frederick
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I've been doing my due diligence with keeping up in the networking world. It's my background, I love Network Administration more than System Administration. They intersect a lot, but are completely different at the end of the day. So here is what I've learned about 802.11ac thanks to Fluke Networks, and taking a class yesterday on 802.11ac.
802.11ac, for those who don't know, is basically the expansion upon 802.11n. 802.11n is only capable of a 600Mbps connection, and 802.11ac is expected to to move up to 6933Mbps, that's just over 11 times more speed. What's really awesome about 802.11ac is that it greatly improves upon MIMO. As you should all know, MIMO means Multiple Streams In, Multiple Streams Out, but the problem is that while it increases bandwidth, only one machine can actually talk or listen at a time. So everyone is having to "time-share" the bandwidth. With 802.11ac, they are using what is called Multiple User MIMO now, where if I have an AP with 2 antennas, and I have two wireless devices, lets say laptops, then each laptop gets it's own dedicated stream, or antenna.
MIMO gets more intense. Each antenna is it's own spatial stream. Because of this, APs will be able to handle more connected devices than before. Even with an 802.11n AP, there is a limit to how many devices can connect before the AP becomes overwhelmed with devices, as 802.11a/b/g/n work like a Hub-Switch (my term). CSMA/CA basically states that with traditional AP's, only 1 device can broadcast at a time, giving the AP and the broadcasting device 100% of the connection (a switch), but the more devices you connect, even if they are all 802.11a for example, the slower the bandwidth actually gets because each device has less and less time to talk before the AP has to go to the next device (hub). 802.11ac defeats this by increasing the channel width, from 20MHz all the way up to 160MHz, accommodating up to 8 Antennas per AP, that all operate on the same channel, but give each antenna it's own breathing room.
Now in theory, because in all honesty it is going to be dependent on the manufacturer for this, if I have a 2 antenna AP, I have what is called a 2x2:2, or 2 transmit antennas than can also receive, creating 2 spatial streams. The THEORY here is that because I have 2 spatial streams, I can actually put all my 802.11a devices on one spatial stream, and all my 802.11n on the other, this way my 802.11n devices don't get bogged down. Now this is in theory, and can be handled by the AP without intervention. But difficult to achieve. In order for this to work properly, there has to be physical spatial separation between the 802.11a devices and the 802.11n, otherwise, they could antenna hop. Also for devices of the same standard, in order for them to be awarded their own spatial stream, there has to be physical spatial separation as well.
There is a dark side to 802.11ac however. It will only be compatible with 802.11a/n/ac devices, which means, 5GHz band only.
In the end, 802.11ac really helps to bring wireless devices closer to the quality of bandwidth that wired connections have with it.
If you have any questions, I'm not an expert yet, but I got tons of information on this.
802.11ac, for those who don't know, is basically the expansion upon 802.11n. 802.11n is only capable of a 600Mbps connection, and 802.11ac is expected to to move up to 6933Mbps, that's just over 11 times more speed. What's really awesome about 802.11ac is that it greatly improves upon MIMO. As you should all know, MIMO means Multiple Streams In, Multiple Streams Out, but the problem is that while it increases bandwidth, only one machine can actually talk or listen at a time. So everyone is having to "time-share" the bandwidth. With 802.11ac, they are using what is called Multiple User MIMO now, where if I have an AP with 2 antennas, and I have two wireless devices, lets say laptops, then each laptop gets it's own dedicated stream, or antenna.
MIMO gets more intense. Each antenna is it's own spatial stream. Because of this, APs will be able to handle more connected devices than before. Even with an 802.11n AP, there is a limit to how many devices can connect before the AP becomes overwhelmed with devices, as 802.11a/b/g/n work like a Hub-Switch (my term). CSMA/CA basically states that with traditional AP's, only 1 device can broadcast at a time, giving the AP and the broadcasting device 100% of the connection (a switch), but the more devices you connect, even if they are all 802.11a for example, the slower the bandwidth actually gets because each device has less and less time to talk before the AP has to go to the next device (hub). 802.11ac defeats this by increasing the channel width, from 20MHz all the way up to 160MHz, accommodating up to 8 Antennas per AP, that all operate on the same channel, but give each antenna it's own breathing room.
Now in theory, because in all honesty it is going to be dependent on the manufacturer for this, if I have a 2 antenna AP, I have what is called a 2x2:2, or 2 transmit antennas than can also receive, creating 2 spatial streams. The THEORY here is that because I have 2 spatial streams, I can actually put all my 802.11a devices on one spatial stream, and all my 802.11n on the other, this way my 802.11n devices don't get bogged down. Now this is in theory, and can be handled by the AP without intervention. But difficult to achieve. In order for this to work properly, there has to be physical spatial separation between the 802.11a devices and the 802.11n, otherwise, they could antenna hop. Also for devices of the same standard, in order for them to be awarded their own spatial stream, there has to be physical spatial separation as well.
There is a dark side to 802.11ac however. It will only be compatible with 802.11a/n/ac devices, which means, 5GHz band only.
In the end, 802.11ac really helps to bring wireless devices closer to the quality of bandwidth that wired connections have with it.
If you have any questions, I'm not an expert yet, but I got tons of information on this.
