Kumu and Artemis challenge assumptions about the radio network

Two start-ups which have been promising fundamentally new approaches to network performance have announced progress on their designs. Five-year-old Kumu Networks has announced a chip to support its implementation of full-duplex technology, which allows a radio to transmit and receive signals on the same frequency at the same time, doubling capacity. And Artemis Networks is targeting 600 MHz white spaces to drive its pCell, which claims to boost spectral efficiency by creating a personal cell of coverage around a user, dynamically and on-demand.

Kumu’s chip is still in the early design phase and is expected to tape out at the end of this year. It could help the company convince the market that full-duplex – which is also being pursued by several other start-ups and research projects – is real and deployable. That could also help it influence the standards which are development for full-duplex in 3GPP and CableLabs.

Kumu has raised $55m to date and has 20 patents for its interference cancelation technology, which enables full-dupex and has been tested by Deutsche Telekom, Israel’s Cellcom and others. Now it will make an RF CMOS chip, manufactured by Globalfoundries, which will be 50mm2 in size and will consume up to 2W of power. It will be targeted at WiFi access points and LTE base stations.

The chip could deliver as much as 132 dB in noise cancellation, about half of it in the analog domain, says Kumu. That could enable a 5 GHz WiFi access point to quadruple the number of channels it supports, said Joel Brand, VP of product management.

Kumu addresses the interference issue by connecting a smart echo-canceller in place of the usual RF rx/tx combiner/splitter in a standard base station. The Kumu radio generates an additional signal that cancels out the interference – a different approach to established interference cancellation techniques, and one which could be applied to cellular networks or to WiFi.

According to Kumu, the system is constantly scanning the radio environment, gauging the state of the airwaves at any given time, as well as the way the transmission is changing the signal environment at the receiver. Its algorithms then compensate for those changes as the signals arrive from the opposite direction, in effect applying echo cancellation to radio waves.

CableLabs has decided the next generation of its DOCSIS standard will support full-duplex at the cable modem termination unit, and Cisco is believed to have contributed algorithms to that effort. The 3GPP is evaluating full-duplex as a possible element in Release 16, the second wave of 5G standards. It has examined simulations that showed 70% capacity increases for base stations, and Cellcom says it achieved 50% increase using Kumu’s technology in an LTE network in 1.8 GHz spectrum, relaying signals over 1,350 meters in a residential neighbourhood.

Kumu has investment from Deutsche Telekom, Swisscom, Verizon and Cisco, among others. In October 2016, DT conducted the world’s first public operator trial of self-interference cancellation, a technology which has been defined as a Technology Building Block for 5G by the NGMN Alliance. DT said SIC technology could be used in existing networks and potentially solve small cell issues by using the same spectrum for access and backhaul. Spare macrocell capacity created via this approach could be harnessed for backhauling nearby small cells, dividing the full 100Mbps of capacity in the macro sector between several metrocells, which would not need their own backhaul, and could also act as relays. In this scenario, the small cell would need to implement the special receiver but no special handsets or macrocells would be required.

The operator’s 5G:haus research arm conducted the tests in Prague, Czech Republic, with Kumu, to determine whether SIC could enable full-duplex communication, and whether that would remain robust and stable in real world conditions.

However, there are downsides to full duplex – limited coverage, and interference risks despite SIC. Researchers at New York University Tandon School of Engineering and Trinity College, Dublin last year proposed a hybrid technology which would address these issues. Shivendra Panwar, professor of electrical and computer engineering at NYU Tandon, says full duplex networks create higher levels of interference, despite SIC and this leads to “many more outages and dropped calls”. The researchers believe the advantages of both systems could be realized with a hybrid network that mixes full and half duplex cells. Carriers could then optimize their networks to meet their particular levels of demand and spectral efficiency without excess interference.

Kumu is just one company which is leveraging interference to improve performance and spectral efficiency. In June, GenXComm raised seed funding for its own full-duplex development, while MimoTech is another pioneer in this area. Magnacom proposed a new modulation technology, WAM, to improve on QAM, and was acquired by Broadcom. And Artemis emerged in 2014 with its technology to harness interference with distributed antennas to create pCells.

Now Artemis has obtained a Special Temporary Authority (STA) from the US FCC to demonstrate its technology in vacant channels in the 500 MHz band at Mobile World Congress Americas (MWC-A) in San Francisco in September.

The company will use the white space TV channels 22 and 24—518-524 MHz and 530-536 MHz—to demonstrate its digital modulation technique, and will clearly be highlighting the implications for winners of 600 MHz spectrum in the recent incentive auction. Artemis is using channels in the 500 MHz band because the 600 MHz channels in San Francisco are still being used by TV stations.

Artemis founder and CEO Steve Perlman told FieceWirelessTech: “They’re going to see that 600 MHz is not simply a coverage band. [With pCell], 600 MHz is a high density band that cuts through buildings like a knife through butter.”

Earlier this year, the start-up introduced the pWave Mini, a 15mm-wide base station that can be daisy-chained into cables, for deployment on rooftops and along buildings or streetlights. This dramatically shrunk the size and cost of its technology, to slash the cost of entry to mobile networks for new entrants such as cablecos – or Artemis’s trial partner Dish Network, which showcased pCell on its stand at the Consumer Electronics Show (CES) in January.

Artemis is currently leasing H-Block mobile spectrum from the satellite TV provider to support pCell LTE trials, and live pCell demonstrations were staged by Dish in Las Vegas. It has also worked on tests with Nokia.

Tom Cullen, Dish’s EVP of corporate development, said at CES: “We are investigating 5G options for our spectrum portfolio, which includes the support of pioneering endeavors like Artemis.”

The pCell is seen as a breakthrough in densification because, rather than avoiding interference like conventional wireless technologies, or waiting in line to use spectrum, the technology exploits interference, combining the interfering radio waves to create an unshared personal cell (a pCell) for each device, providing the full wireless capacity to each user at once, even in extremely high density situations.

In a white paper released last year, Artemis detailed how it achieved multi-gigabit services with sub-millisecond latency and it also ran a video demonstration transmitting at 800Mbps to multiple phones next to each other in a 20 MHz piece of spectrum. The system requires a single virtualized LTE hub, which acts as a software defined radio, driving up to 32 radio antennas which can be placed just about anywhere in the target area. It works well in stadiums and conference centers, where Nokia conducted trials in 2015.

Jim Chiddix, former Time Warner Cable CTO, is an Artemis advisory board member and has said of the pWave Mini: “Reducing high density 5G wireless deployment to standard cable deployment with the pWave Mini is a game-changer for both mobile and fixed wireless,. Now, any ISP—from the largest to the smallest—can rapidly deploy high density pCell 5G LTE and fixed wireless by using well-established cable deployment practices.”

The new iteration of pWave can support multiple protocols and work in unlicensed or licensed bands from 600 MHz to 6 GHz. It promises to deliver over 50 times better spectral efficiency than current LTE on smartphones and to support costs of under $100 each at volume, potentially ushering new entrant service providers into the mobile world with far lower cost of entry (which will certainly be of interest to Dish).

As well as Dish and Nokia, it is interesting that Webpass, the fixed wireless ISP acquired last year by Google, has deployed pWave in some markets.