Non-real Time Research Articles

Packet Scheduling Study For Heterogeneous Traffic In Downlink 3gpplte System

Long Term Evolution (LTE) network deploys Orthogonal Frequency Division Multiple Access (OFDMA) technology for downlink multi-carrier transmission. To meet the Quality of Service (QoS) requirements for LTE networks, packet scheduling has been employed. Packet scheduling determines when and how the user’s packets are transmitted to the receiver. Therefore effective design of packet scheduling algorithm is an important discussion. The aims of packet scheduling are maximizing system throughput, guaranteeing fairness among users, andminimizing either or both PacketLoss Ratio (PLR)and packet delay. Inthis paper, the performance of two packet scheduling algorithms namely Log Maximum-Largest Weighted Delay First (LOG-MLWDF) and Max Delay Unit (MDU), developed for OFDM(Orthogonal Frequency Division Multiplexing)networks, has been investigated in LTE downlink networks, and acomparison of those algorithmswith a well-known scheduling algorithm namely Maximum-Largest Weighted Delay First(MLWDF) has been studied.The performance evaluation was in terms of system throughput, PLR and fairness index. This study was performed forboth real time (voice and video streaming)and non-real time (best effort)perspectives. Results show that for streaming flows,LOG-MLWDF shows best PLR performance among the considered scheduling schemes, and for best effort flows, it outperforms theother two algorithms in terms of packet delay and throughput.

Analysis of a queue length aware and latency guaranteed fuzzy-based adaptive resource allocator for WiMAX networks

Escalation of multimedia devices in recent times has prompted human appetite for affluent multimedia applications. The QoS demands of these applications can only be satisfied by more and more powerful networks. WiMAX (Worldwide Interoperability for Microwave Access) networks are best suitable to serve these real-time applications; however, quantity of non-real time and best-effort traffic also cannot be neglected. Fair and efficient distribution of resources is always challenging in these networks and schedulers need to be adaptive and passable in order to guarantee appreciable performance levels. This paper introduces a quality of service mechanism based on concepts of fuzzy logic for scheduling different traffic classes in WiMAX networks. The proposed framework simplifies fair allocation of resources to real as well as non-real-time traffic classes. The scheduling ploy is developed by modifying weighted fair queuing algorithm to work adaptively by changing weights of queues serving real- and non-real-time traffic using fuzzy logic inferencing capabilities. New weights are calculated adaptively and these weights decide amount of bandwidth allocated to a particular traffic class. The proposed system works on three parameters: amount of real- and non-real-time traffic in queues, throughput requirement for non-real-time flows, and latency requirement of real-time data. Efficiency and fairness of proposed method is evaluated by performing versatile experiments and comparisons with established practices. The results obtained as implication of proposed work are quite promising.

Multi-Wavelength Based Optical Density Sensor for Autonomous Monitoring of Microalgae.

A multi-wavelength based optical density sensor unit was designed, developed, and evaluated to monitor microalgae growth in real time. The system consisted of five main components including: (1) laser diode modules as light sources; (2) photodiodes as detectors; (3) driver circuit; (4) flow cell; and (5) sensor housing temperature controller. The sensor unit was designed to be integrated into any microalgae culture system for both real time and non-real time optical density measurements and algae growth monitoring applications. It was shown that the sensor unit was capable of monitoring the dynamics and physiological changes of the microalgae culture in real-time. Algae biomass concentration was accurately estimated with optical density measurements at 650, 685 and 780 nm wavelengths used by the sensor unit. The sensor unit was able to monitor cell concentration as high as 1.05 g·L−1 (1.51 × 108 cells·mL−1) during the culture growth without any sample preparation for the measurements. Since high cell concentrations do not need to be diluted using the sensor unit, the system has the potential to be used in industrial microalgae cultivation systems for real time monitoring and control applications that can lead to improved resource use efficiency.

