Adaptive type II hybrid ARQ scheme using zigzag code

The authors propose a new hybrid type II ARQ scheme based on the simple multidimensional concatenated zigzag code. Owing to the fact that the error-correcting capability of zigzag codes is far better than that of conventional convolutional codes, the throughput of our scheme is better than existing hybrid ARQ schemes     

Generalized type II hybrid ARQ scheme using punctured convolutionalcoding

A method is presented to construct rate-compatible convolutional (RCC) codes from known high-rate punctured convolutional codes, obtained from best-rate 1/2 codes. The construction method is rather simple and straightforward, and still yields good codes. Moreover, low-rate codes can be obtained without any limit on the lowest achievable code rate. Based on the RCC codes, a generalized type-II hybrid ARQ scheme, which combines the benefits of the modified type-II hybrid ARQ strategy of J. Hagenauer (1988) with the code-combining ARQ strategy of D. Chase (1985), is proposed and analyzed. With the proposed generalized type-II hybrid ARQ strategy, the throughput increases as the starting coding rage increases, and as the channel degrades, it tends to merge with the throughput of rate 1/2 type-II hybrid ARQ schemes with code combining, thus allowing the system to be flexible and adaptive to channel conditions, even under wide noise variations and severe degradations     

Efficient stop-and-wait type II hybrid ARQ scheme

An efficient stop-and-wait ARQ protocol proposed by Sastry (1975) is modified to include a parity retransmission type II hybrid ARQ scheme. Unlike the Sastry scheme in which simple repeats of a data packet are transmitted, with the type II hybrid ARQ scheme, the data packet to be transmitted is encoded with a rate 1/2 code, and repetitions alternate between the two sequences obtained at the output of the encoder. It is found that the throughput can be substantially increased.<>     

A novel hybrid ARQ scheme using turbo codes and diversity combining

A novel HARQ scheme using turbo codes is proposed. The method jointly utilizes diversity combining, partial retransmission, and power scaling. Computer simulations and density evolution analysis show that the new method outperforms equal gain diversity combining and soft information combining techniques for a wide E_b/N₀$E_b/N_0$ range.     

A multicast hybrid ARQ scheme using MDS codes and GMD decoding

An efficient multicast hybrid ARQ scheme is proposed by incorporating the generalized minimum distance (GRID) decoding of maximum distance separable (MDS) codes with Metzner's (1984) scheme. Erroneous frames are stored in the receiver buffer and recovered after receiving one or more redundant frames. The throughput and the average transmission delay of the proposed scheme are analyzed on memoryless symmetric channels. The proposed scheme can circumvent the degradation of the throughput due to an increase of the number of receivers, which is the most serious defect in the conventional multicast ARQ schemes, at the expense of the transmission delay     

Separate codes on type-II hybrid ARQ systems

A hybrid automatic repeat request (ARQ) system (HARQ-II) with parity retransmission for error correction, which combines ARQ and forward error correction is discussed, and the successful application of these codes to HARG-II is illustrated. A method of constructing the codes whereby conventional BCH codes can be changed into separable codes is proposed. A scheme is presented that has the advantages that, the code lengths are always made equal and that even in parity retransmission new information symbols can be sent along with the necessary parity-check symbols. The performance of the proposed schemes on the binary symmetric channel is discussed. The numerical results show that they outperform conventional schemes     

Improved selective repeat ARQ scheme for mobile multimediacommunications

This paper suggests a NAK-based selective repeat (SR) scheme for reliable data transmission in the future land-mobile communications systems supporting multimedia services. The proposed scheme is an improved version of the automatic repeat request defined in IS-707. We analyze the proposed SR under the assumption of a two-states Markov channel. The numerical results show that drastic performance improvement can be achieved at the cost of minor increase in complexity     

New ARQ protocols using concatenated codes

Two automatic-repeat-request (ARQ) protocols using a concatenated coding scheme are described. The structure, introduced in a codeword of a concatenated coding scheme, is used to improve the performance of ARQ protocols, especially for high error rates in the communication channel. The performance of the scheme described herein is derived through theoretical analysis. The results show that the proposed scheme outperform other similar ARQ protocols     

