SLVA decoding with unequal error protection

The unequal error protection (UEP) has shown promising results for transmitting video over error-prone wireless channels. In this paper, we investigate the cross-layer design of forward error correction (FEC) schemes by using the UEP Raptor codes at the application layer (AL) and UEP rate compatible punctured convolutional (RCPC) codes at physical layer (PHY) for prioritized video packets. The video packets are prioritized based on their contribution to the received video quality. A genetic algorithm (GA)-based optimization algorithm is proposed to find the optimal parameters for both Raptor and RCPC codes, to minimize the video distortion and maximize the peak signal-to-noise-ratio for the given video bit rates and channel constraints (i.e., SNR and available bandwidth). We evaluate the performance of four combinations of the UEP schemes for H.264/AVC encoded video sequences over the AWGN and Rayleigh fading channels and show the superiority of the optimized cross-layer UEP FEC scheme. For Rayleigh fading channel, the proposed cross-layer optimization uses two different time-scales at AL and PHY which allows PHY to adapt faster to the changing channel quality.

The communication of reliable data among wireless users that employ multiclass bitstreams to achieve high coding gains has been a tremendous challenge for researchers. In practice, multimedia standards are implemented in wireless technologies to achieve unequal error protection (UEP). These standards employ data partitioning where different levels of importance are assigned to the multimedia content. In this context, in this paper, we provide a generalized UEP framework to evaluate the theoretical error performance bounds of concatenated Reed–Solomon and rate-compatible punctured convolutional (RCPC) codes employing hierarchical 8PSK modulation over both Gaussian and flat Rayleigh wireless fading channels. The contribution of this work is to promote unequal error protection of the multimedia bitstreams without sacrificing channel bandwidth and increasing the computational complexity of the communication system. All the derived theoretical performance bounds are illustrated with numerical examples, and these are simulated using MATLAB Simulink® R2017. Simulation results revealed that with the lowest constraint length of the RCPC codes, near 5-dB difference is achieved between the first- and last-priority subchannels. The proposed unequal protection scheme can be applied to deep-space data transmission systems, digital video broadcasting and wireless JPEG2000 as well as H.265 data transmission systems.

The MPEG-4 video compression standard incorporates several techniques to create error-resilient coded video. These techniques are effective against a certain level of errors. However, wireless channels often have very high error rates; thus channel coding is needed to reduce the number of errors in the compressed bitstream that is sent to the MPEG-4 video decoder. The structure of an MPEG-4 compressed bitstream lends itself to using unequal error protection to ensure fewer errors in the important portions of the bitstream. This paper discuses how unequal error protection can be used with the MPEG-4 error resilience tools and describes several experiments using both unequal and equal error protection on video sent through a simulated GSM channel. The results of these experiments show that when the bit error rate is high, unequal error protection can improve reconstructed video quality by as much as 1 dB compared with equal error protection.

We design and assess some practical low-density parity-check (LDPC) coded transmission schemes for the Gaussian broadcast channel with confidential messages (BCC). This channel model is different from the classical wiretap channel model as the unauthorized receiver (Eve) must be able to decode some part of the information. Hence, the reliability and security targets are different from those of the wiretap channel. In order to design and assess practical coding schemes, we use the error rate as a metric of the performance achieved by the authorized receiver (Bob) and the unauthorized receiver (Eve). We study the system feasibility, and show that two different levels of protection against noise are required on the public and the secret messages. This can be achieved in two ways: i) by using LDPC codes with unequal error protection (UEP) of the transmitted information bits or ii) by using two classical non-UEP LDPC codes with different rates. We compare these two approaches and show that, for the considered examples, the solution exploiting UEP LDPC codes is more efficient than that using non-UEP LDPC codes.

Under strong line-of-sight (LOS) conditions, in a conventional spatial modulation scheme, the signal domain exhibits better error performance than the spatial domain, thus rendering the accomplishment of unequal error protection (UEP) a difficult task. To this end, multilevel spatial hierarchical modulation (MSHM) is proposed to provide UEP in Rician fading channels when both the high priority (HP) and the low-priority information streams are jointly encoded in the spatial and signal domains. A phase-aided multilevel space-shift keying scheme is employed in the spatial domain to enhance HP performance, whereas in the signal domain, hierarchical modulation is employed. The joint space-signal constellation related to the LOS component of the received signal is appropriately formed to provide higher protection to the HP stream while, at the same time, being capable of providing different levels of protection by adjusting the transmission parameters of the spatial and signal schemes when they are jointly employed. By incorporating the Rician factor to the parameters of the proposed MSHM scheme, the latter is made adaptive to the fading conditions. Simulations have been performed to assess the performance and demonstrate the design options offered by the proposed MSHM scheme.

