Analysis of memory and incremental redundancy ARQ schemes over anonstationary channel

A generalized type II automatic-repeat-request (ARQ) scheme using punctured convolutional coding on a two-state Markov model of a nonstationary channel is analyzed. A simple ARQ scheme with memory is also analyzed. It is shown that the simple memory ARQ scheme offers a substantial throughput improvement over a conventional ARQ scheme at severe channel conditions. Furthermore, the generalized type II ARQ scheme yields a better performance than the conventional type II ARQ scheme under all channel conditions, thus making it attractive for use over time-varying channels     

An ARQ scheme using combined QPSK and BPSK transmissions

We propose a hybrid ARQ scheme which uses QPSK modulation for the first transmission and BPSK modulation for retransmissions. The throughput performance of the proposed ARQ scheme is better that those of ARQ schemes purely using QPSK modulation or purely using BPSK modulation for transmissions. Furthermore, the proposed scheme does not require any operation of error correction as usually required in hybrid ARQ schemes. Therefore, the ARQ scheme proposed in this paper can be easily implemented     

Sequential decoding with an efficient incremental redundancy ARQscheme

Sequential decoding is analyzed in conjunction with an efficient incremental redundancy automatic repeat request (ARQ) scheme using punctured convolutional coding. With the incremental redundancy ARQ scheme, whenever the decoding time of a given data packet exceeds some predetermined value T_max, decoding of that data packet is stopped and incremental redundancy bits are provided by the transmitter, a few bits at a time, as needed. It is shown that the incremental redundancy ARQ scheme provides throughput improvement over the partial retransmission code combining ARQ scheme. The advantage of the incremental redundancy ARQ scheme is that the throughput increases as the starting coding rate increases over all ranges of signal-to-noise ratios     

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     

Performance of combined ARQ with SR and GBN for broadband wirelesssystems on a 40 GHz band radio channel

Mobile wireless communication systems for the fourth generation are being explored. The key is broadband and high-quality communications to support multimedia services, and the use of millimeter or centimeter-wave band and ARQ is being considered to realize such communications. In this article we propose a new ARQ scheme which is combined with SR and GBN, and confirm that this new scheme is proper for broadband communication systems. We implemented our ARQ function with hardware and evaluated the ARQ performance: throughput, cell loss rate, and cell transfer delay on a pseudo Rayleigh fading channel. In addition, we evaluated ARQ performance on an actual 40 GHz band radio channel. Through the evaluation, we found it necessary to design an ARQ scheme in accordance with system requirements, and our combined ARQ satisfies this required condition     

A novel adaptive hybrid ARQ scheme for wireless ATM networks

This paper describes the design and performance of a novel adaptive hybrid ARQ scheme using concatenated FEC codes for error control over wireless ATM networks. The wireless links are characterized by higher, time‐varying error rates and burstier error patterns in comparison with the fiber‐based links for which ATM was designed. The purpose of the hybrid ARQ scheme is to provide a capability to dynamically support reliable ATM‐based transport over wireless channels by using a combination of our ARQ scheme (called SDLP) and the concatenated FEC scheme. The key ideas in the proposed hybrid ARQ scheme are to adapt the code rate to the channel conditions using incremental redundancy and to increase the starting code rate as much as possible with the concatenated FEC, maximizing the throughput efficiency. The numerical results show that our proposed scheme outperforms other ARQ schemes for all SNR values. This revised version was published online in July 2006 with corrections to the Cover Date.     

A MAC/PHY cross-layer design for efficient ARQ protocols

In many wireless data systems, automatic repeat request (ARQ) and hybrid automatic repeat request (HARQ) work independently. In this paper, we introduce a new ARQ feedback scheme called Cross-Layer ARQ (CL-ARQ), where ARQ closely interoperates with HARQ by making use of the acknowledgement of HARQ internally. By doing so, CL-ARQ not only removes the overhead for ARQ acknowledgement messages, but also improves the average delivery delay and TCP throughput. Especially, when the entities in charge of HARQ and ARQ are located far apart geographically, CL-ARQ remarkably outperforms the legacy scheme.     

