64QAM
64-state quadrature amplitude modulation

This digital frequency modulation technique is primarily used for sending data downstream over a coaxial cable network. 64QAM is very efficient, supporting up to 28-mbps peak transfer rates over a single 6-MHz channel. But 64QAM's susceptibility to interfering signals makes it ill suited to noisy upstream transmissions (from the cable subscriber to the Internet).

See also: QPSK, DQPSK, CDMA, S-CDMA, BPSK, VSB