As explained in Section 1.9, in order to protect existing radio services from UWB interference, the FCC has assigned conservative emission masks between 3.1 GHz and 10.6 GHz for commercial UWB devices. The maximum allowed power spectral density for these devices—that is, –41.3 dBm/MHz, or 75 nW/MHz—places them at the same level as unintentional
radiators (FCC Part 15 class) such as televisions and computer monitors. Based on the FCC regulations, UWB devices are classified into three major categories: communications, imaging, and vehicular radar..

COMMUNICATIONS DEVICES
For communications devices, the FCC has assigned different emission limits for indoor and outdoor UWB devices. The spectral mask for outdoor devices is 10 dB lower than that for indoor devices, between 1.61 GHz and 3.1 GHz, as shown in Figures 1–15 and 1–16, respectively. According to FCC regulations, indoor UWB devices must consist of handheld equipment, and their activities should be restricted to peer-topeer operations inside buildings.
The FCC’s rule dictates that no fixed infrastructure can be used for UWB communications in outdoor environments. Therefore, outdoor UWB communications are restricted to handheld devices that can send information only to their associated receivers.

In general, the FCC ruling per application with Part 15 classification of –41.3 dBm for both outdoor and indoor operations can be summarized as shown in Table 1–3.