Overview of the five major 5G wireless technologies

Two of the five most important wireless technologies for 5G networks in 2018—multiple-input multiple-output (MIMO) and beamforming—have always been important for 5G networks.

MIMO and Beamforming

With LTE/4G, the industry is approaching the theoretical limits of time and frequency utilization. The next step for 5G wireless technology is to exploit the spatial dimension by sending tightly focused signals in different directions to use any given frequency as often and simultaneously as possible. The industry has challenges to overcome in using both technologies for 5G. Both themes have been advancing and changing in 2017, and 2018 is likely to see more on both fronts.

MIMO describes the aggregation of more and more antennas into increasingly dense arrays on both the transmit and receive sides to create more layers of data streaming, while beamforming and the closely related technology of beam tracking are about directing each signal onto the best path to the receiver while avoiding signal interference.

Beamforming will make MIMO more efficient. However, both technologies need further improvement to be applied in 5G network systems.

Figure 1 5G will rely on antenna arrays to provide mass-input and mass-output (or MIMO); beamforming will direct the signal to specific devices. (Image credit: T-Mobile)

Physically shrinking antennas remains difficult; MIMO arrays for 5G are huge (one reason actual 5G smartphones are unlikely to arrive before 2020, or perhaps later). Most existing arrays still consume too much power to be entirely practical.

Beamforming is exactly what it sounds like, but the term doesn’t capture the complexity involved. In 4G, the transmitter triangulates the receiver; this will be the case in 5G as well, but in 5G, the transmitter will also be able to map the physical environment and then calculate not only multipath bounce, but how to stagger the signal streams to exploit the multipath in a way that doesn’t interfere with synchronized signals. The task becomes more difficult when either or both the transmitter and receiver are moving.

All of this is compounded by additional technical challenges inherent in the next big aspect of 5G wireless.

Figure 2 The signal must be steered in both altitude and azimuth, complicating the task of beamforming. (Image source: Qorvo)

Millimeter Wave (mmWave)

The frequencies initially allocated for 5G are already crowded at 6 GHz. Most of the spectrum recently allocated for 5G services in different jurisdictions around the world is in millimeter wave frequencies.

Millimeter wave ranges from 30GHz to 300GHz. New 5G spectrum allocations around the world range from the 20s (such as 26GHz and 28GHz, which are not technically millimeter wave but are often classified as such), to several bands in the 30GHz to 40GHz range and several bands in the 40GHz to 50GHz range. There is a 60GHz Wi-Fi band that can be used for 5G wireless, and other higher frequencies are under consideration.

Figure 3 Spectrum near and within the millimeter wave range (30-300 GHz) is particularly suitable for higher data rates and is attractive despite its drawbacks. (Source: Ericsson)

On the one hand, these higher frequency signals will support much higher data rates than 5G specifies. The industry still has work to do to improve the spectral efficiency it has managed to achieve so far. On the other hand, the transmission rates of mmWave signals are significantly lower than expected. mmWave signals and signals below 6 GHz cannot travel very far and cannot penetrate obstacles.

In general, many components of 5G are still expensive, especially in the mmWave spectrum, but further integration will surely drive costs down as economies of scale gain momentum and based on possible future innovations.

In previous wireless network evolutions, the basic goal was to get data to the phone. Yes, this started with simple phones and evolved to add broadband access; other types of devices were supported by 4G/LTE networks, but the vast majority of wireless network usage was sending and receiving data to and from phones, but this will change with 5G. 5G will be the enabling technology for many Internet of Things (IoT) applications, but just as importantly, these IoT applications will help to justify the 5G evolution. Use cases, including IoT, are actually built into the 5G technology development roadmap, which is intrinsic to the 5G market development.

While many IoT devices will connect directly to 5G, others will not. Many IoT applications will rely on large numbers of simple, inexpensive sensors or other relatively simple devices. These devices may or may not require low power or ultra-low power, may or may not require low latency, may or may not need to communicate with each other, may generate (and possibly receive) data in quantities that vary widely from device to device, and may need to be polled constantly in real time or only once a day, week, or even month.

In many of these applications, 5G connectivity is not only technologically overkill, but also too expensive to make many of them economically viable. That’s why the next technology introduction could also be very useful for the 5G market.

Low Power Wide Area Network (LPWAN)

In many IoT applications, a large number of devices will be connected to a base station via some wireless technology designed specifically for LPWAN, which in turn will be connected to a high-speed, high-bandwidth network. That network may be 5G, but it doesn't have to be; a 4G connection is sometimes sufficient - sometimes 3G is fine. It's OK to have wired access nearby, and it may be just as useful (if not more ideal), but in many places, there is no wired network nearby, which favors the adoption of 5G network connections.

There are several LPWAN options available today. They include LoRaWAN, Sigfox, Weightless, NB-IoT, LTE-M, Ingenu, and Symphony Link. The next version of Wi-Fi, 802.11ax, has a low-power option in the specification, which may also join them.

Some LPWAN technologies are proprietary, others are the result of a more inclusive development process with varying degrees of openness. It’s too early to tell which will become popular, but one thing is certain: there are more wireless options for LPWAN than the market can accommodate for long.

Mesh networking

In some IoT applications, the use of wireless transmission technology is suitable not only for connecting a large number of simple and cheap devices, but also for interconnecting them with each other. This is the world of mesh networking. Some LPWAN technologies did not provide mesh networking support at the beginning, but now almost all technologies do.

Mesh networking is not unique to LPWANs, it has been incorporated into wireless local area network (WLAN) technology. ZigBee and Thread have supported mesh networking technology from the beginning, Bluetooth has added it in the latest version, and the next version of Wi-Fi will also have mesh networking technology. The next version of Wi-Fi is called 802.11ax, also known as Max (look at "11ax" and flip the first 1 so it faces the other direction. Get it?).

Wireless mesh networks can certainly be useful in 5G. Mesh networks are not easy to do well in local area networks where all connected devices are stationary; the difficulty is exacerbated when you consider mobile devices (people walking, drones, cars). The industry is starting to work on making 5G support mesh networks.

Figure 4 Mesh networks will help interconnect devices. One possible use is vehicle-to-vehicle (V2V) communication. (Source: Michigan Technological University)