The International Telecommunication Union defined the requirements for 5G in the International Mobile Telecommunications 2020 (IMT-2020) standard in 2017. Since then, advances in technology and standardization have made the ubiquitous deployment of 5G via satellite a practical possibility, for example, in locations where terrestrial networks (TNs) are not available. However, it may be difficult for satellite networks to achieve the same performance as TNs. To address this, the IMT-2020 requirements for satellite radio interface technology have recently been established. In this paper, these requirements are evaluated through system simulations for the 3rd Generation Partnership Project New Radio non-terrestrial networks with a low Earth orbit satellite. The focus is on the throughput, area traffic capacity, and spectral efficiency requirements. It is observed that the downlink (DL) requirements can be met for user equipment with 2 receive antenna elements. The results also reveal that frequency reuse factor 1 (FRF1) may outperform FRF3 in DL with a dual-antenna setup, which is a surprising finding since FRF3 is typically considered to outperform FRF1 due to better interference reduction. For uplink (UL), 1 transmit antenna is sufficient to meet the requirements by a relatively large margin – a promising result given that UL is generally more demanding.

Due to the ongoing standardization and deployment activities, satellite networks will be supplementing the 5G and beyond Terrestrial Networks (TNs). For the satellite communications involved to be as efficient as possible, techniques to achieve that should be used. Multi-Connectivity (MC), in which a user can be connected to multiple Next Generation Node Bs simultaneously, is one such technique. However, the technique is not well-researched in the satellite environment. In this paper, an algorithm to activate MC for users in the weakest radio conditions is introduced. The algorithm operates dynamically, considering deactivation of MC to prioritize users in weaker conditions when necessary. The algorithm is evaluated with a packet-level 5G non-terrestrial network system simulator in a scenario that consists of a TN and transparent payload low earth orbit satellite. The algorithm outperforms the benchmark algorithms. The usage of MC with the algorithm increases the mean throughput of the users by 20.3% and the 5th percentile throughput by 83.5% compared to when MC is turned off.

The emerging Non-Terrestrial Networks (NTNs) can aid to provide 5G and beyond services everywhere and anytime. However, the vast emergence of NTN systems will introduce an unseen interference to both the existing satellite systems and Terrestrial Networks (TNs). For that, there is a need for novel ideas on how to efficiently utilize the co-existing systems with the ever-increasing competition on scarce spectrum resources. Dynamic Spectrum Sharing (DSS) is a promising technique in which different systems can operate on the same spectrum, thus increasing the spectrum efficiency and offering better coverage for the users. In this paper, we present a centralized scheme for achieving coordinated DSS to protect the primary TN while providing NTN with sufficient resources. The scheme is evaluated by system simulations in a scenario with a TN and low earth orbit satellite. The results reveal that in a low traffic demand situation, the primary TN users are not affected negatively while the NTN can provide service to the rural area. In high-demand traffic situations, the peak performance of the TN inevitably suffers but the TN cell edge and NTN users’ performance is improved.

To meet the increasing throughput and reliability demands, satellites may be used to complement the Fifth Gener-ation (5G) Terrestrial Networks (TNs). To increase the efficiency of the satellite communications involved, research on bandwidth-efficient techniques is needed. Multi-Connectivity (MC), where a user can be connected to multiple Next Generation Node Bs (gNBs) simultaneously, is one of such techniques. In this paper, the focus is on MC in NonTerrestrial Networks (NTNs) to improve users' experienced throughputs. First, a study of relevant specifications and algorithms is conducted. Then, the designed load-aware Secondary Node (SN) addition and traffic steering algorithms are presented and evaluated in a realistic two-satellite Low Earth Orbit (LEO) network scenario. The simulation results indicate that usage of MC can be beneficial in 5G NTNs.

