OFDM transmitter power amplifier and PAR reduction performance: measurement and simulation

Abstract

Orthogonal frequency division multiplexing (OFDM) is known to exhibit high peak-to-average power ratio (PAR), which may limit the average transmitted power output from a nonlinear power amplifier (PA). We evaluate spectral regrowth and bit-error-rate (BER) performance characteristics when applying OFDM PAR reduction techniques, while integrated to a fixed output level "class A" transmit amplifier. Any potential degradation resulting from the transmitter baseband-to-IF conversion and PA, and the receiver IF-to-baseband conversion, is represented. Through proper modeling of the transmitter PA characteristics, and the transmitter-receiver conversion processes, the transmitted spectrum can be predicted using simulation with remarkable agreement to actual measurements. The complete software defined radio transceiver model demonstrates the expected BER degradations at various PA input backoff operating points. A promising solution to increase the average transmitted power using PAR reduction based on Tellado's method (Tellado, J. and Cioffi, J.M., ANSI Document T1E1.4, Technical Subcommittee no.97-367, 98-083; ITU, Q4/15, no.D-150; Proc. IEEE Int. Symp. on Inf. Theory, p.191, 1998) is presented. A 2.1 dB improvement in input back off (IBO) of the PA is demonstrated.