To enhance bit rate in orthogonal frequency division multiplexing by carrier interferometry spreading code

Abstract

In orthogonal frequency division multiplexing (OFDM) based wireless communication systems; extra guard period is inserted to eliminate ISI (inter symbol interference) and ICI (inter carrier interference) effect. The guard period decreases the symbol rate. The authors describe here a model that eliminates the effects of ICI and ISI without inserting extra guard period. The sub-carrier frequencies and carrier interferometry (CI) code distribute alternatively between consecutive OFDM symbols to eliminate the ISI effect. The CI code is used to each sub-carrier in such a way that the subcarrier frequency, orthogonal to each other, when Doppler frequency shift occurs due to relative movement of the transmitter and receiver. A pilot symbol is used in between the two symbols for linear operation of all the electronic devices. A properly designed matched filter at the transmitter and receiver can reduce the effect of ICI. Here, we consider the effect of ICI for carrier frequency synchronizing error, Doppler shift and phase error with a time invariant channel as well.