The unique feature set of LTE-M
LTE-M is sometimes also called the new GSM for M2M/IoT. Beside global coverage and mobility, LTE-M also supports VoLTE with device costs comparable to GSM. This makes it very attractive for a several IoT applications, including devices with emergency call functions such as child trackers. Moreover, LTE-M can reduce battery consumption and improve indoor coverage. It was initially limited to a bandwidth of 1.4 MHz (Cat M1) and some coverage enhancements feature like frequency hopping and subframe repetitions (CE modes A/B). In order to meet the requirement for more data throughput in Release 14, the new Cat M2 was introduced allowing the optional use of 5 MHz bandwidth. A battery life of more than 10 years calls for specific power saving features like PSM, eDRX or release assistance indication (RAI). Moreover, the introduction of LTE-M and NB-IoT required an optimized core architecture to be specified that allows, for example, the …