Unequal Error Protection Codes Research Articles

A novel boundary constraint LT codes with unequal error protection property

The LT-based Unequal Error Protection (UEP) codes are invented to provide UEP property in different parts of the data. But in the traditional LT-based UEP codes, a phenomenon called Unequal Recovery Time (URT) always by product.For the ensembles in which different parts of data with diverse timeliness requirements, the URT property is useful. Nevertheless, for most cases, the URT properties are not necessary and would leading to lower transmission efficiencies of the overall LT-based UEP codes. In order to provide both UEP property and high transmission efficiency, as new class of LT-based UEP codes is proposed. On the basis of the coding structure proposed in our earlier research, we proposed a novel encoding algorithm. In which algorithm, the selection method of input symbols is divided into two ways according to the boundary degree, then the proposed codes are named as boundary constraint codes. By given the method to determine the boundary degree, and derive the selection probabilities related to the boundary degree, the proposed boundary constraint UEP codes can be easily designed to suit for various UEP requirements. Numerical results demonstrate that the proposed boundary constraint codes can provide higher transmission efficiency while providing the same UEP property as the conventional LT-based UEP codes.

Autoencoder-Based Unequal Error Protection Codes

We present a novel autoencoder-based approach for designing codes that provide unequal error protection (UEP) capabilities. The proposed approach, based on a generalization of an autoencoder loss function, provides a versatile framework for the design of message-wise and bit-wise UEP codes. Using an associated weight vector, the generalized loss function can be used to trade off error probabilities corresponding to different importance classes and to explore the region of achievable error probabilities. For message-wise UEP, we compare the proposed autoencoder-based UEP codes with a union of random coset codes. For bit-wise UEP, the proposed codes are compared with UEP rateless spinal codes and the superposition of random Gaussian codes. In all cases, the autoencoder-based codes show superior performance while providing design simplicity and flexibility in trading off error protection among different importance classes.

Distributed Hypothesis Testing Based on Unequal-Error Protection Codes

Coding and testing schemes for binary hypothesis testing over noisy networks are proposed and their corresponding type-II error exponents are derived. When communication is over a discrete memoryless channel (DMC), our scheme combines Shimokawa-Han-Amari's hypothesis testing scheme with Borade-Nakiboglu-Zheng's unequal error protection (UEP) for channel coding where source and channel codewords are simultaneously decoded. The resulting exponent is optimal for the newly introduced class of generalized testing against conditional independence. When communication is over a multi-access channel (MAC), our scheme combines hybrid coding with UEP. The resulting error exponent over the MAC is optimal in the case of generalized testing against conditional independence with independent observations at the two sensors when the MAC decomposes into two individual DMCs. In this case, separate source-channel coding is sufficient and no UEP is required. This same conclusion holds also under arbitrarily correlated sensor observations when testing is against independence.

A new class of LT-based UEP rateless codes for satellite image data transmission

Satellite communication systems with the long transmission distance, dynamic channel states and limited energy consumption properties. To improve the image data transmission efficiency in the satellite communication systems, a class of rateless codes which can provide unequal error protection (UEP) property and equal water-fall region performance is proposed in this paper. As existing Luby Transform (LT)-based UEP codes with a property termed unequal recovery time (URT), which means that the data with different reliability requirements would be recovered with different overheads, which property would leading to a lower transmission efficiencies when all the portions of data have to be recovered. To overcome this drawback of existing UEP codes, the proposed UEP codes are carefully designed to provide equal water-fall region performances of all the portions of data. By using the well-known asymptotically analysis tool named as And-Or Tree, the asymptotic error performances of the proposed codes are given, and compared with the conventional LT-based UEP codes. All the theoretical analysis results and numerical results all prove that compared with conventional LT-based UEP codes, the proposed codes can provide higher transmission efficiency in the image data transmission in satellite communication systems.

