To see the other types of publications on this topic, follow the link: Backoff method.
Journal articles on the topic 'Backoff method'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 journal articles for your research on the topic 'Backoff method.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse journal articles on a wide variety of disciplines and organise your bibliography correctly.
1
Yamazaki, Taku, Ryo Yamamoto, Takumi Miyoshi, Takuya Asaka, and Yoshiaki Tanaka. "Opportunistic Routing Using Prioritized Forwarders with Retransmission Control." Image Processing & Communications 21, no. 1 (2016): 57–66. http://dx.doi.org/10.1515/ipc-2016-0005.
Full textAbstract:
Abstract In ad hoc networks, broadcast-based forwarding protocols called opportunistic routing have been proposed. In general backoff-based opportunistic routing protocols, each receiver autonomously makes a forwarding decision using a random backoff time based on logical distance. However, each potential forwarder must wait for the expiration of the backoff timer before the packet forwarding. Moreover, they cannot gain forwarding path diversity in sparse environments. In this paper, we propose a novel forwarder selection method for opportunistic routing. In the proposed method, a terminal called, a prioritized forwarder, and which is selected from among neighbours and can forward packets without using the backoff time. In addition, we integrate a hop-by-hop retransmission control in the proposed method, which improves the packet transmission success rate in sparse environments. We evaluate the proposed method in comparison with the conventional protocols in computer simulations.
2
Liang, Yongjun, Ismail Fauzi Bin Isnin, Nur Haliza Abdul Wahab, and Jiafu Su. "Deep Q-learning for reducing enhanced distributed channel access collision in IEEE 802.11p of Vehicular Ad Hoc Network." Journal of Infrastructure, Policy and Development 8, no. 15 (2024): 9494. https://doi.org/10.24294/jipd9494.
Full textAbstract:
The purpose of Vehicular Ad Hoc Network (VANET) is to provide users with better information services through effective communication. For this purpose, IEEE 802.11p proposes a protocol standard based on enhanced distributed channel access (EDCA) contention. In this standard, the backoff algorithm randomly adopts a lower bound of the contention window (CW) that is always fixed at zero. The problem that arises is that in severe network congestion, the backoff process will choose a smaller value to start backoff, thereby increasing conflicts and congestion. The objective of this paper is to solve this unbalanced backoff interval problem in saturation vehicles and this paper proposes a method that is a deep neural network Q-learning-based channel access algorithm (DQL-CSCA), which adjusts backoff with a deep neural network Q-learning algorithm according to vehicle density. Network simulation is conducted using NS3, the proposed algorithm is compared with the CSCA algorithm. The find is that DQL-CSCA can better reduce EDCA collisions.
3
Et.al, Goo Kim. "A Study of BLE Mesh Network Scheduling Algorithm Using A Smartplug." Turkish Journal of Computer and Mathematics Education (TURCOMAT) 12, no. 6 (2021): 456–51. http://dx.doi.org/10.17762/turcomat.v12i6.1865.
Full textAbstract:
This paper proposes a BLE Mesh network scheduling algorithm using SmartPlug. And proposes random-backoff, a very simple method for collision avoidance. The low-energy scheduling algorithm of SmartPlug and BLE node is proposed. SmartPlug periodically broadcasts its own information to inform the surrounding BLE nodes and SmartPlug. A node for data communication with SmartPlug is decided for efficiency. The BLE node periodically transmits data and switches to sleep mode after data transmission. In this paper, propose a very simple method, random-backoff, to reduce collisions when transmitting data in a BLE node. In the simulation of results shows when the data size is 1 ~ 31 bytes and 32 ~ 255 bytes, and random-backoff is effective when 1~31 bytes length. In the case of 32 to 255 bytes, random-backoff is not effective, so additional research is needed. And the simulation conducts under the same condition, but it shows that the data length and the number of transmission attempts has an effect. The simulation results show the transmission success ratio is similar regardless of the data length when random-backoff is not applied. It also shows the number of transmission attempts has an effect. Also, this simulation shows the results that as the number of nodes increases, the wireless environment becomes congested, and the transmission success ratio decreases. As a result of the simulation, random-backoff for collision avoidance is effective in transmitting data of 1 to 31 bytes better than 32 to 255 bytes in the data length.
4
Nakamura, Kazutoyo, Shinsuke Satake, and Hiroshi Inai. "An access method using fixed backoff for wireless LANs." Electrical Engineering in Japan 173, no. 3 (2010): 30–39. http://dx.doi.org/10.1002/eej.21044.
Full text
5
Hua, Qiao Guan, Mao Jian Lin, Guo Ning, Chen Bo, Dai Ning, and Zhang Chuan Long. "An Improved Backoff Scheme for the IEEE 802.15.4 MAC Protocol." Applied Mechanics and Materials 427-429 (September 2013): 2622–25. http://dx.doi.org/10.4028/www.scientific.net/amm.427-429.2622.
Full textAbstract:
To solve the impact on network performance by the mobile nodes and data transfer rate constantly changing,this paper proposes a improved backoff scheme for IEEE802.15.4, which uses Probability Judgement based on Network Load and Exponentially Weighted Moving Average (PJNL_EWMA). According to a real-time monitoring of current network status by probability judgement of network load , this method dynamically adjust backoff exponent by EWMA when the CSMA/CA begins. Compared the IEEE802.15.4 and MBS+EWMA schemes, the simulation experiments on NS2 platform show that the PJNL_EWMA scheme not only improves the throughput of the network, but also reduces the packet loss rate and the collision ratio,significantly improve the network performance.
6
Nakamura, Kazutoyo, Shinsuke Satake, and Hiroshi Inai. "An Access Method by Using Fixed Backoff for Wireless LANs." IEEJ Transactions on Electronics, Information and Systems 128, no. 11 (2008): 1610–18. http://dx.doi.org/10.1541/ieejeiss.128.1610.
Full text
7
Minooei, Hadi, and Hassan Nojumi. "Performance evaluation of a new backoff method for IEEE 802.11." Computer Communications 30, no. 18 (2007): 3698–704. http://dx.doi.org/10.1016/j.comcom.2007.07.003.
Full text
8
Owais Khan, Muhammad Ismail, and Imad Ali. "A Dual-Channel MAC Protocol with Fibonacci Backoff for Enhanced Efficiency in UAV-Based Sensor Networks." Proceedings of the Pakistan Academy of Sciences: A. Physical and Computational Sciences 61, no. 2 (2024): 217–25. http://dx.doi.org/10.53560/ppasa(61-2)847.
