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In this letter, we propose a new scheme to construct low-density parity-check (LDPC) codes that are suitable for unequal error protection (UEP). We derive UEP density evolution (UDE) formulas for the proposed ensemble over the binary erasure channel (BEC). Using the UDE formulas, high performance UEP codes can be found. Simulation results depict an improvement in the bit error rate of more important bits in comparison with previous results on UEP-LDPC codes. 相似文献
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《Communications, IEEE Transactions on》2006,54(6):994-1005
We introduce a new family of unequal error protection (UEP) codes, based on low-density parity-check (LDPC) component codes and Plotkin-type constructions. The codes are decoded iteratively in multiple stages, and the order of decoding determines the level of error protection. The level of UEP among the code bits is also influenced by the choice of the LDPC component codes and by some new reliability features incorporated into the decoding process. The proposed scheme offers a very good tradeoff between code performance on one side and encoding/decoding and storage complexity on the other side. The novel approach to UEP also allows for finding simple approximations for the achievable degrees of UEP, which can be used to govern practical code design implementations. 相似文献
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Rateless Codes With Unequal Error Protection Property 总被引:2,自引:0,他引:2
Rahnavard N. Vellambi B.N. Fekri F. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》2007,53(4):1521-1532
In this correspondence, a generalization of rateless codes is proposed. The proposed codes provide unequal error protection (UEP). The asymptotic properties of these codes under the iterative decoding are investigated. Moreover, upper and lower bounds on maximum-likelihood (ML) decoding error probabilities of finite-length LT and Raptor codes for both equal and unequal error protection schemes are derived. Further, our work is verified with simulations. Simulation results indicate that the proposed codes provide desirable UEP. We also note that the UEP property does not impose a considerable drawback on the overall performance of the codes. Moreover, we discuss that the proposed codes can provide unequal recovery time (URT). This means that given a target bit error rate, different parts of information bits can be decoded after receiving different amounts of encoded bits. This implies that the information bits can be recovered in a progressive manner. This URT property may be used for sequential data recovery in video/audio streaming 相似文献
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针对多媒体无线通信的特点,提出了一种结合自适应纠错技术与联合优化技术的新策略,充分考虑了联合编码的自适应纠错特性和联合优化特性,分析了优化的信源编码算法和优化的信道编码算法.实验仿真结果表明,该方法能够使图像数据在高码率下达到较好的抗噪性能. 相似文献
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具有不等错误保护特性的LDPC 编码调制方案 总被引:1,自引:0,他引:1
针对LDPC(low-density parity-check)编码调制系统,提出了一种新的具有不等错误保护特性的调制方案,在一个码字内,利用不同的调制方式对于重要的比特给予较强的保护,对于次要的比特给予较弱的保护,该方案既适用于非规则LDPC码,也适用于规则LDPC码。计算机仿真结果表明,新方案的性能是传统16QAM及4QAM的折衷,当采用1/2码率时,其频带利用率与8PSK相同,但是误码率性能优于8PSK。新方案的性能优于现有文献中基于比特可靠性的调制映射方案,并采用EXIT(extrinsic information transfer)图对新方案的优异性能给出了解释。 相似文献
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介绍了非规则准循环OOC-LDPC码的构造,并将其应用到图像传输中,根据SPIHT压缩图像编码后的码流具有渐进性的特点,进行不等差错保护。在AWGN信道下仿真结果表明,非规则准循环OOC-LDPC码具有很好的纠错能力和不等差错保护特性。 相似文献
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Chung-Hsuan Wang 《Communications Letters, IEEE》2007,11(9):744-746
In this letter, rate-compatible punctured convolutional (RCPC) codes are further investigated for the application to unequal error protection (UEP). Besides the rate-compatible restriction, we show that puncturing tables should be switched in a special way called soft-switching to guarantee the designed UEP performance. A new data-multiplexing scheme is also proposed for RCPC codes which can achieve similar UEP performance as the conventional scheme but requires no extra zero-padding for frame termination to improve the system throughput. 相似文献
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为了提高图像在无线信道传输的有效性和可靠性,提出一种优化的LDPC信道编码的不等保护图像传输系统——用PEG方法直接生成列重增加的校验矩阵的系统编码。指出由于LDPC码的不规则特性使其对较为敏感的重要信息给予更多的保护,将整体传输分为不同的保护级别进行处理。仿真结果显示改进的方案在客观的PSNR上和主观的视觉效果上都较之等保护措施有明显的改进。 相似文献
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The third generation partnership project (3GPP) and digital video broadcasting-handheld standards recommend systematic Raptor codes as application-layer forward error correction for reliable transmission of multimedia data. In all previous studies on systematic Raptor codes, equal error protection for all data was considered. However, in many applications, multimedia data requires unequal error protection (UEP) that provides different levels of protection to different parts of multimedia data. In this paper, we propose a new design method for Raptor codes that provide both UEP and systematic properties over binary erasure channels. Numerical results show that the proposed UEP design is effective for reliable multi-level protection. 相似文献
