Interesting article on 802.11g (aka Airport Extreme)

**binaryDigit** · May 22nd, 2003, 08:31 PM

I know that this may be better placed in the networking section, but I know that a lot of people don't venture over there unless they have problems, and this article really applies to everyone who has Airport Extreme stuff. The mods can move it if they think it is appropriate.

Anyway, the gist of the article is that the "final" draft of the 802.11g spec is being put out by the IEEE. As part of the final draft, they have decided to put in extra signaling which will drop the effective data rates. The "actual" data rates in a mixed b/g environment will be reduced to about 10Mb/s while a pure g environment will see about 20Mb/s. This is in comparison to the 54Mb/s raw rates advertised. For a pure environment, the actual rate hasen't changed much, but in a mixed environment, you won't see anywhere near the old theoretical max. It'll still be twice as fast as b in the mixed b/g and four times in pure g though, so it's still an improvement.

http://www.computerworld.com/mobilet...l?nas=PM-81450

**cfleck** · May 23rd, 2003, 11:50 PM

wow, i cant believe no one replied to this yet. i wonder if apple will be "redoing" their extreme stuff to make it standards compliant now.

i think the new standard pretty much sux. to drop the transfer rate that low after so many companies have already release higher-octane ones seems silly. i'm waiting on a new 15" pb and (assuming extreme is built in) i'll be dissapointed if it has the throttled back version of g.

**MisterMe** · May 24th, 2003, 08:13 AM

This has by now been covered extensively elsewhere, but the slowdown is minimal--2 Mbps max in the real world. The 54 Mbps number is a maximum theoretical rate. In real world applictions, you can expect a little less than half that. The same is true of the real world data rate of 802.11b aka Airport and Wi-Fi. This is also true of 802.11a. Only with 802.11a, you get substantially less range than with 802.11g. This story is about like announcing in banner headlines: "THE GROUND IS DIRTY."

**Captain Code** · May 24th, 2003, 10:37 AM

The datarate of g is still 54Mbps. But you will only get 20 usable Mbps in an all g network because the rest of the bandwidth is used by overhead of the protocol.

It seems like all the IEEE wanted to do is advertise the real-world bandwidth you'll see, instead of the theoretical limit of the technology.

**TommyWillB** · May 24th, 2003, 12:26 PM

Originally posted by binaryDigit
...It'll still be twice as fast as b in the mixed b/g...

Am I reading this right? In a mixed mode g will operate at 2*b?

If that's true then it is a 2 fold improvement over what Apple is doing now.

Currently the entire network slows down to 1*b as soon as a single b enters the network. So being able to have b&g coexist with g running at 2x is GOOD!

**binaryDigit** · May 24th, 2003, 04:57 PM

Originally posted by TommyWillB
Am I reading this right? In a mixed mode g will operate at 2*b?

If that's true then it is a 2 fold improvement over what Apple is doing now.

Currently the entire network slows down to 1*b as soon as a single b enters the network. So being able to have b&g coexist with g running at 2x is GOOD!

That's what this change is supposed to address. The "slowdown" is due to extra overhead introduced to deal with mixed b/g environments. Todays equipment handles it by just forcing everything to b when a single b client is present. Once everyone updates their firmware, the ap's should more smoothly integrate b clients. This is a similar situation when 100Mb hubs/switches first came out. Many of your cheaper 10/100 hubs would force ALL ports down to 10Mb if you plugged a single 10Mb device into it. It wasn't until later that you commonly had the ability to have each port be either speed.

**moav** · May 25th, 2003, 09:26 AM

I still think something seems fishy. It's almost as if they are doing 802.11 a a favor. Who is on the .11a side of things? If that is the case we aren't gonna be upgrading to the new firmware and I guess we'll just have to buy a few older apple extreme cards and base stations. I am sure they will still have a hidden unsupported button to click for Apple Airport Extreme Networks that will bring the speeds back up.