3rd Generation Partnership Project (3GPP) is working on the specifications related to the 5G satellite component, i.e., 5G Non-Terrestrial Networks (NTN). 5G NTN specifications can be used to build different spaceborne or airborne 5G systems. This article presents a 5G NTN extension to an open-source Network Simulator 3 (ns-3) and its 5G extension (5G LENA). The objective is to use the resulting System Level Simulator (SLS) in 3GPP standardization to evaluate different system concepts and parameterizations.

We are studying the mobility performance, outage and the signaling overhead of conditional handover (CHO) in Fifth Generation New Radio (5G NR). We observe that CHO will bring mobility robustness and outage gain but could lead to significant increase in signaling if not properly parametrized. Also, self-organizing networks (SON) optimization for CHO and CHO triggering based on source quality are found to improve performance significantly without increased signaling.

We are studying the mobility performance and the associated reliability of dual connectivity (DC) between a Long Term Evolution (LTE) macro layer and a 5G small cell layer in an urban environment. We will observe that the reliability benefits of using basic DC as known from LTE are much smaller than expected. Significant improvements are achieved by introducing advanced extensions, but the residual outage will still not fulfill all the tight ultra-reliability limits in a scenario with meaningful mobility.

Power control is essential for uplink multi-user access of Long Term Evolution (LTE). It guarantees that the received uplink power is kept within reasonable dynamic range such that the weak signals from large distance users do not get lost due to limited resolution of the eNB's Analog-to-Digital Converter (ADC). Capacity optimization of the open loop power control (OLPC) parameter P0 is applicable cell-individually for Macro deployments but fails in combination with small cells using the same frequency carrier, i.e. in heterogeneous networks (HetNet). In this paper, we show that an autonomous cell-individual Self-Optimizing-Network (SON) algorithm using cell internal optimization criteria like power headroom (PHR) reports and receive power dynamic range to increase P0 leads to good performance in macro-only layout. However, for co-channel HetNet deployment with embedded pico cells the inter-cell interference among the layers must be taken into account by means of propagation information exchange. We present a novel enhanced HetNet SON approach for P0 optimization where P0 value for a pico is calculated based on network configuration and the path loss of the weak macro cell-edge User Equipments (UEs) Lmax. The results show that approach can limit the P0 at safe level when pico cell could cause too much inter-cell interference to macro cell and on the other hand has higher limits when pico cell UEs are not interfering macro cell. This method offers a simple way to boost uplink capacity in macro and HetNet layouts while taking the uplink dynamic range and inter-cell interference into account.

This paper presents extensive dynamic simulations of the non-transparent in-band relays working in the distributed scheduling mode. The simulation results show that in-band relays can improve noticeably the spectral efficiency without acquiring an additional radio spectrum. Also, packet transmission delays become smaller. An important outcome of the dynamic simulations is that it is very crucial to choose a correct relay zone size where the base station and relay nodes exchange data. Otherwise, throughput fairness of the whole system declines. It indicates an importance of the relay zone size adjustment algorithm that the base station must run.

The IEEE 802.16 technology defines several link level mechanisms to retransmit erroneous data. In this paper we compare the performance of the ARQ and HARQ mechanisms in the IEEE 802.16 networks. Our simulations results show that in general HARQ provides a better performance. However, ARQ can compete successfully with it due to a smaller signaling overhead. Furthermore, since ARQ does not require a dedicated uplink signaling channel for the acknowledgments messages, it results in better resources utilization in the uplink direction.

The IEEE 802.16 technology defines the ARQ mechanism that enables a connection to resend data at the MAC level if an error is detected. In this paper, we analyze the key features and parameters of the 802.16 ARQ mechanism. In particular, we consider a choice for the ARQ feedback type, an algorithm to build block sequences, a scheduling of the ARQ feedbacks and retransmissions, the ARQ block rearrangement, ARQ transmission window and ARQ block size. We run a number of simulation scenarios to study these parameters and how they impact a performance of application protocols. The simulation results reveal that the ARQ mechanism and its correct configuration play an important role in transmitting data over wireless channels in the IEEE 802.16 networks.