802.11 bgn networks
Encryption
XBee Wi-Fi RF Module User Guide
58
The 802.11b standard was approved in July 1999 and can be considered the second generation.
802.11b operates in the 2.4 GHz frequency ISM band. The data rate is from 1 to 11 Mb/s.
802.11 g
The 802.11g standard was approved in 2003. It provides a maximum data rate of 54 Mb/s. In addition,
the standard is also fully backwards-compatible with existing 802.11b wireless networks.
802.11 n
The 802.11n standard was approved in 2009. It provides for data rates up to 300 Mb/s. The XBee Wi-Fi
module uses the single stream n mode with 20 MHz bandwidth and is capable of up to 72.2 Mb/s over
the air in n mode.
Encryption
Encryption is a method of scrambling a message that makes it unreadable to unwanted parties,
adding a degree of secure communications. There are different protocols for providing encryption, and
the XBee Wi-Fi RF Module supports WPA, WPA2, and WEP.
Authentication
Authentication deals with proving the identity of the wireless device attempting to associate with the
network. There are different methods of doing this. The XBee Wi-Fi RF Module supports Open and
Shared Key authentication in WEP mode and it only supports shared key authentication in WPA and
WPA2 modes.
Open authentication
Open authentication is when the access point simply accepts the wireless devices identity without
verifying or proving it. The benefits to this are simplicity and compatibility (all devices can do it). In this
mode, which is only available when using WEP, a connection to the access point occurs even if the WEP
key is wrong. However, no real communication can occur because of mismatched keys. If DHCP is
configured, it fails too, causing the
AI
indicator to get stuck in the
AI 41
state.
If, on the other hand, the
AP
is configured for shared key authentication, no connection occurs with an
incorrect WEP key. Instead,
AI
gets stuck in the FF state, indicating scanning. Although shared key
authentication sounds better, it exposes a big security flaw with WEP. The challenge text, its
encrypted result, and a success/failure result are passed in the clear and can easily be caught over the
air to determine the WEP key.
Shared Key
Shared Key is when the wireless devices must present the proper key to get on the network. Although
Shared Key has more security than Open authentication it should not be considered secure. One of
the benefits of Shared Key authentication is simplicity.
Channels
The XBee Wi-Fi RF Module operates in the 2412-2472 MHz range. The frequency range is broken down
into thirteen channels. Data is transmitted on a channel by radio frequencies over a certain frequency
range. In order to avoid bad performance caused by the overlapping (collision) of channel frequencies
in a wireless LAN environment, it is very important that you select the channels of neighboring access
points accordingly.