Lower Average Delay Research Articles

Adaptive Avatar Handoff in the Cloudlet Network

In a traditional big data network, data streams generated by User Equipments (UEs) are uploaded to the remote cloud (for further processing) via the Internet. However, moving a huge amount of data via the Internet may lead to a long End-to-End (E2E) delay between a UE and its computing resources (in the remote cloud) as well as severe traffic jams in the Internet. To overcome this drawback, we propose a cloudlet network to bring the computing and storage resources from the cloud to the mobile edge. Each base station is attached to one cloudlet and each UE is associated with its Avatar in the cloudlet to process its data locally. Thus, the E2E delay between a UE and its computing resources in its Avatars is reduced as compared to that in the traditional big data network. However, in order to maintain the low E2E delay when UEs roam away, it is necessary to hand off Avatars accordingly-it is not practical to hand off the Avatars' virtual disks during roaming as this will incur unbearable migration time and network congestion. We propose the LatEncy Aware Replica placemeNt (LEARN) algorithm to place a number of replicas of each Avatar's virtual disk into suitable cloudlets. Thus, the Avatar can be handed off among its cloudlets (which contain one of its replicas) without migrating its virtual disk. Simulations demonstrate that LEARN reduces the average E2E delay. Meanwhile, by considering the capacity limitation of each cloudlet, we propose the LatEncy aware Avatar hanDoff (LEAD) algorithm to place UEs' Avatars among the cloudlets such that the average E2E delay is minimized. Simulations demonstrate that LEAD maintains the low average E2E delay.

Tg‐minimised bandwidth‐allocated scheme for multi‐subsystem‐based VPON in metro‐access optical network

Here, Tg-minimised bandwidth-allocated scheme is proposed for VPON supporting joint scheduling of multiple subsystems in metro-access optical network. To minimise guard time (Tg) in WDM-PON and TDM-PON, the Tg-transferred mechanism is introduced. To reduce the number of Tg in OFDM-PON, the subcarrier allocation algorithm based on the minimum number of Tg is proposed. To effectively utilise the network bandwidth resources, the bandwidth allocation based on matrix model is established. To increase the utilisation of wavelength, a dynamic-wavelength allocation mechanism is proposed. Finally, by the simulation, the effectiveness of Tg-minimised bandwidth-allocated scheme is demonstrated. Compared with other schemes, this scheme has at least 3% bandwidth utilisation improvement and lower average delay.

Emergency room closed reduction versus in situ splinting in the treatment of paediatric supracondylar humerus fractures.

PurposeDisplaced supracondylar humerus fractures are treated with open or closed reduction and percutaneous pinning. In 2012, our management of patients with a displaced fracture changed from closed reduction in the emergency department (ED) to in situ splinting prior to closed reduction and pinning in the operating room (OR). The purpose of this study was to investigate if outcomes or complications differ between these two management methods.MethodsPatients less than ten years old with a Gartland type II or III supracondylar humerus fracture between 2008 and 2016 were included. Cases of polytrauma were excluded. Radiographic outcomes were assessed at follow-up. The Fisher’s exact test was used for categorical variables and the Wilcoxon rank sums tests for continuous variables.ResultsIn all, 157 patients were included, 89 with reduction in the ED and 68 without. There was no significant difference between the groups related to demographic factors or fracture characteristics. Patients managed without reduction in the ED had a lower average delay from ED to OR compared with those treated with reduction (16 hours versus 22 hours, p < 0.005) and a shorter hospital length of stay (34 hours versus 40 hours, p < 0.005).ConclusionNo difference in complications or outcomes was found between patients with Type II or III supracondylar fractures treated initially with or without closed reduction in the ED. Patients treated without ED reduction were taken to the OR sooner and remained in the hospital for a shorter period of time. Splinting in situ reduces anaesthesia exposure without increasing postoperative complications or suboptimal outcomes.Level of EvidenceLevel III, retrospective comparative study

