The Internet of things (IoT) is transforming the whole of society. It represents the next evolution of the Internet and will significantly improve the ability to gather and analyze data, as well as the ability to control devices remotely. In this respect, the usage of connected devices is continuously growing with the expansion of the applications being offered to individuals and industries. To address IoT market needs, many low-power wide-area (LPWA) technologies have been developed, some operating on licensed frequencies (e.g., narrowband-IoT [NB-IoT] and Long-Term Evolution-M [LTE-M]), and others on unlicensed frequencies (e.g., LoRa, Sigfox, etc.). In this paper, we address the Release 13 of the NB-IoT 3rd generation partnership project (3GPP) standardized LPWA technology and provide a tutorial on its physical layer (PHY) design. Specifically, we focus on the characteristics and the scheduling of downlink and uplink physical channels at the NB-IoT base station side and the user equipment (UE) side. The goal is to help readers easily understand the NB-IoT system without having to read all the 3GPP specifications or the state-of-the-art papers that generally describe the system. To this end, each presented concept is followed by examples and concrete use-cases to further aid in the reader's comprehension. Finally, we briefly describe and highlight the new features added to the NB-IoT system in Releases 14 and 15.

Abstract-The continuously increasing traffic of Internet services (cloud services, video streaming, social networks and recently Internet of things services) is leading to a huge traffic growth in the core optical networks. This traffic evolution is pushing network operators to exploit efficiently their infrastructures in order to postpone, as much as possible, the expensive deployment of new infrastructures. In this respect, the migration from fixed to flex-grid optical networks was triggered in order to efficiently use optical network capacity taking benefits from the improved spectral efficiency of flexible transponders. In our previous work [1], we demonstrated that migrating towards flexible networks while keeping in use existing optical amplifiers will cause power saturation problem over highly loaded links due to the increase in the number of optical channels. To overcome this problem, we proposed in [1] a power adaptation process that consists on converting transmission performance margins into optical power attenuation over optical links. However, the realized work considered only transparent optical network controlled by GMPLS protocol suite. In this paper, we consider the case of translucent optical network where optical regeneration is required and thus the power adaptation process is adapted to such kind of network. New routing algorithm and protocol extensions are proposed to take into account power and regeneration information in the GMPLS control plane of translucent networks.

This paper deals with channel estimation and equalization, as well as noise variance estimation in uplink narrowband-internet of things (NB-IoT) system. Different techniques are studied in the context of NB-IoT, such as least square (LS) and linear minimum mean square error (LMMSE) for channel estimation, and zero forcing (ZF) and MMSE for equalization. It is shown that a low-complexity application of MMSEbased methods is made possible in NB-IoT by taking advantage of the small number of subcarriers. Furthermore, a noise variance estimator is suggested based on the combination of two successive observations of pilots, assuming slowly varying channel. We also prove that the proposed estimator is efficient, and confirm by simulations that both LMMSE channel estimator and MMSE equalizer can use the estimated noise variance instead of the exact value without loss of performance.

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This paper proposes a flexible multi-standard digital frontend<br>(DFE) hardware architecture designed for three main<br>low-power wide-area (LPWA) technologies: LoRa, Sigfox,<br>and narrowband-Internet of things (NB-IoT).We demonstrate<br>the feasibility of an unified DFE architecture that fits the requirements<br>of these LPWA technologies. The proposed DFE<br>architecture has been implemented on a Spartan-6 field programmable<br>gate array (FPGA) within a base station receiver,<br>and tested using a universal software radio peripheral (USRP)<br>based platform. We show that the expected performance can be<br>achieved with low hardware complexity, in terms of memory<br>and logic requirements.