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.     

Hybrid ARQ scheme using interleaved Reed-Solomon codes in apower-controlled DS-CDMA cellular system

A new hybrid automatic repeat request (ARQ) scheme is proposed for data transmission in a power-controlled direct sequence (DS) code division multiple access (CDMA) system cellular system. The data frame is composed of interleaved Reed-Solomon codes. The depth of interleaving is determined by a power-control interval. After decoding each codeword with algebraic decoding, the post-decoding processor decides whether to accept the codeword or to discard it by using channel state information from the power-control processor. The proposed hybrid ARQ scheme significantly reduces the probability of undetected error among accepted codewords without significantly reducing the throughput     

Incremental-redundancy transmission for meteor-burst communications

The performance of type-II hybrid automatic repeat request (ARQ) is compared to that of fixed-rate type-I hybrid ARQ for meteor-burst communications. Maximum throughput is obtained for meteor-burst communications by using a transmission scheme for which the information rate of the code, varies in response to the fluctuations in the power received from a meteor trail. For type-II hybrid ARQ, a variation in the code rate is inherent in the coding scheme. On the first transmission that is made for a data block, a code of relatively high rate is used, but if an additional transmission is required, only redundant symbols are sent, and this reduces the overall rate of the code. The performance measure is the throughput per trail, which is defined as the expected number of successfully received information bits for a given meteor trail. The authors also develop an approximation for the average value of the throughput, averaged over the parameters of the meteor trail. Numerical results for Reed-Solomon codes are included to illustrate the relative performance of the various schemes. It is shown that the throughput is larger for type-II hybrid ARQ than for either fixed-rate type-I hybrid ARQ or ARQ without forward-error-correction     

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.     

无线光通信差错控制系统的时间参数特性

在无线光通信系统中,光强闪烁和大气衰减等因素将使通信系统产生长突发误码,结合Turbo码,建议并分析了两种差错控制方案中时间参数的特性.对于Turbo码 信道交织的差错控制方案,仿真分析了不同信道交织深度下的无线光通信系统性能,给出了特性曲线.对于Turbo码 反馈重发(ARQ)的方案,仿真结果表明反馈环路延迟时间的变化不影响系统的平均吞吐量,但是将影响平均数据传输延迟和重发次数的概率分布.     

Hybrid ARQ schemes for point-to-multipoint communication overnonstationary broadcast channels

Hybrid automatic-repeat-request (ARQ) error control schemes make use of both error detection and error correction in order to achieve high throughput and low undetected error probabilities on two way channels. Two hybrid ARQ schemes, termed hybrid go-back-N (HGB- N) and hybrid selective-repeat (HSR), are proposed for point-to-multipoint communications over broadcast channels. Both schemes incorporate a concatenated code for error correction and error detection. The performance study of the hybrid schemes is based on a two-state Markov model of a burst noise channel. An analytic solution is derived for the throughput efficiency of the HSR scheme, while approximations and computer simulation are used to evaluate the throughput efficiency of the HGB-N scheme. It is shown that the schemes perform considerably better than the corresponding pure ARQ schemes in which a block code is used for error detection only, especially in environments with a large number of receivers and large channel roundtrip delays, such as satellite broadcast links     

Efficiency of error-control schemes for real-time wireless applications on the Gilbert channel

The design of a bandwidth-efficient physical layer for wireless access has always been a challenging task, due to the harsh environment, characterized by impairing phenomena such as radio interference, fading, and shadowing. With circuit switching, a bit-error rate suitable for real-time applications such as voice and video is guaranteed by adopting robust forward error correction (FEC) codes and proper power-budget margins to face fading problems. With this approach, automatic repeat request (ARQ) is used only for applications that require a much lower error rate and can tolerate high delays. The introduction of the packet technique allows the use of ARQ even for real-time traffic. We compare the efficiency of three error-recovering techniques in the presence of traffic with delay constraints, when the memory property of the wireless segment is represented by the Gilbert-Elliot channel. The techniques compared are FEC with interleaving, real-time ARQ, and erasure coding (EC). The comparisons are performed by using both analytical and simulation tools. Two new analytical models are introduced to evaluate the performance of FEC and EC. Simulation is used to validate the analytical results and to derive the performance of real-time ARQ. The numerical results show that when the channel memory increases well beyond the packet-transmission time, the performance of FEC impairs due to the limited interleaving depth, while ARQ and EC remain effective.     

