Automatic Retransmission Request Research Articles

Energy efficiency in ARQ-based multi-hop systems and the tradeoff with throughput

The minimum energy per bit (EPB) as the energy efficiency (EE) metric in an automatic retransmission request (ARQ) based multi-hop system is analyzed under power and throughput constraints. Two ARQ protocols including type-I (ARQ-I) and repetition redundancy (ARQ-RR) are considered and expressions for the optimal power allocation (PA) are obtained. Using the obtained optimal powers, the EE-throughput tradeoff (EETT) is analyzed and the EETT closed-form expressions for both ARQ protocols and in arbitrary average channel gain values are obtained. It is shown that how different throughput requirements, especially the high levels, affect the EE performance. Additionally, asymptotic analysis is made in the feasible high throughput values and lower and upper EETT bounds are derived for ARQ-I protocol. To evaluate the EE a distributed PA scenario, as a benchmark, is presented and the energy saving-gain obtained from the optimal PA in comparison with the distributed PA for ARQ-I and ARQ-RR protocols is discussed in different throughput values and node locations.

Modeling and Performance Analysis of ECS-HTCARQ Protocol in Interference Scenario

To extend the lifetime of energy-constrained wireless networks, this paper proposes a three-node model of the wireless-powered cooperative communication network (WPCCN). The model consists of an energy-constrained source node, an energy-sufficient relay node, and a destination node and considers two different cochannel interference (CCI) sources at the relay and destination nodes. To ensure the reliability of data transmission, we introduce the cooperative automatic retransmission request (CARQ) protocol, propose the energy-constrained source that harvests and cooperates automatic retransmission request (ECS-HTCARQ) protocol in interference scenario, derive a closed-form expression for the outage probability under Rayleigh fading channels, and establish a discrete-time Markov chain (DTMC) model to analyze the system throughput. The relationship between parameters such as the energy harvesting time allocation factor and energy harvesting efficiency on the outage probability and the system throughput is obtained. Numerical results show that the difference in system throughput is small as the increasing number of transmissions at a high signal-to-interference ratio (SIR), but there is a significant reduction in the outage probability. Finally, the optimal value of the energy harvesting time allocation factor is given under this model.

Common Message Acknowledgments: Massive ARQ Protocols for Wireless Access

Massive random access plays a central role in supporting the Internet of Things (IoT), where a subset of a large population of users simultaneously transmit small packets to a central base station. While there has been much research on the design of protocols for massive access in the uplink, the problem of providing message acknowledgments back to the users has been somewhat neglected. Reliable communication needs to rely on two-way communication for acknowledgement and retransmission. Nevertheless, because of the many possible subsets of active users, providing acknowledgments requires a significant amount of bits. Motivated by this, we define the problem of massive ARQ (Automatic Retransmission reQuest) protocol and introduce efficient methods for joint encoding of multiple acknowledgements in the downlink. The key idea towards reducing the number of bits used for massive acknowledgments is to allow for a small fraction of false positive acknowledgments. We analyze the implications of this approach and the impact of acknowledgment errors in scenarios with massive random access. Finally, we show that these savings can lead to a significant increase in the reliability when retransmissions are allowed since it allows the acknowledgment message to be transmitted more reliably using a much lower rate.

HARQ Optimization for PDCP Duplication-Based 5G URLLC Dual Connectivity

Packet duplication (PD) with dual connectivity (DC) was newly introduced in the 5G New Radio (NR) specifications to meet the stringent ultra reliable low latency communication (URLLC) requirements. PD technology uses duplicated packets in the packet data convergence protocol (PDCP) layer that are transmitted via two different access nodes (ANs) to the user equipment (UE) in order to enhance the reliability performance. However, PD can result in unnecessary retransmissions in the lower layers since the hybrid automatic retransmission request (HARQ) operation is unaware of the transmission success achieved through the alternate DC link to the UE. To overcome this issue, in this paper, a novel duplication-aware retransmission optimization (DRO) scheme is proposed to reduce the resource usage induced by unnecessary HARQ retransmissions. The proposed DRO scheme can minimize the average channel use while satisfying the URLLC requirements. The proposed DRO scheme derives the optimal HARQ retransmission attempts for different ANs by solving a nonlinear integer programming (NLIP) problem. The performance of the proposed DRO scheme was evaluated using MATLAB simulation and is compared to the existing 5G HARQ support schemes. The simulations results show that the proposed DRO scheme can provide a 14.71% and 15.11% reduced average channel use gain compared to the selective data duplication upon failure (SDUF) scheme and latency-aware dynamic multi-connectivity algorithm (LADMA) scheme, respectively, which are the existing 5G PD schemes that use HARQ.

