Automatic Repeat Request Scheme Research Articles

The quadratic three-dimensional assignment problem: Exact and approximate solution methods

This paper reports on algorithm development for solving the quadratic three-dimensional assignment problem (Q3AP). The Q3AP arises, for example, in the implementation of a hybrid ARQ (automatic repeat request) scheme for enriching diversity among multiple packet re-transmissions, by optimizing the mapping of data bits to modulation symbols. Typical practical problem sizes would be 8, 16, 32 and 64. We present an exact solution method based upon a reformulation linearization technique that is one of the best available for solving the quadratic assignment problem (QAP). Our current exact algorithm is useful for Q3AP instances of size 13 or smaller. We also investigate four stochastic local search algorithms that provide optimum or near optimum solutions for large and difficult QAP instances and adapt them for solving the Q3AP. The results of our experiments make it possible to get good solutions to signal mapping problems of size 8 and 16.

Beacon-driven Leader Based Protocol over a GE Channel for MAC Layer Multicast Error Control

In wireless networks current standard MAC layer protocols don’t provide any error correction scheme for broadcast/multicast. In this paper, we enhance a Leader Based Protocol (LBP) and propose a Beacon-driven Leader Based Protocol (BLBP) for the MAC layer multicast error control. To guarantee a very low Packet Loss Ratio (PLR) under strict delay constraints for video multicast over a Gilbert-Elliott (GE) channel, we analyze BLBP and compare it with LBP and different application layer multicast error control schemes via simulation experiments. Both the theoretical analysis and simulation results show that BLBP can correct nearly all the errors for all receivers in the MAC layer and is more efficient than LBP. BLBP is also more efficient than the application layer Automatic Repeat request (ARQ) scheme and the total multicast delay is much shorter. BLBP is very good for real-time multicast applications with strict delay constraints.

ARQ-based switched antenna diversity in Markov channels

Since a switch and stay combining (SSC) scheme performs at the block level, it can be combined with an automatic repeat request (ARQ) scheme. Performance of an ARQ based SSC scheme in a Markov channel is analysed. It demonstrates the performance benefit with SSC-ARQ and the conditions set on the channel state for the scheme to be feasible.

PERFORMANCE ANALYSIS OF CELLULAR CDMA IN PRESENCE OF BEAMFORMING AND SOFT HANDOFF

The present paper proposes a scheme of combining soft handoff (HO) and beamforming in physical layer and automatic repeat request (ARQ) in link layer for improving the performance of data service in cellular CDMA. A stop and wait ARQ scheme has been assumed for data service. Joint effects of beamforming and soft handoff reduce delay, BER and increase throughput significantly. Impact of several parameters of soft handoff and beamforming on data performance has been evaluated. Both the cases of perfect and imperfect beamforming have been investigated. Effects of DOA (Direction of arrival) estimation error have also been indicated on data service.

ARQ strategies for relay cooperative systems

We propose two novel automatic repeat request (ARQ) strategies for relay cooperative system over Rayleigh fanding channel: one uses relay ARQ and the other destination ARQ. The BER performace of these two strategies is derived in fast block fading. Numerical analysis and simulation show the systems can get more performace 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 performce can be improved efficintly.

Satellite-3G Hybrid Networks: Impact of ACM and ARQ on TCP Performance

The adoption of satellite systems in providing broadband transmissions to mobile users such as trains, buses and vans is expected to be an interesting solution. The scenariowe considered refers to a hybrid network architecture, where a geostationary satellite forward link and a terrestrial 3G return link are used in order to exploit both the high bandwidth of a satellite channel and the lower propagation delay of a terrestrial path. The resulting round-trip delay is much shorter than that one experienced by using both the forward and return link via satellite. This is particularly appealing for overcoming the TCP efficiency degradation in high delay-bandwidth product and error prone channels. In this hybrid scenario, we used simulation results to compare the goodput of four of the most popular TCP variants, in the presence of a GOOD-BAD satellite channel, as the one experienced by mobile users. We applied an AdaptiveCoding and Modulation (ACM) technique as well, and studied its impact on TCP efficiency, when used both alone and in cooperation with an Automatic Repeat reQuest (ARQ) scheme of the Selective Repeat (SR) type with low persistency. Results obtained indicate that this hybrid architecture is advantageous for TCP transmissions in terms of average goodput, and that ACM is effective only if it is jointly used with ARQ schemes.

