Extreme Coverage in 5G Narrowband IoT: a LUT-based Strategy to Optimize Shared Channels

E. LUJÁN; J.A. ZULOAGA MELLINO; A. D. OTERO; L. REY VEGA; C. G. GALARZA; E. E. MOCSKOS

IEEE Internet of Things Journal

IEEE

Lugar: New York; Año: 2019 vol. 7 p. 2129 - 2136

One of the main challenges in IoT is providingcommunication support to an increasing number of connecteddevices. In recent years, narrowband radio technology hasemerged to address this situation: Narrowband Internet of Things(NB-IoT), which is now part of 5G. Supporting massive con-nectivity becomes particularly demanding in extreme coveragescenarios such as underground or deep inside buildings sites.We propose a novel strategy for these situations focused onoptimizing NB-IoT shared channels through the selection oflink parameters: modulation and coding scheme, as well as thenumber of repetitions. These parameters are established by thebase station (BS) for each block transmitted until reaching atarget block error rate (BLERt ). A wrong selection of thesemagnitudes leads to radio resource waste and a decrease inthe number of possible concurrent connections. Specifically, ourstrategy is based on a look-up table (LUT) scheme which isused for rapidly delivering the optimal link parameters given atarget QoS. To validate our proposal, we compare with alternativestrategies using an open source NB-IoT uplink simulator. Theexperiments are based on transmitting blocks of 256 bits usingan AWGN channel over the NPUSCH. Results show that, especiallyunder extreme conditions, only a few options for link param-eters are available, favoring robustness against measurementuncertainties. Our strategy minimizes resource usage in allscenarios of acknowledged mode and remarkably reduces lossesin the unacknowledged mode, presenting also substantial gains inperformance. We expect to influence future BS software designand implementation, favoring connection support under extremeenvironments.