Today, the mobile components needed for expanding coverage via roaming among multiple networks must be bought and deployed separately. Achieving smooth roaming among wireless networks with no break in a session requires IT to buy, install and manage multiple physical connections per device and deploy special client/server software to enable session persistence when roaming.
In addition, Wi-Fi-to-cellular handoff products and services leave IT departments speculating about the logistics of merging their networks with a carrier's in terms of service levels, troubleshooting and security.
"The subject of service-level agreements is fastidiously ignored by those who advocate mixed 802.11 and cellular solutions," says Doug Hill, an associate technical fellow and network chief architect at The Boeing Co. Carriers have approached Boeing about running a carrier-controlled mixed network where the carrier charges for voice-over-WLAN calls handed off to Boeing's internal Wi-Fi network at a lower rate than for the portion of a call moving over the cellular network.
But in a potential bridged Boeing-carrier infrastructure, neither party could monitor or troubleshoot across the public/private network boundary without sharing management information with the other. Not sharing the information with the carrier could degrade service quality, but doing so could introduce security concerns, Hill says.
This conundrum is one reason why Nortel, at least in the short term, will likely use premises-based equipment for such handoffs. The company is running trials of Wi-Fi-to-cellular handoffs with national carriers, testing the capability as both a premises-based and a carrier services function, Hitchcock says.
Another reason to house and manage the handoff equipment internally for now, Hitchcock says, is that "there's no single global carrier that can serve our 70-country footprint."
Notes Roger Entner, vice president of wireless telecom at researcher Ovum Ltd., "Your carrier can loan you another [modem] card if you [travel internationally]. Your other option is to rely on global Wi-Fi hot spots."
Roaming issues are why Atlanta-based United Parcel Service Inc. now does business directly with the world's five largest network operators. UPS drivers use the company's self-developed, laptop-based Delivery Information Acquisition Device (DIAD) to frequently transmit delivery status information to the corporate mainframe.