  This paper investigates the joint number of subcarriers and power
optimization in Multi user Orthogonal Frequency Division Multiplexing based
Differential Chaotic Shift Keying systems with noise reduction. We first find a
closed-form expression for the optimal number of references in MU OFDM DCSK
systems, while existing works only consider the numerical simulations.
Moreover, this paper is the first to consider jointly subcarrier and power
allocation in the MU OFDM DCSK system by defining a fractional problem. The BER
expression of the MU OFDM DCSK system as an objective function is nonconvex and
complex, which makes the analytical solution so difficult. We make it tractable
by converting the fractional problem into a subtractive form, which leads to a
near optimal solution. Simulation results show that our proposed approach
provides better BER performance than the existing plans.
