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.

Self-Organizing Networks (SON) aim at automation of network parameters to make the planning, configuration, management, optimization and healing of mobile radio access networks simpler and faster, and thus also more cost efficient. SON use case in this article is Mobility Robustness Optimization (MRO), which targets automatic detection and correction of handover (HO) parameterization. To this end we present novel simulation framework called Self-Organizing Simulator 3 (SonS3) that makes use of real network data to enable an accurate performance analysis of mobility related SON use cases. In addition, we present an MRO algorithm which adapts dynamically the Cell Individual Offset (CIO), and a performance analysis within a realistic urban scenario. The proposed MRO algorithm leads to an overall reduction of more than 30% in mobility problems without causing significant increase in number of HOs.

In 3rd Generation Partnership Project (3GPP), enhancements of Diverse Data Applications (eDDA) work item has targeted at improving always-on connectivity for smartphones, identifying and specifying mechanisms at the Radio Access Network (RAN) level to enhance the ability of 3GPP Long Term Evolution (LTE) to handle diverse traffic profiles. The key aspects are the Radio Resource Control (RRC) release timer for User Equipment (UE) state control between connected and idle modes, and Discontinuous Reception (DRX) targeted for minimizing the UE power consumption in connected state. There exist important tradeoffs between UE power consumption, Quality-of-Service and RAN/core network signalling load. What's more, these tradeoffs may be dependent on the UE mobility/velocity. In this article we study the effect of DRX and RRC release timer parameterization on UE mobility performance in heterogeneous networks. These results can be applied to parameter optimization of DRX and RRC release.

In wireless mobile networks quality of user experience changes dynamically and depends on large variety of factors. Because of that mobile operators are willing to timely and effectively evaluate provided Quality of Service (QoS) in their networks. Nowadays the main tool for monitoring network state and performance is drive testing. To replace this expensive and mostly manual procedure, concept of Minimization of Drive Tests (MDT) is being developed in 3GPP LTE standardization. One area where MDT is applied is QoS verification, where user satisfaction is evaluated on the basis of periodic reports which contain values of different Key Performance Indicators (KPIs). By analyzing these KPIs one could find users which are unsatisfied with the experienced QoS and optimize configuration parameters in the areas of the network where concentration of unsatisfied users is high. In this paper we introduce a data mining framework which allows to distinguish between satisfied and unsatisfied users in LTE mobile network on the basis of limited number of KPIs. In addition, we take into use a KPI ranking system which gives an ability to significantly reduce the number of analyzed variables without compromising the resulting accuracy.

In cellular networks it is envisioned an explosion of diverse data applications running in smart phones, which could increase significantly not only user plane but also control plane load in the network. Smart phones and their always-on applications introduce several challenges: From the network perspective, an increased amount of UEs/applications can increase the signaling load due to frequent state transitions and handover signaling. From the UE perspective, challenges of power consumption are evident, since UE would increasingly be in connected state. In this article we study the trade-off between releasing the UE into idle state vs. keeping the UE in connected state, in a LTE system. The results indicate that optimum performance can be achieved using UE specific RRC release timer and DRX configurations by taking advantage of traffic characteristics and UE mobility.

In this article we study and analyze the problems related to power limitation in Long Term Evolution (LTE) uplink (UL). Power control (PC) has been specified for LTE UL to account for pathloss and slow fading variations and minimize the interference. The maximum transmission power has been limited to 23 dBm. Especially in sparse networks, this can lead to so called power limitation, where the terminals at the cell edge are forced to use less power per Physical Resource Block (PRB) than needed. Power limitation could clearly increase the packet error probability and transmission delay due to increased number of retransmissions. This may be especially problematic for Radio Resource Control (RRC) messages, e.g. handover signaling, since their reliability affects evidently on user Quality of Service (QoS). In this article we have concentrated on power boosting to improve the RRC message reliability and the performance is evaluated by means of dynamic system level simulations. It may be concluded that power boosting notably reduces the power limitation probability and thus also improves the RRC signaling reliability.

This paper describes how LTE Rel' 8 power headroom report (PHR) can be used to detect outage problems in LTE networks. The paper outlines the proposed minimization of drive tests use case for PH triggered measurements, alleviates the problems in this proposal, and describes improvements which can help operators to gather more coverage and outage related information from their networks. The article points out, that the earlier proposal can lead to unnecessary signaling, it does not work always as supposed, and the existing measurements can be used to gather the same information. The study is conducted by simulating two different outage problem scenarios with a fully dynamic LTE system simulator.

