Backoff Algorithm Research Articles

The energy-efficient MDA-SMAC protocol for wireless sensor networks

Nodes in original S-MAC protocol just can visit the channel in the scheduling and listening stage. The working schema may result in data latency and high conflict. To solve those above problems, we split scheduling duty into multiple micro-duties. By using different micro-dispersed contention channel, the sensor nodes reduce the collision probability of the data. Aiming at detecting the fixed duty cycle in S-MAC protocol, on the basis of the micro-duty and buffer queue length, this paper presents an adaptive duty cycle and back-off algorithm. While using different back-off algorithm with different duty cycles, sensor node Fast-Binary Exponential Backoff and Conflict-Avoid-Binary exponential Backoff algorithm separated are applied to reduce data latency further reduce the conflict probability. Combining both of the improvements, we propose a modified S-MAC protocol. Comparing the performance of S-MAC protocol and Division-Multiple Access-Media Access Control (MDA-SMAC) protocol on the NS-2 simulation platform, the results show that MDA-SMAC protocol performs better in terms of energy consumption, latency, and effective throughput than S-MAC protocol

Optimized Adaptive Back off Algorithm for Static and Mobile Wireless Ad hoc Networks

In wireless ad hoc networks with stationary and portable nodules situation, planning a backoff procedure is decisive to evade impact and to increase the act of nodules. Majority of the Medium Access Control (MAC) etiquettes intended for ad hoc networks take up stationary nodules situation. In this paper, an Optimized Adaptive Backoff Algorithm (OABA) is proposed for static and mobile wireless ad hoc networks. In this algorithm, during the back off stage, the type of node is determined as static or mobile. For mobile nodes, their residence time is determined in addition to their priority. Then optimized adaptive backoff algorithm is applied, by checking the type of node. Simulation results have shown that OABA achieves higher delivery ratio with minimized delay, packet drop and energy consumption.

Performance Analysis of Different Channel Allocation Schemes of Random Access (RA) MAC Protocol with Back-Off Algorithm (BOA)

Cognitive radio technology is an effective method to improve the utilization and efficiency of radio spectrum. Cognitive radio technology solves spectrum scarcity problem by allowing cognitive users to use spectrum holes when primary users are absent. Cognitive radio networks are classified according to the infrastructure into: (A) centralized cognitive radio networks and (B) cognitive radio ad-hoc networks. The cognitive media access control (MAC) protocols are the master key of designing cognitive radio network. These allow cognitive users to identify and use the available frequency spectrum in a manner constrains the levels of interference to the primary users. Cognitive radio MAC protocols can be classified into: (A) random access control protocol (B) time slotted control protocols (C) hybrid protocols. In this paper, the dynamic open spectrum sharing (DOSS) MAC protocol is proposed as an example for random access control protocol. Due to the collision among users, the network throughput will be reduced. In order to enhance the performance of DOSS protocol, a back-off algorithm (BOA) will be executed and analyzed to enhance the network throughput. An optimum number of data retransmissions that decrease blocking and dropping ratio are investigated. Moreover, two accessing channels techniques for the proposed algorithm will be presented: fixed channel allocation (FCA) and dynamic channel allocation (DCA) schemes. DCA scheme allows to users to choose the control channel in a dynamic manner. The dynamic behavior decreases the limitation of control channel saturation. So, it can increase the network throughput. The performance analysis of the FCA and DCA schemes for the proposed protocol will be simulated. Finally, the performance analysis of DCA scheme of DOSS mac protocol with BOA will be investigated.

PRIORITY BASED OPTIMIZED BACKOFF ALGORITHM FOR COLLISION AVOIDANCE IN WIRELESS AD HOC NETWORKS

In wireless ad hoc networks, designing a backoff (BO) algorithm is crucial to avoid collision and to enhance the network throughput. The majority of current MAC protocols have altered the Binary Exponential Backoff (BEB) algorithm to provide relative priority among multiple traffic classes. But the BO interval should be adaptively altered depending on the residual energy and traffic load of contending nodes. Hence this paper designs a priority based optimized BO (PBOB) algorithm for collision avoidance. This algorithm works in standard IEEE 802.11 MAC protocol in which the contending nodes are prioritized based on their residual energy, load and traffic type. Then during contention period, the backoff interval is adaptively adjusted based on the priority of each contending node. By simulation results, it has been show that the PBOB algorithm has better packet delivery ratio and throughput with reduced energy consumption.

