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Innovative Research Helps Emergency Responders Better Communicate While Indoors

July 31, 2015 by NTIA

Diagram of signal strength along a walk route

These diagrams illustrate the results of measurements of signal strength along one walk route. On the left are the results of when signals are being transmitted only by the cell tower located two km from the test site. On the right are the results of when transmissions are supplemented by in-building systems. The benefits of supplemental cells are easily seen by comparing the colors between the left and right diagrams with red showing poor coverage and blue showing good coverage.

 

Nearly everyone is familiar with the need to step outside a building to complete a wireless call. Modern building materials, such as aluminum, steel and even specially-coated window glass, significantly reduce or even block wireless signals

While it might be inconvenient for your average mobile device user, it could become a matter of life or death for an emergency first responder. Police officers and firefighters cannot stop what they are doing to leave a building in order to communicate during a time of crisis.

As part of its mission to improve communications for public safety, the First Responder Network Authority (FirstNet), an independent entity within the Commerce Department’s National Telecommunications and Information Administration (NTIA),identified improved in-building communications as a critical need for first responders and a required component of the nationwide public safety broadband network it’s been tasked with deploying.

Providing reliable coverage indoors is a long-standing challenge. The Institute for Telecommunication Sciences (ITS), NTIA’s research laboratory in Boulder, Colo., has been researching in-building communications for many years, independently and as part of its Public Safety Communications Research (PSCR) partnership with Commerce’s National Institute of Standards and Technology. Today, ITS released a new report that describes the results of experiments conducted to investigate both the in-building coverage characteristics of future public safety mobile networks and ways to improve performance in such environments.

This research not only can be used to help first responders better communicate during emergencies, but it also may help spur innovation in commercial wireless networks also interested in enhancing indoor coverage.

This research, sponsored by the Department of Homeland Security, involved a team of researchers led by ITS and the University of Colorado at Boulder that developed experimental techniques to characterize and improve in-building communications with and without supplemental radio transmitters. The team targeted the cellular technology envisioned by FirstNet—Long Term Evolution (LTE) operating in public safety frequency bands. LTE is the wireless technology used in 4G smart phones that allows for much faster transfers of data.

Using a backpack mounted measurement system, ITS researchers collected two independent LTE data streams while walking through multiple levels of two buildings—modeling the path that a first responder might take in response to an incident. The researchers found that to achieve reliable coverage, transmissions from the cell tower needed to be supplemented. Three different methods to improve in-building coverage were tested: a portable base station commonly referred to as a cell on wheels (COW), a small cell using standalone antennas that bring the network closer to the user, and a small cell using a distributed antenna system, which is a network of low-power cell antennas often used indoors to boost coverage.

The researchers were able to improve cell coverage with the help of these supplemental systems. However even with better coverage, data transfers were still slow in some cases due to the challenge of coordinating all the systems. Peak performance requires both adequate coverage and optimization of the network to ensure the smooth transfer of data or calls from a wireless device.

This report provides preliminary data that can be used to begin effective planning of in-building public safety LTE communications. It also identifies additional research needed to reliably predict in-building coverage, and points to the need to enhance coordination of all aspect of a network. We look forward to continuing to work on this important issue with FirstNet and PSCR as we seek to provide public safety officials with the 21st century tools they need to help save lives.