ARQ Systems Research Articles

Aggregation-Assisted Combining for MIMO Multiple ARQ Systems

This letter proposes an aggregation-assisted combining (AAC) for multiple-input multiple-output multiple automatic repeat request systems. The proposed AAC can be considered as a hybrid scheme of the symbol-level combining (SLC) and bit-level combining (BLC), which consists of the aggregation-assisted log-likelihood ratio (LLR) calculation and subsequent LLR combining stages. The aggregation-assisted LLR calculation stage is performed in a similar manner on the SLC except that the interference-to-noise reformulation is performed instead of the terminated-packet elimination; thus, the remaining interference from the terminated packets is regarded as additional noise. This additional noise can degrade the LLR quality from the aggregation-assisted LLR calculation stage. Therefore, the proposed AAC combines the currently calculated LLRs with the previously calculated LLRs similar to the BLC when the previously calculated LLRs have less LLR contaminations, i.e., they experience fewer numbers of terminated packets. The simulation results verify that the proposed AAC outperforms the BLC and even achieves a performance comparable with the SLC with simplified reception procedures.

基于二维Markov链和中继聚合方法的多跳ARQ系统吞吐量的分析

本文主要基于中继聚合的研究方法对多跳ARQ系统的吞吐量进行了分析。首先，对由一对收发节点和一个中继节点组成的两跳ARQ系统的节点状态进行了定义，通过建立二维的Markov链得到了四阶的状态转移矩阵，并因而求得两跳ARQ系统中继节点的状态转移概率。其次，在讨论由一对收发节点和N个中继节点组成的N + 1跳ARQ系统时，我们采用中继聚合将N个中继节点合并成一个超级中继并使得N + 1跳系统在原理上等效于两跳系统，从而求得N + 1跳ARQ系统中继节点的状态转移概率。最后，把多跳ARQ系统自身的状态定义为“G”和“B”，结合超级中继和直传链路的状态我们得到了多跳ARQ系统状态转移过程的八个状态，并通过稳态方程求得了多跳ARQ系统吞吐量的解析式。事实上，我们的结果也证实了多中继和多跳ARQ系统的吞吐量研究有统一的方法，有利于后续研究的统筹规划。 In this paper, we analyzed the throughput of multi-hop ARQ system based on the method of relay aggregation. Firstly, we defined the node-state of two-hop ARQ system which consisted of a pair of transceivers and one relay node, and obtained the four-state transition matrix by establishing a two-dimensional Markov chain, then obtained the state transition probability of relay nodes in two hop ARQ system. Secondly, in the N + 1-hop ARQ system composed of a pair of transceivers and N relay nodes, we used relay aggregation to merge N relay nodes into a super relay and made the N+1-hop system equivalent to the two-hop system in principle, then obtained the state transition probability of relay nodes in N + 1-hop ARQ system. Finally, we defined the state of the multi-hop ARQ system as “G” and “B”, and got eight-state of state transfer processes of multi-hop ARQ system by combining with the state of the super relay and direct channel, and obtained the analytical solution for the throughput of multi-hop ARQ systems based on the steady-state equation. In fact, it was shown that there was a unified method to study the throughput performance of multi-relay and multi-hop ARQ system.

Optimum Energy- and Spectral-Efficient Transmissions for Delay-Constrained Hybrid ARQ Systems

This paper discusses the energy- and spectral-efficient transmissions for delay-constrained wireless communication systems utilizing hybrid automatic repeat request (HARQ). Three design metrics are considered: 1) the energy efficiency (EE) measured by the average energy required to successfully deliver one information bit from a source to its destination; 2) the spectral efficiency (SE) defined as the average data rate per unit bandwidth; and 3) the average energy per bit normalized by the SE. Optimum system designs with respect to different metrics are developed by analytically identifying the sequence of transmission energy that should be employed at different retransmissions. The optimum energy distributions are calculated with a new backward sequential calculation method, where the energy at each retransmission round is expressed as a closed-form expression of a wide range of practical system parameters, such as circuit power and channel coding in the physical layer and frame length and protocol overhead in the media access control layer. Reducing the SE-normalized energy per bit yields a balanced tradeoff between EE and SE. Numerical results demonstrate that reducing the SE-normalized energy per bit achieves a 26.7% SE gain over the system that minimizes the average energy per bit; yet, the EE of the two systems is almost identical.

