Peak cancellation and digital predistortion of high-order QAM wideband signals for next generation wireless backhaul equipment

This paper evaluates the linearity performance in a wideband wireless backhaul transmitter when applying crest factor reduction (CFR) and digital predistortion (DPD) techniques to enhance the transmitted output power, and thus the power efficiency of the overall system, while fulfilling the communications system quality requirements and regulations. The CFR technique applied is the peak cancellation (PC), while the linearizer is based in an adaptive DPD with memory effects compensation. Order reduction techniques are also applied to mitigate the complexity of the DPD structure. The power amplifier is based in a 15 Watts GaN transistor. The test signal follows a multiband 4 channel 1024-QAM configuration (reaching up to 1 Gbps) with 12 dB of PAPR at RF and 112 MHz bandwidth (28 MHz each channel). A testbed for evaluating the PC and DPD linearization performance of the RF subsystem was deployed and experimental results are presented in this paper.