  In this paper, introduced below are the concepts of digital modulation used
in many communication systems today. Techniques described include quadrature
phase shift keying (QPSK) and quadrature amplitude modulation (QAM) and how
these techniques can be used to increase the capacity and speed of a wireless
network. These modulation techniques are the basis of communications for
systems like cable modems, DSL modems, CDMA, 3G, Wi-Fi* (IEEE 802.11) and
WiMAX* (IEEE 802.16).