Genetic Algorithm based Resource Management for Cognitive Mesh Networks with Real-time and Non-real-time Services

Quality-of-service (QoS) provisioning for a cognitive mesh network (CMN) with heterogeneous services has become a challenging area of research in recent days. Considering both real-time (RT) and non-real-time (NRT) traffic in a multihop CMN, [1] studied cross-layer resource management, including joint access control, route selection, and resource allocation. Due to the complexity of the formulated resource allocation problems, which are mixed-integer non-linear programming, a low-complexity yet efficient algorithm was proposed there to approximately solve the formulated optimization problems. In contrast, in this work, we present an application of genetic algorithm (GA) to re-address the hard resource allocation problems studied in [1]. Novel initialization, selection, crossover, and mutation operations are designed such that solutions with enough randomness can be generated and converge with as less number of attempts as possible, thus improving the efficiency of the algorithm effectively. Simulation results show the effectiveness of the newly proposed GA-based algorithm. Furthermore, by comparing the performance of the newly proposed algorithm with the one proposed in [1], more insights have been obtained in terms of the tradeoff among QoS provisioning for RT traffic, throughput maximization for NRT traffic, and time complexity of an algorithm for resource allocation in a multihop network such as CMN.

Architecture and analysis of a dynamically-scheduled real-time memory controller

Memory controller design is challenging as mixed time-criticality embedded systems feature an increasing diversity of real-time (RT) and non-real-time (NRT) applications with variable transaction sizes. To satisfy the requirements of the applications, tight bounds on the worst-case response time (WCRT) of memory transactions must be provided to RT applications, while the lowest possible average response time must be given to the remaining applications. Existing real-time memory controllers cannot efficiently achieve this goal as they either bound the WCRT by sacrificing the average response time, or cannot efficiently support variable transaction sizes. In this article, we propose to use dynamic command scheduling, which is capable of efficiently dealing with transactions with variable sizes. The three main contributions of this article are: (1) a memory controller architecture consisting of a front-end and a back-end, where the former uses a TDM arbiter with a new work-conserving policy and the latter has a dynamic command scheduling algorithm that is independent of the front-end, (2) a formalization of the timings of the memory transactions for the proposed algorithm and architecture, and (3) an analysis of WCRT for transactions to capture the behavior of both the front-end and the back-end. This WCRT analysis supports variable transaction sizes and different degrees of bank parallelism. The critical part of the WCRT is the worst-case execution time (WCET) of a transaction, which is the time spent on command scheduling in the back-end. The WCET is bounded by two techniques applied to both fixed and variable transaction sizes, respectively. We experimentally evaluate the proposed memory controller and compare to an existing semi-static approach. The results demonstrate that dynamic command scheduling significantly outperforms the semi-static approach in the average case, while it performs equally well or better in the worst-case with only a few exceptions. The former reduces the average response time for NRT applications, and the latter pertains the WCRT for RT applications.

Utility-based Scheduling Frameworks to Provide Efficient Quality-of-Service Differentiation in a Mixture of Real-time and Non-real-time Traffics

This paper proposes a utility-based scheduling framework for efficient differentiation of users’ Quality-of-Service (QoS) in a broadband wireless access system involving heterogeneous mixed traffic flows. The utility-based scheduling framework, called Maximum QoS Satisfaction (MQS), is based on three novel Radio Resource Allocation (RRA) techniques; delay-based scheduling policy for Real-Time (RT), minimum-rate-based scheduling policy for Non-Real-Time (NRT) and a throughput-based scheduling policy for Best-Effort (BE) services. Simulation study shows that MQS achieves superior performances in terms of average system throughput and user satisfaction both in single and heterogeneous mixed traffic scenarios, when compared to some existing ones.

A wireless high-frequency anemometer instrumentation system for field measurements

Field measurement of wind characteristics is of great significance for the wind engineering community. High-frequency anemometers such as ultrasonic anemometers are widely used to obtain the high-frequency fluctuating wind speed time history. However, conventional instrumentation systems may suffer from low efficiency, non-real time transmission and higher maintenance cost, and thus are not very appropriate in the field measurement of strong winds in remote areas such as mountain valleys. In order to improve the field measurement performance in those remote areas, a wireless high-frequency anemometer instrumentation system for field measurement has been developed. In this paper, the architecture of the proposed instrumentation system, and measured data transmission and treatment will be presented firstly. Then a comparison among existing instrumentation systems and the proposed one is made. It shows that the newly-developed system has considerable advantages. Furthermore, the application of this system to the bridge site located in the mountain valley is discussed. Finally, typical samples of measured data from this area are presented. It can be expected that the proposed system has a great application potential in the wind field measurement for remote areas such as the mountainous or island or coastal area, and hazardous structures such as ultra-voltage transmission tower, due to its real-time transmission, low cost and no manual collection of data and convenience.