Channel Status based Contention Algorithm for Non-safety Applications in IEEE802.11p Vehicular Network

Abstract The purpose of a vehicular network is to provide better safety and infotainment services to the users through an effective communication. To attain this, IEEE802.11p standard is developed with Enhanced Distributed Channel Access (EDCA) contention-based priority-oriented medium access method. In this method, the backoff algorithm selects the Contention Window (CW) size randomly from the range (0, CW). The lower bound for this range is always fixed as zero, irrespective of the backoff stages and congestion in the network. This causes the backoff procedure to select the smaller value even when the network is heavily congested thus increasing collisions and congestion. To resolve this unbalanced backoff interval problem, this paper proposes a Channel Status based Contention Algorithm (CSCA) which regulates the backoff interval based on the number of retransmission attempts by packets and vehicle density for the non-safety applications. The network simulation is carried out using NS3 along with SUMO for highway traffic and results are shown that the proposed algorithm outperforms the default EDCA and Adaptive EDCA (A-EDCA) methods in terms of packet collision rate, throughput and delay.

Cross-layer based Mobility-Aware Backoff Algorithm for Collision Avoidance in Wireless Ad hoc Networks

Cross-layer based Mobility-Aware Backoff Algorithm for Collision Avoidance in Wireless Ad hoc Networks

Vehicle density and signal to noise ratio based broadcast backoff algorithm for VANETs

In a realistic vehicular ad-hoc networks (VANETs), a beacon frame loss is usually caused by collision or channel noise. In this paper, we propose an effective scheme for the periodic broadcast on the control channel in VANETs. Instead of the fixed contention window, in our scheme, the contention window is dynamically adjusted. For a certain vehicle density, the best contention window size is obtained by maximizing the transmission success rate in a unit time slot. On this basis, the channel quality is evaluated according to the signal to noise ratio (SNR), and the same frame will be transmitted twice under certain conditions. Simulation results show that the proposed vehicle density and SNR based broadcast algorithm outperforms the traditional broadcast methods.

An Insight of Backoff Algorithms in Wireless Networks

The IEEE 802.11 MAC is liable for the scheme of channel accessing. It decides the performance of the WLAN and DCF is the central strategy. Stations that need to get to the divert may partake in a disseminated manner by means of CSMA/CA in the MAC layer. Packet collision can’t be totally avoided because of the nodes which are in scattered manner. MAC layer uses a BEB scheme for CA (collision avoidance).. Nodes are experiencing a collision in common channel in IEEE 802.11 and must have to backoff for a arbitrary time and selected consistently from CW. The contention window is maintained dynamically by BO algorithms. Network performance is decreased due to a sudden change in window size. Different existing algorithms for backoff and comparision among the algorithms are shown in the manuscript.

A Novel Back-off Algorithm for Integration of Scheduling and Control of Batch Processes under Uncertainty

A novel decomposition algorithm for the integration of scheduling and control of multiproduct, multiunit batch processes under stochastic parameter uncertainty is presented. This iterative algorithm solves a scheduling and dynamic optimization problem around a nominal point while approximating uncertainty through back-off terms, embedded in the operational process constraints. Monte Carlo simulations are performed to propagate uncertainty and to evaluate dynamic feasibility; statistical information is drawn from these simulations to update the back-off terms. Convergence of the algorithm results in a set of scheduling and control decisions that aim to keep the plant dynamically feasible under the effect of uncertainty up to a user-defined tolerance criterion. The proposed algorithm is shown to be successfully applied to a multiproduct, multiunit batch plant under the effects of different probability density functions in the uncertain parameters. The algorithm’s performance is gauged against a fully integr...

