Digital Audio Radio Service (DARS) refers to any type of digital radio service. In the United States it is the official FCC term for digital radio services. The most popular type of DARS in the U.S. and Canada is SDARS: Satellite Digital Audio Radio Service, operated by XM Radio and Sirius. XM and Sirius both operate in the 2.3-GHz S band, from 2320 to 2345 MHz. In areas with weak signals, such as downtown areas with tall buildings or parking garages which block satellite signals, Terrestrial repeaters are installed to re-broadcast the signal to ensure continuous coverage. Increasing the spectrum available for more services would be difficult, since unlike C-band and Ku band services, which allow over 200 locations for satellites, S-band satellites must be spaced too far apart for current technology. Existing vehicle antennas would not allow reception of two different stations on the same frequency, though new technology, requiring different receivers, might be possible. WorldSpace also operates a DARS network outside of the United States and Canada with a footprint covering Europe, Asia, the Middle East and Africa using the L-band.