Joint optimization of link scheduling and resource allocation in cooperative vehicular networks

Vehicular networks are a cornerstone of the envisioned intelligent transportation system (ITS) by enabling vehicles to communicate with each other via vehicle-to-vehicle (V2V) communications to overcome the current and future needs for increasing traffic safety and efficiency. In this paper, we employ the knapsack problem (KP) to formulate the problem of cooperative scheduling and radio resource management in vehicular networks for non-real time services. For the sake of maximizing sum utility (MSU) of the networks, we propose two-dimensional-multi-choice knapsack problem (2D-MCKP)-based scheduling scheme to select the coordinator vehicles for the sink vehicle and allocate radio resource to V2V and vehicle-to-infrastructure (V2I) links to solve the MSU optimization problem. Simulation results indicate that the proposed scheme significantly improves the average utility and average data rates with sustainable computational complexity. Moreover, the designed cooperative communication system achieves higher spectral efficiency and better fairness.

Combined power and rate allocation in self-optimized multi-service two-tier femtocell networks

In this paper a novel utility-based game theoretic framework is proposed towards simultaneously allocating users’ uplink transmission power and rate in multi-service two-tier open-access femtocell networks. Each user is associated with an appropriately designed utility function, depending on both transmission powers and rates, while accounting for the tier each user belongs to (i.e. Macro User (MU) and Femto User (FU)), and the type of service he requests (i.e. Real Time (RT) or Non-Real Time (NRT)). Towards mitigating the intercell and cross-tier interference caused by FUs and giving higher priority to the MUs, a convex pricing mechanism with respect to FUs’ bit energy to interference density ratio is also incorporated. The overall resource allocation problem is formulated as a Utility-based uplink Power and Rate Allocation game in Multi-Service two-tier Femtocell networks (UPRA-MSF), where each user aims selfishly at maximizing his utility-based performance. The existence and uniqueness of UPRA-MSF game's Nash equilibrium with respect to both uplink transmission power and rate is analytically shown. A distributed algorithm is proposed towards obtaining the corresponding equilibrium point and its convergence is proven. Finally, the operational effectiveness and superiority of the proposed framework is evaluated through modeling and comparative simulation.

Hybrid Energy Efficient Protocol with Service Differentiation for QoS Provisions in Multi-Hop WSNs

The growing demand of usage of wireless sensors networks (WSNs) in multiple types of applications such as environment monitoring or asset tracking makes the quality-of-service (QoS) a paramount topic in wireless sensors applications. In these applications, each sensor node may collect different types of data with different levels of importance involving a different treatment to meet QoS purpose. Consequently, a sensor network should be ready to spend more resources in transmitting packets that hold more important information. In this paper, the authors propose an enhanced protocol with differentiated services for WSNs called QoS-HEEP. The proposed protocol is an improvement of HEEP protocol while providing requested quality of service for high priority real time traffic, which is distinguished from the low priority and non-real time traffic. Thus, input traffic streams are served based on their priorities. Through simulations using NS Simulator; it is observed that the authors' proposal outperforms more than other protocols developed in the literature for QoS provisions in WSNs.

Energy-Efficient L2 Transmission Scheme in IEEE 802.11 WLAN

We propose an energy-efficient L2 transmission scheme using the protocol property of Non-Real-Time (NRT) traffic in IEEE 802.11 WLANs. Typically, the collision probability at the Access Point (AP) and the retransmission probability at the Mobile Terminals (MTs) may increase significantly when the number of served MTs constantly increases. As these probabilities are increasead, energy efficiency in WLANs is decreased. In order to reduce the retransmission attempts, the proposed scheme allocates the maximum backoff count to an MT which is using NRT traffic. Thus, we propose a new energy consumption metric for retransmission while comparing it to the Distributed Coordination Function (DCF) by numerical analysis in a saturated network situation.