Energy efficiency analysis of antenna selection multi‐input multi‐output automatic repeat request systems over Nakagami‐mfading channels

In this study, the authors investigate energy efficiency in antenna selection multi-input multi-output automatic repeat request (MIMO ARQ) wireless systems. The authors first derive an approximate expression for the average frame-error rate (FER) in antenna selection MIMO systems over quasi-static Nakagami-m fading channels. The FER approximation is then used to obtain an analytical expression of an energy-efficiency metric that is defined as the total energy required to successfully deliver one information bit. The authors prove that this energy-efficiency metric is a quasi-convex function with respect to the average signal-to-noise ratio value. Based on this analysis, the authors obtain the optimal value of the average energy per transmitted data symbol such that the total energy consumption in the system is minimised. The results show that the energy efficiency in antenna selection MIMO ARQ systems is improved when the number of equipped antennas is increased. Simulation results are provided to validate the analysis.

Closed-Form Error Analysis of AF-CARQ with CSI-Assisted Relay over Nakagami- $$m$$ m Fading Channels

This paper presents a new Amplify-and-Forward Cooperative Automatic Repeat reQuest protocol with channel state information-assisted relay which is more suitable for the only-read access networks. The channels of any pair of terminations are quasi static flat Nakagami- $$m$$ m fading channels, which are mutually independent and non-identically distributed. Assuming that the coherent equal gain combining is adopted to combine the retransmitted signals from the same link at the destination and selective combining is adopted to the signals from different links. Based on the approximation of product of Nakagami- $$m$$ m variables, we obtain the end-to-end signal-to-noise rate of any link. The closed-form expression of the average bit error rate for several modulation schemes is obtained by analyzing cumulative distribution function (CDF) and Gaussian Q-function. Then we analyze the amount of fading of the fading channels by the $$n$$ n order moment which is obtained by CDF. Numerical simulation results show that the relay node can resist the fading of system effectively comparing with the system without relay node. And with the increasing of the number of transmission, the performance advantage of relay link is more and more obviously. It is better to let the maximum transmission time $$F=6$$ F = 6 , which is very useful for improving the transmission efficiency of the truncated ARQ system. The maximum reduction of amount of fading can be reached when $$t=3$$ t = 3 , if the total number of transmission is $$f=6$$ f = 6 . The number of bits in the frame should not have too big.

Generalized Pollaczek-Khinchin Formula for Markov Channels

The wireless fading channels with finite input buffer, Poisson arrivals and two-state Markov modulated service processes (MMSP) are modeled as M/MMSP/1/K queues in this paper. The existing performance analyses of Markov channels are almost all based on the matrix-geometric method, which provides little physical insights for system design. By contrast, we focus on deriving closed-form analytic expressions with physical interpretations in terms of system parameters of interest. Our main contribution is to derive the generalized Pollaczek-Khinchin (P-K) formula of M/MMSP/1/K queue from start-service probability to explore the impact of state transitions on the queueing behavior of Markov channels. This generalized P-K formula reveals that the performance of wireless channels with varying rates can be fully characterized by a newly defined system parameter, called state transition factor β, which clearly explains the reason that the channel with slow state transition rate owns a larger delay for the same channel capacity. In the extreme case when the state transition factor β approaches 0, we show that the channel under consideration can be approximately modeled as an M/G/1 queue. We use the Type I Hybrid ARQ system with a fixed data-rate as an example in this paper to illustrate our results.

A Novel Memory-based ARQ System with its Analysis of Throughput

The Primitive Bit Error Rate is much higher in severe electronic-magnetic environment, which results in much more retransmissions for an ARQ data transceiver; this means a lower efficiency of transmission. To cope with the above problem, this paper proposes a new mechanism, which is based on majority-voting. Through theoretical analysis and simulations, this novel approach shows better performance than those conventional ones.

Distribution of high-definition video in 802.11 wireless home networks

Wireless distribution of multimedia contents through 802.11 networks in the home environment presents a number of advantages which have fueled the interest of industry in recent years, such as simple connectivity and data delivery to a variety of devices. Together with High-Definition (HD) contents, multimedia wireless distribution has been proposed for several applications, such as IPTV and Digital TV distribution for multiple devices in the home environment. However, the quality of wireless multimedia services is deteriorated by random packet losses caused by the changing channel behavior. For these scenarios, we propose in this paper a multicast distribution system for High-Definition video over 802.11 wireless networks based on rate-limited packet retransmission. Unlike previous works, which require on-line calculation of the optimal retransmission strategies, the presented system employs optimal retransmission strategies obtained through an off-line optimization process. This approach, based on Stochastic Dynamic Programming, allows a lower on-line complexity and, when compared to another limited rate ARQ system, offers a higher packet recovery and improvements in video quality for low end-to-end delays requirements.

