The IEEE standard802.11af uses the digital dividend. These are the frequencies freed up by the digitization of television, the white spaces, for WLANs. In Germany, this is the frequency range between 790 MHz and 862 MHz. As a further frequency range, the Federal Communications Commission( FCC) has released the frequencies between 470 MHz and 710 MHz.
802.11af and 802.22 use the available frequencies with cognitive radio in an extremely frequency-efficient manner while avoiding interference with other transmission frequencies of analog television or radio microphones. The physical layer of 802.11af is based on OFDM multiplexing as specified under 802.11ac. The advantage of this frequency range over the 2.5 GHz range is the lower attenuation of the carrier frequency by walls or other solid material. The frequency channels are 6 MHz to 8 MHz wide and can be bundled in groups of four. Multi- user MIMO( MU-MIMO) is used to increase the data rate.
The data rates depend on the modulation method and the Modulation and Coding Scheme( MCS). They range from 1.8 Mbit/s with two- phase shift keying(BPSK) and a channel width of 6 MHz to 35.6 Mbit/s with quadrature amplitude modulation (256QAM).