High performance phase rotated spreading codes for MC-CDMA

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Conference Proceeding

Publication Date



In conventional multi-carrier CDMA (MC-CDMA) systems, binary spreading codes such as Hadamard-Walsh codes are employed to spread user information across all subcarriers to exploit frequency diversity in frequency selective fading channels. We first recap that because of the binary nature of the spreading codes, transmission power is not distributed evenly across all subcarriers. Oftentimes, certain subcarriers have zero transmission power, leading to less diversity to be exploited at receiver. We employ a phase rotated spreading code design and derive the corresponding combining scheme for the phase rotated codes. As a direct result, MC-CDMA system now exploits full diversity available in the channel at all times, leading to significant performance gain. Simulation results over various multi-path fading channels confirm the performance gain of the scheme.



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