Adaptive Modulation and Superposition Coding for MIMO Data Transmission Using Unequal Error Protection and Ordered Successive Interference Cancellation Techniques

This paper proposes and discusses an efficient multiple input multiple output (MIMO) system for adaptive modulation coding (AMC) based on unequal error protection (UEP) and superposition coding (SPC) by exploiting the features of sub channel partitioning. Using AMC, an appropriate order of modulation and code rate to suit the channel state information (CSI) can be selected. The realization of UEP is achieved through adaptive allocation and transmission of high and low-priority data signals over high and low quality sub channels respectively. A multistage decoding (MSD) receiver with the ordered successive interference cancellation (OSIC) technique is employed in the receiver by using two linear receiver signal combiner (RSC) techniques: zero-forcing (ZF) and minimum mean square error (MMSE). The data priority can be distinguished by the signal-to-noise ratio (SNR) and can be categorized as mode-B and mode-G. The simulation results show that the SNR performance enhancement for the UEP- MIMO scheme is approximately 9.4 dB compared to the others schemes. In addition, for the UEP-MIMO scheme, the overall data system transmission from mode-B outperforms that of mode-G with SNR gains of 8.2 dB compared to the 7.5 dB for the UEP-SISO scheme. Also, MMSE-SPC also outperforms the ZF-SPC with a 3 dB SNR at a bit error rate (BER) of 10-3.

Turbo Unequal Error Protection Codes with Multiple Protection Levels

Most existing Turbo unequal error protection (UEP) codes provide two error protection levels at the cost of extending the block size of the codeword or increasing the computational complexity. This paper proposes two novel Turbo UEP coding schemes, which provide multiple error protection levels for information bits, according to their different sensitivities to the channel noise. By per- muting the information bits and designing the puncturing scheme, multiple error protection levels can be achieved using one encoder without increasing the computational complexity. In addition, the coding rate of the proposed Turbo UEP schemes can be chosen from 1/3 to 1/2. Experimental results show that the information bits with a high protection level resist noise more effectively than those with a low protection level. The proposed UEP schemes provide better capability of error protection for the entire information, compared with the Turbo equal error protection (EEP) schemes and the existing Turbo UEP schemes.

Unequal Error Protection Codes Derived from Double Error Correction Orthogonal Latin Square Codes

In recent years, there has been a growing interest in multi-bit error correction codes (ECCs) to protect SRAM memories. This has been caused by the increased number of multiple errors that memories suffer as technology scales. To be suitable to protect an SRAM memory, an ECC has to be decodable in parallel and with low latency. Among the codes proposed for memory protection are orthogonal latin square (OLS) codes that provide low latency decoding and a modular construction. For some applications, like multimedia or signal processing, the effect of errors on the memory bits can be very different depending on their position on the word. Therefore, in these cases, it is more effective to provide different degrees of error correction for the different bits. This is done with unequal error protection (UEP) codes. In this paper, UEP codes are derived from double error correction (DEC) OLS codes. The derived codes are implemented for an FPGA platform to evaluate the decoder complexity and latency. The results show that the new codes can be implemented with lower decoding delay than traditional SEC-DED codes and with a cost similar to that of both DEC OLS and SEC-DED codes.

Further Exploration of Convolutional Encoders for Unequal Error Protection and New UEP Convolutional Codes

In this paper, the unequal error protection (UEP) capability of convolutional encoders, in terms of the separation vector, is studied from an algebraic viewpoint. A simple procedure is presented for constructing a generator matrix, which is basic and has the largest separation vector for every convolutional code. Such a generator matrix would be desirable, since the corresponding encoder not only achieves UEP optimality, but also avoids undesired catastrophic error propagation. In addition, canonical generator matrices, which are both basic and reduced, are even more preferable for encoding, since they attain the lowest complexity for Viterbi decoding. However, the direct transformation from a UEP-optimal generator matrix to a canonical generator matrix may come with an unexpected loss of the separation vector. We also propose a specific type of transformation matrix that reduces the external degrees of the generator matrices, from which canonical generator matrices can be constructed that include the mitigated degradation of the separation vector. Finally, beneficial UEP convolutional codes that achieve the maximum free distances for the given code parameters are provided.

