A Linear Programming Solution to the Subcarrier-and-Bit Allocation of Multiclass Multiuser OFDM Systems

Adaptive subcarrier-and-bit allocation in orthogonal frequency division multiplexing (OFDM) systems can significantly improve spectral efficiency and reduce power consumption. The combinatorial optimization on the power, bit and subcarrier allocation in multiclass multiuser OFDM systems normally involved nonlinear objective functions and constraints, resulting in highly complex and computation intensive optimization problems. In this paper, we propose a method to linearize and simplify the optimization problem formulated on subcarrier-and-bit allocation in multiclass multiuser OFDM systems. With a drastically reduced complexity, the converted linear optimization problem can be solved in close to real time and the solutions found are optimal, as no relaxation is made during the linearization. Different approximate relationships between symbol error rate (SER) and bit error rate (BER) are also used to investigate the calculation on the required transmit power.