This paper deals with optimized channel coding for OFDM transmissions (COFDM) over frequency-selective channels using irregular low-density parity-check (LDPC) codes. Firstly, we introduce a new characterization of the LDPC code irregularity called " irregularity profile. " Then, using this parameterization, we derive a new criterion based on the… (More)
We present an optimized channel coding scheme for OFDM transmitter. Traditional coding methods use regular codes, in the sense that each bit participates in the same way to the channel encoding. Our approach consists in using a priory assumption on the channel available at the transmitter in order to optimize the coding scheme. We have considered the… (More)
The blind separation problem of linear time-dependent mixtures is addressed in this paper. We have developed a new algorithm based on the minimization of the mutual information as well as a penalized term which ensures an a priori normalization of the estimated sources (outputs) and so, avoids the scale indeterminacy. The criterion minimization is done… (More)
— We introduce a wide class of LDPC codes, large enough to include LDPC codes over finite fields, rings or groups as well as some non-linear codes. A belief propagation decoding procedure with the same complexity as for the decoding of LDPC codes over finite fields is also presented. Moreover, an encoding procedure is developed.
There is a great interest to apply BSS methods in mechanical system signal processing for monitoring or diagnosis purpose. Actually, we show that BSS allows to recover the vibratory information issued from a single rotating machine working in a noisy environment by freeing the sensor signal from the contribution of other working machines. In that way, BSS… (More)
— All systems dealing with the Orthogonal Frequency Division Multiplexing (OFDM) modulation are affected by the major, and well known, drawback of high Peak-to-Average Power Ratio (PAPR). The deliberate amplitude clipping has been found as a suitable way to reduce the output signal level of OFDM transmitters. Unfortunately, it causes numerous degradations… (More)
Recommended by Luc Vandendorpe Orthogonal frequency division multiplexing (OFDM) is the modulation technique used in most of the high-rate communication standards. However, OFDM signals exhibit high peak average to power ratio (PAPR) that makes them particularly sensitive to nonlinear distortions caused by high-power amplifiers. Hence, the amplifier needs… (More)
High peak average to power ratio (PAPR) is one of the main drawback of the OFDM systems currently used in high rate communication standards. One way to reduce PAPR consists in clipping the amplitude of the OFDM signals introducing an additional noise that degrades the system performances. This work presents two iterative reconstruction algorithms of the… (More)