LTE modem

The nRF9161 SiP contains a Low-Power Wide-Area (LPWA) network processor with dedicated flash/RAM, which controls the radio and baseband hardware components. LTE capabilities are provided by installing Nordic Semiconductor firmware, which complies with 3GPP LTE release 14 Cat-M1 and Cat-NB1/NB2 standards.

The following is an overview of the LTE modem, with a figure showing key components:

• RF transceiver
• Modem baseband (BB)
• Embedded flash/RAM
• LPWA network processor and peripherals

They provide functions for the LTE L1, L2, and L3 (layers 1, 2, and 3 respectively) as well as IP communication layers. Peripherals provide hardware services for the LPWA network processor operating system and secure execution environment.

Figure 1. nRF9161 LTE modem functional overview

Application and LPWA network domains interact through the interprocessor communication (IPC) mechanism. The LTE modem is accessible to users through the modem API.

The application processor is the system master and is responsible for starting and stopping the LTE modem. The LPWA network processor enables the clocks and power required for its own operation. The platform handles shared resources, such as clocks, and does not need user participation. In cases where a hard fault is detected in the modem, the application domain will perform a hard reset of the modem.

The nRF9161 LTE modem feature set depends on the modem firmware version and the application firmware. For more information on the LTE modem API, see nRF Connect SDK API documentation and nRF91 AT Commands.

The key features of the LTE modem are:

• Complete modem with baseband and RF transceiver
• 3GPP release 14 compliant LTE categories:
  • Cat-M1 (eMTC - enhanced machine type communication)
  • Cat-NB1 (NB-IoT - narrowband Internet of things)
  • Cat-NB2 (NB-IoT)
• Power saving modes
• Supports LTE bands from 700 MHz to 2.2 GHz through a single 50 Ω antenna pin
  • ANT antenna pin is DC grounded
• RX sensitivity: -108 dBm for Cat-M1 and -114 dBm for Cat-NB1 and Cat-NB2
  • As defined in 3GPP conformance test specification TS 36.521-1
• 1.8 V MIPI RF Front-End (MIPI RFFE) digital control interface and MAGPIO control interface for external RF applications.
• LTE modem internal ADC that is also used for some AT command interface services, for example, for battery monitoring
• 1.8 V UICC (universal integrated circuit card) interface, based on ISO/IEC 7816-3 and compliant with:
  • UICC (ETSI TS 102 221)
  • eUICC (ETSI TS 103 383)