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     

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     

Improving Wireless TCP Throughput by a Novel TCM-Based Hybrid ARQ

A novel hybrid ARQ (HARQ) scheme using a concatenated two-state trellis-coded modulation (CT-TCM) code is proposed for improving wireless TCP throughput. A distinguished feature of the proposed scheme is that the heavily punctured TCM codes are used for retransmissions of the corrupted data block, which are combined at the receiver with the previously received sequences of the same data block for decoding. By this method, significantly improved coding gain and efficient spectrum utilization can be achieved with very low complexity. A Markov model is developed to evaluate TCP throughput over the proposed HARQ in wireless link. By both analysis and simulation, we demonstrate that compared with other existing TCM-based ARQ schemes, significant improvement of TCP throughput over wireless links is achieved by the proposed CT-TCM HARQ while smaller buffer size is required at the access point.     

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.     

An integrated FEC coding scheme for ATM transmission over regenerative satellite networks

The application of asynchronous transfer mode (ATM) on both wireless and satellite networks requires system adaptation. This adaptation has to improve the overall system's performance, and achieve high quality‐of‐service classes approaching that for fibre‐optic communications. In this paper, a new integrated forward‐error‐correction (FEC) coding scheme is introduced for ATM transmission over regenerative satellite networks. The proposed FEC scheme is a concatenation of two Reed–Solomon codes tailored for the header and payload parts of the ATM cell. This integrated coding scheme is shown to significantly improve the cell loss ratio as compared to the standard CRC code used in the ATM cell header. We obtain both upper and lower performance bounds for the concatenated code and check their accuracy when compared to exact system's performance. Both analytical and simulation results show that a cell loss ratio and bit‐error rate (BER) of 10^?25 and 10^?7 can be, respectively, achieved with minimum delay requirements on the SATCOM link. Finally, an approximation for the system's throughout is obtained. It is shown that using a hybrid selective‐repeat automatic‐repeat‐request (SR‐ARQ) with the RS code, a large throughput of approximately 0.843 can be achieved at BERs lower than 10^?7 for data services. Copyright © 2005 John Wiley & Sons, Ltd.     

Hybrid ARQ with selective combining for fading channels

We propose and analyze a hybrid automatic repeat request (ARQ) with a selective combining scheme using rate-compatible punctured convolutional (RCPC) codes for fading channels. A finite-state Markov channel model is used to represent the Rayleigh fading channels. We show that the hybrid ARQ with selective combining yields better performance than the generalized type-II ARQ scheme for fading channels. Furthermore, simulation results of real-time video time division multiple access (TDMA) transmission system are given. Better video quality can be obtained by our proposed scheme, with a bounded delay. Analytical results of throughput and packet error rate (PER) are compared to the simulated results. Our analysis based on a finite-state Markov channel model, is shown to give good agreement with simulations     

Turbo-coded ARQ schemes for DS-CDMA data networks over fading andshadowing channels: throughput, delay, and energy efficiency

Modified ARQ (automatic-repeat-request) techniques based on turbo coding are investigated for asynchronous DS-CDMA (direct-sequence code-division multiple-access) data networks under shadowing and frequency selective fading channel conditions. The throughput, delay, and energy efficiency performance of standard ARQ, metric combining, and RCPT (rate compatible punctured turbo) coded ARQ schemes are compared via simulations. The RCPT/ARQ schemes are shown to outperform the other two schemes in terms of both throughput and energy efficiency at the cost of larger delay and complexity. In addition, maximum network throughput is investigated for different ARQ schemes under energy constraints     

