xG Technology: Cognitive radio is real today

For years, I attended trade shows where speakers talked about the virtues of software-defined radios that could be programmed to operate in different spectrum bands. Today, multiband devices leveraging this technology finally are on the market, but engineers already are looking toward the next step — cognitive radios that automatically harness the frequency-agility aspects of multiband devices without the need for human intervention.

It's a concept that certainly has resonated within the military, which often has to communicate in hostile environments in which spectral planning is difficult, if not impossible, and enemies are not hesitant to use jamming technology, if they believe it will help them gain an advantage. DARPA is in the middle of a testing program that promises to result in cognitive military radios that can be sold for less than $500.

Eventually, this technology could be used in the commercial and public-safety sectors. However, that transition from military research to commercial products historically has taken years.

But officials for Florida-based xG Technology says there is no need to wait that long, because it already has a commercially available cognitive-radio system known as xMAX. Although currently designed to operate in the unlicensed 900 MHz ISM band, the cognitive-radio characteristics of the xMAX technology allows the system to be frequency agnostic, according to Rick Rotondo, xG Technology's vice president of marketing.

"It's a carrier-class, cognitive-radio network," Rotondo said during an interview in the conference room at a Chicago hotel. "What is carrier class? What first comes to mind is being able to offer competitive services, quality of service and reliability as any other carrier in the market."

The notion of delivering carrier-class quality of service over unlicensed spectrum — where best-effort technologies like Wi-Fi are norm — would seem impossible with most wireless technologies. However, the xMAX system assesses the spectral environment and utilizes vacant frequencies in 33-millisecond intervals.

From the Chicago conference room, Rotondo let me make a call over a base station plugged into a wall socket to one of the harshest xMAX skeptics I know while a jamming device was operational in the room. I was allowed to turn a knob that caused the jamming to occur at different frequencies. During the call, I turned the knob multiple times per minute during my conversation, forcing the xMAX system to move to a different channel. The recipient of my call said the voice quality was good and did not notice any changes as the used frequency changed.

Mind you, other technologies employ similar techniques in unlicensed, but most of them are operate only in short-range environments. By contrast, xMAX performs at cellular-like ranges while still operating at the Part 15 power limit of 1 watt.

Rotondo said this range is possible because of the way xG Technology CTO Joe Bobier has optimized the system. One particularly interesting feature is the use of the company's patented passive combiners that greatly enhance the efficiency of the xMAX network, he said. Instead of using an expensive active combiner that requires power results in a 5 — 7 dB loss, the passive xMAX combiner uses no power, is significantly less expensive to manufacture, and — most important — has an insertion loss of just 0.3 dB.

"It's absolutely brilliant," Rotondo said, noting that the solution could be used in other wireless and wired systems. "This is really a breakthrough implementation of a standard technology."

Whether xG Technology's xMAX system becomes commercially successful is anybody's guess at this point, as the Florida-based startup could face a number of regulatory, technical and business challenges. However, the cognitive characteristics of the xMAX system and tools such as the passive combiner sound like good ideas that have an impact on the future evolution of communications.

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