Forwarding Delay Research Articles

Static Differential NCL Gates: Toward Low Power

This brief proposes a new topology for implementing differential null convention logic gates. The new topology relies on the static implementation of conventional versions of such gates and uses a set of extra minimum-sized transistors to cut off connections to the power rails in specific nodes while the gate is switching. It shows that albeit the extra transistors adding cost in area, they enable solid savings in dynamic and static power and improve transition delays. Electrical simulation results for a Kogge-Stone adder case study led to savings of 67.3% in dynamic power, 61.9% in static power, 67.2% in energy per operation, and 8.9% in forward propagation delay, when compared with a state-of-the-art differential topology.

Controlling Race Conditions in OpenFlow to Accelerate Application Verification and Packet Forwarding

OpenFlow is a Software Defined Networking (SDN) protocol that is being deployed in many network systems. SDN application verification takes an important role in guaranteeing the correctness of the application. Through our investigation, we discover that application verification can be very inefficient under the OpenFlow protocol since there are many race conditions between the data packets and control plane messages. Furthermore, these race conditions also increase the control plane workload and packet forwarding delay. We propose Attendre, an OpenFlow extension, to mitigate the ill effects of the race conditions in OpenFlow networks. We have implemented Attendre in NICE (a model checking verifier), Open vSwitch (a software virtual switch), and NOX (an OpenFlow controller). Experiments show that Attendre can reduce verification time by several orders of magnitude, and significantly reduce TCP connection setup time.

CAR: Coding-Aware Opportunistic Routing for Unicast Traffic in Wireless Mesh Networks

An intermediate node in an inter-flow network coding scheme needs to know exactly which are the previous hop and next hop of a packet before coding. It is difficult to incorporate inter-flow network coding into opportunistic routing (OR) because the next hop of a packet in OR can't be determined in advance. Coding-aware opportunistic routing (CAR) is proposed in this paper to address this problem on fixed wireless mesh networks (WMNs). Meanwhile, it aims to maximize the number of native packets coded in each single transmission. It dynamically selects a route for a given flow according to the real-time coding opportunities. There are no control packets in CAR, which greatly reduces the overhead costs. CAR gives the coded packet that consists of a larger number of native packets with a smaller forwarding delay. The forwarder with the largest number of native packets coded together is ultimately selected to send data. Simulations demonstrate that CAR achieves significantly better throughput gains and derives a reasonable end-to-end delay in both cross topology and mesh topology under both transmission control protocol (TCP) and user datagram protocol (UDP) traffic, as explained below. CAR achieves more than 35 % throughput improvement under TCP traffic and more than 15 % throughput improvement under UDP traffic, compared to other state-of-art protocols in cross topology, respectively. CAR also provides a several-fold increase in throughput in a large scale network (mesh topology). In a word, CAR significantly improves network performance of a WMN.

Adaptive message forwarding for avoiding broadcast storm and guaranteeing delay in active safe driving VANET

Active safe driving has been extensively studied to avoid vehicle accidents or traffic jam by using the inter-vehicle communications (IVC) in Vehicular Adhoc NETworks and Intelligent Transport Systems (ITSs). In IVC, the shared emergency message certainly brings several advantages: achieving active safe driving, avoiding vehicle accidents, avoiding blind-driving in traffic jam, balancing vehicle traffic loads, etc. However, the shared (emergency) message always forwarded through broadcasting that suffers from broadcast storm and flooding of messages, and then yields a long forwarding delay and degrades the synchronization interval of the application of adaptive cruise control. Thus, to guarantee real-time forwarding of emergency messages (EMs) needs to be addressed for successfully achieving an efficient active safe driving in ITS. This paper thus proposes the Adaptive Forwarding message and Cooperative Safe driving (namely AFCS) for achieving active safe driving mechanism. AFCS avoids flooding the broadcast-type Ems, and then guarantees QoS transmissions of EMs and the real-time driving video information sharing among vehicles. Furthermore, we model an analytical model to analyze several important parameters: packet forwarding delay, packet connectivity probability, number of forwarded messages, etc. Additionally, the proposed approach is applied to cooperate with the cooperative-based ACC to reduce the butterfly effect when vehicles suddenly brake. Numerical results demonstrate that AFCS outperforms the compared approaches in transmission range, connectivity probability, total number of forwarding messages, number of hop-counts, the end-to-end delay, and the butterfly effect. The analysis result is close to the simulation result, and thus justifies the claims of the analytical model.

