There is a lot of other modulation techniques... start by understanding them. You can start with Wikipedia, follow the links in the sidebar. http://en.wikipedi

There is a lot of other modulation techniques... start by understanding them. You can start with Wikipedia, follow the links in the sidebar. http://en.wikipedia.org/wiki/Amplitude_modulation http://en.wikipedia.org/wiki/Amplitude_modulation Analog modulation: AM / FM / PM / QAM / SM / SSB Digital modulation: ASK / APSK / CPM / FSK / MFSK / MSK / OOK / PPM / PSK / QAM / SC-FDE / TCM Spread spectrum: CSS DSSS FHSS THSS See also: Capacity-approaching codes / Demodulation / Line coding / Modem / PAM / PCM / PWM There are limits to how much information can be transmitted on a channel with a given signal/noise ratio. http://en.wikipedia.org/wiki/Shannon_limit http://en.wikipedia.org/wiki/Shannon_limit