In this paper we propose a new image transmission scheme for an image which has been compressed using wavelet image compression and coded with a Variable Length Code. The proposed scheme applies Unequal Error Protection (UEP) at three different stages, namely the source coding, channel coding and retransmission stage. UEP at the source coding stage is employed to unequally protect the image subbands against error propagation, which arises due to variable length coding. At the channel coding stage, UEP is applied by the use of Rate Compatible Punctured Convolutional codes to unequally allocate coding redundancy to the image subbands. Finally at the retransmission stage, UEP is applied by assigning different synchronization error tolerances to the image subbands. Gains of over 4 dB in terms of Peak to Peak Signal to Noise Ratio (PSNR) is achieved by employing the integrated UEP scheme as compared to a standard Equal Error Protection Scheme.

In order to improve the bit error rate (BER) of multiple-input multiple-output orthogonal frequency diversity multiplexing (MIMO-OFDM) system in Nakagami-m channels, the model used rate-compatible punctured convolution (RCPC) and space-time block code (STBC) at the transmitter, maximum ratio combining (MRC) at the receiver was put forward. The signal-to-noise ratio (SNR) of the MIMO-OFDM system in Nakagami-m channels was studied, the expression of BER was given and the average BER upper limit after RCPC encode was further presented. Simulation result shows that the BER performance and the diversity gain of MIMO-OFDM with RCPC encoding achieve much improvement than the system with no RCPC. Owing to the free distance becomes shorter with the increase of code rate, the BER performance and the diversity gain of RCPC encoded MIMO-OFDM decreases a little

Recently, the forward error correction (FEC) codes are gaining popularity in video transmission community because of its capability of recovering lost packets in lossy wireless networks. The state-of-the-art scheme for FEC video transmission are the delay-aware fountain codes (DAF), which combine the ratelessness of fountain codes with the property of video coding. However, DAF assumes that all the data in the video has the same importance, thus every packet should have the equal chance to be decoded. In this work, in order to further adapt DAF to real-world video coding, we propose a method to integrate the unequal error protection (UEP) into DAF to provide additional protection for important bits. Different from the existing schemes, the proposed scheme does not impose any restriction on the importance profile, and it does not rely on any specific video coding standard. Most importantly, the proposed scheme is designed within the framework of DAF, so it neither requires any change on the DAF decoder or the protocol, nor any additional coordination between encoder and decoder. Simulation experiments show the proposed system achieves higher decoding ratios and PSNR compared to equal error protection (EEP) under the same network conditions.

Give a limited bandwidth, unequal error protection (UEP) via channel coding with different code rates for different important regions of bitstream may yield much less error contamination than equal error protection (EEP). We propose an optimal code rate allocation scheme that minimizes error contamination after channel and source decoding. We use JPEG2000 for source coding and turbo product code (TPC) for channel coding as an example to demonstrate this technique with ultraspectral sounder data. The statistics of erroneous pixels after TPC and JPEG2000 decoding are used to determine the optimal channel code rates for each wavelet resolution. The proposed UEP scheme significantly reduces error contamination when compared to its EEP counterpart. The optimal code rate allocation needs to be determined only once, given any predefined set of available channel codes, desired code rate, and noise level.

Distributed Speech Recognition (DSR) systems rely on efficient transmission of speech information from distributed clients to a centralized server. Wireless or network communication channels within DSR systems are typically noisy and bursty. Thus, DSR systems must utilize efficient Error Recovery (ER) schemes during transmission of speech information. Some ER strategies, referred to as forward error control (FEC), aim to create redundancy in the source coded bitstream to overcome the effect of channel errors, while others are designed to create spread or delay in the feature stream in order to overcome the effect of bursty channel errors. Furthermore, ER strategies may be designed as a combination of the previously described techniques. This chapter presents an array of error recovery techniques for remote speech recognition applications. This chapter is organized as follows. First, channel characterization and modeling are discussed. Next, media-specific FEC is presented for packet erasure applications, followed by a discussion on media-independent FEC techniques for bit error applications, including general linear block codes, cyclic codes, and convolutional codes. The application of unequal error protection (UEP) strategies utilizing combinations of the aforementioned FEC methods is also presented. Finally, framebased interleaving is discussed as an alternative to overcoming the effect of bursty channel erasures. The chapter concludes with examples of modern standards for channel coding strategies for distributed speech recognition (DSR). 8.1. Distributed Speech Recognition Systems Throughout this chapter various error recovery and detection techniques are discussed. It is therefore necessary to present an overview of a complete experimental DSR system, including feature extraction, a noisy channel model, and an automatic speech recognition engine at the server end (Fig. 8.1). 2 Bengt J. Borgstrom, Alexis Bernard, and Abeer Alwan Feature Extraction Source Coding Channel Coding Channel Decoding Source Decoding Speech Recognition Client Server Noisy Channel input speech

