Terrestrial Mobile Networks Research Articles

Interference mitigation method for LEO satellites with optimal dynamic switching array elements in co‐frequency beams

AbstractSatellite communication has rapidly advanced, from navigation to broadband Internet and direct mobile connectivity. Driven by low Earth orbit satellites, these networks are merging with terrestrial mobile networks, forming integrated space–air–ground systems. However, the growing scale of satellite constellations has intensified intra‐system interference, particularly among ground cells utilizing co‐frequency beams. A mitigation method based on switching array elements is proposed, optimizing their state by considering beamwidth and maximum sidelobe level. Simulations show that the proposed algorithm effectively reduces beam coverage widening and sidelobes, mitigating the interference between co‐frequency beams.

Delanalty Minimization With Reinforcement Learning in UAV-Aided Mobile Network

Unmanned aerial vehicle (UAV)-assisted mobile communication has been studied in recent years. UAVs can be used as aerial base stations (BSs) to improve the performance of terrestrial mobile network. In this article, mobile data offloading with UAV trajectory optimization is investigated. To tackle with the delay of requesting data and the immediacy of requested data at the same time, a new metric named delanalty is newly proposed. The delanalty metric jointly considers the delay of user requesting data, the immediacy of requested data file, and the quantity of residual requesting data. A find max delanalty user mechanism is proposed to eliminate the user who has the largest delay time. Furthermore, an actor–critic (AC)-based deep reinforcement learning (DRL) algorithm called AC -based delanalty trajectory optimization (ACDTO) algorithm is proposed to solve UAV’s trajectory optimization problem. Simulation results show that the proposed ACDTO algorithm can find an optimal flight trajectory with minimal delanalty for all users.

HAPS Cell Design Method for Coverage Extension Considering Coexistence on Terrestrial Mobile Networks

HAPS Cell Design Method for Coverage Extension Considering Coexistence on Terrestrial Mobile Networks

Toward Integration of 6G-NTN to Terrestrial Mobile Networks: Research and Standardization Aspects

Toward Integration of 6G-NTN to Terrestrial Mobile Networks: Research and Standardization Aspects

Agile gravitational search algorithm for cyber-physical path-loss modelling in 5G connected autonomous vehicular network

Agile gravitational search algorithm for cyber-physical path-loss modelling in 5G connected autonomous vehicular network

Innovative Trends in the 6G Era: A Comprehensive Survey of Architecture, Applications, Technologies, and Challenges

While the fifth-generation mobile network is being commercialized worldwide, researchers have recently started looking towards the next generation, called the 6G network. Unlike 5G and previous generations of wireless technologies designed to improve network performance for greater bandwidth, lower latency and greater reliability, 6G ecosystems is considered a platform conducive to innovations in the fields of computing, artificial intelligence, connectivity and sensors, virtualization and more. It is designed to meet the requirements of higher global coverage, greater spectral efficiency, a reduced carbon footprint, with an emphasis on sustainability, equity, trust and security through unprecedented architectural evolutions and technology. 6G will be an integrated network system that includes a traditional terrestrial mobile network, space network, and underwater network to provide ubiquitous network access. Even if there are studies on vision of 6G network that have already been published, there is still a significant amount of ground to cover. There is no decision made yet regarding anything and nothing has been ruled out. The focus of this study is to identify a complete picture of changes in architectures, technologies, and challenges that will shape the 6G network. We hope the research results will provide indications for further studies on 6G ecosystems.

Nullforming-Based Precoder for Spectrum Sharing Between HAPS and Terrestrial Mobile Networks

Ultra-wide coverage is one of the important concepts of the sixth generation (6G) mobile communications. High-altitude platform stations (HAPSs) have attracted considerable attention as a leading candidate for coverage extension of cellular networks. HAPSs should share a frequency band with terrestrial cellular networks and provide users with mobile communication services using the common frequency band to improve spectral efficiency in service links. However, the signals from HAPS strongly interfere with terrestrial cells in the service area of HAPS, which leads to a considerable deterioration in the system capacity of terrestrial cells. This study proposes a novel two-stage precoding scheme that realizes spectrum sharing between HAPS and terrestrial networks. The proposed scheme mitigates HAPS interference with terrestrial cells using beamforming techniques in phased array antenna systems. In the first stage, nulls are created in directions of terrestrial cells. In the second stage, user-specific beams are formed in directions of users connected to HAPS. Results demonstrate that the proposed scheme improves the signal-to-interference-plus-noise ratio of users in terrestrial cells by up to 10 dB compared with a conventional minimum mean square error (MMSE) precoder without nullforming when the HAPS uses a cylindrical array antenna with 196 elements. Furthermore, for ten terrestrial cells, the proposed scheme achieves 128% of total capacity of the conventional MMSE precoder. Total capacity is defined as the sum capacity of HAPS and all terrestrial cells.

