802.11AC Wave2

When 802.11AC was introduced, we found it to be the most amazing thing since sliced bread.  It was dramatically faster than 802.11N, backwards compatible, and mostly interference free.  Today, we will discuss what 802.11AC-Wave2 brings to the table and how we feel about it.

802.11AC-Wave2 – Features and Enhancements

  • Supports speeds up to 2.34 Gbps (more spatial streams) 

Pros:  Compared to 802.11AC-Wave1, which has a capacity of  1.3 Gbps, the new standard has much higher capacity for throughput.  This is due to an increase in spatial streams.  With 802.11AC-Wave2, we increase from 3 spatial streams to 4.  This translates to a 33% increase in throughput.

Cons:  Similar to 802.11AC-Wave1, most client devices implement only one or two spatial streams in order to save on power and space required for additional antennas.  Addtionally, upgrades to current network switching infrastructure is required to fully take advantage of the ~2Gbps throughput.  A high signal to noise ratio and line of sight is usually also required.

  • Supports multiuser multiple input, multiple output (MU-MIMO)

Pros:  First, we must understand that with each additional spatial stream, we gain additional throughput.  Unfortunately, 802.11AC-Wave1 spatial streams are transmitted over multiple antennas to only ONE client at a time. Let’s imagine a freeway with multiple lanes, which can accommodate all sorts of cars, even the “wide load” ones that carry mobile homes and big construction equipment.  Now, imagine only 1 car can move at a time on this freeway.  Most cars (tablets, phones, etc) only require the use of a single lane, yet they have all the lanes available to them.  As you can see, this isn’t very efficient because the other lanes essentially goes to waste.  MU-MIMO fixes this. It allows each stream (lanes) to be directed to a different one-stream client simultaneously. So potentially, three clients get serviced in the time it previously took to service one.  Qualcomm claims a 2x-2.5x performance improvement.

Cons:  Unfortunately, this feature is only available in the downstream.  Using the car analogy, imagine the efficient freeway is only available for northbound, not southbound.  This also is a fairly complex and new technology, stability in a real-world environment has not be verified yet.

  • Offers the option of using 160-MHz-wide channels for greater performance

Pros:  Channel bonding is the single biggest performance multiplier, and it is the foundation for vendors’ claims of 1.3 Gbps speeds for Wave 1, and from 2.3 Gbps for Wave 2 up to 6.7 Gbps.  To accomplish this, 802.11AC-Wave1 allows FOUR 20 MHz channels to be bonded into a single 80 MHz channel. 802.11AC-Wave2 builds on this to provide up to 160 MHz (contiguous channels and a non-contiguous 80 + 80 configuration).

Cons:  With the availability of just a SINGLE contiguous 160MHz channel, this capability is more useful in a point-to-point configuration than a corporate wireless network.  Corporate networks require a dense configuration, which would cause performance degrading co-channel intereference.  In practice, this means that when a nearby cell is using the channel, it makes the channel busy for other nearby cells on the same channel. Additionally, nearby does not only mean neighboring cells, but due to the nature of the Wi-Fi channel access method CSMA/CS, it also means that cells at a 1-3 cell distance may keep the channel reserved.

So, with everything said and done, what is NetCal’s stance on 802.11AC-Wave2?  To keep things simple again, we recommend upgrading to 802.11AC-Wave1 90% of the time to save money on client device, equipment and infrastructure upgrades costs.  As you can guess from the above information, the improvements can only be seen in very limited circumstances (backhauling, standalone, close range, line of sight, mesh nodes, point-to-point/point-to-multipoint bridges).

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