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AT&T and BT Plot Cellular IP Link
By Joanne Taaffe at CommunicationsWeek
International
23 June 1999
AT&T and BT plan to align their disparate cellular networks to
offer corporate users global access to mobile voice and data
applications. The plan foresees the creation of a new IP-based
mobile network, and the two companies have formed a
carrier-vendor alliance they hope will drive the adoption of the
IP-centered approach across the rest of the industry.
"We'll have a truly global access network, [with] the same user
interface and user experience," said Hans Andersson, director,
network architecture, at AT&T Wireless Services Inc.,
Redmond, Washington.
In an initial move, BT announced it will start offering simple
data services such as calendaring and e-mail over its existing
circuit-switched GSM networks later this year. However, the
two companies remain tight-lipped about the way these
corporate wireless applications - developed with Microsoft
Corp. - will be marketed, and how closely they will work on
building next-generation IP-based cellular networks.
Philip Marnick, BT's head of mobility development, said its
simple wireless data services "will in all likelihood become a
part of ... [the] Concert portfolio," BT's global services
operation. But he added that the next-generation IP project
does not come under the umbrella of the AT&T and BT formal
alliance. "The mobile side is not in the joint venture, but
there's a lot of understanding we can transfer," he explained.
Last month the two operators created a working group,
dubbed 3G.IP, to drive the standards needed for the creation
of a third-generation Universal Mobile Telecommunications
System (UMTS) IP-based network. Members of the group
include Telenor AS, Telecom Italia Mobile SpA and Canadian
wireless operator Rogers Cantor, as well as equipment
vendors L.M. Ericsson AB, Nortel Networks, Lucent
Technologies Inc. and Nokia Oyj.
By 2003 the duo aims to make IP the standard transport
medium for data and voice throughout the mobile network.
Although the operators are primarily concerned with how IP
works with wireless, said AT&T's Andersson, they are also
considering "the convergence of wireless and fixed, and the
service offering." He added that "IP is an ideal candidate for
making that happen."
Other members of 3G.IP say that these attempts to ensure that
IP can run effectively across wireless networks from the
handset right through to the core network tie in neatly with
the AT&T-BT plan, announced last year, to build an IP-based
fixed network.
"The architecture that they've put up for their international
joint venture fits very well with this idea," said Oddvar
Hesjedal, vice president of research and development at
Telenor, which has an alliance with BT. Hesjedal added that "it
fits well with a common project [between Telenor and BT] that
we can't reveal."
BT and AT&T are also working to ensure that BT Cellnet's
GSM network inter-operates with AT&T's TDMA network:
Cellnet plans to upgrade its GSM network to General Packet
Radio Services (GPRS) towards the end of next year, before
later installing a UMTS network. Meanwhile, AT&T will
evolve its TDMA network to EDGE (Enhanced Data for GSM
Evolution), which because of spectrum limitations will also
serve as AT&T's third-generation network, said Andersson.
"By 2001 we'll have EDGE for Internet browsing and corporate
access. BT is launching [its service] on its existing air
interface, and we will do some trials. The big commercial
offering will be on EDGE, when we will be able to interwork
with GPRS, and then we'll be able to do data roaming at that
point," said Andersson. He added: "Around 2003 we'll have a
voice-over-IP-centered architecture ... Over time, the circuit
switch will be legacy."
Most cellular operators support an evolution toward IP-based
packet-switched networks, said Roger Tarazi of the European
Telecommunications Standards Institute (ETSI). "A 3G
network would revolutionize the way information is
transported today ... The use of an all IP-based architecture
will provide a basis for advanced multimedia services, he said.
Such services could include virtual private networks, provided
over fixed and mobile networks, that share a common
environment, said Robin Duke-Woolley, senior consultant at
Schema Ltd., London.
How fast operators will move over to packet-based networks,
however, will vary. "It will be an evolution in that direction,
with different people going at different speeds," Tarazi said.
AT&T and BT believe that by using IP they will cut the cost
of installing, running and developing applications for wireless
networks. "The reason is cost, global roaming and economies
of scale," said Umesh Amin, director, new technology &
planning in the technology development group, AT&T
Wireless Services.
The 3G.IP group will work on IP over wireless with the 3G
Partnership Project (3GPP) - an industry body working on
technical specifications for a 3G mobile system based on the
evolved GSM core networks - and ETSI. But in a new move for
the cellular industry, it will attend an Internet Engineering
Task Force (IETF) meeting next month with a view to
developing a specialized version of IP that can cope with the
addressing and signaling demands of a mobile network, whose
subscribers are, by definition, always on the move.
"It's an initiative ... to take a lead in an all IP-based
architecture," said AT&T's Andersson, who added that a
working group was necessary because "there is no room in
formal industry bodies to take such a leap into the future."
The fact that IP has been designed to deliver packets to a fixed
address is only one obstacle. IP headers are too bulky for
bandwidth-restricted wireless networks and need to be
stripped. And as wireless networks are not fixed point to fixed
point, there is no guarantee that packets will not be dropped, a
necessary requirement for voice calls. The group hopes to
work with the IETF on reducing the length of the packets so
that less information is lost should a packet be dropped.
The members of 3G.IP are not alone in working towards
unifying fixed and mobile networks in order to create a flexible
core IP network that can interoperate with applications in a
standardized way, said Henry Harrison, senior consultant at
Schema. "All manufacturers and pretty much all operators are
talking about IP at the core of ... unified networks," he said.
The 3G.IP group's three principle objectives are: To develop
"an all IP-based architecture and not deploy circuit-switching
and ensure that wireless is very well represented in the
evolution for voice over IP; [develop] global harmonization
between EDGE and W-CDMA handsets; [and] jump-start IP
technology for wireless," said Andersson.
The question of IP's role in UMTS networks comes only two
years before the first UMTS networks are expected to be
deployed, and around 10 years into the development life of 3G
networks. However, "UMTS is defined in two phases. First
[there was] the radio interface. The next step is the core
network and discussions on whether fixed and mobile should
be defined in the same manner. That will be defined in
2000-2001," said Telenor's Hesjedal.
Although the basic elements of UMTS networks have been
sketched in - for example, manufacturers know there will be a
base-station controller with wideband radio and a base station
- the industry is now in the process of "coming to an
agreement on the type of network nodes and their hierarchical
relation," after being held up in disputes over what the air
interface should be, said Filip Lindell, senior manager for
wireless strategies at Ericsson.
UMTS could have deployed an evolution of existing wireless
protocols that have been developed to deal with signaling to
terminals on the move, much as the protocols for GPRS
packet-based networks have grown out of GSM. "Current
mobile systems have developed a very efficient hand-over
system," noted Nokia's Ukko Lappalainen. And with an
Internet gateway between the core wireless network and the
fixed network, GPRS will support IP, even if it is not an IP
network.
Recently, manufacturers and carriers have realized that IP
could be a viable protocol for 3G. The belief among 3G.IP's
members is that most corporate networks are moving over to
IP-based networks and that corporate users will push the
growth of data use on wireless networks. "A few years from
now [we want] an end-to-end, IP-based telecoms network,"
said AT&T's Amin.
But the equipment manufacturers are not underestimating the
amount of work required. "Native IP from the terminal will
require quite a lot of work," said Nokia's Lappalainen, adding:
"There is no clear standard on voice interoperability on IP."
Members of 3G.IP hope, however, that common specifications
will start to be drawn up towards the end of this year.
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