Hybrid Automatic Repeat Request System Research Articles

Polar Codes: Encoding/Decoding and Rate-Compatible Jointly Design for HARQ System

Polar coding are the first class of provable capacity-achieving coding techniques for a wide range of channels. With an ideal recursive structure and many elegant mathematical properties, polar codes are inherently implemented with low complexity encoding and decoding algorithms. Since the block length of the original polar construction is limited to powers of two, rate-compatible polar codes (RCPC) are presented to meet the flexible length/rate transmission requirements in practice. The RCPC codes are well-conditioned to combine with the hybrid automatic repeat request (HARQ) system, providing high throughput efficiency and such RCPC-HAPQ scheme is commonly used in delay-insensitive communication system. This paper first gives a survey of both the classical and state-of-the-art encoding/decoding algorithms for polar codes. Then the RCPC construction methods are discussed, including the puncturing, shortening, multi-kernel construction, etc. Finally, we investigate several RCPC-HARQ jointly design systems and discuss their encoding gain and re-transmission diversity gain.

Development of hybrid ARQ protocol for the quantum communication system on stabilizer codes

In this paper, we develop a novel hybrid automatic-repeat-request (ARQ) protocol for the quantum communication system using quantum stabilizer codes. The quantum information is encoded by stabilizer codes to against the channel noise. The two-photon entangled state is prepared for codeword secure transmission. Hybrid ARQ protocol rules the recognition and retransmission of error codewords. In this protocol, the property of quantum entangled state ensures the security of information, the theory of hybrid ARQ system improves the reliability of transmission, the theory of quantum stabilizer codes corrects the flipping errors of codewords. Finally, we verify the security and throughput efficiency of this protocol.

HARQ in Full-Duplex Relay-Assisted Transmissions for URLLC

The Release 16 completion unlocks the road to an exciting phase pertain to the sixth generation (6G) era. Meanwhile, to sustain far-reaching applications with unprecedented challenges in terms of latency and reliability, much interest is already getting intensified toward physical layer specifications of 6G. In support of this vision, this work exhibits the forward-looking perception of full-duplex (FD) cooperative relaying in support of upcoming generations and adopts as a mean concern the critical contribution of hybrid automatic repeat request (HARQ) mechanism to ultra-reliable and low-latency communication (URLLC). Indeed, the HARQ roundtrip time (RTT) is known to include basic physical delays that may cause the HARQ abandonment for the 1 ms latency use case of URLLC. Taking up these challenges, this article proposes a hybrid FD amplify-and-forward (AF)-selective decode-and-forward (SDF) relay-based system for URLLC. Over this build system, two HARQ procedures within which the HARQ RTT is shortened, are suggested to face latency and reliability issues, namely, the proposed and the enhanced HARQ procedures. We develop then an analytical framework of this relay based HARQ system within its different procedures. Finally, using Monte-Carlo simulations, we confirm the theoretical results and compare the proposed relay-assisted HARQ procedures to the source-to-destination (S2D) HARQ-based system where no relay assists the communication between the source and the destination.

Optimization of Two-Way Network Coded HARQ With Overhead

To account for the ever-increasing demand for wireless broadband, it is critical to develop new techniques that can increase throughput. Network-coded (NCed) hybrid automatic repeat request (HARQ) has previously been shown to hold much potential for increasing network throughput by utilizing the retransmissions and side-information. However, the previous performance analysis did not take into account that the implementation of NCed HARQ requires additional control information that indicates which packets are included in one network coded packet and additional ARQ acknowledgements for the packets overheard by the unintended users. In this paper, we analyze the resources required for additional overhead and derive the outage probability and throughput for both downlink and uplink. With the analytical expressions and Monte Carlo simulation results, we study the trade-off between the maximum number of users (MNU) for NCed HARQ system and the overall throughput. Finally, we numerically show the existence of the optimal MNU and derive an approximate closed-form expression for the optimal value.

FPGA-Based Channel Coding Architectures for 5G Wireless Using High-Level Synthesis

We propose strategies to achieve a high-throughput FPGA architecture for quasi-cyclic low-density parity-check codes based on circulant-1 identity matrix construction. By splitting the node processing operation in the min-sum approximation algorithm, we achieve pipelining in the layered decoding schedule without utilizing additional hardware resources. High-level synthesis compilation is used to design and develop the architecture on the FPGA hardware platform. To validate this architecture, an IEEE 802.11n compliant 608 Mb/s decoder is implemented on the Xilinx Kintex-7 FPGA using the LabVIEW FPGA Compiler in the LabVIEW Communication System Design Suite. Architecture scalability was leveraged to accomplish a 2.48 Gb/s decoder on a single Xilinx Kintex-7 FPGA. Further, we present rapidly prototyped experimentation of an IEEE 802.16 compliant hybrid automatic repeat request system based on the efficient decoder architecture developed. In spite of the mixed nature of data processing—digital signal processing and finite-state machines—LabVIEW FPGA Compiler significantly reduced time to explore the system parameter space and to optimize in terms of error performance and resource utilization. A 4x improvement in the system throughput, relative to a CPU-based implementation, was achieved to measure the error-rate performance of the system over large, realistic data sets using accelerated, in-hardware simulation.