Full textAbstract:
Unmanned aerial vehicles (UAVs) are highly effective in collecting data from challenging environments equipped with Wireless Sensor Networks (WSNs), overcoming retrieval challenges. However, using a single-channel Medium Access Control (MAC) protocol for synchronization can lead to potential data collisions among multiple sensors sharing the same medium and result in high power consumption. In this article, we propose a dual-channel MAC protocol specifically designed for UAV-based data collection from WSNs. The protocol includes features such as varying transmission power levels for UAVs, dedicated channels for control and data packets, and a Fibonacci Backoff strategy. The UAV optimizes power usage by initially using low-power transmission and gradually increasing it. The dual-channel communication allows for separate channels for wakeup signals and data transmission, enhancing efficiency. Additionally, the sleep and wakeup mechanism conserves sensor node battery power during inactivity. We developed a discrete event simulator to evaluate the proposed protocol's performance. Our simulation results show that the average for each node count, the proposed protocol with the Fibonacci Backoff strategy improves network throughput by 20.68%, reduces delay by 22.32%, and decreases power consumption by 21.84% compared to the conventional Exponential Backoff method.
9
Ming, Zidong, Xin Liu, Xiaofei Yang, and Mei Wang. "An Improved CSMA/CA Protocol Anti-Jamming Method Based on Reinforcement Learning." Electronics 12, no. 17 (2023): 3547. http://dx.doi.org/10.3390/electronics12173547.
Full textAbstract:
The CSMA/CA algorithm uses the binary backoff mechanism to solve the multi-user channel access problem, but this mechanism is vulnerable to jamming attacks. Existing research uses channel-hopping to avoid jamming, but this method fails when the channel is limited or hard to hop. To address this problem, we first propose a Markov decision process (MDP) model with contention window (CW) as the state, throughput as the reward value, and backoff action as the control variable. Based on this, we design an intelligent CSMA/CA protocol based on distributed reinforcement learning. Specifically, each node adopts distributed learning decision-making, which needs to query and update information from a central status collection equipment (SCE). It improves its anti-jamming ability by learning from different environments and adapting to them. Simulation results show that the proposed algorithm is significantly better than CSMA/CA and SETL algorithms in both jamming and non-jamming environments. And it has little performance difference with the increase in the number of nodes, effectively improving the anti-jamming performance. When the communication node is 10, the normalized throughputs of the proposed algorithm in non-jamming, intermittent jamming, and random jamming are increased by 28.45%, 21.20%, and 17.07%, respectively, and the collision rates are decreased by 83.93%, 95.71%, and 81.58% respectively.
10
Rim, Minjoong. "Delayed Response and Random Backoff First for Low-Power Random Access of IoT Devices with Poor Channel Conditions." Sensors 23, no. 23 (2023): 9556. http://dx.doi.org/10.3390/s23239556.
Full textAbstract:
As IoT services become more active, the density of IoT devices is increasing, and massive connectivity technology is needed to support numerous devices simultaneously. In addition, IoT devices are often battery-powered, and during random access, it is necessary to reduce the power consumption to extend the lifetime of the devices. In particular, devices with poor channels need to send at a very low transmission rate through a large number of repetitions, and longer packet lengths can increase the probability of collisions, increasing the power consumption while shortening the lifetime of the IoT system. Dividing devices into groups based on the number of repetitions and allocating different resources to each group can reduce collisions for bad-channel devices, but it can be difficult to support large connections, due to the inefficient use of resources. This paper proposes schemes to reduce the collision probability of bad-channel devices while allowing IoT devices to use shared resources, instead of dividing resources by groups. There are two versions of the proposed schemes. The first method reduces collisions by delaying the response of a bad-channel device, and in the meantime, eliminating interference from other devices, assuming that the bad-channel device is not sensitive to delay. Instead of checking the response, and then, performing a random backoff when no acknowledgement packet is received, the second proposed method reverses the order of response checking and random backoff, that is, it first performs a random backoff, and then, checks the response to decide whether to retransmit. The proposed method can increase the lifetime of the IoT system by reducing the collision probability of a bad-channel device, without degrading the performance of other devices.
11
Zhao, Taifei, Jing Wang, Shiqi Wang, and Xingshan Li. "Underwater wireless optical communication multi-tokens random backoff neighbor discovery method." Journal of the Optical Society of America A 36, no. 9 (2019): 1475. http://dx.doi.org/10.1364/josaa.36.001475.
Full text
12
He, Yong, Jie Sun, Ruixi Yuan, and Weibo Gong. "A reservation based backoff method for video streaming in 802.11 home networks." IEEE Journal on Selected Areas in Communications 28, no. 3 (2010): 332–43. http://dx.doi.org/10.1109/jsac.2010.100405.
Full text
13
Swetha, R., G. Vijaya kanth, and M. Venkatesh Naik. "Robust Semi-Random Backoff (RSRB) Method for Data Allocation in Mobile Networks." International Journal of Engineering Trends and Technology 15, no. 2 (2014): 50–53. http://dx.doi.org/10.14445/22315381/ijett-v15p211.
Full text
14
Lee, Yutae, Min Young Chung, and Tae-Jin Lee. "Performance Analysis of IEEE 802.11 DCF under Nonsaturation Condition." Mathematical Problems in Engineering 2008 (2008): 1–17. http://dx.doi.org/10.1155/2008/574197.
Full textAbstract:
Carrier sense multiple access with collision avoidance (CSMA/CA) methods are considered to be attractive MAC protocols for wireless LANs. IEEE 802.11 distributed coordination function (DCF) is a random channel access scheme based on CSMA/CA method and the binary slotted exponential backoff procedure to reduce the packet collision. In this paper, we propose a new analytical model for a nonsaturated IEEE 802.11 DCF network and evaluate its performance. We verify our model using simulations and show that our results agree with the simulations.
15
Lee, Won Hyoung, Ho Young Hwang, and Jo Woon Chong. "Runtime Estimation of the Number of Active Devices in IEEE 802.15.4 Slotted CSMA/CA Networks with Deferred Transmission and No Acknowledgment Using ARMA Filters." Wireless Communications and Mobile Computing 2018 (September 2, 2018): 1–12. http://dx.doi.org/10.1155/2018/5420876.
Full textAbstract:
We propose a novel method for estimating the number of active devices in an IEEE 802.15.4 network. Here, we consider an IEEE 802.15.4 network with a star topology where active devices transmit data frames using slotted carrier sense multiple access with collision avoidance (CSMA/CA) medium access control (MAC) protocol without acknowledgment. In our proposed method, a personal area network (PAN) coordinator of a network counts the number of events that a transmission occurs and the number of events that two consecutive slots are idle in a superframe duration, and the PAN coordinator broadcasts the information through a beacon frame. Each device can count the number of slots that each device is in the backoff procedure and the number of the first clear channel assessment (CCA) that each device performs whenever it performs the first CCA after the backoff procedure. Then, each device estimates the number of active devices in the network based on these counted numbers and the information from PAN coordinator with the help of an autoregressive moving average (ARMA) filter. We evaluate the performance of our proposed ARMA-based estimation method via simulations where active devices transmit data frames in IEEE 802.15.4 slotted CSMA/CA networks. Simulation results show that our proposed method gives estimation errors of the number of active devices less than 4.501% when the actual number of active devices is varying from 5 to 80. We compare our proposed method with the conventional method in terms of the average and standard deviation for the estimated number of active devices. The simulation results show that our proposed estimation method is more accurate than the conventional method.
