Throughput-constrained scheduling in OFDMA wireless networks

Adaptive modulation and coding is an important characteristic of OFDMA based wireless networks. A group of subcarriers and symbols (which we refer to as “allocation unit”) can be assigned to an user equipment (UE) based on its channel conditions. The “allocation units” can have different bandwidths for different UEs depending on the current channel conditions of the UEs. The UEs typically have a minimum throughput requirement. In this article our goal is to design a scheduler that maximizes the number of scheduled UEs while meeting their minimum throughput requirements. First we define an analytical model for scheduling and then propose three algorithms for the optimization problem. We show that, given the sets of “allocation units”, maximizing the number of UEs is equivalent to finding the maximum independent set of a bounded degree graph. We also define the set allocation problem that minimizes the number of intersecting sets subject to certain constraints.