Three PAPR Reduction Methods: SLM, PTS, and Constellation Transformation

There are three primary methods for addressing Peak-to-Average Power Ratio (PAPR) reduction in communication systems: Selected Mapping (SLM), Partial Transmit Sequence (PTS), and Constellation Transformation. These techniques mitigate the adverse effects of high PAPR, which can cause signal distortion in power amplifiers. SLM (Selected Mapping) generates multiple candidate signals by applying different phase rotation sequences to the original OFDM signal. The implementation typically involves creating phase vectors with random or predetermined phase shifts (e.g., using BPSK rotation factors ±1), applying them element-wise to subcarriers, and selecting the signal version with minimum PAPR using magnitude comparison operations. PTS (Partial Transmit Sequence) partitions the input signal into disjoint sub-blocks (via segmentation algorithms), optimizes each segment's phase through iterative search or optimization algorithms (like gradient descent), and combines them coherently. Code implementation requires careful handling of phase weighting factors and inverse Fourier transforms for each partition. Constellation Transformation employs non-uniform constellation mapping (such as circular constellations or hierarchical modulations) to reduce peak power occurrences. This can be implemented through look-up tables or algorithmic remapping that redistributes constellation points away from high-amplitude regions while maintaining minimal BER degradation. These methods enhance system stability by reducing power amplifier back-off requirements, with implementations often involving parallel processing (for SLM candidate evaluation) and side information transmission for signal reconstruction at the receiver.