What is PAPR?
PAPR (Peak to Average Power Ratio) is the ratio between the peak instantaneous power and the average power of a signal, typically expressed in dB. High PAPR is a fundamental challenge in OFDM-based systems like 5G NR, where the summation of many subcarrier signals can produce occasional very high peaks. These peaks force power amplifiers to operate with significant back-off from their maximum output power, reducing efficiency and increasing cost — a critical consideration for both base station (energy consumption) and UE (battery life) design.
How Does PAPR Work?
In an OFDM signal with N subcarriers, when all subcarriers happen to align in phase, the instantaneous peak power can reach N times the average subcarrier power. For a 5G NR 100 MHz carrier with hundreds of subcarriers, theoretical PAPR can exceed 12 dB. In practice, the probability of maximum peaks is low, so PAPR is typically characterised using the CCDF (Complementary Cumulative Distribution Function) at a specific probability level (e.g., 99.9%). DFT-s-OFDM (used in 5G NR uplink) has lower PAPR than CP-OFDM because it is essentially a single-carrier waveform processed through an OFDM structure. PAPR reduction techniques include clipping, tone reservation, selected mapping (SLM), and active constellation extension.
Use Cases
5G NR power amplifier design and efficiency optimization, DFT-s-OFDM selection for UE uplink (to save battery), base station energy consumption reduction, RF front-end module specification, and waveform design trade-offs in 5G and beyond.
3GPP / Standards Reference
3GPP TS 38.211 (NR physical channels — CP-OFDM and DFT-s-OFDM), 3GPP TR 38.802 (NR waveform study)
Related Terms
EVM | AM distortion | DFT-s-OFDM | CP-OFDM | OFDM
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This glossary entry is part of the 5GWorldPro Complete 5G Glossary. To go deeper into 5G architecture and technology, explore our 5G Training courses.