C2TCP: A Flexible Cellular TCP to Meet Stringent Delay Requirements

Since, current widely available network protocols/ systems are mainly throughput-oriented designs, meeting stringent delay requirements of new applications such as virtual reality and vehicle-to-vehicle communications on cellular network requires new network protocol/system designs. C2TCP is an effort toward that new design direction. C2TCP is inspired by in-network active queue management designs such as RED and CoDel and motivated by lack of a flexible end-to-end approach which can adapt itself to different applications’ QoS requirements without modifying any network devices. It copes with unique challenges in cellular networks for achieving ultra-low latency (including highly variable channels, deep per-user buffers, self-inflicted queuing delays, and radio uplink/downlink scheduling delays) and intends to satisfy stringent delay requirements of different applications while maximizing the throughput. C2TCP works on top of classic throughput-oriented TCP and accommodates various target delays without requiring any channel prediction, network state profiling, or complicated rate adjustment mechanisms. We have evaluated C2TCP in both real-world environment and extensive trace-based emulations and compared its performance with different TCP variants and state-of-the-art schemes including PCC-Vivace, Google’s BBR, Verus, Sprout, TCP Westwood, and Cubic. Results show that C2TCP outperforms all these schemes and achieves lower average delay, jitter, and 95th percentile delay for packets.

A Scheduling Method of Cross-Layers Optimization of Polling Weight for AOS Multiplexing

The core mechanism of Advanced Orbit System (AOS) mainly contains the packet channel multiplexing and the virtual channel multiplexing. The multiplexing efficiency and frame time directly affect the performance of the AOS and even the whole system. In this paper, in order to optimize AOS multiplexing performance, a scheduling method of cross-layers optimization of polling weight (CLOPW) is proposed. Different from single sublayer optimization such as the isochronous frame methods, the novel method focuses on factors related to AOS performance of two core sublayers, such as packet distribution, residual function, cache capacity, frame time, and multiplexing efficiency. We build a multiple factors framing model of finite buffer and deduce the formula of packet multiplexing efficiency based on the short correlation. Furthermore, we give the formula for the virtual channel utilization and delay of cross-layer optimization. The experimental results show that the novel scheduling method of cross-layers optimization of polling weight is higher utilization of virtual channel and lower average delay than the isochronous frame method.

Block-Based Carry Speculative Approximate Adder for Energy-Efficient Applications

In this brief, a low energy consumption block-based carry speculative approximate adder is proposed. Its structure is based on partitioning the adder into some non-overlapped summation blocks whose structures may be selected from both the carry propagate and parallel-prefix adders. Here, the carry output of each block is speculated based on the input operands of the block itself and those of the next block. In this adder, the length of the carry chain is reduced to two blocks (worst case), where in most cases only one block is employed to calculate the carry output leading to a lower average delay. In addition, to increase the accuracy and reduce the output error rate, an error detection and recovery mechanism is proposed. The effectiveness of the proposed approximate adder is compared with state-of-the-art approximate adders using a cost function based on the energy, delay, area, and output quality. The results indicate an average of 50% reduction in terms of the cost function compared to other approximate adders.

Dynamic Speed Control of Unmanned Aerial Vehicles for Data Collection under Internet of Things.

With the new advancements in flight control and integrated circuit (IC) technology, unmanned aerial vehicles (UAVs) have been widely used in various applications. One of the typical application scenarios is data collection for large-scale and remote sensor devices in the Internet of things (IoT). However, due to the characteristics of massive connections, access collisions in the MAC layer lead to high power consumption for both sensor devices and UAVs, and low efficiency for the data collection. In this paper, a dynamic speed control algorithm for UAVs (DSC-UAV) is proposed to maximize the data collection efficiency, while alleviating the access congestion for the UAV-based base stations. With a cellular network considered for support of the communication between sensor devices and drones, the connection establishment process was analyzed and modeled in detail. In addition, the data collection efficiency is also defined and derived. Based on the analytical models, optimal speed under different sensor device densities is obtained and verified. UAVs can dynamically adjust the speed according to the sensor device density under their coverages to keep high data collection efficiency. Finally, simulation results are also conducted to verify the accuracy of the proposed analytical models and show that the DSC-UAV outperforms others with the highest data collection efficiency, while maintaining a high successful access probability, low average access delay, low block probability, and low collision probability.

