Flexibility may be coming to a base station near you.
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.
