What is 4x4MIMO, I hear you ask? MIMO stands for Multiple Input Multiple Output and 4×4 indicates four transmission and reception streams. The reason this is interesting is because no commercial smartphone has supported 4×4 MIMO – apparently until the Galaxy Note 7. While still unconfirmed, the Note 7 apparently has the four antennas 4×4 MIMO needs for faster and more stable connections with higher data transfer rates and better efficiency.
The revelation came when a Redditor someone shared an engineering screen showing the tell-tale line ‘4RxD’ which roughly translates to four-way receive antenna diversity. If that still makes no sense, it means the Note 7 looks to have twice as many antennas as normal smartphones. This means the presence of hardware support for 4×4 MIMO, which is evidently still being field-tested.
What is 4×4 MIMO?
According to Quantenna, MIMO systems “offer superior data rates, range and reliability without requiring additional bandwidth or transmit power”. What this means for connection performance is this: “A 4×4 MIMO system with dynamic digital beamforming and MIMO receiver processing supports two maximum-rate data streams, 99 percent of the time.”
If all of that sounds a bit complicated, focus on the “two maximum-rate data streams, 99 percent of the time”. Or as one Redditor put it “20MHz markets would go from 150 Mbps to 300 Mbps. If it has 256 QAM, then add 33% for about 400 Mbps peak speeds.”
20MHz markets would go from 150 Mbps to 300 Mbps. If the Note 7 also has 256 QAM, then add another 33% for about 400 Mbps peak speeds.
This is what has everyone over on Reddit all in a tizz, because the Note 7 looks to be the first commercial smartphone to be available with 4×4 MIMO. It’s not necessarily the kind of thing you want to jam into a press conference – the previous few paragraphs should tell you why – but it is pretty exciting news.
Why is 4×4 MIMO something I want?
Simple: when optimum conditions are met, the Galaxy Note 7 would be capable of downloading data at double the normal rate. This would then allow the CPU and other resources to idle down more quickly, saving you battery life as well. In poor reception areas, four antennas would maintain a more stable connection for calls as well. Various other benefits – of varying degrees of complexity – were also discussed in the Reddit thread.
The Note 7 on which 4×4 MIMO was discovered was T-Mobile branded, but T-Mobile’s cell towers currently only support two network layers. Ideally, both the transmitter (cell tower) and receiver (smartphone) would support four layers, although two-to-four still works. It must be noted though that Samsung still needs 4×4 MIMO certification for the Note 7 (which wasn’t mentioned in the original FCC documents).
Support for 4x4 MIMO is only found in the Qualcomm X12 LTE Modem in the Snapdragon 820.
While 4×4 MIMO will work on other carrier networks as well, the radio that supports 4×4 MIMO is only found in the Qualcomm X12 LTE Modem. The Snapdragon 820 includes this modem, but the Exynos-equipped Note 7 variants do not.
Of course, we cannot confirm the Note 7 actually includes the four antennas required until someone does a hardware teardown (which won’t be long).
To release the full potential of 4×4 MIMO, both the carriers and Samsung would need to enable support for four spatial streams on both the transmitter and receiver. T-Mobile has already indicated that this would happen in 2016 and all Samsung would need to do is send out an OTA update enabling the feature.
The possibility of more stable cell phone connections, better reception in areas with a weak signal, up to double the download speeds and general efficiency improvements, all adds up to a big win for Samsung. But we can’t help but wonder why no public comment has yet been made regarding field-testing 4×4 MIMO for the Note 7 or a timeline discussed for its release.
We’ve reached out to Samsung for details on its plans for 4×4 MIMO and will update this post with any further information we receive.
Would this convince you to buy a Note 7 over another phone? When do you think full support will roll out?