Unequal error protection codes derived from SEC‐DED codes

Error correction codes are commonly used to protect the data stored in memories from errors. Among the codes used, single error correction double error detection (SEC-DED) codes are probably the most common due to their simplicity. In some applications, the importance of the bits is different, being some of them critical while others can tolerate some errors. This is the case, for example, in some multimedia and signal processing systems. For those applications, unequal error protection (UEP) codes that provide different protection for different bits can be used. In many cases, the bits that require extra protection are only a few. Therefore, it would be convenient to use a traditional code extended to provide additional protection for a few bits. A simple method to derive UEP codes from SEC-DED codes is presented. The proposed UEP codes protect a few bits against double errors and behave as SEC-DED codes for the rest. Encoding and decoding complexity is only slightly larger than that of an SEC-DED code and the implementation is a simple modification of the SEC-DED implementation.

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.

Integer programming approach to unequal error protection coding for multiuser broadcast channels

In this study, an integer programming approach is introduced to construct unequal error protection (UEP) codes for a multiuser broadcast communication system. The authors establish integer programming models for both binary and non-binary UEP codes. The results show that optimal UEP codes can be constructed such that their code lengths achieve the integer programming bounds. Based on the bounds, the authors investigate asymptotic behaviour of code rates with symbols in 𝔾𝔽(q), and the authors present performance analysis of multiuser communications over a degraded broadcast channel with the optimal UEP codes.

Coded Collaborative Spectrum Sensing With Joint Channel Decoding and Decision Fusion

This paper considers the integration of channel decoding with fusion based decision, for coded collaborative spectrum sensing (CSS) employing local Neyman-Pearson (NP) testing at each sensor. We derive a belief-propagation (BP) algorithm for joint channel decoding and decision fusion (JCDDF), based on a factor graph model for coded CSS schemes. Using the Lloyd-Max method, we also propose a new methodology for the local sensor to quantize its observation. The design of the quantizer embeds the binary NP test outcome in the quantization bits. Using the JCDDF algorithm, we show that coded CSS paired even with a short (8,4) extended Hamming code outperforms not only uncoded CSS, but also schemes where channel decoding and decision fusion are executed separately. Then, we consider the design of good channel codes for such CSS schemes. We demonstrate that the JCDDF algorithm employing unequal error protection (UEP) coding improves performance and outperforms equal error protection coding. Furthermore, we present a simple code search algorithm for identifying short UEP codes. Using such UEP codes, we finally show that a performance improvement over uncoded CSS can be attained also without bandwidth expansion using higher order modulations.

Linear unequal error protection codes based on terminated convolutional codes

Convolutional codes which are terminated by direct truncation (DT) and zero tail termination provide unequal error protection. When DT terminated convolutional codes are used to encode short messages, they have interesting error protection properties. Such codes match the significance of the output bits of common quantizers and therefore lead to a low mean square error (MSE) when they are used to encode quantizer outputs which are transmitted via a noisy digital communication system. A code construction method that allows adapting the code to the channel is introduced, which is based on time-varying convolutional codes. We can show by simulations that DT terminated convolutional codes lead to a lower MSE than standard block codes for all channel conditions. Furthermore, we develop an MSE approximation which is based on an upper bound on the error probability per information bit. By means of this MSE approximation, we compare the convolutional codes to linear unequal error protection code construction methods from the literature for code dimensions which are relevant in analog to digital conversion systems. In numerous situations, the DT terminated convolutional codes have the lowest MSE among all codes.

A new leader-based multicast scheme with a Raptor code in IEEE 802.11 multi-rate WLANs

Abstract Multimedia streaming using a multicast scheme over IEEE 802.11 multi-rate wireless local area networks (WLANs) faces many challenges owing to the heterogeneous channel conditions of receivers. Although many multicast schemes have been proposed to support multimedia streaming over multi-rate WLANs, those schemes do not deal with multicast transmission efficiently. In this paper, a new leader-based multicast scheme with a Raptor code is proposed. The proposed scheme consists of a leader selection block, a scalable video coding (SVC) block with unequal error protection (UEP), and a link adaptation block with a Raptor code. In the proposed scheme, one of the multicast group members is selected as a multicast group leader according to a leader cost, and then link adaptation operates between the multicast transmitter and the multicast group leader. In addition, SVC, UEP, and Raptor code mechanisms are applied to guarantee the minimum required performance of multicast group members. The proposed scheme aims to enhance the link utilization and guarantees the minimum quality-of-service requirement of multicast group members. Simulation results show that the proposed scheme performs better than previous multicast schemes.