A Lightweight Autoscaling Mechanism for Fog Computing in Industrial Applications

Fog computing provides a more flexible service environment than cloud computing. The lightweight fog environment is suitable for industrial applications. In order to strengthen service scalability, container virtualization has been proposed and studied in recent years. It is vital to explore the tradeoff between service scalability and operating expenses. This paper integrates the hypervisor technique with container virtualization, and constructs an integrated virtualization (IV) fog platform for deploying industrial applications based on the virtual network function. This paper presents a fuzzy-based real-time autoscaling (FRAS) mechanism and implements it in the IV fog platform. The FRAS mechanism provides a dynamic, rapid, lightweight, and low-cost solution to the service autoscaling problem. Experimental results showed that the proposed FRAS mechanism yields a better service scale with lower average delay, error rate, and operating expenses compared to other autoscaling schemes.

A hybrid active queue management technique for QoS based unicasting protocols in MANETs

Mobile Ad hoc Networks (MANETs) is the interconnection of several self-energy dependent mobile nodes. It is one of the self-configured and infrastructure less network. In MANET the issues are security, Quality Of Services, Congestion etc. The major issue of MANET is to control the congestion. Congestion means the network capacity is larger than the no of packets transmitted across the network. In this paper, an effort has been made to evaluate and analyze the performance of the network by means of comparing two on-demand reactive routing protocols such as AODV [Ad-hoc On-demand Distance Vector] and DSR [Dynamic Source Routing] with each other along with also by comparing with DSDV [Destination Sequenced Distance Vector], which is a proactive routing protocol. The comparison is also being made under the light of two queue management techniques such as RED (Random Early Detection) and Droptail. A gateway discovery algorithm is being used by both AODV and DSR routing protocols, which uses the mechanism of connecting mobile nodes through gateway, however Bellman-Ford algorithm is being used by DSDV which uses the concept of including freedom from loops in the routing table. By means of simulation through NS-2 network simulator by varying the number of nodes, we observe that the performance differentials of AODV, DSR, and DSDV routing protocols are directed to foremost performance differentials to guarantee QoS for both of these protocols in RED and Droptail queue management techniques. There is a lot of queue management approach to minimize the congestion rate and transfer the data successfully to the destination. Two queue management techniques popularly used to manage queues in MANets are Active queue management and Passive queue management. Active queue management is widely used and RED is the most popular approach which gives low average delay, high throughput and lower packet drop rate. But RED algorithms have some drawback. So here we are using a hybrid approach, named as MRED by means of combining the features of both RED and ECN to overcome the drawbacks of RED.

On Removing Routing Protocol from Future Wireless Networks: A Real-time Deep Learning Approach for Intelligent Traffic Control

Recently, deep learning has appeared as a breakthrough machine learning technique for various areas in computer science as well as other disciplines. However, the application of deep learning for network traffic control in wireless/heterogeneous networks is a relatively new area. With the evolution of wireless networks, efficient network traffic control such as routing methodology in the wireless backbone network appears as a key challenge. This is because the conventional routing protocols do not learn from their previous experiences regarding network abnormalities such as congestion and so forth. Therefore, an intelligent network traffic control method is essential to avoid this problem. In this article, we address this issue and propose a new, real-time deep learning based intelligent network traffic control method, exploiting deep Convolutional Neural Networks (deep CNNs) with uniquely characterized inputs and outputs to represent the considered Wireless Mesh Network (WMN) backbone. Simulation results demonstrate that our proposal achieves significantly lower average delay and packet loss rate compared to those observed with the existing routing methods. We particularly focus on our proposed method's independence from existing routing protocols, which makes it a potential candidate to remove routing protocol(s) from future wired/ wireless networks.