IPTV Multicast Over Wireless LAN Using Merged Hybrid ARQ With Staggered Adaptive FEC

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> Internet Protocol TV (IPTV), an emerging internet application, provides more flexibility and interactivity for users because of its embedded return channel. Wireless 802.11 networks, used as the last hop of IPTV networks, would add another dimension of mobility, which is of great value for hot spot deployment and is increasingly required for in-home content distribution. However, a wireless channel may suffer from multi-path fading and interference, which may cause random and burst packet loss and impact users' quality of experience of an IPTV program. We report the design, implementation and evaluation of Merged Hybrid Adaptive FEC and ARQ (MHARQ) system for IPTV multicast over wireless LANs. In MHARQ, an IPTV cache server is introduced to improve the reliability for the last hop wireless distribution. MHARQ combines the advantages of receiver-driven staggered FEC and hybrid ARQ schemes to compensate the large dynamic range of WLAN channels and to achieve high reliability, scalability and wireless bandwidth efficiency for IPTV multicast. We also address backward compatible FEC encoding and decoding, audio and video synchronization issues in practical system implementation. Using the ORBIT radio grid test bed, we have investigated the performance of the proposed MHARQ system with various numbers of users per AP and different numbers of APs per IPTV cache server. It is demonstrated via real system implementation on ORBIT that MHARQ improves wireless bandwidth efficiency and scalability for reliable IPTV multicast, compared with existing reliable multicast schemes. </para>

Multilevel Control Signaling for Hybrid ARQ in the UMTS HSDPA System

In this paper, we propose and analyze a multi-level acknowledgement scheme for hybrid ARQ (H-ARQ) systems, which modifies the general ACK/NAK signals to represent multilevel information. For instance, the other signals except the ACK/NAK signals may be used for scheduling of retransmission in the H-ARQ scheme, which results in increasing the resolution of the uplink channel estimation signals. Simulation results demonstrate that when the retransmission interval is set to the optimal length, the proposed H-ARQ scheme shows a 0.5-2dB gain with properly selected parameters.

A Hybrid ARQ System with Erasures Correction and Parity Retransmission

A modified type of Hybrid ARQ system with erasures correction and parity bits retransmission is considered. Performance of the system is analyzed under assumption that the forward channel suffers from Nakagami common fading and additive white Gaussian noise. A good agreement between theoretical results and simulation is achieved. The proposed ARQ protocol is compared with other known Hybrid ARQ algorithms. It demonstrates significantly higher throughput efficiency in a range of SNR.

A Novel SNR Estimation Technique Associated with Hybrid ARQ

By using multiple repeated signal replicas to formulate the accumulative observed noisy signal sequence (AONSS) or the differential observed noisy signal sequence (DONSS) in the hybrid ARQ system, a novel data-aided maximum likelihood (DA ML) SNR estimation and a blind ML SNR estimation technique are proposed for the AWGN channel. It is revealed that the conventional DA ML estimate is a special case of the novel DA ML estimate, and both the proposed DA ML and the proposed blind ML SNR estimation techniques can offer satisfactory SNR estimation without introducing significant additional complexity to the existing hybrid ARQ scheme. Based on the AONSS, both the generalized deterministic and the random Cramer-Rao lower bounds (GCRLBs), which include the traditional Cramer-Rao lower bounds (CRLBs) as special cases, are also derived. Finally, the applicability of the proposed SNR estimation techniques based on the AONSS and the DONSS are validated through numerical analysis and simulation results.

Adaptive Hybrid ARQ Systems With BCJR Decoding

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> We propose and evaluate a novel method of constructing Hybrid Automatic Repeat reQuest (HARQ) systems using the specific properties of the Bahl, Cocke, Jelinek, and Raviv (BCJR) error-correcting algorithm. Because the convergence to the actual codeword is not always guaranteed with the BCJR approach, we propose a system in which two different types of Negative AcKnowledgement messages (NAKs) are employed. The first type is the conventional 1-bit NAK, and the second type specifies retransmission pattern in such a way that the additional parity bits are concentrated on the parts of the code trellis that did not converge to a valid sequence. This is different from the traditional construction of rate-compatible punctured codes (RCPCs), which attempts to obtain the optimal weight distance properties of the codes without taking the convergence properties of the BCJR decoder into account. We demonstrate the performance of the algorithm using RCPCs, and we show that our system outperforms the best known conventional HARQ scheme in terms of the throughput and the average length of retransmitted blocks on practical Gaussian, Rayleigh, and thresholded Rayleigh channels. Moreover, as opposed to other adaptive HARQ algorithms, our solution requires no precomputed lookup tables, and it is robust to changes in the channel characteristics and only introduces moderate increase in feedback link throughput requirements. </para>

Joint Rate and Power Adaptation for Type-I Hybrid ARQ Systems Over Correlated Fading Channels Under Different Buffer-Cost Constraints

