In this paper, we consider the source-channel rate allocation for different transmission schemes. We propose a new trellis structure and a new algorithm that are able to deal with both variable length packet and fixed length packet problems. The trellis description allows to handle any kind of transmission schemes and can therefore be applied to Bit Interleaved Coded Modulations (BICM), parallel channels or Hybrid-Automatic Repeat reQuest (HARQ).

The problem of frame synchronization of non-binary Low-Density Parity-Check (LDPC) codes is considered in this paper. We propose two techniques of blind frame synchronization that are based on syndrome calculation over the Galois Field GF(q). While the first technique computes hard values of the syndrome, the second one deals with probabilities. Furthermore, we present in this paper a theoretical analysis on the proposed synchronization criteria. This analysis is validated by comparison to simulated results. Although non-binary LDPC codes have short lengths and their decoding is very effective even at low Signal-to-Noise Ratio (SNR), simulation results have shown that the proposed Non-Binary Soft Syndrome (NBSS) based synchronization algorithm is well adapted to such codes. The Frame Error Rate (FER) curves obtained after synchronization and decoding are very close to the perfect synchronization case.

We present in this paper a blind frame synchronization method based on the adaptation of the parity check matrix of the code. The blind synchronizer is initially based on the calculation of the log-likelihood ratios (LLR) of the syndrome elements, obtained using the parity check matrix of the code. Before applying our synchronization procedure, we propose in this paper to rearrange the parity check matrix of the code according to the reliability of the received symbols as previously introduced for decoding linear block codes with high density parity check matrix. Simulation results show that the frame error rate (FER) curves obtained after applying the proposed synchronization method to product codes are very close to the ones with perfect synchronization. In addition to its powerful synchronization properties, the main advantage of the proposed synchronization algorithm is its capability of being introduced as a part of the decoder so that no additional material is required for the synchronization step.

We present in this letter a blind frame synchronization method based on a maximum a posteriori probability (MAP) approach. Applied to coded communication systems, this method is based on the calculation of the log-likelihood ratios (LLR) of the syndrome obtained according to the parity check matrix of the code. After presenting the proposed method, we compare it to an existing blind synchronization method previously introduced. Simulation results show that the proposed method outperforms the existing one and presents good performance when applied to codes having a sparse parity check matrix such as low density parity check (LDPC) codes and convolutional codes.

We have recently proposed in a blind frame synchronization method based on a maximum a posteriori (MAP) approach. In this letter, we study the properties of this method and show that this synchronization technique is well suitable for codes having a sparse parity check matrix, such as low-density parity-check (LDPC) codes. We also find the probability distributions involved in our synchronization criterion and expand the analytical expression of the probability of false synchronization. Through computer simulations we validate our theoretical results and show that this synchronization technique has excellent performance when applied to LDPC codes. We also show that this method outperforms another approach of blind frame synchronization that computes hard values of the syndrome instead of its log-likelihood ratios (LLR).