There are no network towers in the middle of oceans. There are no phone lines trailing the international cruise ships that dot large waterways. But there are thousands of tourists making long-distance cruises every year. These travelers, like the hundreds of cruise line staffers onboard, have friends and family to call and jobs to check on, creating a need for more ways to make those important connections. In working with one of its customers, Telecom Italia Mobile (TIM) recognized this and came to Andrew, the wireless division of CommScope, Inc. to see what could be done.
"We saw that there were a lot of people on these cruise ships, thousands at a time usually, who are on vacation but want to stay in close touch with family and friends," said TIM's special projects leader. "We knew that providing our customers with wireless service would make them happy, provide us with a new revenue stream, and benefit the cruise lines, too."
Lack of Wireless Communication Means Lack of Convenience, Homesickness
Communications between vessels and the mainland are generally accomplished via satellite connections, but this means passengers must use, for additional costs and with less convenience, the ship's wired phones while onboard. In those scenarios, passengers are unable to receive wireless calls, nor can they simply use their mobile devices on deck or in their rooms to check or send messages.
Cruise ship workers also experience frustration at the lack of easy communications while at sea. A recent survey of 600 cruise workers by Navitas Telecom revealed that 90 percent have experienced problems in the past keeping in touch with friends and family [1]. Almost half off these workers ranked communications services as a top priority when choosing the company for which to work. Employees abandoning ship while at sea because they miss their families too much is not unusual. Employee retention is a common difficulty in this industry for this very reason.
Unique Locations Demand Tailor-Made Solutions
To alleviate these connectivity problems, TIM decided the cruise ship's satellite system could be used to backhaul wireless communications to the mainland, which would tap into TIM's core GSM network. But to ensure connectivity via handhelds, network equipment would need to be installed onboard, which would spread wireless signals across the ship's decks and down its many corridors. This system would have to operate mindful of the ship's unique power supply limitations, equipment installation restrictions, and aesthetic requirement.
Andrew product and systems engineers worked with TIM radio planning engineers to devise how such a system could work. They knew Andrew's ION-B radio-over-fiber distributed antenna system was a good place to start, as its remote units could be connected in a low power environment, and it could support multiple frequency bands. This meant more passengers and the ship's crew would be able to access the system. In application, the ION-B system that the engineers devised works through small, unobtrusive antennas distributed throughout the vessel, which communicate with passengers' handheld devices. The antennas are linked to remote electronic units, which communicate via fiber optic cables to a master unit, which transmits and receives signals through the ship's tracked microwave antenna to a satellite in the sky. The satellite relays signals to and from TIM's satellite gateway in Italy, which ultimately interfaces into TIM's GSM wireless network.
"It wasn't a 'go install some antennas and cable and be done with it' type of project," said Marianna Fabbri, product line manager, ION-B, Andrew. "The maze-like design of a cruise ship made the system design challenging, the fact that you are using a satellite gateway added complexity, and the whole project made for a unique RF engineering challenge. Thanks to great teamwork between our engineers and TIM's, we created a sound technological solution."
Bringing a GSM Network Onboard Requires Deep Understanding
One of the most challenging parts of expanding wireless coverage on a cruise ship is dealing with the portion of the GSM core network that is installed onboard. In a typical GSM network on a cruise ship, the BSS (base station subsystem) system, which is composed of BTSs (base transceiver stations) and BSCs (base station controllers), is connected to the MSC (mobile switching center) via cable (interface A). In this system, there is a special platform called the NIB (network in a box), which is as big as a PC tower and includes the complete BSS system and NSS (network and switching subsystem) functionalities. The interface A (between the BSS and MSC) is carried on a satellite link.
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The NIB has TRAU (transcoding and rate adaptation unit) and MSC functionalities and also a database HLR (home location register). This allows for defining three different groups of users:
- Public: user registered only inside public HLR of GSM network, not allowed to access any local service onboard, with calls passing through GSM PLMN
- Private: user registered only inside NIB HLR for local services purposes " wireless PBX - with calls not passing through satellite link
- Hybrid: user registered both inside NIB HLR and PLMN HLR, with calls allowed to pass through both local PBX and PSTN or PLMN
