Iterative pre-distortion of the non-linear satellite channel

Digital Video Broadcasting - Satellite - Second Generation (DVB-S2) is the current European standard for satellite broadcast and broadband communications. It relies on high order modulations up to 32-amplitude/phase-shift-keying (APSK) in order to increase the system spectral efficiency. Unfortunately, as the modulation order increases, the receiver becomes more sensitive to physical layer impairments, and notably to the distortions induced by the power amplifier and the channelizing filters aboard the satellite. Pre-distortion of the non-linear satellite channel has been studied for many years. However, the performance of existing pre-distortion algorithms generally becomes poor when high-order modulations are used on a non-linear channel with a long memory. In this paper, we investigate a new iterative method that pre-distorts blocks of transmitted symbols so as to minimize the Euclidian distance between the transmitted and received symbols. We also propose approximations to relax the pre-distorter complexity while keeping its performance acceptable

A comparison of soft and hard decision-directed feedforward phase estimators

Publication in the conference proceedings of EUSIPCO, Florence, Italy, 200

On linear MMSE based turbo-equalization of nonlinear Volterra channels

International audienceThis article deals with Minimum Mean Square Error (MMSE) turbo equalization of nonlinear interference using a volterra series decomposition of the underlying nonlinear channel. Although it has been often argued that linear MMSE based equalization is unsuited for cancelling nonlinear interference, we show that this common belief is not true in a strict sense. By a proper derivation of the linear based MMSE soft equalizer, we are able to show that the underlying structure of the equalizer is equivalent to a Soft Interference Canceller (SIC) treating both the linear and nonlinear interference. Based on these results, approximations are provided for lowering the computational complexity. Links to previously proposed “nonlinear” SIC are emphasized showing that the previously proposed structures are nothing but approximations of a linear MMSE receiver applied to nonlinear ISI channels. Simulations show that significant improvements can be achieved by using the proposed exact and approximate MMSE based turbo-equalizers

Asymptotic Analysis and Design of Iterative Receivers for Non Linear ISI Channels

International audienceIn this paper, iterative receiver analysis and design for non linear satellite channels is investigated. To do so, an EXtrinsic Information Transfer (EXIT) chart-based optimization is applied using two major assumptions: the equalizer outputs follow a Gaussian Mixture distribution since we use non-binary modulations and partial interleavers are used between the Low Density Parity Check (LDPC) code and the mapper. Achievable rates, performance and thresholds of the optimized receiver are analysed. The objective in fine is to answer the question: Is it worth optimizing an iterative receiver for non linear satellite channels

On Linear Frequency Domain Turbo-Equalization of Non Linear Volterra Channels

International audienceThis article deals with iterative Frequency Domain Equalization (FDE) for Single Carrier (SC) transmissions over Volterra non linear satellite channels. SC-FDE has gained much importance in recent research for its efficient implementation at the receiver and its interesting low Peak to Average Power Ratio (PAPR) at the transmitter. However, nearly saturated power amplifiers on board satellites generate linear and non linear Inter Symbol Interference (ISI) at the receiver. It is thus interesting to investigate the implementation of SC-FDE for non linear channels. To do so, a frequency domain equivalent satellite channel is derived based on the time domain Volterra series representation of the non linear channel. Then a Minimum Mean Square Error (MMSE)-based iterative frequency domain equalizer is designed. It is shown that the proposed equalizer consists of a Soft Interference Canceller (SIC) which subtracts both the linear and non-linear soft frequency symbols. The equalizer performance is then compared to the equivalent time domain implementation. Results show that a channel-memory independent efficient implementation is achieved at the price of a negligible spectral efficiency loss due to cyclic prefix insertion

Analytical Expressions of Power Spectral Density for General Spectrally Shaped SC-FDMA Systems

In this work, Power Spectral Density (PSD) of different implementations of Single-Carrier Frequency Division Multiple Access (SC-FDMA) are investigated. First, a general model of spectrally shaped SC-FDMA transmission scheme is proposed. This scheme is shown to encompass different implementations of SC-FDMA including the classical Long Term Evolution (LTE) SC-FDMA waveform. Then analytical expressions of PSD are derived for both localised and interleaved FDMA using or not spectral shaping techniques based on the aforementioned general SC-FDMA system model. Finally, analytical results are validated through comparison with simulation estimated PSD

Next generation HTS system using hybrid satellite and terrestrial BB delivery- BATS

This paper presents the results from the EU FP 7 project BATS aimed at integrated BB access across the EU for 2020 and beyond. The BB access is integrated between DSL, LTE and the satellite and features a broadband intelligent user terminal. The satellite component is a cluster of two multibeam HTS satellites providing lower cost per bit than today’s satellites. The system architecture embedding the gateways and user terminals is presented as well as the design for the advanced satellites. The detailed design concepts of the intelligent router are also provided. We present the results of controlled lab tests on an emulated test bed as well as initial results from a field trial in which the intelligent routers were placed in households in Spain and Germany and connected to local; DSL and LTE as well as the Hylas satellite