Haotong Cao

Bio: Haotong Cao is an academic researcher from Nanjing University of Posts and Telecommunications. The author has contributed to research in topics: Computer science & Network virtualization. The author has an hindex of 16, co-authored 90 publications receiving 905 citations. Previous affiliations of Haotong Cao include Nanjing University & Hong Kong Polytechnic University.

LEO Satellite Constellation for Internet of Things

Abstract: 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.

Novel Node-Ranking Approach and Multiple Topology Attributes-Based Embedding Algorithm for Single-Domain Virtual Network Embedding

Abstract: Network virtualization (NV) is a promising approach to remove the ossification of current Internet. Virtual network embedding (VNE) is the key issue in NV which efficiently and effectively maps various of virtual networks (VNs), with different node and link resource requests, onto the shared substrate network(s) with finite underlying resources. Previous VNE algorithms in the literature are mostly heuristic. Single network topology attribute and each node’s local resources are assisted to rank nodes in most heuristic algorithms, leading to inefficient resource utilization of substrate network in the long run. To deal with this issue, we propose the network topology attribute and network resource-considered algorithm (VNE-NTANRC). The VNE-NTANRC algorithm adopts a novel node-ranking approach to rank all substrate and virtual nodes before embedding each given VN. The novel node-ranking approach has two subapproaches and considers five important network topology attributes and global network resources altogether. One subapproach is able to calculate all node values (NoV) directly. The other subapproach, stimulating from the Google PageRank website algorithm, enables to calculate NoVs in a stable state. Simulation results reveal that VNE-NTANRC algorithm outperforms typical and latest heuristic algorithms, only considering single network topology attribute and local resources.

Heuristic solutions of virtual network embedding: A survey

Abstract: 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.

A Novel Optimal Mapping Algorithm With Less Computational Complexity for Virtual Network Embedding

Abstract: Network virtualization (NV) is widely accepted as one enabling technology for future network, which enables multiple virtual networks (VNs) with different paradigms and protocols to coexist on the shared substrate network (SN). One key challenge in NV is VN embedding (VNE), which maps a VN onto the shared SN. Since VNE is NP-hard, existing efforts mainly focus on proposing heuristic algorithms that try to achieve feasible VNE in reasonable time, consequently the resulted embedding is not optimal. To tackle this difficulty, we propose a candidate assisted (CAN-A) optimal VNE algorithm with lower computational complexity. The key idea of the CAN-A algorithm lies in constructing the candidate substrate node subset and the candidate substrate path subset before embedding. This reduces the mapping execution time substantially without performance loss. In the following embedding, four types of node and link constraints are considered in the CAN-A algorithm, making it more applicable to realistic networks. Simulation results show that the execution time of CAN-A is hugely cut down compared with pure VNE-MIP algorithm. CAN-A also outperforms the typical heuristic algorithms in terms of other performance indices, such as the average VN request acceptance ratio and the average virtual link propagation delay.

On the Performance of Cell-Free Massive MIMO With Mixed-ADC Under Rician Fading Channels

Abstract: In this letter, we introduce a mixed analog-to-digital converter (ADC) receiver architecture to cell-free massive multi-input multi-output (mMIMO) system under Rician fading channels. In particular, the mixed-ADC architecture permits some of receiver’s antennas to be implemented with economical low-resolution ADCs, while the rests are equipped with high-priced perfect ADCs. Leveraging on the additive quantization noise model (AQNM), a tight approximate uplink spectral efficiency (SE) expression with matched filtering receiver is derived, which provides us with a tool for easily quantifying the impacts of the Rician ${K}$ -factor, the quantization bit of low-resolution ADCs, and the proportion of the perfect ADCs in the mixed-ADC architecture. Numerical observations demonstrate that the mixed-ADC architecture with a small fraction of perfect ADCs has a great potential to boost the SE compared to the case with pure low-resolution ADCs. Moreover, the mixed-ADC architecture is superior to the full perfect ADCs counterpart in terms of energy efficiency (EE).

Table Of Integrals Series And Products

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Non-Orthogonal Multiple Access (NOMA) for cellular future radio access

Abstract: Radio access technologies for cellular mobile communications are typically characterized by multiple access schemes, e.g., frequency division multiple access (FDMA), time division multiple access (TDMA), code division multiple access (CDMA), and OFDMA. In the 4th generation (4G) mobile communication systems such as Long-Term Evolution (LTE) (Au et al., Uplink contention based SCMA for 5G radio access. Globecom Workshops (GC Wkshps), 2014. doi:10.1109/GLOCOMW.2014.7063547) and LTE-Advanced (Baracca et al., IEEE Trans. Commun., 2011. doi:10.1109/TCOMM.2011.121410.090252; Barry et al., Digital Communication, Kluwer, Dordrecht, 2004), standardized by the 3rd Generation Partnership Project (3GPP), orthogonal multiple access based on OFDMA or single carrier (SC)-FDMA is adopted. Orthogonal multiple access was a reasonable choice for achieving good system-level throughput performance with simple single-user detection. However, considering the trend in 5G, achieving significant gains in capacity and system throughput performance is a high priority requirement in view of the recent exponential increase in the volume of mobile traffic. In addition the proposed system should be able to support enhanced delay-sensitive high-volume services such as video streaming and cloud computing. Another high-level target of 5G is reduced cost, higher energy efficiency and robustness against emergencies.

The Road Towards 6G: A Comprehensive Survey

Abstract: 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

Abstract: 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

Broadband LEO Satellite Communications: Architectures and Key Technologies

Abstract: 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.