Browsing by Subject "Throughput"

Now showing 1 - 19 of 19

Open Access
Adaptive routing framework for network on chip architectures
(ACM, 2016-01) Mustafa, Naveed Ul; Öztürk, Özcan; Niar, S.
In this paper we suggest and demonstrate the idea of applying multiple routing algorithms during the execution of a real application mapped on a Network-on-Chip (NoC). Traffic pattern of a real application may change during its execution. As performance of an algorithm depends on the traffic pattern, using the same routing algorithm for the entire span of execution may be inefficient. We study the feasibility of this idea for applications such as SPARSE and MPEG-4 decoder, by applying different routing algorithms. By applying more than one routing algorithms, throughput improves up to 17.37% and 6.74% in the case of SPARSE and MPEG-4 decoder applications, respectively, as compared to the application of single routing algorithm. © 2016 ACM.
Open Access
Analyses of serial production lines and assembly systems for throughput and inyerdeparture time variability
(1998) Kök, Abdullah Gürhan
In this thesis, we study three different but closely related production system design problems. First, we investigate the effects of various design factors such as number of stations, buffer capacity, allocation of bulfers and location of a bottleneck on the interdeparture time variability of serial production lines. In the second part, we study the effects of number of component stations, processing time distributions, buffers and buffer allocation schemes on throughput and interdeparture time variability of assembly systems. As an alternative to work transfer, we introduce variability transfer and assess its effectiveness. We analyze the anomaly displayed by optimal throughput for some processing time distributions and uncover the underlying details of this behavior. In the third part, we analyze serial production lines and assembly systems under constant workload condition. In addition to investigating the problem of determining the optimal system size, we examine the effects of other design factors such as buffers and material handling time on throughput, interdeparture time variability and cost related measures. Each part reveals several important findings. We also discuss the managerial implications of these findings to present guidelines for the practitioners.
Open Access
Analysis of assembly systems for interdeparture time variability and throughput
(Taylor & Francis, 2002) Sabuncuoğlu, İ.; Erel, E.; Kok, A. G.
This paper studies the effect of the number of component stations (parallelism), work transfer, processing time distributions, buffers and buffer allocation schemes on throughput and interdeparture time variability of assembly systems, As an alternative to work transfer, variability transfer is introduced and its effectiveness is assessed. Previous research has indicated that the optimal throughput displays an anomaly at certain processing time distributions and, this phenomenon is now thoroughly analyzed and the underlying details are uncovered. This study also yields several new findings that convey important practical implications.
Open Access
Architectural requirements for energy efficient execution of graph analytics applications
(IEEE, 2015-11) Özdal, Muhammet Mustafa; Yeşil, Şerif; Kim, T.; Ayupov, A.; Burns, S.; Öztürk, Özcan
Intelligent data analysis has become more important in the last decade especially because of the significant increase in the size and availability of data. In this paper, we focus on the common execution models and characteristics of iterative graph analytics applications. We show that the features that improve work efficiency can lead to significant overheads on existing systems. We identify the opportunities for custom hardware implementation, and outline the desired architectural features for energy efficient computation of graph analytics applications. © 2015 IEEE.
Open Access
Classification of closed and open shell pistachio nuts using principal component analysis of impact acoustics
(IEEE, 2004-05) Çetin, A. Enis; Pearson, T. C.; Tewfik, A. H.
An algorithm was developed to separate pistachio nuts with closed-shells from those with open-shells. It was observed that upon impact on a steel plate, nuts with closed-shells emit different sounds than nuts with open-shells. Two feature vectors extracted from the sound signals were melcepstrum coefficients and eigenvalues obtained from the principle component analysis of the autocorrelation matrix of the signals. Classification of a sound signal was done by linearly combining feature vectors from both mel-cepstrum and PCA feature vectors. An important property of the algorithm is that it is easily trainable. During the training phase, sounds of the nuts with closed-shells and open-shells were used to obtain a representative vector of each class. The accuracy of closed-shell nuts was more than 99% on the test set.
Open Access
Dynamic congestion control in interconnected computer networks
(IEEE, 1988-10) Ulusoy, Özgür; Baray, Mehmet
The authors evaluate a window-based congestion control mechanism in an internetwork environment. They also propose and study two dynamic-window congestion-control algorithms. These algorithms provide further control to the window mechanism by adjusting the window size in accordance with the availability of the network resources at the destination. A comparison of dynamic algorithms with fixed window control is provided in terms of throughput and delay performance. It is shown that dynamic algorithms have considerable performance advantages over fixed-window control.
