训练序列长度可变的混合ARQ方案

为了进一步提高系统的吞吐效率,本文提出了一种均衡器训练序列长度可变的混合ARQ方案.通过对该方案和现有方案吞吐效率的理论推导和计算复杂度分析得出:该方案可以在不增加计算复杂度的情况下,提高系统吞吐效率.数值仿真的结果进一步证实了该方案的有效性.     

移动通信中基于Turbo码的混合ARQ方案

在移动环境中，由于信道的时变特性，单纯的FEC或ARQ机制往往无法提供所希望的系统性能。为了提高数据及图像的传输可靠性，需采用ARQ与FEC相结合的混合ARQ差错控制方案。首先介绍了几种常见的以Turbo码作为纠错码的混合ARQ方案，然后研究了基于Turbo码组合译码的有限次重传混合ARQ方案，给出了传输方案及组合译码算法。仿真结果表明，低Eb/No时，该方案对通过率有明显改善。     

一种自适应混合ARQ体制

本文提出了一种采用乘积码的混合ARQ体制。与混合Ⅱ型方案相比,该体制在对信道的自适应能力、码长的选择、译码速度方面具有更大的灵活性。在很宽的信道变化范围内,该体制的通过率高于混合Ⅱ型。     

基于G.hn标准协议的PLC混合ARQ方案研究与改进

现代电力线通信(PLC)系统为了可靠地传输数据并提高系统传输量,自动重传请求(ARQ)技术必不可少.然而ARQ技术已经很好地解决了现有通信的数据传输问题,但由于PLC信道不稳定、强干扰以及衰减非常快等缺点造成误码率极高、吞吐量低.针对PLC家庭网络提出能够适应PLC信道的H-ARQ技术来满足未来PLC通信网络的需求.改进ARQ和低密度奇偶校验(LDPC)技术相结合来提高传输率、降低误码率.最后通过仿真实验对改进的H-ARQ协议算法验证,从仿真结果可以看出误码率降低、吞吐量较高,能适应环境极其差的电力线通信.     

无线数据传输中的混合ARQ

本文针对无线数据传输中的混合ARQ,介绍了混合ARQ的基本概念和技术,重点分析评述了用于混合ARQ系统中的各种包合并方案和相关的纠错编码技术,并对混合ARQ的相关研究工作进行了展望.     

M步混合ARQ系统时延性能分析

为保证数据传输的可靠性,多种ARQ（自动请求重传）协议被提出和采用。论文针对多种ARQ／混合ARQ协议提出了一个一般化、系统化的时延分析模型,并采用信号流图理论及梅逊公式给出了M步混合ARQ控制系统的时延性能分析结果,为多种ARQ／混合ARQ协议的时延性能分析提供了一种系统化的有效分析方法。     

混合ARQ无线传输系统在多机牵引中的应用

为了保障多机牵引无线同步控制系统数据传输的可靠性,提出一种多机牵引无线同步控制系统的混合ARQ数据传输子系统设计方案,并讨论了其在机车信号传输中存在的问题。     

An Adaptive Hybrid ARQ Scheme

A hybrid ARQ in which the transmitter adaptively selects an FEC code according to the channel condition is presented and analyzed. The code is selected according to the past transmissions and acknowledgements by an algorithm which is a generalization of that in [1]. The throughput is obtained as a function of the frame error rate for a general system employing the adaptive hybrid ARQ with acknowledgements that arrive instantly on an error-free return channel. The throughput is obtained as a function of the signal-to-noise ratio for an example quad rate system employing convolutional codes with non-coherent frequency shift keying over the uncorrelated Rayleigh fading channel. This allows the best choice for the parameters of the algorithm to be made. In the case that the channel bit errors are independent, the generalization offers performance improvement of less than 10% over that in [1]. But when the channel errors are bursty, as in the case of Rayleigh fading with finite bit interleaving, the generalization offers throughput improvement as high as 24%. We go on to consider incorporating code combining with the adaptive scheme to form an adaptive memory hybrid ARQ. Simulation of a system using complementary punctured convolutional codes with 4 code rates shows that 2-level code combining can extend the adaptive scheme's useful throughput into the low SNR region by approximately 4 dB.     

ARQ strategies for relay cooperative systems

We propose two novel automatic repeat request (ARQ) strategies for relay cooperative systems over Rayleigh fading channel one uses relay ARQ and the other destination ARQ. The BER performance of these two strategies is derived in fast block fading. Numerical analysis and simulation show the systems can get more performance gain when the inter-channel (the source to the relay) quality is bad in the relay ARQ strategy. In the destination ARQ strategy, when the uplink qualities of the source and relay to the destination are poor, the average received SNR of the destination is much low, the systems performance can be improved efficiently.     

