When the south tower of Manhattan’s World Trade Center col­lapsed on Sept. 11, 2001, emer­gency respon­ders out­side the building ordered the fire­fighters within to evac­uate. Many did not receive the message.

As is often the case in emer­gency sit­u­a­tions, the com­mu­ni­ca­tion took place almost entirely over radio waves. According to the 9/​11 Com­mis­sion Act of 2007, three things likely kept the fire­fighters from hearing the order: They were either off-​​duty res­cuers on-​​scene without a radio, the radio channel they were using was over­whelmed, or they were using a dif­ferent channel entirely.

In the after­math of that and other tragic events, like Hur­ri­cane Kat­rina, the fed­eral gov­ern­ment has issued a call to iden­tify more use­able space on the radio spec­trum, to deal with the issue of over­whelmed chan­nels. New sys­tems allowing users to com­mu­ni­cate across chan­nels have popped up, forcing safety workers to replace their entire arsenal of radios. Now, a decade after the World Trade Center attacks, bil­lions of dol­lars have been spent but experts say the spec­trum is still maxed out and those new radio devices still cost thou­sands of dol­lars each.

A group of recent grad­u­ates from Northeastern’s Depart­ment of Elec­trical and Com­puter Engi­neering decided to tackle the latter issue in a simple, inex­pen­sive, and user-​​friendly way for their senior cap­stone project. Their solution—called Inter­op­er­able Com­mu­ni­ca­tion Device, or ICD—allows two-​​way radio users to com­mu­ni­cate across chan­nels without updating any hard­ware, according to team member Richard Obermeier.

Along with their team mem­bers, Richard Ober­meier, left, and Justin White devel­oped the Inter­op­er­able Com­mu­ni­ca­tion Device for their senior cap­stone project. Photo by David Potter.

Unlike a stan­dard two-​​way radio, a software-​​defined radio allows pro­gram­mers to define its capa­bil­i­ties using nothing but code. The group of stu­dents, led by team member Fer­nando Quivira, pro­grammed one of these to func­tion on mul­tiple radio fre­quen­cies and inte­grated it into the com­mu­ni­ca­tions chain.

First, the trans­mit­ting radio uses one fre­quency to send a mes­sage to the software-​​defined radio. The SDR then recon­fig­ures the code embedded in that mes­sage to be com­pat­ible with another fre­quency. Finally, the SDR sends the new mes­sage code to the receiver’s radio on this new wave.

Team member Justin White devel­oped a straight­for­ward user inter­face, which dis­patchers at safety head­quar­ters like police and fire sta­tions could use to con­nect radio users on dif­ferent fre­quen­cies. The dis­patcher would use a simple drag-​​and-​​drop method to link two or more users in a “chat room.” Any radios in the chat room can com­mu­ni­cate via the software-​​defined radio as described above. “The drag and drop func­tion is like turning the knob on your car radio,” said Obermeier.

While the system requires opti­miza­tion, it is already in working order, he said, and could be adopted by safety offi­cers around the country for pen­nies on the dollar com­pared to sim­ilar devices already on the market.