Inter and intrasystem nonlinearity compensation for radio on fiber considering wideband CDMA air-interface

This paper addresses both the intersystem and intrasystem intermodulation distortions (IMD) for radio on fiber considering the wideband CDMA (WCDMA) air interface. For radio on fiber configuration, base stations (BS) receive RF signals from mobiles and transmit them to the radio network controller (RNC) on an optical fiber channel. Since a WCDMA BS is exposed to the whole cellular spectrum, it receives a comb of frequencies of other cellular systems operating in the same geographical area. This provokes intersystem IMD. Apart from this, the CDMA BS is also subjected to the intrasystem IMD instituted by its own CDMA mobile users due to the nonlinearity of the power amplifier (PA). Moreover as the system is optical fiber feeder, the laser diode's (LD) nonlinearity also incites the IMD due to a clipping effect. The nonlinearities instituted by PA and LD can be regarded as intrasystem IMD. In this paper all these IMD are addressed through a unified operation of FEC codes and post-nonlinearity recovery block (PNRB).