  Movable antenna (MA) technology can flexibly reconfigure wireless channels by
adjusting antenna positions in a local region, thus owing great potential for
enhancing communication performance. This letter investigates MA technology
enabled multiuser uplink communications over general Rician fading channels,
which consist of a base station (BS) equipped with the MA array and multiple
single-antenna users. Since it is practically challenging to collect all
instantaneous channel state information (CSI) by traversing all possible
antenna positions at the BS, we instead propose a two-timescale scheme for
maximizing the ergodic sum rate. Specifically, antenna positions at the BS are
first optimized using only the statistical CSI. Subsequently, the receiving
beamforming at the BS (for which we consider the three typical zero-forcing
(ZF), minimum mean-square error (MMSE) and MMSE with successive interference
cancellation (MMSE-SIC) receivers) is designed based on the instantaneous CSI
with optimized antenna positions, thus significantly reducing practical
implementation complexities. The formulated problems are highly non-convex and
we develop projected gradient ascent (PGA) algorithms to effectively handle
them. Simulation results illustrate that compared to conventional
fixed-position antenna (FPA) array, the MA array can achieve significant
performance gains by reaping an additional spatial degree of freedom.