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Chung-Hsuan Wang Mao-Ching Chiu Chi-chao Chao 《IEEE transactions on information theory / Professional Technical Group on Information Theory》2010,56(1):296-315
In this paper, convolutional codes are studied for unequal error protection (UEP) from an algebraic theoretical viewpoint. We first show that for every convolutional code there exists at least one optimal generator matrix with respect to UEP. The UEP optimality of convolutional encoders is then combined with several algebraic properties, e.g., systematic, basic, canonical, and minimal, to establish the fundamentals of convolutional codes for UEP. In addition, a generic lower bound on the length of a UEP convolutional code is proposed. Good UEP codes with their lengths equal to the derived lower bound are obtained by computer search. 相似文献
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Lin M.-C. Lin S. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》1988,34(4):867-871
The unequal error correction capabilities of binary cyclic codes of composite length are investigated. Under certain conditions, direct sums of concatenated codes have unequal error correction capabilities. By a modified Hartmann and Tzeng (1973) algorithm, it is shown that a binary cyclic code of composite length is equivalent to the direct sum of concatenated codes. With this, some binary cyclic unequal error protection (UEP) codes are constructed. Finally, the authors present a class of two-level UEP cyclic direct-sum codes which provide error correction capabilities higher than those guaranteed by the Blokh-Zyablov (1974) constructions 相似文献
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Chung-Hsuan Wang Yi-Hsin Lin 《Communications, IEEE Transactions on》2008,56(9):1385-1389
In this paper, puncturing and path pruning are combined for convolutional codes to construct a new coding scheme for unequal error protection (UEP), called the hybrid punctured and path-pruned convolutional codes. From an algebraic viewpoint, we show that the hybrid codes not only inherit all the advantages of the conventional rate-compatible punctured convolutional codes and path-compatible pruned convolutional codes but also can provide more flexible choices of protection capability for UEP. In addition, a data-multiplexing scheme originally proposed for path-pruned codes which can guarantee smooth transition between rates without additional zero-padding for frame termination is proven applicable to the hybrid codes to improve the system throughput. 相似文献
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New results on self-orthogonal unequal error protection codes 总被引:1,自引:0,他引:1
Zhi Chen Pingzhi Fan Fan Jin 《IEEE transactions on information theory / Professional Technical Group on Information Theory》1990,36(5):1141-1144
A lower bound on the length of binary self-orthogonal unequal error protection (UEP) codes is derived, and two design procedures for constructing optimal self-orthogonal UEP codes are proposed. With this lower bound, known self-orthogonal UEP codes can be evaluated. It is pointed out that, for given values of minimum distance and code rate, the self-orthogonal codes must be relatively long, so optimal self-orthogonal codes are not optimal in general. But self-orthogonal codes can be implemented simply, and they have error-correcting capabilities beyond those guaranteed by their minimum distance. These properties can be viewed as a partial compensation for using self-orthogonal codes 相似文献
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The modified Plotkin bound for unequal error protection (UEP) codes is derived. Based on the separation vector of UEP codes, the authors adopt the average separation of all information digits of a given UEP code, and replacing it with minimum distance in the normal Plotkin bound leads to the new bound, which is valid for both linear and nonlinear UEP codes 相似文献
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Chung-Hsuan Wang Chi-Chao Chao 《Communications, IEEE Transactions on》2002,50(2):213-224
Path pruning, a new coding concept to achieve free distance enlargement for convolutional codes, is proposed. Through path pruning, every convolutional code can be used for unequal error protection (UEP), no matter whether it is originally a UEP code. To avoid undesired path discontinuity and reduce possible path distance loss, a cascaded implementation together with a path-compatible criterion is proposed, under which path-compatible pruned convolutional (PCPC) codes are constructed. Necessary and sufficient conditions are also derived for a subclass of PCPC codes whose decoding can be done by a single decoder for the parent code. Finally, some PCPC codes with good UEP capabilities found by computer search are given 相似文献