Feature Story

COMMUNICATIONS BREAKDOWN: A CASE FOR SOFTWARE-DEFINED RADIOS

When fighter pilots of the U.S. Marine Corps VMFA-232 "Red Devil" Squadron recently returned from Iraq, one captain in particular shared an anecdote about his experience coordinating and communicating with U.S. and Coalition forces.

"Having just gotten back from Iraq, one of our primary jobs was to launch off the aircraft carrier and fly out over Baghdad" to support U.S. troops on the ground, he explained during a brief interview conducted here at the Miramar Marine Corps Air Station.

"A good portion of the task was over Baghdad where we'd be working for the Army. And having brought an Army guy out to the ship - a HeLo [helicopter] pilot as well as one of their ground guys … they had very little idea that we were even up there. One of the Army helicopter guys … with 20 years of flying experience was like: 'I had no idea I had fixed-wing support 20,000 feet above me overhead.' They are not doing a good job of coordinating the efforts right now, I would say, to essentially let us talk to the Army guys on the ground," the captain said.

The communications breakdown described by this fighter pilot (who spoke on condition of anonymity) isn't isolated just to the Marines. But U.S. Defense Department also isn't oblivious to problem. Just down Interstate 15 here in this perpetually sunny Southern Californian metropolis is headquarters of the Joint Tactical Radio Systems (JTRS) - a joint U.S.-NATO program nicknamed "Jitters" that began in 1997 to develop and implement interoperable nodes within the access layer of field communications in the form of software-defined radio (SDR).

The concept of the SDR is by no means new. Before JTRS, there was another military initiative dubbed "SpeakEasy." And, clearly, the work of government-sponsored programs could have easily translated to benefits that ideally can trickle into the public and commercial sectors. Imagine the possibilities if the New York Police Department can seamlessly communicate with the firefighters and EMS workers of the FDNY on communication systems that relies on software to reprogram a radio's modulation schema. But analysts and industry experts argue that government SDR development has yet to produce ubiquitous commercial radio access networks (RAN) and currently don't go far enough in advancing interoperability even for the military.

"Of course, the reality of the SDR is far from the ideal. The industry has been talking about the possibilities of such a system for two decades time and it could still be years before we see commercial deployments," Deutsche Bank Analyst Brian Modoff wrote in a recent report. "Nonetheless, we think the case for SDR has become more compelling of late."

While the notion of ubiquitous radio communications may conjure up imagery of science fiction, the reality is SDRs are already being supported on a single chipset that is reprogrammable on-the-fly.

"That's being done already today," explained Lee Pucker, Chief Technology Officer at Spectrum Signal Processing based in British Columbia, Canada. Pucker is also the Chairman of the Designs, Process and Tools Working Group of the SDR Forum. "It's a lot closer than you think but there's still a lot of work that has to be done on it."

As open standards-based interoperability gains traction at the network's core particularly as it relates to IP-based communications, carriers and telecom equipment manufacturers (TEMs) may be empowered to develop similar changes at the network's edge. "We could start to see changes in RAN that could happen in parallel to the advent of IMS," according to Modoff.

In order to control traffic modulated between 802.11g, CDMA or GSM, Modoff believes a best-practices method calls for SDR to reside in the infrastructure side of the access link rather than sit on the base station or the customer-premises equipment (CPE). "SDR deployed on a fiber-optic based architecture would be very appealing considering the types of traffic and radio resources likely to be encountered in high traffic areas - airports, malls, high rises," the DB analyst concluded.

However, while government-sponsored research have, thus far, done little to standardize the architecture, the biggest drawback with programs like JTRS is not taking into account a roadmap that would future-proof the technology, Pucker added. As the electrical engineering community begins to explore the commercial viability of SDR, Pucker believes it should also look toward the next logic step - that being "cognitive radio," a system that continually examines the operator's spectrum and then tailors the radio functions based on the current environment in which the radio is operating in.

"The JTRS program is about having radios where the air interface standards, the wave forms, can be changed on-the-fly but it's not doing it automatically based on the assessment in the environment," Pucker explained. "There's a difference between having SDRs and having cognitive-radio abilities. JTRS is all about SDR."

Representatives of the JTRS were unavailable for comment. But in the Pentagon's defense, two DARPA projects - NeXt-Generation Communications (XG) and the Wireless Network after Next (WNaN) - are trying to develop technologies and systems concepts to enable intelligent adaptive wireless networks.

Even with all those kinks worked out, though, a complex set of issues completely unrelated to technology pose as challenges to commercial deployment of ubiquitous radio. For starters, there vast extent of North American jurisdictions creates a public policy conundrum. So while groups like the SDR Forum are looking at what the requirements are for interoperability for first responders and the public safety sector, there are a number of other things that have to be done as well. "How do you prioritize communications? Do you need multiple, different levels of security?" Pucker asked rhetorically.

Another issue is money - not so much in the form of funding for research and trial deployment but to determine which business models are viable and which aren't. For example, a key requirement in the defense space is to ensure wave forms modulate quickly enough to enable interoperable and, hence, effective communications. But in the commercial sector, there may only be a handful of modulation schemas to support so there's less of a need to switch dynamically between them and more of a need to ensure the scalability of new features to the platform over time, Pucker explained.

"When you look at the trade-offs, you look at different business drivers and there are different business models in which they operate," Pucker said.

While the heart of the telecom industry (like Ericsson, Nokia and others) has yet to join the SDR Forum and jump aboard the cognitive radio bandwagon, there are a growing number of other companies worth watching. Among them, DB's Modoff points to Aeroflex, a supplier of test gear to the JTRS program. Also worth watching are companies ranging in size from defense contractor L-3 Communications on the high end down to Bitwave Semiconductor, a fabless chip company that has already developed the single, universal chipset.

Return to: 2006 Feature Stories