Looking at NB-IoT over LEO Satellite Systems: Design and Evaluation of a Service-Oriented Solution

The adoption of the NB-IoT technology in satellite communications intends to boost Internet of Things services beyond the boundaries imposed by the current terrestrial infrastructures. Apart from link-level studies in the scientific literature and preliminary 3GPP technical reports, the overall debate is still open. To provide a further step forward in this direction, the work presented herein pursues a novel service-oriented methodology to design an effective solution, meticulously stitched around application requirements and technological constraints. To this end, it conducts link-level and system-level investigations to tune physical transmissions, satellite constellation, and protocol architecture, while ensuring the expected system behavior. To offer a real smart agriculture service operating in Europe, the resulting solution exploits 24 Low Earth Orbit satellites, grouped into 8 different orbits, moving at an altitude of 500 km. The configured protocol stack supports the transmission of tens of bytes generated at the application layer, by also counteracting the issues introduced by the satellite link. Since each satellite has the whole protocol stack on-board, terminals can transmit data without the need for the feeder link. This ensures communication latencies ranging from 16 minutes to 75 minutes, depending on the served number of terminals and the physical transmission settings. Moreover, the usage of the Early Data Transmission scheme reduces communication latencies up to 40%. These results pave the way towards the deployment of an effective proof-of-concept, which drastically reduces the time-to-market imposed by the current state of the art

Performance assessment of NB-IoT protocol over satellite channels

Abstract Cellular networks play a very important role in nowadays paradigm which goal is to establish connectivity all around the world. Low power wide area networks (LPWAN) seem to fit well within low-cost devices, which constitute a great part of the electronics market. In this context, the narrowband internet of things (NB-IoT) protocol specified by the 3GPP is consolidating as one of the most adopted technologies in the field of LPWAN, together with LoRaWAN. With the goal of reaching global coverage, the NB-IoT protocol, which was mainly designed for terrestrial cellular networks, is now being extended to be able to work also on satellite networks. The support of satellite access is seen as the enabler of truly massive machine-type communications (mMTC) into areas that cellular connectivity is limited or inexistent (remote areas, air and sea communications). This thesis provides a performance assessment of the NB-IoT protocol under different satellite link conditions and transmission modes. The assessment is conducted using the MATLAB LTE Toolbox.Las redes móviles tienen un papel muy importante en la actualidad, puesto que tienen como objetivo establecer conectividad en todo el mundo. Las redes de bajo consumo y largo alcance (LPWAN) parecen encajar bien en un entorno donde los dispositivos de bajo coste constituyen una gran parte del mercado de la electrónica. En este contexto, el protocolo NB-IoT especificado por el 3GPP se consolida como una de las tecnologías más adoptadas en el contexto de LPWAN, junto con LoRaWAN. Con el objetivo de conseguir una cobertura global, el protocolo NB-IoT, que fue diseñado principalmente para redes de telefonía terrestre, ahora se está ampliando para poder trabajar también en redes de satélite. El acceso por satélite es visto como la puerta hacia las comunicaciones de tipos máquina masiva (mMTC) en áreas donde la conectividad celular es limitada o inexistente (áreas remotas, comunicaciones aéreas y marítimas). Esta tesis proporciona una evaluación del rendimiento del protocolo NB-IoT bajo diferentes condiciones de enlace por satélite y modos de transmisión. La evaluación se realiza utilizando la caja de herramientas MATLAB LTE.Les xarxes mòbils tenen un paper molt important en l'actualitat, ja que tenen com a objectiu establir connectivitat a tot el món. Les xarxes de baix consum i llarg abast (LPWAN) semblen encaixar bé en un entorn on els dispositius de baix cost constitueixen una gran part del mercat de l'electrònica. En aquest context, el protocol NB-IoT especificat pel 3GPP es consolida com una de les tecnologies més adoptades en el context de LPWAN, juntament amb LoRaWAN. Amb l'objectiu d'aconseguir una cobertura global, el protocol NB-IoT, que va ser dissenyat principalment per a xarxes de telefonia terrestre, ara s'està ampliant per poder treballar també en xarxes de satèl·lit. L'accés per satèl·lit és vist com la porta cap a comunicacions de tipus màquina massiva (mMTC) en àrees on la connectivitat cel·lular és limitada o inexistent (àrees remotes, comunicacions aèries i marítimes). Aquesta tesi proporciona una avaluació del rendiment del protocol NB-IoT sota diferents condicions d'enllaç per satèl·lit i modes de transmissió. L'avaluació es realitza utilitzant la caixa d'eines MATLAB LTE

