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The explosive growth of connected objects is certainly one of the most important challenges facing operators' network infrastructures. Although it has been foreseen for a very long time, it is still not clear how to support such huge number of devices efficiently. Indeed, although a smarter planning of dedicated access slots would certainly limit the burden, this remains limited since some equipments react to events, which cannot be timed. Moreover, barring some IoT devices from accessing the network, using Access Class Barring–like techniques, is very efficient; nevertheless, efficiency is generally linked to precise knowledge of the number of contending devices. Although, before connection establishment, the terminals are invisible to access points, it is very difficult to estimate their number. A lower bound of backlogged devices can be determined. The average number of terminals can even be estimated with more or less precision, as this kind of problems comes to the classical “balls‐into‐bins” problem, which was extensively analyzed in the literature. However, an overestimation of this number implies underutilization of resources whereas an underestimation may lead to a congestion collapse. In this way, we propose a lightweight change to the standard to accurately reveal the state of network congestion by overloading connections' requests with the number of access attempts (number of times the device has been barred as well as the number of attempts). Using such information, we propose an accurate recursive estimator of the number of devices. The obtained results demonstrated that the proposed solution not only makes it possible to estimate the number of equipment much better than existing techniques but also allows determining precisely the number of blocked equipments.

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In order to achieve ubiquitous coverage and service continuity in future 5G network, satellite-based access is the best solution to complement the terrestrial LTE-A. In light of this, we introduce a channel-aware hybrid scheduling technique on the basis of satellite-LTE spectrum sharing. According to the user-experienced channel, base stations (eNodeB) and the satellite will work cooperatively. The eNodeB mainly provides service in urban area for high density population. Meanwhile, the satellite will perform either offloading, providing service for under-served users, or extra coverage for users in rural and remote areas having no coverage of eNodeB. Leveraging the multiuser diversity, we implement a new metrics computation method for hybrid satellite-LTE downlink scheduler (H-MUDoS). Compared with other existing schedulers, simulation results clearly demonstrate the high performance of H-MUDoS in terms of spectral efficiency in addition to improvement of the quality-of-service requirements and capacity maximization. KEYWORDS hybrid architecture, LEO satellite, LTE-A, offloading, scheduling, spectral efficiency, 5G | INTRODUCTIONThe increasing demands of data traffic in addition to limited available spectrum puts more pressure and challenging issues on emerging 5G network expectations. Thus, investigations in innovative technologies in the heterogeneous terrestrial-satellite network are crucial to address the 5G dilemma. In addition, considering the lack of coverage in many regions (about 71% of rural population are not covered 1 in 2015), ubiquitous on-demand coverage is a key enabler to ensure the future 5G network paradigm. As a matter of fact, the satellite component is fundamental to provide 5G services anywhere anytime either by providing a backhaul or through direct access. It is expected that the satellite solution will be a part of the hybrid network configuration in 5G HetNet. 2 In fact, global coverage remains the major added value of satellite communications. 3 The O3b project aims to extend the coverage for "The Other 3 Billion" population of the world where broadband internet is unavailable. 4 Moreover, the satellite solution comes to the rescue when terrestrial infrastructure is unavailable and remains the best solution for public safety or in emergency situations. On top of this, the cost of exclusive terrestrial coverage is unbearable to address the increasing data traffic and network demand for rural and remote areas.Kuang et al 1 describe the coverage cost on the basis of "long tail" concept distribution. As a matter of fact, satellite technology is cost-effective in rural and remote areas in addition to urban/suburban areas. Meanwhile, the mobile terminals are more and more miniaturized compared with the past ones, ie, Thuraya XT-PRO, which is supported by the most robust and powerful satellite network. Thanks to its advanced omnidirectional antenna Thuraya XT-PRO offers full walk-and-talk capability in addition to an uninterrupted signal even in the harshest environments. 5 next generation ne...

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