Adaptive Transmission Control for Uplink/Downlink Fairness in Unsaturated CSMA Networks

In carrier sensing multiple access (CSMA)-based IEEE 802.11 systems, it is important for an access point (AP) and multiple stations to have access opportunity proportional to their traffic load, ensuring fairness between uplink (UL) and downlink (DL). This letter proposes an adaptive backoff algorithm based on estimation for the UL/DL backlog sizes in unsaturated CSMA networks. Based on the UL/DL backlog estimation, the optimal UL and DL transmission probabilities are derived as a function of the UL/DL backlog sizes. The proposed algorithm not only improves the overall system performance but also provides the near-perfect UL/DL fairness.

Improved MAC layer protocol of Wifi for satellite network.

With the development and universal application of satellite technology, an important way to expand the function of satellites is setting up inter-satellite networks to make them work together. Traditional satellite networking methods generally adopt a fixed time slot allocation method, which is not suitable for small satellite groups with low latency and high throughput requirements. In order to solve this problem, it has been proposed to apply the traditional Wifi protocol in satellite networking. As there are differences between satellite networks and terrestrial networks, it’s necessary to improve the traditional 802.11 protocol. The Media Access Control (MAC) protocol in 802.11 is improved in this paper, which mainly includes the adaptive algorithm of maximum contention window size and the growth algorithm of Contention Window (CW) size. The maximum contention window is adjusted according to the conflict state of the current network, which makes the network accommodate more satellite nodes. The CW growth algorithm improves the traditional Binary Exponential Back-off (BEB) algorithm, where the CW is designed according to the priority of the data frame or the network load. In this way, high-priority satellite accusation information will have higher reliability or tolerate greater network load.

On simple back-off in unreliable radio networks

In this paper, we study local and global broadcast in the dual graph model, which describes communication in a radio network with both reliable and unreliable links. Existing work proved that efficient solutions to these problems are impossible in the dual graph model under standard assumptions. In real networks, however, simple back-off strategies tend to perform well for solving these basic communication tasks. We address this apparent paradox by introducing a new set of constraints to the dual graph model that better generalize the slow/fast fading behavior common in real networks. We prove that in the context of these new constraints, simple back-off strategies now provide efficient solutions to local and global broadcast in the dual graph model. We also precisely characterize how this efficiency degrades as the new constraints are reduced down to non-existent, and prove new lower bounds that establish this degradation as near optimal for a large class of natural algorithms. We conclude with an analysis of a more general model where we propose an enhanced back-off algorithm. These results provide theoretical foundations for the practical observation that simple back-off algorithms tend to work well even amid the complicated link dynamics of real radio networks.

Underwater wireless optical communication multi-tokens random backoff neighbor discovery method.

The cooperation of multiple pieces of equipment can greatly improve the efficiency of work when performing tasks underwater. Networking communication is a crucial technology for underwater cooperation. Wireless optical communication technology has many advantages in underwater networking communication. Neighbor discovery is a key part of networking between nodes, and it is required to establish links quickly. This paper combines the token mechanism with the random backoff mechanism and proposes a multi-tokens random backoff (MTRB) neighbor discovery method for underwater wireless optical communication. Simulation and analysis of the MTRB method show that the method has high neighbor discovery efficiency. When the parameters are selected properly, the rate of neighbor discovery by the MTRB method is increased by about 50% compared with the single token and the random backoff algorithm.

Multichannel MAC protocol with dynamic backoff contention for distributed cognitive radio networks

Multiuser access is a critical issue in distributed cognitive radio networks (DCRNs), as the collisions among the competing secondary users (SUs) may decrease the network throughput significantly. In order to reduce the collisions, we propose a dynamic backoff algorithm to find an optimal backoff contention window to maximize the network throughput and reduce the channel access delay. Based on the proposed algorithm, a multichannel medium access control (MAC) protocol with dynamic backoff contention (MMAC-DB) is designed. In this protocol, the time duration of each channel is divided into four phases: idle, sensing-sharing, contention, and data transmission. The dynamic backoff algorithm is implemented in the contention phase. Moreover, a duration tradeoff is made between the data transmission phase and the contention phase. The effectiveness of the proposed protocol is examined by extensive simulations, which shows that the proposed protocol can enhance the throughput and reduce the channel access delay.

