As of today, the fifth generation (5G) mobile communication system has been rolled out in many countries and the number of 5G subscribers already reaches a very large scale. It is time for academia and industry to shift their attention towards the next generation. At this crossroad, an overview of the current state of the art and a vision of future communications are definitely of interest. This article thus aims to provide a comprehensive survey to draw a picture of the sixth generation (6G) system in terms of drivers, use cases, usage scenarios, requirements, key performance indicators (KPIs), architecture, and enabling technologies. First, we attempt to answer the question of "Is there any need for 6G?" by shedding light on its key driving factors, in which we predict the explosive growth of mobile traffic until 2030, and envision potential use cases and usage scenarios. Second, the technical requirements of 6G are discussed and compared with those of 5G with respect to a set of KPIs in a quantitative manner. Third, the state-of-the-art 6G research efforts and activities from representative institutions and countries are summarized, and a tentative roadmap of definition, specification, standardization, and regulation is projected. Then, we identify a dozen of potential technologies and introduce their principles, advantages, challenges, and open research issues. Finally, the conclusions are drawn to paint a picture of "What 6G may look like?". This survey is intended to serve as an enlightening guideline to spur interests and further investigations for subsequent research and development of 6G communications systems.

The Road Towards 6G: A Comprehensive Survey

As of today, the fifth generation (5G) mobile communication system has been rolled out in many countries and the number of 5G subscribers already reaches a very large scale It is time for academia and industry to shift their attention towards the next generation At this crossroad, an overview of the current state of the art and a vision of future communications are definitely of interest This article thus aims to provide a comprehensive survey to draw a picture of the sixth generation (6G) system in terms of drivers, use cases, usage scenarios, requirements, key performance indicators (KPIs), architecture, and enabling technologies First, we attempt to answer the question of “Is there any need for 6G?” by shedding light on its key driving factors, in which we predict the explosive growth of mobile traffic until 2030, and envision potential use cases and usage scenarios Second, the technical requirements of 6G are discussed and compared with those of 5G with respect to a set of KPIs in a quantitative manner Third, the state-of-the-art 6G research efforts and activities from representative institutions and countries are summarized, and a tentative roadmap of definition, specification, standardization, and regulation is projected Then, we identify a dozen of potential technologies and introduce their principles, advantages, challenges, and open research issues Finally, the conclusions are drawn to paint a picture of “What 6G may look like?” This survey is intended to serve as an enlightening guideline to spur interests and further investigations for subsequent research and development of 6G communications systems

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This article aims to provide a comprehensive overview for key issues in broadband LEO satellite communication systems. First of all, the network architecture is introduced, which is the basis of the whole system. The space-based LEO system with ISL, which requires a small number of ground gateways, is the focus. In this system, the satellite constellation design is important with impact on key system performances such as coverage. Two popular LEO constellations, the walker Delta and Star constellations, are introduced. Given satellite constellations, proper beam coverage schemes should be employed at satellites to provide seamless coverage all over the world. A hybrid wide and spot beam coverage scheme is presented, where the LEO provides a wide beam for large area coverage and several steering spot beams for highspeed data access. Moreover, special coverage schemes should be designed in broadband LEO systems for the interference coordination between LEO and GEO. To protect GEO communications, LEO satellites should be turned off if they cause interference to GEO. In this case, to provide services for users covered by the turned-off LEO satellites, a progressive pitch method and a coverage expanding method can be employed. Finally, the coverage performance of LEO is also closely related to resource management schemes. The global resource management for broadband LEO systems is complicated, involving a large amount of data, and a two-level management structure should be employed. Using this structure, an NMC with powerful storage and processing capabilities is employed to carry out the first-level management, making strategies based on all information collected from the whole system. Then satellite base stations with limited capabilities are employed to respond to the strategies generated by NMC in real time.

Broadband LEO Satellite Communications: Architectures and Key Technologies

Digital Soviet Union : the Russian national segment of the Internet as a closed national network shaped by strategic cultural ideas

With a ten-year horizon from concept to reality, it is time now to start thinking about what will the sixth-generation (6G) mobile communications be on the eve of the fifth-generation (5G) deployment. To pave the way for the development of 6G and beyond, we provide 6G visions in this paper. We first introduce the state-of-the-art technologies in 5G and indicate the necessity to study 6G. By taking the current and emerging development of wireless communications into consideration, we envision 6G to include three major aspects, namely, mobile ultra-broadband, super Internet-of-Things (IoT), and artificial intelligence (AI). Then, we review key technologies to realize each aspect. In particular, teraherz (THz) communications can be used to support mobile ultra-broadband, symbiotic radio and satellite-assisted communications can be used to achieve super IoT, and machine learning techniques are promising candidates for AI. For each technology, we provide the basic principle, key challenges, and state-of-the-art approaches and solutions.