Open Access
Energy-harvesting irregular repetition slotted ALOHA with unit-sized battery
(IEEE, 2018-05) Demirhan, U.; Duman, Tolga M.
We propose an irregular repetition slotted ALOHA (IRSA) based uncoordinated random access scheme for energy harvesting (EH) nodes. Specifically, we consider the case in which each user has a unit- sized battery that is recharged with energy harvested from the environment in a probabilistic manner. We analyze this scheme by deriving asymptotic throughput expressions, and obtain optimized probability distributions for the number of packet replicas for each user. We demonstrate that for the case of IRSA with EH nodes, these optimized distributions perform considerably better than those of slotted ALOHA (SA), contention resolution diversity slotted ALOHA (CRDSA) and IRSA, which do not take into account the EH process, for both asymptotic and finite frame length scenarios.
Open Access
Energy-Optimum throughput and carrier sensing rate in csma-based wireless networks
(IEEE, 2014) Koseoglu, M.; Karasan, E.
We propose a model for the energy consumption of a node as a function of its throughput in a wireless CSMA network. We first model a single-hop network, and then a multi-hop network. We show that operating the CSMA network at a high throughput is energy inefficient since unsuccessful carrier sensing attempts increase the energy consumption per transmitted bit. Operating the network at a low throughput also causes energy inefficiency because of increased sleeping duration. Achieving a balance between these two opposite operating regimes, we derive the energy-optimum carrier-sensing rate and the energy-optimum throughput which maximize the number of transmitted bits for a given energy budget. For the single-hop case, we show that the energy-optimum total throughput increases as the number of nodes sharing the channel increases. For the multi-hop case, we show that energy-optimum throughput decreases as the degree of the conflict graph corresponding to the network increases. For both cases, the energy-optimum throughput reduces as the power required for carrier-sensing increases. The energy-optimum throughput is also shown to be substantially lower than the maximum throughput and the gap increases as the degree of the conflict graph increases for multi-hop networks. © 2002-2012 IEEE.
Open Access
The general behavior of pull production systems: the allocation problems
(Elsevier, 1999) Kırkavak, N.; Dinçer, C.
The design of tandem production systems has been well studied in the literature with the primary focus being on how to improve their e ciency. Considering the large costs associated, a slight improvement in e ciency can lead to very signi®cant savings over its life. Division of work and allocation of bu er capacities between workstations are two critical design problems that have attracted the attention of many researchers. In this study, ®rst an understanding into how the system works is to be provided. Except for the integration of two allocation problems, the basic model utilized here is essentially the same as the previous studies. Theoretical results that characterize the dynamics of these systems may also provide some heuristic support in the analysis of large-scale pull production systems. Ó 1999 Elsevier Science B.V. All rights reserved.
Open Access
Goodput and throughput comparison of single-hop and multi-hop routing for IEEE 802.11 DCF-based wireless networks under hidden terminal existence
(John Wiley and Sons Ltd, 2016) Aydogdu, C.; Karasan, E.
We investigate how multi-hop routing affects the goodput and throughput performances of IEEE 802.11 distributed coordination function-based wireless networks compared with direct transmission (single hopping), when medium access control dynamics such as carrier sensing, collisions, retransmissions, and exponential backoff are taken into account under hidden terminal presence. We propose a semi-Markov chain-based goodput and throughput model for IEEE 802.11-based wireless networks, which works accurately with both multi-hopping and single hopping for different network topologies and over a large range of traffic loads. Results show that, under light traffic, there is little benefit of parallel transmissions and both single-hop and multi-hop routing achieve the same end-to-end goodput. Under moderate traffic, concurrent transmissions are favorable as multi-hopping improves the goodput up to 730% with respect to single hopping for dense networks. At heavy traffic, multi-hopping becomes unstable because of increased packet collisions and network congestion, and single-hopping achieves higher network layer goodput compared with multi-hop routing. As for the link layer throughput is concerned, multi-hopping increases throughput 75 times for large networks, whereas single hopping may become advantageous for small networks. The results point out that the end-to-end goodput can be improved by adaptively switching between single hopping and multi-hopping according to the traffic load and topology. Copyright © 2015 John Wiley & Sons, Ltd.