IRREGULAR REPETITION CODE HYBRID ARQ IN WIRELESS SYSTEM

Error control consists of error detection and error correction in the communication system. The purpose of this research work is to reduce error in the wireless communication system by using the advantages of both error correction techniques which are forward error correction (FEC) and automatic repeat request (ARQ). Thus, error can be corrected without retransmission and also via retransmission(s) when needed. Combination of FEC and ARQ is known as Hybrid ARQ. In this paper, Hybrid ARQ system is designed using three components which are the irregular repetition code (IRC) as a simple code, bit-interleaved coded modulation with iterative decoding (BICM-ID) as a simple Turbo processing and ARQ. The HARQ system is enhanced by the extended mapping (EM) adopted in the mapping system. The performance of the systems is evaluated in the additive white Gaussian noise (AWGN). The results show the Hybrid ARQ with extended mapping (Hybrid ARQ-EM) outperforms Hybrid ARQ with standard mapping (Hybrid ARQ-SM). Hybrid ARQ-EM achieves low bit error rate BER (10-5) at low signal-to-noise ratio SNR which only 3.03dB close to the theoretical limit. The proposed system Hybrid ARQ-EM achieves 52 percent gain enhancement of SNR gap from the theoretical limit compared to Hybrid ARQ-SM. Hybrid ARQ-EM gives better performance although in worse channel condition.

Optimising energy efficiency of LDPC coded chase combining HARQ system

The energy efficiency of the low-density parity check (LDPC) coded chase combining hybrid automatic repeat request (HARQ) system over the additive white Gaussian noise channel is analysed. The energy efficiency can be improved by increasing the maximum transmission number (K) and reducing the transmit power. The asymptotic energy efficiency corresponding to K = ∞ equals the reciprocal of the threshold signal-to-noise ratio of the forward error correction code, which does not depend on the falling speed of the word error ratio. When the retransmission number is relatively small, optimising equal transmit power and variable transmit power can improve the energy efficiency by up to 10 and 18% respectively, compared with minimum equal power transmission.

CRC-Free Hybrid ARQ System Using Turbo Product Codes

This paper presents a hybrid automatic repeat request (HARQ) system using turbo product codes (TPC). The inherent word-error detection capability of TPC is exploited to replace the conventional cyclic redundancy check (CRC) used for packet error detection in conventional HARQ systems. Therefore, TPC are used for joint bit error correction and packet error detection. Consequently, the HARQ system efficiency is improved by increasing the system throughput when short packets are transmitted or by reducing the computational complexity/delay when the packets transmitted are long. Monte Carlo simulation results reveal that the CRC-free TPC-HARQ system consistently provides equivalent or higher throughput than CRC-based HARQ systems. Moreover, numerical results show that TPC self-detection has lower computational complexity than CRC detection, particularly for TPCs with high code rates. In particular scenarios, the relative complexity of the self-detection approach with respect to popular CRC techniques is about 0.3%.

Impact of outdated channel state information on energy efficiency of co‐operative hybrid automatic repeat reQuest in wireless sensor networks

Co-operative communication has been shown to significantly improve energy efficiency in wireless sensor networks. The outdated channel state information (CSI) problem will result in severe performance degradation of co-operative communication systems including energy efficiency. In this study, the authors analyse the impact of outdated CSI on energy efficiency of amplify-and-forward co-operative hybrid automatic repeat reQuest system. The authors derive the expression of the average energy consumption per bit of data transmission under outdated CSI. Numerical results show the deteriorating effects of outdated CSI on the performance of energy efficiency and transmission reliability in co-operative communication system. It is also shown that energy efficiency can be improved by error correcting codes mechanism when end-to-end signal-to-noise ratio at the destination node is within a certain range.

An Accurate Approximation of the Exponential Integral Function Using a Sum of Exponentials

This paper proposes a novel approximation for the exponential integral function, E1[x], using a sum of exponential functions. This approximation facilitates studying the error probability of a number of communication techniques in the presence of Co-Channel Interference (CCI). These include Hybrid Automatic Repeat Request (HARQ) with soft combining, selection relaying, incremental relaying, and opportunistic incremental relaying, just to name a few. To illustrate the usefulness and accuracy of the proposed approximation, we study the error probability of a Chase combining HARQ system operating in the presence of an unknown source of CCI where we derive an accurate closed form expression for the Moment Generating Function (MGF) of the resultant Signal to Interference plus Noise Ratio (SINR). The accuracy of the derived result is verified using computer simulation.