Spatially Coupled LDPC Codes via Partial Superposition and Their Application to HARQ

This paper proposes a new class of spatially coupled codes, which are constructed by sending codewords of a low-density parity-check block code (LDPC-BC) in a block Markov superposition transmission (BMST) manner, resulting in the BMST-LDPC codes. Different from the conventional spatially coupled LDPC (SC-LDPC) codes, the proposed BMST-LDPC codes can have encoder/decoder implemented using the structure of the corresponding LDPC-BCs. The proposed construction is universal , which is applicable to any existing LDPC-BCs including the 5 G New Radio (5G-NR) LDPC-BCs to obtain extra coding gains. The proposed BMST-LDPC codes are also a special class of BMST codes, which have lower error floors even with an encoding memory of one, inheriting a low decoding latency. Moreover, partial superposition , where a fraction of the coded bits are superimposed onto the following codewords, is introduced to alleviate the decoding error propagation. The construction can be optimized, for random long codes, by a protograph-based extrinsic information transfer (EXIT) chart analysis, or by a one-dimensional search for structured block codes. Furthermore, the BMST-LDPC scheme is integrated with the hybrid automatic retransmission request (HARQ) over the block fading channel, improving the throughput performance. Numerical results are presented to validate our analysis and demonstrate the performance advantage of the BMST-LDPC codes over the LDPC-BCs. They also show that the proposed HARQ scheme can yield a throughput improvement of up to 10% over the conventional HARQ scheme.

Data Transmission Model with Lost Fragments Recovery Based on Application Layer ARQ

Wireless networks in difficult conditions of signal receiving are characterized by a high level of burst data losses, at which a large number of data fragments can be lost in a row. In this case, to recover the lost data, the use of forward error correction methods (FEC) in most cases does not give a sufficient effect. The use of standard data loss recovery methods based on automatic retransmission request (ARQ) at the data link and transport layers of the OSI model can lead to significant delays, which is often unacceptable for real-time streaming services. In such a case, it may be preferable to skip the piece of data rather than delay waiting for the piece to be delivered on retransmissions. The use of ARQ-based techniques on application layer of OSI model for data streaming allows for a more efficient recovery of lost data chunks in wireless networks with a high level of burst losses. The known models of a discrete channel for wireless networks allow for analytically assessing the probability of data loss, however, they do not take into account cases with retransmission of lost data. The study proposes a mathematical model of data transmission in a wireless communication channel based on the Gilbert model, which takes into account the loss recovery by the ARQ method and allows you to calculate the data loss ratio. To check the adequacy of the proposed model, a software was developed that ensures the transmission of data streaming in a wireless communication network with recovery of fragment losses at the application level, and a corresponding experimental study was carried out. It is shown that the mathematical model takes into account the burstiness of transmitted data losses and their recovery by the ARQ method.

A Throughput-Enhanced HARQ Scheme for 5G System via Partial Superposition

In this letter, we propose partial superposition for 5G hybrid automatic retransmission request (HARQ), resulting in a throughput-enhanced HARQ scheme for the 5G system. The novelty of the proposed scheme is to retransmit an erroneous packet by superimposing (XORing) its partial bits onto a fresh packet, costing no extra bandwidth and transmission power. The proposed HARQ schemes can be implemented with the basis of the hardware components of the 5G standard. Numerical results show that the proposed HARQ schemes can yield a throughput improvement up to 10% over the original 5G HARQ scheme.

Performance Analysis and Comparison of HARQ Protocols Based on Outage Probability in Wireless Communication Networks

Hybrid Automatic Retransmission reQuest (HARQ) protocol can effectively compensate the signal transmission error caused by complex time-varying channels and multi-path effects of wireless communication networks. This paper analyzes and compares the principle and system performance of three HARQ protocols from the perspective of system outage probability, and the expressions of system throughput and energy efficiency are derived by establishing a one-dimensional Discrete Time Markov Chain (DTMC) and calculating the steady-state distribution. MATLAB numerical simulations are applied to evaluate and compare the performance superiority among three HARQ Protocols.

