Tantra Analyst

Asus Foreshadows 5G Handsets

Asus announced at Computex what could possibly be the most powerful smartphone to date. The Asus ROG (Republic of Gamers) is a beast, with features such as vapor chamber cooling (found only in gaming laptops), a Snapdragon SDM845 SoC, 8GB RAM, 512 GB storage and a slew of accessories.

The handset has the potential to redefine smartphone gaming. However, my interest in this phone is not gaming, but in one of its connectivity features called 802.11ad aka WiGig, a 60 GHz version of Wi-Fi.

This is Asus’ second attempt at .11ad. Its first .11ad smartphone, the Asus Zen 4 announced last year, only had limited availability. This announcement along with recent news about Facebook’s Terragraph trials shows continued .11ad momentum.

The significance of Asus ROG phone is not just .11ad’s multi-gigabit performance. It foreshadows millimeter wave links in future 5G smartphones, given .11ad uses the 60 GHz band. This phone provides a glimpse of the performance and design considerations of using mmwave well ahead of the 2019 timeframe for 5G handsets.

First, this phone puts to rest the fundamental question of whether it’s possible to support mmwave bands in a smartphone form factor. It also proves that all the tiny mmwave antennas Qualcomm has been showing for a long time do fit and work in a smartphone.

Typically, these antenna elements are used in groups called antenna arrays. Each array can have eight or more elements. Depending on the design, a smartphone can have up to three such arrays distributed around the device, so that beam forming can be done at all vertical and horizontal angles.

There is no clear indication on how many arrays the Asus ROG phone has. But usually, you will need at least two for good performance. 

The first 5G mmwave smartphones probably also will have at least two antenna arrays–one on the top and the other at the bottom to provide good diversity. The .11ad baseband and RF silicon are usually separate from those of .11ac/n, because of such a large difference in frequency. Similar considerations will probably apply to 5G mmwave RF designs as well.

Of course, .11ad and 5G mmwave are different technologies with somewhat different use cases. The Wi-Fi variant is primarily for indoors; 5G mmwave is for use both indoors and outdoors. Also, the cellular technology has to support mobility via cell handoffs which makes it much more complicated.

These differences will not affect similarities in how the signals propagate and behave. For example, the behavior of .11ad and 5G will be similar in terms of their inability to penetrate walls.

Both .11ad and 5G mmwave will use antenna arrays, beamforming, and beam-tracking techniques to overcome the signal loss, although techniques to implement these might be a bit complex for 5G mmwave. Both wireless nets also rely on reflections from different surfaces to provide coverage in the absence of clear line of sight.

Tests of these handsets will divulge more details. For example, it would be interesting to check non-line-of-sight performance.

Most of the demos shown so far have been with devices mounted on a cradle. The behavior of 5G mmwaves will be substantially different when the user is holding the phone.

For example, holding a handset with one hand in the portrait mode might block the antenna array on the bottom. Holding the phone with both hands in landscape mode might block both top and bottom arrays. And even if the arrays are located such that they provide good diversity, the body of the user could block signals.

I expect Asus considered these challenges and hardened the handset’s performance for many of these scenarios. I am eager to get a hold of this phone and test it out. Unfortunately, I will have to wait until the third quarter of 2018 to get a commercial phone.

One final thought: Among vendors with commercial .11ad products, Qualcomm is the only one to show it so far in a smartphone. This indicates how far ahead of the competition the company is in commercializing mmwave technology.