Improved Cognitive Networking Through Full Duplex Cooperative ARQ and HARQ

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

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%.

In the fifth generation (5G) wireless communication system, the non‐orthogonal multiple access (NOMA) scheme has recently been proposed as a possible candidate for improving spectral efficiency. We look at power‐domain NOMA in this study, in which, multiple simultaneous transmissions are allowed at the same channel with different transmission powers. To achieve reliable transmissions in NOMA, the hybrid automatic repeat request (HARQ) scheme can be integrated into NOMA. The performance of a downlink NOMA system using the Type I HARQ method is investigated in this research. This type of HARQ does not entail expensive device which is considered one of the requirements for a massive 5G‐based Internet of Things network. Unfortunately, in the literature, it has been shown that deriving closed‐form expressions for the outage probabilities of HARQ‐aided NOMA systems is intractable due to the incorporation of multiple fractional random variables. Consequently, in this article, we follow a simple yet efficient methodology to study our considered HARQ‐aided NOMA system. The HARQ‐assisted NOMA system on the downlink is modeled as an absorbing discrete‐time Markov chain (DTMC). Thereafter, under perfect and imperfect channel estimation, we use this model to examine system performance in terms of outage probability and estimated number of retransmissions. Interestingly, we demonstrate that our DTMC‐based analysis is straightforward, repeatable, and accurate. Moreover, in this article, we propose a cooperative HARQ (CHARQ) scheme for the downlink NOMA system. According to CHARQ, the users cooperate with the base station in the retransmission process that will result in improving the performance of NOMA. Monte Carlo simulations have been conducted to not only verify the accuracy of our DTMC‐based analysis, but also manifest the superiority of CHARQ over HARQ.

A new hybrid automatic repeat request (ARQ) scheme that utilises reliability estimates generated by soft-input, soft-output (SISO) decoders is proposed. The proposed ARQ scheme transmits additional information for the unreliable bits, and this information is used to perform additional decoding. Results are presented that show this ARQ technique can provide performance close to the channel capacity.

Cooperative Hybrid ARQ in Solar Powered Wireless Sensor Networks

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.

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.

There are two kinds of technique used for error control: FEC (forward error correction) and ARQ (automatic repeat request). Combining these two schemes, which is called HARQ (hybrid ARQ), makes it possible to increase the channel throughput. The error of the channel quality estimate that is used to select the MCS (modulation coding scheme) in type I HARQ can be a serious problem in scenarios when the mobile station moves at high speeds. Furthermore, in a system dominated by packet services, the interference level may be bursty, and thus it is difficult to predict the interference level. Therefore, the type II HARQ scheme is a more robust solution compared with type I HARQ. In order to improve channel throughput while at the same time satisfying quality of service (QoS) under various channel conditions, an efficient hybrid ARQ type II scheme is proposed. The optimum redundancy size for every transmission is calculated to maximize the throughput using QoS parameters, the performance of LDPC code and channel conditions. The proposed scheme, together with such benefits as QoS support, provides a way of achieving higher throughput in wireless communication systems.

We propose a new data link control protocol for wireless ATM networks. This new protocol can support both real time and non-real-time services by adopting different error control mechanisms. For real-time traffic, only forward error control (FEC) is used for error correction. For non-real-time traffic, a hybrid automatic repeat request (ARQ) scheme is adopted to reduce the cell loss ratio to a minimum level. In both the FEC and hybrid ARQ schemes, the coding rate is adapted to the channel conditions. When the signal-to-noise ratio (SNR) is high, the coding rate may be higher; while when the channel is bad, the coding rate is adjusted to be lower. The automatic coding rate adaptiveness guarantees the high utilization of the scarce wireless channel resources.

Sequential decoding is analyzed in conjunction with an efficient incremental redundancy automatic repeat request (ARQ) scheme using punctured convolutional coding. With the incremental redundancy ARQ scheme, whenever the decoding time of a given data packet exceeds some predetermined value T/sub max/, decoding of that data packet is stopped and incremental redundancy bits are provided by the transmitter, a few bits at a time, as needed. It is shown that the incremental redundancy ARQ scheme provides throughput improvement over the partial retransmission code combining ARQ scheme. The advantage of the incremental redundancy ARQ scheme is that the throughput increases as the starting coding rate increases over all ranges of signal-to-noise ratios. >

User scheduling and multiuser multi-antenna (MU-MIMO) transmission are at the\ncore of high rate data-oriented downlink schemes of the next-generation of\ncellular systems (e.g., LTE-Advanced). Scheduling selects groups of users\naccording to their channels vector directions and SINR levels. However, when\nscheduling is applied independently in each cell, the inter-cell interference\n(ICI) power at each user receiver is not known in advance since it changes at\neach new scheduling slot depending on the scheduling decisions of all\ninterfering base stations. In order to cope with this uncertainty, we consider\nthe joint operation of scheduling, MU-MIMO beamforming and Automatic Repeat\nreQuest (ARQ). We develop a game-theoretic framework for this problem and build\non stochastic optimization techniques in order to find optimal scheduling and\nARQ schemes. Particularizing our framework to the case of "outage service\nrates", we obtain a scheme based on adaptive variable-rate coding at the\nphysical layer, combined with ARQ at the Logical Link Control (ARQ-LLC). Then,\nwe present a novel scheme based on incremental redundancy Hybrid ARQ (HARQ)\nthat is able to achieve a throughput performance arbitrarily close to the\n"genie-aided service rates", with no need for a genie that provides\nnon-causally the ICI power levels. The novel HARQ scheme is both easier to\nimplement and superior in performance with respect to the conventional\ncombination of adaptive variable-rate coding and ARQ-LLC.\n

A new hybrid automatic repeat request (HARQ) scheme is proposed for multiple-input multiple-output (MIMO) systems when the acknowledgment (ACK) bundling is applied for packet retransmissions. In the proposed HARQ scheme, both Chase combining (CC) and incremental redundancy (IR) are utilised for a retransmission request, and the proposed HARQ scheme is called a multiple retransmission strategy-based HARQ (MRS-HARQ). During the reception process of the MRS-HARQ, IR packets obtain signal-to-noise ratio gains using the extended detection with CC packets and the improved IR packets are utilised to eliminate the interference from the CC packets. This sequential reliability improvement allows the MRS-HARQ to decrease the occurrence of the deficient transmissions, and the proposed MRS-HARQ can achieve an improved error performance and throughput over the conventional CC-based and IR-based HARQ schemes with the ACK bundling.

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.

We develop a general model based on random coding bounds to explain and predict the coding performance of various type-I and type-II hybrid automatic repeat request (HARQ) schemes based on the bit-interleaved coded modulation (BICM) in 3GPP HSPA. We explore how the intrinsic properties of BICM interact with various transmitter-side (e.g., whether to use the same bit mapping for retransmission) and receiver-side HARQ options (e.g., bit vs. symbol level processing and Log-MAP vs. Log-Max demodulation). The accuracy of the theoretical model is verified with extensive link simulations. The performance model can be incorporated into radio resource management algorithms for efficient wireless network operations. In a companion paper, the unified analytical model is further applied to investigate performance of LTE HARQ operations, which consist of varying mixture of type-I/II and bit remapping HARQ features.

This paper presents a neural model for reliable and fault tolerant transmission in Wireless Sensor Networks based on Bi-directional Associative Memory. The proposed model is an attempt to enhance the performances of both the cooperative and non cooperative Automatic Repeat Request (ARQ) schemes in terms of reliability and fault tolerance. We have also demonstrated the performances of both the schemes with the help of suitable examples.