Parameter Optimization for OFDM Systems in Doubly-Selective Fading Channels with Line-of-Sight Components

In wireless communications, the channel can often be modelled as a time-selective frequency-selective fading channel with line-of-sight (LOS) component. Although orthogonal frequency division multiplexing (OFDM) systems are developed to cope with the frequency selectivity of the channel, they will suffer from interference caused by the time-varying character of the channel, present in particular in the LOS component, when the number of carriers increases. A proper selection of the system parameters, such as the number of carriers and the length of the cyclic prefix, can alleviate the effect of the doubly-selective channel on the system performance. In this paper, we investigate analytically the effect of the aforementioned system parameters on the performance, and determine the optimum values of the system parameters. Further, we study the effect of deviations from the optimum parameters on the system performance