In this paper we propose a radio problem detection based rescue handover for 3G Long Term Evolution (LTE). The radio problem detection based handover algorithm takes advantage of already existing Radio Link Failure (RLF) detection mechanism specified in 3GPP for LTE. In coverage limited scenarios as well as challenging interference and mobility conditions, the event triggered handover measurement report may not be even sent to Evolved NodeB at the time of RLF. In proposed algorithm UE shall monitor the downlink quality based on the cell-specific reference signal in order to detect the downlink radio link quality of the serving cell. In case of a detected radio link problem handover process is initiated to a better cell. The proposed handover algorithm is compared to the default UE assisted hard handover process by means of fully dynamic system level simulations. Based on the studies it can be concluded that the radio problem detection assisted handover algorithm decreases the amount of RLFs thereby improving the handover and system performance. Especially the RLFs that occur before the handover process is even started are basically non-existent.

In this article we have studied the coverage optimization for 3G Long Term Evolution (LTE) according to Minimization of Drive Tests (MDT) work item description in Third Generation Partnership Project (3GPP). Target for the MDT work item is to define a set of measurements and measurement reporting procedures, so that operators are able to collect measurement data from users and thereby reducing need for manual drive tests. The main focus of MDT is coverage optimization. We propose an extended Radio Link Failure (RLF) reporting for both coverage and mobility optimization use cases for MDT. In this paper the MDT studies and especially the benefits of extended RLF reporting and classification are analyzed by means of dynamic system level simulations. The RLFs are classified into three categories based on the content in extended RLF reports: coverage, handover parameterization and interference problem. It can be concluded that the coverage as well as other problems may be identified with quite high probability with only a minimal standardization effort.

This paper proposes a potential enhancement for Discontinuous Reception (DRX) operation in Long Term Evolution (LTE) networks. In Third Generation Partnership Project's (3GPP's) Release 8 it is specified that User Equipment (UE) may be configured with DRX which controls the UE's Physical Downlink Control Channel (PDCCH) monitoring activity. By allowing discontinuous monitoring of PDCCH the UE can switch its receiver circuitry on and off for battery saving purposes. However, if UE turns its receiver circuitry off it is not capable to neither perform nor send any Channel Quality Indicator (CQI) measurements to the network prior to 'on-duration' (i.e., activity) period. This means that the Evolved Node B (e- Node B) might not have accurate CQI information and the scheduling and resource allocation could be based on outdated CQI information. To avoid reduced performance caused by the out-of-date information, this paper evaluates a scheme where a CQI preamble period is introduced prior to the actual 'on duration' time. During the preamble period UE measures the CQI and sends the measurement result to the e-Node B. The performance of the scheme is evaluated together with Voice over IP (VoIP) service. Used tool is a dynamic system level simulator which enables detailed simulation of users in multiple cells with realistic call generation, propagation, fading and mobility models. In addition to VoIP performance the UE power consumption is also evaluated with a simple model. This paper concludes that the preamble scheme can lead to improved performance in terms of VoIP capacity, and that the improvements can be achieved with acceptable trade-off in terms of battery saving opportunities

In this paper we present and analyze different packet scheduling mechanisms for Voice-over-IP (VoIP) in UTRAN Long Term Evolution Downlink. Dynamic packet scheduling provides multi-user and frequency domain scheduling gain, but at the expence of high control channel utilization. VoIP service with high number of simultaneous users and small packets can cause the control channel consumption to be the bottleneck for VoIP performance. Thus several persistent packet scheduling mechanisms have been proposed in 3GPP, such as fully persistent, talk-spurt based persistent and semi-persistent packet scheduling. We analyze the VoIP performance of different packet scheduling mechanisms by using fully dynamic system level simulations. We observe that with dynamic packet scheduling the VoIP capacity is restricted by the control channel capacity, whereas with persistent scheduling the capacity is restricted by the delay budget due to worse PRB SINR and resulting increased number of retransmissions.

