As I browsed the Exhibit Hall and lingered outside professional development sessions at APCO 2013, I found a consistent theme in the conversations I overheard and those I entered myself. Most communication center managers had come to APCO to discover the latest products and the exhibitors did not disappoint. Although there was a lot of glitz and glamour, hardware and software of the future and tons of talk about high-end technological progress, many of the managers had no idea what they were looking at or what all the tech-babble even meant.
Covia Labs, CEO David Kahn summed it up perfectly during our interview when he explained there were a lot of companies producing products designed to make the telecommunicators adjust to the system and not the other way around. He expressed concern that the needs of the telecommunicators were being lost in the process of the next great thing. I would agree based on the lost look in the eyes of so many attendees as they stood in booths being told what that manufacturer’s product could do.
After a conversation with a former co-worker of mine who has been tasked with assisting her major metropolitan communications center into the next generation, I realized somehow we’ve missed a step in this curriculum of new technology: the basics. After speaking with numerous people, research and attending sessions, I present a two-part column on Radio 101.
All wireless technologies use radio waves to communicate. Radio waves transmit sound and data invisibly through the air. To use radio waves, there needs to be a transmitter and a receiver. I won’t get into all the technological terms regarding the various parts of equipment but if you’re interested ask your IT personnel. I’m sure they’d be thrilled that you care. Basically, the transmitter takes the message (voice, picture, text, etc) and encodes it into a wave. Modulation is used to encode the message and our systems use frequency modulation to accomplish this. Then, this wave is sent out to a receiver that decodes it by demodulating and then amplifying the message. Both sites use antennae (a metal stick that launches and catches waves) to facilitate this process. A wireless device (such as a cell phone) has the transmitter and receiver inside and can use both simultaneously. Radio towers (antennae) are generally throughout the user area and many times on top of the communications building.
One characteristic of the wave is its frequency. The frequency is the number of times the wave oscillates up and down per second. A cycle per second is called a hertz (Hz). Kilohertz (KHz) is thousands of hertz and megahertz (MHz) is millions of hertz. An 800 MHz radio is broadcasting at 800,000,000 cycles per second. As the frequency goes up, the wavelength gets shorter. The radio spectrum is the radio frequency (RF) portion of the electromagnetic spectrum. This is a chart that shows what bands (portions of the spectrum) each wireless technology gets to transmit on. Everything from AM/FM radio, to television stations to individual cell phone carriers to police radios is assigned to a band. A bandwidth is how much space your frequency takes up.
Analog vs. Digital
Television and cell phones have already switched completely from analog to digital radio waves. Police communication centers throughout the country are a mix of analog and digital. Analog is a continuing stream of electrical signals that vary in intensity over time. Analog signals use modulation and are easily disturbed by environmental interference such as storms. A benefit of analog is that only a portion of the signal is disturbed so partial transmissions can be heard. Digital, on the other hand, changes information into a mathematical code which is sent in non-continuous block segments. These pulses of information are less disturbed by environmental factors but if a segment is disturbed, it is lost in its entirety. Because digital can be confused by background noise, many public safety communications professionals still believe that the “old way” of analog is more appropriate. The good thing about digital is that companies are still researching and developing ways to improve it. Hopefully, one day we will have the best of both worlds and the days of garbled and lost transmissions will be over.
Wide Band vs. Narrow Band
The radio spectrum is a finite resource. There is only so much room so frequencies must be regulated to be efficient to prevent interference. Essentially a wide band transmission takes up more room on the frequency. Components of the transmitter and receiver can make transmissions take up less room or narrowband. An advantage of narrow banding is more radios can co-exist on the same frequencies without interference while a disadvantage is that data-speed is decreased. The Federal Communications Commission (FCC) has required implementation of narrow banding. Agencies were required to drop from using 25 KHz to 12.5 KHz during Phase I. By 2016, Phase II will be implemented requiring the bands be narrowed to 6.25 KHz. Many think this phase will be re-assessed and possibly eliminated.
The FCC regulates interstate and international communications by radio, television, wire, satellite and cable in all 50 states, the District of Columbia and U.S. territories. It was established by the Communications Act of 1934 and operates as an independent U.S. government agency overseen by Congress. Regulatory responsibility for the radio spectrum is divided between the FCC and the National Telecommunications and Information Administration (NTIA). Non-federal use is regulated by the FCC while the NTIA regulates federal use. Allocation of space on the radio spectrum for non-federal public safety is the responsibility of the Office of Engineering and Technology (OET) a division of the FCC. The Public Safety and Homeland Security Bureau (PSHSB) is the division that develops, recommends and administers the FCC’s policies that pertain to public safety communication’s issues. The FCC has numerous rules that must be followed and this agency has the power to impose fines and shut down use. Public safety communication centers must have an FCC-issued license to broadcast. An agency cannot just apply to the FCC for this license but instead must use an approved licensing service, such as APCO. Part of this process is to have an appropriate frequency chosen which requires a frequency coordinator. APCO offers this management service as well. Violation of FCC law, even if it’s un-willful such as letting a license lapse, will result in penalties.
I hope this has helped clear up some basic questions about frequencies and how the radio system that we use day-in-and-day-out works. In my next column, we’ll go over legacy vs. P25, NG9-11, FirstNet and other acronym heavy terms such as LMR and LTE. Until then, be safe.