16
SUKARIDHOTO, Sritrusta, Nobuo FUNABIKI, Toru NAKANISHI, Kan WATANABE, and Shigeto TAJIMA. "A Fixed Backoff-Time Switching Method for CSMA/CA Protocol in Wireless Mesh Networks." IEICE Transactions on Communications E96.B, no. 4 (2013): 1019–29. http://dx.doi.org/10.1587/transcom.e96.b.1019.
Full text
17
Xie, Zhijun, Baocheng Wang, Jiancheng Yu, et al. "An Optimal Backoff Time-Based Internetwork Interference Mitigation Method in Wireless Body Area Network." Journal of Sensors 2020 (March 2, 2020): 1–13. http://dx.doi.org/10.1155/2020/4365191.
Full textAbstract:
When multiple Wireless Body Area Networks (WBANs) are aggregated, the overlapping region of their communications will result in internetwork interference, which could impose severe impacts on the reliability of WBAN performance. Therefore, how to mitigate the internetwork interference becomes the key problem to be solved urgently in practical applications of WBAN. However, most of the current researches on internetwork interference focus on traditional cellular networks and large-scale wireless sensor networks. In this paper, an Optimal Backoff Time Interference Mitigation Algorithm (OBTIM) is proposed. This method performs rescheduling or channel switching when the performance of the WBANs falls below tolerance, utilizing the cell neighbour list established by the beacon method. Simulation results show that the proposed method improves the channel utilization and the network throughput, and in the meantime, reduces the collision probability and energy consumption, when compared with the contention-based beacon schedule scheme.
18
Tang, Yong. "Research the QOS of Ad HOC Network MAC Layer Based on Inpoint Method of Sumt." Applied Mechanics and Materials 475-476 (December 2013): 909–14. http://dx.doi.org/10.4028/www.scientific.net/amm.475-476.909.
Full textAbstract:
One of the choke point of AD HOC network is that the system hasnt resolved the problem of QOS in the MAC layer, the MAC layer QOS of AD HOC network is divided into two levels, one is flow level, and the other is node level. In order to solve QOS problem, this paper proposed a new algorithm IMSMAC, the algorithm use penalty function to optimize the value of different level of service in flow level, and use different priority backoff index to different node in node level. Analysis the throughput and delay of IMSMAC and DCF in NS2, the result showed that the high priority service have a certain degree of improvement in throughput and delay in IMSMAC algorithm.
19
Khanafer, Mounib, Mouhcine Guennoun, Mohammed El-Abd, and Hussein T. Mouftah. "Improved Adaptive Backoff Algorithm for Optimal Channel Utilization in Large-Scale IEEE 802.15.4-Based Wireless Body Area Networks." Future Internet 16, no. 9 (2024): 313. http://dx.doi.org/10.3390/fi16090313.
Full textAbstract:
The backoff algorithm employed by the medium access control (MAC) protocol of the IEEE 802.15.4 standard has a significant impact on the overall performance of the wireless sensor network (WSN). This algorithm helps the MAC protocol resolve the contention among multiple nodes in accessing the wireless medium. The standard binary exponent backoff (BEB) used by the IEEE 802.15.4 MAC protocol relies on an incremental method that doubles the size of the contention window after the occurrence of a collision. In a previous work, we proposed the adaptive backoff algorithm (ABA), which adapts the contention window’s size to the value of the probability of collision, thus relating the contention resolution to the size of the WSN in an indirect manner. ABA was studied and tested using contention window sizes of up to 256. However, the latter limit on the contention window size led to degradation in the network performance as the size of the network exceeded 50 nodes. This paper introduces the Improved ABA (I-ABA), an improved version of ABA. In the design of I-ABA we observe the optimal values of the contention window that maximize performance under varying probabilities of collision. Based on that, we use curve fitting techniques to derive a mathematical expression that better describes the adaptive change in the contention window. This forms the basis of I-ABA, which demonstrates scalability and the ability to enhance performance. As a potential area of application for I-ABA, we target wireless body area networks (WBANs) that are large-scale, that is, composed of hundreds of sensor nodes. WBAN is a major application area for the emerging Internet of Things (IoT) paradigm. We evaluate the performance of I-ABA based on simulations. Our results show that, in a large-scale WBAN, I-ABA can achieve superior performance to both ABA and the standard BEB in terms of various performance metrics.
20
Liu, Xiang Yang, Yang Wang, and Ying Mei Chen. "A Contention-Based Transmission Strategy for Distributed Radar Sensor Network." Applied Mechanics and Materials 513-517 (February 2014): 3317–21. http://dx.doi.org/10.4028/www.scientific.net/amm.513-517.3317.
Full textAbstract:
A channel-sharing method was proposed to improve the energy efficiency per detection task in distributed radar sensor network. The sensor nodes transmitted their local test statistics (LTS) to the fusion center in approximately descending order of their LTSs by modifying the value of backoff timer and frame interval according to the value of their LTSs. Simulation results show that, compared with the method using dedicated channels to transfer data to the fusion center, the occurrence of the discrepancy between the global decisions of the two methods is less than 30 per a million tests. The increased amount of transmitted data, however, is not more than 5%, and the channel bandwidth of the system is reduced to of the original. Therefore, the proposed method fulfills the evident decrease in communication bandwidth, at a very small cost of detection performance.
21
Wiese, B., and K. S. Jacobsen. "Use of the reference noise method bounds the performance loss due to upstream power backoff." IEEE Journal on Selected Areas in Communications 20, no. 5 (2002): 1075–84. http://dx.doi.org/10.1109/jsac.2002.1007388.
Full text
22
Md., Masudul Haque, Tarek Habib Md., and Mokhlesur Rahman Md. "AUTOMATED WORD PREDICTION IN BANGLA LANGUAGE USING STOCHASTIC LANGUAGE MODELS." International Journal on Foundations of Computer Science & Technology (IJFCST) 5, no. 6 (2023): 9. https://doi.org/10.5281/zenodo.7998164.
Full textAbstract:
Word completion and word prediction are two important phenomena in typing that benefit users who type using keyboard or other similar devices. They can have profound impact on the typing of disable people. Our work is based on word prediction on Bangla sentence by using stochastic, i.e. N-gram language model such as unigram, bigram, trigram, deleted Interpolation and backoff models for auto completing a sentence by predicting a correct word in a sentence which saves time and keystrokes of typing and also reduces misspelling. We use large data corpus of Bangla language of different word types to predict correct word with the accuracy as much as possible. We have found promising results. We hope that our work will impact on the baseline for automated Bangla typing.
23
Chen, Min, Jiang Zhu, Yu Xin Zhang, Tao Yan, Chong Xie, and Hua Zhao. "Research on RFID Anti-Collision Algorithms Based on Quadtree." Advanced Materials Research 978 (June 2014): 226–30. http://dx.doi.org/10.4028/www.scientific.net/amr.978.226.
