Type II hybrid ARQ scheme based on QoS and LDPC code

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.

During data exchange in wireless networks, an error in transmission can occur. Corrupted data cannot be further processed without a correction. A technique based on either Automatic Repeat reQuest (ARQ) or Forward Error Correction (FEC) is conventionally used to repair erroneous data in wireless networks. The ARQ is backward mechanism that uses a feedback channel for the confirmation of error-free data delivery or to request a retransmission of corrupted data. This method can increase a network throughput if radio channel conditions are getting worse (Sambale et al., 2008). On the other hand, the ARQ method increases the delay of packets due to the retransmission of former unsuccessfully received packets. The FEC can increase user’s data throughput over the channel with poor quality despite the fact that additional redundant bits are coded together with users’ data at the transmitter side. The method combining both above mentioned methods is called Hybrid ARQ (HARQ). All three error correction mechanisms are implemented on physical and/or Medium Access Control (MAC) layer.

Hybrid ARQ (HARQ) combines Automatic Repeat Request (ARQ) and Forward Error Correction (FEC) to exploit information from erroneous packets after retransmissions. Due to its superior reliability, HARQ became a crucial component of several important 3G and 4G systems. Although the performance advantage is very attractive, implementing HARQ is challenging with emerging high throughput communication systems such as LTE and LTE-A. Specifically, a large amount of data needs to be stored whenever there is a retransmission. Knowing that LTE/LTE-A systems would provide Gbps or hundreds of Mbps, a straightforward implementation would require around 14 Mbit memory as HARQ buffer. With cost and power limited wireless terminals, the available memory size to support HARQ is a strict and challenging constraint. Hence, it is essential to find efficient techniques to minimize the memory footprint for storing erroneous packets with marginal or, preferably, no degradation. In the context of LTE systems, we propose a novel method to reduce the memory footprint for HARQ systems. This method has been evaluated with a fully fledged practical LTE simulation chain with MIMO transmissions. Compared to state-of-the-art solutions, we show a promising memory compression factor that is close to 5, whereas communication performance degradation is marginal.

It 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.

Various Automatic Repeat Request (ARQ) schemes have been used to combat errors that befall information transmitted in digital communication systems. Such schemes include simple ARQ, mixed mode ARQ and Hybrid ARQ (HARQ). In this study we introduce extended ARQ schemes and derive expressions for their throughput performance. We then compare their performance with mixed mode ARQ schemes where it is shown that extended ARQ schemes outperform the mixed mode ARQ schemes. We also show how the parameters for the schemes can be chosen to maximize performance.Keywords: ARQ, extended ARQ, HARQ, mixed mode ARQ, throughput

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A cooperative automatic repeat request (ARQ) scheme is proposed for cognitive radio networks with full duplex capability. Its performance is studied for ARQ and hybrid ARQ (HARQ) modes, in terms of data link layer packet error rate (PER) and the primary and secondary throughputs. It is shown that activity of the secondary network during primary’s retransmission does not affect primary’s performance in ARQ mode, and would even improve it in HARQ mode.

In this paper, we propose a modified MAC protocol supporting real-time video traffic over the IEEE 802.11 WLAN. Investigating H.26L real-time video transmission over wireless IEEE 802.11b LANs, we present a novel hybrid automatic repeat request (ARQ) algorithm that efficiently combines forward error control (EEC) coding with the ARQ protocol based on multiple transmission stages. The scheme includes: (1) multiple transmission stages with corresponding ARQ feedback information that determines how many transmission stages should be activated; (2) conditional frame skipping algorithm based on accumulated feedback information. Through analysis and simulation, we show that multiple-stages based Hybrid ARQ scheme has high error recovery rate for real-time video frames. In case of severe unreliable channel which causes losing a lot of IP packets, at the cost of little end-to-end delay's increase, we obtain a peak signal-to-noise ratio improvement up to about 10dB compared to the hybrid ARQ proposed in I A. Majumdar et al. (2002).

In this paper, we propose a data-driven joint modulator and demodulator based on meta-learning for hybrid automatic repeat request (HARQ) schemes, which include Type-I HARQ, HARQ with chase combining (HARQ-CC), and HARQ with incremental redundancy (HARQ-IR). Data-driven deep learning (DL) techniques have proven particularly effective for enabling wireless systems to adapt to complex scenarios with unknown or imperfect channel conditions that are difficult to characterize analytically. Most existing DL approaches to realize data-driven communication frameworks are based on joint source-channel coding (JSCC). However, the difficulty in detecting transmission errors makes JSCC unsuitable for HARQ systems. To address this limitation, we propose a novel architecture that combines classical channel coding with DLbased modulation and demodulation. Specifically, we employ an autoencoder to implement both the modulator and demodulator. To quickly adapt to time-varying fading channels, the ModelAgnostic Meta-Learning (MAML) algorithm is leveraged to accelerate the convergence of the model as well as enhance the reliability of HARQ. The MAML framework is divided into two phases, including the pre-training phase to acquire shared initialization parameters across various channel conditions and the fine-tuning phase to rapidly adapt to specific channel states. Simulation results demonstrate that the proposed architecture offers dramatic improvements in convergence speed and generalization capabilities, and meanwhile boosts the reliability of HARQ schemes.

