Joint ICI cancellation, channel estimation and error correction in iterative fashion

Abstract

The rapid advancement in the field of wireless communications that has been expedited by the commercial demand for better services has led to the application of wireless systems in many fields of life including education, military, medical and many real time services. A number of these services demand a high data rate for the applications to run. OFDM is a promising technique that can provide this high data rate by efficiently utilizing the available bandwidth. The problem with this technique is the high Inter-Carrier Interference that occurs due to the disturbance of orthogonality between the subcarriers of an OFDM symbol during the course of transmission. This requires a better channel estimation strategy. Alongwith this, despite the fact that most of the emerging wireless standards such as 802.11n (Wi-Fi) and 802.16e (WiMax) use OFDM technique for increased spectral efficiency and improvement of performance, very little attention has been paid to the use of efficient error correcting Turbo codes ithese systems. The BER of the published work is still not better than 10-3 at affordable SNR for lower modulation schemes. In this research we have applied Frequency-domain equalization technique for suppressing ICI in the OFDM system and have integrated Turbo Codes in the resulting system for error correction. We have worked on the design of an efficient encoder and decoder. The decoder uses an iterative mechanism for decoding the received bits that is based on Maximum a posteriori algorithm. The error reduction achieved by the iterative mechanism of the Turbo Decoder improves the overall coding gain of the system. Results have been achieved for a number of lower order modulation schemes through MATLAB simulation with and without Turbo Codes implementation and with the application of Frequency-domain equalization strategy