  For a single transmit and receive antenna system, a new constellation design
is proposed to combat errors in the phase estimate of the channel coefficient.
The proposed constellation is a combination of PSK and PAM constellations,
where PSK is used to provide protection against phase errors, while PAM is used
to increase the transmission rate using the knowledge of the magnitude of the
channel coefficient. The performance of the proposed constellation is shown to
be significantly better than the widely used QAM in terms of probability of
error. The proposed strategy can also be extended to systems using multiple
transmit and receive antennas.
