治安
In the United States, the 4.9 GHz band is reserved for use by public safety wireless applications. The transmission mask is narrower for the public safety band than for consumer part 15 applications. Thus one cannot simply operate 802.11j equipment in the public safety band and be FCC compliant. Public safety agencies are working with manufacturers and the FCC in order to leverage commercial off-the-shelf (COTS) equipment. there were public safety groups working closely with the manufacturing community, federal interests, and standards bodies to create an 802.11 series standard for public safety.