  This letter presents a detailed study for indoor wireless environments, where
transmit power, rate and target bit error rate (BER) are varied to increase
spectral efficiency. The study is conducted for the recently proposed joint
fading and two-path shadowing (JFTS) channel model, which is shown to be
accurate for modeling non-Gaussian indoor WLAN environments. Analysis is done
for both average and instantaneous BER constraints without channel coding,
where only a discrete finite set of constellations is available. Numerical
results show that, for a JFTS channel i) varying only the transmission rate
(modulation constellation size) achieves more improvement in spectral
efficiency compared to varying transmit power only, and ii) varying rate and/or
power subject to instantaneous BER (IBER) constraint offers better performance
than when subject to average BER (A-BER) constraint.