NB-IoT via LEO satellites: An efficient resource allocation strategy for uplink data transmission

In this paper, we focus on the use of Low-Eart Orbit (LEO) satellites providing the Narrowband Internet of Things (NB-IoT) connectivity to the on-ground user equipment (UEs). Conventional resource allocation algorithms for the NBIoT systems are particularly designed for terrestrial infrastructures, where devices are under the coverage of a specific base station and the whole system varies very slowly in time. The existing methods in the literature cannot be applied over LEO satellite-based NB-IoT systems for several reasons. First, with the movement of the LEO satellite, the corresponding channel parameters for each user will quickly change over time. Delaying the scheduling of a certain user would result in a resource allocation based on outdated parameters. Second, the differential Doppler shift, which is a typical impairment in communications over LEO, directly depends on the relative distance among users. Scheduling at the same radio frame users that overcome a certain distance would violate the differential Doppler limit supported by the NB-IoT standard. Third, the propagation delay over a LEO satellite channel is around 4-16 times higher compared to a terrestrial system, imposing the need for message exchange minimization between the users and the base station. In this work, we propose a novel uplink resource allocation strategy that jointly incorporates the new design considerations previously mentioned together with the distinct channel conditions, satellite coverage times and data demands of various users on Earth. The novel methodology proposed in this paper can act as a framework for future works in the field.Comment: Tis work has been submitted to the IEEE IoT Journal for possible publication. Copyright may be transferred without notice, after which this version may no longer be accessibl

Active Terminal Identification, Channel Estimation, and Signal Detection for Grant-Free NOMA-OTFS in LEO Satellite Internet-of-Things

This paper investigates the massive connectivity of low Earth orbit (LEO) satellite-based Internet-of-Things (IoT) for seamless global coverage. We propose to integrate the grant-free non-orthogonal multiple access (GF-NOMA) paradigm with the emerging orthogonal time frequency space (OTFS) modulation to accommodate the massive IoT access, and mitigate the long round-trip latency and severe Doppler effect of terrestrial-satellite links (TSLs). On this basis, we put forward a two-stage successive active terminal identification (ATI) and channel estimation (CE) scheme as well as a low-complexity multi-user signal detection (SD) method. Specifically, at the first stage, the proposed training sequence aided OTFS (TS-OTFS) data frame structure facilitates the joint ATI and coarse CE, whereby both the traffic sparsity of terrestrial IoT terminals and the sparse channel impulse response are leveraged for enhanced performance. Moreover, based on the single Doppler shift property for each TSL and sparsity of delay-Doppler domain channel, we develop a parametric approach to further refine the CE performance. Finally, a least square based parallel time domain SD method is developed to detect the OTFS signals with relatively low complexity. Simulation results demonstrate the superiority of the proposed methods over the state-of-the-art solutions in terms of ATI, CE, and SD performance confronted with the long round-trip latency and severe Doppler effect.Comment: 20 pages, 9 figures, accepted by IEEE Transactions on Wireless Communication

Smart Beamforming for Direct Access to 5G-NR User Equipment from LEO Satellite at Ka-Band

