Mobile Ops Investing in Kumu's Full Duplex

The news that Kumu Networks has received $25 million in funding from Cisco and three major network operators seems to be an indication that its full-duplex technology is poised to add major spectral efficiency to existing LTE networks and future 5G ones as well. That doesn't mean a doubling of wireless spectrum capacity is right around the corner, however. (See Cisco, Wireless Ops Back $25M in Kumu Funding.)

Kumu Networks 's Full duplex technology cancels self-interference to allow a radio to transmit and receive at the same time on the same frequency -- a goal that has been pursued by many for some time now, says Gabriel Brown, Heavy Reading wireless analyst. In theory, that means twice as much data on the same amount of wireless spectrum, assuming symmetrical traffic.

Most of the work in this area to date has been in university labs, and Kumu is "one of the first to demonstrate a system that works sufficiently well to be excited about in a commercial context," he notes. "Kumu Networks is, by far, the most important full-duplex company, with key patents granted on physical layer processes."

That's why interest is high among so many operators, including the three funding companies -- Verizon Communications Inc. (NYSE: VZ)'s Verizon Ventures, Deutsche Telekom AG (NYSE: DT)'s Strategic Investments and Swisscom AG (NYSE: SCM) -- as well as others including Telecom Italia Mobile SpA (Milan: TIM), which today announced its original field test of Kumu technology in Turin, SK Telecom (Nasdaq: SKM), and Telefónica , which had Kumu's technology on its stand at Mobile World Congress in 2015 for demo purposes, Brown says.

That initial application isn't in doubling capacity of access links in wireless networks, he points out, but in enabling in-band backhaul for small cells that operate in the same frequency as existing macro cells.

"There are several use cases for full-duplex technology in 4G-LTE," says Brown. "Most promising are relay nodes for self-backhauling small cells and X2 relay nodes for the transmission of Channel State Information needed to run coordinated scheduling techniques, such as coordinated multipoint (CoMP) scheduling and joint transmission (JT)."

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In its press release, Telecom Italia says its test "enabled the self-backhauled small cell 4G with Full Duplex technology solution to be tested in a live environment, thanks to which a smart repeater is capable of transmitting and receiving a mobile signal on the same frequency, thereby doubling the transmission capacity of the network," according to the press release. (See TIM Tests Kumu's Full Duplex in Turin.)

Kumu says its work could save "trillions of dollars" by doubling the spectral efficiency of wireless networks, which today are being asked to handle the explosion of smartphone bandwidth. And, in its funding announcement, it calls Full Duplex "a foundational technology that will address some of the critical challenges facing next generation networks."

It is interesting to note that Kumu doesn't yet have silicon companies as strategic investors.

"Ultimately, the interference cancellation will go into silicon," says Brown. "The self-interference cancellation (SIC) circuits used for full duplex are still relatively bulky, power-hungry and expensive. Developers are focused on improving SIC algorithms in programmable silicon before committing to system-on-chip (SoC) designs. Over time, however, new manufacturing processes and optimized algorithms will enable greater miniaturization. The prospect of full-duplex SIC modules built in low cost small geometry silicon is very appealing, but is probably still several years away."

— Carol Wilson, Editor-at-Large, Light Reading

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