Estimation and Compensation for Effects of Carrier Frequency Offsets in Orthogonal Frequency Division Multiplexing Based Cooperative Networks
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Abstract
Estimation and Compensation of Carrier Frequency Offset (CFO) is regarded as major operation in the OFDM based Cooperative network. However, the presence of CFO in OFDM based cooperative networks distorts the transmitted signal from the source, this actually result to poor copy of transmitted signal at destination. Maximal Likelihood (ML) which was one of technique used to combat the effects of CFO in the system suffers from higher error as well as low bandwidth efficiency, as there was redundancy of bits for each carrier and observation of computational complex in its operation. Hence, this paper, an Extended Kalman Filter (EKF) was developed to overcome the effect of CFO in order to minimize the error in the OFDM based cooperative network The transmitting signal at the source using the Amplified and Forward protocol at different number of subcarriers and QAMs over the Rayleigh fading channel was received using Enhanced Signal to Noise Ratio Combiner (ESNRC). In the first phase, the transmitted signal was received by the relay, while the second phase of the transmission was made to amplify the transmitted signal at the relay and re-transmitted to the ESNRC where two signals from relay and source were combined for further signal transmission processes. The combined signal was made to pass through estimator and compensator block to reduce the CFO effects in order to minimize the systemic error in the OFDM based cooperative network. The performance of EKF-OFDM technique was assessed using BER and SNR, comparing it to the existing ML-OFDM technique. The simulation results showed that the developed EKF technique achieved better performance than the existing ML-OFDM as well as C-OFDM due to CFO estimation and compensation accuracy by minimizing the error and improvement in bandwidth efficiency through the EKF implementation. The developed technique can be adopted to improve the performance of the OFDM based cooperative network.
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