Congestion Control in CoAP Observe Group Communication.

The Constrained Application Protocol (CoAP) is a simple and lightweight machine-to-machine (M2M) protocol for constrained devices for use in lossy networks which offers a small memory capacity and limited processing. Designed and developed by the Internet Engineering Task Force (IETF), it functions as an application layer protocol and benefits from reliable delivery and simple congestion control. It is implemented for request/response message exchanges over the User Datagram Protocol (UDP) to support the Internet of Things (IoT). CoAP also provides a basic congestion control mechanism. In dealing with its own congestion, it relies on a fixed interval retransmission timeout (RTO) and binary exponential backoff (BEB). However, the default CoAP congestion control is considered to be unable to effectively perform group communication and observe resources, and it cannot handle rapid, frequent requests. This results in buffer overflow and packet loss. To overcome these problems, we proposed a new congestion control mechanism for CoAP Observe Group Communication, namely Congestion Control Random Early Detection (CoCo-RED), consisting of (1) determining and calculating an RTO timer, (2) a Revised Random Early Detection (RevRED) algorithm which has recently been developed and primarily based on the buffer management of TCP congestion control, and (3) a Fibonacci Pre-Increment Backoff (FPB) algorithm which waits for backoff time prior to retransmission. All the aforementioned algorithms were therefore implemented instead of the default CoAP mechanism. In this study, evaluations were carried out regarding the efficiency of the developed CoCo-RED using a Cooja simulator. The congestion control mechanism can quickly handle the changing behaviors of network communication, and thus it prevents the buffer overflow that leads to congestions. The results of our experiments indicate that CoCo-RED can control congestion more effectively than the default CoAP in every condition.

CA-CWA: Channel-Aware Contention Window Adaption in IEEE 802.11ah for Soft Real-Time Industrial Applications.

In 2016, the IEEE task group ah (TGah) released a new standard called IEEE 802.11ah, and industrial Internet of Things (IoT) is one of its typical use cases. The restricted access window (RAW) is one of the core MAC mechanisms of IEEE 802.11ah, which aims to address the collision problem in the dense wireless networks. However, in each RAW period, stations still need to contend for the channel by Distributed Coordination Function and Enhanced Distributed Channel Access (DCF/EDCA), which cannot meet the real-time requirements of most industrial applications. In this paper, we propose a channel-aware contention window adaption (CA-CWA) algorithm. The algorithm dynamically adapts the contention window based on the channel status with an external interference discrimination ability, and improves the real-time performance of the IEEE 802.11ah. To validate the real-time performance of CA-CWA, we compared CA-CWA with two other backoff algorithms with an NS-3 simulator. The results illustrate that CA-CWA has better performance than the other two algorithms in terms of packet loss rate and average delay. Compared with the other two algorithms, CA-CWA is able to support industrial applications with higher deadline constraints under the same channel conditions in IEEE 802.11ah.

Is Cognitive Radio an Opportunity to Improve the Performance of the IEEE 802.15.4 in Mobile e-Health Scenarios?

In the last decade, the number of wireless devices in the 2.4 GHz band has grown rapidly, such as WiFi, Bluetooth, ZigBee and IEEE 802.15.4. Because of the technologies and the number of devices continues increasing, the probability of spectrum saturation is high. The implementation of the Cognitive Radio (CR) proposes an alternative to reuse spectrum, in order to guarantee a peaceful coexistence with the other technologies operating in the same frequency band. The contribution of this paper can be listed as follows: i) proposes a study to verify the performance of the IEEE 802.15.4 standard in mobile e-Health scenarios and its capacity with multiple mobile source nodes in the network, in intention to evaluate its capacities to support cognitive radio directives, through an OMNeT++ simulation and physical embedded devices test bed, both results showed a high correlation. The novelty of this study is the introduction of mobile nodes (which simulate mobile patients inside one hop WSN topology). ii) The results obtained in section IV B, show that in the best case of the study, was obtained a 14.5% packets losses by collisions with five mobile source nodes, which is 13.5% greater than the 1% allowed by the standard. In addition, the percentage of packets lost by the backoff algorithm has an important increase from eight up to ten mobile source nodes, demonstrating the impact of the number of nodes has on the performance of the network. iii) Concluding, the implementation of CR will improve the performance in WSN IEEE 802.15.4, through dynamic multi-channel operation avoiding the spectrum saturation problem.