基于非均匀星座的改进ARQ方案及其性能分析

本文针对调制阶数大于4的MPSK和MQAM调制，在重传中采用非均匀星座图和符号比特重新排序，提出了一种改进的ARQ方案。通过对AWGN信道下ARQ方案进行理论分析和数值仿真，表明基于非均匀星座的新方案在信道条件较差时能有效地提高重要比特的可靠性，若重传中结合符号比特重排和分组合并，则可使接收端解调合并后的比特可靠性趋于均匀且总体得到提高，从而有效地减少重传次数，提高系统的吞吐率。由于本文所提方案并不改变调制解调规则和数据分组长度，故容易实现和控制。     

A Low-Overhead Energy-Efficient ARQ Protocol for Wireless Sensor Networks

Wireless sensor network （WSN） is a typical kind of low-power and lossy network, in where ARQ （Automatic Repeat reQuest） schemes are often used to improve packets reliability. However, the ARQ related packets may incur significant load and consume more energy. This paper proposes a novel energy efficient ARQ protocol called ARQ＋, which uses the nearest-first scheme and NAK aggregation scheme to reduce the amount and transmission hops of the ARQ related packets. Consequently, the energy consumption is significantly decreased. Theoretical analyses of ARQ＋ on energy consumption, packet arrive ratio and latency are provided. Performance improvement of ARQ＋ is validated by extensive simulations. They both show that ARQ＋ has satisfactory energy efficiency, good packets arriving ratio and reasonable average packet delay comparing to traditional ARQ schemes.     

HARQ–ARQ interaction method for LTE‐based mobile satellite communication system

Hybrid automatic repeat request (HARQ) and automatic repeat request (ARQ) of the terrestrial long‐term evolution (LTE) system are designed considering the very short propagation delay of terrestrial environment. Therefore, when HARQ and ARQ are applied to the LTE‐based mobile satellite communication system, the inefficiency is caused by the long propagation delay of satellite environment. This paper proposes the interaction method between HARQ and ARQ for the decrease of inefficiency in the LTE‐based mobile satellite communication system. The existing concept of layered architecture about HARQ and ARQ is also maintained in our interaction method. Simulation results reveal that our proposed scheme can provide the larger spectrum efficiency than that of the non‐interaction scheme in all environments. The performance improvement can be up to 2.04 times through the interaction method. Copyright © 2014 John Wiley & Sons, Ltd.     

LTE中ARQ的机制研究及算法改进*

本文主要研究了LTE中的ARQ机制,并针对ARQ确认算法中每次组装状态报告只是固定添加未接收到的PDU的SN号或分段信息而可能导致资源浪费的问题,提出了一种自适应确认算法,通过设定不同的基准参数,采用不同的偏移算法,有效的提高了系统的确认效率和资源利用率,从而使系统获得了较高的吞吐量。     

一种用于OFDM系统的频率分集ARQ方案

研究了一种适合高数据速率的正交频分复用OFDM传输的频率分集ARQ方案.通过采用等增益合并和子载波分配等技术,该方案可利用频率分集来有效减少慢衰落信道中的重传次数.计算机仿真显示在累计正确分组接收率为0.99时此方案的重传次数为3次,而普通的方案要10次以上.     

On stochastic learning in predictive wireless ARQ

Traditional automatic repeat request (ARQ) protocols are channel unaware. That is, they react to channel errors by simply retransmitting erroneous packets and do not proactively decide whether or not to transmit a packet in a given slot based on past channel conditions. Clearly, ARQ protocols operating in this mode are not energy efficient. For example, continuously retransmitting erroneous packets when the wireless channel is in deep fade would cause significant wastage of transmission energy. In this paper, we present a stochastic learning automaton‐based wireless channel state aware ARQ protocol. The learning automaton learns to predict and track the time‐varying wireless channel conditions based on past observations. A Markov chain model for the channel state transitions is used. No a priori knowledge about the state transition probabilities is required by this predictor. Stochastic convergence of the learning algorithm is proved. The proposed ARQ protocol utilizes the predictions to compute transmission/retransmission policies in an online fashion. No pilot (training) symbols are used by the protocol for channel state prediction thereby avoiding any energy wastage due to the transmission of these symbols. Simulation results show that depending on the channel memory significant energy savings can be attained when compared with standard ARQ protocols. We also discuss the transmission energy versus delay trade‐off. Copyright © 2007 John Wiley & Sons, Ltd.     

卫星数据通信中ARQ和FEC的优化组合研究

本文从分析ＦＥＣ编码码率对吞吐量的影响着手，指出为达到较高的信道吞吐量，不是采用越强的纠错编码能力越好的观点；之后，又提出了一种新的第２类混合差错控制方式，分析了其吞吐量性能，结果证明，此方式能以有限大的存储容量和实现复杂度达到比现有方式更高的吞吐量。