The 5G Network of Tomorrow is coming to mobile broadband, and like SDN/NFV, it will generate new network operating models.While avant-garde operators will quickly adopt, further cementing their market leading positions, 5G will open the door to non-traditional network operators and infrastructure vendors for networks in unlicensed and shared licensed spectrum. Notably, the Radio Access Network will experience a major change, as the nature of 5G frequencies will change the design and operation of cellular networks.Knowing that 5G is a major change for operators with a legacy mindset, the development community is trying to deliver the maximum utility and longevity with a platform that should last for 10 years and avoid operators’ buyer remorse of “I wish we had known…”
What are the differences with 5G frequencies, and what can we expect from them? Today’s cellular frequencies range from 450 MHz to more than 3000 MHz—technical terms that have important physical and economic implications, and traditionally licensed spectrum. With 5G multi-connectivity, operators can use unlicensed spectrum for added capacity or develop isolated networks for enterprise and industrial applications.Because of the physics of electromagnetic radio waves, the lower numbered frequencies are able to reach farther and cover more area for less cost than the higher numbered frequencies. However, it is not a free lunch, because as more subscribers sign up, cell sites using the lower numbered frequencies will have too many subscribers for each base station, causing slow data rates and delivering a poor user experience. Operators can buy more radio spectrum (if available) and/or put up more cell sites, including small cells, to meet wireless broadband data demand. Smarter antenna systems will also improve network performance and capacity beyond what is capable with today’s standard 2×2 and 4×4 MIMO deployments in 4G LTE.
For cellular networks, the signal quality matters most for the user experience, and as a simple rule of thumb, a stronger signal (relative to the surrounding electronic noise) leads to a better user experience withfaster data rates.In the digital realm, blazing speed correlates with mass-market capacity, as all subscribers in a cell share the total data rate. Obtaining stronger signals with 5G involves smarter antenna technology, more radio spectrum, and smaller cells. The physics of 5G spectrum changes the economics for antenna solutions, as the higher frequencies equate to packing more antennae into a smaller space and remaining cost effective. The higher numbered frequencies are promising, because there is a lot of radio space available, which will help support a 1000x increase in traffic. Smaller cells and smart antennae offset the propagation physics that would otherwise mean a very short range and poor user experience.
5G will encompass a wide range of spectrum, but my primary interest is new frequencies above 6 GHz.At 28 GHz, for example, a single antenna, called a “half wavelength dipole,” is about 0.2 inches—not big at all.The small size spurs creative engineers to do many clever things, like beamforming.An array of antennae, say 128 elements, is still very small, but the right digital signal processing can generate a very focused beam from the base station to the mobile.This is necessary for the cellular signals to overcome the energy losses due to distance, buildings, trees, rain, or people.
At a recent 5G workshop, Qualcomm demonstrated a 28 GHz test setup with a 128 element antenna representing a base station, and a mock-up mobile with a smaller set of selectable antennae (read about the demo).The 128 element base station antenna was about 6”x8” and the ability to focus a radio beam was demonstrated under a variety of orientations. An antenna designed the same way for today’s LTE frequencies at 700 MHz would be about 20’x30’ and not feasible. An operator can hang an abundance of 6”x8” antennae in a place like Times Square, which leads back to another aspect of 5G—Massive MIMO (Multiple-Input, Multiple Output – who thinks up these names?). Massive MIMO essentially means that the network uses multiple antenna beams from multiple base stations to deliver the fastest data to your mobile.
The tiny smart antennae demonstrated by Qualcomm had about 27 db gain, about 10–12 more db than a typical cellular base station antenna. 10 db more means that antenna could put 10x more signal power on a mobile than a legacy cellular antenna. An analogy to this effect is like using a candle to light up a dark room versus using a flashlight. This focused approach also extends to the many antennae that might be deployed, that is several base stations with lots of antennae may deliver the signal to your mobile, hence Massive.The net effect is to provide you a stronger signal with less interference, or noise, from all the other mobiles nearby. The relative signal-to-noise ratio (SNR) limits how fast the network can deliver the data, and a bigger ratio is better. Beam Forming Smart Antennae makes for a larger signal value at the top of the ratio fraction, and smaller noise value at the bottom for a double boost to SNR.
A second aspect, and just as critical as the base station antenna, are mobile antennae. Qualcomm demonstrated a facsimile of a mobile, a Form Factor Accurate device, with antenna in the case edges, front and back, top and bottom.Many antennae are needed to make sure that at least some are unobstructed by your hand or other body parts. I expect that there are best practices in mobile antenna design that will come from this, so that 5G handset vendors will not have Antennagate déjà vu all over again.
A third critical aspect of a 5G cellular network will be multi-connectivity. 5G multi-connectivity means that while your network is delivering an outstanding data experience in the uber-fast 6 GHz (and higher) frequencies, it maintains additional connections with 4G LTE (Long Term Evolution – seriously, where do they get these names?). In spite of the multiple beam forming antennae that puts your device in the spotlight, there will be occasional times where the 28 GHz signal is blocked. Rather than drop off the network, the network maintains the connection through the wider coverage of 4G LTE until the 28 GHz signal returns.
The bigger picture of 5G is more than just the spectrum, antennae, anda faster-better-cheaper mobile broadband. The 5G Network of Tomorrow is about designing and operating the networks with the forethought and flexibility to last through 2030. The 5G network will bring to fruition the aspirations of the connected society, that is the Internet of Everything. Of course, none of this is simple to implement, but by connecting the dots among 4G, 5G, and millimeter wave smart antennae research, we have a good idea for key components of a 5G network. The creative geniuses at companies like Qualcomm are working diligently to make this happen.