A Wake-up Radio protocol based on adaptive backoff and dynamic CCA in Wireless Sensor Networks

Asynchronous wake-up communication based on wake-up radio (WuR) is an important energy-saving method in wireless sensor networks (WSNs). The Clear Channel Assessment (CCA) is a major section of energy consumption in asynchronous WuR-based nodes. The traditional static backoff will lead to longer waiting delay which increase the energy consumption of successful sending packets when the network traffic becomes heavier. So a protocol DNAP-WuR is proposed to solve these problems in the terminal initiated (TI) communication mode. It first implements the dynamic CCA optimization (DCO) mechanism which allows nodes to interrupt the CCA process as soon as the channel is busy. Nodes can go to sleep faster during busy periods, instead of performing CCA detection until the counter is reduced to zero. And then, the WuR based adaptive logarithm backoff (WALB) algorithm is used to predict the backoff time sequences which can reduce the WuC’s collision probability and decrease the energy consumption according to the nodes number and the packet arrival rate. In order to avoid the phenomenon that the backoff window size is reduced too fast or increased slowly after packets transmitted. Compared with CSMA-WuR protocol, the DNAP-WuR has 4.6% reduction in energy consumption and 12.1% promotion in throughput.

Analytical Available Bandwidth Estimation in Wireless Ad-hoc Networks Considering Mobility in 3-Dimensional Space

Estimation of available bandwidth for ad hoc networks has always been open and active challenge for the researchers. A lot of literature is proposed in the last 20 years to evaluate the residual bandwidth. The main objective of the work being admission of new flow in the network with the constraint that any existing current transmission is not affected. One of the prime factors affecting the estimation process is the collision among packets. These collisions trigger the backoff algorithm that leads to wastage of the usable bandwidth. Although a lot of state of art solutions were proposed, but they suffer from various flaws and shortcoming. Other factor contributing to the inaccuracy in existing solution is the mobility of nodes. Node mobility leads to instability of links leading to data losses and delay which impact the bandwidth. The current paper proposes an analytical approach named Analytical Available Bandwidth Estimation Including Mobility (AABWM) to estimate ABW on a link. The major contributions of the proposed work are: i) it uses mathematical models based on renewal theory to calculate the collision probability of data packets which makes the process simple and accurate, ii) consideration of mobility under 3-D space to predict the link failure and provides an accurate admission control. Extensive simulations in NS-2 are carried out to compare the performance of the proposed model against the existing solutions.

Experiencing LoRa Network Establishment on a Smart Energy Campus Testbed

The fundamental properties of long-range (LoRa) performance have been revealed by previous research, but advanced issues remain unresolved. This paper tackles three technical challenges that are confronted when establishing a LoRa network on a smart energy campus testbed in Korea. First, the communication range of LoRa in a combined indoor and outdoor environment has yet to be determined. To address this problem, this study builds a LoRa testbed from which we measure the propagation properties of radio signals in a combined environment. Then, we establish a simplified path loss model for LoRa PHY and compute the communication range. Next, national regulations enforce the use of the Listen-Before-Talk (LBT) scheduling scheme, but its performance has never been examined. This paper enumerates the impacts of LBT, threshold values, back-off algorithms, and application parameters on LoRa Medium Access Control (MAC) performance. Last, the application parameters required by the smart energy scenario influence LoRa performance, but their impacts have been scarcely reported. Based on the application parameters and experimental results, this paper proposes a strategy to deploy LoRa gateway(s) and nodes on the campus. To the best of the authors’ knowledge, this is the first work that considers performance issues when establishing a LoRa network on a real-world application testbed.