LTE

NB-IoT field issues often sound very simple at first: the SIM is inserted, the module has signal, why does it still not send data? Or the platform has seen the device online before, so why does it later disappear for a long time? Once you break it apart, the bottleneck is usually somewhere else. Some devices never found a cell they could camp on. Some synchronized to a cell and read system information but never finished random access. Some already established an RRC (Radio Resource Control) connection but got stuck at NAS (Non-Access Stratum) registration or authentication. Others registered successfully but never established a usable bearer, so the application still could not send data.