Peak Power Reduction for Pilot-Aided OFDM Systems with Semi-Blind Detection

Orthogonal Walsh-Hadamard sequences have been adopted for peak-to-average power ratio (PAPR) reduction without sending side information in pilot-aided orthogonal frequency division multiplexing systems. The PAPR reduction performance is determined by the number of orthogonal sequences, which is equal to the sequence length. However, increasing the length of pilot sequences significantly degrades bandwidth efficiency. The current study presents a novel set of pilot sequences obtained by sub-sampling the Zadoff-Chu sequences. The sub-sampled sequences are then equally partitioned into several groups, where sequences in the same group are orthogonal to one another and can therefore be blindly detected at the receiver. The number of pilot sequences can be doubled whenever one extra bit of side information is sent for a given pilot length. Therefore, the proposed scheme has the advantage of enhancing PAPR reduction performance with only marginal cost.