Global Roaming

Fewer people are opposed to global roaming than to motherhood and apple pie. Yet, technical, business and political realities are making it harder to achieve than the average consumer might expect. The current state of global roaming is reminiscent of someone who has just reached the peak of Mt. Everest. Perhaps the hardest part of the trip is behind them but, if the weather turns, perhaps not.

INCOMPATIBILITIESAdvances in wireless technology form a double-edged sword. Without many of those advances, there would be no phones to roam with, nor any channels for homers, let alone roamers. But with innovations come incompatibilities. The most obvious incompatibilities, those between radio technologies, are the least serious. Many multimode terminals are available, although nobody has yet attempted to cross the CDMA/TDMA tightrope. Some people joke about the 4-pound (2-kilogram) bricks that would result. However, if you take the battery, keyboard, outer shell and display off an existing dual-mode, dual-band phone, there is so little left that it is hard to believe that the size of a triple- or quadruple-mode phone would be a big problem. Certainly, technical and marketing challenges to multimode phones abound, but where markets demand, manufacturers surely will follow.

More insidious incompatibilities occur in the wireless backbone network, most particularly in mobility applications and SS7 signaling. Two successful mobility applications for global roaming exist today: the TIA/EIA-41 standard and the GSM MAP. Not only are the arrangements of bits and bytes used to represent the same concept different, but the concepts used for short messaging, authentication, feature handling and other capabilities are different as well. Even within TIA/EIA-41, compatibility limitations exist. For example, it would be challenging to send a short message to a multimode D-AMPS/CDMA phone due to limitations of the networking protocol. Even locking onto the best local channel would become difficult without more help from the network.

LANGUAGE BARRIERSTo make matters worse, both mobility applications use SS7 to transport and route messages. Here, the global roaming barriers are not between wireless technologies but between the many national variants of SS7, of which ANSI SS7 (used in the United States and Canada) is the most well known. Furthermore, SS7 point codes are limited in scope to a single national network and cannot be used to improve international roaming. The alternative, global title translation, requires significant software development, standardization and network upgrades, including international gateway modifications.

SS7 communications within one national network is much easier than between countries. Today, most global roaming is handled by extending the ANSI SS7 network to other countries.

AMERICAN HERITAGEWireless technologies that were developed in the United States have another hurdle due to their birthplace. The United States has such complex internal issues and such a huge market potential that it was not necessary to consider international roaming. Its largest trading partner, Canada, even has its telecommunications network integrated with the United States. GSM, on the other hand, was developed in Europe to replace a forest of older, incompatible national systems with a single pan-European standard. Global roaming was built in to GSM but is being bolted on to TIA/EIA-41. GSM is having some technical problems adapting to the U.S. telecommunications environment, which is probably the most complex in the world, while TIA standards are having trouble adapting to international roaming.

One major problem from this heritage is the use of a North American phone number to identify mobile phones. The 10-digit MIN does not have to be the same as the phone number but almost always is (in the United States and Canada, at least). Consequently, any MIN that begins with a currently used area code (or a potential area code) cannot be used by international wireless carriers safely to identify their mobiles roaming in the United States. The long-term solution is to migrate to the 15-digit international mobile subscription identity, which already is being used by GSM systems. However, this remains a long-term solution because of the amount of equipment that has to be upgraded to support it.

TEAMWORKBecause of the enormous size of the U.S. telecommunications marketplace, U.S. carriers have been slow to recognize the potential of international roaming. International roaming is difficult to measure when, relatively speaking, it barely exists, and most consumers are unaware of global roaming's availability. However, many organizations finally are charging forward with the roaming issue. Both the CDMA Development Group and the UWCC are encouraging the improvement of international roaming for their respective technologies. The UWCC, which promotes D-AMPS TDMA technology, even is tackling the difficult challenge of interworking with GSM. SS7 network and clearinghouse providers, such as the NACN, BellSouth International and GTE, also are busy signing up international customers, although the networking still has limitations such as the need to allocate ANSI point codes for all international wireless switches.

CTIA was a major force behind the mid 1990s effort to resolve Mexican roaming problems, which stimulated the formation of the International Forum on AMPS Standards and Technology (IFAST) in 1996. This organization (www.ifast.org) is trying to resolve both short-term and long-term international roaming issues. The most immediate need is to ensure that all mobiles have unique MIN codes. Numbers that cannot be confused with those used by North American mobiles (beginning with the digit 0 or 1) are called international roaming MINs and are allocated in blocks of 1million by the IFAST to needy international, data and satellite operators. Another requirement is that every wireless system have a unique system identifier. Where the current allocation is insufficient, IFAST has stepped in to allocate a new block to a country or to a satellite carrier.

Here's a wish list for the future of international roaming:

* Add global title support to all wireless network elements that support international routing of SS7 messages (MSC, HLR, signal transfer point, international gateways).

* Make sure all future standards and wireless equipment can support international mobile subscription identity (IMSI).

* Make the international roaming MINs pool (currently almost half used) lasts long enough to make a smooth transition to IMSI.

* Negotiate some common ground between IS-41 and GSM concepts to make more features work seamlessly across technology boundaries.

* Educate consumers that international roaming works, and that it is often one of the easiest and cheapest ways to call home.

* Fix SS7 so that international messaging is just as easy as national messaging. (OK, so maybe this one is a dream.)