802.11a/g Interfaces
André Perez · 2018
The 802.11a and 802.11 g interfaces operate at the physical layer convergence procedure (PLCP) sub-layer and physical medium dependent (PMD) sub-layer. On transmission, the PLCP converts the PLCP service data units (PSDU) from the medium access control (MAC) layer to form the PLCP protocol data units (PPDU), adding a preamble and a header. The 802.11a interface operates in the 5 GHz Unlicensed-National Information Infrastructure (U-NII) band. The 802.11 g interface, called Extended Rate Physical (ERP), must be compatible with the 802.11 interface, called direct sequence spread spectrum (DSSS). The 802.11 g interface implements the functions of the 802.11a interface, except that it uses the Industrial, Scientific and Medical (ISM) frequency band at 2.4 GHz. The DSSS-orthogonal frequency-division multiplexing (OFDM) mode uses a format that includes the short or long preamble and the header of the 802.11b interface associated with the preamble and the header of the 802.11a interfaces.