Reduction of Power Consumption using Joint Low Power Code with Crosstalk Avoidance Code in Case of Crosstalk and Random Burst Errors

When technology is scaling down, reliability and power issues are arise in the intercommunication of System on Chip (SoC). The intercommunication links are suffers with various noise sources like crosstalk, temperature variation and voltage deflection which lead to communication link failure. To get reliable system, the strong error detection and correction codes are required. In this proposed work, Crosstalk avoidance code detects and corrects of one bit error, two bit error and some of three bit errors. The Hybrid Automatic Re-transmission Request is also used when the CAC detects the burst error of three. Apart from this, the Low Power Codes are used to get low power consumption using Bus Invert (BI) technique in proposed work. The LPC code reduces the power consumption of interconnection wires using reducing switching activity. The performance of proposed work evaluated in Xilinx 14.7 in Vertex-6 Field Programmable Gated Array (FPGA) device. The proposed work is calculated of power consumption of codec module and interconnection wire, delay of CAC and LPC code and link swing voltage. This work provides 11.7% improvement in power consumption and presents high reliability than JTEC. The energy dissipation of wires in the proposed work is decreased 23.5% than un-coded schemes.

On Channel-Aware Secure HARQ-IR

In this paper, we study secure hybrid automatic retransmission request (HARQ) over block-fading channels when the channel from a legitimate transmitter (i.e., Alice) to an eavesdropper (i.e., Eve) is less noisy than that to a legitimate receiver (i.e., Bob). In order to have a positive secrecy rate, we exploit the notion of the channel reciprocity in time division duplex mode, where the shared channel state information between Alice and Bob is used as a secret key. The resulting HARQ scheme is referred to as channel-aware secure HARQ (CAS-HARQ) in this paper. In this scheme, in order to keep Eve ignorant of the confidential message from Alice to Bob, deliberative transmissions of random message blocks are considered when the channel to Bob is weak. We derive closed-form expressions for bounds on the probabilities of connection outage and secrecy outage to see reliability and security, respectively, of CAS-HARQ. Based on our analysis, we can see that it is possible to have a positive secrecy rate with certain outage probabilities even if the channel to Eve is less noisy than that to Bob.

Information hiding in edges: A high capacity information hiding technique using hybrid edge detection

The multimedia security is becoming more and more important as the data being exchanged on the Internet is increasing exponentially. Though cryptography is one of the methods which is used to secure the data during transit, but the camouflaged appearance of the scrambled data alerts the adversary about some critical information being shared. In such a scenario, steganography has been used as an alternate solution to secure the secret information. In this paper a color image steganographic algorithm based on hybrid edge detection is proposed. The color image is partitioned into constituent Red (R), Green (G) and Blue (B) planes. Hybrid edge detection is used for finding the edge and non-edge pixels of Green and Blue planes of cover image. The Green and Blue planes are used for hiding the data while Red plane holds the pixel status (whether edge or non-edge) of these planes. The RC4 encryption algorithm is used to encrypt secret message before embedding it in the cover image to enhance security of the secret data. A fragile watermark/logo (whose size is less than 1% of total secret data) has been embedded, besides secret data in the cover image, to facilitate content authentication and early tamper detection. At the receiver, firstly logo is extracted. If it is same as one embedded at transmitter, indicating that secret data has not been altered during transit, secret data is extracted. Otherwise (if extracted logo is not same as used at input) the receiver does not waste critical time to extract compromised data but sends an automatic retransmission request. Experimental investigations reveal that the proposed scheme is capable of providing high quality of stego-images for a fairly high pay load. A comparison of the proposed technique with some state of art schemes substantiates the above arguments.

Optimal Cognitive Access and Packet Selection Under a Primary ARQ Process via Chain Decoding

This paper introduces a novel technique that enables access by a cognitive secondary user (SU) to a spectrum occupied by an incumbent primary user (PU) that employs Type-I hybrid automatic retransmission request (ARQ). The technique allows the SU to perform selective retransmissions of SU data packets, whose transmission previously failed. The temporal redundancy introduced by the PU ARQ protocol and by the selective retransmission process of the SU can be exploited by the SU receiver to perform interference cancellation (IC) over multiple transmission slots, thus creating a “clean” channel for the decoding of the concurrent SU or PU packets. The chain decoding (CD) technique is initiated by a successful decoding operation of an SU or a PU packet and proceeds by an iterative application of IC as previously buffered packets become decodable and their interference can be removed, thus making it possible to recover the concurrent data packets, and so on, until no more packets are decodable. Based on this scheme, an optimal policy is designed that maximizes the SU throughput under a constraint on the average long-term PU performance. The optimality of the CD protocol is proved, which determines which packet the SU should send at any given time, based on four basic rules. Moreover, a decoupling principle is proved, which establishes the optimality of decoupling the secondary access strategy from the CD protocol. Specifically, first , the SU access policy, optimized via dynamic programming, specifies whether the SU should access the channel or remain idle, based on a compact state representation of the protocol, and second , the CD protocol embeds four basic rules that are used to select the packet transmitted by the SU. It is shown numerically that CD outperforms by up to 35% other schemes considered in the literature, which do not employ retransmissions at the SU pair and thus do not exploit the full potentiality of IC.

