The introduction of Narrowband Internet of Things (NB-IoT) as a cellular (NB-IoT) technology aims to support massive Machine-Type Communications applications. These applications are characterized by massive connections from a large number of low-complexity and low-power devices. One of the goals of NB-IoT is to improve coverage extension beyond existing cellular technologies. In order to do that, NB-IoT introduces transmission repetitions and different bandwidth allocation configurations in uplink. These new transmission approaches yield many transmission options in uplink. In this paper, we propose analytical expressions that describe the influence of these new approaches in the transmission. Our analysis is based on the Shannon theorem. The transmission is studied in terms of the required Signal to Noise Ratio, bandwidth utilization, and energy per transmitted bit. Additionally, we propose an uplink link adaptation algorithm that contemplates these new transmission approaches. The conducted evaluation summarizes the influence of these approaches. Furthermore, we present the resulting uplink link adaptation from our proposed algorithm sweeping the device's coverage.
As a newly-developing technology, NB-IoT has still several issues to investigate. On the one hand, regarding NB-IoT performance, the authors of @cite_0 evaluate the coverage performance of NB-IoT. In @cite_8 , the authors also included results of capacity for a small rural area with real operator-deployed base stations. Nevertheless, these works and other similar provide final results for specific configurations that hinder the comparison of the results. Particularly, the authors of @cite_6 derive and simulate an analytical bound for the SNR gain from repetitions. On the other hand, the extensive use of repetitions in NB-IoT adds a new dimension for link adaptation that traditional LTE mechanisms do not consider. The works @cite_7 and @cite_4 examine this topic. The former proposed a downlink link adaptation algorithm. The latter investigated dynamic uplink link adaptation. However, neither of them examine analytically the impact of the repetitions. Additionally, the uplink link adaptation proposed in @cite_4 do not contemplate the bandwidth reduction as a new dimension in uplink link adaptation.
@cite_4 @cite_7 @cite_8 @cite_6 @cite_0
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Narrowband Internet of Things (NB-IoT) is a new narrow-band radio technology introduced in the Third Generation Partnership Project release 13 to the 5th generation evolution for providing low-power wide-area IoT. In NB-IoT systems, repeating transmission data or control signals has been considered as a promising approach for enhancing coverage. Considering the new feature of repetition, link adaptation for NB-IoT systems needs to be performed in 2-D, i.e., the modulation and coding scheme (MCS) and the repetition number. Therefore, existing link adaptation schemes without consideration of the repetition number are no longer applicable. In this paper, a novel uplink link adaptation scheme with the repetition number determination is proposed, which is composed of the inner loop link adaptation and the outer loop link adaptation, to guarantee transmission reliability and improve throughput of NB-IoT systems. In particular, the inner loop link adaptation is designed to cope with block error ratio variation by periodically adjusting the repetition number. The outer loop link adaptation coordinates the MCS level selection and the repetition number determination. Besides, key technologies of uplink scheduling, such as power control and transmission gap, are analyzed, and a simple single-tone scheduling scheme is proposed. Link-level simulations are performed to validate the performance of the proposed uplink link adaptation scheme. The results show that our proposed uplink link adaptation scheme for NB-IoT systems outperforms the repetition-dominated method and the straightforward method, particularly for good channel conditions and larger packet sizes. Specifically, it can save more than 14 of the active time and resource consumption compared with the repetition-dominated method and save more than 46 of the active time and resource consumption compared with the straightforward method. Coverage enhancement and low complexity are quite important aspects to support and broaden the application of machine type communication (MTC) in long term evolution (LTE). Repeating the same data across multiple subframes is widely considered as basic solution to improve the coverage. Low complexity target is mainly achieved by reducing the supported bandwidth and restricting the data processing size. Repetitions can be regarded as a new dimension of link adaptation besides the modulation and coding scheme (MCS) selection and the low complexity features are new factors impacting the link adaption as well. However, existing link adaptation mechanism in LTE system is unable to support such two-dimension link adaptation. Straightforward method suffers serious spectral efficiency loss and more power consumption and there is little other research on this issue, either. To save power and improve the spectral efficiency when performing the link adaptation for MTC, a smart method of coordinating the MCS selection and the repetition level determination with the consideration of new low complexity features is proposed in this paper. Extensive link level simulations are carried out to verify the effectiveness of proposed method. Simulation results show that proposed method could improve the spectral efficiency by around 42.1 and reduce the power consumption by around 36.8 The 3GPP has introduced the LTE-M and NB-IoT User Equipment categories and made amendments to LTE release 13 to support the cellular Internet of Things. The contribution of this paper is to analyze the coverage probability, the number of supported devices, and the device battery life in networks equipped with either of the newly standardized technologies. The study is made for a site specific network deployment of a Danish operator, and the simulation is calibrated using drive test measurements. The results show that LTE-M can provide coverage for 99.9 of outdoor and indoor devices, if the latter is experiencing 10 dB additional loss. However, for deep indoor users NB-IoT is required and provides coverage for about 95 of the users. The cost is support for more than 10 times fewer devices and a 2-6 times higher device power consumption. Thus both LTE-M and NB- IoT provide extended support for the cellular Internet of Things, but with different trade- offs. Narrow-Band Internet of Things (NB-IoT) is 3GPP's cellular technology designed for narrow-band and Low-Power Wide Area Network (LPWN). NB-IoT provides deep indoor coverage for thousands of low-data-rate and low-powered devices. Coverage enhancement for devices in weak coverage condition is enabled by having signal repetitions over extended period of time in order to boost the signal quality. Performance gain from repetitions of signals is limited by channel estimation quality. In this paper we analyze impact of channel coherence time on the uplink coverage. In addition to analytical performance bound and simulation results, we also present coverage performance results from practical measurements using a NB-IoT prototype. It is reported how the NB-IoT coverage improvement is limited by the channel estimation quality and coherence time of the channel. Narrowband Internet of Things (NB-IoT) is a new radio access technology, recently standardized in 3GPP to enable support for IoT devices. NB-IoT offers a range of flexible deployment options and provides improved coverage and support for a massive number of devices within a cell. In this paper, we provide a detailed evaluation of the coverage performance of NBIoT and show that it achieves a coverage enhancement of up to 20 dB when compared with existing LTE technology.