  Reliable estimation of users' channels and data in rapidly time varying
fading environments is a very challenging task of multiuser detection (MUD)
techniques that promise impressive capacity gains for interference limited
systems such as non-orthogonal CDMA and spatial multiplexing MIMO based LTE.
This paper analyzes relative channel estimation error performances of
conventional single user and multiuser receivers for an uplink of DS-CDMA and
shows their impact on output signal to interference and noise ratio (SINR)
performances. Mean squared error (MSE) of channel estimation and achievable
spectral efficiencies of these receivers obtained from the output SINR
calculations are then compared with that achieved with new adaptive
interference canceling receivers. It is shown that the adaptive receivers using
successive (SIC) and parallel interference cancellation (PIC) methods offer
much improved channel estimation and SINR performances, and hence significant
increase in achievable sum date rates.
