Prototypes of LTE products that provide full mission-critical-voice functionality could be available for laboratory testing within two years, an official with Public Safety Communications Research (PSCR) testified during a recent hearing on FirstNet oversight conducted by the U.S. House subcommittee on communications and technology.

PSCR Program Manager Dereck Orr cited “significant progress” being made internationally to include public-safety characteristics in LTE communications standards and offered a potential timeline for vendors to develop such products.

“Our expectation, at least from a PSCR perspective, is that—within the next 18 to 24 months—we’d like to start seeing prototypes in our laboratories that display these capabilities, so we can at least start assessing, testing and reiterating on the standards to ensure that these products someday actually do meet the capabilities of the land-mobile-radio systems,” Orr said during the hearing, which was webcast.

Orr said that NPSTC has defined mission-critical voice as having the ability to transmit and receive voice communications in the following seven ways:

• Via push-to-talk functionality;
• With group-call (one-to-many) capability;
• Direct-mode (i.e., peer-to-peer or talkaround, as it is known in the land-mobile-radio industry) communications, so that responders can talk even when network infrastructure is unavailable;
• Full-duplex voice, as with a traditional phone call;
• With caller identification (ID);
• With emergency-alert notification that provides “dogmatic access” to the network for responders in critical situations;
• With sufficient audio quality to allow a voice to be intelligible in the difficult noise environments that first responders encounter.

“The most challenging aspects for mission-critical voice right now are really the top three, which are dealing with push-to-talk capability, group communications and direct mode—device-to-device [communications]—because those aren’t issues that are being dealt with by the commercial community right now,” Orr said.

Orr made the comments in response to a statement by Rep. John Shimkus (R-Ill.), who described mission-critical voice—voice communications used by first responders during emergencies—as “an important aspect of this debate” surrounding the development of FirstNet’s nationwide broadband network.

Although gateway-based solutions and proprietary over-the-top applications exist today, PSCR officials and international counterparts are trying to have standards bodies include these mission-critical-voice characteristics in future releases of the LTE standard. The direct-mode and group-call features are still part of the 3GPP standards body’s Release 12 work for LTE that is expected to be finished during the first half of 2014, according to sources familiar with standards progress. The push-to-talk functionality likely would not be included in the LTE until at least Release 13, according to sources.