共查询到20条相似文献,搜索用时 0 毫秒
1.
2.
3.
Topology-transparent scheduling for mobile wireless ad hoc networks has been treated as a theoretical curiosity. This paper makes two contributions towards its practical deployment: (1) We generalize the combinatorial requirement on the schedules and show that the solution is a cover-free family. As a result, a much wider number and variety of constructions for schedules exist to match network conditions. (2) In simulation, we closely match the theoretical bound on expected throughput. The bound was derived assuming acknowledgments are available immediately. We use rate less forward error correction (RFEC) as an acknowledgment scheme with minimal computational overhead. Since the wireless medium is inherently unreliable, RFEC also offers some measure of automatic adaptation to channel load. These contributions renew interest in topology-transparent scheduling when delay is a principal objective. 相似文献
4.
数字通信系统通常采用前向纠错编码提高系统可靠性,传统干扰方法针对采用前向纠错编码通信系统的干扰效果较差,为了克服此缺点,提出了通过控制错误分布的脉冲干扰方法。分析了典型卷积码和RS码的纠错能力,根据2种纠错编码的特性分别探讨了干扰信号设计原则和方法。计算机仿真表明,针对不同的编码样式采用特定脉冲干扰参数,能够取得更好的干扰效果。 相似文献
5.
This paper examines the use of BCH error-correcting codes in improving the performance of a stop-and-wait automatic repeat-request (ARQ) scheme over random error and Rayleigh fading channels. Two models are analyzed. The first model considers the effect of forward error correction on the mean wasted time per message. The second model assumes a Poisson arrival process for the messages and examines the effect of forward error correction on the mean time between the arrival of a message and its successful transmission. In both models, our results indicate that the performance of the ARQ scheme can be substantially improved by the use of forward error correction. 相似文献
6.
7.
前向纠错技术及其在现代通信系统中的应用 总被引:3,自引:0,他引:3
对在数字通信系统中广泛使用的前向纠错(FEC)技术进行了较为详细的介绍,重点描述了不同的编码方法,分析了各种信道编码技术及其对系统性能的影响。 相似文献
8.
9.
Forward Error Correction Coding for Fading Compensation in Mobile Satellite Channels 总被引:2,自引:0,他引:2
Fading in mobile satellite communications severely degrades the performance of data transmission. The channel is modeled with nonfrequency selective Rice and Rayleigh fading. Also, stored channel simulation is used for hardware data transmission. FEC coding with Viterbi decoding of convolutional codes, and Berlekamp-Massey decoding of Reed-Solomon codes, are used to compensate for the fading. In addition to interleaving, channel state and erasure information improve the performance of the decoder. The BER after decoding is calculated for specific codes on several channels and for different transmission schemes. Using very simple channel state and erasure information gives 2-7 dB additional coding gain. These gains have been verified by hardware data transmission on synthetic fading channels and stored mobile satellite channels. 相似文献
10.
11.
The multipath fading channel modeling traditionally focuses on physical level dynamics such as signal strength and bit error
rate. In this paper we characterize multipath fading channel dynamics at the packet level and analyze the corresponding data
queueing performance in various environments. The integration of wireless channel modeling and data queueing analysis provides
us a unique way to capture important channel statistics with respect to various wireless network factors such as channel bandwidth,
mobile speed and channel coding. The second order channel statistics, i.e. channel power spectrum, is found to play an important
role in the modeling of multipath fading channels. The data queueing performance is largely dependent on the interaction between
the channel power spectrum and the data arrival power spectrum; whichever has lower frequency power will have more impact
on queueing performance. Note that the data arrival power spectrum provides a measure of burstiness and correlation behavior
of data packet arrivals. Throughout the paper, we use the Markov chain modeling technique to match the measured important
channel statistics for both channel modeling and queueing analysis.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
12.
Ming-Fong Tsai Naveen Chilamkurti Ce-Kuen Shieh 《Wireless Personal Communications》2011,56(3):435-446
Video streaming over wireless networks is a challenging task due to its high error rate. Forward error correction (FEC) is
a popular mechanism to recover lost packets for video streaming. Conventional FEC mechanisms use a whole redundant packet
to recover the error source packet, when the packet error occurs with only a few bit errors inside. In this paper, we propose
an Adaptive packet and block length FEC (APB-FEC) control mechanism. In order to overcome the high bit error rate, a small
packet length reduces the packet error rate and a large FEC block length will enhance the recovery performance. Our proposed
APB-FEC can obtain better recovery performance than conventional FEC mechanisms. Hence, APB-FEC can also reduce retransmission
overhead. Using extensive emulations, we validate the efficiency of APB-FEC mechanism for video streaming over wireless networks. 相似文献
13.
