Average Number Of Retransmissions Research Articles

An Adaptive Hybrid Automatic Repeat Request (A-HARQ) Scheme Based on Reinforcement Learning

V2X communication is susceptible to attenuation and fading caused by external interference. This interference often leads to bit error and poor quality and stability of the wireless link, and it can easily disrupt packet transmission. In order to enhance communication reliability, the 3rd Generation Partnership Project (3GPP) introduced the Hybrid Automatic Repeat Request (HARQ) technology for both 4G and 5G systems. Nevertheless, it can be improved for poor communication conditions (e.g., heavy traffic flow, long-distance transmission), especially in advanced or cooperative driving scenarios. In this paper, we propose an Adaptive Hybrid Automatic Repeat Request (A-HARQ) scheme that can reduce the average block error rate, the average number of retransmissions, and the round-trip time (RTT). It adapts the Q-learning model to select the timing and frequency of retransmission to enhance the transmission reliability. We also design some transmission schemes—K-repetition, T-delay and [T, K]-overlap—which are used to shorten latency and avoid packet collision. Compared with the conventional 5G HARQ, our simulation results show that the proposed A-HARQ scheme decreases the system’s average BLER, the number of retransmissions, and the RTT to 5.55%, 1.55 ms, and 0.97 ms, respectively.

Performance Evaluation of an On-Body Wireless Body Network Based on an Ultra-Wideband Physical Layer under a Dynamic Channel Model

Wireless body area networks (WBANs) are attracting attention as an important technology for realizing the Internet of Medical Things (IoMT). In addition, ultra-wideband (UWB) is one of the wireless communication technologies suitable for the IoMT and WBANs. Our previous study investigated the feasibility of WBANs utilizing UWB under ideal and static wearable WBAN channel models. The present research applies a dynamic on-body UWB channel model to a WBAN as a more realistic channel model. The feasibility of a high-reliability UWB-WBAN is demonstrated by evaluating the physical layer performance. Numerical results reveal the maximum number of retransmissions needed to achieve the desired transmission failure ratio for each link type and the corresponding energy efficiency and average number of retransmissions. These findings contribute to the realization of a highly reliable IoMT utilizing UWB-WBANs in a practical environment.

Financial Big Data Based on Internet of Things and Wireless Network Communication

With the advent of the era of big data, Internet of things technology and wireless communication technology have been in a state of rapid development. Opportunities and challenges in all walks of life are being subverted. Financial management, as the foundation of corporate governance, is important for improving economic efficiency and achieving sustainable business development which plays an important role. In order to realize the management and classification of financial big data, better identify the financial data of different enterprises, strengthen the safe storage of financial information, and provide early warning for the security issues involved, this article is based on the Internet of things and wireless communication networks. In the method part, this article introduces the framework of the Internet of things, Bluetooth, and infrared data transmission in wireless network communication and the principles of financial big data. The algorithm introduces a single‐user MIMO system, free space propagation, and spectrum and energy efficiency. The analysis part analyzes the spectrum efficiency of different algorithms, social utility, average number of retransmissions, comprehensive scores of competitiveness in various fields of the Internet of things, and the significance of financial indicators. By comparing the data, it can be seen that the algorithm in this paper is superior to the two algorithms of IAN‐CoMP and IA‐CoMP. When the number of users is 100, the social utility of the algorithm in this paper is 4.45, while IAN‐CoMP is 3.43 and IA‐CoMP is 3.67. When the number of users increases to 700, the social utility of the algorithm in this paper is 28.34. The other two algorithms are, respectively, 24.45 and 25.99, and we know that the social utility of the algorithm in this paper is the best. Through comprehensive analysis, it is concluded that the financial big data model based on the Internet of things and wireless network communication in this paper can better realize data management and collection, so as to meet the needs of information developers.

A Low-Latency Transmission Method for Massive MIMO Systems With Low Control Signaling Overhead

In this paper, we consider the uplink of massive MIMO systems where the channel capacity is almost deterministic and varies slowly over time. We exploit this fact, by appropriately choosing the length of the codeword only once based on an initial estimate of the uplink channel capacity fed back by the base station (BS). The user terminal (UT) then transmits the codeword over consecutive coherence time intervals without waiting for any acknowledgement (ACK/NACK) from the BS. The BS sends only a single ACK/NACK after it completes decoding. Therefore, the proposed method has significantly less latency and signaling overhead when compared with stop-and-wait type hybrid automatic repeat request (HARQ) methods (as in LTE uplink) where a lot of delay is introduced as the UT needs to wait for the BS to signal the ACK/NACK for every retransmission. Analysis reveals that for sufficiently large number of antennas at the BS, the average codeword length of the proposed method (in number of coherence intervals) is the same as the average number of retransmissions (in number of coherence intervals) required by incremental redundancy (IR)-based HARQ and also that the energy efficiency of the proposed method and IR-HARQ is the same.