Design of a supervisory controller for Cooperative Intersection Control using Model Predictive Control

Abstract The Cooperative Intersection Control (CIC) methodology ensures a safe, smooth traffic flow through an automated intersection by means of virtual platooning. In this paper, we address the design of a centralised supervisory controller for CIC which optimises the crossing sequence of vehicles. We propose an approach in which the intersection as a whole is modelled as a hybrid system, which evolves in both continuous-time and in discrete-time. This hybrid system model resembles a queueing system, and relates the entry of vehicles into the intersection to a measure of the delay of their travel through the intersection. We design a supervisory controller using Model Predictive Control (MPC), which aims to minimise the vehicles’ average delay by controlling their access to the intersection. A simulation study based on real-life data demonstrates the effectiveness of the MPC approach compared to a first-come-first-served (FCFS) policy and a conventional traffic light controller. This study shows that MPC achieves a faster transient response and a lower average delay, thereby increasing the throughput of the intersection.

A Novel Hybrid Access Protocol Based on Traffic Priority in Space-Based Network

The space-based network is made up of aircrafts, spacecrafts, and all kinds of satellites in different orbits, which is hierarchical and tridimensional. In this special hierarchical network, a suitable multiple access protocol is required if the satellites with high velocity sharing the limited channel resources reasonably. There are majority kinds of services and traffic required during the disaster or emergent times. Thus, a novel hybrid access protocol based on traffic priority in the space-based network is proposed, where the frequency-time division multiple access (F-TDMA) is introduced into the space-based network first, and some improvements by jointing the time-domain of F-TDMA to meet the specific requirements of the satellite users are in this paper. Moreover, different traffics in the space-based network are considered as well. The analysis and simulation results show that the hybrid access protocol can obtain a higher throughput and a lower collision probability with a lower average delay comparing with the traditional collision avoidance carrier sense multiple access (CSMA/CA).

Low-Latency Dynamic Wavelength and Bandwidth Allocation Algorithm for NG-EPON

Recently, the IEEE 802.3ca Task Force has been working to standardize the next-generation Ethernet passive optical network (NG-EPON) to fulfill future bandwidth demands. NG-EPON allows an optical network unit (ONU) transmission to be scheduled on multiple wavelength channels simultaneously. This will increase network capacity up to 100 Gb/s, along with flexibility, as any of the channels can be allocated from the four wavelength channels, each having a capacity of 25 Gb/s. However, it also raises many technical aspects to be considered while deciding on an optimum scheduling strategy for NG-EPON (100G-EPON) architecture. This paper proposes a dynamic wavelength and bandwidth allocation (DWBA) algorithm for NG-EPON to schedule upstream wavelength channels while providing a low average packet delay and catering frame resequencing problem. An online scheduling framework with gated service grant sizing policy has been demonstrated in this work. The proposed DWBA algorithm’s performance is evaluated in comparison with legacy interleaved polling with an adaptive cycle time (modified- IPACT) and recently proposed water-filling algorithmbased DWBA (WF-DBA) algorithms. Simulation results confirmed the validity of the proposed DWBA algorithm.

Cost-effective multicast routings in wireless mesh networks with multiple gateways

In order that multicast routing characteristics is reflected in wireless mesh networks, multicast routing metric is required for quantifying the multicast tree cost under wireless environments. This paper proposes a new multicast routing metric considering receiver's different characteristics of link quality on a wireless multicast channel as well as wireless multicast advantage. The proposed multicast-tree transmission ratio quantifying the multicast tree cost represents the product of the multicast transmission ratios of all nodes in the constructed multicast tree. In this paper, we also propose a wireless multicast routing which constructs the multicast tree by maximizing the multicast-tree transmission ratio in wireless mesh networks with multiple gateways and design the multicast routing protocol based on AODV protocol. Since the multicast tree by our wireless proposed routing algorithm contains the nodes having maximum multicast-node transmission ratio, our proposed multicast routing shows a higher delivery ratio and a lower average delay than original multicast AODV and the multicast routing with minimizing the forwarding nodes in its multicast tree. In comparison with other multicast routings, simulation results show that the proposed multicast heuristics maximizing the multicast-tree transmission ratio construct a cost-effective multicast tree in terms of its delivery ratio, average delay, and required network resources.

