Misunderstood When it Matters Most – Spirent Finds LTE Devices for Public Safety Have Room for Improvement
Holmdel, NJ, September 25, 2019 –(LSE:SPT), a leading provider of test, assurance, and analytics solutions for next-generation devices and networks, today announced critical findings from its LTE Device Speech Intelligibility Benchmark Analysis. The findings in the report show that phrase misunderstandings can occur in mission-critical communications scenarios up to almost 50 percent of the time, even when using devices that are marketed specifically for use by the public safety community.
As public safety networks transition to PS-LTE (Public Safety LTE), more handsets are entering the market. Spirent conducted testing of a representative sample of these handsets in its Maryland-based Performance Center - a world-class testing facility that specializes in evaluating the communications performance of voice, video and data devices. As part of the test process, the company evaluated speech intelligibility in four commercially-available devices. Testing emulated use within a quiet environment, followed by six emulated first-responder noise environments including a nightclub, emergency siren and a fire-rescue situation utilizing a saw.
Spirent’s whitepaper, “”, offers a look into anonymized results of the benchmark testing, which revealed:
The top-performing device outperformed the others tested by at least a six-to-one margin in certain emulated environments;
No device proved perfect – intelligibility failure rates ranged from 1% to 49%, depending on the environment;
Great performance in one environment did not necessarily correlate with similar performance in other emulations; and
In some cases, consumer-grade devices outperformed devices purpose-built for PS-LTE use.
“Our testing looked at certain devices through the lens of how well they were able to transmit the essentials of speech while suppressing most background noise, because that’s where the largest performance gaps emerge in public safety applications,” said Vice-President of Product Marketing at Spirent, Saul Einbinder. “The significant performance discrepancies we uncovered indicate that device makers must further re-evaluate designs and components to assure performance on the mission-critical LTE networks being rolled out around the world.”
Previous testing of speech intelligibility was largely subjective and based on human responses, but Spirent applied a new algorithm designed by the U.S. National Telecommunications and Information Administration (NTIA). The ABC-MRT16 algorithm models the human auditory system and, in conjunction with a head and torso simulator in a 3D sound reproduction lab with automated testing, was used to assess over 80,000 distinct speech points to determine the quality of speech intelligibility. Spirent is the first testing and assurance provider to offer a speech intelligibility service designed to help mobile operators determine which devices will work best on mission-critical networks, while giving device developers and manufacturers guidance on how they can improve performance in noisy real-world environments.
"Assuring high-quality speech intelligibility during mission-critical operations is essential," said Ken Rehbehn, Directing Analyst at IHS Markit, and himself a former 911 dispatcher and current firefighter/EMT in Montgomery County, MD. "Distorted communications reduces incident command effectiveness and, in the extreme, can lead to career-ending injury or line-of-duty death. Device vendors serving the public safety market have a profound duty to do everything possible to maximize speech intelligibility.”
Achieving a higher bar for device performance in public safety environments begins in the development process. Software algorithms determine which parts of the audio are actually speech, and yet still allow some background sounds to be transmitted to help the listener better understand situational context. Spirent has found that independently testing elements of the handset voice path, together with fine-tuning of microphone circuitry and audio processing software, are some of the ways device designs can be enhanced to better accommodate grueling first responder scenarios. Testing for a range of common public safety scenarios is critical to establishing that a device will perform every time a first responder relies on it.
“While our testing found substantial room for improvement in some cases, the good news is that there is a pathway to better performance,” said Einbinder. “This is absolutely a solvable problem. First responders need to trust that the devices they use for lifesaving measures will perform when it matters most, and we believe pinpointing performance challenges that exist early in the development process will help the entire industry take a major step toward that goal.”