Analysis of Two-Unicast Network-Coded Hybrid-ARQ With Unreliable Feedback

Network-coded (NC) automatic repeat request (ARQ) systems have been shown to provide significant throughput improvements over basic ARQ systems in multiuser wireless systems. These systems have been extended to NC hybrid-ARQ (HARQ) to show further enhancements in throughput by allowing receivers to use previous retransmissions. However, prior results were derived under the assumption of perfect ARQ feedback channels. In practical systems, feedback channels are not perfect, and therefore it is crucial to study the effect of noise in the ARQ feedback channels. In this paper, we consider the case of two-unicast flows and extend NC-HARQ to the case of imperfect ARQ feedback. Assuming binary symmetric feedback channels, we analyze the performance of these systems in terms of throughput, probability of packet loss, and average number of retransmissions. In the presence of feedback noise, our results show that significant throughput improvements over basic HARQ can still be obtained for a moderate-to-high signal-to-noise ratio with negligible increase in the probability of packet loss. We also present a new scheme that limits the number of NC packets to only one per data packet and show that for the two-unicast case the new scheme attains most of the throughput improvements of the original NC-HARQ scheme.

Wireless Broadcasting Retransmission Strategy of most Lost Packets Priority Based on Network Coding

Combining network coding, a wireless broadcasting retransmission strategyMost Lost Packets Priority is proposed to decrease the number of retransmissions, preferentially consider nodes which have most lost packets, choose the suitable packets to be encoded and retransmission in order to reduce the number of retransmissions, increase network efficiency in wireless network. It is showed in experiment that compared with BENEFIT, MLPP can reduce the average number of retransmissions, and make the average number of retransmissions closer to the preferential number of retransmission and improve the transmission efficiency.

Link Adaptation for Energy-Efficient Transmission with Receiver CSI

This paper derives link adaptation solutions for different wireless communications channels, maximizing the energy efficiency. These solutions account for the transmission as well as processing power consumption. The minimum energy consumption is achieved by solving an optimization problem, which we prove to be quasi-convex. We show that a convex function characterizes the average number of retransmissions when errors are due to channel noise or fading. We also derive closed-form approximations of the optimal link parameters for Rayleigh and Nakagami channels. These indicate that the target outage probability is only a function of the packet length.

Uncoordinated orthogonal frequency division multiple access: To spread or not to spread

We study uncoordinated multiple access using the orthogonal frequency division multiple access (OFDMA) technique where multiple users independently and randomly pick a sub-carrier from a set of sub-carriers for transmission in each slot. Signals transmitted on distinct sub-carriers are orthogonal to each other while signals transmitted by different users on the same sub-carrier interfere with each other. We study average throughput and outage probability performance of such a system in the asymptotic limit of large numbers of sub-carriers and users while keeping the ratio of number of users to sub-carriers fixed, for non-fading, flat fading, and frequency-selective fading additive white Gaussian noise channels. The performance is compared to that of a system in which all users spread their signal over all the sub-carriers as in a code division multiple access (CDMA) system. Our results show that at high signal-to-noise ratio (SNR), transmission without spreading results in higher throughput but requires more retransmissions on the average. At low SNRs, the throughput performance is comparable but the system with spreading requires smaller average number of retransmissions.

Performance of multi-relay collaborative hybrid-ARQ protocols over fading channels

According to collaborative hybrid automatic-repeat-request (ARQ) protocols, relay stations that have been able to decode the original message from previous transmissions, collaborate with the source in future retransmissions by jointly sending a space-time codeword. In this letter, analysis of the average number of retransmissions and throughput of collaborative hybrid-ARQ Type I (i.e., without memory) and chase combining (i.e., with memory) protocols is provided for any number of relays.

An ARQ Scheme with Memory and Soft Error Detectors

This paper describes a technique for increasing the efficiency of an ARQ communication system utilizing error detection codes. In this technique the blocks containing errors are not discarded at the receiver, as in the conventional ARQ systems. Such blocks are retained in order to make use of the information contained in them. A reliability value is associated to each demodulated symbol; this reliability value is updated every time a new retransmission is made, even if the vector received is in error. The process of updating the symbols often eliminates automatically the errors introduced by the channel. The results obtained by means of a simulation show that this method offers a considerable reduction in the average number of retransmissions, in comparison with conventional ARQ systems.