Performance of Hybrid ARQ Using Trellis-Coded Modulation Over Rayleigh Fading Channel

Trellis-coded modulation (TCM) has been shown as an attractive coding scheme for broadband wireless networks due to its bandwidth efficiency. Various hybrid automatic repeat request (ARQ) schemes using TCM as underlying forward error control have been proposed in the literature. In this paper, we study the performance of the hybrid ARQ with concatenated two-state TCM (CT-TCM) over Rayleigh fading channels. The throughput of the CT-TCM hybrid ARQ (CT-TCM-HARQ) scheme over a quasi-static Rayleigh fading channel is evaluated by both analysis and simulation. Besides, the performance of the CT-TCM-HARQ over fully interleaved Rayleigh fading channels is evaluated by simulation and compared with other existing TCM-based hybrid ARQ schemes. The numerical results demonstrate that the CT-TCM-HARQ achieves improved coding gain and throughput.

Cross-Layer Design and Analysis of Wireless Networks Using the Effective Bandwidth Function

In this paper, we propose a useful framework for the cross-layer design and analysis of wireless networks where ARQ (automatic repeat reQuest) and AMC (adaptive modulation and coding) schemes are employed. To capture the joint effect of the packet transmission error rate at the PHY layer and the packet loss probability at the MAC layer, we introduce the effective bandwidth function of the packet service process. Base on queueing analysis with this effective bandwidth function, our cross-layer design tries to satisfy the required packet loss probability by each user and minimize the average packet transmission error rate. Numerical examples are provided to show the usefulness and characteristics of our framework.

STBC Distributed ARQ Scheme for OFDM Ad-Hoc Wireless Networks

In this paper, we propose a novel highly reliable packet transmission protocol for ad-hoc wireless networks without deciding the route from a source node to a destination node in advance. The proposed protocol uses distributed surrounding nodes as transmitters of the retransmission packet when the transmitted packet contains an error. In this protocol, when a packet is not correctly received at the destination node, the source node and the surrounding nodes that have correctly received the packet simultaneously retransmit the same data packet to the destination node. The transmitting timing is triggered by the control packet transmitted from the source node. These operations are repeated until the packet reaches to the destination node like automatic repeat request (ARQ). Moreover, the retransmitted packet is encoded by one branch of the space time block code (STBC) for improving the performance with the network diversity effect. We call this method as STBC Distributed ARQ scheme. The performance of the proposed scheme is evaluated by the computer simulations.

Design of Rate-Compatible Irregular Repeat Accumulate Codes

We consider the design of efficient rate-compatible (RC) irregular repeat accumulate (IRA) codes over a wide code rate range. The goal is to provide a family of RC codes to achieve high throughput in hybrid automatic repeat request (ARQ) scheme for high-speed data packet wireless systems. As a subclass of low-density parity-check codes, IRA codes have an extremely simple encoder and a low-complexity decoder while providing capacity approaching performance. We focus on a hybrid design method which employs both puncturing and extending. We propose a simple puncturing method based on minimizing the maximal recoverable step of the punctured nodes. We also propose a new extending scheme for IRA codes by introducing the degree-1 parity bits for the lower rate codes and obtaining the optimal proportions of extended nodes through density evolution analysis. The throughput performance of the designed RC-IRA codes in hybrid ARQ is evaluated for both AWGN and block fading channels. Simulation results demonstrate that our designed RC codes offer good error correction performance over a wide rate range and provide high throughput, especially in the high and low signal-to-noise ratio regions.

Channel Estimation and Equalization Techniques in Downsampled ARQ Systems

In this paper, we study channel estimation and equalization for a class of bandwidth efficient automatic repeat request (ARQ) systems. In these systems, retransmissions achieve bandwidth efficiency through symbolwise downsampling. Unlike a standard ARQ scheme, in which an erroneous packet is fully repeated, more sophisticated hybrid ARQ systems retransmit a recoded data packet. However, many of these ARQ schemes do not consider the integration of ARQ protocols with receiver signal processing such as channel estimation and signal detection. In this paper, we present a joint multichannel estimation algorithm that exploits the structure of a symbolwise downsampled ARQ equipped network. We show that this new method can improve the identifiability conditions for channel estimation as well as the overall system performance

Throughput performance of Hybrid ARQ schemes with packet and code combining for DS‐CDMA downlink systems using orthogonal spreading sequences

