An engineer calibrates microwave waveform generators Image courtesy of IBM

An engineer calibrates microwave waveform generators. (Image courtesy of IBM).

Qualcomm Builds Low-Frequency Counterpart to Millimeter Wave System

Perhaps because they remain largely uncultivated and unregulated, higher-frequency bands have filled the conversation about fifth-generation, or 5G, wireless networks. In particular, wireless carriers are trying to divert overflow into frequency bands over 3 GHz, where most cellular networks have topped out.

Loud voices in the industry are singing praise for these new wireless pastures, but many are now focusing on millimeter-wave spectrum over 30 GHz. Qualcomm, for instance, last year revealed a prototype system for testing wireless over 28 GHz channels, at the same time making Wi-Fi chips that access 60 GHz spectrum.

Now Qualcomm is filling out its technology. The company recently revealed a prototype radio that operates in frequency bands lower than 6 GHz. This is significantly closer than millimeter waves to the spectrum set aside for 4G networks.

The prototype contains a base station for testing devices with 5G capabilities, including lower latency and faster downloads. It will assist in the development of Qualcomm’s candidate for the 5G air interface. The 3G Partnership Project has already heard proposal for the standard with plans to start winnowing out ideas by early next year.

In the wireless industry, the physics of frequency bands lower than 6 GHz are more familiar than millimeter waves, which are better suited for sending data extremely fast over short distances. On the other hand, the lower-frequency bands are capable of covering a wide area, a property that defined how most 4G cellular networks are built. Huawei, for example, is a firm believer that most 5G data will continue passing through lower bands.

This makes the sub-6-GHz bands fertile ground for development. “You are able to incorporate all of the new 5G advanced wireless technologies while also being able to reuse existing macro cell sites,” Patrick Moorhead, an analyst with Moor Insights and Strategy, wrote in a column about the prototype. “This may not seem like a big deal, but it is.”

Adapting 5G to existing infrastructure has been one of the industry’s priorities. Wireless network equipment maker Ericsson is issuing 5G software updates for base stations to reduce latency, improve coverage and capacity with beamforming, and shift network resources to more intensive applications.

Flexibility is the defining feature of 5G networks, according to Matt Branda, director of technical marketing at Qualcomm. The prototype serves as another piece in what Qualcomm and other wireless companies are calling a “unified” 5G air interface. The idea is that networks will coordinate access to both 4G spectrum and higher-spectrum bands in the millimeter-wave range.

The reason is that 5G networks will handle a wide array of devices, from smartphones to connected cars to video streaming from virtual reality headsets. Many companies are working to focus millimeter wave signals into narrow beams and steer them around buildings and obstacles that can block their path to mobile devices. But these high frequency signals are likely to be more useful for wireless infrastructure rather than connecting mobile devices, according to Moorhead.

Lending support to that idea is the fact than few companies are making an entirely new air interface. Most proposals are slight twists on the 4G waveform—also known as Orthogonal Frequency Division Multiplexing—though several startups are straying in other directions.

The 5G air interface will have “a flexible framework that can scale from low spectrum bands to [millimeter wave], from macro deployments to local hotspots,” said Qualcomm’s Branda.

Qualcomm plans on using the new system along with its 28-GHz prototype, which is helping the company tuck into more advanced forms of beamforming and interference cancellation. The sub-6-GHz radio will lower latency significantly more than LTE networks and will support data rates over one gigabit per second, giving signals 100 MHz of bandwidth.

Qualcomm is demonstrating the new prototype at Mobile World Congress Shanghai this week, partnering with the China Mobile Research Institute, a wireless research lab working on 5G technology.

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