We test the first 2×2 MU-MIMO on the market.

The Killer 1535 Wi-Fi adapter was the first 2×2 MU-MIMO compatible adapter on the market when it launched earlier this year, and is only found in a few products right now. We had a chance to test it out with the recently reviewed MSI G72 Dominator Pro G-Sync laptop, using the new Linksys EA8500 MU-MIMO router. How did it perform, and just what is MU-MIMO? Read on to find out!

Killer networks certainly haven’t skimped on the hardware with their new wireless adapter, as the Wireless-AC 1535 features two external 5 GHz signal amplifiers and is 802.11ac Wave 2 compliant with its support for MU-MIMO and Transmit Beamforming. And while the adapter itself certainly sounds impressive the real star here – besides the MU-MIMO support – is the Killer software. With these two technologies Killer has a unique product on the market, and if it works as advertised it would create an attractive alternative to the typical Wi-Fi solution.

MU-MIMO: What is it?

With an increasing number of devices using Wi-Fi in the average connected home the strain on a wireless network can often be felt. Just as one download can bring your internet connection to a crawl, one computer can hog nearly all available bandwidth from your router. MU-MIMO offers a solution to the network limitations of a typical multi-user home, and in fact the MU in MU-MIMO stands for Multi-User. The technology is part of the Wave 2 spec for 802.11ac, and it works differently than standard MIMO (multiple input, multiple output) technology.  What’s the difference?

With standard MIMO (also known as Single-User MIMO) compatible devices take advantage of multiple data streams that are propagated to provide faster data than would otherwise be available for a single device. Multiple antennas on both base station and the client device are used to create the multiple transmit/receive streams needed for the added bandwidth. The multiple antennas used in MIMO systems create multiple channels, allowing for those separate data streams, and the number of streams is equal to the number of antennas (1×1 supports one stream, 2×2 supports two streams, etc.).

MU-MIMO doesn’t work differently in relation to a single connected device, rather its advantage is the ability to support MIMO with multiple devices simultaneously. On a standard MIMO router each device is essentially forced to wait its turn, and things can slow to a crawl. Multi-user MIMO takes advantage of unused data streams to allow for multiple simultaneous connections, and with most devices using far less than the available channels there would be sufficient overhead to allow fast, simultaneous use. MU-MIMO allows for up to 4 simultaneous user transmissions, and with most devices only able to use one or two of these at a time, the technology seems ideal for a home router.

With the new MU-MIMO technology Qualcomm has taken the lead in releasing products with this new standard, including the chipsets used in all of the devices in this review. The Linksys EA8500 Max-Stream AC2600 MU-MIMO Wireless-AC Smart Router uses the QCA9980 chipset to provide Qualcomm’s MU/EFX MU-MIMO wireless technology, and both the MSI G72 Dominator Pro G (Killer Wireless-AC 1535) and Dell Inspiron 15 laptops (Atheros QCA9377) used were equipped with Qualcomm chipsets, though the Killer Wireless card takes advantage of a powerful software suite as well (more on this later).

Before continuing here's a look at the specifications for the Killer Wireless-AC 1535:

  • Support for 802.11a/b/g/n/ac with two spatial streams
  • Max wireless throughput of 867 Mbps
  • Supports 20/40 MHz channel bandwidth at 2.4 GHz + 20/40/80 MHz at 5 GHz
  • Integrated Bluetooth 4.1
  • Killer ExtremeRange Technology (Tx BF, MU-MIMO, external amplifiers)
  • Lag and Latency Reduction Technology for low-latency gaming/VoIP
  • Advanced Stream Detect application detection
  • Automatic app prioritization (default highest priority to games/video/voice)
  • 4 customizable network priority levels
  • Bandwidth monitor and user-defined bandwidth limits (by application)
  • Real-time and historical performance monitoring
  • Wi-Fi analyzer (dynamically measures AP signal strength, channel usage)
  • Supports DoubleShot Pro Technology: Use Killer Ethernet and Killer Wi-Fi together for throughup up to 1.867 Mbps; prioritize traffic between Killer Ethernet/Wi-Fi; use multiple broadband connections simultaniously

Our thanks to Rivet Networks for providing the equipment for our review!

Performance Baseline

I started my evaluation of the Killer Wireless-AC 1535 by performing a simple file transfer test, and my file copied over the network to the connected MSI Dominator Pro G notebook with impressive speed.

The transfer topped out at nearly 80 MB/s, which was about the upstream limit of my PC server's rather weak onboard NIC, and I was seeing nearly 700 Mbps (of the theoretical 867 Mbps connection) from this 2×2 adapter connected to the Linksys MU-MIMO router. To make a simple comparison with a conventional 1×1 card I performed the same transfer on the Dell Inspiron 15.

With a max speed of 40 MB/s and just over 350 Mbps of bandwidth the 1×1 adapter was almost exactly half as fast with the large file transfer, and while this isn’t surprising at all considering we’re comparing single to dual-stream wireless, it at least serves to demonstrate that both adapters (and the router) were functioning properly.