A Modified Selective-Repeat Type-II Hybrid ARQ System and Its Performance Analysis

The hybrid ARQ scheme with parity retransmission for error control, recently proposed by Lin and Yu [1], [2], is quite robust. This scheme provides both high system throughput and high system reliability. In this paper, a modified Lin-Yu hybrid ARQ scheme is presented. The modified scheme provides a slightly better throughput performance than the original Lin-Yu scheme; however, it is more flexible in utilizing the error-correction power of a code. The modified scheme can be incorporated with a rate 1/2 convolutional code using Viterbi decoding. Furthermore, the pure selectiverepeat ARQ is a degenerated case of the modified scheme in selective mode. Lin and Yu analyzed their scheme only for a receiver buffer of sizeNwhereNis the number of data blocks that can be transmitted in a round-trip delay interval. No analysis for other buffer sizes was given. In this paper, the throughput performance of the modified Lin-Yu scheme is analyzed for any size of receiver buffer. Consequently, the throughput efficiency of the pure selective-repeat ARQ for any receiver buffer size can be obtained. We also show that the modified scheme achieves the same order of reliability as a pure ARQ scheme.     

Reliability-based hybrid ARQ

A new hybrid automatic repeat request (ARQ) scheme that utilises reliability estimates generated by soft-input, soft-output (SISO) decoders is proposed. The proposed ARQ scheme transmits, additional information for the unreliable bits, and this information is used to perform additional decoding. Results are presented that show this ARQ technique can provide performance close to the channel capacity     

A New ARQ Scheme for Reliable Broadcasting in Wireless LANs

This paper proposes a new automatic repeat request (ARQ) scheme for reliable broadcasting in distributed wireless LANs. Unlike traditional ARQ schemes for reliable broadcasting, the proposed scheme is highly efficient in its ARQ control information delivery and only introduces light control overhead in the network. Our simulation results show that as compared with traditional ARQ schemes, the proposed scheme improves the LAN throughput by from several tens to more than one hundred percent, depending on the number of nodes in the LAN.     

On ARQ scheme with adaptive error control

Adaptive automatic repeat request (ARQ) schemes are quite effective for throughput enhancement in time-varying mobile channel environments. An ARQ scheme with adaptive error-correcting codes is considered. A robust channel sensing algorithm by making use of XOR-ing is proposed for link adaptation. With the proposed channel estimation algorithm, an adaptive scheme that adapts its error-correcting codes according to channel conditions is presented. The efficiency of the proposed adaptive ARQ scheme is evaluated in terms of throughput performance by computer simulation for a time-varying mobile channel characterized by Rayleigh fading and log-normal shadowing. As an enhancement in counteracting long deep fades, the incorporation of frequency diversity into an adaptive ARQ scheme is also investigated and the simulation results show that this scheme is quite efficient in counteracting long deep fades     

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。     

The performance analysis of a concatenated ARQ scheme using parityretransmissions

The authors analyze an ARQ (automatic repeat request) scheme using parity retransmissions. By dividing each transmission block into subblocks, the combination of a transmission block and its retransmission block has the structure of a concatenated code. They derive formulae for calculating an upper bound on the probability of undetected errors and a lower bound on the throughput for such an ARQ scheme. Numerical results show that even with extremely simple code design, such an ARQ scheme has satisfactory performance     

Performance analysis of a time diversity ARQ in land mobile radio

A time diversity automatic repeat-request (ARQ) scheme with a finite number of transmissions is investigated for a digital FM mobile radio with frequency demodulation (FD). It processes all the retransmissions of a single data block using postdetection diversity combining. The analysis of the signal energy per bit required for a given bit error rate (BER) and the spectral efficiency in a cellular mobile radio system are presented. The results obtained from the numerical calculations show that this ARQ scheme offers a performance superior to both the basic ARQ scheme and the time-diversity scheme     

