Ubiquitous connectivity is the most significant goal of sixth-generation (6G) wireless networks. To this end, integrating non-terrestrial networks (NTNs) with terrestrial networks (TN) can be an inevitable path to 6G. To achieve cost-effectiveness and bandwidth efficiency in NTN design, the open radio access network (O-RAN) and integrated access and backhaul (IAB) approaches, which prevail in TN, are adopted in the proposed NTN architecture. To maximize the uplink rate under bandwidth and power constraints, we jointly optimize i) the power allocation to pilot and data symbols, ii) the compression rates for inter-satellite link (ISL) transmission of pilot and data, and iii) the bandwidth partitioning between the access link and the xHaul link. Because the original optimization problem is challenging to solve directly, it is decomposed into three subproblems: power, compression rate, and bandwidth optimization, while the other parameters being kept fixed. The convergent solution is obtained via an iterative optimization approach that alternates between optimization and a gradient-based search. The effectiveness of the proposed approach is verified by numerical simulations.

Due to the high altitudes and large beam sizes of satellites, the curvature of the Earth’s surface can impact system-level performance. To consider this, 3GPP introduces the UV-plane beam mapping for system-level simulations of non-terrestrial networks (NTNs). This paper aims to provide a comprehensive understanding of how beams and user equipments (UEs) are placed on the UV-plane and subsequently mapped to the Earth’s surface. We present a general process of projecting UEs on the UV-plane onto the Earth’s surface. This process could offer a useful guideline for beam and UE deployment when evaluating the system-level performance of NTNs.

This paper proposes performance improvements based on CSS waveform for High Doppler environments such as LEO and high-speed vehicles. Specifically, we refer to the Lora waveform in this paper and the performance assessment has been presented under the LEO satellite channel impairments.

Standardization for non-terrestrial network (NTN) including satellite is in progress in 3GPP, the International Organization for Standardization of Wireless Communications. Currently, in RAN 1, various companies contributing to standardization are submitting simulation results to calibrate the results of link level simulation, which requires simulator design for transmitters and NTN channels that meet the 3GPP NR standard. In this paper, the block diagram of the transmitter and the NTN channel is created, and a configuration for this is described. Then simple simulation result will be shown.

This paper presents the structure of terminal ASIC chip with low speed, low power, and small characteristics for satellite IoT transmission. The external connection with the sensor, flash external, and tuner will be made centering on the ASIC chip. Three transmission waveforms, such as the LoRa, I-LoRa, and LoRa-E, will be used to send the collected data to LEO satellite. As a result, the data collected from the sensor is transmitted to the ASIC chip through the sensor interface, and the ASIC chip modulates the collected data into an uplink signal and sends it to LEO satellite through the tuner.

Low-earth orbit (LEO) satellites based low-power Internet of Things (IoT) service has attracted attention to provide the hyper-space communication networks in 6G communication. In this paper, we study the regression based pilot design for estimation and compensation of the Doppler effect caused by the high-speed mobility of the LEO satellite.

In this paper, we have presented the performance results of NR-compliant waveforms under nonlinear HPA channels which also can be candidates for B5G/6G satellite communication for integrated terrestrial and satellite networks.

This paper proposes a new systematic analysis framework for the LEO satellite networks by focusing on the orbit geometry. By modeling LEO satellite orbits as a Poisson line process, we characterize the distribution of the total length of the visible orbit region observed by the typical user.

In this paper, we consider downlink low Earth orbit (LEO) satellite communication systems where multiple LEO satellites are uniformly distributed over a sphere at a certain altitude according to a homogeneous binomial point process (BPP). Based on the characteristics of the BPP, we analyze the distance distributions and the distribution cases for the serving satellite. We analytically derive the exact outage probability, and its approximated expression is obtained using the Poisson limit theorem. With these derived expressions, the system throughput maximization problem is formulated under the satellite-visibility and outage constraints. To solve this problem, we reformulate it with bounded feasible sets and propose an iterative algorithm to obtain near-optimal solutions. Simulation results perfectly match the derived exact expressions for the outage probability and system throughput. The analytical results of the approximated expressions are fairly close to those of the exact ones. It is also shown that the proposed algorithm for the throughput maximization is very close to the optimal performance obtained by a two-dimensional exhaustive search.

This paper considerssatellite eavesdroppersin uplink satellite communication systems where the eavesdroppers are randomly distributed at arbitrary altitudes according to homogeneous binomial point processes and attempt to overhear signals that a ground terminal transmits to a serving satellite. Non-colluding eavesdropping satellites are assumed, i.e., they do not cooperate with each other, so that their received signals are not combined but are decoded individually. Directional beamforming with two types of antennas: fixed- and steerable-beam antennas, is adopted at the eavesdropping satellites. The possible distribution cases for the eavesdropping satellites and the distributions of the distances between the terminal and the satellites are analyzed. The distributions of the signal-to-noise ratios (SNRs) at both the serving satellite and the most detrimental eavesdropping satellite are derived as closed-form expressions. The ergodic and outage secrecy capacities of the systems are derived with the secrecy outage probability using the SNR distributions. Simpler approximate expressions for the secrecy performance are obtained based on the Poisson limit theorem, and asymptotic analyses are also carried out in the high-SNR regime. Monte-Carlo simulations verify the analytical results for the secrecy performance. The analytical results are expected to be used to evaluate the secrecy performance and design secure satellite constellations by considering the impact of potential threats from malicious satellite eavesdroppers.

In this paper, we analyze the performance impact when the direct sequence spread spectrum aloha scheme in LEO satellite channel for global IoT service is applied. It is expected that satellite communication can play a significant role for mMTC item, the one of 5G representative service models in terms of service coverage extension. Moreover, the usability of hybrid satellite-terrestrial user terminal (or user equipment) with limited power emission capability can be considered in case of the scenario of direct connectivity to LEO satellite where terrestrial signal is not reached. In this paper, we applied the Ingenu-like waveform based on IEEE 802.15.4k standard to LEO satellite channel which has been deployed in unlicensed ISM 2.4GHz and the main elements related with throughput performance are presented.

In this paper, we study the provision of broadband interactive services to passengers of Korean high-speed train in the ISM 2.4 GHz band. We address in particular the design of tunnel gap-fillers (GFs) able to provide bi-directional connectivity to train-based terminals. The work has been developed in the broader context of interactive services provision for high-speed trains through satellite networks. First, a channel model for the in-tunnel propagation is derived. Taking into account the results of the propagation analysis, a comparison between commercial technologies (belonging to both the IEEE and the DVB standard families) is provided, showing the possible strengths and weaknesses of the proposed solutions with respect to architectural and performance point of views.