Constellation rearrangement for 4-PAM repetition coding

In fading channels to get diversity gain, transmitted data can be repeated in time or frequency. Constellation rearangement can be used instead of using the same signal constellation for each repeated transmission. In this method, symbols and the points in the signal space can be chosen differently for each one of the diversity branches. On the other hand, power allocation is another method that improves the performance. In this paper, repetition coding that uses signal constellations of 4-pulse amplitude modulation and signal constellation rearangement are compared for both fixed and optimal power allocation. It is observed that most of the gain is due to constellation rearrangement and advantages of power allocation are limited.