Full textAbstract:
This paper presents an improved RFID anti-collision algorithm, which is on the basis of the bit-locking backoff anti-collision algorithm. A method of sending 2 bits length collision information,is used in the recognition process.The reader determines whether the quadtree strategy is adopted according to the collision information of the “00”,“01”,“10”,“11”, effectively reducing the null operations. The proposed algorithm is analyzed carefully in account, transmission delay and throughput of the system. Simulation results show that the improved algorithm have better performance compared with the same class of anti-collision algorithm, which is more suitable for multi-tab environment.
24
Lee, Taegyeom, and Ohyun Jo. "Imitation Learning Backoff: Reinforcement Learning-based Channel Access for Guaranteeing Fairness (Student Abstract)." Proceedings of the AAAI Conference on Artificial Intelligence 39, no. 28 (2025): 29401–3. https://doi.org/10.1609/aaai.v39i28.35266.
Full textAbstract:
This paper addresses contention window optimization for multi-access scenarios. Our investigation into state-of-the-art models revealed that a limited number of nodes dominate the communication channels. Such monopolization issues are critical in networks as they can lead to significant disruptions. To mitigate this monopolization problem, we propose an imitation learning-based backoff mechanism. The proposed model is a reinforcement learning-based contention window optimization method. It imitates the expert's policy to ensure fair policy convergence for the agent and includes opportunities for weight adjustment to boost performance. The proposed model shows a fairness improvement of approximately 20% to 41% across various scenarios.
25
Wang, Weicheng, Jianpo Li, Yang Lu, and Chuang Liu. "Optimization Method of Adaptive Backoff and Duty Cycle for S-MAC Protocol in Wireless Sensor Networks." IEEE Access 9 (2021): 15066–73. http://dx.doi.org/10.1109/access.2021.3053328.
Full text
26
Touijer, Bethaina, Yann Ben Maissa, and Salma Mouline. "IEEE 802.15.6 CSMA/CA access method for WBANs: Performance evaluation and new backoff counter selection procedure." Computer Networks 188 (April 2021): 107759. http://dx.doi.org/10.1016/j.comnet.2020.107759.
Full text
27
Shah, A. F. M. Shahen. "Architecture of Emergency Communication Systems in Disasters through UAVs in 5G and Beyond." Drones 7, no. 1 (2022): 25. http://dx.doi.org/10.3390/drones7010025.
Full textAbstract:
Unmanned aerial vehicles (UAVs) are valued in 5G and 6G networks due to their communication capabilities, low cost, and flexible deployment. Recently, UAV-aided emergency networks in disasters have been designed where one single large UAV is used. Compared with a single large UAV, Flying Ad Hoc Networks (FANETs) with small UAVs have many benefits. Therefore, instead of a single large UAV, a FANET is proposed in this paper. To take full advantage of their services, UAVs must be able to communicate efficiently with each other and with existing networking infrastructures. However, high node mobility is one of the main characteristics of FANETs, which can result in rapid topology changes with frequent link breakage and unstable communications that cause collision and packet loss. As an alternative, networks can be broken up into smaller groups or clusters to control their topology efficiently and reduce channel contention. In this study, a novel cluster-based mechanism is proposed for FANETs. The process of cluster management is described. The IEEE 802.11 backoff method is specifically intended for direct communications and is not appropriate for cluster-based communications. Therefore, a new backoff mechanism is proposed based on cluster size to optimize performance. An analytical study using the Markov chain model is presented to explore the performance of the proposed mechanism. The study takes into account Nakagami-m fading channels. Performance-influencing parameters are taken into consideration and the relationships among these parameters as well as performance metrics such as throughput, packet dropping rate, outage probability, and delay are obtained. Furthermore, simulation results are provided which verify the analytical studies. A quantitative comparison with current cluster-based methods is also presented. The simulation results show that the suggested technique enhances system performance and complies with the safety message delay constraint of 100 ms.
28
Wang, Shengwei, Jun Liu, Wei Cai, Minghao Yin, Lingyun Zhou, and Hui Hao. "Multi-hop Fast Conflict Resolution Algorithm for Ad Hoc Networks." ITM Web of Conferences 17 (2018): 01004. http://dx.doi.org/10.1051/itmconf/20181701004.
Full textAbstract:
Media access control is an important technology in ad hoc networks. Based on the multi-hop Pseudo Bayesian (PB) algorithm and the single-hop Fast Conflict Resolution algorithm (FCR), in this paper, we propose a Multi-hop Fast Conflict Resolution (MFCR) algorithm for ad hoc networks. We make the detailed introduction of the theoretical model, the pseudo Bayesian analysis and the algorithm deign. MFCR employs a competition probability forecasting method, which is similar to the backoff counter used in FCR, combined with the handshake process used in PB to solve the utilization and the fairness problems of the time slot allocation. Simulations show that the MFCR has evident improvement in the network performance.
29
Korzun, D. G., O. Yu Bogoiavlenskaia, and K. A. Kulakov. "Applying the Random Backoff Algorithm for Active Information Exchange Control in Smart Internet Environment Server." Programmnaya Ingeneria 14, no. 5 (2023): 207–16. http://dx.doi.org/10.17587/prin.14.207-216.
Full textAbstract:
The information exchange-as a way of interaction for participants in an Internet environment-is a fundamental function of a distributed system within the computing paradigms of Internet of Things, Cyber-Physical Systems, Ambient Intelligence etc. Participants in an Internet environment are represented by software agents running typically on low-performance edge computing devices. Interaction is implemented through exchange of information collected by the participants in a shared information store that implements the «intelligence» of this environment. The organization of agents access to the shared information and of their interaction uses a semantic information broker that manages information flows between participants. With an increase in the number, diversity, and activity of participants, the workload on the broker and the data transmission network increases. In this paper, a novel method is proposed to reduce the workload by delegating part of the control of the information exchange to the participants themselves. The subscription mechanism is modified for information changes in a shared information store. Instead of the passive option, when the broker must notify all agents who have subscribed to the information being changed, the active option is used, when agents themselves can check for information changes. A new two-component control method based on the well-known backoff algorithm in combination with the well-known adaptive strategy for choosing the time of sending the next request from an agent to a broker for the presence of information changes is proposed. The control capabilities are studied experimentally using a simulated Internet environment.
30
Sun, Jun. "A multi-objective optimization based doherty power amplifier and its matching network optimization method." PLOS ONE 18, no. 12 (2023): e0293371. http://dx.doi.org/10.1371/journal.pone.0293371.
Full textAbstract:
In the actual design process of traditional power amplifiers, there is a problem of being cumbersome and unable to simultaneously meet low power and saturation modes. Therefore, an improved multi-objective optimization algorithm proposed by decomposition is introduced to optimize its matching network to achieve overall optimization design of power amplifiers. The algorithm, matching network, and optimized power amplifier performance are simulated and verified. The experimental outcomes denote that on the logic function with Zener diode transistor, the proposed algorithm has a mean generation distance index of 5.03E-3, which is lower than most algorithms. Its overall comprehensive performance is better than the comparison algorithm, and compared to the comparison algorithm, it converges more quickly in the early stage of iteration on 1 and 2, and tends to stabilize in the 40th generation, and completes convergence in the 80th generation. In addition, the optimal solution has already begun to appear around the 25th generation and reached saturation around the 70th generation. At the same time, in the actual working bandwidth, the optimized power amplifier saturation efficiency reaches 51.5%~61.9%, and the efficiency at 6dB power backoff is about 44.4%~56.5%. Overall, the algorithm proposed in the study is effective in optimizing power amplifiers and their matching networks, effectively solving the problem of insufficient efficiency in low power modes in traditional designs.