Performance of H.263 video transmission over wireless channelsusing hybrid ARQ

This paper proposes a hybrid ARQ error control scheme based on the concatenation of a Reed-Solomon (RS) code and a rate compatible punctured convolutional (RCPC) code for low-bit-rate video transmission over wireless channels. The concatenated hybrid ARQ scheme we propose combines the advantages of both type-I and type-II hybrid ARQ schemes. Certain error correction capability is provided in each (re)transmitted packet, and the information can be recovered from each transmission or retransmission alone if the errors are within the error correction capability (similar to type-I hybrid ARQ). The retransmitted packet contains redundancy bits which, when combined with the previous transmission, result in a more powerful RS/convolutional concatenated code to recover information if error correction fails for the individual transmissions (similar to type-II hybrid ARQ). Bit-error rate (BER) or signal-to-noise ratio (SNR) of a radio channel changes over time due to mobile movement and fading. The channel quality at any instant depends on the previous channel conditions. For the accurate analysis of the performance of the hybrid ARQ scheme, we use a multistate Markov chain (MSMC) to model the radio channel at the data packet level. We propose a method to partition the range of the received SNR into a set of states for constructing the model so that the difference between the error rate of the real radio channel and that of the MSMC model is minimized. Based on the model, we analyze the performance of the concatenated hybrid ARQ scheme. The results give valuable insight into the effects of the error protection capability in each packet, the mobile speed, and the number of retransmissions. Finally, the transmission of H.263 coded video over a wireless channel with error protection provided by the concatenated hybrid ARQ scheme is studied by means of simulations     

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.<>     

自适应调制混合ARQ系统中低时延冗余递增策略的研究

冗余递增混合ARQ能提供较高的数据通过率,但也带来了较大的传输时延。该文提出一种具备低时延冗余递增策略的混合ARQ系统并与自适应调制系统相结合,不但根据不同的接收信噪比,选取不同的调制方式,而且还选择不同的冗余递增策略。仿真和计算结果表明,与采用固定冗余递增策略的自适应调制混合ARQ系统相比,该系统在保证较高的数据通过率的前提下,大大降低了系统传输时延。     

基于节点选择的Turbo编码协同ARQ协议

文中给出了一种基于节点选择的Turbo编码协同ARQ(TC-ARQ)协议方案,并从理论上证明了采用基于节点选择的TC-ARQ协议相比传统的Turbo ARQ协议(T-ARQ)能获得更高的分集增益以及比非节点选择的协同ARQ协议更低的误帧率.仿真结果证实了该方案相对T-ARQ的优异性能,并仿真分析了节点数对节点选择性能增益的影响.     

A cooperative-ARQ protocol with frame combining

This article presents a low coordination overhead cooperative Automatic Repeat reQuest (ARQ) scheme with an integrated frame combiner, which exploits space diversity and cooperation between neighbouring nodes. A comparison between cooperation with and without frame combiner is also performed. In channels with a strong Line of Sight (LOS) component and low Signal-to-Noise ratio (SNR), the efficiency of the proposed protocol is many times higher than for other ARQ schemes. For non-LOS scenarios, the cooperative ARQ without frame combiner achieves the best efficiency results, and the overhead introduced by the frame combiner mechanism leads to results that can be even below the classical ARQ mechanism. In AWGN channels, the saturation throughput of the proposed scheme integrated into a IEEE 802.11 DCF based MAC is also studied. When the number of active stations is high, the cooperative ARQ without frame combiner shows to be the best option, while for light network loads, the presented scheme performs better.     

无线视频的一种码率控制方法

无线信道的高误码率对视频图像质量有很大的影响,前向纠错(FEC)和自动重发请求(ARQ)对于降低无线信道的误码率,提高图像质量有很好的效果。通过对FEC和ARQ方法的有效性分析,在TMN8的基础上提出一种简单的混合FEC/ARQ自适应模式选择码率控制方法。该方法首先预测报文丢失数量和纠错报文传输时延,从而选择合适的纠错编码模式,并为纠错编码分配比特数。实验结果表明该方法有效降低无线信道下报文丢失率,显著提高了图像质量。