Cross-Layer Forward Error Correction Scheme Using Raptor and RCPC Codes for Prioritized Video Transmission Over Wireless Channels

3G mobile multimedia communication systems based on W-CDMA support a flexible and adaptive transmission capability to provide packet data service as well as voice service. Mobile multimedia communication requires a coding scheme that can accommodate varying code rate requirements. RCPC (rate compatible punctured convolutional) codes are one practical solution to adaptive coding. RCPC codes use a single rate-1/n convolutional encoder/decoder pair and the transmitter and receiver only need to share a puncturing table. RCPT (rate compatible punctured turbo) codes can be used in a similar way to RCPC codes. This paper considers the application of concatenated RS-RCPT codes and RCPT-HARQ (hybrid ARQ) schemes to W-CDMA.

This paper investigates how Scalable Video Coding (SVC) can benefit from different Forward Error Correction (FEC) and transmission schemes in mobile broadcast systems. Simulation are performed in DVB-H (Digital Video Broadcasting - Handheld) systems. In DVB-H, a differentiation in robustness for the different SVC layers can be achieved at the link layer using intra-burst MPE-FEC (multi-Protocol Encapsulation FEC). The paper evaluates the gain that can be achieved with the MPE-FEC using equal (EEP) and unequal error protection (UEP), and the performance improvements of an SVC layer-aware FEC (LA-FEC) approach that can be implemented in DVB-H either at the link layer with MPE-iFEC (inter-burst MPE-FEC) or at the application layer with AL-FEC. LA-FEC improves the SVC base layer robustness generating parity information across existing dependencies within the SVC video coding structure. Laboratory measurement results using a TU6 channel model show that the performance of an SVC service in DVB-H can be significantly increased by a proper link layer FEC scheme. It is shown that using SVC in combination with LA-FEC and a proper transmission scheduling does not only give a better performance in terms of PSNR and amount of video outages compared to a single layer service at the same service bit rate, but also gives an additional lower quality layer which can be used for applications like conditional access.

This thesis summarizes research on the design and implementation of the unequal error protection (UEP) mechanism for the RaptorQ forward error correction (FEC) scheme. As part of this research, existing UEP mechanisms for various fountain codes were evaluated. Two new UEP methods were proposed for the RaptorQ coding scheme, and these methods were designed with the assumption that all of the symbols in a source block have the same priority. The first method, known as priority based overhead number (PBON), was based on the priority encoding transmission model, wherein the error-correction capability was altered by making the number of overhead symbols proportional to the priority of the information symbols. This method was extended to the RaptorQ codes with some changes and evaluated for failure probability and performance. The second method, known as priority based precode ratio (PBPR), was designed by changing the precode properties of the RaptorQ codes. The ratio of precode symbols to Luby-Transform symbols in the RaptorQ codes was changed to achieve different error correction capabilities for each priority group. The scheme with the higher number of precode symbols provided superior error-correction capabilities compared to those with fewer precode symbols. Both methods were empirically verified through simulation in the C++ programming language. The results demonstrated that the higher-importance class depicted a better error-correction capability than the lower-importance class.

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.

With the exponential growth of video traffic over wireless networked and embedded devices, mechanisms are needed to predict and control perceptual video quality to meet the quality of experience (QoE) requirements in an energy-efficient way. This paper proposes an energy-efficient QoE support framework for wireless video communications. It consists of two components: 1) a perceptual video quality model that allows the prediction of video quality in real-time and with low complexity, and 2) an application layer energy-efficient and content-aware forward error correction (FEC) scheme for preventing quality degradation caused by network packet losses. The perceptual video quality model characterizes factors related to video content as well as distortion caused by compression and transmission. Prediction of perceptual quality is achieved through a decision tree using a set of observable features from the compressed bitstream and the network. The proposed model can achieve prediction accuracy of 88.9% and 90.5% on two distinct testing sets. Based on the proposed quality model, a novel FEC scheme is introduced to protect video packets from losses during transmission. Given a user-defined perceptual quality requirement, the FEC scheme adjusts the level of protection for different components in a video stream to minimize network overhead. Simulation results show that the proposed FEC scheme can enhance the perceptual quality of videos. Compared to conventional FEC methods for video communications, the proposed FEC scheme can reduce network overhead by 41% on average.

We investigate the rate-compatible punctured convolutional (RCPC) codes concatenated with hierarchical QAM for designing a cross-layer unequal error protection scheme for H.264 coded sequences. We first divide the H.264 encoded video slices into three priority classes based on their relative importance. We investigate the system constraints and propose an optimization formulation to compute the optimal parameters of the proposed system for the given source significance information. An upper bound to the significance-weighted bit error rate in the proposed system is derived as a function of system parameters, including the code rate and geometry of the constellation. An example is given with design rules for H.264 video communications and 3.5-4 dB PSNR improvement over existing RCPC based techniques for AWGN wireless channels is shown through simulations.

Video streaming over wireless channel encounters many challenges due to the time-varying characteristics of wireless channels and limited network bandwidth. In this paper, we investigate an adaptive forward error correction (FEC) scheme for streaming the stored MPEG-4 FGS bit-stream from the video server to the clients over wireless channel. In this scheme, the base layer is transmitted reliably and the enhancement layer is protected with unequal error protection (UEP) scheme. Taking the fine-grained characteristics of FGS into account, we propose a decodable rate maximized criterion to optimally allocate the bit rate between the source rate and the channel coding rate and dynamically adapt to the varying network condition. Experimental results show that Compared with fixed unequal error protection (UEP) and equal error protection (EEP), our proposed method can provide a better performance.