Open Access
Inter-varietal structural variation in grapevine genomes
(Wiley-Blackwell Publishing Ltd., 2016) Cardone, M. F.; D'Addabbo, P.; Alkan C.; Bergamini, C.; Catacchio, C. R.; Anaclerio, F.; Chiatante, G.; Marra, A.; Giannuzzi, G.; Perniola, R.; Ventura M.; Antonacci, D.
Grapevine (Vitis vinifera L.) is one of the world's most important crop plants, which is of large economic value for fruit and wine production. There is much interest in identifying genomic variations and their functional effects on inter-varietal, phenotypic differences. Using an approach developed for the analysis of human and mammalian genomes, which combines high-throughput sequencing, array comparative genomic hybridization, fluorescent inï¿½situ hybridization and quantitative PCR, we created an inter-varietal atlas of structural variations and single nucleotide variants (SNVs) for the grapevine genome analyzing four economically and genetically relevant table grapevine varieties. We found 4.8 million SNVs and detected 8% of the grapevine genome to be affected by genomic variations. We identified more than 700 copy number variation (CNV) regions and more than 2000 genes subjected to CNV as potential candidates for phenotypic differences between varieties
Open Access
Modelling and optimisation of Turkish Army 5th level renovation maintenance system via simulation
(2000) Tütüncüoğlu, Reşat Ali
Logistics is the application of time and space factors to war. It is the economics of warfare, and it comprises, in the broadest sense, the three big M's of warfare; material, movement, and maintenance. This thesis employing the simulation tool as an effective vehicle for defining the path from competitive concepts to real word solutions, modelling Turkish Army's 5 Level Renovation System and bringing up ways of optimisation. Steady state performances of the renovation unit are measured. Different types of configurations are tested and their advantages and disadvantages are discussed.
Open Access
Outage capacity and throughput maximization using theoretical and learning-based approaches
(2023-07) Masrur, Saad
This thesis explores two research problems in wireless communications: the optimal channel switching and randomization problem in flat-fading Gaussian noise channels, and channel selection and switching approaches based on the upper confidence bound (UCB) bandit algorithm. In the first part of the thesis, the optimal channel switching and randomization problem is formulated and its solution is characterized for flat-fading Gaussian noise channels with the aim of outage capacity maximization under average power and outage probability constraints. For the single user scenario, it is proved that the optimal solution can always be realized by performing one of the following strategies: (1) Transmission over a single channel with no randomization. (2) Channel switching between two channels with no randomization. (3) Randomization between two parameter sets over a single channel. Hence, the solution can easily be obtained by considering only these three strategies. However, for the multiuser scenario, obtaining the optimal solution can have very high computational complexity. Therefore, an algorithm is proposed to calculate an approximately optimal channel switching and randomization solution (with adjustable approximation accuracy) based on the solution of a linearly constrained linear optimization problem. In the second part of the thesis, we consider the case of unknown channel statistics at the transmitter, and propose channel selection and channel switching approaches based on the UCB bandit algorithm for communications between a transmitter and a receiver over a block fading channel. In the absence of channel switching in a block, we propose a UCB bandit algorithm for selecting the best channel among the possible set of channels for maximizing the number of correctly received symbols per unit of time. In the presence of channel switching, we first define a set of virtual channels by considering all possible channel pairs with various power levels and timesharing factors. Then, a UCB bandit algorithm is utilized to determine the best virtual channel; hence, to find the optimal channel switching strategy. Also, a low complexity version of this algorithm is proposed for efficient convergence to the optimal solution when a high number of virtual channels exists. In addition, for comparison purposes, theoretical limits are presented when the channel statistics are available at the transmitter. Simulation results indicate that the proposed UCB bandit algorithms can achieve very close performance to theoretical limits over a sufficiently large number of blocks, and make benefits of channel switching be realized.
