Channel Analysis in OFDM Systems

Satveer Singh, Md. Umar, Shalini

Orthogonal frequency division multiplexing (OFDM) Technique has received a lot of interest in mobile communication research. For wideband mobile communication system, the radio channel is usually frequency selective and time variant. In OFDM system, the channel transfer function of radio channel appears in both frequency and time domains. Therefore, a estimation of channel is necessary for demodulation of OFDM signal. Channel estimation methods for OFDM system based on pilot aided. In this thesis we investigate and compare different pilot based channel estimation schemes for OFDM systems. The channel estimation can be performed by either inserting pilot tones into all subcarriers of OFDM symbols with a specific period or inserting pilot tones into each OFDM symbol. In this present study, major type of pilot arrangement such as 1. Block type 2. Comb type. Both type of pilot arrangement have been focused employing least square error (LSE) and Minimum mean square error (MMSE) channel estimators. Block type pilot subcarrier is suitable for slow fading radio channels. Comb type pilot subcarrier is suitable for fast fading radio channels. Also com type pilot arrangement is sensitive to frequency selective when compare to block type pilot arrangement. Channel estimation algorithm based on comb type pilot is dividing into pilot signal estimation and channel interpolation. Symbol error rate performance of OFDM systems for both type pilot subcarriers are presented in this thesis.