UEP with Adaptive Multilevel Embedded Modulation for MIMO-OFDM Systems

In this paper, a scalable multimedia system with unequal error probabilities (UEP) is considered. A combination of adaptive modulation and hierarchical (embedded) constellations is implemented to realize three different levels of data priorities. The highest priority data bits spread over all available subcarriers with a relatively low modulation order. The next data levels are embedded on top of each other, according to the given channel gain, forming varying multilevel hierarchical constellations. An arbitrary margin separation is considered between the classes, however the highest priority data should be granted a certain maximum symbol-error rate (SER). The given data rates are allocated adaptively using an optimum bitloading algorithm. In case of channel feedback errors, our algorithm performs very close to the ideal case, keeping the high priority data even safer. Moreover, the low-complex bit-loading algorithm makes the UEP adaptation concepts suitable for future wireless systems with limited feedback.