SIRC: A Secure Incentive Scheme for Reliable Cooperative Downloading in Highway VANETs

In this paper, we propose a secure incentive scheme to achieve fair and reliable cooperative (SIRC) downloading in highway vehicular ad hoc networks (VANETs). SIRC can stimulate vehicle users to help download-and-forward packets for each other and consists of cooperative downloading and forwarding phase. During the cooperative downloading phase, SIRC utilizes “virtual checks” associated with the designated verifier signature to ensure fair and secure cooperation. Meanwhile, to minimize the payment risk of the client vehicle, partial prepayment strategy is adopted, i.e., the vehicles involved in downloading packets can only obtain part of the check before the client vehicle confirms the packet reception. During the cooperative forwarding phase, a profit-sharing model associated with an aggregating Camenisch–Lysyanskaya (CL) signature can stimulate cooperation and reduce the authentication overhead. In addition, we develop a reputation system to encourage cooperation and punish malicious vehicles. The aggregating CL signature and the symmetric cryptosystem are applied to resist various attacks, including injection/removing attack, free riding attack, submission refusal attack, and denial of service attacks. Extensive simulation results are given to show that the proposed SIRC can achieve a high download success rate and low average download delay with moderate cryptographic computation and communication overhead.

Multicast tree construction: a nodes' relative leaving probability algorithm based on NICE in ALM

Due to the existing defects of IP multicast, which is difficult to be expanded and managed, the researchers put forward application layer multicast. Real-time transmission is an important application field of application layer multicast technology. However, it has strict requirements for the network delay. This paper firstly analyses the delays composition of application layer multicast and the rule of the distribution of the nodes' session time. And then, according to these factors, we propose a multicast tree construction algorithm concerning the nodes' relative leaving probability based on NICE NRLP-NICE. NRLP-NICE compares the distance among nodes and selects the centre nodes as the leaders to build new multicast tree. Meanwhile, NRLP-NICE switches the rule of the distribution of nodes' session time into nodes' relative leaving probability. NRLP-NICE is simulated by Omnet++. The simulated results show that NRLP-NICE has low control costs and average delay error percentage compared to NICE.

A routing defense mechanism using evolutionary game theory for Delay Tolerant Networks

Delay Tolerant Networks (DTNs) often suffer from intermittent disruption due to factors such as mobility and energy. Though lots of routing algorithms in DTNs have been proposed in the last few years, the routing security problems have not attracted enough attention. DTNs are still facing the threats from different kinds of routing attacks. In this paper, a general purpose defense mechanism is proposed against various routing attacks on DTNs. The defense mechanism is based on the routing path information acquired from the forwarded messages and the acknowledgment (ACK), and it is suitable for different routing schemes. Evolutionary game theory is applied with the defense mechanism to analyze and facilitate the strategy changes of the nodes in the networks. Simulation results show that the proposed evolutionary game theory based defense scheme can achieve high average delivery ratio, low network overhead and low average transmission delay in various routing attack scenarios. By introducing the game theory, the networks can avoid being attacked and provide normal transmission service. The networks can reach evolutionary strategy stable (ESS) under special conditions after evolution. The initial parameters will affect the convergence speed and the final ESS, but the initial ratio of the nodes choosing different strategies can only affect the game process.

