802.11n: High Throughput, Not Just Fast Wireless

eggboard writes "Unstrung reveals that the 802.11 working group is spawning 802.11n, a high-throughput task group to work on increasing the actual data:symbol ratio in wireless networks while also boosting speed to 108 Mbps to 320 Mbps. Most people who use 802.11a, b, or g know that actual net throughput, or the real data that's carried, is a fraction of the cited rate: maybe 7 Mbps in the 11 Mbps 802.11b flavor and 25 Mbps in the 54 Mbps a and g flavors. The goal of 802.11n is to increase speed, sure, but also to increase the percentage of symbols that don't bear overhead. The bad news: they predict 2005 or 2006 for completion."

Comments

Real speeds of 802.11

[lindsayt]

I just wanted to point out that if we accepted 11Mbps and 54Mbps as the speeds of 802.11b and 802.11a/g then we would have to call regular fast ethernet 200Mbps. 802.11b is 5.5Mbps full-duplex and a and g both are 27Mbps full duplex. It is true that the radio signals are capable of carrying 11 and 54 respectively, but half of this bandwidth is dedicated for each direction, so that the MAXIMUM one-way speed you can achieve with 802.11a/g is 27Mbps. This means that if they're hitting real-life numbers of 24Mbps (I doubt it) of data throughput, then they're doing really well - about 88% of theoretical. That's as good as you can really expect from wired networks, in terms of throughput to bandwidth ratios.

802.1x + rolling keys is secure, even with WEP

[Stan Chesnutt]

If you can find an access-point that will do 802.1x properly with rolling keys, you are in great shape, even with RC4 WEP. The WEP attacks that have been published exploit a vulnerability with poorly-chosen IV values, and if enough encrypted packets are captured, the keys can be inferred. But, if you rekey on a frequent basis, and use a "modern" implementation of WEP which avoids the weak IV values, then you will be fine. Unfortunately, I don't know which SOHO access-point devices currently support an optimum 802.1x implementation. On the client side, Windows XP SP1 does it right, and I believe that Meetinghouse has client implementations for Linux and Mac OSX.

Noop.

[mindstrm]

- Technically we call it "100baseT Full Duplex"
- The 100 refers to 100 bits/second as a maximum channel capacity, not the maximum transfer rate between two hosts. it takes multiple hosts using the channel at the same time to saturate the channel.
- Half of the bandwidth of 802.11b is NOT set for " each direction". The full amount can be used for either direction.. it's half duplex. Further, the 11mbps refers to the radio channel, not any " direction".

- Full channel usage happens with multiple hosts, not with only two. with two hosts.. just like ethernet, but the delays and wait times are larger, adn there is more protocol overhead, due to the lack of collision detection.