OM2DNC: Opportunistic Max2-Degree Network Coding for wireless data broadcasting

In wireless broadcasting systems, multiple retransmissions are commonly employed to guarantee the correct reception of each packet. The traditional hybrid automatic retransmission request protocol retransmits one packet per slot. Hence, a large amount of retransmissions is required to correctly receive all the packets, which leads to low spectrum efficiency. In this paper, we propose an Opportunistic Max2-Degree Network Coding (OM2DNC) based wireless broadcasting (WBC) protocol. Specifically, to reduce the overall number of retransmissions, lost packets of different user equipments (UEs) are combined by performing Max-Degree network coding (NC) at the access node. Then, NC combined packets are broadcasted by utilizing the Max-Degree based opportunistic retransmission protocol. At each UE, the lost packet can be recovered by using the proposed joint network recursive systematic convolution decoder. Theoretical analyses and simulation results show that the average number of transmissions performance of the proposed OM2DNC based WBC protocol outperforms that of the traditional NC based WBC protocols.

Improved MLWDF scheduler for LTE downlink transmission

ABSTRACTIn long-term evolution (LTE) downlink transmission, modified least weighted delay first (MLWDF) scheduler is a quality of service (QoS) aware scheduling scheme for real-time (RT) services. Nevertheless, MLWDF performs below optimal among the trade-off between strict delay and loss restraints of RT and non-RT traffic flows, respectively. This is further worsened with the implementation of hybrid automatic retransmission request (HARQ). As these restraints grow unabated with increasing number of user demands, the performance of MLWDF further reduces. In order to ameliorate this situation, there is a need to directly incorporate the variations in user demands and HARQ implementation as parameters to the MLWDF scheduler. In this work, an improvement to the MLWDF scheduler is proposed. The improvement entails adding two novel parameters that characterise user demand and HARQ implementation. The scheduler was tested using varying three classes of service in QoS class identifiers (QCIs) table standardised by Third Generation Partnership Project for LTE network to characterise different services. It was also tested on the basis of packet prioritisation. The proposed scheduler was simulated with LTE-SIM simulator and compared with the MLWDF and proportional fairness schedulers. In terms of delay, throughput and packet loss ratio; the proposed scheduler increased overall system performance.

Rate Adaptation for Incremental Redundancy Secure HARQ

This paper studies secure communication based on incremental redundancy (INR) secure hybrid automatic retransmission request (HARQ) protocol over block-fading wiretap channels. The transmitter has no instantaneous channel state information (CSI) available from either main channel or the eavesdropper channel, hence the coding rates cannot be adapted to instantaneous channel conditions. We investigate the outage performance for two schemes of INR secure HARQ protocols: case 1) when there exists two reliable multibit feedback channels from both legitimate receiver and eavesdropper to the transmitter carrying a function of outdated CSI, and case 2) when there is a multibit feedback channel only from legitimate receiver. In both cases, we demonstrate that using the information carried via multibit feedback channels, the transmitter can adapt the coding rates in order to achieve a better secrecy throughput using a smaller number of transmissions comparing to the ACK/NACK feedback channel model. For some parameters, our rate adaptation protocol achieves a strictly positive secrecy throughput whereas it is equal to zero for the protocol with ACK/NACK feedback. We show that for some set of parameters, the loss of secrecy throughput between case 1 and case 2 is very small compared to the gain provided by both protocols.

Group communication over LTE: a radio access perspective

Long Term Evolution (LTE), which has its root on commercial mobile communications, recently becomes an influential solution to future public safety communications. To verify the feasibility of LTE for public safety, it is essential to investigate whether an LTE system optimized for one-to-one communications is capable of providing group communication, which is one of the most important service concepts in public safety. In general, a number of first responders for public safety need to form a group for communicating with each other or sharing the common data for collaboration on their mission. In this article, we analyze how the current LTE system can support group communication in a radio access aspect. Based on the requirements for group communication, we validate whether each LTE-enabled radio access method can efficiently support group communication. In addition, we propose a new multicast transmission scheme, termed index-coded Hybrid Automatic Retransmission reQuest (HARQ). By applying the index coding concept to HARQ operations, we show that the LTE system can provide group communication more sophisticatedly in terms of radio resource efficiency and scalability. We finally evaluate the performance of LTE-enabled group communication using several radio access methods and show how the proposed transmission scheme brings the performance enhancement via system level simulations.

