Adaptive Subcarrier-and-Bit Allocation in Multiclass Multiuser OFDM System

Abstract

Subcarrier-and-bit allocation (SBA) has been exten- sively investigated in the literature to improve spectral efficiency of multiuser OFDM systems. However, in previous studies, only suboptimal solutions were given and only single-class cases were considered. In this paper, adaptive SBA for multiclass multiuser OFDM system is considered. The optimal solution to this problem for a given revenue function is derived, i.e., the instantaneous total system revenue is maximized with the quality-of-service (QoS) of each class guaranteed. The framework presented in this paper, which gives the optimal solution, can be used as a benchmark for future developed heuristic algorithm. because the optimal solution has yet been given so far, and it remains a challenging topic in this area. Moreover, variety of service classes was not taken into consideration in the previous literature, which restricted the application of these algorithms to only single-class case. In this paper, we deal with transmit power optimization of adaptive SBA for multiuser OFDM system supporting multiclass services. Each class has its own QoS requirements such as target data rate and bit error rate (BER). The purpose is to conduct a unified analysis of this constrained optimization problem and then derive its exact optimal solution. The results obtained from this theoretical framework will be useful for comparing the accuracy of any developed suboptimal or heuristic algorithm.