Robust Path Construction for Reliable Data Transmissions in Node Disjoint Multipath Routing

Wireless Sensor Networks (WSNs) are prone to node breakdowns due to energy constraints, which contribute to frequent topology changes. Moreover, since sensor nodes have restricted transmission range, multiple hops are needed by the node in order to forward the packets from one node to the other and this raises very challenging issues when designing routing protocols. Most of the proposed single path routing schemes use a periodic low-rate flooding of data in order to recover from path failures, which causes higher consumption in sensor node resources. So multipath routing is an optimal approach to enhance the network lifetime. In this paper, a robust path construction for a reliable data transmission in node-disjoint multipath routing (RNDMR) is proposed for WSNs. The proposed RNDMR has the ability to provide a low overhead path construction as well as provide data transmission reliability by using XOR-based coding algorithm, which entails low utilization of resources, such as low storage space and lesser computing power. In the proposed RNDMR, the procedure involves the splitting up of all transmitted messages into many different segments of equal size, before adding the XOR-based error correction codes and distributing it among multiple paths simultaneously in order to boost reliable data transmission and to be assured that the essential fragment of the packet arrives at the sink node without any additional consumption of energy and undue delay. By using simulations, the performance of RNDMR was assessed and compares it with ReInForm routing. The results illustrate that RNDMR attains low energy consumption, records low average delay and routing overhead, as well as increased packet delivery ratio when compared with ReInForm Routing.

Secure and Privacy Preserving Protocol for Cloud-Based Vehicular DTNs

Cloud-assisted vehicular delay tolerant networks (DTNs) have been utilized in wide-ranging applications where a continuous end-to-end connection is unavailable, the message transmission is fulfilled by the cooperation among vehicular nodes and follows a store-carry-and-forward manner, and the complex computational work can be delegated to the disengaged vehicles in the parking lots which constitute the potential vehicular cloud. Nevertheless, the existing incentive schemes as well as the packet forwarding protocols cannot well model continuous vehicle collaboration, resist vehicle compromise attacks and collusion attacks, leaving the privacy preservation issues untouched. In this paper, a novel threshold credit-based incentive mechanism (TCBI) is proposed based on the modified model of population dynamics to efficiently resist the node compromise attacks, stimulate the cooperation among intermediate nodes, maximize vehicular nodes’ interest, and realize the fairness of possessing the same opportunity of transmitting packets for credits. Then, a TCBI-based privacy-preserving packet forwarding protocol is proposed to solve the open problem of resisting layer-adding attack by outsourcing the privacy-preserving aggregated transmission evidence generation for multiple resource-constrained vehicles to the cloud side from performing any one-way trapdoor function only once. The vehicle privacy is well protected from both the cloud and transportation manager. Finally, formal security proof and the extensive simulation show the effectiveness of our proposed TCBI in resisting the sophisticated attacks and the efficiency in terms of high reliability, high delivery ratio, and low average delay in cloud-assisted vehicular DTNs.

Intelligent Inter-domain Connection Provisioning for Multi-domain Multi-vendor Optical Networks

We propose a semicentralized semidistributed network architecture based on active stateful path computation elements (PCEs) to intelligently provide end-to-end inter-domain connections in multi-domain optical transport networks supplied by different equipment vendors. A novel control entity, called an inter-domain communication control and management element (ICCME), is introduced into the architecture to achieve flexible distributed inter-domain control and centralized intra-domain management by integrating with &#x201C;proactive&#x201D; and &#x201C;reactive&#x201D; stateful capabilities. Inter-domain routing and signaling are completed with the collaboration of multiple ICCMEs in a peer-to-peer manner, which decentralizes highly intensive computation and signaling to multiple ICCMEs. In addition, we put forward a unified inter-domain communication protocol to eliminate the differences in private signaling message formats of various vendors&#x2019; domains. We report a successful field trial of providing inter-domain connections across a commercial three-domain three-vendor optical transport network. Also, experimental results indicate that ICCME-based architecture performs better than previous schemes in terms of scalability, i.e., low average routing load of control entities and low average delay in establishing inter-domain connections, but results in higher message overhead and blocking probability.