Spectrum Sharing for 6G Integrated Satellite-Terrestrial Communication Networks Based on NOMA and CR

The explosive growth of bandwidth-hungry Internet applications have led to the rapid development of new generation mobile network technologies that are expected to provide broadband access to the Internet in a pervasive manner. For example, 6G networks are capable of providing high-speed network access by exploiting higher frequency spectrum; high-throughout satellite communication services are also adopted to achieve pervasive coverage in remote and isolated areas. In order to enable seamless access, integrated satellite-terrestrial communication networks (ISTCNs) have emerged as an important research topic, which aim to provide high-speed and pervasive network access by integrating broadband terrestrial mobile networks with satellite communication systems. As the terrestrial networks have begun to use higher frequency bands that overlap with those of the satellite networks, the satellite terminals can potentially access the terrestrial networks in an integrated manner. However, more efficient spectrum management techniques are needed to reduce the congestion and interference caused by spectrum sharing. In this article, we seek to improve satellite-terrestri-al spectrum sharing performance by introducing non-orthogonal multiple access (NOMA) and cognitive radio (CR) in the spectrum access of the ISTCN. Through fusing NOMA and CR, CR-NO-MA allows multiple satellite terminals to access both the idle and busy spectrum simultaneously, which will achieve high-efficiency full spectrum access. Furthermore, some open research and challenges for the spectrum sharing of the ISTCN are discussed.

Field Trial on 5G New Radio Over Satellite

5G New Radio (NR) is the 3rd Generation Partnership Project (3GPP) radio access technology for the next generation mobile communications network. A major evolution of 5G constitutes the integration of non-terrestrial networks including geostationary and low Earth orbit satellites. The seamless integration of satellites in the terrestrial mobile network requires significant adaptations within the radio access network and the development of new features in the core network to cope with the specific satellite channel characteristics. To date, the 5G control and data plane has been standardized to handle only continuous backhaul communication between the network components. However, a mobile satellite enabled next generation Node B (gNB) located in a vehicle or in a moving aerial platform needs to be able to handle frequent backhaul outages of various duration as well as longer signal delays as opposed to short terrestrial connections via fiber. In this paper, we report the results of an over-the-air (OTA) field trial comprising a mobile edge node connected to the 5G standalone core network components over a geostationary satellite. We analyze Transmission Control Protocol (TCP) acceleration and GPRS Tunneling Protocol (GTP)/TCP/Internet Protocol (IP) header compression features through the GTP. Moreover, the influence of short and long interruptions in the communication between the edge node and the central components on the entire system performance is investigated. The header compression and TCP acceleration modules were implemented on the satellite modems and are now part of the protocol stack of these devices. The results show up to 12% higher data rates for the 5G user equipment (UE), on a 1.5 MHz single carrier return link compared to deactivated TCP acceleration and header compression. We increased the data rate by 20% on the 4.5 MHz DVB-S2X forward link between the UE and 5G core. Moreover, our measurements reveal that even satellite-enabled gNB mobility is possible with the current Release 15 standard. After a short outage of the satellite connection due to shadowing, the UE can successfully re-establish the user plane connection to the core network. Our results will facilitate the full integration of satellite components in 5G through open and standard solutions.

Guest Editorial: Introduction to the Special Section on Heterogeneous Communications Networks

The papers in this special section focus on heterogeneous communication networks. These networks, consisting of terrestrial mobile networks, satellite networks, IoT, WiFi, and etc., is a promising technique to meet the challenges in future mobile communications. Heterogeneous network resources are expected to cooperate with each other to support more efficient data transmissions and also provide more reliable services. However, current network architectures cannot efficiently exploit the benefit of heterogeneous wireless communication networks. Considering the deficiency in existing wireless networks nowadays, the most substantial amount of future system performance gains will be obtained by means of heterogeneous network infrastructure densification. Therefore, the heterogeneous communication networks should be deeply investigated to realize the full benefits of each of them.

