INGLE CARRIER COMMUNICATION SYSTEM WITH FREQUENCY DOMAIN EQUALIZATION

Abstract

Orthogonal Frequency Division Multiplexing (OFDM) has gained enormous popularity in the recent years due to its inherent ability to counter multipath effects and support high data rates. Its implementation has been made simpler through the efficient calculation of Discrete Fourier Transform (DFT) via the Fast Fourier Transform (FFT) algorithm. However, timing and frequency synchronization issues in OFDM affect its performance severely. Carrier Frequency Offset (CFO) in particular presents a huge problem as a minor offset disturbs the orthogonality of the carriers. In addition, it suffers from high Peak to Average Power ratio (PAPR) at the transmitter and requires the transmitter to operate with a large linear range. To alleviate these problems, a Single Carrier with Frequency Domain Equalization (SC-FDE) is considered which gives performance comparable to OFDM. CFO does not pose that big a problem in SC-FDE. Various frequency domain equalizers have been implemented which include Linear Equalizer, Decision Feedback Equalizer (DFE) and Iterative Block DFE. Inorder to avoid the error propagation phenomenon of the DFEs and to increase the robustness of the Equalizer, we propose the use of a training sequence to optimize the feedforward and feedback filter coefficients. The new technique Data Aided Decision Feedback Equalizer (DAB-DFE), assumes that the transmission takes place within the duration of coherence time and hence, the channel remains constant for the subsequent blocks in the frame. A number of different channels are considered for performance evaluation. The results confirm that DAB-DFE outperforms the contemporary equalizers.