A Dynamic Packet Scheduling Scheme with Multilevel Priority for Wireless Sensor Network

Packet scheduling is one of the critical issues in wireless sensor networks. In WSNs most existing scheduling mechanisms use FCFS, non-preemptive or preemptive priority algorithms. However, most of these algorithms incur high processing overhead and high end-to-end transmission delay due to the FCFS concept and starvation of real time and nonreal time data packets in non-preemptive and preemptive priority scheduling algorithms. Also, these packet scheduling algorithms are predetermined and hence cannot change in application requirements of WSNs. Therefore, in this paper, we propose a dynamic multilevel priority (DMP) packet scheduling algorithm to overcome the short comes like starvation of real time data, end-to-end or data transmission delay, and to make the packet scheduling dynamic. It is well known that in DMP scheduling scheme, nodes are organized in hierarchical structure and each node (except those nodes which are located at last level of hierarchical structure) has three level of priority queues in which real time data packets go to highest priority queue and non-real time data packets go to other two queues based on certain threshold levels of their estimated processing time. The DMP scheme proposed in this work was implemented with network simulator (NS2) v.2.32. The results obtained (end-to-end delay, average waiting time, network lifetime, and energy consumption) indicate the proposed DMP scheme is superior to existing first come first serve (FCFS) packet scheduling scheme. General Terms Wireless Sensor Network, FCFS.

Securing data exchange in wireless multimedia sensor networks: perspectives and challenges

The emerging use of Wireless Multimedia Sensor Networks (WMSNs) and communication facilities have increased the need for network security measures to protect different types of multimedia data either real time or non-real time during the transmission period. A lot of researchers are becoming more interested on secure WMSNs due to the broad application necessities which can be range over smart environment, security surveillance and smart health-care; so requirements on secure aggregation of multimedia data, Quality of Service (QoS) and privacy should be satisfied. Current technologies vs. proposed security techniques in WMSNs and its pros and cons from a security point of view are explored in details. In addition to promising future trends of this research area by giving more attention for new challenging problems including secure routing protocol, fault tolerant, robustness and recovery process. We believe that this paper will add significantly a valuable discussion among the researchers and promote them to fetch new research ideas to design approximately best model by combining the most important security issues in order to reach secure WMSNs.

Experimental study for FPGA PID position controller in CNC micro-machines

Real-time control systems based on Field Programmable Gate Array (FPGA) can make a huge number of computational operations in a short period of time under deterministic constrains; thus, electric drives in micro-machines could improve their performance deploying digital controllers in FPGA. On the other hand, conventional PID controllers for CNC micro machines have been implemented for controlling several industrial applications but there are not enough number of research papers that deal with electric drive efficiency in position close loop control using PID controllers. Thus, this paper presents a complete analysis when the electric drive for position close loop is working outside the operation point in a CNC micro machine. Experimental results illustrate the performance of the electric drive when the efficiency is considered and different materials are machining. In addition, a comparison is presented between non-real time PID controller which is based on LabVIEW USB card and the real time PID controller deployed in a LabVIEW c-RIO.

Efficient Scheduling of Packets in Wireless Sensor Networks Using Priority Based Scheduling Approach

The packet scheduling is essential and plays an important role to sense the element nodes with resource constraints in Wireless Networks. The packet scheduling scheme also scale the energy consumption and end-to-end information transmission delay in time period and non-real-time information packets during wireless transmission. The proposed Priority based Packet Scheduling (PPS) technique has a tendency to overcome the issues based on priority queues in a wireless network. The priority queue has three levels at each node, except those at the last virtual hierarchy level in the zone-based topology of wireless network. In the meantime packet square are measured and placed in the highest-priority queue and might pre-empt information packets in alternative queues. In the non-real-time period packet square are measured and placed into two alternative queues supported at a particular threshold of their calculable interval. The time period and non-real time information has two queues in a leaf node, since they did not receive information from alternative nodes which causes scale back end-to-end delay. The proposed PPS technique has affinity to evaluate performance through simulations for the time period and non-real-time information. Simulation results illustrate that the PPS Scheme outperforms typical schemes in terms of average information waiting time and end-to-end delay.

