Although our vision for 5G goes well beyond faster peak rates, we also believe 5G should continue to deliver efficient solutions to the ever growing mobile data traffic challenge and provide extreme multi-Gbps data rates to usher in the next era of immersive multimedia experiences such as 3D/UHD video telepresence and virtual reality. Earlier this week, in a live demonstration to Industry Analysts, Qualcomm Research demonstrated a key 5G technology enabler to these extreme mobile broadband experiences—millimeter wave (mmWave).
Spectrum bands in very high frequencies such as 28 GHz, known as mmWave provide very large bandwidths capable of delivering multi-Gbps data rates, as well as the opportunity for extremely dense spatial reuse to increase capacity. These opportunities are not new—mmWave frequencies are being utilized today for applications such as streaming high-resolution video indoors with Wi-Fi 802.11ad operating at 60 GHz for example. Traditionally however, these higher frequencies were not robust enough for indoor/outdoor mobile broadband applications due to high propagation loss and susceptibility to blockage from buildings, humans, foliage, and even rain drops. These challenges made utilizing mmWave for mobile broadband not feasible due to insufficient coverage and lack of support for mobility especially in non-line-of-sight (NLOS) environments. But that is about to change…
As implied by the name (millimeter-wave), at the higher frequencies in which mmWave operates, the small wavelengths enable the use of a large number of antenna elements in a relatively small form factor. This characteristic of mmWave can be leveraged to form narrow directional beams that can send and receive more energy to overcome the propagation / path loss challenges. These narrow beams can also be utilized for spatial reuse. This is one of the key enablers for utilizing mmWave for mobile broadband services. In addition, the NLOS paths (e.g., reflections from nearby building) can have very large energies providing alternative paths when LOS paths are blocked.
The challenge for ‘mobilizing’ mmWave doesn’t end there though. To enable a good mobile broadband user experience with mmWave requires continuous intelligent beam searching and tracking algorithms to discover and switch to the dominant beam path. This dominant beam path will be constantly changing based on environment, mobility, and slew of other factors. We need a 5G design that delivers agile transfers between beam paths, as well as between different mmWave small cells. So although it may be cool to see the multi-Gbps peak rate demonstrations with mmWave, the real challenge comes in delivering a robust mmWave design that can actually be feasible in indoor/outdoor mobile deployments. Which brings me back to the live 28 GHz demonstration by Qualcomm Research earlier this week in San Diego.
The engineers at Qualcomm Research demonstrated their TDD synchronous system operating in the 28 GHz band. The demonstration included one mmWave base station and one device (or UE), although the system was designed to be able to handle multiple devices. The mmWave base station antenna design prototyped by Qualcomm Research team had 128 antenna elements with 16 controllable RF channels, while the device contained four selectable sub-arrays each with 4 controllable RF channels. Commercial base stations could have more antenna elements depending on their size, coverage area, etc. The multiple sub-array in the device forms a dynamic, directional beam, ensuring that the user conditions, such as the user’s hand position on device or the position of device with respect to the base station, would not overly impact performance.
The live demonstration showcased intelligent beamforming and beam tracking techniques that resulted in a relatively stable SNR even when the device was moved and RF channel conditions changed. The demonstration GUI clearly showed the system switching between beam patterns (both on uplink and downlink) as the environment changed. The engineers disclosed that in other measurements the system has measured line-of-sight (LOS) coverage of approximately 350 meters and also shared simulation results from an outdoor dense urban deployment in Manhattan with NLOS coverage of approximately 150 meters.
Of course, the ubiquitous coverage and seamless mobility we have come to expect with mobile broadband services will continue to rely on lower frequencies below 6 GHz, while using mmWave in the future with 5G to boost user throughput and increase network capacity. And that is why we are designing the 5G Unified Air Interface to provide tight interworking between mmWave and 5G sub-6 GHz, as well as multi-connectivity with 4G LTE access, to even further increase the robustness of the mmWave design.
The live demonstration is a big step in ‘mobilizing’ mmWave, but there is more work to be done. Qualcomm is working closely with the industry to standardize 5G technologies through the 3GPP standards organization, including ongoing activities in channel modeling for mmWave. We look forward to showcasing more details on our mmWave system at MWC in February 2016. In the meantime, you can get all the latest information on all the 5G technologies, including mmWave, from our 5G technology website.