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针对图像数据在无线信道传输中存在的可靠性与稳定性较差等问题,提出了一种自适应不等差错保护的联合信源信道编码方案。采用基于小波变换的信源编码对原始图像数据进行压缩处理,并对生成的码流进行重要程度划分;基于LDPC码对划分好的码流数据采取不同等级的差错保护措施;最终,反馈信道状况信息给信道编码器并进行码率的自适应调整,从而实现高质量的图像信号传输。仿真实验结果表明,提出的算法具有更高的峰值信噪比(PSNR),相比EEP算法及DE-UEP算法,其PSNR值有0.2~0.4 dB的提升。 相似文献
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RS+卷积级联码在无线本地环路中的性能分析 总被引:1,自引:0,他引:1
本文描述了一种适用于无线本地环路信道编译码器的编码方案,即采用(2,1,23)卷积码为内编码,GF(24)域上的RS(15,9,7)码为外编码的级联码,并对组联码的参数选取、误码性能进行了分析和仿真,最后提出了硬件设计方案。这是一种实用可行的编码方案。 相似文献
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介绍了现有不等差错保护技术在图像通信中的运用.在MPEG-4标准和Turbo码的基础上实现了基于感兴趣区域的不等差错保护技术.在网络状况不良的情况下较大地降低了感兴趣区域信息的信道传输误码,提高了恢复图像的主观质量,在有感兴趣区域的图像或视频的传输(如无线可视电话业务)中可得到运用. 相似文献
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RS+卷积极联码在无线本地环路中的性能分析 总被引:1,自引:0,他引:1
本文描述了一种适用于无线本地环路信道编译码器的编码方案,即采用(2,1,3)卷积码为内编码,GF(2^4)域上的RS(15,9,7)码外编码的级联码,并对级联码的参数选取,误码性能进行了分析和仿真,最后提出了硬件设计方案。这是一种实用可行的编码方案。 相似文献
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针对传统不等差错保护(Unequal Error Protection,UEP)算法在加性高斯白噪声信道中存在误码平台的问题,提出了一种改进的扩展窗喷泉码(Expanding Window Fountain,EWF)编码算法。通过为不同重要等级数据加窗的方式,使得重要等级较高的信息节点能够以更高的概率连接至更多的校验节点。在编码过程中分开记录不同窗内信息节点的度数值,并优化校验节点选取信息节点的方式,使得度数值相对较小的信息节点始终能被优先选取,从而提高了每个窗内信息节点的平均度数值,为各重要等级的数据提供了额外的增益。仿真结果表明,改进的EWF算法可将不同等级数据的误码平台降低1~2个数量级,且数据的等级越高,保护性能越强。 相似文献
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In this paper, we consider real-time video coding and transmission over packet-switched wireless IP networks, such as WLAN,
using RCPT codes and joint source-channel coding (JSCC) with concentration on a packet-by-packet adaptive scheme. We present
a systematic design methodology to enable the applicability of JSCC techniques. The performance of H.263+ video coding and
transmission over wireless channel modeled as slow Rician fading channels using this approach is studied. Results indicate
that a packet-by-packet adaptive RCPT-JSCC approach is of significant advantage for real-time video applications and leads
to more acceptable video delivery quality over interference-limited and time-varying wireless networks. 相似文献
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Reliable transmission of images and video over wireless networks must address both potentially limited bandwidths and the possibilities of loss. When bandwidth sufficient to transmit the bit stream is unavailable on a single channel, the data can be partitioned over multiple channels with possibly unequal bandwidths and error characteristics at the expense of more complex channel coding (i.e., error correction). This paper addresses the problem of efficiently channel coding and partitioning pre-encoded image and video bit streams into substreams for transmission over multiple channels with unequal and time-varying characteristics. Within channels, error protection is unequally applied based on both data decoding priority and channel packet loss rates, while cross-channel coding addresses channel failures. In comparison with conventional product codes, the resulting product code does not restrict the total encoded data to a rectangular structure; rather, the data in each channel is adaptively coded according to the channel's varying conditions. The coding and partitioning are optimized to achieve two performance criteria: maximum bandwidth efficiency and minimum delay. Simulation results demonstrate that this approach is effective under a variety of channel conditions and for a broad range of source material. 相似文献
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MC‐CDMA, a multicarrier (MC) modulation scheme based on code division multiple access (CDMA), is the most likely candidate for the next generation of mobile radio communications. The rate compatible punctured turbo (RCPT) coded hybrid automatic repeat request (HARQ) has been found to give improved throughput performance in a direct sequence (DS) CDMA system. However, the extent to which the RCPT HARQ improves the throughput performance of an MC‐CDMA system has not been fully understood. In this paper, we apply the RCPT HARQ to MC‐CDMA and evaluate by computer simulations its performance in a frequency selective Rayleigh fading channel. We found that the performance of RCPT HARQ MC‐CDMA is almost insensitive to channel characteristics. The performance can be drastically improved with receive diversity combined with space‐time transmit diversity. In addition, the comparison of RCPT HARQ MC‐CDMA, orthogonal frequency division multiplexing, and DS‐CDMA shows that under similar conditions the throughput of MC‐CDMA is the best in a frequency selective fading channel. 相似文献
