Reduction of intermodulation products of superior order generated by Nonlinear systems over OFDM signals using a pre-distortion technique

The main problems of multiple carriers that pass through non-linear devices are: a Nonlinear AM / AM conversion, a Nonlinear AM / PM conversion, and inter-modulation. These problems are usually present in satellite transmissions, where high-power amplifiers (HPAs) and nonlinear transponders are used, as well as in terrestrial broadcasting systems where, in order to enlarge the service area (geographical area in which the service is offered) High-power amplifiers operating in their Nonlinear region are used. The multi-carrier transmission called OFDM, which is widely used in wireless networks as WiMAX and LTE, falls in this context. In order to alleviate the effects of Nonlinear channels on OFDM signals, the present study suggests the use of a pre-distortion system, which is mathematically described through a complex power series. The Strategy is focused in determine the parameters of the pre-distortion system, which is based on the reduction of the inter-modulation power sum associated to inter-modulation products of any specified order. Analysis of configurations based on this strategy is presented with numerical results involving situations of specific interest.