6G Visions: Mobile ultra-broadband, super internet-of-things, and artificial intelligence

Internet of Things (IoT) is one of the evolutionary directions of the Internet. This paper focuses on the low earth orbit (LEO) satellite constellation-based IoT services for their irreplaceable functions. In many cases, IoT devices are distributed in remote areas (e.g., desert, ocean, and forest) in some special applications, they are placed in some extreme topography, where are unable to have direct terrestrial network accesses and can only be covered by satellite. Comparing with the traditional geostationary earth orbit (GEO) systems, LEO satellite constellation has the advantages of low propagation delay, small propagation loss and global coverage. Furthermore, revision of existing IoT protocol are necessary to enhance the compatibility of the LEO satellite constellation-based IoT with terrestrial IoT systems. In this paper, we provide an overview of the architecture of the LEO satellite constellation-based IoT including the following topics: LEO satellite constellation structure, efficient spectrum allocation, heterogeneous networks compatibility, and access and routing protocols.

LEO Satellite Constellation for Internet of Things

Network virtualization (NV) is considered as an enabling tool to remove the gradual ossification of current Internet. In the network virtualization environment, a set of heterogeneous virtual networks (VNs), isolated from each other, share the underlying resources of one or multiple substrate networks (SNs) according to the resource allocation strategy. This kind of resource allocation strategy is commonly known as so called Virtual Network Embedding (VNE) algorithm in network virtualization. Owing to the common sense that VNE problem is NP-hard in nature, most of VNE algorithms proposed in the literature are heuristic. This paper surveys and analyzes a number of representative heuristic solutions in the literature. Apart from the analysis of representative heuristic solutions, a taxonomy of the heuristic solutions is also presented in the form of table. Future research directions of VNE, especially for the heuristics, are emphasized and highlighted at the end of this survey.

Heuristic solutions of virtual network embedding: A survey

Space information network (SIN) plays an extremely important role in civil and military applications. However, a specific definition of SIN still remains a challenging issue. Unlike space communication network (SCN), which merely focuses on information delivery, SIN has the ability to process the delivered information and providing corresponding services based on the information, which makes SIN seem to be able to understand information. This paper offers architecture and corresponding network model for time-space uninterrupted SIN. Initially, both physical and logical constitution of SIN architecture are presented with several corresponding constellation designs, which is the fundamental work for setting nodes in SIN. Based on this SIN architecture, a hierarchical autonomous system (AS)-based network model for SIN is proposed in order to manage SIN more efficiently by separating the whole network into several relatively stable ASs. Furthermore, we analyze topology control schemes and network capacity trend of AS-model based SIN. This paper gives the future research directions in the conclusion.

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Architecture and Network Model of Time-Space Uninterrupted Space Information Network

Network virtualization (NV) has been accepted as the integral paradigm of next generation network (e.g., 5G virtualized network) since its inception. Virtual network embedding (VNE) is the resource optimization problem for NV. Over the past decade, multiple VNE algorithms have been proposed. However, prior VNE algorithms focus on embedding more proposed virtual networks (VNs) onto the shared substrate networks (SNs) so as to maximize embedding revenues of internet service providers (ISPs), managing and operating the shared SNs. Due to the fact that energy cost is approaching more than half of the operating cost of shared SNs, it is crucial for ISPs to minimize total VN energy cost so as to maximize the net profit. To deal with this issue, a formal VNE problem model and VNE energy cost model are first proposed. Then, a novel node ranking approach is proposed, jointly quantifying the multiple energy and revenue related topological attributes. The novel node ranking approach is able to compute stable node embedding ability. Next, an energy efficient heuristic algorithm ( ER-VNE ) is detailed. Numerical simulations are made to validate that the ER-VNE can significantly reduce the energy cost by approximately 16% over the typical energy-related algorithm while embedding the same amount of VNs successfully.

ER-VNE : A Joint Energy and Revenue Embedding Algorithm for Embedding Virtual Networks

Virtual network embedding (VNE) refers to the resource allocation problem for network virtualization. Since its inception, multiple mapping algorithms have been proposed for embedding virtual networks (VNs) effectively and efficiently. However, prior mapping algorithms mostly complete the VN embedding in two separated stages: first node embedding and subsequent link embedding. Certain mapping algorithms embed the VN in one stage by using mixed integer linear programming method or subgraph isomorphism approach, involving high embedding completion time. Meanwhile, prior researchers conduct the VN embedding, on the basis of one underlying substrate network (SN). While in future VNE application, each VN must be mapped among multiple geographically distributed SNs. On above backgrounds, we propose a location aware and node ranking value driven embedding algorithm, labeled as LANRVD. The LANRVD enables to conduct the embedding in two coordinated embedding stages within polynomial time. In addition, the LANRVD embeds the VN among multiple geographically distributed SNs. Numerical results reveal that the LANRVD significantly improves VN acceptance ratio by 10&#x0025; over existing typical two-separated-stages algorithms.

Zhicheng Qu

Papers

LEO Satellite Constellation for Internet of Things

Heuristic solutions of virtual network embedding: A survey

Architecture and Network Model of Time-Space Uninterrupted Space Information Network

ER-VNE : A Joint Energy and Revenue Embedding Algorithm for Embedding Virtual Networks

Location Aware and Node Ranking Value Driven Embedding Algorithm for Multiple Substrate Networks