A Comparison of Block and Convolutional Codes in ARQ Error Control Schemes

ARQ methods of error control can considerably improve the reliablity of data transmission in such areas as satellite communications, computer networks, etc. A number of ARQ schemes using both block and convolutional codes have appeared in the literature. In this paper, the following problem is addressed. Given two different implementations of an ARQ scheme, one using a block code and the other using a convolutional code, such that the bit error probability of both implementations does not exceed some specific value, which implementation has the higher throughput and under what conditions will it be attained? The comparison is made for three basic retransmission schemes using both hybrid and pure ARQ: stop-and-wait, go-back-N, and selective repeat. Numerical estimates of the throughput were obtained using approximate theoretical expressions for BCH codes and simulation results for sequential decoding of rate 1/2 convolutional codes. Parameters optimizing the performance of both block and convolutional codes for different channel conditions and round trip delays were found and were used to obtain these numerical estimates. Comparison of the quantitative results indicates a trend toward preferring convolutional codes as delay and/or block length increases. A binary symmetric channel with noiseless feedback was assumed. Possible implications for the Gaussian channel are also discussed.     

Adaptive Modulation and Coding with Selective Retransmission under OFDM signaling

In this paper, we present bandwidth efficient selective retransmission method in conjunction with adaptive modulation and coding (AMC) scheme for OFDM waveform. In the proposed method, when a packet failure occurs, receiver requests retransmission of information symbols prone to error corresponding to the low signal-to-noise ratio (SNR) sub-carriers of OFDM modulation. The selective retransmission avoids unnecessary retransmission and AMC chooses a proper modulation and coding scheme with an objective to maximize the throughput. Our method achieves higher throughput as compared to conventional retransmission methods such as Chase combining hybrid automatic repeat reQuest (CC-HARQ) and incremental redundancy hybrid automatic repeat reQuest (IR-HARQ). We also provide the throughput and delay analysis of the proposed method for non-truncated ARQ. The simulation results demonstrate throughput gain without significant impact on delay as compared to the conventional retransmission approaches.     

EXIT chart-aided adaptive coding for MMSE turbo equalization with multilevel BICM

This letter proposes adaptive coding (AC) for multilevel bit interleaved coded modulation (ML-BICM) with MMSE turbo equalization, of which aim is to minimize the information rate loss due to the mismatch between the channel realization and channel coding. With the aid of the knowledge about extrinsic information transfer (EXIT) characteristics at the receiver, the code parameters such as code rates and/or generator polynomials are adaptively selected independently in each the ML-BICM layer. Numerical results show that throughput efficiency can be significantly improved with the proposed AC technique over the automatic repeat request (ARQ) technique with fixed code rate.     

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     

基于并行级联LDPC码的递增冗余HARQ方案及性能分析

并行级联LDPC码是由多个码率不同的子码,经并行级联后得到的码率可变的LDPC码.本文提出了基于并行级联:LDPC码的递增冗余HARQ方案,给出了这种方案的吞吐量性能封闭解.在AWGN信道和Rayleigh衰落信道下,通过仿真将新方案的性能和随机LDPC码的性能进行了比较.结果显示,并行级联LDPC码的递增冗余HARQ方案性能接近随机LDPC码,但编、译码更简单,参数选择范围更广.     

Joint Source and Channel Coding for MIMO Systems: Is it Better to be Robust or Quick?

A framework is developed for optimizing the tradeoff between diversity, multiplexing, and delay in multiple-input multiple-output (MIMO) systems to minimize end-to-end distortion. The goal is to find the optimal balance between the increased data rate provided by antenna multiplexing, the reduction in transmission errors provided by antenna diversity and automatic repeat request (ARQ), and the delay introduced by ARQ. First, closed-form analytical results are developed to minimize end-to-end distortion of a vector quantizer concatenated with a space-time MIMO channel code in the high SNR regime. The minimization determines the optimal point on the diversity-multiplexing tradeoff curve. For large but finite SNR this optimal point is found via convex optimization, which is illustrated with an example of a practical joint source-channel code design. It is then shown that for MIMO systems with ARQ retransmission, sources without a delay constraint have distortion minimized by maximizing the ARQ window size. This results in a new multiplexing-diversity tradeoff region enhanced by ARQ. However, under a source delay constraint the problem formulation changes to account for delay distortion associated with random message arrival and random ARQ completion times. In this case, the simplifications associated with a high SNR assumption break down, and a dynamic programming formulation is required to capture the channel diversity-multiplexing tradeoff as well as the random arrival and retransmission dynamics. Results based on this formulation show that a delay-sensitive system obtains significant performance gains by adapting its operating point on the diversity-multiplexing-delay region to system dynamics.