802.11n vs 802.11ac

In the continuation of a theme, we previously looked at the coverage of the 802.11ac series of Cisco APs and what difference the number of antennas makes to the coverage pattern. The question in this blog though, is what difference has the leap from 802.11n APs (3502i / 3602i) up to the 802.11ac (3702i) AP made. Has the extra antennas made any difference in the newer models to coverage? The APs were all set to the same power and the coverage checked with AirMagnet.

Cisco 3502i @ 11dBM (12.5mW)

Let’s start with the workhorse 3502i AP. This AP is a 2x3 MIMO with two spatial streams and was 802.11n only.

2.4 GHz - Primary Coverage @ -67dBi		5 GHz - Primary Coverage @ -67dBi

Cisco 3602i @ 11dBM (12.5mW)

The later model 3602i was a stop gap between 802.11n and full 802.11ac, with the option to add an 802.11ac module. This has the antennas, but not all the channel bonding available to 802.11ac. This AP has 4x4 MIMO with three spatial streams.

2.4 GHz - Primary Coverage @ -67dBi		5 GHz - Primary Coverage @ -67dBi

Cisco 3702i @ 11dBM (12.5mW)

Finally the current top end AP of the Cisco 3702i. This is Cisco's first, true 802.11ac AP, wtih 4x4 MIMO with three spatial streams.

2.4 GHz - Primary Coverage @ -67dBi		5 GHz - Primary Coverage @ -67dBi

Results

So, what practical difference has the number of antennas made to the coverage the AP is able to provide?

Between 802.11n and 802.11ac, there does not seem to be much visible change when you look at it from a coverage stand point. The real reason 802.11ac is so amazing, is how it has upgraded 802.11n, changing the theoretical datarate to Gigabits per second, depending on how it is configured. As this is Cisco's first proper 802.11ac Access Point, they have not taken advantage of all of the new technologies that ac has brought along, such as MU-MIMO, also known as Multi-User MIMO, this allows for an AP to create specified spatial streams for the users, as well as allowing a greater number of MIMO versions, bring it up to 8x8. But that is for another blog.

To conclude, the difference between Cisco's 802.11n and 802.11ac APs are not seen in coverage, but in the datarate that they can provide the user.