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混合自动重传请求(ARQ)作为一种差错控制技术被采纳为3GPP长期演进项目(LTE)的关键技术。基于速率兼容截断Turbo(RCPT)编码的混合ARQ算法,因其性能优异、实现复杂度低而被广泛关注。传统混合ARQ算法主要包括Chase合并方式混合ARQ,其在高信噪比条件下提供较大的性能增益;以及增量冗余(IR)方式混合ARQ,其在低信噪比条件下提供了更精确的速率控制。本文结合现有方法提出了一种基于RCPT编码的自适应选择合并混合ARQ算法,它在不同信噪比条件下自适应地选择Chase合并方式混合ARQ与IR方式混合ARQ,并且在接收端自适应地选择合并可靠性较高的传输码块。本文对其在瑞利衰落信道中的性能作了理论分析,并且进行了仿真,同时与传统的Chase合并方式混合ARQ以及IR方式混合ARQ作了性能比较。比较结果显示本文的算法在瑞利信道中比传统算法具有更为优异的性能以及相似的复杂度。 相似文献
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无线视频传输容错算法研究新进展 总被引:9,自引:2,他引:9
视频信号经过压缩编码后通过Rayleigh衰减无线信道传输,容易受到突发性错误的影响,造成视频传输质量下降。容错(error resilience)是保证无线视频传输质量的重要措施。本文首先对几种无线信道模型进行了概括与比较,然后总结了各种容错算法的优缺点和最新研究进展情况。重点讨论了在传输层实施的前向纠错编码(FEC)和反馈差错控制,在编码器端根据不同的信道传输特性所采用的容错算法,包括帧内刷新、长期限存储、分层编码和多描述编码。本文还通过一种传输方案对容错策略的组合实施情况进行了分析。最后探讨了无线视频传输容错算法的发展趋势和挑战,提出了几个值得重视的发展方向。 相似文献
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In this paper, we propose acombined variable-rate code-excited linearly predictive (QCELP)speech coding and unequal error protection (UEP) channel codingsystem for wireless communications. In contrast to theconventional schemes, our system employs a concatenatedsuper-imposed rate-compatible punctured convolutional (SI-RCPC)channel coding scheme which can provide UEP with respect to notonly the bit-significance of speech packets but also the speechactivity and local channel characteristics. Verified by thesimulation results, the combined system achieves an averagetransmission rate less than 8 kb/s as well as an average 2 dBsignal-to-noise ratio (SNR) gain over the conventional equal errorprotection system. 相似文献
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Bon-Jin Ku Jong-Moon Chung Changeon Kang 《AEUE-International Journal of Electronics and Communications》2004,58(6):420-423
In this letter, we investigate serial and hybrid concatenated space-time (SC-ST and HC-ST) codes applying iterative decoding topologies. The coding operations are based on the concatenation of convolutional coding, interleaving, and space-time coding along with a multiple-transmitter/multiple-receiver diversity system. Through the analysis of the SC-ST and HC-ST coding systems, improved design specifications can be selected for the component encoders with considerations of the wireless channel characteristics. Based on the iterative decoding process and the optimum parameter selection operations, a considerable improvement in the error rate performance is obtained. For the applied specs, the results indicate that at the frame error rate (FER) 10−2 level the SC-ST coding system provides a coding gain of approximately 3 dB in comparison to the Tarokh, Seshadri, Calderbank (TSC) space-time (ST) code [1], where the HC-ST coding system provides an additional coding gain of approximately 1 dB beyond the SC-ST code. 相似文献
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《Signal Processing: Image Communication》2004,19(4):369-385
Transporting hybrid coded video over wireless channel is very challenging. On the one hand, wireless link is much more error prone than wired network due to time varying channel conditions such as fading and multipath interference. On the other hand, hybrid coded video is very vulnerable to error propagation when transmitted over error prone channels. Numerous researches have been conducted to enhance error robustness for wireless video transmission. Among them, many schemes use retransmission to reduce packet loss rate and improve reconstructed video quality. However, retransmission is delay constrained due to the low delay nature of real-time video. Packet loss is inevitable even when retransmission is employed. In the proposed architecture, a novel error recovery scheme is introduced which switches adaptively between ACK and NACK modes according to channel conditions. Video proxy server at the base station is designed to make the retransmission and feedback based error recovery method more effective. State-of-the-art H.264 is used as video encoder since it provides not only high coding efficiency but also multi-frame which plays a key role in the framework. Simulation results demonstrate the effectiveness of this architecture. 相似文献
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提出了采用低密度奇偶校验码的分布式联合信源信道网络编码方案,应用于两源一中继一目的节点的无线传感器网络中.在方案中,信源节点通过传输系统信道码的校验位与部分信息位,同时实现了信源压缩与信道纠错.中继节点有效利用数据的相关性进行译码,并进行部分数据比特删余,减少因中继端网络编码引起的错误传播,仿真验证了方案的有效性.应用了不等差错保护思想,更贴近实际应用场景,利于目的节点进行更好的低误差解码. 相似文献