The wireless radio generates a 2.4 GHz carrier wave (2.4 to 2.483 GHz) and modulates that wave using a variety of techniques. For 1 Mbps transmission, BPSK (Binary Phase Shift Keying) is used (one phase shift for each bit). To accomplish 2 Mbps transmission, QPSK (Quadrature Phase Shift Keying) is used. QPSK uses four rotations (0, 90, 180 and 270 degrees) to encode 2 bits of information in the same space as BPSK encodes 1. The trade-off is increase power or decrease range to maintain signal quality. Because the FCC regulates output power of portable radios to 1 watt EIRP (equivalent isotropic radiated power), range is the only remaining factor that can change. On 802.11 devices, as the transceiver moves away from the radio, the radio adapts and uses a less complex (and slower) encoding mechanism to send data.