The 802.11d specification is similar in most respects to 802.11b. The main difference is that the configuration can be fine-tuned at the Media Access Control layer (MAC layer) level to comply with the rules of the country or district in which the network is to be used. Rules subject to variation include allowed frequencies, allowed power levels, and allowed signal bandwidth. The specification eliminates the need for designing and manufacturing dozens of different hardware solutions, each for use in a particular jurisdiction. The 802.11d specification is thus well suited for systems that want to provide global roaming.
The 802.xx Fast Reference lists related specifications and provides a link to each of them.