Ofdm, Turbo Codes and Improved Channel Estimation: a Magical Combination

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 which demand a high data rate. OFDM is a promising technique that can provide this high data rate by efficiently utilizing the bandwidth. Thus a no. of emerging wireless standards such as 802.11n (Wi-Fi) and 802.16e (WiMax) use OFDM for increased spectral efficiency. The problem with OFDM is the high Inter-Carrier Interference due to the disturbance of orthogonality between the subcarriers of a symbol. It requires a better channel estimation strategy. Alongwith this, very little attention has been paid to the use of efficient error correcting Turbo codes in these systems. In the work presented in this book, we have used Frequency-domain Pilot-assisted Block-type equalization technique for suppressing ICI in the OFDM system and have integrated Turbo Codes in the resulting system for error correction. The decoder is based on Maximum a posteriori algorithm which uses an iterative mechanism for decoding the received bits.