We present a general framework for the computation of the optimal scheduling policies for delay and overflow-constrained joint rate and power adaptations for type-I hybrid automatic-repeat-request systems. This framework can be applied to adaptive resource-allocation problems on correlated flat-fading or frequency-selective fading channels for bursty nonconstant packet arrivals. It is shown that the optimal-rate and powercontrol laws can be obtained by solving the formulated Markov decision process problems. We consider two cases for packet scheduling over wireless channels that are of significant practical importance. In the first case, we assume that the transmitter perfectly knows the channel-state information (CSI) at the beginning of the transmission. The transmitter is also provided with the decoding result for the previous transmission in terms of observation feedback at the end of the transmission. Second, we consider the scheduling problem when the transmitter does not know the CSI at the time of transmission, but it makes the transmission decision based on the history of previous transmissions and corresponding outcomes. In both cases, our objective is to minimize transmission power, and the optimal policies are computed under two different buffer-cost constraints, namely, the average buffer delay and the average packet overflow rate. The results of this paper are of importance for the development of modern wireless standards that support heterogeneous multimedia and Internet traffic with certain application-dependent-delay and packet-dropping requirements.

POMDP-Based Coding Rate Adaptation for Type-I Hybrid ARQ Systems over Fading Channels with Memory

We address the issue of optimal coding rate scheduling for adaptive type-I hybrid automatic repeat request wireless systems. In this scheme, the coding rate is varied depending on channel, buffer and incoming traffic conditions. In general, we consider the hidden Markov model for both time-varying flat fading channel and bursty correlated incoming traffic. It is shown that the appropriate framework for computing the optimal coding rate allocation policies is partially observable Markov decision process (POMDP). In this framework, the optimal coding rate allocation policy maximizes the reward function, which is a weighted sum of throughput and buffer occupancy with appropriate sign. Since polynomial amount of space is needed to calculate the optimal policy even for a simple POMDP problem, we investigate maximum-likelihood, voting and Q-MDP policy heuristic approaches for the purpose of efficient and real-time solution. Our results show that three heuristics perform close to completely observable system state case if the fading and/or traffic state mixing rate is slow. On the other hand, when the channel fading is fast, Q-MDP heuristic is the most throughput-efficient among considered heuristics. Also, its performance is close to the optimal coding rate allocation policy of fully observable system state case. We also explore the performances of the proposed heuristics in the bursty correlated traffic case and show that maximum-likelihood and voting heuristics consistently outperform the non-adaptive case

Optimum Subpacket Transmission for Hybrid ARQ Systems

Optimum Subpacket Transmission for Hybrid ARQ Systems

Blockage mitigation techniques in satellite communications

This article proposes systematic approaches to minimize severe channel degradation. Detection of channel condition is performed by means of two continuous ARQ NAK counting schemes. Stop-and-wait ARQ non-NAK counting is used for timed complete blockage. A single (31,21,5) code is designed for all the ARQ systems proposed. After the blockage state of a transmission channel is determined, satellite link parameter trade-offs and other specific remedy alternatives are recommended to enhance channel performance. System performance criteria are derived with different Earth station capabilities.

Efficient partial retransmission ARQ strategy with error detection codes by feedback channel

The paper presents and analyses a new partial retransmission ARQ strategy (PRAS) which uses error detection in the feedback direction to enable the transmitter to pinpoint and repeat only an individually errored subblock resulting in more efficient use of a communication channel. The scheme also increases the probability of successful retransmission and provides an adaptive overhead. The throughput analysis shows a substantial improvement over a conventional selective repeat ARQ system. A practical implementation (selective cell retransmission (SCR)) demonstrates the technique over an asynchronous transfer mode (ATM) satellite link using hybrid ARQ to provide selective retransmission (i.e. supporting both ATM real-time and TCP/IP applications). A comparison with RS (n=255, k=233, t=11) coding shows that it can achieve a higher TCP throughput for a BER up to 7/spl times/10/sup -4/.

Advances in the performance of Reed-Solomon codes

This paper presents generalized expressions for the probabilities of correct decoding and decoder error for Reed-Solomon (RS) codes. In these expressions, the symbol error and erasure probabilities are different in each coordinate in a codeword. The above expressions are used to derive the expressions for reliability and delay for Type-I hybrid ARQ (HARQ-I) systems when each symbol in a packet (multiple codewords per packet) has unique symbol error and erasure probabilities. Applications of the above results are demonstrated by analyzing a bursty-correlative channel in which the symbols and codewords within the packet are correlated.

Performance of ARQ Go-Back-N protocol in Markov channels with unreliable feedback

In this paper, an ARQ Go-Back-N protocol with time-out mechanism is studied. Transmissions on both the forward and the reverse channels are assumed to be subject to Markovian errors. A recently developed approach, based on renewal theory, is further extended and the steady state average number of packets in the ARQ system is evaluated. This allows us to determine analytically both throughput and transmission delay of the system. Simulation results, that confirm the analysis, are also presented. Based on the analysis, the trade-off involved in the choice of the time-out parameter is identified and discussed.