July 29, 2013

When should Enterprises switch to Wi-Fi 802.11ac?

In my last blog I discussed the benefits of 802.11ac and how enterprises should start preparing for it.

Before we attempt to answer the question on whether Enterprises should switch to 802.11ac today, let’s look at the differences between 802.11ac and the current generation Wi-Fi devices based on 802.11n – which is what most Enterprises are still deploying.

Basic comparison between 802.11n and 802.11ac:

Key Features

802.11n

802.11ac

Remarks

Frequency

2.4 and 5GHz band

5GHz band only

5Ghz has less noise, and a much greater number of non-overlapping channels

However, the higher the frequency the shorter the wavelengths are. Which of course means less range, and therefore more required APs

Channel bandwidth

20 and 40 MHz

20, 40, and 80MHz and maybe 160MHz

Increased performance through wider spectrum path. However using wider spectrum reduces the number of non-overlapping channels, which is important for enterprises

(note: 160 MHz is not supported in wave-1 of 11ac)

Spatial Streams

1 – 4 Spatial Streams

1 – 8 Spatial Streams

up to 4 per client

Increased performance through “multi-lane highway ” data path between AP and each device

(note: in wave-1 only 3 spatial streams are supported)

Bandwidth per spatial stream

150Mbps

433Mbps

Almost all .11ac clients today are single-stream which is close to today’s practical 3-stream 802.11n data rates of 450Bbps

Maximum theoretical speed

600Mbps

6.93 Gbps

Speed drops exponentially with distance in .11ac

This is only theoretical, will not be achieved in reality

Realistic bandwidth

(maximum)

450 Mbps

Three stream (3×3)

~ 1 Gbps

(at close range)

This is the likely maximum bandwidth that can be achieved in an enterprise environment

Multi-user MIMO

Not available

Available, but not in first generation products

Allows a single 802.11ac device to transmit independent data streams to multiple different stations at the same time.

(Note: not available in wave-1)

Beam forming

Proprietary

Standard

Detects where devices are and intensifies the signal in their direction(s).

Modulation

BPSK, QPSK, 16QAM, 64QAM

BPSK, QPSK, 16QAM, 64QAM and 256QAM modulation

This gives higher throughput but when you are very close to the access point (within 10 ft.)

As the table above shows, many of the true benefits of 802.11ac such as multi-user MIMO and spatial streams (that are higher than 4) are not available in the wave-1 chipsets that are currently deployed with today’s 802.11ac APs and client devices. This means today’s 802.11ac devices are limited to bandwidth capacity that is similar to what is currently achievable by existing 802.11 devices. This is why most enterprises have decided to wait for wave-2. The problem is that wave-2 based APs will not be available for at least another 12-18 months.

Therefore some Enterprises are starting to consider wave-1 based APs especially for certain incremental network expansion. But it also means more APs will be required due to the mandatory 5 Ghz-only spectrum use – this means potentially more investments will be required for these APs which  are 11n-like in terms of performance. Is this worth doing?

So what should enterprises do in the meantime?  Join me on July 31 for a free webinar to discuss these issues with a panel of Wi-Fi experts from Enterasys and Henry Ford Health System

Ali Kafel is the Director of Product Marketing for Enterasys Networks and a contributor to TMCnet. Please follow him on twitter @akafel for more thoughts on this and other similar topics.

 

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