31
Ming-Chu Chou, Guang-Jhe Lin, Chih-Heng Ke, and Yeong-Sheng Chen. "Differentiated QoS Provisioning in Wireless Networks Based on Deep Reinforcement Learning." Advances in Technology Innovation 9, no. 4 (2024): 257–72. http://dx.doi.org/10.46604/aiti.2024.13655.
Full textAbstract:
Wireless networks manage performance by adjusting the contention window, as they cannot directly detect collisions. Traditional contention window adjustment algorithms, such as the Binary Exponential Backoff (BEB) algorithm, may lead to lower throughput when multiple services with varying bandwidth demands coexist. To address this issue, this study aims to enhance network throughput by enabling differentiated bandwidth allocation for various services. Using deep reinforcement learning, the state space, action space, and reward functions are defined to optimize this differentiation. These definitions are integrated into the Deep Deterministic Policy Gradient (DDPG) technique, implemented in the Access Point (AP) to intelligently adjust the contention window. Leveraging DDPG’s capability for continuous actions, the proposed method provides Quality of Service (QoS) differentiation, ensuring that each service at its respective priority level meets its transmission requirements. Compared to the BEB algorithm, the proposed approach offers improved traffic allocation and higher network bandwidth utilization.
32
Hassan, Emad S. "Performance enhancement and PAPR reduction for MIMO based QAM-FBMC systems." PLOS ONE 19, no. 1 (2024): e0296999. http://dx.doi.org/10.1371/journal.pone.0296999.
Full textAbstract:
Filter Bank Multi-Carrier (FBMC) is attracting significant interest as a multi-carrier modulation (MCM) approach for future communication systems. It offers numerous advantages in contrast to Orthogonal Frequency Division Multiplexing (OFDM). Nonetheless, similar to many other MCM techniques, FBMC encounters a significant challenge with a high Peak-to-Average Power Ratio (PAPR). Additionally, incorporating Multiple-Input and Multiple-Output (MIMO) into FBMC presents heightened difficulties due to the presence of complex interference and increased computational complexity. In this paper, we first study the performance analysis of MIMO based Quadrature Amplitude Modulation (QAM)-FBMC systems considering the system complexity and interference. To enhance coverage effectively using beamforming with multiple antennas, it is essential to reduce PAPR to minimize the input backoff (IBO) required by nonlinear power amplifiers. Therefore, we propose new PAPR reduction method for MIMO based QAM-FBMC systems leveraging the null space within the MIMO channel using clipping and filtering (CF) technique. The PAPR reduction signals generated in this process are then mapped to the null space of the overall MIMO channel for each frequency block. Through computer simulations using a nonlinear power amplifier model, we illustrate that the proposed method substantially enhances both PAPR and throughput of MIMO based FBMC systems compared to conventional methods.
33
Wu, Huarui, Xiao Han, Huaji Zhu, Cheng Chen, and Baozhu Yang. "An Efficient Opportunistic Routing Protocol with Low Latency for Farm Wireless Sensor Networks." Electronics 11, no. 13 (2022): 1936. http://dx.doi.org/10.3390/electronics11131936.
Full textAbstract:
Wireless sensor networks (WSN) can accurately and timely obtain the production information of crops, and provide data basis for intelligent agriculture. The dynamic crop state and unstable climate environment make it difficult to predict the connectivity probability of wireless links. Therefore, this paper studies an energy-saving opportunity routing transmission strategy under the influence of dynamic link interaction. The protocol establishes an importance model based on algebraic connectivity to reduce the energy consumption of network key nodes. At the same time, based on the improved Bellman–Ford algorithm, a method of constructing candidate sets is studied. It converts the opportunistic routing transmission cost of farm WSN into anycast link cost and the remaining opportunistic path cost affected by energy consumption. The priority queue is used to determine the nodes participating in the iteration, thereby reducing the computational overhead. The protocol also designs a backoff strategy considering the current residual energy to select the only forwarding node and reduce the unnecessary packet copies in the transmission process. Simulation results show that the studied method is superior to the existing opportunistic routing schemes in terms of packet overhead, network lifetime, energy consumption, and packet delivery rate.
34
Sharma, Pankaj Kumar, R. K. Nagaria, and T. N. Sharma. "Enhancement of Power Efficiency in OFDM System by SLM with Predistortion Technique." Journal of Telecommunications and Information Technology, no. 4 (June 28, 2023): 86–91. http://dx.doi.org/10.26636/jtit.2011.4.1183.
Full textAbstract:
Orthogonal Frequency Division Multiplexing (OFDM) is considered as a strong candidate for future wireless communication because it is marked by its higher frequency multiplicity and greater immunity to multipath fading. However, the main drawback of OFDM is its high amplitude fluctuations measured by peak-to-average power ratio (PAPR), which leads to power inefficiency and requires expensive high power amplifier (HPA) with very good linearity. In this paper, we propose selected mapping (SLM) with predistortion technique to decrease the nonlinear distortion and to improve the power efficiency of the nonlinear HPA. In the proposed method SLM reduces the PAPR and improves the power efficiency, the predistorter improves the bit error rate (BER) performance of the system. The PAPR reduction is possible with SLM when compared with original OFDM. After reducing the PAPR with SLM the data goes into the HPA with and without predistorter. The BER performance curves of SLM method with or without predistorter shows that, predistorter operates more effectively in SLM method than original OFDM system. At 4 dB IBO (input backoff) the conventional method with predistorter achieves 1.8 dB SNR gain than conventional method without a predistorter and at 6 dB IBO the BER performance is towards the ideal linear amplifier. The proposed system will be evaluated for OFDM system in the presence of a nonlinear power amplifier.
35
Fan, Zuzhi. "Delay-constrained flooding in extremely low-duty-cycle sensor networks." International Journal of Distributed Sensor Networks 15, no. 3 (2019): 155014771984022. http://dx.doi.org/10.1177/1550147719840225.
Full textAbstract:
Flooding is a fundamental function for the network-wide dissemination of command, query, and code update in wireless sensor networks. However, it is challenging to enable fast and energy-efficient flooding in sensor networks with low-duty cycles because it is rare that multiple neighboring nodes wake up at the same time, making broadcast instinct of wireless radio unavailable. The unreliability of wireless links deteriorates the situation. In this work, we study the delay-constrained flooding problem in order to disseminate data packets to all nodes within given expected delivery delay. In particular, a transmission power control–based flooding algorithm is proposed to reduce the flooding delay in such low-duty-cycle sensor networks. According to the soft delay bound, each node can locally adjust its transmission power level. To alleviate transmission conflicts, the backoff method with transmission power adaptive mechanism has been proposed. Based on the large-scale simulations, we validate that our design can reduce flooding delay with small extra energy expenditure compared with conventional flooding schemes.
