The long term evolution (LTE) modem consists of baseband processing and RF parts, which together implement a complete 3GPP LTE release 13 (Rel-13) Cat-M1 and Cat-NB1 and LTE release 14 (Rel-14) Cat-NB1 and Cat-NB2 capable product.

As illustrated in the image below, the following is a part of the LTE modem:

The modem baseband and host processor provide functions for the LTE L1, L2 and L3 (layer 1, 2 and 3 respectively) as well as IP communication layers. Modem peripherals provide hardware services for modem operating system and for modem secure execution environment.

Figure 1. LTE modem within the nRF91
LTE modem within the nRF91

Application and modem domains are interacting through interprocessor communication (IPC) mechanism. LTE modem is accessible to user through the modem API.

The application processor is the master in the system and responsible for starting and stopping of the modem. LTE modem enables the clocks and power required for its own operation. Shared resources, such as e.g. clocks, are handled within the platform and require no user involvement. In cases where a hard fault is detected in the modem, the application domain will perform a hard reset for the modem.

Note: For details regarding the modem API, please refer to nRF Connect SDK document and nRF91 AT Commands, Command Reference Guide document.

Key features of the LTE modem are:

Note: nRF9160 is able to run different modem FW builds that define the final modem feature set in a specific nRF9160 based application.