Crest factor reduction through scaling and recovering by frame in OFDM communication systems

A new scheme for reducing crest factor in orthogonal frequency division multiplexing (OFDM) communication systems has been proposed. The reduction is achieved by simply scaling all symbols in a frame that exceeds a desired level on the transmitter side. The scaled symbols are recovered by scaling back on the receiver side. All of those operations can be achieved by adding simple functions such as level detection and summation of symbol amplitudes in baseband. The major advantage is that there is no extra information to be sent to the receiver for those operations due to a fixed scaling factor already shared between the transmitter and receiver. Also, the scheme does not degrade adjacent channel power ratio (ACPR) and error vector magnitude (EVM) at all due to the frame-based scaling and recovering so it does not require filtering after crest factor reduction (CFR) as in clipping. One of the limitations is that this scheme achieves only a CFR of about 2.5dB. For validation of the scheme, the processes in baseband and in RF have been conducted with Simulink and measurement with a power amplifier respectively.