Study how spatial diversity can help in massive IoT and develp signal processing access for MIMO beamformingNon-Terrestrial Networks (NTN), in particular LEO Satellite Networks, are expected to play a key role in extending and complementing terrestrial 5G networks in order to provide services to air, sea and un-served or under-served areas. This work proposes the implementation of a novel scheme called Resource Sharing Beamforming Access (RSBA), which seems a promising solution to deal with scenarios where Bit Error Rate (BER), probability of collision and/or achievable rate are important aspects of study. Given the system architecture presented in this work, RSBA will be proposed as solution in the 5G-NR Sat-IoT scenario. As it is expected, a huge amount of IoT devices will be transmitting in the uplink, and being the case of Non-Orthogonal-Multiple-Access (NOMA), the risk of collisions between devices will increase. The idea, after assessing the channel impairments of a direct link between a LEO Satellite and a NB-IoT device, it to study how spatial diversity via smart beamforming at the receiver will reduce the probability of collision between the devices, and thus increasing the number of users that can access to the media

Evolution of High Throughput Satellite Systems: Vision, Requirements, and Key Technologies

High throughput satellites (HTS), with their digital payload technology, are expected to play a key role as enablers of the upcoming 6G networks. HTS are mainly designed to provide higher data rates and capacities. Fueled by technological advancements including beamforming, advanced modulation techniques, reconfigurable phased array technologies, and electronically steerable antennas, HTS have emerged as a fundamental component for future network generation. This paper offers a comprehensive state-of-the-art of HTS systems, with a focus on standardization, patents, channel multiple access techniques, routing, load balancing, and the role of software-defined networking (SDN). In addition, we provide a vision for next-satellite systems that we named as extremely-HTS (EHTS) toward autonomous satellites supported by the main requirements and key technologies expected for these systems. The EHTS system will be designed such that it maximizes spectrum reuse and data rates, and flexibly steers the capacity to satisfy user demand. We introduce a novel architecture for future regenerative payloads while summarizing the challenges imposed by this architecture

Study of the 5G NB-IoT protocol with low density LEO Constellations of nanosatellites

The NB-IoT protocol, specified by 3GPP, is one of most popular and widely used technology for low-power wide-area (LPWA) networks. To further strengthen the potential of this technology, 3GPP is currently developing an extension of the NB-IoT protocol for non-terrestrial networks (NTN), so that terrestrial coverage could be extended using satellite-based network deployments and reach global coverage. The first part of this Master's Thesis focuses on the development of a MATLAB simulation software for the characterization of a NB-IoT NTN deployment scenario in terms of satellite coverage footprint (e.g. SNR distributions) and dynamics of the satellite link during a satellite pass (e.g. time evolution of the SNR and Doppler).Among the simulator inputs, there are the satellite height, the spherical geometry of the earth, the parameters associated with the satellite, such as orbit or speed, the transmission power, frequency, pathloss, etc... The simulator allows selecting the different inputs such as NTN parameters, link budget parameters or antenna type. These inputs, which are completely configurable, are used to obtain a set of outputs that allow to characterize the NB-IoT NTN scenario, such as the characterization of the satellite coverage footprint, the antenna pointing or the characterization of the satellite pass. For each characterization, the different parameters and results obtained, such as SNR heatmaps, Doppler frequency or propagation delay, are studied in more detail. The second part of the study is aimed at evaluating the performance of the NB-IoT NTN protocol over a satellite link. For this purpose, different numerical simulations have been performed, to estimate the minimum SNR and achievable spectral efficiency of the protocol for different communication models channels (e.g. AWGN and TDL channels, frequency offsets), different protocol configurations (e.g. number of repetitions, modulation and coding schemes) as well as considering different channel estimators. The analysis has been conducted for both downlink and uplink data channels (e.g. NPDSCH and NPUSCH). Simulations of NPDSCH Block Error Rate (BLER) and NPUSCH Block Error Rate (BLER) from the MATLAB LTE toolbox, modified and adapted to non-terrestrial communications with LEO satellites, are performed