Worldwide Coverage Mobile Systems for Supra-Smart Cities Communications: Featured Antennas and Design

Current terrestrial mobile communications networks can’t provide worldwide coverage. Satellite communications are expensive, and terminals are large and heavy. Worldwide mobile coverage requires the use of satellites providing an appropriate QoS, including polar regions. The analysis of the potential satellite constellations demonstrates that LEO one is the best solution. A new generation of low cost, small size, lightweight and global mobile coverage LEO satellites is emerging. The main limitation of the terminals is the antenna size factor, and innovative antennas must be developed to meet this goal. This paper investigates the technologies and techniques for designing and developing antennas aimed at LEO satellite communications in Smart Cities and beyond, which are especially beneficial for mobile communications in areas without 4G/5G coverage. The paper focuses on the terrestrial segment and future mobile devices, remarking the design constraints. In this scenario, the paper reviews the most relevant technologies and techniques used to design suitable antennas. The investigation analyses the state-of-the-art and most recent advances in the design of antennas operating in the Ku-band. The main contribution of the authors is a novel antenna design approach based on SIW technology. The antenna features are compared with other approaches, highlighting the benefits, advantages and drawbacks. As a conclusion, the proposed antenna demonstrates to be a good solution to meet the design constraints for such an application: light, low cost, small size factor.

A survey on space-aerial-terrestrial integrated 5G networks

Abstract Thanks to their inherent advantages including large radio coverage and less dependence on terrestrial infrastructures, space and aerial networks can play an important role in 5G for ubiquitous coverage, large area broadcast services, and emergency communications. The space-aerial-terrestrial integrated networks (SATIN) are envisioned as an important trend of 5G evolution. However, due to distinct features including high altitude, moving platforms, large beam footprint and constrained payload, satellite networks are usually designed with unique protocols and functionalities, which hamper the integration of satellite networks with terrestrial mobile networks. The SATIN face many unprecedented technical challenges to achieve optimum performance, seamless user experience, and integrated security protection. This article makes a comprehensive overview of the latest researches from academia and industry to achieve the integrated 5G system. We first introduce the satellite and mobile technology trends, then present the vision of SATIN and related works in the area. Key enabling technologies from perspectives of the radio interface, networking, and security are discussed in depth. Then related standardization initiatives, especially the latest studies at 3GPP, and major industry research projects on non-terrestrial integrated 5G are reviewed. Important open issues are identified to inspire future studies for a fully integrated 5G system.

NPVT: Network Protocol Validation Testbed for Integrated Space-Terrestrial Network

With the development of the terrestrial network and the increase in demand for providing global Internet access, using the integrated space-terrestrial network (ISTN) has attracted significant attention to provide the global Internet service. However, ISTN faces a unique set of challenges, such as time-varying link quality and dynamic link connection in its space network, and the significant differences between space network and the terrestrial network of ITSN. These unique characteristics may impose an adverse impact on network protocols of ISTN. The focus of this paper is to design a network protocol validation testbed (NPVT) for ISTN. Using the static hardware devices with real network protocols, the proposed testbed was designed to emulate the dynamic space network based on the satellite operational data, and then to provide a near-real space network environment for the validation of diverse network protocols. To further support network protocol validation when space network and terrestrial network are integrated, we integrated the testbed with the terrestrial operational next-generation Internet (i.e., CERNET2) and mobile communication network at the backbone level. The extensive experiments demonstrated that NPVT is capable of validating diverse network protocols in complicated and dynamic scenarios.

A Survey on Green 6G Network: Architecture and Technologies

While 5G is being commercialized worldwide, research institutions around the world have started to look beyond 5G and 6G is expected to evolve into green networks, which deliver high Quality of Service and energy efficiency. To meet the demands of future applications, significant improvements need to be made in mobile network architecture. We envision 6G undergoing unprecedented breakthrough and integrating traditional terrestrial mobile networks with emerging space, aerial and underwater networks to provide anytime anywhere network access. This paper presents a detailed survey on wireless evolution towards 6G networks. In this survey, the prime focus is on the new architectural changes associated with 6G networks, characterized by ubiquitous 3D coverage, introduction of pervasive AI and enhanced network protocol stack. Along with this, we discuss related potential technologies that are helpful in forming sustainable and socially seamless networks, encompassing terahertz and visible light communication, new communication paradigm, blockchain and symbiotic radio. Our work aims to provide enlightening guidance for subsequent research of green 6G.

