Kumu Networks’ new chip could solve dilemma for Wi-Fi vendors at 6 GHz

The new chip that Kumu Networks is making available today for customer evaluation and testing could be used by Wi-Fi vendors looking to use the 6 GHz band when it becomes available for unlicensed devices.

Kumu just announced that the Kumu Networks KU1500-0 self-interference cancellation chip is now available for evaluation, testing and product design. The new chip, designed as the key element in a full-duplex architecture, can be used to boost the performance of existing filters or entirely replace RF filters in consumer electronic devices with a tunable solution.

Last month, the FCC unanimously approved a Notice of Proposed Rulemaking to promote the unlicensed use of the 6 GHz band (5925-7125 MHz), providing much-needed spectrum for Wi-Fi along with the existing 5 GHz band and the overcrowded 2.4 GHz band. It’s still in the comment phase, but once finalized, it’s likely that Wi-Fi vendors will want to support 2.4, 5 and 6 GHz radios in a single enclosure.

But interference between co-located radios in the 5 and 6 GHz bands could pose a problem, especially given the narrow guard band between the bands, according to Kumu, whose technology is designed to suppress the type of self-interference that would occur there. The guard band between the 5 and 6 GHz is just not enough for a normal filter to handle, according to Joel Brand, Kumu's vice president of product management. Access point vendors would “have to be very creative about how they put 5 GHz or 6 GHz in a single AP,” he said. If they try to do it with filters, “they would have to put filters on top of filters,” which leads to more problems.

This is where cancellation comes in. In the case of Wi-Fi, for example, it allows for taking 5 and 6 GHz radios and operating them side by side even if the guard band in between them is narrow, he explained.

Of course, this isn’t the only use case for the new chip. Customers with plans to test the chip include Wi-Fi chipset designers and system manufacturers, LTE base station manufacturers, and IoT system manufacturers. Testing is planned in applications including:

  • Suppressing internal interference in multiband Wi-Fi access points
  • Suppressing interference between Wi-Fi and IoT radios in the 2.4 GHz band
  • Reducing size, weight and isolation requirements for mobile base station filters
  • Reducing antenna isolation requirements for repeaters, relay nodes and RFID readers

The KU1500-0 was designed for a 2x2 MIMO radio (two transmitters interfering with two receivers). It contains 300 nanoseconds of delay elements for handling interference from RF reflections. The RFIC was fabricated using 130-nm RF SOI technology commonly used in Front-End Modules.

The next version of the chip, planned for a tape-out in mid-2019, will use the most advanced 45-nm RF SOI technology, as announced earlier this year by Global Foundries.

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One of Kumu’s goals has been to change wireless standards to full duplex, and that proposal is in front of standards bodies, including 3GPP, and there’s a track in IEEE to consider full duplex, according to Brand. “It’s certainly in discussions,” he said, but Kumu isn’t devoting a lot of effort on that front given it’s just one startup among many entities.