802.11n Interface

This chapter discusses features of medium access control (MAC) layer, physical layer convergence procedure (PLCP) sub‐layer, and physical medium dependent (PMD) sub‐layer. It also discusses management frames in the MAC layer. The management frames indicate that the access point has an 802.11n interface by including the high throughput (HT) capabilities information element, which is included in BEACON frames so that mobiles can determine that the 802.11n interface is available. The block acknowledgment mechanism is initially optional, but the efficiency gains coupled with the aggregate frame transmission resulted in BlockAck control frame support being required for the 802.11n interface. For the 802.11n interface, the block acknowledgment mechanism can be compressed, thus only processing the sequence number. The 802.11n interface operates in the Unlicensed‐National Information Infrastructure (N‐NII) band, at 5 GHz, as the 802.11a interface, and in the Industrial, Scientific and Medical (ISM) band, at 2.4 GHz, as the 802.11 g interface.