Testing MU-MIMO

To demonstrate MU-MIMO I ran instances of Netperf on both laptops via 5 GHz Wi-Fi and a PC connected via Gigabit Ethernet. To pull results simultaneously both laptops were configured as servers, with the connected PC set up as a Netperf client. I ran the performance test first with MU-MIMO disabled on the router.

The most important number here is the data received, as the transmit from the PC should be about the same with all tests. Without the benefit of MU-MIMO the MSI laptop (Killer Wireless-AC 1535) averaged 255.3 Mbps received, and the Dell (Atheros QCA9377) averaged 228.7 Mbps.

Next I enabled MU-MIMO on the router, restarted Netperf on both laptops, and re-ran the test.

Results improved to 321.1 Mbps received on the MSI (up from 255.3), and 247.1 Mbps on the Dell (up from 228.7). So we definitely see an advantage with MU-MIMO, but this is admittedly an unlrealistic circumstance – how often will your wireless devices be running as servers? So to create a "real-world" demo for this technology I took the same large file (a Windows 10 iso) from the initial throughput test and placed it on both the connected PC and a Gigabit connected NAS. I then pointed each laptop at one of the copies of the file and had the laptops download them with MU-MIMO disabled first.

First I’ll list exactly what steps I took to test simultaneous transfers on these laptops with and without MU-MIMO enabled, as this was a little more complex to set up:

  • Laptops were positioned 20 feet apart to allow adequate space for beamforming
  • Each laptop downloaded an identical file from a separate device; Dell from NAS and MSI from PC server to prevent bottlenecking (both connected via Gigabit Ethernet)
  • File transfers were initiated on Dell laptop first in each test, followed by the MSI
  • The tests were repeated to verify accuracy. Screenshots from actual recorded transfer run

Dell simultanious file transfer (started 1st) with MU-MIMO disabled

The Dell Inspiron 15 began at around 300 Mbps (close to the max for this laptop without another device connected) before the MSI’s download began, finishing at the ~280 Mbps you see in the screenshot with the MSI laptop’s download underway.

So how would the Killer Wireless-AC in the MSI laptop fare during this Dell transfer? Not well, as you will see. I created a truly worst-case scenario for this laptop's adapter, and the Dell was already consuming quite a bit of the available bandwidth before the MSI began its file transfer.

MSI simultanious file transfer (started 2nd) with MU-MIMO disabled

The speed from the MSI laptop is nearly 10x below its potential as it would download at well over 650 Mbps (and 70 – 80 MB/s) consistently, with this Killer 1535 wireless card the only connected device. Another note to consider, the speeds seen here on the MSI laptop are not even close to the level they would reach if I had begun the transfer on this system first (or even simultaneously). The behavior I observed in my testing was that the 2×2 wireless in the MSI laptop took over most of the available bandwidth, leaving the Dell to single-digit transfer speeds in those extreme cases. This is why I chose to start the Dell test first, since otherwise the MSI would create a situation where there was almost zero available bandwidth.

But this was all before I enabled MU-MIMO.

After my brief testing I have to say, this new wireless tech is the real deal. While there was certainly a difference with the Netperf testing, the difference in real-world file transfers was much more impressive. While one of the laptops would have precedence on the network – causing the other to lag considerably – without MU-MIMO enabled, the results were much closer to 50/50 when the setting was enabled on the Linksys router.

Dell simultanious file transfer (started 1st) with MU-MIMO enabled

The first result here shows the transfer on the Dell laptop underway, and if you look at the Windows file transfer status there is a drop in speed at about the halfway mark when the MSI download began. 200 Mbps is a lot slower (80 Mbps slower, in fact) than the Dell was getting before MU-MIMO was enabled, so what’s happening over on the MSI at this time?

MSI simultanious file transfer (started 2nd) with MU-MIMO enabled

While not as consistent (speeds ranged anywhere from 150 Mbps to 250 Mbps) the MSI was on a much more even playing field with the Dell with MU-MIMO enabled. In fact, though the screenshot shows 173 Mbps at this particular moment speeds actually ranged most often just above or below the 200 Mbps mark – and that was for both laptops. While the Killer Wireless-AC 1535 was certainly capable of dominating the lesser 1×1 card in raw throughput, it was a testament to this MU-MIMO technology that it could still achieve equal footing with the Dell in this worst-case test.

I never saw speeds of over 700 Mbps combined with dual streams on this router, but even if we aren’t approaching what might be possible with dual 2×2 adapters (the Dell Inspiron was only 1×1) this is still a great result. To go from an inconsistent 5 – 80 Mbps on the second laptop to a consistent 180 – 220 Mbps on both is a big deal. There would be more than enough bandwidth to share a fast internet connection without penalty between two laptops, and the benefit would only grow larger with other connected devices as MU-MIMO makes use of all unused data streams with compatible clients. Four 1×1 wireless adapters would be able to connect at pretty much full speed simultaneously, for example.

Next we'll check out the powerful Killer software, and see how it changes the experience with the MSI G72 Dominator Pro G laptop.

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