Link adaptation is crucial in the upcoming broadband wireless systems, where there are stringent Quality of Service (QoS) requirements. It is well established in single antenna systems, whereas it is challenging and at the same time promising in Multiple Input Multiple Output (MIMO) communication. Changing the modulation order/coding scheme or switching between MIMO modes for adaptation is rather complex and requires high adaptive control overhead. As an alternative, error control coding, which is widely used in MIMO can be modified to make the system rate adaptive, with or without constellation change. In this paper, we present an adaptive transmission technique in Generalised Spatial Modulation (GSM) MIMO using Rate Compatible Punctured Convolutional (RCPC) codes. An antenna grouping method based on limited channel state information (CSI) feedback is used here to select the puncturing matrices and the active antennas. The system throughput and BER performance are analyzed for various channel selection and puncturing schemes.

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 chapter, we describe different forward error correction (FEC) schemes currently in use or suitable for use in optical communication systems. We start with the description of standard block codes. The state-of-the-art in optical communication systems standardized by the ITU employ concatenated Bose–Chaudhuri–Hocquenghem (BCH)/RS codes [1, 2]. The RS(255,239), in particular, has been used in a broad range of long-haul communication systems [1, 2], and it is commonly considered as the first-generation of FEC [3, 4]. The elementary FEC schemes (BCH, RS, or convolutional codes) may be combined to design more powerful FEC schemes, e.g., RS(255,239) + RS(255,233). Several classes of concatenation codes are listed in ITU-T G975.1. Different concatenation schemes, such as the concatenation of two RS codes or the concatenation of RS and convolutional codes, are commonly considered as second generation of FEC [3, 4].

This paper shows an important enhancement of TCP behavior over the IEEE 802.11b Wireless Local Area Network (WLAN) if a combination of a Forward Error Correction (FEC) scheme and a Snoop agent is added to the idle Repeat reQuest (RQ) mechanism inherently used by such technology. The FEC scheme has been improved with some smart cross-layer optimizations, and its operation adapts to the channel conditions. Besides, the aim of the Snoop agent is to back up the FEC, overcoming the deficiencies of its adaptation, which are mainly due to the high variability of the channel inside a typical office environment. A complete experimental approach has been followed, and exhaustive measurement campaigns have been carried out over a real platform to derive a large number of performance parameters. Both methods have been implemented as modules belonging to a generic layer-two Performance Enhancing Proxy (PEP).

The utilization of forward error correction (FEC) schemes for stereo video streaming is investigated. Stereo video is categorized in 3 layers and each layer is protected with different protection ratios for efficient streaming. Systematic Reed-Solomon (RS) and Luby Transform (LT) codes are utilized as the error protection schemes. Detailed simulations are performed in order to observe the optimum unequal error protection (UEP) strategies for the defined video layers. Moreover, as a result of these simulations the performance comparison of RS and LT codes for video streaming is provided.

Data with varied reliability requirement, for example, digitally encoded speech, need a coding scheme that can provide different levels of protection. An error in the most significant bits can be more damaging than an error in the least significant bits. Therefore, channel coding with unequal error protection (UEP) is needed. Rate-compatible punctured convolutional (RCPC) codes can be used to apply unequal error protection. In this paper, the serial list Viterbi algorithm (SLVA) decoding with UEP is studied. We observed that the error performance of SLVA decoding depends strongly on the puncturing provided to the least significant bits. Limiting the SLVA search window to cover the most important bits, the SLVA is able to correct the errors occurring in the most significant bits more efficiently. The effect of location of the most important bits either in the beginning or in the end the sequence was evaluated. When the most important bits are located at the beginning of the information sequence, the SLVA search window should be expanded by few bits of the area where these bits are located in order to achieve the best performance with SLVA decoding. The effect of CRC code for error detection was also studied. The length of the CRC code is a crucial factor, since the probability of undetected errors should be kept low in order to. achieve the best performance with a limited SLVA search window.

In wireless relay networks (WRNs), multiple source nodes communicate with a single destination node through a common relay network. Different source nodes may have different error protection or recovery time requirements. In this paper, we focus on unequal error protection (UEP) distributed network coding (DNC) design for WRNs. Specifically, we propose a continuous UEP method based on fountain codes with the objective of satisfying the UEP or unequal recovery time (URT) requirements. Then based upon this UEP method, we develop an adaptive UEP DNC scheme to realize adaptive UEP in WRNs. We analyze the properties of the proposed adaptive UEP DNC scheme and derive the upper and lower bit error rate (BER) bounds for it over Rayleigh fading channels under maximum-likelihood (ML) decoding. Simulation results show that the proposed adaptive UEP DNC scheme has desirable UEP and URT properties. The transmitted data from the source nodes in different protection groups can be recovered successfully under their performance requirements in a shorter time by using the adaptive UEP DNC scheme.

From the fact that the first bit among the four coded bits at the rate compatible punctured convolutional (RCPC) coding defined in the Eureka 147 DAB system is not punctured, this paper proposes a new DAB system model that substitutes the turbo code for the existing RCPC code without modifying the puncturing procedure. The performance of a new system is compared to that of the, conventional system in the fast information channel (FIC) and main service channel (MSC) for DAB transmission mode I on the Rician fading channel and the Rayleigh fading channel.