AbstractIn this paper, we evaluate the throughput performance of Automatic Repeat reQuest (ARQ) and HARQ I, with packet combining, and HARQ II, with code combining, using convolutional codes for DS‐CDMA downlink systems employing a Rake receiver. The different user packets are code multiplexed using a set of orthogonal variable spreading factor sequences. The analysis is carried out in two extreme scenarios, with either a constant or a packet‐by‐packet independent multipath fading channel during the different transmissions. The obtained results are valid for any multipath intensity profile of the channel and take simultaneously into account AWGN noise, path gains estimation noise, intersymbol interference and multiuser interference. Copyright © 2008 John Wiley & Sons, Ltd.

MIMO throughput optimisation via quantised rate control

The problem of throughput maximisation in a wireless multiple-input multiple-output (MIMO) system using a quantised feedback, which is an appropriate model for practical systems with limited feedback capacity, is considered. Unlike the ergodic capacity that can be achieved through power control only, maximising the throughput in the block fading channels is based on appropriate rate control strategy. The optimal quantised rate control design for general MIMO systems is formulated and a gradient descent search algorithm to find the optimal solution is employed. It is seen that the proposed quantised rate control scheme with only a few bits of feedback considerably improves the throughput of a MIMO system. With the same amount of feedback overhead, the proposed quantised rate control with constant power is compared with the optimal quantised power control strategy with an optimised constant rate, and the result demonstrates the importance of rate control in throughput maximisation. The effect of quantised rate control in MIMO systems employing different automatic repeat request schemes is also investigated.

Fuzzy Logic Control of Adaptive ARQ for Video Distribution over a Bluetooth Wireless Link

Bluetooth's default automatic repeat request (ARQ) scheme is not suited to video distribution resulting in missed display and decoded deadlines. Adaptive ARQ with active discard of expired packets from the send buffer is an alternative approach. However, even with the addition of cross-layer adaptation to picture-type packet importance, ARQ is not ideal in conditions of a deteriorating RF channel. The paper presents fuzzy logic control of ARQ, based on send buffer fullness and the head-of-line packet's deadline. The advantage of the fuzzy logic approach, which also scales its output according to picture type importance, is that the impact of delay can be directly introduced to the model, causing retransmissions to be reduced compared to all other schemes. The scheme considers both the delay constraints of the video stream and at the same time avoids send buffer overflow. Tests explore a variety of Bluetooth send buffer sizes and channel conditions. For adverse channel conditions and buffer size, the tests show an improvement of at least 4 dB in video quality compared to nonfuzzy schemes. The scheme can be applied to any codec with I-, P-, and (possibly) B-slices by inspection of packet headers without the need for encoder intervention.

Differential FEC and ARQ for Radio Link Protocols

To bring TCP-based services to the mobile devices in a cellular network, it is necessary that TCP be extended over the wireless link. However, the performance of TCP severely degrades in a wireless medium. Hence, radio link protocols (RLPs) are used as an interface between TCP and the physical medium. RLPs fragment TCP segments into frames and use robust error correcting codes and fast retransmission schemes to shield the channel related losses from TCP, thus preventing TCP throughput degradation. In this paper, we show the limitations of the existing RLPs, which do not differentiate the frames generated from the same TCP segment. We claim that if selective frames are made more robust to transmission failures, then the performance of RLP and, hence, TCP can be improved. We identify such decisive frames and categorize them as crucial and noncrucial. Our claim is based on the fact that initial frames can afford a few trials of retransmissions, whereas the later ones cannot. We treat the frames differentially with respect to forward error correcting (FEC) coding and automatic repeat request (ARQ) schemes. We consider specific cases of FEC and ARQ strategies and show the qualitative difference in the performance of the RLP through analysis and simulations. The gain in the performance is more prominent when both FEC and ARQ (hybrid-ARQ) are used. The increase in TCP throughput with the proposed RLP is also demonstrated

Equation based rate control scheme for video streaming over wireless channels with link level ARQ

Equation based TCP-friendly rate control (TFRC) protocol has been proposed to support video streaming applications. In order to improve TFRC performance in wireless channels, the link level automatic repeat request (ARQ) scheme is usually deployed. However, ARQ cannot ensure strict delay guarantees, especially over multihop links. This paper introduces a theoretical model to deduce an equation for packet size adjustment in transport layer to minimize retransmission delay by taking into consideration the causative reasons inducing retransmission in link layer. An enhanced TFRC (ETFRC) scheme is proposed integrating TFRC with variable packet size policy. Simulation results demonstrate that higher goodput, lower packet loss rate (PLR), lower frame transmission delay and jitter with good fairness can be achieved by our proposed mechanism.

