Flow-level performance of proportional fairness with hierarchical modulation in OFDMA-based networks

Proportional Fairness (PF) is known to achieve a good trade-off between efficiency and fairness by an opportunistic allocation of resources to users with good radio conditions, without sacrificing fairness towards the other users of the system who have worse radio conditions. On the other hand, Hierarchical Modulation (HM) is a means to increase the spectral efficiency of a given system by superposing an additional information stream over a basic one, by means of embedded constellations. This, in turn, results in a high resource utilization and hence overall system throughput. In this work, we model the system performance, obtained by jointly using PF with HM, for a realistic dynamic setting where users come to the system at random time epochs and leave it after a finite duration, upon the completion of their data transfers. We show that, in the presence of HM, a simple cyclic service, such as round robin, yields a better performance than PF, along with less complex implementation.