Fecha de publicación: 26/10/2021 Fuente: Wipo "IOT" The invention relates to the field of communication, in particular to a data transmission method of an NB-IOT end, an NB-IOT chip, equipment, a communication system and a computer readable storage medium. The data transmission method of the NB-IOT end comprises the steps: updating an SINR left threshold value according to connection data of the NB-IOT end and a base station, wherein the connection data comprises whether connection succeeds or not and a measured SINR; when the measured SINR is smaller than the SINR left threshold value, by the NB-IOT end, sending a random access preamble to the base station through a narrowband physical random access channel (NPRACH) with an enhanced coverage level (ECL) as (i+1) for the NB-IOT end to establish connection with the base station; and/or when the measured SINR is greater than the SINR left threshold value, by the NB-IOT end, sending a random access preamble to the base station through the NPRACH with the ECL as i, for the NB-IOT end to establish a connection with the base station. According to the invention, the SINR threshold value is updated based on the measured SINR, so that which ECL is used by the NB-IOT end to access the base station is determined according to the measured SINR and the SINR threshold value, and the problem of long time consumption caused by improper ECL configuration when the NB-IOT accesses the base station is solved.