Low complexity predistortion and equalization in nonlinear multicarrier satellite communications

Efrain Zenteno, Roberto Piazza, Bhavani Shankar Mysore Rama Rao, Daniel Rönnow, Björn Ottersten
2015 EURASIP Journal on Advances in Signal Processing  
Aiming to reduce the power/mass requirements in satellite transponders and to reduce mission costs, joint amplification of multiple carriers using a single high-power amplifier (HPA) is being considered. In this scenario, a careful investigation of the resulting power efficiency is essential as amplification is nonlinear, and multicarrier signals exhibit enlarged peak-to-average power ratio. Thus, operating the amplifier close to saturation vastly increases signal distortion resulting in a
more » ... e degradation of performance, especially for higher order modulations. This paper proposes a reduced-complexity digital predistortion (DPD) scheme at the transmitter and a corresponding equalizer (EQ) at the receiver to mitigate these nonlinear effects. Scenarios include both the forward as well as the return links. In particular, the paper exploits the MIMO Volterra representation and builds on a basis pursuit approach using a LASSO (least absolute shrinkage and selection operator) algorithm to achieve an efficient basis representation, avoiding large computational complexity, to describe the selection of predistorter/equalizer model. The work further compares and contrasts the two mitigation techniques taking various system aspects into consideration. The gains in performance and amplification efficiency demonstrated by the use of DPD/ EQ motivate their inclusion in next-generation satellite systems. transmit the data stream in a form suitable for reception by a satellite. Transparent payloads, where the uplink data is mainly frequency shifted, amplified, and forwarded to users, are by far the most common telecom satellite architectures due to their competitive cost and technological flexibility. Clearly, in such payloads, the signal processing carried out on the ground can be updated based on technological advances in the course of the lifetime of the satellite. Each satellite transponder receives the data signal from one or more gateways and processes it before redirecting it to the ground receivers. In the widespread direct-to-home (DTH) services, the end receivers are fixed integrated receiver decoders [1] for TV applications. To ensure that the amplification is power efficient, the high-power amplifiers (HPAs) are operated close to the saturation point. However, these HPAs suffer from nonlinear effects when driven close to saturation leading to signal distortion [2] . High order signaling/modulation
doi:10.1186/s13634-015-0215-0 fatcat:gaqkpg6e3vamzfv7wfghivaxqq