36
Hoque, Faika, and Sungoh Kwon. "An Emergency Packet Forwarding Scheme for V2V Communication Networks." Scientific World Journal 2014 (2014): 1–7. http://dx.doi.org/10.1155/2014/480435.
Full textAbstract:
This paper proposes an effective warning message forwarding scheme for cooperative collision avoidance. In an emergency situation, an emergency-detecting vehicle warns the neighbor vehicles via an emergency warning message. Since the transmission range is limited, the warning message is broadcast in a multihop manner. Broadcast packets lead two challenges to forward the warning message in the vehicular network: redundancy of warning messages and competition with nonemergency transmissions. In this paper, we study and address the two major challenges to achieve low latency in delivery of the warning message. To reduce the intervehicle latency and end-to-end latency, which cause chain collisions, we propose a two-way intelligent broadcasting method with an adaptable distance-dependent backoff algorithm. Considering locations of vehicles, the proposed algorithm controls the broadcast of a warning message to reduce redundant EWM messages and adaptively chooses the contention window to compete with nonemergency transmission. Via simulations, we show that our proposed algorithm reduces the probability of rear-end crashes by 70% compared to previous algorithms by reducing the intervehicle delay. We also show that the end-to-end propagation delay of the warning message is reduced by 55%.
37
Pang, Shengli, Zekang Li, Ziru Yao, Honggang Wang, Weichen Long, and Ruoyu Pan. "Research on the Evaluation and Prediction of V2I Channel Quality Levels in Urban Environments." Electronics 13, no. 5 (2024): 911. http://dx.doi.org/10.3390/electronics13050911.
Full textAbstract:
The present manuscript introduces a method for evaluating and forecasting the quality of vehicle-to-infrastructure (V2I) communication channels in urban settings. This method precisely classifies and predicts channel quality levels in V2I scenarios based on long-range (LoRa) technology. This approach aims to accurately classify and predict channel quality levels in V2I scenarios. The concept of channel quality scoring was first introduced, offering a more precise description of channel quality compared to traditional packet reception rate (PRR) assessments. In the channel quality assessment model based on the gated recurrent unit (GRU) algorithm, the current channel quality score of the vehicular terminal and the spatial channel parameters (SCP) of its location are utilized as inputs to achieve the classification of channel quality levels with an accuracy of 97.5%. Regarding prediction, the focus lies in forecasting the channel quality score, combined with the calculation of SCP for the vehicle’s following temporal location, thereby achieving predictions of channel quality levels from spatial and temporal perspectives. The prediction model employs the Variational Mode Decomposition-Backoff-Bidirectional Long Short-Term Memory (VMD-BO-BiLSTM) algorithm, which, while maintaining an acceptable training time, exhibits higher accuracy than other prediction algorithms, with an R2 value reaching 0.9945. This model contributes to assessing and predicting channel quality in V2I scenarios and holds significant implications for subsequent channel resource allocation.
38
Nowakowski, Karol, Michal Ptaszynski, and Fumito Masui. "MiNgMatch—A Fast N-gram Model for Word Segmentation of the Ainu Language." Information 10, no. 10 (2019): 317. http://dx.doi.org/10.3390/info10100317.
Full textAbstract:
Word segmentation is an essential task in automatic language processing for languages where there are no explicit word boundary markers, or where space-delimited orthographic words are too coarse-grained. In this paper we introduce the MiNgMatch Segmenter—a fast word segmentation algorithm, which reduces the problem of identifying word boundaries to finding the shortest sequence of lexical n-grams matching the input text. In order to validate our method in a low-resource scenario involving extremely sparse data, we tested it with a small corpus of text in the critically endangered language of the Ainu people living in northern parts of Japan. Furthermore, we performed a series of experiments comparing our algorithm with systems utilizing state-of-the-art lexical n-gram-based language modelling techniques (namely, Stupid Backoff model and a model with modified Kneser-Ney smoothing), as well as a neural model performing word segmentation as character sequence labelling. The experimental results we obtained demonstrate the high performance of our algorithm, comparable with the other best-performing models. Given its low computational cost and competitive results, we believe that the proposed approach could be extended to other languages, and possibly also to other Natural Language Processing tasks, such as speech recognition.
39
Feng, Xinglong, Yuzhong Zhang, Ang Gao, and Qiao Hu. "Research on AUV Multi-Node Networking Communication Based on Underwater Electric Field CSMA/CA Channel." Biomimetics 9, no. 11 (2024): 653. http://dx.doi.org/10.3390/biomimetics9110653.
Full textAbstract:
To address the issues of high attenuation, weak reception signal, and channel blockage in the current electric field communication of underwater robots, research on autonomous underwater vehicle (AUV) multi-node networking communication based on underwater electric field Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) channel was conducted. This article, first through simulation, finds that the Optimized Link State Routing (OLSR) protocol has a smaller routing packet delay time and higher reliability compared to the Ad Hoc On-Demand Distance Vector (AODV) protocol on underwater electric field CSMA/CA channels. Then, a 2FSK underwater electric field communication system was established, and dynamic communication experiments were carried out between two AUV nodes. The experimental results showed that within a range of 0 to 3.5 m, this system can achieve underwater dynamic electric field communication with a bit error rate of 0 to 0.628%. Finally, to avoid channel blockage during underwater AUV multi-node communication, this article proposes a dynamic backoff method for AUV multi-node communication based on CSMA/CA. This system can achieve dynamic multi-node communication of underwater electric fields with an error rate ranging from 0 to 0.96%. The research results have engineering application prospects for underwater cluster operations.
40
Sproat, Richard, Mahsa Yarmohammadi, Izhak Shafran, and Brian Roark. "Applications of Lexicographic Semirings to Problems in Speech and Language Processing." Computational Linguistics 40, no. 4 (2014): 733–61. http://dx.doi.org/10.1162/coli_a_00198.
Full textAbstract:
This paper explores lexicographic semirings and their application to problems in speech and language processing. Specifically, we present two instantiations of binary lexicographic semirings, one involving a pair of tropical weights, and the other a tropical weight paired with a novel string semiring we term the categorial semiring. The first of these is used to yield an exact encoding of backoff models with epsilon transitions. This lexicographic language model semiring allows for off-line optimization of exact models represented as large weighted finite-state transducers in contrast to implicit (on-line) failure transition representations. We present empirical results demonstrating that, even in simple intersection scenarios amenable to the use of failure transitions, the use of the more powerful lexicographic semiring is competitive in terms of time of intersection. The second of these lexicographic semirings is applied to the problem of extracting, from a lattice of word sequences tagged for part of speech, only the single best-scoring part of speech tagging for each word sequence. We do this by incorporating the tags as a categorial weight in the second component of a 〈Tropical, Categorial〉 lexicographic semiring, determinizing the resulting word lattice acceptor in that semiring, and then mapping the tags back as output labels of the word lattice transducer. We compare our approach to a competing method due to Povey et al. (2012).