Open Access
Random access over wireless links: optimal rate and activity probability selection
(2017-07) Karakoç, Nurullah
Due to the rapidly increasing number of devices in wireless networks with the proliferation of applications based on new technologies such as machine to machine communications and Internet of Things, there is a growing interest in the random access schemes as they provide a simple means of channel access. To this end, various schemes have been proposed based on the ALOHA protocol to increase the e ciency of the medium access control layer over the last decade. On the other hand, physical layer aspects of random access networks have received relatively limited attention, and there is a need to consider optimal use of the underlying physical layer properties especially for transmission over wireless channels. In this thesis, we study uncoordinated random access schemes over wireless fading channels where each user independently decides whether to send a packet or not to a common receiver at any given time slot. To characterize the system throughput, i.e., the expected sum-rate, an information theoretic formulation is developed. We consider two scenarios: classical slotted ALOHA, where no multiuser detection (MUD) capability is available and slotted ALOHA with MUD. Our main contribution is that the optimal rates and the channel activity probabilities can be characterized as a function of the user distances to the receiver to maximize the system throughput in each case (more precisely, as a function of the average signal to noise ratios of the users). We use Rayleigh fading as our main channel model, however, we also study the cases where log-normal shadowing is observed along with small scale fading. Our proposed optimal rate selection schemes o er signi cant increase in expected system throughput compared to the same rate approach commonly used in the literature. In addition to the overall throughput optimization, the issue of fairness among users is also investigated and solutions which guarantee a minimum amount of individual throughput are developed. We also design systems with limited individual outage probabilities of the users for increased energy e ciency and reduced delay. All of these analytical works are supported with detailed numerical examples, and the performance of the proposed methods are evaluated.
Open Access
Random access over wireless links: optimal rate and activity probability selection
(IEEE, 2017-12) Duman, Tolga M.; Karakoç, N.
In this paper, we consider a random access scheme over wireless fading channels based on slotted ALOHA where each user independently decides whether to send a packet or not to a common receiver at any given time slot. To characterize the system throughput, i.e., the expected sum- rate, an information theoretic formulation is developed. We consider two scenarios: classical slotted ALOHA where no multi-user detection (MUD) capability is available and slotted ALOHA with MUD. Our main contribution is that the optimal rates and channel activity probabilities can be characterized as a function of the user distances to the receiver to maximize the system throughput. In addition, we address the issue of fairness among the users and provide solutions, which guarantee a minimum amount of individual throughput.
Open Access
Reducing processor-memory performance gap and improving network-on-chip throughput
(2019-02) Mustafa, Naveed U. l.
Performance of computing systems has tremendously improved over last few decades primarily due to decreasing transistor size and increasing clock rate. Billions of transistors placed on a single chip and switching at high clock rate result in overheating of the chip. The demand for performance improvement without increasing the heat dissipation lead to the inception of multi/many core design where multiple cores and/or memories communicate through a network on chip. Unfortunately, performance of memory devices has not improved at the same rate as that of processors and hence become a performance bottleneck. On the other hand, varying traffic pattern in real applications limits the network throughput delivered by a routing algorithm. In this thesis, we address the issue of reducing processor-memory performance gap in two ways: First, by integrating improved and newly developed memory technologies in memory hierarchy of a computing system. Second, by equipping the execution platform with necessary architectural features and enabling its compiler to parallelize memory access instructions. We also address issue of improving network throughput by proposing a selection scheme that switches routing algorithm of an NoC with changing traffic pattern of an application. We present integration of emerging non-volatile memory (NVM) devices in memory hierarchy of a computing system in the context of database management systems (DBMS). To this end, we propose modifications in storage engine (SE) of a DBMS aiming at fast access to data through bypassing the slow disk interfaces while maintaining all the functionalities of a robust DBMS. As a case study, we modify the SE of PostgreSQL and detail the necessary changes and challenges such modifications entail. We evaluate our proposal using a comprehensive emulation platform. Results indicate that our modified SE reduces query execution time by up to 45% and 13% when compared to disk and NVM storage, with average reductions of 19% and 4%, respectively. Detailed analysis of these results shows that our modified SE suffers from data readiness problem. To solve this, we develop a general purpose library that employs helper threads to prefetch data from NVM hardware via a simple application program interface (API). Our library further improves query execution time for our modified SE when compared to disk and NVM storage by up to 54% and 17%, with average reductions of 23% and 8%, respectively. As a second way to reduce processor-memory performance gap, we propose a compiler optimization aiming at reduction of memory bound stalls. The proposed optimization generates efficient instruction schedule through classification of memory references and consists of two steps: affinity analysis and affinity-aware instruction scheduling. We suggest two different approaches for affinity analysis, i.e., source code annotation and automated analysis. Our experimental results show that application of annotation-based approach on a memory intensive program reduces stall cycles by 67.44%, leading to 25.61% improvement in execution time. We also evaluate automated-analysis approach using eleven different image processing benchmarks. Experimental results show that automated-analysis reduces stall cycles, on average, by 69.83%. As all benchmarks are both compute and memory-intensive, we achieve improvement in execution time by up to 30%, with a modest average of 5.79%. In order to improve network throughput, we propose a selection scheme that switches routing algorithm with changing traffic pattern. We use two selection strategies: static and dynamic selection. While static selection is made off-line, dynamic approach uses run-time information on network congestion for selection of routing algorithm. Experimental results show that our proposal improves throughput for real applications up to 37.49%. They key conclusion of this thesis is that improvement in performance of a computing system needs multifaceted approach i.e., improving the performance of memory and communication subsystem at the same time. The reduction in performance gap between processors and memories requires not only integration of improved memory technologies in system but also software/compiler support. We also conclude that switching routing algorithm with changing traffic pattern of an application leads to improvement of NoC throughput.
