  Antenna selection (AS) is regarded as one of the most prospective
technologies to reduce hardware cost but keep relatively high spectral
efficiency in multi-antenna systems. By selecting a subset of antennas to
transceive messages, AS greatly alleviates the requirement on RF chains. This
paper studies receive antenna selection in single-input multiple-output (SIMO)
systems, namely the antenna-selection SIMO (AS-SIMO) systems, from the
perspective of digital modulation. The receiver, equipped with multiple
antennas, selects an optimal antenna subset to receive messages from the
single-antenna transmitter. By assuming independent and identical distributed
(i.i.d) flat fading Rayleigh channels, we first analyze the input-output mutual
information, also referred as symmetric capacity, of AS-SIMO systems when the
modulation style is BPSK/QPSK/16QAM. To reduce the computation complexity of
the capacity, closed-form approximated expressions of the symmetric capacity
based on asymptotic theory are given for the first time to approach the exact
results. Compared with the conventional derivations, our approximation holds
much lower computation complexity with the guarantee of high precision. Next,
this asymptotic approximation technique is extended to estimate the symbol
error rate (SER) of antenna-selection SIMO systems and approximated expressions
for SER are proposed which indicates much lower complexity. Finally, a special
scenario of single-antenna-selection is detailedly investigated and series
expressions of the symmetric capacity are formulated for the first time. Beside
analytical derivations, simulation results are provided to demonstrate the
approximation precision of the derived results. Experiment results show that
the asymptotic theory has a remarkable approximation effect.
