On the Random Access Procedure of NB-IoT Non-Terrestrial Networks

The standardization of the 5G systems has recently entered in an advanced phase, where non-terrestrial networks will be a new key feature in the upcoming releases. Narrowband Internet of Things (NB-IoT) is one of the technologies that will address the massive machine type communication (mMTC) traf- fic of the 5G. To meet the demanding need for global connectivity, satellite communications can provide an essential support to complement and extend the NB-IoT terrestrial infrastructure. However, the presence of the satellite channel comes up with new demands for the NB-IoT procedures. In this paper, we investigate the main challenges introduced by the satellite channel in the NB-IoT random access procedure, while pointing out valuable solutions and research directions to overcome those challenges

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 Delaying the scheduling of a certain user would result in a resource allocation based on outdated parameters.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

An Uplink UE Group-Based Scheduling Technique for 5G mMTC Systems Over LEO Satellite

Narrowband Internet of Things (NB-IoT) is one of the most promising IoT technology to support the massive machine-type communication (mMTC) scenarios of the fifth generation mobile communication (5G). While the aim of this technology is to provide global coverage to the low-cost IoT devices distributed all over the globe, the vital role of satellites to complement and extend the terrestrial IoT network in remote or under-served areas has been recognized. In the context of having the global IoT networks, low earth (LEO) orbits would be beneficial due to their smaller propagation signal loss, which for the low complexity, low power, and cheap IoT devices is of utmost importance to close the link-budget. However, while this would lessen the problem of large delay and signal loss in the geostationary (GEO) orbit, it would come up with increased Doppler effects. In this paper, we propose an uplink scheduling technique for a LEO satellite-based mMTC NB-IoT system, able to mitigate the level of the differential Doppler down to a value tolerable by the IoT devices. The performance of the proposed strategy is validated through numerical simulations and the achievable data rates of the considered scenario are shown, in order to emphasize the limitations of such systems coming from the presence of a satellite channel

Satellite Systems in the Era of 5G Internet of Things

In recent years, IoT applications have drawn a great deal of attention, both in academia and industry. A crucial requirement of any infrastructure serving the IoT market will be to guarantee ubiquitous connectivity to the low-cost, low-powered devices distributed all over the globe. It is widely accepted that this requirement will not be met by the terrestrial network alone. There will be, in fact, vast areas of the globe where the terrestrial infrastructure deployment will be unfeasible or not economically viable, thus leaving those areas un- or under-served. For this reason, several studies and projects are addressing the use of a Non-Terrestrial Network component to seamlessly complement and extend the terrestrial network coverage in future systems. The design of these extremely complex systems requires manifold analyses at different levels of abstraction, from satellite constellation and ground segment architecture aspects, to the evaluation of the air interface behaviour, in order to evaluate the system performance. The aim of this work is to perform a detailed analysis of the SatCom system aspects, trying to be as accurate as possible but without getting lost in unnecessary details, in order to provide a comprehensive set of tools, organised in a simulation platform, to support the design and performance evaluation of the system. Notably, simulation softwares play an important role in this framework; however, a full-featured simulation tool does not yet exist for the evaluation of the described emerging technologies. ESA M2M Simulator (ESiM2M) is a System-Level Simulator, developed in collaboration with the European Space Agency, which is intended for closing this gap, as a tool for the design and analysis, from a system-level point of view, of Satellite-IoT systems. This work is primarily focused on the description of the ESiM2M simulation tool and the results derived with the latter from analyses on Satellite-IoT systems