In 2014, the FCC instilled some new rules regarding frequencies in the atmosphere. This regulation change directly effected Cisco AP's. For so long, we have been able to get the "A" domain AP's, but if you have tried to order a new AP recently, you may have noticed you received a "B" domain AP. This has caused some Network Admins headaches as it can mean for a disruptive upgrade in their wireless network should they be using their Cisco wireless Access Points in conjunction with a wireless controller. You have to update your wireless controller to accept the latest iOS versions of the -B Regulatory domain APs if it is not currently ready. I ran into two customer's networks where this was the case already. The "A" APs are still order-able by Cisco, but Cisco is no longer shipping the "A" APs, they are shipping the "B" APs. So it comes as a little bit of a shock to some Network Admins when they put their newly ordered APs into the network only to find that its not working, they are not the right regulatory domain they ordered, and that they have to do a controller upgrade.
Here is an explanation of why Cisco switched to no longer shipping the "A" regulatory domain APs.
Why did Cisco move from “A” Reg Domain to “B” Reg Domain?
- In 2014 the FCC Announced a Rule Change that affected
the U-NII Bands ( 5 GHz).
- In 2012, the FCC open up Channel 144 for use in 802.11.
(However, not many manufactures of endpoints or APs updated their
equipment to support this channel at the time).
I.
The new “-B” regulatory domain:
- Adds channels 120, 124, and 128 in response to the 2014
rule Change.
- Adds channel 144 in response to the 2012 rule change.
- Allows the use of U-NII-1 band for indoor and outdoor
use (previously only indoor only)
- The change in U-NII-1 band also allowed for increased
power usage in this band.
(from 50 mW à 250 mW for client device; 1 W for AP)
Ø These changes require
actual changes in the hardware to be able to broadcast on these frequencies and
at this power rating.
Ø I fully expect all APs
moving forward that support 5Ghz to operate in the “B” regulatory domain if
deployed in the US.
II.
Primer on UNII Bands
- Currently 4 sets of UNII Bands:
· UNII 1 (Channel 36-48)
(5.180 to 5.240 GHz, 4 channels)
· UNII 2 (Channel 52-64)
(5.260 to 5.320 GHz, 4 channels)
· UNII 2e (Channel 100-144)
(5.500 to 5.720 GHz; 12 channels)
· UNII 3 (Channel 149-165)
(5.745 to 5.825 GHz; 5 channels)
- Each Band is a set of frequencies, and each band has a
different set of requirements for Tx (Transmit) Power and EIRP (total radiated
output from AP).
- The Increase
in the number of channels means that we can use more 40 MHz, 80 MHz, and MHz wide channels that do not overlap.
- The wider
channels are how 802.11ac Wave 2 can achieve such a high data rate
compared against 802.11ac Wave 1. (Wave 2 supports 80 Mhz and 160
MHz channels).
III.
Channel Width Primer
- Wider channel
means a higher potential data rate (the connection between the wireless
devices and the APs). (Think about a two lane road vs. a massive
interstate).
- Non-overlapping
channels mean that the same devices are not contending for the same
airspace.
- A single RF
channel represents a contention space. Any device broadcasting on
that channel (even if it is a neighboring AP on a totally different
network) all content for that same airspace.
- 5 Ghz channels
are separated by 20 MHz channel width. (So combining channel 36 and
channel 40 gives you a 40 MHz wide channel).
- Channels must
be contiguous (in a row) in order to channel-bond to a wider channel.
IV.
Non-Overlapping Channels
- The new FCC
regulations have allowed more channel availability for the 5 GHz
spectrum. This was done to alleviate the overcrowding that is
already occurring (similar to the way 2.4 GHz band already has
overcrowding).
- This, by
proxy, also allows for high potential data rates. Higher data rates
means that the medium (the RF space) is available more often than
unavailable. (Only a single device can talk on a single channel at a
time. It’s physics 101: two devices cannot occupy the same space at
the same time).
- Higher
availability of the medium is the true metric of a wireless network, not
data rate, throughput, or bandwidth.
V.
Channel Count by Width (See Picture Above)
- 20 MHz Wide
Channels
25 available
- 40 MHz Wide
Channels
12 available
- 80 MHz Wide
Channels
6 available
- 160 MHz Wide
Channels
2 available
- If the FCC
rules had not changed:
1.
1x
- 160 MHz Wide Channel
2.
5x
– 80 MHz Wide Channel
3.
This
would make Wave 2 almost impossible to deploy at full data rates
4.
New
channels are being proposed which are indicated in RED.
VI.
Data Rate vs. Throughput
- Wireless is
half duplex. A device can Rx (receive) or Tx (transmit), but not at
the same time. It can also not send and listen at the same
time. It can do a single action at any given moment.
- Data Rate –
The “wire” (connection speed) between the device and the AP. For
instance, my average data rate at home is somewhere around 300 Mbps
between my iPhone and my AP).
- Throughput –
The actual speed of the data going over the wire.
(In a wired, full duplex network,
throughput and data rate usually are equal).
- Aggregate
Throughput – How much actual data the AP is bridging from the wireless
connection to the wired one. (An AP is essentially a device that
bridges these two mediums. Multiple devices can be connected to an
AP at any given moment).
VII.
Actual Speeds (Throughput)
- 802.11 a/g has
a max data rate of 54 Mbps.
1.
Due
to overhead and media access methods, actual throughput is no greater than ½
the max data rate.
2.
This
means that with a perfect wireless connection, your max throughput is about 23
Mbps.
- 802.11 n has a
max data rate of 450 Mbps.
1.
Due
to overhead and media access methods, actual throughput is not greater than
60-70% of max data rate.
2.
This
means with a perfect wireless connection, your max throughput is closer to 270
Mbps).
- 802.11 ac Wave
1 has a max data rate of 1.3 Gbps.
1.
Due
to overhead and media access methods, actual throughput is not greater than
60-70% of max data rate.
2.
This
means with a perfect wireless connection, your max throughput is closer to 780
Mbps.
- 802.11 ac Wave
2 has a max data rate of 3.5 Gbps (the official spec actually calls for
nearly 7 Gpbs, but we simply cannot shove any more radio chains into
current devices. The maximum we have seen is 4x4:4 where the spec
calls for 8x8:8).
1.
Due
to overhead and media access methods, actual throughput is not greater than
60-70% of max data rate.
2.
This
means with a perfect wireless connection, your max throughput is closer to 2.
Gbps
3.
This
data rate is only achievable:
a.
with
a 160 MHz wide channel (of which there are only 2 currently that don’t overlap)
b.
An
extremely strong RSSI (signal from AP) of around -40 dBm (which essentially
requires you to be around 10 feet away from the AP)
c.
A
low ceiling or highly directional antenna to stop multi-path (reflections of the
RF signal that, depending on phase, can give you worse signal quality).
d.
A
very high SNR (signal to noise ratio) which requires an environment with very
little interference from all the various things that can cause interference on
that channel.
