The medium access control (MAC) and physical characteristics for wireless local area networks (LANs) are specified in this standard, which is part of a series of standards for local and metropolitan area networks. The medium access control unit in this standard is designed to support physical layer units as they may be adopted dependent on the availability of spectrum. This standard contains five physical layer units: four radio units, operating in the 2400-2500 MHz band and in the bands comprising 5.15-5.25 GHz, 5.25-5.35 GHz, and 5.725-5.825 GHz, and one baseband infrared (IR) unit. One radio unit employs the frequency-hopping spread spectrum (FHSS) technique, two employ the direct sequence spread spectrum (DSSS) technique, and another employs the orthogonal frequency division multiplexing (OFDM) technique.