Crest Factor Reduction for OFDM-Based Wireless Systems
Orthogonal Frequency Division Multiplexing (OFDM) is regarded widely as the key underlying air interface technology for wireless systems such as WiMAX, 3GPP Long-Term Evolution (LTE), and 3GPP2 ultra-mobile broadband (UMB). Due to the inherent nature of these technologies, OFDM signals have high peak-to-average power ratio (PAR) that adversely affects the efficiency of Power Amplifiers (PAs) used in wireless base stations. Crest factor reduction (CFR) schemes help reduce PAR and have been implemented widely for Code Division Multiple Access (CDMA) systems. However, CFR schemes developed primarily for CDMA signals exhibit poor performance when used in conjunction with OFDM signals, given the stringent Error Vector Magnitude (EVM) requirements specified in a standard such as WiMAX.