Fast Fading Implementation Optimization in an OFDMA System Simulator

In this paper, we investigate methods for improving an OFDMA system simulator in terms of trade-off between complexity and radio channel implementation accuracy. Fast fading and SINR calculations are the most resource consuming tasks of a system simulator. In order to decrease their complexity, it is proposed to reduce the number of calculated channel transfer function (CTF) realizations according to the time and frequency correlation properties of the simulated radio channel. Besides, we highlight that the upsampling of the channel impulse response (CIR), which is needed for the fast Fourier transform (FFT) application, may introduce major errors in the channel frequency statistics if it is done by simple brute force grid alignment (BFGA) method. To achieve better results we introduce a low complex upsampling method which reduces the simulation inaccuracies significantly. The possibility to trade complexity for precision is shown. It is possible for instance to divide the fast fading and SINR calculation complexity by 50 while keeping a reasonable simulation accuracy.