Today, I am writing you about advances in “MU-MIMO.” No, this isn’t a new sushi dish that some talented sushi chef created recently. Multi-User-Multiple-in Multiple-out (try saying that fast three times) is a development that promises to put Wi-Fi on the fast track to solve the Wi-Fi issues that happen when networks get loaded up with users.
It has been around for a several years (it was added to the 802.11ac spec in 2013 but is finally catching some wind, mainly due to advances in router chipsets allowing routers to handle up to four MIMO streams (we are talking enterprise-class, 802.11ac routers for now).
Most of us are aware that Wi-Fi’s biggest bane is loading. Since the standard Wi-Fi router configuration is a serial sequencer, it can only handle one device at a time – very quickly, mind you, but it is a single task process. Even with MIMO that is true. With few users, that process is fairly transparent and speeds remain acceptable. But once it gets a lot of users, the bandwidth per user gets narrower and narrower, eventually showing up as the dreaded slow Internet. This is the Single-User MIMO (SU-MIMO) spec of 802.11ac.
So MU-MIMO alleviates that bottleneck, to some degree. It isn’t a cure-all, since it can only handle four streams maximum, but that is a 400 percent increase (theoretically). But in reality, most real-world tests show between 80 percent and 200 percent improvement in Mbps data throughput – generally sufficient to keep decent speeds in all but the most extreme loading cases. This will play well for denser, multiple-user, Wi-Fi networks. And that is not just for the commercial market. By 2020,the average home will have as many as 20, or more, Wi-Fi connected devices, according to ABI and Machine Research.
What makes MU-MIMO exciting is that it can increase performance appreciably without any modifications or changes to the basic bandwidth structure. However, the functionality is quite different.
SU-MIMO can support up to four spatial streams, scalable up to 16 dimensions. However, its biggest drawback is that it requires multiple antennas at both ends. It also places the burden of the signal processing on the client.
MU-MIMO makes the router the intelligent component. The intelligence and processing burden now takes place in the router. Signal processing is also now done in the router.
MU-MIMO also implements beamforming. That is a huge game changer because it directs transmission to the specific antenna determined by intelligent algorithms. Simultaneously, it nulls other antennas. It also has advanced signaling in the packets, which identify the MU group, the modulation used and the client’s address.
This is a nice uptick for much of the aging Wi-Fi infrastructure. As Wi-Fi use continues to expand, it will also become more congested. Incremental improvements such as MU-MIMO help to keep up with the pace. Something as simple as replacing a router is a fast and easy fix as we wait for gigabit Wi-Fi.