Résumé:
In this dissertation we treated the adaptive modulation problem for a time-varying and
frequency selective channel when the channel state information is imperfect. The
imperfections of channel state information are due to errors in channel estimation or in delay
caused by the Doppler spread. By using a uniform power allocation of every sub-channel, the
non linear problem considered was to maximize the spectral power efficiency and keeping the
same targeted instantaneous bit error rate for all subchannels. Furthermore we compared
different scenarios such as adaptive and non-adaptive modulation in order to know how to
efficiency adapt the modulation. The simulation results show how it is important to underload
the system when errors in channel state information are detected.
Keywords : OFDM, Channel capacity, Spectral efficiency, Adaptive modulation, Bit allocation.