Clock Synchronization Over Communication Paths With Queue-Induced Delay Asymmetries

Timing protocols such as the IEEE 1588 Precision Time Protocol and the Network Time Protocol require an accurate measurement of the communication path delay between the time server (master) and the client (slave) in order to provide a precise timing synchronization. The precise time at the client's site is then estimated using an assumption that forward and backward delays due to physical propagation time through network are equal, or any difference between them is calibrated beforehand. Apart from physical link delays, a timing packet experiences queue-induced delay due to switching/routing devices on the path. This queuing delay is usually different in forward and backward directions, thus introducing the queue-induced asymmetry (QIA), which is a major contributor to the time error between master and slave clocks if physical asymmetries are calibrated. This letter proposes a new technique for QIA compensation that does not require any on-path timing support, thus is easily deployed with current network devices.

A distributed beaconless routing protocol for real-time video dissemination in multimedia VANETs

Vehicular Ad-Hoc Networks (VANETs) will play an important role in Smart Cities and will support the development of not only safety applications, but also car smart video surveillance services. Recent improvements in multimedia over VANETs allow drivers, passengers, and rescue teams to capture, share, and access on-road multimedia services. Vehicles can cooperate with each other to transmit live flows of traffic accidents or disasters and provide drivers, passengers, and rescue teams rich visual information about a monitored area. Since humans will watch the videos, their distribution must be done by considering the provided Quality of Experience (QoE) even in multi-hop, multi-path, and dynamic environments. This article introduces an application framework to handle this kind of services and a routing protocol, the DBD (Distributed Beaconless Dissemination), that enhances the dissemination of live video flows on multimedia highway VANETs. DBD uses a backbone-based approach to create and maintain persistent and high quality routes during the video delivery in opportunistic Vehicle to Vehicle (V2V) scenarios. It also improves the performance of the IEEE 802.11p MAC layer, by solving the Spurious Forwarding (SF) problem, while increasing the packet delivery ratio and reducing the forwarding delay. Performance evaluation results show the benefits of DBD compared to existing works in forwarding videos over VANETs, where main objective and subjective QoE results are measured.

Predictive Method of Networked Control of Industrial Automation Systems

A New method for real-time prediction of uncertain network transmission time delay and the closed-loop control method through the network manufacturing and industrial plant are introduced. Put forward delay prediction method is based on the multilayer perceptron neural model. To reduce the amount of the first layer of neurons network, thus reducing the computational burden a real-time implementation, a method for the determination of Markov delay sequence order. Used to predict delay and a zero order equivalent discrete time model of the plant, a kind of time-varying state feedback control algorithm is put forward a strategy to obtain real-time update. The stability of the closed-loop switch sufficient conditions is derived using the theorem of linear system. It shows that the method studies of industrial network by two cases, i.e., a DC motor driven transport roll paper and a milling machine. Simulation study describes the effectiveness of the method to control these challenging problems.

