"It was a greenfield design, but a ship changes over time," he says. So the wireless team visited it during construction to test out how well the access points worked on site. Sometimes the optimal location for an access point was unsuitable for architectural reasons, requiring relocation and more tweaking, he says. "Typically we have to work around the design requirements of the ship," he says.

One challenge was that for the many types of network users -- various classes of crew and passenger voice, Internet access, and data -- designers thought they would need 13 different SSIDs for the network. "That's not necessarily within the realm of best practices," Schmidt says. They managed to get that number down to five and resorted to using multiple virtual LANs over some of them. Cisco wireless control points impose priority for voice and video access over data, Martin says.

Passengers can rent pairs of iPhones on board that are loaded with ship-specific applications. For instance, there's a location-finding app that maps where the partner phone is so passengers can easily track traveling companions. Passengers can also rent they attach to their children. When the children move, the tags tell an iPhone app where they've gone and it's displayed on the phone's screen. The phones also display daily shipboard activities.

The iPhones are also used for passengers' shipboard voice communications. (The crew uses Cisco mobile VoIP phones.) If passengers want to call to shore, they can do so either on their cell phones or with the wired VoIP phones in their cabins. GSM cell calls link either directly to cell towers ashore when the ship is in range, or through a shipboard cell tower that kicks in when the ship is out of range of a cell tower on shore. The cell tower is managed by AT&T's Wireless Maritime Services and bounces signals off to reach a WMS ground station. Passenger phone calls from their cabins travel via satellite to Royal Caribbean's headquarters network on land, then out to the public phone network.