Subject: [NEXTEL-1] Nextel & SDR

From: Marcel <[email-masked]>
Date: Mon, 31 Mar 2003 13:10:28 -0500

Wireless Web anywhere
Source: Network World
Publication date: 2003-03-24
Arrival time: 2003-03-28

It's all about the handoff between 802.11b LAN technology and wireless
WAN standards,

You're in a hotel lobby using its IIM bit/sec 802.11b wireless LAN to
download e-mail to your laptop, when your cab arrives.You get in, and your
laptop continues downloading, though at a slower rate, all the way to the
airport.

At the airport,you proceed to a passenger lounge where the transfer rate
picks up again thanks to another802.11b network. All this happens
seamlessly with no indication, other than the change in data rate, that you
are moving from a LAN to a WAN to another LAN.

You can't do this today because wireless LANs based on IEEE 802.11
protocols can't talk with wireless WAN i that use data-over- cellular
standards such as GSM, General Packet Radio Service (GPRS) and Code
Division Multiple Access. However, the major wireless carriers, inclucing
AT&T Wireless, Nextel, Sprint PCS,T-Mobile and Verizon, are expected to
begin supporting such LAN/WAN handoffs, with the first implementations
possibly later this year.

Let's take a step back to describe how we got to this point. Soon after the
Wi-Fi or 802.11b wireless LAN standard was ratified in 1999, the technology
began taking over public access hot spots such as airports and hotel
lobbies.

Initially, cellular operators saw the new wireless LAN standard as
competition.They had hoped to charge by the byte for data services such as
text messaging, Web surfing and downloading or sending e-mail on 3G
networks in which they had invested billions of dollars.They didn't want
high-speed public LANs "stealing" than traffic.

During the next few years, however, a couple of things became clear: First,
3G rollout and market penetration would take longer than operators had
hoped. Second, 802.11 became the overwhelming technology of choice for
companies installing hot spots. Operators decided if they couldn't beat 'em,
they'd better join 'em.

*In December 2001,Sprint PCS invested $15 million in Boingo Wireless,
which now operates about 1,000 hot spots. Sprint PCS has talked about
developing a dualmode WAN/wireless LAN card and a service to take
advantage of it.

* In January 2002,VoiceStream Wireless, now T-Mobile, purchased bankrupt
MobileStar Networks, which operated hot spots at Starbucks
locations.Today, the rebranded T-Mobile HotSpot service lets customers
connect in about 2,000 locations such as Starbucks, Borders bookstores,
airports and airline clubs. Customers also can use the GSM/GPRS WAN
when no LAN connection is available.

T-Mobile also has announced plans for an integrated GPRS/Enhance Data
Rates for Global Evolution/802.11b service offering, expected to arrive
sometime in 2003, that would let customers switch manually between Wi-Fi
and cellular.

* In April 2002, Nextel Communications announced that it was testing
technology from RadioFrame Networks that would let enterprise customers
receive cell phone calls indoors via a software- defined radio (SDR) system
designed to combine multiple cell phone networks with 802.11 networks.

And technology is emerging to support the merged WAN/LAN vision. Nokia
has announced a PC card that incorporates GSM/GPRS and 802.11b. In
addition,you can create a dual-mode platform by adding a GPRS card to a
laptop with built-in 802.11b.

However, there are still problems. For one thing, even though wireless
carriers have bowed to the inevitability of public access 802.11b, it's still not
clear how well the wireless LAN fits into carriers' business models.

Wireless LANs are less expensive than WANs, if only because they run on
unlicensed ("free") spectrum. Accordingly, hot spot operators charge much
less per megabyte than wireless carriers.The result is lower revenue, even
for carriers that get into the hot spot business. And there's a limit to how
much carriers can lower data prices on WANs, because too much data
could reduce their ability to carry voice traffic - their bread and butter.

In addition, it's going to take a lot more than the right hardware in a laptop to
enable seamless wireless LAN/ WAN roaming.There are difficult issues
involved in switching the TCP/IP sessions between networks operated by
different companies, says Christian Gunning, director of product
management for Boingo.

"With built-in 802.11b,you'll only really need a WAN card,"says Fran
Rabuck, president of Rabuck Associates, a mobile consultancy"How or if
the handoff will work between the services is a really big question."

That's one area where T-Mobile has the advantage of both being the largest
hot spot operator and owning a nationwide GSM/GPRS network, Rabuck
says.

T-Mobile likely will phase in wireless LAN/WAN integration, says
spokeswoman Kim Thompson, with some level of integration taking place
this year, although probably not transparent handoffs.

T-Mobile might find a worthy competitor in the recently formed Cometa
Networks, a joint venture of AT&T, Intel and IBM (along with Apax Partners
and 3i), established to provide wholesale nationwide broadband wireless
Internet access, Rabuck says.

Two technologies to watch as likely enablers of transparent handoffs are
Mobile IP and SDR.The Mobile IP protocol is designed to handle handoffs at
the network layer (Layer 3),while leaving the transport layer (Layer 4) and
above unaffected, so that the existing routing infrastructure, nonmobile hosts
and applications don't have to change.

SDR operates at the data link layer (Layer 2),which is responsible for link
establishment and maintenance. Because wireless LAN and wireless WAN
technologies are radically different at Layer 2, a device is required to tie
them together. SDR is a good option.
http://cnniw.yellowbrix.com/pages/cnniw/Story.nsp?story_id=37678711&ID=cnniw&scategory=Business+and+Finance&

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