End-to-end delay of an adaptive selective repeat ARQ protocol

This paper analyzes the end-to-end delay of a selective-repeat ARQ protocol which tries to adaptively use the channel idle time. The end-to-end delay consists of three parts: queueing delay at the transmitter, transmission delay over the channel, and resequencing delay at the receiver. Although this paper succeeds only in obtaining approximate end-to-end delay, the agreement with simulation is generally good     

基于RCPT编码的自适应选择合并混合ARQ算法

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。     

Design of rate-compatible structured LDPC codes for hybrid ARQ applications

In this paper, families of rate-compatible protograph-based LDPC codes that are suitable for incrementalredundancy hybrid ARQ applications are constructed. A systematic technique to construct low-rate base codes from a higher rate code is presented. The base codes are designed to be robust against erasures while having a good performance on error channels. A progressive node puncturing algorithm is devised to construct a family of higher rate codes from the base code. The performance of this puncturing algorithm is compared to other puncturing schemes. Using the techniques in this paper, one can construct a rate-compatible family of codes with rates ranging from 0.1 to 0.9 that are within 1 dB from the channel capacity and have good error floors.     

Incremental redundancy hybrid ARQ schemes based on low-density parity-check codes

We study the throughput of hybrid automatic retransmission request (H-ARQ) schemes based on incremental redundancy (IR) over a block-fading channel. We provide an information-theoretic analysis assuming binary random coding and typical-set decoding. Then, we study the performance of low-density parity-check (LDPC) code ensembles with iterative belief-propagation decoding, and show that, under the hypothesis of infinite-length codes, LDPCs yield almost optimal performance. Unfortunately, standard finite-length LDPC ensembles incur a considerable performance loss with respect to their infinite-length counterpart, because of their poor frame-error rate (FER) performance. In order to recover part of this loss, we propose two simple yet effective methods: using a modified LDPC ensemble designed to improve the FER; and using an outer selective-repeat protocol acting on smaller packets of information bits. Surprisingly, these apparently very different methods yield almost the same performance gain and recover a considerable fraction of the optimal throughput, thus making practical finite-length LDPC codes very attractive for data wireless communications based on IR H-ARQ schemes.     

基于II型H-ARQ系统速率可变低密度校验码的设计与研究

构造了一类用于II型H-ARQ系统、具有Z字形结构校验矩阵、性能优良的速率可变低密度校验码(RC-LDPC)。将渐进边增长(progressiveedgegrowth)算法推广应用到RC-LDPC码的构造中,扩大了码率动态变化范围,提高了码的性能。仿真结果表明将此类RC-LDPC码应用于II型H-ARQ系统,可获得较高的吞吐量,且其校验矩阵的Z字形结构极大地降低了系统实现的复杂度。     

Analysis of a type II hybrid ARQ strategy in a DS-CDMA packet transmission environment

A type II hybrid automatic repeat request scheme is considered as a retransmission strategy in a direct-sequence code-division multiple-access packet mobile radio network. An analysis based on equilibrium point analysis is presented to model the behavior of the system in a message-based traffic generation model. A simulation approach is introduced to validate the proposed analytical model, obtaining results that closely match those derived theoretically.     

基于II型H-ARQ系统速率可变低密度校验码的设计与研究

构造了一类用于Ⅱ型H-ARQ系统、具有Z字形结构校验矩阵、性能优良的速率可变低密度校验码（RC-LDPC）。将渐进边增长（progressive edge growth）算法推广应用到RC-LDPC码的构造中，扩大了码率动态变化范围，提高了码的性能。仿真结果表明将此类RC-LDPC码应用于Ⅱ型H-ARQ系统，可获得较高的吞吐量，且其校验矩阵的Z字形结构极大地降低了系统实现的复杂度。     

