Wireless/Mobile /

The many facets of roaming

By Joanie Wexler
Network World Wireless Newsletter, 06/11/01

Last time, I discussed efforts under way by the Wireless Ethernet Compatibility Alliance to propose industry-standard backend billing and settlement systems for wireless ISPs. The group's work is aimed at enabling users to take their office laptops and roam among public wireless 802.11 LANs installed in airports, hotels, conference centers, country clubs and the like. Such LANs are likely to connect to different ISPs in the wide area but the Wireless Ethernet Compatibility Alliance's back-end settlement efforts should nonetheless allow users to receive a single, consolidated bill from their primary ISP.

There are separate efforts with similar goals in the 2.5G mobile arena that are specifically targeted at General Packet Radio Service (GPRS) networks. GPRS is a 2.5G, packet-based version of GSM airlink technology. It is also an interim network to 384K bit/sec-and-up 3G networks and can deliver IP-based packet data speeds up to a maximum rate of 160K bit/sec. As a result, GPRS offers much greater potential for data and multimedia services than the 20K bit/sec circuit-switched speeds of today's GSM and other 2G networks.

Currently, users with GSM mobile phones (the dominant technology in Europe and offered as services in some U.S. regions by Cingular Wireless, VoiceStream and other smaller carriers) can roam among different GSM operators' networks. Now, with mobile networks entering the GPRS packet-switched environment, new roaming agreements must be struck between wireless service providers and ISPs.

GPRS roaming services have begun to be implemented using certain network operators as a GPRS Roaming Exchange (GRX) network. GRXs standardize access point name addressing, security protocols and GPRS call routing over Internet domain name servers. These exchanges are similar in concept to the network access points (NAP) in the wired Internet world; they eliminate the need for wireless carriers to have peering agreements with each other and the scores of ISPs in the middle. Wireless network operators route calls into the exchange, which then forwards the calls over a private IP network, separate from the public Internet, to their destination network.

Like the NAPs (and unlike the Wireless Ethernet Compatibility Alliance efforts), though, the GRX is a transport service only. A mobile network operator needs to have a settlement service in addition to the exchange to provide the bill consolidation service for customers. These business agreements are, of course, the toughest part of the equation. The GRX will provide the usage statistics to enable the settlement services, say GRX experts at global carrier Equant, which is has partnered with Finland-based worldwide wireless operator Sonera to provide GRX services to Sonera and other operators.

Worldwide carriers such as WorldCom and Infonet are also among the companies leading the charge of these wireless exchanges.