14.
The aim of this paper is to use a software defined radio (SDR) based approach in order to select channel encoding and decoding method accordingly using 8-QAM (Quadrature Amplitude Modulation) in terms of bit error rate (BER). By selecting a higher order format of QAM, we are able to carry more bits of information per symbol; also the data rate can be increased thus achieving greater distance between adjacent points in the I–Q plane by distributing the points more evenly. Hence the constellation points are more distinct and data errors are reduced. In the present work 8-QAM is chosen as modulation scheme so that balance can be maintained between higher data rates while maintaining an acceptable bit error rate for SDR. Channel coding schemes forward error correction are used where the re-transmission of the data is not feasible, thus redundant bits are added along with the message bits and transmitted through the channel. On the receiver side, this channel coded signal is decoded in order to get back the original data even if the channel coded signal undergoes some interference from the noise in the transmission medium. The performance is then analyzed in terms of BER for Hamming and convolution coding algorithms at a particular value of SNR in LabVIEW graphical programming. With the help of LabVIEW we were able to design the systems in a block-based manner in shorter time as compared to the commonly used text-based programming languages. 相似文献
15.
与传统存储方式相比,脱氧核糖核酸(DNA)存储的难点是测序序列中的插入和删除错误给信息解码过程带来了巨大挑战。针对具有1位纠错能力的前向纠错编码DNA存储,该文提出一种桶式分配策略提高解码的精度和效率。首先,搜索每个分组中所有测序读长的可识别DNA码,根据1位纠错能力确定其对应的合法编码;其次,根据每个可识别DNA码在测序读长的位置确定相应编码的最佳编码位置(即桶);最后,按照众数投票确定每个桶中的最终编码。仿真结果表明在0.10和0.05错误率条件下,平均解码准确率在20X测序深度时可达94%以上;在0.15错误率条件下,平均解码准确率在60X测序深度时可达90%以上。 相似文献
16.
量子位叠加态的防错纠错编码 总被引:10,自引:2,他引:8
提出用单个量子位的叠加态进行量子编码,采用分组纠错方法,设置纠错量子线路;用8个量子们编码时,建立同态量子位对模型,简化了量子编码。 相似文献
17.
Error correction codes (ECCs) are commonly used to deal with soft errors in memory applications. Typically, Single Error Correction-Double Error Detection (SEC-DED) codes are widely used due to their simplicity. However, the phenomenon of more than one error in the memory cells has become more serious in advanced technologies. Single Error Correction-Double Adjacent Error Correction (SEC-DAEC) codes are a good choice to protect memories against double adjacent errors that are a major multiple error pattern. An important consideration is that the ECC encoder and decoder circuits can also be affected by soft errors, which will corrupt the memory data. In this paper, a method to design fault tolerant encoders for SEC-DAEC codes is proposed. It is based on the fact that soft errors in the encoder have a similar effect to soft errors in a memory word and achieved by using logic sharing blocks for every two adjacent parity bits. In the proposed scheme, one soft error in the encoder can cause at most two errors on adjacent parity bits, thus the correctness of memory data can be ensured because those errors are correctable by the SEC-DAEC code. The proposed scheme has been implemented and the results show that it requires less circuit area and power than the encoders protected by the existing methods. 相似文献
18.
Performance predictions for troposcatter channels with multipath are developed using the eigenvalues in the Karhunen-Loeve representation of the tropo signal. Flat Rayleigh fading predictions, in the presence of jamming, are easily extended to multipath channels with this technique 相似文献
19.
20.
网络编码对网络中的传输错误或恶意攻击十分敏感,如果网络拓扑和网络码对于网络的收点和发点都是已知的,这种类型的网络称为Coherent网络。在Coherent网络中,网络汉明重量的概念拉近了网络纠错码和传统纠错码之间的距离,传统纠错码的一些理论和方法有望在将来应用于网络纠错码。类似于传统纠错码,极小距离反映了网络纠错码的纠错能力。利用陪集码理论去描述和研究网络纠错码是一个令人感兴趣的研究方向。 相似文献