the reputation and markets in China (as the largest market in the world). Thus, eventually, the fellowship actually bring substantial added values for both sides.