Due to its strengths as spectral efficient digital modulation technique Orthogonal Frequency Division Multiplexing (OFDM) is receiving serious attention for very high data rate wireless applications. However the same properties of OFDM that make it so efficient in bandwidth use – orthogonal sub-carriers – cause it to be sensitive to carrier frequency offset and Doppler shifts. This results in inter-carrier interference (ICI) that degrades the bit error rate of OFDM. Also due to the simultaneous use of multiple carriers for data transmission a higher peak to average power ratio (PAPR) can be observed compared to wide-band single carrier transmission techniques. PAPR causes problems with the linear power amplifiers. In the literature there are multiple methods that try to solve those issues. In this work we study several methods that try to improve the drawbacks of traditional OFDM and show that WHT (Walsh Hadamard Transform) combined with OFDM symbol data symmetry and space-time diversity could help improve both the BER and PAPR.
|Commitee:||Mozumdar, Mohammad, Tsang, Chit-Sang|
|School:||California State University, Long Beach|
|School Location:||United States -- California|
|Source:||MAI 54/02M(E), Masters Abstracts International|
|Keywords:||Orthogonal frequency division multiplexing, Space-time, Walsh-hadamard|
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