Eliminating Bottlenecks in the South African Conveyancing Environment

Customer valuations are not just about service quality but also process efficiency. As a result organisations need to continuously reassess their business processes in order to improve their operations and service delivery to their customers. Conveyancing deals with the exchange of immovable property. Although conveyancing processes are wider in context than conventional organisational-level business processes, the issues of process bottlenecks, efficiency, and effectiveness are also present. The end-to-end property process in South Africa seems to be tedious, cumbersome and very complex. This paper deals with bottlenecks that may occur at the various stages in immovable property exchange transactions. It puts forward delay reasons identified by stakeholders in the property service chain and puts together a debottlenecking framework for the end-to-end conveyancing process. DOI: 10.5901/mjss.2014.v5n14p97

QoS Aware Multipath Threshold Routing for Mobile Ad hoc Networks

Due to their dynamic topology and lack of central administration, Quality of Service (QoS) provisioning in Mobile Ad hoc Networks (MANET) is a challenging task. QoS is crucial for supporting delay sensitive real-time services in MANETs. Due to the un-predictable behaviour and topology changes of such networks, routing protocols need to quickly and accurately capture and manage the delay, congestion and load at various locations of the network. This paper presents a novel threshold based multipath routing approach for enhanced QoS in MANETs. In this approach, when the available bandwidth of a link decreases below a defined threshold or average load or the forwarding delay at a node increases beyond a defined threshold, traffic is distributed over fail-safe multiple routes to reduce the load at a congested node. Through simulation results, we show that the proposed approach achieves improved QoS in terms of end-to-end delay, packet delivery ratio, and throughput for constant bit rate (CBR) traffic when compared with Optimised Link State Routing (OLSR), a popular single path proactive protocol for MANETs.

Multiuser Detection with Delay Feedback Scheme for Asynchronous Cooperative Networks

The transmission antennas in cooperative systems are spatially distributed on multiple nodes, so the received signal can be asynchronous due to the propagation delays. In this paper, we propose a novel feedback mechanism for cooperative relay networks to improve the performance by increasing the forwarding delay. In contrast to a previous work by the authors, where the performance is poor for small delay, the proposed feedback scheme in amore attractive scenario where the destination can deal with any delay with the better performance. Simulation results illustrate the performance of the proposed scheme in comparison with forward and backward interference cancellation (FBIC) scheme without feedback. Finally, we demonstrate that the greater the delay, the more obvious advantages of the algorithm complexity than bounded delay tolerant Alamouti codes (BDT-AC).

Bilateral teleoperation of multiple agents with formation control

This paper studies the formation problem for multi-slave teleoperation system over general communication networks, where multiple mobile slave agents are coupled with a single master robot. The forward and backward network transmission time delays are assumed to be asymmetric and time-varying. Due to the quantization in the network, a dynamic quantization strategy is provided to quantize the output signals of the master robot and slave agents before transmitting. Then, a novel master-slave protocol is designed to achieve the formation task under variable time delays and quantization. Additionally, the sufficient conditions for stability are presented to show that the formation protocol can stabilize the master-slave system under variable time delays and quantization. Finally, simulation are performed to show effectiveness of the main results.

Differential energy saving algorithms in a distributed router architecture

A distributed multistage software router (MSSR) is composed by several interconnected software routers running on personal computers (PCs). The MSSR architecture overcomes scalability and performance issues of single software router by providing parallel forwarding paths. Like many networking devices, a MSSR must be sized for peak traffic load, which implies energy inefficiency at low loads. Thus, we focus on energy saving schemes to improve the router energy efficiency by dynamically adapting the MSSR architecture to the currently offered load. We first introduce an optimal energy saving algorithm defined as a mixed integer linear programming (MILP) optimization model. Then, heuristic solutions, named differential algorithms are discussed. While the optimal approach provides higher energy savings, the heuristics avoid the complete MSSR reconfiguration, thus reducing forwarding delays and minimizing service interruption. The performance evaluation shows that the proposed heuristic algorithms, that gracefully modifies the internal MSSR configuration, preserve the load proportional energy demand characteristics of the optimal algorithm, with a minimal loss of efficiency, largely compensated by algorithm simplicity.

