Predistortion for Wideband Nonlinear Satellite Downlinks

Layton, Kelvin J.; Mehboob, Azam; Akhlaq, Assad; Bagaglini, Flaviano; Cowley, William G.; Lechner, Gottfried

doi:10.1109/lcomm.2017.2710339

Cited by 10 publications

(17 citation statements)

References 9 publications

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“…Three strategies were compared (The system includes the TWTA and OMUX filter): No predistortion. The traditional DPD (the signal loss of the band‐limited feedback signal output through OMUX is ignored) using a complexity‐reduced MP model with K = 9 and M = 6. The proposed DPD (the signal loss of the band‐limited feedback signal output through OMUX is recovered) using a complexity‐reduced MP model with K = 9 and M = 6. The predistortion parameters were extracted using the signal from the first 8000 symbols, branched from different paths in the transmit chain. The iterative algorithm performed up to 10 iterations to minimize the difference between the desired signal and the predicted signal after the nonlinearity.…”

Section: Simulation Results and Analysismentioning

confidence: 99%

Exploiting low complex digital predistortion to improve wideband nonlinear satellite downlinks

Liu

et al. 2018

Satell Commun Network

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With the increasing demand for higher data rate, increasing throughput requires wider bandwidth. Due to the nonlinear effect of power amplifier, severe nonlinear distortion effects will appear onboard satellite. Digital predistortion (DPD) scheme is usually employed to compensate for the distortions and memory effects introduced by traveling wave tube amplifier (TWTA) and output multiplexing filter (OMUX). In conventional predistorter, the signal loss of band-limited feedback signal output through OMUX is usually ignored. Actually, it will affect the linear effect of TWTA. In order to solve the problem as to improve wideband nonlinear satellite downlink, this paper introduces a novel spectral extrapolation method based on deep neural network to recover the band-limited feedback signal. On this basis, an advanced orthogonal matching pursuit algorithm is adopted in the nonlinear TWTA model construction to further reduce the DPD complexity. The proposed setup effectively compensates the distortions and is well suited for systems that generate data bits on satellites. KEYWORDS digital predistortion, nonlinear, output channel filter, satellite downlinks 1 | INTRODUCTION Increasing data rates over satellite channels have motivated the quest for efficient transmission of spectrum, while sharing a single high power amplifier with multiple carriers. Compensation for nonlinear distortion with memory is a key technology for the highly efficient operation of communication systems. The main contributor to nonlinearity in satellite is the traveling wave tube amplifier (TWTA) when it is driven close to saturation. In addition, with the increase in demand for transmitting broadband signals, the memory effects of output signals through TWTA and output multiplexing filter (OMUX) become more prominent. The nonlinear distortion caused by TWTA manifests itself in two major effects.One is that spectral spreading or regrowth causes spillage into adjacent frequency bands and may violate the stringent spectrum limits set by the regulatory commissions. Another effect is in-band distortion causes constellation warping and clustering. Unless appropriate methods are taken, both two effects are detrimental and can severely degrade system performance .1,2 Digital predistortion is a transmitter-based method of effectively mitigating nonlinear distortion. There are two categories of approaches, data predistortion and signal predistortion. Data predistortion is more suitable in "bent pipe" satellites as the uplink can be corrected at the gateway. A data predistortion method using Volterra inverse is proposed in Piazza et al 3 for multicarrier satellite operation. For multicarrier data predistortion, Beidas et al 4 utilizes stochastic approximation to introduce another data predistortion method with enhanced performance. However, in adaptive technology, most of the available signal predistortion methods are still based on inversions that minimize the equalization mean squared error (MSE), using various models such as Volterra or Wiener. 5 Signal p...

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Section: Simulation Results and Analysismentioning

confidence: 99%

Exploiting low complex digital predistortion to improve wideband nonlinear satellite downlinks

Liu

et al. 2018

Satell Commun Network

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“…Thus, it is easy to find R(r , θ ) = R(r * , θ * ), which indicates that (r , θ ) is also an optimal solution to (11). Accordingly, one can conclude that there must exist one optimal solution that satisfies both (12) and (13) . According to Proposition 1, the problem in (11) can be recast without loss of optimality as max r,θ…”

Section: Beamforming Optimizationmentioning

confidence: 93%

“…PA nonlinearity often exists in practical systems [10], [11], where digital pre-distortion (DPD) modules are widely used to mitigate it [12], [13]. However, both energy consumption and hardware cost are limited for practical HSTNs.…”

Section: Introductionmentioning

confidence: 99%

Optimal Beamforming for Hybrid Satellite Terrestrial Networks With Nonlinear PA and Imperfect CSIT

Liu

Feng

Chen

et al. 2020

IEEE Wireless Commun. Lett.

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In hybrid satellite-terrestrial networks (HSTNs), spectrum sharing is crucial to alleviate the "spectrum scarcity" problem. Therein, the transmit beams should be carefully designed to mitigate the inter-satellite-terrestrial interference. Different from previous studies, this work considers the impact of both nonlinear power amplifier (PA) and large-scale channel state information at the transmitter (CSIT) on beamforming. These phenomena are usually inevitable in a practical HSTN. Based on the Saleh model of PA nonlinearity and the large-scale multibeam satellite channel parameters, we formulate a beamforming optimization problem to maximize the achievable rate of the satellite system while ensuring that the inter-satellite-terrestrial interference is below a given threshold. The optimal amplitude and phase of desired beams are derived in a decoupled manner. Simulation results demonstrate the superiority of the proposed beamforming scheme.Index Terms-Beamforming, hybrid satellite-terrestrial network, large-scale channel state information, nonlinear power amplifier, spectrum sharing.

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“…Considering the power limitation of the satellite, the high power amplifier (HPA) in the transponder of satellite channels often operates near the saturation point to improve the power efficiency [4,5]. However, due to the non-linear transfer characteristics of the HPA, non-linear distortion is introduced in the form of constellation warping and clustering at the receiver when high-order modulated signals with large envelopes are used for transmission [6][7][8].…”

Section: Introductionmentioning

confidence: 99%

Design of Nonequiprobable High-Order Constellations over Non-Linear Satellite Channels

Chen

Han

et al. 2020

Electronics

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High-order modulations are essential to improve the bandwidth efficiency of communication systems. However, such modulated signals with large envelopes are typically sensitive to the non-linear distortion caused by high power amplifiers (HPAs) in the transponder of satellite channels. In this paper, a new nonequiprobable constellation is designed to combat the non-linear effects of HPAs. We use non-uniformly distributed symbols to construct the appropriate high-order constellation for non-linear satellite channels. The nonequiprobable symbols are generated using the non-linear mapping method, which specifically consists of expansion mapping, symbol decomposition, permutation, and combination. Moreover, the demapping method adapting to the designed nonequiprobable constellation is also discussed. The simulation results show that the proposed scheme has considerable performance improvements compared with the traditional equiprobable constellations over the non-linear satellite channel.

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Predistortion for Wideband Nonlinear Satellite Downlinks

Cited by 10 publications

References 9 publications

Exploiting low complex digital predistortion to improve wideband nonlinear satellite downlinks

Exploiting low complex digital predistortion to improve wideband nonlinear satellite downlinks

Optimal Beamforming for Hybrid Satellite Terrestrial Networks With Nonlinear PA and Imperfect CSIT

Design of Nonequiprobable High-Order Constellations over Non-Linear Satellite Channels

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