Making Cell Signals, Emergency Band Emissions Cohabitate

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In the state of Washington, an effort to ensure cell phone waves and emergency radio band waves can exist and work clearly in the same spectrum without interference is wrapping up.  The work was fraught with complications that ranged across jurisdictions and even international borders, according to WaTech, a government-spawned technology services agency.

Michael Marusich, the state’s Chief Information Officer coordinated efforts between wireless phone companies, police, fire, search and rescue and other entities of the federal government and state agencies that rely on radios for emergency communication in the field. “It’s like changing a jet engine in flight. You can’t interfere with normal operations, some of which are life-critical for public safety,” Marusich said.

Marusich points to an incident in California that started it all, when a house was burning just two blocks away from a fire station but the emergency radio dispatcher could not alert the firefighters because of interference. When the fire department didn’t show up, people at the scene ran down to the fire station to get help. Later, it was determined that the signal from a cell tower across the street from the fire station overpowered the two-way radio signal to the fire station.  

The problem was this, according to Marusich: Cell phones and public safety radio channels share the 800 MHz band.  Even though cell phone towers are usually placed at lower elevations and emergency radio towers usually located on hills and mountaintops, separating the signals became an issue due to the growing bombardment of cellular use.

In 2004, the FCC began working with carrier Nextel (now Sprint) on a solution: Move the cellular communications to the upper end of the band and move public safety communications to the lower end. Nextel, one of the major carriers that used the shared 800 MHz frequency and cause for some of the interference, agreed to pay the bulk of the costs associated with the shuffle.

For some states, the job of re-banding would be easy, the WaTech study reported. For Washington, which shares borders with Canada and two states, the work would be more of a challenge. Marusich said the re-banding had to be done gradually so that the reassigned frequencies on the spectrum did not interfere with other frequencies in use.

Total costs for the Washington efforts to date are approaching around $23 million. As the project winds down, Marusich is reconciling expenditures to pass along for federal government approval and Sprint‘s reimbursement. He said overall cooperation between most of the impacted entities was “exceptional,” with many in operational support of each other.

The project closes out for Washington at the end of June. Some other states, principally those along the border with Mexico, are still engaged in the re-banding effort, Marusich said.  

June 28, 2018        

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