In this paper we study the packet scheduling of mixed traffic in UTRAN long term evolution downlink. A dynamic packet scheduling (PS) architecture with service classification, queue specific sorting and scheduling algorithms as well as frequency domain PS has been presented to differentiate scheduling of different traffic classes. Simulation results have been provided by using control data, voice-over-IP (VoIP) and best effort (BE) traffic types. The results show that VoIP prioritizing is needed to keep the VoIP UEs satisfied. However, the strict prioritizing decreases the system spectral efficiency to around 70-80% of the pure BE spectral efficiency due to small VoIP packets.

In this paper, we study VoIP capacity in UTRA Long Term Evolution downlink under different mobility conditions. Since LTE is designed to be a wide area system supporting very high mobility, VoIP capacity for different mobility conditions is an important measure for the LTE system. We show how the mobility dynamics affect the VoIP capacity, using a dynamic system simulator to model the effects of both Robust Header Compression (ROHC) and handovers. The results indicate that the effect of non-ideal ROHC to VoIP system capacity is minimal, especially when compared to the mobility effects to system capacity.

In this paper we evaluate the performance of channel quality indicator (CQI) reporting schemes in 3GPP UTRAN long term evolution (LTE) downlink (DL). In LTE, time and frequency dependent CQI is needed for DL packet scheduling (PS) and fast link adaptation (LA). Studies have indicated that frequency domain PS (FD-PS) and LA are essential techniques in improving the LTE performance, giving e.g. both cell throughput and coverage gain of around 40 % over a distributed multiplexing scheme. However, there is a tradeoff with signaling overhead related to the CQI feedback and overall LA and PS performance, which is rather overlooked in the literature. We analyze four different CQI reporting schemes with respect to system spectral efficiency and conclude that the best-M average and threshold based CQI reporting schemes seem to be the most promising in terms of the compromise between system performance and signaling overhead.

In this paper, we study voice-over-IP (VoIP) performance in UTRA long term evolution (LTE) downlink (DL). We have utilized fully dynamic system simulations to study the VoIP adaptive multi-rate (AMR) 12.2 codec capacity in four different 3GPP simulation cases. The effects of link adaptation (LA), packet bundling, control channel capacity and number of HARQ processes on VoIP capacity have also been considered. The results present the absolute VoIP capacity numbers of LTE DL. We also show that LA together with packet bundling provides clear gain on the VoIP capacity, because more VoIP packets can be scheduled in each TTI. Also, the control channel limitations can be effectively compensated by packet bundling.

Flow-based fast handover for mobile IPv6 (FFHMIPv6) is a new handover method designed for mobile IP networks. The FFHMIPv6 uses the flow-state information and packet encapsulation to enable reception of packets simultaneously with the address registration process of mobile IPv6. Analysis and performance evaluation of FFHMIPv6 shows it handles the handover delay more efficiently than the basic mobile IPv6, hierarchical MIPv6, as well as fast handovers for MIPv6 handover mechanisms. However, if FFHMIPv6 is to be the primary mechanism for handover in mobile IP networks it has to be secure, efficient as well as reliable alternative to the existing handover mechanisms. In this paper, we present the security analysis and assessment of FFHMIPv6. We also recommend solutions to the identified security vulnerabilities and defense mechanisms to FFHMIPv6. The major security threat of FFHMIPv6 is related to the process of Flow-based fast handover binding update (FFHBU).

In this paper we discuss the problem related to interface selection in a multihomed mobile host. Traditional signal strength or priority based handover algorithms may not be sufficient for providing an always-best-connected access for the user in a heterogeneous multi-access environment. We present the policy based handover logic of VERHO mobility management system, where handover decisions are made in a more intelligent way with several affecting cross-layer parameters, policies and interface selection algorithms. Mainly, in this paper, we concentrate on comparing and analyzing different interface selection algorithms in Matlab simulations to find out the best alternative for the VERHO system

In this paper we present a common triggering mechanism (cross-layer framework) and logic to gather link state and quality related information from the link layers of different access technologies. This information may he utilized by upper layer protocols and applications to react to changes of the link layer. Examples of such a utilization is movement detection, handover decision and application adaptation. The access technology dependent events and parameters, when necessary, are converted into access technology independent triggers and hints. The presented prototype architecture, link information provider (LIP), is currently tested with the VERHO vertical handover controller, which enables intelligent policy-based handover decisions according to several input parameters from the user, application, link layer, etc. Currently, LIP supports certain general link layer parameters, which can he gathered from the operating system and network interface drivers. The system is designed to be easily extended.