A hybrid PAPR reduction scheme for coded OFDM

We consider schemes for reducing the peak-to-average power ratio (PAPR) in coded orthogonal frequency-division multiplexing (OFDM) systems. We develop a new PAPR reduction technique using the label-inserted encoder of a random-like code and the soft amplitude limiter (SAL). Using this hybrid scheme provides 5.5 dB PAPR reduction in an OFDM system with 128 subcarriers, 4-bit selection and 3 dB clipping. Besides the significant PAPR reduction, the scheme also enjoys other advantages such as small overhead, low complexity, no side information transmission, and little performance loss. Among various random-like codes, the irregular repeat accumulate (IRA) code is the best choice for its simple encoder and capacity achieving performance. The scheme can be directly applied to multiple-input multiple-output (MIMO) OFDM systems. The capacity of the clipped MIMO-OFDM systems is analyzed based on a Gaussian approximation of the clipping noise. We consider an iterative receiver with soft MAP MIMO-OFDM detector. For both single antenna and multiple antenna systems, the encoder part is independent in the hybrid scheme, thus no additional constraint is applied to the IRA code optimization. The IRA codes are designed for the ergodic MIMO-OFDM systems with different PAPR reduction settings, more specifically different clipping ratios, based on the extrinsic information transfer (EXIT) charts. Simulation results show that the hybrid scheme with 3 dB clipping can achieve as good PAPR reduction performance as the simple clipping with 0 dB ratio but incurs much less performance loss at the receiver