Polar codes are the first provable capacity-achieving channel codes. Despite the splendid performance of long Polar codes, short Polar codes have relatively poor performance compared with other modern channel coding schemes (e.g., Turbo codes and LDPC). In this paper, we explore some practical methods to improve the performance of Polar codes with short to moderate codeword lengths. First, we use Reed Solomon (RS) codes as outer codes. With a specific interleaving strategy, we can concatenate multiple RS codes with one frame of Polar codes. Combining a strategy of allocating unequal RS code rates with the concatenation, different levels of protection are assigned based on the error pattern of successive cancellation list (SCL) decoders. Thus, the finite length performance will certainly be enhanced for this encoding scheme. Meanwhile, the memory size that the original SCL decoding procedure requires is reduced, and the increment of overall decoding complexity is small. Additionally, we propose an intra-frame interleaver to further enhance the performance by dispersing errors. Finally, we designed a list decoding scheme for the proposed multi-RS concatenated Polar codes. Depending on the soft information generated by an SCL decoder, we calculated the reliability of each RS symbol and conducted soft RS decoding. So, the overall performance was enhanced under this joint decoding strategy. Simulation results indicate that the bit error rate (BER) performance of short Polar codes can be well improved.

Spatial variation of intertidal assemblages at Tavolara-Capo Coda Cavallo MPA (NE Sardinia): geographical vs. protection effect

This paper presents a solution to the problem of providing quality-of-service (QoS) guarantees in an ATM network with wireless links. The suggested resolution to this problem is through selectable-rate channel coding. In particular, rate-compatible punctured convolutional (RCPC) codes are employed due to their several attractive features that make them favorable for ATM-based applications. In this adaptive scheme, the RCPC code rate is intelligently varied in response to the channel's nonstationary behavior according to the channel state information (CSI). This yields an equivalent stationary channel with a fixed and predetermined bit-error rate (BER) in which QoS can be guaranteed. In order to demonstrate the performance of RCPC codes in providing and maintaining the QoS, a lognormal fading channel model is assumed. An architecture is proposed for the wireless link. This system assumes that accurate CSI is available at the transmitter as well as at the receiver. Bandwidth utilization of the proposed system under various channel conditions is then evaluated, plotted, and discussed.

In this paper, we focus on network coding design for the wireless sensor networks (WSNs), where multiple source nodes communicate with a common destination node with the help of multiple relay nodes in a two-hop fashion. Specifically, we propose an unequal error protection (UEP) distributed network-channel coding (DNCC) scheme based on Luby-transform (LT) codes. We analyse three properties of the proposed UEP DNCC scheme, i.e. effective weights, turning points, and thresholds of the source nodes' number. Also, we derive the upper and lower bit error rate (BER) bounds for the proposed UEP DNCC scheme over Rayleigh fading channels under maximum-likelihood (ML) decoding. Based on the analysis, it is observed that the proposed UEP DNCC scheme can achieve all protection levels required when the number of source nodes is large enough. Simulation results show that our UEP DNCC scheme can provide desirable UEP to all source nodes.

We propose an iterative design algorithm for jointly optimizing source and channel codes. The joint design combines channel-optimized vector quantization (COVQ) for the source code with rate-compatible punctured convolutional (RCPC) coding for the channel code. Our objective is to minimize the average end-to-end distortion. For a given channel SNR and transmission rate, our joint source and channel code design achieves an optimal allocation of bits between the source and channel coders. This optimal allocation can reduce distortion by up to 6 dB over suboptimal allocations for the source data set considered. We also compare the distortion of our joint iterative design with that of two suboptimal design techniques: COVQ optimized for a given channel bit-error-probability, and RCPC channel coding optimized for a given vector quantizer. We conclude by relaxing the fixed transmission rate constraint and jointly optimizing the transmission rate, source code, and channel code.