On the performance of hybrid FEC/ARQ systems using rate compatiblepunctured turbo (RCPT) codes

This paper introduces a hybrid forward-error correction/automatic repeat-request (ARQ) system that employs rate compatible punctured turbo (RCPT) codes to achieve enhanced throughput performance over a nonstationary Gaussian channel. The proposed RCPT-ARQ system combines the performance of turbo codes with the frugal use of incremental redundancy inherent in the rate compatible punctured convolutional codes of Hagenauer (1988). Moreover, this paper introduces the notion of puncturing the systematic code symbols of a turbo code to maximize throughput at signal-to-noise ratios (SNRs) of interest. The resulting system provides both an efficient family of achievable code rates at middle to high SNR and powerful low-rate error correction capability at low SNR     

A hybrid ARQ protocol using integrated channel equalization

In this letter, a new hybrid automatic repeat request (ARQ) approach is presented to enhance receiver performance for communication systems employing forward error-correction codes in frequency-selective fading environments. This new approach involves a simple modification to the traditional turbo equalizer by combining multiple ARQ transmissions via integrated channel equalization. This modification leads to better computational efficiency, better exploitation of channel diversity, better channel-estimation ability, and improved performance (frame-error rates) when concatenated with an outer code. These improvements are verified through evaluations of extrinsic information transfer charts and ARQ simulations when compared with iterative combining of multiple transmissions.     

Performance evaluation of the generalized type-II hybrid ARQ schemewith noisy feedback on Markov channels

The generalized type-II hybrid automatic repeat request (ARQ) scheme on Markov channels is examined in order to study the effect of feedback channel errors on the performance of ARQ systems. It is shown that it is possible to derive expressions for certain critical performance parameters, such as the throughput efficiency, the probabilities of packet loss, undetected error, and correct delivery. To provide a means of comparison, a parallel set of expressions is provided under the usual assumption of an error-free feedback channel. By use of simulations, the ARQ system performance is examined under noiseless feedback and noisy feedback. It is found that feedback channel noise can result in the loss of packets, an increase in the number of undetected errors, and the occurrence of unnecessary transmissions. To enhance the performance of the GH-II ARQ scheme, a predictor is used and found to lower the probability of undetected error, reduce the number of unnecessary transmissions, and increase the throughput efficiency     

An adaptive error control system using hybrid ARQ schemes

A simple and efficient system utilizing the class of Hamming codes in a cascaded manner is proposed to provide high throughput over a wide range of channel bit error probability. Comparisons with other adaptive schemes indicate that the proposed system is superior from the point of view of throughput, while still providing the same order of reliability as an ARQ (automatic repeat request) system. The main feature of this system is that the receiver uses the same decoder for decoding the received information after each transmission while the error-correcting capability of the code increases. As a result, the system is kept to the minimum complexity and the system performance is improved     

Performance of truncated type-II hybrid ARQ schemes with noisyfeedback over block fading channels

This paper considers truncated type-II hybrid automatic repeat-request (ARQ) schemes with noisy feedback over block fading channels. With these ARQ techniques, the number of retransmissions is limited, and, similar to forward error correction (FEC), error-free delivery of data packets cannot be guaranteed. Bounds on the average number of transmissions, the average coding rate as well as the reliability of the schemes are derived using random coding techniques, and the performance is compared with FEC. The random coding bounds reveal the achievable performance with block codes and maximum-likelihood soft-decision decoding. Union upper bounds and simulation results show that over block fading channels, these bounds can be closely approached with simple terminated convolutional codes and soft-decision Viterbi decoding. Truncated type-II hybrid ARQ and the corresponding FEC schemes have the same probability of packet erasure; however, the truncated ARQ schemes offer a trade-off between the average coding rate and the probability of undetected error. Truncated ARQ schemes have significantly higher average coding rates than FEC at high and medium signal-to-noise ratio even with noisy feedback. Truncated ARQ can be viewed as adaptive FEC that adapts to the instantaneous channel conditions