U.S. presidential nominating conventions used to be criticized as "smoke-filled rooms" because of the cigars that party politicians smoked while they decided on a candidate. Now the delegates are toting Blackberries instead of Cohibas, and the air is thick with radio signals.

Gather about 20,000 of the most talkative people in the world in one giant room, add support staff, then invite dozens of TV broadcasters and countless radio, newspaper and online news operations, and you have a recipe for wireless havoc. Reining it in is the job of Louis Libin, a telecommunications and broadcasting engineer who has helped set up networks at conventions dating all the way back to 1988.

As he does every four years, Libin this year is working on both the Democratic National Convention beginning Aug. 25 in Denver and the Republican National Convention next month in Minneapolis. In both cities, planners have been working for nearly a year to get ready. Setting up the wired networks is mostly a matter of logistics, he said, so wireless takes up most of his time. Meanwhile, Libin is also CEO of unified communications vendor PhoneFusion.

"When we have to begin to take a spectrum that's already crowded and now overlay all new services on top of that, that is the big unknown," Libin said. "The wireless side is the biggest deal, because there's no script you could read from."

For example, the Pepsi Center, where the Democratic convention will take place, can hold about 21,000 people. Libin estimated half the convention-goers will be carrying two cell phones. There will also be 3,000 to 4,000 walkie-talkies, hundreds of wireless microphones, and wireless cameras for as many as 50 TV outlets, he estimated. Plus, about thirty government agencies will be there and need to communicate. In addition to setting aside frequencies for all those, the spectrum plan can't interfere with existing applications such as TV and local public safety, he explained.

The volume of calls at the Pepsi Center could be five to 10 times that of an average hockey game, estimated John Niedermaier, vice president and general manager of ADC's in-building wireless solutions division. And use of cellular data, a mainstream application for the first time at this year's conventions, could add significantly to the demand, he said. To prevent poor reception and dropped calls, ADC is supplying additional in-building devices in all the Denver venues, plus at Denver International Airport.

The biggest danger is interference among various wireless devices, according to Libin. For example, if the wrong user ended up on the frequency set aside for a TV crew, it could suddenly shut down a live news report from the floor. Many of the microphones and cameras will be wireless, and most are designed to use the same radio bands, Libin said. Although a microphone may only have to reach a camera ten feet away, it will broadcast to its full range anyway, all across the hall. Meanwhile, as government officials and their staffs converge on the site from around the country, each with their own walkie-talkies, their transmissions could clash.