Since wireless channel is always band-limited with multi-path fading and highly burst errors, flexible error control is needed in wireless asynchronous transfer mode (WATM) networks. This paper proposes a hybrid automatic repeat request (HARQ) architecture which has on-demand quality of services (QoS). By choosing different options in the architecture, we get different error control schemes. In this paper, we investigate the performance of three different error control schemes, namely HARQ, HARQ with different redundancy, and adaptive HARQ with traffic-type-dependent redundancy. The simulation results show that the HARQ with FEC adaptation offers the best performance.

Hybrid automatic repeat request (HARQ) can make efficient and reliable transmission possible for radio communications. However, in the HARQ scheme, packet control information (PCI), such as HARQ block identifiers (HARQ block ids) in selective repeat ARQ (SR-ARQ), are required and the reduction of PCI overhead is an issue. In particular, type-II HARQ handles a large amount of PCI because it includes the HARQ block ids and sub-block ids. The sub-block id identifies the set of parity bits in the HARQ block of the corresponding sub-block, and is used to combine the sub-blocks. This report proposes a method of PCI reduction suitable for type-II HARQ with SR-ARQ. The method can inform the HARQ block id and sub-block id of each HARQ block by sending only the information on how many HARQ blocks are contained in each 1st, 2nd, 3rd, and 4th transmission group. The estimated size of reduced PCI and simulation results of our TDD communication system confirms that the proposed method greatly reduces PCI and improves data throughput compared to a conventional method.

The data transmission fails due to errors which have been generated by disconnections, noises and distortions in a communication line. To protect such failures, the following three schemes of error-control procedures are mainly used : (i) automatic-repeat-request (ARQ), (ii) forward-error-correction (FEC) and (iii) hybrid ARQ which combines FEC with ARQ. This paper proposes two stochastic models of hybrid ARQ policies with retransmission number K and response time T, and derives the mean times to success of data transmission. Comparing the mean times with each other, we discuss analytically which policy is better. These results are also evaluated in numerical examples.

We propose and analyze a scheme for wireless channels, which is a combination of a hybrid type I automatic repeat request (ARQ) scheme and a power ramping. In the hybrid type I ARQ scheme, the same redundancy bits for error correction is transmitted repeatedly when a negative acknowledgment (NAK) is obtained. In addition to the ARQ scheme, the power ramping is considered for more reliable downlink data transmission, in which the transmission power is gradually changed from a small level to large levels when the number of retransmission increases. This is done without any knowledge of the channels at the transmitter. Simulation results show that by applying the combined hybrid ARQ and power ramping scheme with properly selected parameters, it has a throughput advantage of 3-5%.

The IEEE 802.16 Medium Access Control (MAC) protocol supports point-to-multipoint (PtM) and mesh broadband very high peak bit rate wireless applications while delivering Quality of Service (QoS) similar to the one of ATM and DOCSIS. The MAC sub-layer, protocol and service data units are described, as well as the missions, functions, connections, addressing and service flows of the Service Specific Convergence and MAC Common Parts Sub-layers. Then, the headers formats, the MAC sub-header, specific payloads and sub-header ordering are analyzed. IEEE 802.16 MAC connections are described and basic, primary and secondary management connections are presented, as well as details on fragmentation, packing and concatenation. The encryption of MAC Packet Data Units and Automatic Repeat Request (ARQ) area also covered, followed by hybrid ARQ. Scheduling algorithms, QoS classes, aspects of bandwidth allocation and request mechanisms are finally addressed, as well as contention resolution mechanisms and network entry issues.

As the physical transmission rate develops rapidly in the modern IEEE 802.11 WLANs, the efficiency of traditional stop-and-wait(SAW) automatic repeat request (ARQ) mechanism degrades dramatically. Negative acknowledgement (NAK)-based ARQ mechanism is a proper candidate to improve the link layer performance. In this paper we propose a discrete-time Markov chain (DTMC) model to analyze the performance of the IEEE 802.11 WLAN system with NAK-based ARQ mechanism. Then the analytical performance is compared with that of SAW ARQ. We find that NAK-based ARQ outperforms SAW ARQ in terms of system throughput while performs poorly in terms of transmission delay. Then a hybrid ARQ scheme is proposed, through which the system can leverage between the two mechanisms to achieve better quality of service(QoS) guarantee. The simulation result validates the correctness of the proposed model and scheme.