Based on a shared physical layer approach, the DMTS-8000 software-defined multiblade radio rack system eliminates banks of discrete handsets and allows CDMA vendors and operators to optimize their equipment for maximum loads.

"It's a very competitive market and ARPUs [average revenues per user] are falling," said Steve Szabo, vice president of business development and cofounder of Dyaptive (Vancouver, B.C.). As a result, he said, operators want new sources of revenue, which implies higher data rates and quality for newer services. "But how do you benchmark quality? That's what we do."

Incorporated in 2001 and funded by venture capital in 2002, Dyaptive has been working on the problem, in collaboration with "one of the top three" CDMA basestation vendors, for three years.

The issue is important, he Szabo, because basestation vendors need reliable, cost-efficient equipment testing, while operators such as Alltel, Sprint and Verizon want to tune and optimize their basestations for loads in the field.

While CDMA is more spectrally efficient, there are more ways to optimize these networks compared to older time- division multiple access (TDMA) schemes. "CDMA has complexity in that you can trade quality, capacity and coverage," Szabo said.

New philosophy

The basic problem is density, said Dyaptive CTO Todd Sankey. "We didn't want to generate the signal of 1,000 mobiles. We wanted to generate the signal the basestation would see from a 1,000 mobiles." This required a shared physical layer that connected directly to basestation sector ports.

The result was the DMTS-8000 system that generates predictable composite signals that simulate multiple thousands of users. "It's all done digitally and mathematically," said Szabo. "Because it's software based, it can be upgraded to support new features and air interfaces and traffic can be programmed to more accurately represent actual deployments with mixtures of 2G, 3G, low-rate and high-rate users," said Sankey.

Each virtual mobile terminal has its own RF environment and behavioral model that can be programmed by the tester. "We can simulate AWGN [additive white Gaussian noise], intracell interference, multipath and fading envorinments so it looks like a real mobile and can do handoffs between basestations," Sankey said. The system can handle up to 2 million calls per hour. Current test systems generate between 3,000 and 15,000 calls/hour, said Szabo.

The initial implementation is targeted at CDMA, though W-CDMA is on the roadmap. While pricing was not available, Szabo said it's comparable with current systems, which cost $1,800 to $2,500 per phone.