Chelsea Greene is an Electronics Engineer with the Public Safety Communications Research (PSCR) Division and has been with NIST since 2018. In this role, she contributes to PSCR’s growing Mission Critical Voice (MCV) portfolio, and has recently led research into Transmit Volume Optimization (TVO) in hopes to standardize the devices that first responders need to communicate in emergency scenarios.
PSCR’s communications team interviewed Ms. Greene in honor of National STEM Day to learn more about her accomplishments, what being a woman in STEM means to her, and her hopes for young women interested in math and science.
Can you describe your current role at PSCR and what you're researching?
Chelsea Greene (CG): My background is in electrical engineering and I started working on the MCV team back in 2018. I love MCV’s focus on Quality of Experience (QoE) and making sure that the end user is actually able to do their job. When I first started, I was doing a lot of data collection and device troubleshooting, and I'm a bit spreadsheet obsessed. So, I started developing test cases, and going through all of these different measurements we wanted to do. From there, I'd look at the data and develop different scripts to detect if something was off in our measurements or if something was weird in the data, which turned into this focus on the quality of our measurements, and how we can make sure that we're doing things in a consistent way.
One major thing we've learned is that the volume settings of the radios, or whatever push-to-talk device a first responder is using, can actually impact the results when we're performing measurements. If someone is just screaming into a radio, it's not going to sound great on the other side. But if you're too quiet, you won't be able to get your message across. The project that we just wrapped up was started before the pandemic, and focuses on Transmit Volume Optimization (TVO). TVO is the calibration step we run before taking other measurements. First, we develop a measurement that, depending on the transmit volume level, shows the effects of distortion caused by that volume setting. Then, we use a tool that runs through a range of transmit volumes. Using that information, we can scan through the data and compare the results of varying volumes. By doing this, we can determine a range of values that aid in selecting an optimal value for the end user. The end user can then use that same setting throughout all of their testing so they won’t see any variation or uncertainty in their results.
How does this research fit into the rest of the Mission Critical Voice portfolio?
CG: The MCV portfolio’s main focus is on Quality of Experience (QoE) measurements whereas a lot of industry measurements are based on quality of service. They'll measure something and say, okay, we got the signal and stop there. Since the focus of MCV is QoE, we're really looking at how the end user is experiencing a system. Is there a delay? What’s the mouth-to-ear latency? We look at a lot of measurements, and the heart of many of them is intelligibility. If you can't understand what's actually coming through, it defeats the whole point of using these devices. We want to make sure that we're actually measuring things that have real world practicality.
I imagine there are hurdles to exploring this type of work because of the public safety context.
CG: Yeah. The challenge is when you have first responders in emergency situations, you can't expect everyone to be talking perfectly. You can’t tell people “okay, talk at negative 12.” It's strange because when we’re calibrating the measurements, we know that things are consistent. And it’s eye opening how different devices behave very differently, depending on the volume.
Of course, being able to understand exactly what's being said and going on is critical in these scenarios.
CG: Exactly. If [a first responder is] missing even one word, it could just be the word that removes all the context.
Do you think there's a chance that in the future this could be applied to civilian technology, like cell phones?
CG: I could definitely see it happening, just because now there are first responders that are using these push-to-talk devices for general use cases. So in theory, the same measurements could apply to any communication system. The newer measurement that we're working on now, the probability of successful delivery, is measuring the probability of successful delivery of a message that's five seconds long, 10 seconds long, etc. and chopping it off to see how much of the sentence you can hear.
When did you first determine you were interested in this type of work?
CG: I graduated in 2017 and started working in power engineering; I didn't really love it because I did the same thing every day. In the past, I had an assistive technology internship where I was working mostly with handheld devices in a theme park, so it was a challenging environment. When I saw the opportunities with PSCR, specifically with MCV, I was really excited to work on tech that does not function in a typical environment. And the work being done with PSCR is just so important and impactful, I was really interested in working on something that would be helpful. That really attracted me, and the PSCR mission was really interesting to me. Plus there are a lot of great people.
Absolutely, your work environment is so important.
CG: Yeah, I think it's great that everyone I've met at PSCR is so dedicated to the mission. I think that's why we've been successful. I remember coming in for my interview, and number one, everyone was terrifyingly friendly. And I thought “this is suspicious.” Because everyone was so excited about what they were working on. And that passion is so contagious; you're around a bunch of people who really care about what they're doing. And that's rare.
It really is!
CG: There’s a lot of collaboration, too. No one is that person who just sits in their box and does that thing over there—everyone really works together. I think that that really contributes to making a good workplace because everyone's very open about concerns or ideas. And I think that that makes the final product better of what we're doing.
Has this research been field tested with first responders yet?
CG: Right now we have a big effort to push things into a different programming language that's free because the one that it was developed in is not. So, we're working with a test system that is currently being used by The First Responder Network Authority (FirstNet) to measure FirstNet AT&T devices to drive future reinvestment back into the network for first responders. We're really trying to make this more usable; we're trying to make our system something that’s a little more user friendly for someone who doesn't have a strong communications electronics background. I think there's been a lot of effort to make things easier to run. That’s the main priority for the rest of the program.
Is this the work that you're most proud of doing since you’ve been at PSCR?
CG: I'm definitely a little biased with this one. I got the chance to lead the project, which was cool, and I began wondering, “what are we going to do about this?” And I got to run with it. That was exciting, because I like to look at our data a bit obsessively and pick out patterns, and now they’re actually being practically used in something. It's cool to see how far things have come just because when I was first looking at it, I noticed this weirdness and now it's turned into a real project.
That's awesome. So, who are some of your role models in STEM?
CG: I had one mentor in college who was really great. One thing I really loved was that she was also an electrical engineer and worked for the government and she always said it's one of the best things you can do. You get this feeling you have to be a certain way when you're a woman in engineering… But she wore lots of bright pinks which inspired me to be louder. It was great having her as my mentor. Before that was my tech art teacher in middle and high school, she was just fantastic. She was the first woman I encountered who spoke to me about engineering concepts and she was super supportive- she would just hand me all these things like drafting supplies from her house to play with on my own, that was cool.
Mentors like that are so special!
CG: Something I noticed when I first came into PSCR is the amount of women in engineering that work here. It’s very exciting for me–being able to work with so many female engineers in leadership positions is amazing. At the end of the day, once you find a job that you can just be yourself at, it really helps—not only just mental health-wise but you become a better version of yourself, a happier version of yourself, and then you can do better work and contribute all of these great ideas.
And now you've got an opportunity to be that spark of inspiration for other young women too. Do you have any advice for young women who are interested in STEM?
CG: I used to tone myself down, especially when I figured out there's not many women in STEM classes. At first, I would mute myself a little bit and stick to myself so I got quieter, I stopped dressing in these obnoxious colors and just tried to not stand out, really. I didn't want that added attention—I just wanted to learn. I think the biggest lesson I learned was don't try to fit into that box because whatever you pull out of your background that you might not want to bring up at work are the things that help you grow and be better or contribute ideas. I'm a disabled woman in STEM, and I didn't know anyone else with a disability in my courses early on which was sometimes daunting. But I'm so used to problem solving, I'm so used to just jumping into that mode. You don't have to be the person who's the best at math, you don't have to be the person who's the best at all these very specific things. You just have to be the person that likes to solve stuff, who’s able to look at something and say, okay, that's a problem, and I want to work on it. That's enough.