Energy-Efficient Relay Selection of Cooperative HARQ based on the Number of Transmissions over Rayleigh-Fading Channels

Cooperative hybrid automatic retransmission request (C-HARQ) is a simple and effective method for wireless communication. Since its performance largely depends on the selection of a relevant relay, the design of an appropriate relay selection scheme is very important. Although various works have been performed on this topic, most of them did not take into account both the “ not memoryless ” and multiple retransmission characteristics of C-HARQ, resulting in the loss of achievable performance. In this paper, we propose a novel cooperative relay selection scheme in a distributed manner called transmission number relaying (TNR) to simultaneously reduce the outage probability and increase the energy efficiency by utilizing the features of C-HARQ. The TNR scheme determines a single relay based on the estimated number of transmissions, which is calculated from the channel condition. Using these numbers instead of just the channel condition improves the outage probability and reduces the total consumed energy. The exact probability of the number of transmissions at each relay and the outage probability are analyzed, and the numerical results show that the proposed scheme significantly improves the outage probability and reduces the total consumed energy. In addition, when the number of available relays is small, the proposed scheme achieves high energy efficiency.

NTC-HARQ: Network–Turbo-Coding Based HARQ Protocol for Wireless Broadcasting System

Wireless broadcasting systems employ multiple retransmissions to guarantee the correct reception of each packet. The traditional hybrid automatic retransmission request (HARQ) protocol retransmits one packet per slot. Hence, a large amount of retransmissions is required to correctly receive all the packets, which leads to low spectrum efficiency. In this paper, we propose a Network-coding-and-distributed-Turbo-Coding-based type-III HARQ (NTC-HARQ) protocol, including an xoring Network Coding Combined (XNCC) retransmission strategy at the access node (AN) and a joint network-turbo decoding (JNTD) strategy at the user equipment (UE). Specifically, to reduce the overall number of retransmissions, lost packets of different UEs are network coding (NC) combined at the AN by utilizing the XNCC strategy. The soft information of the lost packet at each UE can be recovered from the received network-coded retransmission packet by using the proposed xoring soft network decoder. The recovered soft information of the UE's lost packet is combined with the local undecodable soft information of the same packet to form a distributed turbo code. A Chase-combining-based distributed turbo decoder is proposed to perform turbo decoding, which introduces coding gain and improves packet-error-rate (PER) performance. Theoretical analyses and simulation results show that the average-number-of-transmission performance of the proposed NTC-HARQ protocol outperforms that of the XNCC-based type-I HARQ protocol, the traditional NC-based HARQ protocol, and the JNTD-based protocol.

A Novel Cooperative ARQ Method for Wireless Sensor Networks

In wireless sensor networks, cooperative communication can combat the effects of channel fading by exploiting diversity gain achieved via cooperation communication among the relay nodes. A cooperative automatic retransmission request (ARQ) protocol based on two-relay node selection was proposed in this paper. A novel discrete time Markov chain model in order to analyze the throughput and energy efficiency was built, and system throughput and energy efficiency performance of proposed protocol and traditional ARQ protocol were studied based on such model. The numerical results reveal that the throughput and energy efficiency of the proposed protocol could perform better when compared with the traditional ARQ protocol.

Link Layer Correction Techniques and Impact on TCP’s Performance in IEEE 802.11 Wireless Networks

TCP performance degrades when end-to-end connections extend over wireless links which are characterized by high Bit Error Rate and intermittent connectivity. Such degradation is mainly accounted for TCP’s unnecessary congestion control actions while attempting TCP loss recovery. Several independent link loss recovery approaches are proposed by researchers to reduce number of losses visible at TCP. In this paper we first presented a survey of loss mitigation techniques at wireless link layer. Secondly performance evaluation for TCP through Type 0 Automatic Retransmission Request mechanism in erroneous Wireless LAN is presented. In particular, simulations are performed taking into account the wireless errors introduced over IEEE 802.11 link using a well-established 2-State Markov model. TCP performance is evaluated under different settings for maximum link retransmissions allowed for each frame. Simulation results show that, link retransmission improves TCP performance by reducing losses perceived at TCP sender. However, such improvement is often associated with adverse effect on other TCP parameters that may cost a lot in return under extreme network conditions. In this paper an attempt is made to observe impact of link retransmissions on the performance of multiple TCP flows competing with each other. The analysis presented in this paper signifies the scope for maximizing TCP’s throughput at the least possible cost.