A classification back-off method for capacity optimization in NB-IOT random access

Narrowband Internet of Things (NB-IOT), one of the Low Power Wide Area (LPWA) Networks, can be defined as a communication technology under the licensed spectrum. There are four characteristics of NB-IOT which include wide coverage, lower cost, long battery life-time, support of a massive number of devices in a cell. We mainly discuss the access capacity optimization when a large number of devices are accessed in NB-IOT. In this paper, we analyze the random access procedure in detail, combined with two kinds of traffic model proposed by 3rd Generation Partnership Project (3GPP) in order to get a system flow chart. Due to the non-sensitivity of NB-IOT business, we put forward a classification Back-off method to classify different types of devices in the Back-off mechanism. Simulation results have verified the efficacy of our proposed method, showing that the capacity gain, on the basis of an access number of 50 thousands, can be increased by 3%-6%.