| With the development of technology in various fields, it can be predicted that the world will be a world in which all things connected in the future. Machine to machine communication will cover every corner of the world. NB-IoT (Narrow Band IoT) as a new feature introduced by 3GPP R13, has improved indoor coverage, can support of massive number of low throughput devices that can significantly reduce complexity and hence cost. Considering the limited spectrum resources,the communication systems will be deployed in the adjacent spectrum in the same geographical area. Due to the non-ideal characteristics of communication equipment, in the case of small space between two systems, interference caused by adjacent system will reduce the system performance. System coexistence is to improve the spectrum efficiency with the limited loss of system performance. Therefore, to confirm the RF index of NB-IoT which can co-exist with the legacy systems is an urgent problem need to be solved.The theoretical knowledge of NB-IoT system is introduced briefly at first. Then, study the coexistence interference between NB-IoT and other legacy systems in different kinds of scenarios. Considered of the improved indoor coverage of NB-IoT, Building Penetration Loss is proposed to make the system more accurate.In stand-alone scenario, according to the narrowband characteristics of NB-IoT, a new conversion method for ACLR and ACS is proposed.The method takes the number of users and the bandwidth of NB-IoT into account, converts the inputs of ACLR and ACS into the effective ACLR and ACS. In in-band and guard-band scenarios, considering the network deployment of NB-IoT and LTE, the power leakage model is established,based on the power spectral density of two systems. This is the key to evaluate the interference in this two scenarios. System level simulation results show that, under the given NB-IoT system RF index, NB-IoT can coexist with the legacy systems with allowing performance loss. |
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