Feedback Cancellation With Probe Shaping Compensation

Adaptive feedback cancellation methods may integrate the use of probe signals to assist with the biased optimal solution in acoustic systems working in closed-loop. However, injecting a probe noise in the loudspeaker decreases the signal quality perceived by users of assistive listening devices. To counter this, probe signals are usually shaped to provide some level of perceptual masking. In this letter we show the impact of using a shaping filter on the system behavior in terms of convergence rate and steady state error. From this study, it can be concluded that shaping the probe signal may have detrimental influence in terms of system performance. Accordingly, we propose to use the unshaped probe signal combined with an inverse filter of the shaping filter to identify the feedback channel. This restructure of the problem restores convergence rate of LMS type algorithms. Furthermore, we also show that an adequate forward path delay is required to obtain an unbiased solution and that the suggested scheme reduces this delay.

Time-Optimal Convergecast With Separated Packet Copying: Scheduling Policies and Performance

Convergecast, in which packets originating from multiple sources are reported to a single sink, is a fundamental primitive for data collection in wireless sensor networks. This paper investigates the time-optimal link-scheduling problem for time-division multiple-access (TDMA)-based convergecast, aiming to minimize the amount of time required to complete convergecast. We observe that packet copying between the microcontroller and the radio transceiver in existing sensor platforms has a big impact on the packet forwarding delay, and we propose a novel model for convergecast in which packet copying is separated from packet transmission and reception. We establish tight lower bounds on the number of time slots required for convergecast in networks with line and tree routing topologies, and we present both centralized and distributed algorithms for constructing the time-optimal convergecast schedules. We evaluate our scheme in both simulations and experiments on hardware. The results show that our scheme can achieve a system throughput (defined as the number of data bits received by the sink per second) of 202.8 kb/s, which is 86.31% of the theoretical bound. In comparison with the traditional TDMA-based convergecast schemes, our scheme can achieve up to a 86.22% improvement on system throughput.

Trajectory Optimization of Packet Ferries in Opportunistic Social-Based Machine-to-Machine Networks

Machine-to-machine (M2M) communication is an emerging paradigm to connect a large number of devices through wireless technologies. In recent application scenarios, devices are normally carried by people in social contexts. Like the behavior of people, the moving activity of devices always happens in a specific area, which corresponds to some specific communities. How to guarantee the higher packet delivery ratio while reducing forwarding delay in such M2M networks is a challenging issue and has not been well addressed yet. In this paper, we put some special mobile devices (called postmen) in the opportunistic social-based M2M networks and their main responsibility is to carry packets for normal devices which belong to specific communities. Our work focuses on the optimization of the moving trajectory by considering the minimum transmission delay. We formulate the optimal issue into semi-Markov Decision Process model. The decision process includes two parts: packets-choosing strategy and trajectory of packet-ferrying determination strategy. By maximizing the individual reward of a postman, its optimal trajectory will be found. Furthermore, the proposed solution guarantees the packet delivery ratio and delay for isolated communities. Simulation results show that the proposed packet-ferrying solution outperforms the two existing ferrying solutions in terms of packet delivery ratio.

A study of quality of service in the universal DBA algorithm using a PIC-based EPON testbed

Ethernet Passive Optical Network (EPON) has emerged as a promising technology since it offers high bandwidth at a distance that can go up to 20 km. In the upstream EPON transmission, a dynamic bandwidth allocation (DBA) algorithm is needed to avoid collisions and to efficiently allocate the bandwidth. This paper proposes an algorithm called as a Universal DBA (UDBA) algorithm that can support the priority universally in the entire EPON system. A peripheral interface controller (PIC)-based EPON testbed is used to test the algorithm within the mulipoint control protocol environment. For the performance study, we have compared the results achieved using UDBA in terms of delay, throughput, and fairness with two other DBA algorithms. UDBA shows improvements in terms of expedited forwarding, assured forwarding and best effort delay as much as 43.9, 42.6, 20 % over User-oriented Hierarchical Bandwidth Scheduling with Single Cycle (UHSA-S) and 37.5, 20.2, 25.3 % over Modified Smallest Available Report First (MSARF), respectively. Throughput is improved as high as 17.9 % over UHSA-S and 12.8 % over MSARF. In addition, the fairness index of UDBA is higher up to 14 % as compared to UHSA-S and 2.7 % as compared to MSARF.