Performance Analysis for Superposition Modulated Cooperative Relay HARQ Networks

In this paper, a two-user superposition modulated cooperative relay hybrid automatic repeat request (HARQ) system is proposed. Two mobile station (MS) uplink communications to the base station (BS) with cooperative assistance of a relay station (RS) are considered. The RS is assumed to be able to perfectly monitor and decode the two MS-to-BS transmitted packets and assist the two MSs by immediately transmitting a cooperative superposition modulated packet that combines the two MS generated packets in the analog domain. The BS is assumed to have perfect channel statistical information and can feed back the appropriate superposition weighting factor to the RS regularly. The HARQ retransmissions, if needed, are then jointly performed by the RS for both MSs instead of separately for each MS. The superposition of the modulated packets is repeatedly retransmitted by the RS to the BS if needed. With the foregoing setting, we derive an information-theoretic achievable rate region and an approximation of the system outage probability. Based on the high SNR behaviors of the approximated system outage probability, we obtain the superposition weighting factor using a simple and efficient searching algorithm. We also analytically derive the HARQ system throughput as the performance metric for comparison. Compared with the traditional relaying HARQ system, our proposed scheme exhibits more than 30% gain in terms of system throughput, depending on the fading statistics of the RS-to-BS and MS-to-BS channels.

New stopping criteria for iterative decoding of LDPC codes in H‐ARQ systems

SUMMARYUnder severely unreliable channel, decoding of error‐correcting codes frequently fails, which requires a lot of computational complexity, especially, in the iterative decoding algorithm. In hybrid automatic repeat request systems, most of computation power is wasted on failed decoding if a codeword is retransmitted many times. Therefore, early stopping of iterative decoding needs to be adopted. In this paper, we propose a new stopping algorithm of iterative belief propagation decoding for low‐density parity‐check codes, which is effective on both high and low signal‐to‐noise ratio ranges and scalable to variable code rate and length. The proposed stopping algorithm combines several good stopping criteria. Each criterion is extremely simple and will not be a burden to the overall system. With the proposed stopping algorithm, it is shown via numerical analysis that the decoding complexity of hybrid automatic repeat request system with adaptive modulation and coding scheme can be fairly reduced. Copyright © 2012 John Wiley & Sons, Ltd.

Hybrid ARQ Protocol for Multi-Antenna Multicasting Using a Common Feedback Channel

Wireless multicasting (also called common information broadcasting) is a technique where a common information message is transmitted to multiple users. This is typically accomplished by having the basestation broadcast out a signal representing this message. In this paper, we consider a multicasting scheme where the basestation transmits the multicasting signal without any a-priori knowledge of the users' channel state information. In this set-up, a hybrid automatic repeat request (ARQ) control is employed to improve the reliability of multicasting communication. In most hybrid ARQ set-ups, each user is usually allocated a dedicated feedback channel to tell the basestation if the previously transmitted signal was correctly decoded. However, dedicated feedback channels waste significant uplink resources, especially when the number of users is large. To mitigate this problem, we consider a negative acknowledgement (NACK) based hybrid ARQ control where the failed users are allowed to transmit the NACK signal (which is assumed to be the same for all users) through a common channel while the other users remain silent. We consider the effect of feedback error and multicasting signal decoding error on our hybrid ARQ system performance as the number of users grows large. Specifically, it is shown that the throughput performance of the proposed hybrid ARQ scheme using repetition retransmission is not severely degraded relative to the throughput performance of the noiseless feedback case. In addition, we show that the performance improvement obtained by replacing repetition encoding with incremental redundancy becomes insignificant for the large number of users asymptote. On the other hand, it is shown that the improvement provided by incremental redundancy is significant when some of the users are allowed to fail to decode the message.

Continuous BP Decoding Algorithm for a Low-Density Parity-Check Coded Hybrid ARQ System

A continuous belief propagation (BP) decoding algorithm for a hybrid automatic repeat request (ARQ) system is proposed in this paper. The proposed continuous BP decoding algorithm utilizes the extrinsic information generated in the last iteration of the previous transmission for a continuous progression of the decoding through retransmissions. This allows the continuous BP decoding algorithm to accelerate the decoding convergence for codeword determination, especially when the number of retransmissions is large or a currently combined packet has punctured nodes. Simulation results verify the effectiveness of the proposed continuous BP decoding algorithm.

