Two-user opportunistic scheduling using hierarchical modulations in wireless networks with heterogenous average link gains

Our contribution, in this paper, is two-fold. First, we analyze performance of a hierarchical modulation-assisted two-best user opportunistic scheduling (TBS) scheme, which was proposed by the authors in [1], in a fading environment where different users have different average link gains. Specifically, we present expression for the spectral efficiency (SE) of the users and using this expression, we compare degrees of fairness (DOF) of the TBS with that of classical single user opportunistic scheduling schemes. Second contribution is that we propose a new hybrid two-user opportunistic scheduling (HTS) scheme based on the TBS scheme. This HTS selects the first user based on the largest absolute carrier-to-noise (CNR) value among all the users while the second user is selected according to the ratios of the absolute CNRs to the corresponding average CNRs of the remaining users. Numerical results are presented for a fading environment where different users experience independent but non-identical (i.n.d) channel fading. These selected numerical results show that the proposed HTS scheme can considerably increase the system's fairness without any degradation of the link SE compared to the classical single best user scheduling. These results also show that the proposed HTS has a lower fairness in comparison to the proportional fair scheduling (PFS) which suffers from a considerable degradation in link SE.