41
Ma, Naji, and Ming Diao. "CoFi: Coding-Assisted File Distribution over a Wireless LAN." Symmetry 11, no. 1 (2019): 71. http://dx.doi.org/10.3390/sym11010071.
Full textAbstract:
The wireless channel is volatile in nature, due to various signal attenuation factors including path-loss, shadowing, and multipath fading. Existing media access control (MAC) protocols, such as the widely adopted 802.11 wireless fidelity (Wi-Fi) family, advocate masking harsh channel conditions with persistent retransmission and backoff, in order to provide a packet-level best-effort service. However, the asymmetry of the network environment of client nodes in space is not fully considered in the method, which leads to the decline of the transmission efficiency of the good ones. In this paper, we propose CoFi, a coding-assisted file distribution protocol for 802.11 based wireless local area networks (LANs). CoFi groups data into batches and transmits a random linear combination of packets within each batch, thereby reducing redundant packet and acknowledgement (ACK) retransmissions when the channel is lossy. In addition, CoFi adopts a MAC layer caching scheme that allows clients to store the overheard coded packets and use such cached packets to assist nearby peers. With this measure, it further improves the effective throughput and shortens the buffering delay when running applications such as bulk data transmission and video streaming. Our trace based simulation demonstrates that CoFi can maintain a similar level of packet delay to 802.11, but increases the throughput performance by a significant margin in a lossy wireless LAN. Furthermore, we perform a reverse-engineering on CoFi and 802.11 using a simple analytical framework, proving that they asymptotically approach different fairness measures, thus resulting in a disparate performance.
42
Tsvykh, Volodymyr, and Dmytro Nelipa. "Contemporary Theory of Public Administration in the USA: from Post-Bureaucracy Paradigm by B. Armajani and M. Barzeley to Postmodern Concept by Ch. Fox and H. Miller." Bulletin of Taras Shevchenko National University of Kyiv. Public Administration 11, no. 1 (2019): 53–61. http://dx.doi.org/10.17721/2616-9193.2019/11-6/7.
Full textAbstract:
The purpose of the article is to study comprehensively the content of the leading newest concepts in the field of public administration in the United States, identify their basic features, as well as clarify key characteristics of the contemporary American theory of public administration. The study used a set of logical methods (synthesis, analysis, inductive method, etc.) and such general scientific approaches as system, structural-functional and bibliographic ones. The article presents a systematic study of modern theory of public administration in the United States, analyzes the leading concepts, reveals their essence, principles and features. In particular, the principles of transition from bureaucratic to post-bureaucratic management, developed by B. Armajani and M. Barzeley, are analyzed; ten principles of entrepreneurial government by T. Gaebler and D. Osborne; the content of recursive practices, due to which the construction of reality takes place, including public and political, based on the scientific views of Ch. Fox and H. Miller; the essence of R. Denhardt's new civil service, which relies on the instruments of direct democracy and recognizes public activity above market instruments in the context of achieving public interests; main directions (managerial, political and legal) of integrated public administration by D. Rosenbloom; argumentation of P. Nutt and R. Backoff regarding the expediency of using strategic management in public administration. The key characteristics (trends) of the modern theory of public administration in the US are revealed, namely: debureaucratization; marketization; managerization; servicing; postmodernization. The preconditions and content of these tendencies are identified. The scientific novelty of the article is to conduct a thorough study of the main new concepts in the field of public administration in the United States, as well as to identify general relevant characteristics of the American theory of public administration. The practical significance of the article is related to the possibility of further use of its materials in the educational process, research and practical field, taking into account clear applied orientation of modern theory of public administration in the United States.
43
Vatri, Alessandro, and Barbara McGillivray. "Lemmatization for Ancient Greek." Journal of Greek Linguistics 20, no. 2 (2020): 179–96. http://dx.doi.org/10.1163/15699846-02002001.
Full textAbstract:
Abstract This article presents the result of accuracy tests for currently available Ancient Greek lemmatizers and recently published lemmatized corpora. We ran a blinded experiment in which three highly proficient readers of Ancient Greek evaluated the output of the CLTK lemmatizer, of the CLTK backoff lemmatizer, and of GLEM, together with the lemmatizations offered by the Diorisis corpus and the Lemmatized Ancient Greek Texts repository. The texts chosen for this experiment are Homer, Iliad 1.1–279 and Lysias 7. The results suggest that lemmatization methods using large lexica as well as part-of-speech tagging—such as those employed by the Diorisis corpus and the CLTK backoff lemmatizer—are more reliable than methods that rely more heavily on machine learning and use smaller lexica.
44
Bedi, Harpreet Singh. "Utilization of a Wireless Network Performing CSMA/CA with Random Backoff Algorithm." Journal of Physics: Conference Series 2327, no. 1 (2022): 012060. http://dx.doi.org/10.1088/1742-6596/2327/1/012060.
Full textAbstract:
Abstract Optimizing WLAN performance in IEEE 802.11 network with extremely different working environments is a difficult task. We must use a network that can provide the most benefits to its end-users to improve network strength and data transmission. To increase performance in this congested situation, we construct an adaptive backoff algorithm for the IEEE 802.11 DCF that enhances in congested network conditions, system throughput is improved, the collision probability is reduced, and good fairness is maintained. This paper deals with the utilization of networks for different backoff strategies for different network conditions. The results obtained were comparatively much better than the existing methods.
45
Jacobsen, K. S. "Methods of upstream power backoff on very high speed digital subscriber lines." IEEE Communications Magazine 39, no. 3 (2001): 210–16. http://dx.doi.org/10.1109/35.910609.
Full text
46
Lin, Cheng-Han, Ming-Hua Cheng, Wen-Shyang Hwang, Ce-Kuen Shieh, and Yu-Hang Wei. "A Rapidly Adaptive Collision Backoff Algorithm for Improving the Throughput in WLANs." Electronics 12, no. 15 (2023): 3324. http://dx.doi.org/10.3390/electronics12153324.
Full textAbstract:
In the 802.11 protocol, the fundamental medium access mechanism is called Distributed Coordination Function (DCF). In DCF, before making any transmission attempt, the nodes count down a timer with a value randomly selected from the Contention Window (CW) size. If the transmitted packet is involved in a collision, the node increases the CW size in an attempt to reduce the collision rate. Conversely, if the packet is transmitted successfully, the node reduces the CW size in order to increase the frequency of the transmission attempts. The growth or reduction in the CW size has a critical effect on the network performance. Several backoff algorithms have been proposed to improve the system throughput. However, none of these methods enable the system to approach the theoretical maximum throughput possible under DCF. Accordingly, this study proposes the Rapidly Adaptive Collision Backoff (RACB) algorithm, in which the CW size is adjusted dynamically based on the collision rate, as analyzed by a mathematical model. Notably, RACB requires no knowledge of the number of nodes in the wireless network and is applicable to both lightly loaded and heavily loaded networks. The numerical results show that, by adjusting the CW size such that the collision rate is maintained at a value close to 0.1, RACB enables the system throughput to approach the maximum DCF throughput in wireless environments containing any number of nodes.