Design and measurement of a 5G mmW mobile backhaul transceiver at 28 GHz

High throughput and ultra low latency are the main requirements for fifth generation (5G) mobile broadband communications. Densely populated urban environments require utilization of previously underutilized millimeter wave frequency spectrum for higher data rates. The Ka-band, previously used in satellite applications, is of particular interest to terrestrial 5G mobile networks. New radio solutions are required for these frequencies, such as multiple wireless base stations organized in small cells and highly directional antennas to compensate for higher path loss. Wireless backhaul is predicted to be the most cost-effective and versatile solution to connect 5G base stations to the core network. Wireless backhaul enables flexible and easy installation of 5G base stations in ad hoc networks, supporting large crowd gatherings such as concerts and sports events. In this article, we present an architecture of a wireless backhaul transceiver, which operates on the 26.5–29.5-GHz band. The architecture described in this paper was implemented, and the performance of the receiver (Rx) array has been measured. We also present over-the-air antenna array measurement results using the Rx. The measurement results show that unequal Rx channel gains and antenna gains do not have a significant effect on the shape of the main lobe of the radiation pattern. We have measured a coherence gain of 2.7 dB from two Rx channels that is close to the theoretical value of 3.0 dB. We have achieved a conducted Rx EVM of better than 2% using a 100-MHz 16-QAM modulated signal at 26.5 GHz.

ADMM-Based Optimal Power Control for Cognitive Satellite Terrestrial Uplink Networks

This paper proposes an underlay power control scheme for cognitive satellite terrestrial uplink networks, where the primary terrestrial mobile network coexists with the secondary satellite communication network. In particular, the schemes are developed to guarantee that both the interference power constraints and interference outage probability constraints (IOPCs) of primary terrestrial users (PTUs) are satisfied. Since the IOPCs of PTUs belong to the chance constraint and the system throughput optimization model is non-convex, we first transform the IOPCs of PTUs into a series of equivalent transmit power constraints by using the Marcum-Q functions. Then, the alternating direction method of multipliers (ADMM) is introduced to derive the power allocation by alternatively optimizing the subproblems, each of which has the exact closed-form solution. The global convergence of the ADMM is guaranteed. Simulation results demonstrate the effectiveness of the proposed method.

Outage Performance of Cognitive Hybrid Satellite–Terrestrial Networks With Interference Constraint

This paper investigates the performance of a cognitive hybrid satellite–terrestrial network, where the primary satellite communication network and the secondary terrestrial mobile network coexist, provided that the interference temperature constraint is satisfied. By using the Meijer-G functions, the exact closed-form expression of the outage probability (OP) for the secondary network is first derived. Then, the asymptotic result in a high-signal-to-noise-ratio (SNR) regime is presented to reveal the diversity order and coding gain of the considered system. Finally, computer simulations are carried out to confirm the theoretical results and reveal that a more loose interference constraint or heavier shadowing severity of a satellite interference link leads to a reduced OP, whereas stronger satellite interference power poses a detrimental effect on the outage performance.

Special Issue: Smart Satellite Systems

Special Issue: Smart Satellite Systems

A Novel Satellite Telephone Communication System Based on SIGSO Satellite

In recent years, the coverage of terrestrial mobile communication network is more and more extensive, and the mobile phones have occupied the vast majority of voice communications in almost all countries. However, satellite voice communication system is still playing an irreplaceable role on the vast sea and the land area which are not covered by the land mobile communication network. The motion characteristics of the SIGSO satellites and its new demands and characteristics to the system are analyzed, and a novel very low rate satellite telephone system is put forward. The speech coding algorithms are studied, and a suitable speech coding algorithm and coding rate of 600bps is selected for the SIGSO satellite communication system. The overall design of the satellite voice communication network is given, including link budgets, network structure, system components, system signaling and so on. This satellite telephone system can get access to the PSTN network through ground gateway to achieve interoperability with the public network.

Hybrid Communication System Based on OFDM

A Hybrid architecture between terrestrial and satellite networks based on Orthogonal Frequency Division Multiplexing (OFDM) is employed here. In hybrid architecture, the users will be able to avail the services through the terrestrial networks as well as the satellite networks. The users located in urban areas will be served by the existing terrestrial mobile networks and similarly the one located in rural areas will be provided services through the satellite networks. The technique which is used to achieve this objective is called Pre-FFT adaptive beamforming also called time domain beamforming. When the data is received at the satellite end, the Pre-FFT adaptive beamforming extracts the desired user data from the interferer user by applying the complex weights to the received symbol. The weight for the next symbol is then updated by Least Mean Square (LMS) algorithm and then is applied to it. This process is carried out till all the desired user data is extracted.