Nonadditivity of forward and simultaneous masking

The current study measured the additional masking obtained for combinations of forward and simultaneous maskers as a function of forward masker bandwidth, signal delay, and simultaneous masker level. The effects of the two individual maskers were equated in all conditions. Additional masking increased with increasing masker level, increasing signal delay, and decreasing masker bandwidth. The portion of the simultaneous masker that made the greater contribution to additional masking was the part that overlapped with the signal, not with the forward masker. The changes in additional masking observed as a function of forward masker bandwidth and the interaction between the effects of forward and simultaneous maskers call into question the use of additional masking as a measure of basilar membrane compression and present problems for the use of simultaneous noise to simulate hearing loss.

An Extension of Proxy Mobile IPv6 for Reducing Handover Latency and Packet Loss using Transient Binding

Proxy Mobile IPv6 (PMIPv6) is a protocol for building a common and access technology independent of mobile core networks, accommodating various access technologies such as WiMAX, 3GPP, 3GPP2 and WLAN based access architectures. Transient Binding is a mechanism applicable to the mobile node's inter-MAG handover while using a single interface or different interfaces. Proxy Mobile IPv6 (or PMIPv6, or PMIP) is a network-based mobility management protocol This paper proposes an improvement of Proxy Mobile Ipv6 in the aspect of reducing packet loss and hand over latency. Proxy Mobile IPv6 also implements additional features not present in IPv4. This paper proposes an improvement in the Proxy Mobile IPv6.The extension of Proxy Mobile IPv6 with transient binding will support multihoming and optimizes the handover. Here the handover problem in multihoming is reduced by transient binding by using modified Local Mobility Anchor (m-LMA) with its updated Binding Cache Entry (u-BCE). Also this mechanism efficiently supports the uplink and downlink packets between mobile nodes, so it avoids superfluous packet forwarding delay and packet loss.

English

Mobile Multi-hop Relay (MMR) WiMAX network uses Relay stations (RSs) to extend the cell coverage, and enhances the link quality and the throughput. In MMR WiMAX networks, the number of hops between the Subscriber stations (SSs) and the Base station (BS) is allowed to be more than two hops when Non transparent RS (NT-RS) is used. However, this requires modification to the frame structure of NT-RS to reduce the delay of relaying the data packets across multiple hops. Therefore, this paper presents a new NT-RS frame structure aimed to decrease the multi-hop relaying delay in order to improve the performance of the data transmission over MMR WiMAX network. The proposed frame structure serves the sub-ordinate SSs as well as NT-RSs in the access zones, while using the relay zones to communicate with its super-ordinate stations. The performance of the proposed frame structure is tested through a simulation work. The results showed that,the forwarding delay is reduced, and hence the link layer and the Transmission control protocol (TCP) throughput are improved significantly.   Key words: IEEE 802.16j, transmission control protocol (TCP) performance, non transparent relay stations (NT-RS), frame structure.

Performance evaluation of fuzzy logic-based congestion optimisation approach for sensor networks

Congestion in WSN leads to excessive consumption of energy, which needs to be controlled to improve the system life time. Congestion estimation has always been an important issue in wireless sensor networks for efficient information processing. In the recent past some researchers have used fuzzy logic for congestion estimation and shown that fuzzy logic is a potential tool for detection and estimation of congestion in wireless sensor networks. In this work we have used four different fuzzy systems for congestion estimation and evaluated their performances. Through these four fuzzy systems we will estimate the number of dropped packets with respect to time. In addition to this we have also found the average number of packet dropped for time interval 0 to 100 seconds, with respect to number of nodes in a certain cluster. Three important parameters affecting information processing and congestion in wireless sensor networks are identified as packet forwarding ratio, delay and validity. Simulation results of these fuzzy systems show that validity and delay-based system gives best performance and minimises packet drops to a significant amount during information processing in wireless sensor networks.