47
Lisiecki, Bartosz. "Case Study: Advanced Solutions for Complex Drilling Challenges." Journal of Petroleum Technology 77, no. 01 (2025): 46–49. https://doi.org/10.2118/0125-0046-jpt.
Full textAbstract:
_ While renewable energy development continues to rise, the transition from traditional hydrocarbons is not progressing as rapidly as once expected, and oil and gas is still set to be a key player in the energy mix by mid-century. There has been significant development of green technologies and increased investments in wind, solar, and hydrogen energy, but the demand for hydrocarbons continues to grow, driven by global energy demand and the complexities of transitioning entire energy infrastructures. As the world aims to balance energy security with sustainability and affordability, it is clear hydrocarbons will continue to fulfil a critical role in meeting energy demand for the foreseeable future. It will take the next 27 years to move the energy mix from the present 80% fossil/20% non-fossil split to 48%/52% (DNV Energy Transition Outlook, 2023). Looming net-zero goals have placed operators under the microscope as they grapple with the challenge of maintaining profitability while adhering to environmental regulations. There are also increasing expectations from stakeholders and investors who are factoring environmental, social, and governance criteria into their investment decisions. Operators must now demonstrate not just financial viability, but also a commitment to sustainable practices. The drilling landscape in particular faces more complex challenges than ever before as it contends with fluctuating oil prices, more stringent environmental regulations, and increasingly complicated wells. While advances in exploration and drilling technologies have transformed the industry, unlocking previously inaccessible reserves and increasing production rates, the risk and technical difficulties associated with drilling operations have also escalated. As the sector strives to reduce its carbon footprint, advancements in drilling technologies are not only helping to minimize environmental impact, but also enabling more-efficient operations in increasingly complex well conditions. Understanding Stuck-Pipe Encounters Stuck-pipe incidents are a frequent challenge during drilling operations, often costing operators millions in remediation. The remediation process is complex, frequently requiring days or even weeks of nonproductive time (NPT) and resources that may not be immediately available. Such incidents can arise from various factors, including differential sticking which occurs when pressure differences between the mud column and formation fluids cause the drillstring to stick against the wellbore wall, creating a "stuck spot" that immobilizes the pipe. Packoff is also a common issue where accumulated cuttings, debris, or other materials around the drillstring create a blockage. In any situation, even if partial movement is possible, circulation and rotation are often not feasible. As each stuck-pipe scenario is unique, resolving it often necessitates a customized approach. Operators frequently find themselves constrained by a lack of available solutions, limiting their ability to respond effectively to a stuck-pipe situation. Jarring is a traditional stuck-pipe recovery method that uses mechanical or hydraulic tools to deliver sudden, high-impact forces to the drillstring to free the stuck pipe. Though this method can be effective, it is expensive and can take days or longer, which results in significant NPT to the project. If the stuck pipe cannot be resolved, the last resort is to perform a disconnect, traditionally requiring mobilization of a wireline crew to deploy an explosive charge, known as a backoff or string shot. The explosives must be detonated above the freepoint to sever the string and can leave an unpredictable fishing profile for future operation. This technique can be time-consuming, costly, and introduces a new set of risks into the operation by deploying third-party crews and transporting hazardous materials to the rigsite.
48
Chen, Wen Ning, Si Jia Li, Krishna Singh Bhandari, Shahid Aziz, Nodirbek Kosimov, and Dong Won Jung. "A Flow Stress Equation of AA5005 Aluminum Alloy Based on Fields-Backofen Model." Materials Science Forum 1078 (December 22, 2022): 3–10. http://dx.doi.org/10.4028/p-95f697.
Full textAbstract:
Tensile tests on AA5005 alloy were conducted on model MTS-810 tensile test machine during temperature 633-773 K and strain rate 0.0003-0.03 s-1. The flow stress–true strain curves were obtained. In order to analyze the flow stress behavior of aluminum AA5005 alloy, the phenomenological Fields-Backofen equation based on the fitting regression analysis was developed. The flow stress values calculated by the obtained model keep coincidence with experimental values. Eventually, the statistical analysis methods (correlation coefficient (R), average absolute relative error (AARE)) were adopted to examine the credibility of the established model. Results show that the R-value is 0.99592 and the AARE is 3.3128 %, which indicates the high fitting accuracy of the Fields-Backofen equation. Consequently, the Fields-Backofen model can describe the constitutive relationship of AA5005 alloy credibly.
49
Parras, Juan, and Santiago Zazo. "Repeated Game Analysis of a CSMA/CA Network under a Backoff Attack." Sensors 19, no. 24 (2019): 5393. http://dx.doi.org/10.3390/s19245393.
Full textAbstract:
We study a CSMA/CA (Carrier Sense Medium Access with Collision Avoidance) wireless network where some stations deviate from the defined contention mechanism. By using Bianchi’s model, we study how this deviation impacts the network throughput and show that the fairness of the network is seriously affected, as the stations that deviate achieve a larger share of the resources than the rest of stations. Previously, we modeled this situation using a static game and now, we use repeated games, which, by means of the Folk theorem, allow all players to have better outcomes. We provide analytical solutions to this game for the two player case using subgame perfect and correlated equilibria concepts. We also propose a distributed algorithm based on communicating candidate equilibrium points for learning the equilibria of this game for an arbitrary number of players. We validate approach using numerical simulations, which allows comparing the solutions we propose and discussing the advantages of using each of the methods we propose.
50
Niu, Yong, Zhonggang Sun, Yaoqi Wang, and Jiawei Niu. "Phenomenological Constitutive Models for Hot Deformation Behavior of Ti6Al4V Alloy Manufactured by Directed Energy Deposition Laser." Metals 10, no. 11 (2020): 1496. http://dx.doi.org/10.3390/met10111496.
Full textAbstract:
This work focuses on the hot deformation behavior and constitutive models of Ti6Al4V alloy manufactured by directed energy deposition laser (DEDL). The hot compression tests of DEDL Ti6Al4V alloy at deformation temperature of 700–950 °C and strain rate range of 0.001–1 s−1 were carried out. Three phenomenological models including modified Johnson–Cook model, modified Fields–Backofen model, and strain-compensated Arrhenius model were introduced to predict the flow stresses during uniaxial compression. The predictability of the three models is evaluated according to correlation coefficient, average absolute relative error, and average root mean square error. Traditional linear regression method (TLRM) and nonlinear regression analysis (NRA) were used to solve the constants of modified Johnson–Cook model and strain-compensated Arrhenius model, NRA was used to solve the constants of modified Fields–Backofen model. Compared with the TLRM, the NRA improves the accuracy of modified Johnson-Cook model, while has limited effect on that of strain-compensated Arrhenius model. The accuracy of modified Fields–Backofen model and strain-compensated Arrhenius model is higher than that of modified Johnson–Cook model.