Reduction of ICI effect in MIMO - OFDM system using self -cancellation with convolution coding and space frequency block code

Abstract

New generation wireless communication systems require high data rate transmission in order to fulfill the requirements for on demand multimedia communication such as- audio, video, image and data. Orthogonal frequency division multiplexing (OFDM) is a multicarrier modulation technique for high data rate transmission of signals over wireless channel. OFDM converts a frequency selective fading channel into a collection of parallel flat fading sub channels but sensitive to frequency offset and phase noise. The carrier frequency offset and phase noise cause loss of orthogonality among subcarriers resulting to inter carrier interference (ICI). Antenna diversity and channel coding in OFDM system reduces the effect of ICI and improves the performance of the conventional system significantly. In this thesis work, analytical models have been developed to suppress ICI with the concept of selfcancellation data conjugate (SCDC) along with convolution coding and space frequency block code (SFBC) for 2x2 multiple input and multiple output (MIMO) OFDM system. Detailed mathematical derivation is carried out for common phase error, ICI, carrier to interference ratio (CIR) and bit error rate (BER) for both SCDC with convolution coding and SFBC. The performance of the proposed systems is evaluated through numerical simulation by varying different system parameters. Results show that while SFBC is used in the proposed system, CIR is increased about 4 dB and 24 dB in SCDC MIMO and conventional OFDM system respectively. The BER performances of SCDC with convolution coding and SFBC have improved about 3 dB and 1.2 dB respectively (at BER of 10-8) in 2x2 MIMO-OFDM system than that of 2x1 multiple input single output OFDM system. Thus, it is observed both coding schemes suppress the ICI effect considerably but SCDC with convolution coding is more effective than SFBC method in 2x2 MIMO-OFDM system.