Performance Evaluation of Enterprise-Wide Network that Its Backbone Is Based on Leased Trunk

Asynchronous Transfer Mode (ATM) has been recommended and has been accepted by industry as the transfer mode for Broadband network. Currently, large scale effort has been undertaken both in the industry and academic environment to design and build high speed ATM networks for corporate bodies. These networks are meant to support both real-time and non-real time applications with different quality of service (QoS) requirements. The resources to support the applications QoS requirements are typically limited and therefore the need to dynamically allocate resource in a fair manner becomes inevitable. In this work, an evaluation is carried out on the performance of enterprise-wide network that its backbone is based on leased trunk. The performance of the leased trunk is evaluated when loaded with homogeneous and heterogeneous traffic. The evaluation is carried out in order to determine the exact effect of traffic overload on resources-trunk transmission capacity and buffer. The aim is to define the optimum loading level and the associated QoS parameter values. A typical network was adopted, modeled and simulated in MATLAB environment by using Simulink tool and the results obtained were analyzed by using Microsoft Excel.

Resource allocation in multi-relay multi-user OFDM systems for heterogeneous traffic

Resource allocation is an important issue that has not been well resolved in multi-relay multi-user Decode-and-Forward (DF) OFDM systems with subcarrier-pairing at relays in the presence of heterogeneous flows, i.e., simultaneous real-time (RT) and non-real-time (NRT) traffic. In this paper, we address the issue by first formulating it as a joint optimization problem of relay-user pair selection, subcarrier-pair assignment and power allocation and then solving it through dual decomposition and subgradient methods. Asymptotic optimal iterative algorithms with polynomial complexity are proposed with the objective of maximizing sum-transmission-rate of NRT traffic while providing quality-of-service (QoS) guarantee for RT traffic, in two cases: (i) with total network power constraint and (ii) with individual power constraints. Effective selections of initial dual variables and stepsize for the subgradient method are also presented. Simulation results are provided in multiple scenarios and they show that: (i) the proposed algorithms outperform the existing schemes in terms of providing QoS requirements of RT users and maximizing sum network transmission rates; (ii) algorithms designed under total power constraint exploit the power resource much better than those under individual power constraints.

Admission control and resource allocation strategies for IEEE 802.15.5

In this paper, a novel two-tier mechanism for the access control and resource allocation of a two-hop high data rate IEEE 802.15.5 network is proposed. One of the main contributions in this proposal is the use of a dynamic superframe size in the IEEE 802.15.5. Additionally, the ideas of using a superframe utilization threshold and a channel time allocation period (CTAP) utilization threshold are incorporated, with the aim of allowing more devices to access the shared superframe. Using these thresholds, two new hop-1 resource allocation algorithms are described; CTAP utilization threshold-based resource allocation algorithm (CTRA) and superframe utilization threshold-based resource allocation algorithm (STRA). These algorithms control the access of the hop-1 Mesh PicoNet Coordinators (MPNCs) and Mesh DEVices (MDEVs) to the channel time resources in the superframe. Furthermore, an algorithm for the distribution of the hop-1 MPNCs' resources among the real-time (RT) and non-real-time (NRT) MDEVs at hop-2 is introduced. In this mechanism, a new flag metric is applied to provide higher priorities to MPNCs over MDEVs in the hop-1 algorithms and to the RT MDEVs over the NRT MDEVs in the hop-2 algorithm. Simulation results show the superiority of the proposed mechanism over others by providing a higher satisfaction factor and higher fairness among the competing devices at both hop-1 and hop-2 of the IEEE 802.15.5.

Analysis of the impact of PCI planning on downlink throughput performance in LTE

The planning of Physical Cell Identities (PCI) has a strong impact on the performance of Long Term Evolution cellular networks. Although several PCI planning schemes have been proposed in the literature, no study has quantified the performance gains obtained by these schemes. In this paper, a comprehensive performance analysis is carried out to quantify the impact of PCI planning on user quality of service and network capacity in the downlink of LTE. First, an analytical model for the influence of PCI planning on reference signal collisions is developed. Based on this model, different PCI planning schemes are tested on a dynamic system-level simulator implementing a macrocellular scenario. During the analysis, both Voice-over-IP and full buffer services over time-synchronized and non-time synchronized networks are considered. Results show that call blocking and dropping for real-time services and user throughput for non-real time services can be significantly improved by a proper PCI plan.

Using qualitative data, people's perceptions, and the science of decision making to inform policy and improve hepatitis C care for people who use drugs

Using qualitative data, people's perceptions, and the science of decision making to inform policy and improve hepatitis C care for people who use drugs