Asymptotic Analysis and Optimization for Generalized Distributed Fountain Codes

A novel generic fountain coding scheme for multiple access networks over erasure channels is proposed and it can be applied to several instances. Moreover, asymptotic analysis using And-Or tree analysis technique is evaluated and an efficient joint optimization method employing linear and nonlinear programs is presented. Furthermore, selective distributed Luby Transform (SDLT) codes and unequal error protection (UEP) codes are evaluated as two special cases. Simulation results reveal that the proposed coding scheme can reduce decoding overhead and provide strong UEP property across sources.

A Novel Turbo Unequal Error Protection Scheme for Image Steganography

An Unequal Error Protection (UEP) scheme for image steganography is proposed in this paper. When stego images are transmitted through a noisy channel, the embedded message may be more sensitive to noise than the cover message. Therefore, we propose a Turbo UEP coding scheme for steganographic communication in a noisy channel, which provides higher error protection for the embedded message and lower error protection for the cover message. Simulations show that this coding scheme provides different error protection levels in one coding process and maintains the coding rate constant. In addition, an application scheme of the proposed Turbo UEP code for steganographic communication is presented, and the experimental results show that the extracted secret images have better quality than the cover images after decoding.

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.

A Serial Unequal Error Protection Codes System Using MMSE-FDE for Fading Channels

In our previous research, to achieve unequal error protection (UEP), we proposed a scheme which encodes the data by randomly switching between several codes which use different signal constellations and showed the effectiveness in AWGN channels. In this paper, we propose our UEP system using MMSE-FDE (frequency- domain equalization based on the minimum mean square error criterion) for fast and selective fading by using the fact that importance levels are changed every few symbols, i.e., every block, in the proposed system. We confirmed the improvement in BER performance and the effectiveness of adaptive equalization for the proposed system in fading channels. As a result, we showed that a UEP system is realizable in mobile telecommunications environments.

Concatenated Block Codes for Unequal Error Protection of Embedded Bit Streams

A state-of-the-art progressive source encoder is combined with a concatenated block coding mechanism to produce a robust source transmission system for embedded bit streams. The proposed scheme efficiently trades off the available total bit budget between information bits and parity bits through efficient information block size adjustment, concatenated block coding, and random block interleavers. The objective is to create embedded codewords such that, for a particular information block, the necessary protection is obtained via multiple channel encodings, contrary to the conventional methods that use a single code rate per information block. This way, a more flexible protection scheme is obtained. The information block size and concatenated coding rates are judiciously chosen to maximize system performance, subject to a total bit budget. The set of codes is usually created by puncturing a low-rate mother code so that a single encoder-decoder pair is used. The proposed scheme is shown to effectively enlarge this code set by providing more protection levels than is possible using the code rate set directly. At the expense of complexity, average system performance is shown to be significantly better than that of several known comparison systems, particularly at higher channel bit error rates.

Improved Design of Unequal Error Protection LDPC Codes

We propose an improved method for designing unequal error protection (UEP) low-density parity-check (LDPC) codes. The method is based on density evolution. The degree distribution with the best UEP properties is found, under the constraint that the threshold should not exceed the threshold of a non-UEP code plus some threshold offset. For different codeword lengths and different construction algorithms, we search for good threshold offsets for the UEP code design. The choice of the threshold offset is based on the average a posteriori variable node mutual information. Simulations reveal the counter intuitive result that the short-to-medium length codes designed with a suitable threshold offset all outperform the corresponding non-UEP codes in terms of average bit-error rate. The proposed codes are also compared to other UEP-LDPC codes found in the literature.