An Algorithm for Iterative Detection and Decoding MIMO-OFDM HARQ with Antenna Scheduling

In this paper, a multiple-input-multiple-output (MIMO) hybrid-automatic repeat request (HARQ) algorithm with antenna scheduling is proposed. It retransmits the packet using scheduled transmit antennas according to the state of the communication link, instead of retransmitting the packet via the same antennas. As a result, a combination of conventional HARQ systems, viz. chase combining (CC) and incremental redundancy (IR) are used to achieve better performance and lower redundancy. The proposed MIMO-OFDM HARQ system with antenna scheduling is shown to be superior to conventional MIMO HARQ systems, due to its spatial diversity gain.

Improved regular and semi-random rate-compatible low-density parity-check codes with short block lengths

Powerful rate-compatible codes are essential for achieving high throughput in hybrid automatic repeat request (ARQ) systems for networks utilising packet data transmission. The paper focuses on the construction of efficient rate-compatible low-density parity-check (RC-LDPC) codes over a wide range of rates. Two LDPC code families are considered; namely, regular LDPC codes which are known for good performance and low error floor, and semi-random LDPC codes which offer performance similar to regular LDPC codes with the additional property of linear-time encoding. An algorithm for the design of punctured regular RC-LDPC codes that have low error floor is presented. Furthermore, systematic algorithms for the construction of semi-random RC-LDPC codes are proposed based on puncturing and extending. The performance of a type-II hybrid ARQ system employing the proposed RC-LDPC codes is investigated. Compared with existing hybrid ARQ systems based on regular LDPC codes, the proposed ARQ system based on semi-random LDPC codes offers the advantages of linear-time encoding and higher throughput.

Optimum subpacket transmission for hybrid ARQ systems

Hybrid automatic-repeat-request (ARQ) is a flexible and efficient technique for data transmissions. In hybrid ARQ, subpacket schemes are more attractive for systems with burst errors than complete packet schemes. Although subpacket schemes were proposed in ARQ systems, optimum subpacket transmission is more effective to maximize throughput in a dynamic channel. Since convolutional codes have properties of burst errors in decoding, the optimum subpacket can be applied to convolutional codes. This paper investigates the performance of subpacket transmission for convolutionally coded systems. An efficient method is proposed to estimate the optimum number of subpackets, and adaptive subpacket schemes, i.e., schemes that enable a system to employ different optimum numbers of subpackets under various conditions, are suggested to achieve the maximum throughput of the system. Numerical and simulation results show that the adaptive subpacket scheme is very effective for the convolutionally coded hybrid ARQ system, and it can provide higher throughput, smaller delay,and lower dropping rate than complete packet schemes. Moreover, the adaptive subpacket scheme can be flexibly used with packet combining techniques to further improve the system throughput.

Performance evaluations of hybrid automatic repeat request schemes for a data communication system

AbstractIt is generally impossible to avoid occurrences of errors of the data transmission because of the disturbing factors such as disconnections, noises or distortions in a communication line. Therefore, the error‐control procedure is indispensable to trnnsmit high‐quality data and its various techinques have been considered from the viewpoints of high reliability data transmission. the main techniques in the error‐correcting strategies are classified into the following three categories: (i) forward‐error‐correction (FEC) scheme; (ii) automatic‐repeat‐request (ARQ) scheme; and (iii) hybrid ARQ scheme. the hybrid ARQ scheme is the system combined FEC scheme with ARQ scheme. This aims to reduce the frequency of retransmissions as much as possible and to gain a constant data throughput, even in a worse communication environment, by coding error patterns that would be expected to occur frequently. However, when the first data of transmission has failed, the hybrid ARQ is removed to the ARQ policy with the same FEC, i.e., its data throughput decreases because of bit increments, such as codes to correct errors in the data transmission. This is called type‐I hybrid ARQ and its modified systems, which are called type‐II hybrid ARQ, have been studied and proposed by many authors. This paper suggests a new type‐II hybrid ARQ system from the viewpoint of improving the data throughput and derives the mean time to success of the data transmission. Then, the mean times of the system are compared analytically with those of the usual ARQ and the type‐I hybrid ARQ, and an evaluation is done.

New parity retransmission system using product codes

The type-II hybrid automatic repeat request (ARQ) system is an adaptive error control system and has been given considerable attention in the recent years. The main feature of this system is the application of a rate 1/2 block or convolutional error correction code and parity retransmission. The author presents a new parity retransmission system using simple product codes. The throughput efficiency of the proposed system is analysed for the binary symmetric channel (BSC). Numerical results indicate that the proposed system outperforms the type-II hybrid ARQ system.