THE FUTURE AS SEEN THROUGH TECHNOLOGY

When Donald Arnstein and Paul Ebert walked into the offices of a major telecom service provider earlier this decade to show off their new technique for propagation analysis, they thought they had hit the big time. Years of thoughtful work by the men, friends since grad school in the 1960s, seemed to have the potential to pay off. The service provider could give them licensed spectrum in which to test their invention — who knew what else might lay ahead.

The service provider was WorldCom. “We thought we had it made,” Ebert said, “but we went and talked to these people, and they were all starting to look for other jobs.”

But Arnstein and Ebert kept working. They founded Saraband Wireless in 2000 with their own money and continued to develop their chip-based “propagation analyst” technique, earning a National Science Foundation Grant that helped fund testing and verification of the system. They received a U.S. patent earlier this month.

“We think we're the only company out there that's interested in developing propagation estimation aids to be deployed at every wireless link on the network,” Arnstein said.

The Saraband Vector Network Analyzer Applique (VNNA), as the company is calling its patented but not-yet-productized system, puts a new spin on traditional vector analysis, which measures conveyance and modulation distortions in signals being transmitted. The VNNA splits a wireless channel measuring device into two halves, a signal injector and a signal receiver that can be placed many miles apart. Saraband's patented feedback system aligns the timing of crystal oscillators within each device so that an entire wireless channel between two points can be swept in real time for channel state path conditions that might otherwise affect the wireless transmission.

“We send out strobing signals that constantly measure the channel from the transmitter to the receiver and back again,” Arnstein said. These two-way measurements also are integrated with an adaptive processing circuit that uses the measurements to correct interference between the two points, potentially helpful in making transmissions from non-line-of-sight gear more reliable and capable of greater distances. The system uses less than 1% of the available channel bandwidth to make all of this happen.

Channel path interference is common in both licensed and unlicensed spectrum, but Arnstein and Ebert think their VNNA is more useful for licensed spectrum networks because of how firmly the parameters of band usage are defined. They believe the VNNA would be best if integrated into new base stations, and with that in mind, Saraband is looking for partners.

Although the timing was off with WorldCom, the timing might be right now. New WiMAX networks are being built in licensed spectrum, and equipment vendors and service providers want to use signal enhancement techniques to give them an edge in capacity and coverage, respectively. Saraband's VNNA might fit right in.