Unequal Error Protection Rateless Codes Research Articles

Generalized Unequal Error Protection Rateless Codes for Distributed Wireless Relay Networks

A generalization of unequal error protection (UEP) rateless codes and distributed rateless codes for distributed relay networks is proposed. We consider a two-hop relaying network where a single source transmits UEP rateless coded data to a destination via multiple relays. At the relays, the UEP rateless coded symbols are re-encoded by distributed rateless codes (DRC) to minimize the redundancy at the second hop. Previously introduced UEP rateless codes (URC) have supported a limited number of importance classes, mostly two classes, and targeted importance levels suited to a specific application. In this paper, however, we formulate an optimization problem to provide optimal URC in terms of the symbol error rate (SER) given any specific number and strengths of importance levels. Next, another optimization is proposed to obtain DRC with the minimum SER at a given overhead, which utilizes information of common symbols among the relays. The optimization methods are based on the AND-OR tree analysis and sequential quadratic programming. In addition, we evaluate the minimum achievable end-to-end symbol error rates over the wireless relay networks.

Optimization of unequal error protection rateless codes for multimedia multicasting

Rateless codes have been shown to be able to provide greater flexibility and efficiency than fixed-rate codes for multicast applications. In the following, we optimize rateless codes for unequal error protection (UEP) for multimedia multicasting to a set of heterogeneous users. The proposed designs have the objectives of providing either guaranteed or best-effort quality of service (QoS). A randomly interleaved rateless encoder is proposed whereby users only need to decode symbols up to their own QoS level. The proposed coder is optimized based on measured transmission properties of standardized raptor codes over wireless channels. It is shown that a guaranteed QoS problem formulation can be transformed into a convex optimization problem, yielding a globally optimal solution. Numerical results demonstrate that the proposed optimized random interleaved UEP rateless coder's performance compares favorably with that of other recently proposed UEP rateless codes.

Enhanced unequal error protection coding scheme of Luby transform codes

A Luby transform (LT) coding scheme providing unequal error protection (UEP) is proposed. As an enhanced method, the proposed UEP-LT coding scheme can be easily applied to the existing UEP rateless codes to achieve further bit error rate (BER) performance improvement. In the proposed UEP-LT encoder, a number of the so-called fixed symbols are added to the original source symbols. The level of importance of them can be assigned as that of any subset of the original source symbols. When the encoded symbols are generated, the proposed encoder only XOR the original source symbols. Therefore the efficiency of the UEP-LT codes remains unchanged. It is found that this can benefit the belief propagation decoding. Using the And–Or tree analysis technique, the asymptotic BER performance of the proposed method is analysed in detail. Compared with some existing UEP rateless codes, the asymptotic BERs of the proposed UEP-LT codes are much lower when the parameters are properly chosen. Besides, the proposed method needs less decoding iterations to converge, which means the source symbols can be recovered earlier. Simulation results show that the BER performances are improved when the proposed scheme is applied to the existing UEP rateless codes.

A Novel Structure of HTTP Adaptive Streaming Based on Unequal Error Protection Rateless Code

A Novel Structure of HTTP Adaptive Streaming Based on Unequal Error Protection Rateless Code

Unequal Error Protection for Streaming Media Based on Rateless Codes

This paper presents an Unequal Error Protection (UEP) method for streaming media. Previous researches have shown that UEP rateless codes can provide a low-complexity solution for downloading scalable information. However, the randomized generator of rateless codes leads to uncertainty of decoding probability and decoding priority of input data, and thus it is not suitable for streaming applications. In this paper, a novel UEP method is presented for streaming media. The proposed method, which consists of a hierarchical coding graph as well as low-complexity encoding and decoding operations, preserves the advantage of the UEP rateless codes and characterizes the decoding probability and decoding priority by formulas. The proposed hierarchical coding graph guarantees that high-priority input data are recovered before low-priority ones, so important information can be recovered with low latency, low computation, and high probability. In addition, data in different layers of the proposed UEP are dependently encoded, so that data in different layers can help decode each other. For heterogeneous clients, the proposed UEP codes can help a decoder with recovery of different amount of information according to the network condition and computation ability. Besides, we also extend the proposed UEP codes to a rateless version for downloading of media. Compared with the previous finite-length and rateless UEP codes, our method can recover more high-priority data even in serious packet loss rate (PLR), and the decoding order of data can be assigned by the server.

Expanding window fountain codes for unequal error protection

A novel approach to provide unequal error protection (UEP) using rateless codes over erasure channels, named Expanding Window Fountain (EWF) codes, is developed and discussed. EWF codes use a windowing technique rather than a weighted (non-uniform) selection of input symbols to achieve UEP property. The windowing approach introduces additional parameters in the UEP rateless code design, making it more general and flexible than the weighted approach. Furthermore, the windowing approach provides better performance of UEP scheme, which is confirmed both theoretically and experimentally.