Routers Flashcards
What does MU-MIMO stand for, and what does it mean?
“MIMO” stands for “Multiple-Input, Multiple-Output”, and it refers to the way bandwidth is broken up by a router and pushed to individual devices.
What does SU-MIMO stand for, and what does it mean?
Most modern routers use “SU-MIMO”, or “Single User, Multiple-Input, Multiple-Output”. With these routers, only one device can receive data at any given time. This means that if you have one person watching Netflix and another watching Youtube, if you were to start both those streams at the exact same time, one device would get priority while the other had to wait until the first had buffered a few bits of data for itself.
What is the “pez dispenser” analogy for SU-MIMO vs MU-MIMO?
SU-MIMO routers can only open up one stream at a time, they do so in very rapid succession, which to the naked eye looks like a solid stream of data. To borrow an analogy, think of it like a Pez dispenser strapped to a carousel: everyone standing around the circle is eventually going to get a piece of candy, but the carousel still needs to make one full rotation before all the members of the network are satisfied.
“MU-MIMO” routers, on the other hand (“Multiple User, Multiple-Input, Multiple-Output”) are able to break up this bandwidth into separate, individual streams that each share the connection evenly, no matter the application.
What are the three “flavors” of MU-MIMO routers and what do they mean?
2×2, 3×3, and 4×4, which refers to the number of streams that they can create for each device in your household. This way, the MU-MIMO carousel can simultaneously send Pez flying in four directions at once. Without getting too technical, this is like each device getting its own “private” router, up to four total in 4×4 MU-MIMO loadouts.
What is the main benefit of an MU-MIMO router?
The main benefit here is that instead of each stream being periodically (albeit very, very briefly) interrupted by the time it takes for the carousel to spin around once, a MU-MIMO router can keep its signal constant for those four devices, and fairly distribute the bandwidth to each without compromising the speed of any of the others at the same time.
What protocol is MU-MIMO only available over currently and why does that reduce its usefulness?
Currently, MU-MIMO routers are only able to broadcast over the newer 802.11ac wireless protocol, a signal that many devices haven’t been updated to decode just yet. It also only works in 5Ghz Even fewer devices actually have MU-MIMO. As of this writing, there are a only few laptops that have MU-MIMO-ready wireless receivers, and a select number of smartphones and tablets that come with a Wi-Fi chip that knows what to do with a MU-MIMO stream (like the Microsoft Lumia 950).
What happens if you have more devices than what the MU-MIMO router is rated for?
Right now MU-MIMO tops out at four streams, which means that if you add a fifth device to the network, it will have to share a stream with another device in the same way a SU-MIMO router would, which sort of defeats the purpose.
What is the issue of MU-MIMO routers handling similarly placed devices? What is this called?
MU-MIMO broadcast signals work on a directional basis, and can only be split up when devices are in different locations around the house. For example: if you’re streaming a movie to the living room on the TV and your kids are connecting their Nintendo 3DS on the couch only a few feet away, by default both devices will be forced to share the same stream. Because of the way that MU-MIMO streams work, there’s currently no workaround for this, which means if you live in a small apartment or do most of your browsing from the same room, MU-MIMO won’t provide any extra benefits over SU-MIMO.
What are the protocol/band downsides of MU-MIMO?
MU-MIMO uses a special form of beamforming that is part of the 802.11ac standard. It works in 5 GHz only.
What are the device count rating downsides of MU-MIMO?
MU-MIMO theoretically enables up to four devices to share the same Wi-Fi airtime. Many 4x4 based designs support only up to three simultaneous devices, 3x3 designs support up to two, 2x2 designs can’t support any.
What is the compatibility downside of MU-MIMO?
You need both MU-MIMO enabled routers and devices to benefit from MU-MIMO
What is the upload/download downside of MU-MIMO?
MU-MIMO works only for downlink data (moving from router to device). It provides no benefit for uplink
What is the range benefit of MU-MIMO?
No benefit; MU-MIMO does not increase range
MU-MIMO works best with strong to medium strength signals
What is the issue with Broadcom / Qualcomm chip MU-MIMO?
Another little secret widely known by industry insiders, but by few consumers, is that Broadcom’s 2x2 MU-MIMO client-side devices fall back to 1x1 mode when connected to a MU-MIMO enabled router. This happens with both Qualcomm and Broadcom-based routers; the problem is on the client side.
How is MU-MIMO device support at this stage?
even if you load new firmware onto your AC3100/3150/5300/5400 router, it’s unlikely you’ll get decent MU-MIMO performance.
The other problem working against MU-MIMO as a useful Wi-Fi technology is that devices support it have been slow to come to market, particularly in the U.S. The first mainstream U.S. phones to support MU-MIMO were Google Nexus and Samsung’s Galaxy S6.
Both Google and Samsung continue to include MU-MIMO in their phones including 2x2 MU-MIMO in Google’s Pixel and Samsung’s Galaxy S7/S7 Edge. But if you’re an iPhone fan, Apple has yet to support MU-MIMO, and perhaps never will, at least until they settle their kerfuffle with Qualcomm. Tablets supporting MU-MIMO also still aren’t that common.
Today’s MU-MIMO
So the router end of MU-MIMO is a hot mess and support on the device end is nothing to write home about.
Test from smallnetbuilder.com showed that using MU-MIMO doesnt’ give the 3x speed that they advertise, but it does make a difference; about 23%