Evaluation of rate compatible block turbo codes for multimedia application in satellite communication network

AbstractIn this paper, we evaluate the performance of the hybrid automatic repeat request (ARQ) scheme combined with adaptive coding in satellite communication systems. A cross‐layer design which combines the ARQ scheme in the data link layer and adaptive coding and modulation in the physical layer is very important to maximize system throughput and/or performance. Due to the long round trip delay in satellite systems, the strategy to adopt may need to be different from that is used in the terrestrial systems. A rate compatible code is a desirable scheme for adaptive coding and hybrid ARQ. In this paper, we propose an adaptive coding scheme with hybrid ARQ using rate compatible block turbo codes, and demonstrate its performance on a mobile satellite channel for multimedia applications. The proposed rate compatible block turbo codes are a very effective tool to improve the performance of satellite systems using adaptive coding with hybrid ARQ. The simulation results presented in this paper reveal that the hybrid ARQ scheme combined with adaptive coding can improve the system performance by effectively compensating for the various channel attenuations. Copyright © 2006 John Wiley & Sons, Ltd.

Performance analysis of TFRC over wireless link with truncated link-level ARQ

In this paper, an analytical framework is proposed for evaluating the quality of service (QoS) of TCP-friendly rate control protocol (TFRC) in hybrid wireless/wired networks. For the wireless network, a link-level truncated automatic repeat request (ARQ) scheme is deployed to reduce the packet losses visible to the transport layer protocol. Two discrete time Markov chains (DTMC) are introduced to analyze the network performance and the QoS of the TFRC protocol, in terms of wireless link utilization, flow throughput, packet loss rate, and probability of end-to-end delay exceeding a prescribed threshold. Extensive simulations are performed to verify the accuracy of the analytical results. It is concluded that the analytical results are useful for optimizing the system parameters, such as the interface buffer size and the maximum number of retransmissions of the truncated ARQ scheme. With the optimal parameters, wireless link utilization can be maximized, and the QoS requirements of multimedia applications can be statistically guaranteed.

On the performance of turbo codes-based hybrid ARQ with segment selective repeat in WCDMA

In this paper, a new turbo codes-based hybrid automatic repeat request (TC-HARQ) scheme with segment selective repeat (SSR) is proposed. The main strategy is, upon retransmission, to repeat the data that are most important for the next round of decoding based on the distribution of residual errors after current decoding. The performance in terms of reliability and throughput is analyzed. To adapt to correlated fading channels where an inter-leaver is always employed before transmission, we further modify the SSR strategy so that data having experienced correlated deep fading are selected for retransmission. Finally, this proposed scheme is applied to the wideband code division multiple access (WCDMA) system under frequency selective fading channels. Simulation results demonstrate that in all single and multiple user cases, SSR-based TC-HARQ leads to significant throughput improvement with similar bit error rate (BER) performance as compared to type-I TC-HARQ.

Coding Performance of Hybrid ARQ Schemes

We develop a unified performance metric and detailed analysis for hybrid automatic repeat request (HARQ) schemes based on incremental redundancy (IR) and Chase combining (CC). The general result is applicable to both symbol-based and bit-interleaved coded modulations, to HARQ processes based on rateless and fixed-rate mother codes, and IR schemes with and without a self-decodability restriction. The analysis shows that IR over CC coding gains tend to increase with the initial coding rate, but decrease with the signal-to-noise (SNR) variation between retransmissions. The gains can also be diminished when a fixed-rate mother code is used or when the self-decodability criterion is imposed. The theoretical prediction is compared with observed gains at 10% codeword error rates based on turbo-coding simulations. For scenarios with moderately varying SNR between retransmissions, the analytical model tracks actual simulation results very well. However, when the SNR varies widely and the systematic part of the turbo codeword is effectively erased, the CC scheme could, in fact, outperform some IR schemes. For these scenarios, which can be induced by fast time-varying fading or long retransmission delays, the self-decodable IR and the CC schemes prove to be more robust without much performance comprise. Finally, we discuss adaptive improvement to the conventional IR schemes based on the analytical result