Open Access
Robust superhydrophilic patterning of superhydrophobic ormosil surfaces for high-throughput on-chip screening applications
(Royal Society of Chemistry, 2016) Beyazkilic, P.; Tuvshindorj, U.; Yildirim, A.; Elbuken, C.; Bayındır, Mehmet
This article describes a facile method for the preparation of two-dimensionally patterned superhydrophobic hybrid coatings with controlled wettability. Superhydrophobic coatings were deposited from nanostructured organically modified silica (ormosil) colloids that were synthesized via a simple sol-gel method. On the defined areas of the superhydrophobic ormosil coatings, stable wetted micropatterns were produced using Ultraviolet/Ozone (UV/O) treatment which modifies the surface chemistry from hydrophobic to hydrophilic without changing the surface morphology. The degree of wettability can be precisely controlled depending on the UV/O exposure duration; extremely wetted spots with water contact angle (WCA) of nearly 0° can be obtained. Furthermore, we demonstrated high-throughput biomolecular adsorption and mixing using the superhydrophilic patterns. The proposed superhydrophilic-patterned nanostructured ormosil surfaces with their simple preparation, robust and controlled wettability as well as adaptability on flexible substrates, hold great potential for biomedical and chemical on-chip analysis.
Open Access
A simple and effective mechanism for stored video streaming with TCP transport and server-side adaptive frame discard
(Elsevier, 2005) Gürses, E.; Akar, G. B.; Akar, N.
Transmission control protocol (TCP) with its well-established congestion control mechanism is the prevailing transport layer protocol for non-real time data in current Internet Protocol (IP) networks. It would be desirable to transmit any type of multimedia data using TCP in order to take advantage of the extensive operational experience behind TCP in the Internet. However, some features of TCP including retransmissions and variations in throughput and delay, although not catastrophic for non-real time data, may result in inefficiencies for video streaming applications. In this paper, we propose an architecture which consists of an input buffer at the server side, coupled with the congestion control mechanism of TCP at the transport layer, for efficiently streaming stored video in the best-effort Internet. The proposed buffer management scheme selectively discards low priority frames from its head-end, which otherwise would jeopardize the successful playout of high priority frames. Moreover, the proposed discarding policy is adaptive to changes in the bandwidth available to the video stream. © 2004 Elsevier B.V. All rights reserved.
Open Access
Spatio-temporal analysis of throughput for single-hop CSMA networks
(Institute of Electrical and Electronics Engineers Inc., 2014) Koseoglu, M.; Karasan, E.
Throughput model for non-persistent CSMA networks which was proposed by Kleinrock and Tobagi has been widely used, although it provides a loose lower bound when nodes are distributed in a large area because the analysis assumes that the propagation delay between each pair of users equals to the largest propagation delay in the network. We present a throughput analysis which considers the spatial distribution of nodes. We obtain a simple throughput expression which predicts throughput with an 8% maximum error whereas the earlier model results in a 44% error when the maximum propagation delay equals to the packet transmission time. © 2014 IEEE.