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NewsGlobe: Interviews
Sprint bulks up on backhaul
Finds utility emerging IP/Ethernet and microwave approaches
by Sean Buckley
Sprint Nextel may be one of the largest wireless network providers, but
the growth of new unlimited plans, including its own Sprint Everything
plan—not to mention its WiMAX network—is putting continuous
constraint on its backhaul network.
Like its wireless brethren, Sprint Nextel’s default backhaul strategy has
been to rent T1 circuits from the local ILEC. Sprint realizes, however,
that T1s, despite their reliability, are limited in terms of scale and quite
expensive to maintain.
“What we’re seeing with the Simply Everything product from Sprint and
with the rest of the industry is that the increase in unlimited data and
voice plans exponentially increases the backhaul requirements of 2G and
3G networks,” said Craig Cowden, Sprint’s vice president of cable/VoIP
and access strategy, at the recent Converging 2G/3G and UMTS/CDMA
on Common Backhaul Infrastructure panel at CTIA Wireless 2008 in Las
Vegas. “There’s a challenge where we can’t just scale with LEC T1
because one, it’s expensive and two, it does not scale operationally or
financially.” (See:
Breaking the backhaul bottleneck)
Cowden added he’s keen on leveraging new alternatives that offset
having to pay Sprint’s nearest competitor—the ILEC—any more money
than it has to. To break free of the T1 bottleneck, Sprint is using a
number of new approaches including everything from pseudowires and
optical to HFC.
Even with all the options, Cowden said, “There’s no one silver bullet
solution” for wireless backhaul.
Multi-purpose platforms
While fiber-based solutions are Sprint’s preferred method for wireless
backhaul, the operator increasingly has been leveraging the cable MSO’s
fiber and, in some cases, its coax.
Working with cable operators makes sense. In recent years, cable
operators have been breaking out of their video-centric shells to offer
business and even wholesale services. In terms of wireless backhaul,
cable operators often have fiber and coax passing cell sites, so
extending these facilities into a tower would be as easy as extending a
fiber drop to the site.
In addition, Sprint already supplies many cable operators with turnkey
VoIP solutions, besides working with major MSOs (i.e., Comcast, Cox and
Time Warner Cable) on joint wireless initiatives.
“We’re spending a lot of time working with the MSOs, some more
aggressively than others, to develop a DOCSIS-over-Ethernet standard,”
Cowden said. “We’re working with them to develop not just the
technology but also the systems interface because we want to use their
coax for Ethernet.”
Cowden added that coax can be leveraged by other Sprint divisions. “It’s
not just for cell site backhaul,” he said. “It’s also a huge driver for our
enterprise last-mile access requirements.”
To expand its Ethernet service set to a broader audience, Sprint
launched Sprint Provided Ethernet Access Service late last year. With
this initiative, Sprint’s business division will leverage traditional copper,
DSL, wireless and coax to deliver Ethernet to business customers. (See:
Sprint steps out with Ethernet)
“By combining cell site backhaul needs and our business service
requirements, it really creates a scale that makes it attractive for them,”
Cowden said. “Strategically, Sprint is very interested in pursuing
solutions that reduce access costs, but [also] redirect it from AT&T and
Verizon.”
Along with cable, Sprint is trialing Ethernet-over-copper solutions with
an unnamed access service provider that can bond potentially multiple
T1 circuits to expand available bandwidth over existing copper for 3G
backhaul.
It’s currently trialing one unnamed operator’s solution and, despite some
of the distance limitations of copper, Cowden likes what he sees.
“For all 3G cell site backhaul, we think there’s an interim niche, and an
interim could be a long time,” Cowden said. “We are working with
providers right now, and we think we’ll be able to test the viability of a
10-meg, Ethernet-over-copper solution. We’re very interested in it as an
interim technology, and we will go to fiber as a long-term solution, but
long term can be just that.” (See:
Bonding with copper)
Two-tier WiMAX solution
Of course, 2G/3G wireless is only one part of the Sprint backhaul
network equation.
Despite naysayers, Sprint’s new CEO Dan Hesse emphasized recently
that the operator’s XOHM WiMAX service being offered up as a total
package gives it a two-year start over others making a migration to long
term evolution. Keeping the spirit of using common wireless technologies for its
networks, Sprint is looking at various alternatives for its XOHM WiMAX
service.
Because it’s a greenfield 4G wireless network, Sprint’s backhaul mode for
WiMAX includes a mixture of fiber and microwave from alternative
providers such as Fiber Tower.
Sprint has taken a two-tier approach to WiMAX backhaul:
• Wireless aggregation converged backhaul uses a mixture of
traditional microwave, LMDS and/or BRS (2.5 GHz spectrum);
• Backhaul hub to Sprint facilities uses a mixture of Ethernet
over DWDM, Ethernet over SONET, or a third-party provider’s facilities.
(see Figure 1).
Sprint sees potential in LMDS, for example, for other wireless backhaul
needs.
“We’re looking at LMDS aggressively,” Cowden said. “LMDS has some
technical limitations that I think we can work through, but we’re more
concerned about the economics right now.”
Bridging TDM to IP
For all Ethernet’s promised capabilities, the reality for wireless operators
is there’s still a lot of TDM in their networks. The question then becomes
how they can effectively bridge the gap between their current TDM-
based investments and the IP road.
While some operators (mainly in Europe) have opted for a split
deployment, placing all voice traffic on traditional TDM-based circuits
then running data over Ethernet, Sprint is not chasing such an approach.
Instead, Sprint is using two converged access methods to accommodate
TDM and IP/Ethernet.
At the cell site, Sprint will deploy equipment that includes both an
Ethernet interface and a traditional T1 interface. The egress port coming
out of that equipment would be fiber. Within the fiber itself, Sprint will
allocate T1 and Ethernet. Depending on the type of service, it would
either ride the Ethernet or T1 pipe within that fiber.
In addition, Sprint is looking at pseudowire solutions that would emulate
the T1 across a larger 1 GigE pipe.
As it deploys its WiMAX backhaul capabilities, Sprint will leverage the
same solution for its existing 2G/3G wireless needs where necessary.
“With some of our AAV and MSO alternatives, they are producing fiber-
based solutions for 4G backhaul, but the equipment they deploy allows
for the muxing on a T1 interface and the output is across fiber,” Cowden
said. “Where we have that type of solution and where a WiMAX tower is
collocated with a 3G tower, we would take advantage of that same
capability.”
Whatever technology strategy it pursues, depending on what the
particular situation, Sprint is high on the possibilities of Ethernet.
“I want to send a message to vendors, potential vendors and access
providers that we are motivated to move toward the economics of
Ethernet-based solutions and the bandwidth upgrade flexibility of
Ethernet solutions,” Cowden said. “We’re also motivated strategically to
redirect our access spend away from AT&T and Verizon.”
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