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Software radios could bring flexibility to base stations
By Kristen Beckman
Flexibility may be coming to a base station near you.
August 10, 1998
Most base stations today are built to accommodate only one or two wireless technologies, but a
relatively new concept may allow carriers to reconfigure base stations to support a variety of
standards and applications.
Software radios are ``radios in which a large portion of the functionality is implemented through a
programmable signal processing device,'' according to Jeffrey H. Reed and Brian D. Woerner,
authors of a textbook on software radios due out next year.
Using a software radio within a base station would allow manufacturers to build one hardware
product that can house software radios which can be reconfigured to support different technologies
and applications. That translates into better cost efficiencies for the manufacturer and ultimately
service providers, say experts.
``The topic of software radio has been around for awhile, mainly in the military,'' said Stephen
Blust, senior manager of strategic technology at BellSouth Cellular Corp. Although the military
remains a primary market for software radios, the commercial wireless industry recently has begun
to take an interest in the concept, he said.
Blust is chairman of the Modular Multifunction Information Transfer System Forum, which is
changing its name to the Software Defined Radio Forum. The group, comprising the defense and
commercial wireless sectors as well as civil government, is working to implement software radios in
wireless handsets and base stations.
The group has been focusing on handset issues, but members expressed enough interest in base
stations that a new working group was formed to look at the idea. Blust said.
``There has definitely been an increase in the noise level surrounding software radios in the last 18
months or more,'' said Blust. ``People don't say `what?' anymore when you ask them about
software radios. They ask `when?' ''
Possibilities
While software radios could have applications in today's second-generation systems, many
software radio experts expect third-generation technology to drive the use of software radios.
One of the most compelling advantages of software radios is their ability to support multimode
operations.
``Traditionally, dual-mode operation has required two complete sets of hardware, increasing the
size and cost of the radio,'' said Reed, who also is associate director of the Mobile & Portable
Radio Group and an associate professor of electrical engineering at Virginia Tech. ``A software
radio could change modes by simply loading a different piece of software into the memory.''
Software radios also would allow use of advanced signal processing techniques such as adaptive
antennas, interference rejection and strong encryption, said Reed.
Advances in technology used to mean equipment became obsolete rather quickly, but with software
radio base stations, the hardware need not be replaced. Only the software needs to be changed.
Blust said service providers and manufacturers don't have to wait until 3G is a reality before
investing in base stations equipped with software radios once they become available.
``I would hate to have put in base stations and cell sites that are only one year old and then have to
tear them out when 3G comes along,'' said Blust. ``Instead, if I buy a software radio now, it forms
an evolution platform that will meet next-generation needs in a couple of years.
``It's like planting the seeds now so I don't have to do a `forklift' migration later,'' he said, referring
to the alternative of completely replacing base station equipment later.
Virginia Tech's Reed sees even more potential for software radios.
``I don't think we will see the full potential of software radios until fourth-generation wireless
systems,'' said Reed. ``We'll see both handsets and base stations with software-defined radios
actually determine which air interface to use according to the current conditions.''
For instance, ``If there is heavy traffic on the network, the handset and base station can reconfigure
themselves to work around it,'' envisioned Reed.
``A few years ago, everyone was concerned about the splintering of standards, and everyone said it
was a tremendous disadvantage,'' he said. ``Maybe it's not so bad after all. It might actually be
good because all of the technologies have their relative strengths and weaknesses, and software
radios can be used to exploit the strengths of each technology.''
Challenges
Dr. David Goodman, director of the Wireless Information Network Laboratory (WINLAB) at
Rutgers, said although software radios are extremely promising, proponents should be careful to
consider some of the hurdles that need to be overcome before software radios can be used to solve
3G problems.
``There is still a lot of work that needs to be done to take advantage of software radios,'' he said.
``People that are counting on software radios to be a panacea for 3G may be assuming too much.''
For the idea to work, the influential infrastructure providers will have to embrace and support the
idea, said BellSouth's Blust.
``Early on, a couple of companies had some ideas, but they weren't the traditional infrastructure
manufacturers of the industry,'' said Blust. ``In the United States, systems are tightly integrated from
the base station to the switch. It is difficult for a third party to bring a product in because there is too
much proprietary equipment.''
Manufacturer Watkins-Johnson has developed and deployed a base station product that
incorporates software radio technology, said Andrew Park, a member of the technical staff at the
company. Watkins-Johnson is exploring partnership opportunities with larger manufacturers, he
said.
``Many of the American carriers are quite conservative in what they want to deploy,'' said Park.
``They want to make sure it doesn't hurt any previous equipment they've deployed.
``Partnering opens up bigger doors,'' continued Park. ``Companies like Lucent (Technologies Inc.),
(L.M.) Ericsson and [Northern Telecom Ltd.] all have very well-established switching systems,
which carriers view as the center of their infrastructure. `[Carriers] want things to work with that.''
In addition, said Park, the amount of proprietary equipment deployed forces carriers to buy
equipment from the same companies that provided the switches, making it difficult for third-party
vendors to come into the market with a product on their own.
Implementing software radios also would be a fairly dramatic departure from the way infrastructure
manufacturers are used to doing business.
``It changes the market value of the product manufacturer. The value shifts to the software,'' said
Blust. ``It's a different way of doing business, and it's not necessarily an easy transition. There are
positive things happening, and efforts are moving forward, but business issues often override.''
In the end, said Blust, software radios can help carriers accomplish one of their top
priorities-making technology transparent to the customer, especially moving toward 3G.
``Service providers are beginning to recognize the long-term benefits,'' he said. ``This industry is
traditionally consumed with next quarter.
``Now they are starting to look more to future opportunities,'' he said. |
