by Duco Das, Senior Marketing Manager, 5G, NXP Semiconductors
The fifth generation of cellular is the most ambitious ever, and the addition of millimeter-wave spectrum formerly reserved for military, aerospace, and research applications is essential for it to succeed. Many of the most impressive cellular use cases —autonomous vehicles, self-guided robots and drones, immersive AR/VR everywhere—will eventually call this part of the spectrum home. That’s because the millimeter-wave spectrum available for 5G provides the gigahertz of bandwidth that will allow the very high data rates and near-zero latency required to run advanced mission-critical applications to be achieved.
The cellular industry has been eyeing these frequencies for some time, but until very recently, working at such high frequencies has posed too many technical challenges. Signals at these frequencies require an unobstructed line of sight from transmitter to receiver and cannot pass through solid objects such as building materials and trees. A hand holding a smartphone can cause interference, and even high levels of humidity can hinder transmission.
However, technology has a way of evolving to meet challenges when there is a defined benefit, and the applications proposed for 5G (and later, 6G) clearly meet this requirement. In the last few years, advances in RF silicon along with a deeper understanding of channel characteristics and signal propagation have finally made the millimeter-wave region a viable option.
Some millimeter-wave deployments have either been deployed or are nearing completion, especially for Fixed Wireless Access (FWA) networks. For example, the Tampa International Airport has deployed a millimeter-wave service that lets the major wireless carriers offer 5G mobile service throughout the facility. It delivers speeds of up to 2 Gb/s while also enhancing 4G LTE performance with download speeds of up to 300 Mb/s.
We expect millimeter-wave to play an important role in the infrastructure, working behind the scenes as part of macro cell backhaul and fiber extension and as part of IoT expansions and Industry 4.0. New millimeter-wave networks will also meet the growing demand for high-speed data in densely populated and suburban areas such as city centers; in public spaces such as airports, arenas and concert venues; and large shopping malls.
5G is designed to coexist with the latest versions of Wi-Fi, including Wi-Fi 6/6E, and as users move between indoor and outdoor locations, they will likely use a mix of sub-6 GHz, millimeter-wave frequencies, and Wi-Fi. Millimeter-wave will also be an important element for Multi-access Edge Computing (MEC) that extends cloud-computing resources to support edge deployments and enables convenient, consistent service access at the edge.
Active beamforming and steering are essential for millimeter-wave operation because they vary the amplitude and phase of the transmitted signal in each antenna element to form narrow beams that can be targeted at specific areas based on traffic conditions. As this minimizes noise and interference, the connection is more direct and reliable. Beamforming also supports spatial multiplexing in which frequencies are used more than once in the network when pointing different beams in different directions. This increases capacity without having to increase the allocated bandwidth.
Also, because beamforming prevents the radio from broadcasting where signals are not needed, there is less interference for devices trying to pick up other signals. It’s part of the reason why Tampa Airport’s millimeter-wave deployment has the added benefit of improving 4G LTE operation.
To support millimeter-wave operation, 5G beamforming algorithms use several techniques, including switching, steering, and tracking, to identify reflected energy in the signal path and redirect it to alternative paths. The result is the ability to use millimeter-wave frequencies more effectively when line-of-sight transmission is not possible.
Beamforming is designed to work with radios that use MIMO (Multiple-In, Multiple-Out), a method that increases capacity by using more than one antenna to transmit and receive each packet. Antennas operating at higher frequencies can have more elements because they can be made very small. In a radio operating below 6 GHz, for example, the MIMO antenna array might use eight antenna elements. But at millimeter-wave frequencies, this can be increased to 64 or 256 (or even 1024) in a very small footprint, small enough to fit in the tight spaces of smartphones, IoT devices, and roof-mounted “shark fin” antenna units on passenger vehicles.
One of the challenges is making millimeter-wave radios more power-efficient, which has the important benefit of lower power consumption and also makes the antenna structure easier to keep cool. NXP has developed its QUBiC silicon-germanium (SiGe) process technology that balances RF output power with high linearity, efficiency, and cost. We have produced stable RF performance at frequencies across all major 5G millimeter-wave bands and currently offer 4-channel beamforming ICs for 26 GHz with the MMW9014K product and 28 GHz with the MMW9012K product.
These low-loss, high-bandwidth circuits are compact solutions for millimeter-wave applications and deliver exceptional performance for macro use cases up to and above 60 dBm EIRP. We employ package technologies for our RF front-end components to deliver the full functionality in a compact footprint that fits within the antenna grid. The overall design also demonstrates superior thermal handling and lifetime reliability in a very demanding application.
All these advancements represent just the beginning of millimeter-wave technology development, and we expect it to keep improving over time. A decade ago, this was a pipe dream, but the “defined benefits” of 5G and later generations are providing the financial and research incentives needed to spur innovation and the results are already in evidence nationwide.