Responder with radio (L3Harris)

NIST prototypes tech that bridges LMR and wireless broadband networks

Many of the country’s 4.6 million public safety workers still use traditional analog radios, in part because of the high cost of switching to digital equipment and the newer systems’ slow adoption of familiar “push to talk” features on which responders depend. 

Now, engineers at the National Institute of Standards and Technology have built a low-cost computer system that connects older public safety radios with the latest wireless communications networks. The prototype system could help public safety agencies more easily integrate their radio systems into broadband networks supporting voice, text, instant messages, video and data transmission.

The NIST prototype connects analog land mobile radio (LMR) handsets and towers with an LTE server that handles operations inside a broadband network. This Mission Critical Push-to-Talk system features:

  • Software-defined radios that interact with the LMR signal interfaces and feed that data into the next unit.
  • An open-source software environment for managing software radio, which handles digital signal processing.
  • A user interface for LTE handsets, which allows LMR radio users to talk to LTE network users like they’re both on the same push-to-talk network.

The physical equipment includes a computer with an internet connection to the LTE system, suitable software and an antenna. The entire setup is about the size of a video game console plus a laptop or desktop computer, NIST officials said in an April 12 news release

NIST wanted to be sure the system was robust, inexpensive and that it conformed to existing and future standards.

The NIST system costs less than existing industry and government efforts to bridge radio and cellphone networks.

“There isn’t a commercial option that compares to what we are developing,” NIST Engineer Jordan O’Dell said. “The goal here is to create a prototype and accelerate technology development in industry that will fill a significant gap.”

Currently, bridging radio and cell networks requires a radio system that supports the Project 25 Inter-Radio Frequency Subsystem Interface, which can be too expensive for many public safety agencies to buy or retrofit. Another option that provides a bridge between radio handsets and the broadband network requires investing in dedicated “donor” radios and interfaces.

“We want public safety agencies to have a very inexpensive option that can interface with old technology when the other options are out of reach,” O’Dell said.

NIST researchers plan to improve the interface to the broadband network, link to additional types of radios and publicly release all capabilities as open source. 

Read the full NIST paper here.

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