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Say hello to my little friends!

Now we have two new 802.11 friends called A-MSDU and A-MPDU.  Their job: to make the protocol analyst's job more difficult.

A-MSDU = Aggregate MSDU
A-MPDU = Aggregate MPDU

Both can be used together, with restrictions (of course, because it's not as much fun unless you have extra rules to follow).

You can string MSDUs together - called subframes when aggregated - in the payload of a single QoS MPDU.  An A-MSDU subframe structure consists of:

DA (6), SA (6), Length (2), MSDU (0-2304), Padding (0-3) -- all of the numbers are in octets

 

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Evaluating Readiness to Support Wireless LANs

Make certain you have solid support plans, including knowledgeable staff and the correct tools, before you give a thumbs up for that new wireless network.

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Random 802.11n Observances

The 802.11n amendment allows for up to 4x4 MIMO.  That's 4 transmitters and 4 receivers working at the same time.  Due to cost, nobody is building a 4x4 system.  Instead, we're seeing 2x2 on the cheap stuff, 2x3 on the higher-end client radios and the lower-end APs, and 3x3 on the higher-end APs.  More transmitters and receivers means better quality: better reception, higher throughput, the works.  Always look for 2x3 stations and 3x3 APs whenever possible. Continue reading...

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Review of Nokia N800 for Wireless LANs

Earlier this year Nokia released an updated version of their popular Nokia N770 Internet Tablet. The N800 excels at being a small, light-weight device capable of WiFi as well as Bluetooth access to the Internet. THis is a user-based review of this great little device.

 

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Foraging for Goodies

In my daily foraging for goodies in the 802.11 standard, I tripped across what seemed to be something routine, but upon deeper inspection (the reading of several RFCs), it seems that PAP, CHAP, and MS-CHAP cannot be used between an authenticator and authentication server in an RSN.

 

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The 802.11 Frame Format: New and Improved.

When will the madness end?  With 802.11n, we have a newly elongated frame format.

Frame Control: 2 octets
Duration/ID: 2 octets
Address 1: 6 octets
Address 2: 6 octets
Address 3: 6 octets
Sequence Control: 2 octets
Address 4: 6 octets
QoS Control: 2 octets
HT Control: 4 octets (new!)
Frame Body: 0-7955 octets (yeah baby!)
FCS: 4 octets Continue reading...

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New 802.11n Features: Briefly

802.11n has many new features including Space Time Block Coding (STBC), Spatial Multiplexing (SM), Cyclic-Delay Diversity (CDD), Maximal Ratio Combining (MRC), and Transmit Beam Forming (TxBF). A great summary of these features is found in an Atheros whitepaper here: http://www.atheros.com/pt/whitepapers/MIMO_Pwr3_whitepaper.pdf

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