What is Preamble type, when do I need to change it?
The Preamble type in 802.11 based wireless communication defines the length of the CRC (Cyclic Redundancy Check) block for communication between the Access Point and roaming wireless adapters. CRC is a common technique for detecting data transmission errors.
If your wireless devices are not using the same preamble type, they will have problems communicating. The recommended solution is setting all network adapters, access points and other wireless devices to the same type. On older wireless equipment, there may not be a manual switch for it. In that case it's either automatic or fixed to long preamble. Newer routers and access points have a preamble type setting in their web administration interface.
In essence, older equipment (802.11b/g) often uses long preamble, it is also recommended for longer-distance connections with low signal. Newer equipment/strong signals in clean wireless environments can also use short preamble.