2×2:2, 3×3:3, What do these mean?

It’s common to see access points described with 2×2:2 or 3×3:3. Or 4×4:4, for that matter. Some now even go up to 8×8:8. What does that mean, and how important is it in deciding on which access point is right for me?

The first number represents how many transmit antennas the access point the second is how many receive antennas. The third number refers to the number of spatial streams. In other words, the number of independent wireless data transmissions that go over the antennas on the same channel. These spatial streams are fundamental to MIMO (multiple input, multiple output) antenna technology.

As an example, the Aerohive AP245X is 3×3:3. This means that it has 3 transmit antennas and 3 receive antennas, with 3 spatial streams.

MIMO takes multiple copies of the same data signal and transmits them through physically distinct paths. They go to a receiver which recombines the signal from the various streams. So our Aerohive is capable of transmitting and receiving 3 simultaneous streams of information on a single channel.

However, the numbers should not be confused with the number of radios inside the access point. Inside the device there are two radios – one for the 2.4 GHz transmissions, and one for the 5 GHz transmissions.

How is a 3×3:3 AP better than than a 2×2:2 access point?

The more antennae an access point has, the more spatial streams it can handle at the same time. The greater number of spatial streams allows the access point to deliver more data over the air at the same time. This increases the bandwidth (data rate) the access point can deliver.

Depending on the radios in the client device, you can get more spatial streams to the client device, meaning more throughput. With the latest Wi-Fi6 gear you can achieve 1.2Gb (2x600Mb) on a 2×2:2 access point radio compared to 1.8Gb (3x 600Mb) on a 3×3:3 (on the 5Ghz radio).

The greater number of antennas helps improve signal link quality and reliability. It does this through a technique called spatial diversity. Because the antennas are physically separate from each other, each antenna sees a slightly different copy of the signal. The signal seen by one antenna may be slightly imperfect in one area of the transmission while the other antenna may see it perfectly. This is especially significant in environments where the RF environment is less than ideal due to site geometry, building materials, and interference. It’s sort of like triangulation.

Also with an access point having a higher number of spatial streams, the access point can communicate with more devices at the same time. This means improved performance in highly congested areas, with the ability to handle more clients request at the same time.

Would a 3×3 device make a difference if the client device is a 1×1?

As a matter of fact, it would. In such a case, there are no MIMO gains from the additional spatial streams. But there are still performance advantages with a 3×3 access point.

First of all, the 3×3:3 device knows that it is only transmitting to a 1×1 client. So it uses the leftover antenna chains to break up and transmit blocks of data. This ensures that the client device can reconstruct the original signal, even if parts of some streams disappear during transmission. This goes by the name Space Time Block Coding.

Secondly, even though a 1×1 client can only send 1 stream, that single stream bounces off walls, furniture, and other objects. It then arrives at the access point’s three receiving antennas as separate signals. The access point uses the same signal recombination algorithm to take the signal received on each antenna chain. Then, it pieces together the original data signal by combining the strongest segments from each chain.

In a real world environment, you could see a 14 to 34% throughput improvement when these features were enabled.

Now, if you have any other questions about access points, you can email us or call Corporate Armor at 877-449-0458. We have years of experience guiding our customers to their ideal access points from top names like Aerohive, Meraki, Fortinet, Aruba, and more. Thanks for reading!