Search for: spatial-correlations
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    Spatial prefetching

    , Article Advances in Computers ; 2021 ; 00652458 (ISSN) Lotfi Kamran, P ; Sarbazi Azad, H ; Sharif University of Technology
    Academic Press Inc  2021
    Many applications extensively use data objects with a regular and fixed layout, which leads to the recurrence of access patterns over memory regions. Spatial data prefetching techniques exploit this phenomenon to prefetch future memory references and hide their long latency. Spatial prefetchers are particularly of interest because they usually only need a small storage budget. In this chapter, we introduce the concept of spatial prefetching and present two instances of spatial data prefetchers, SMS and VLDP. © 2021 Elsevier Inc  

    Bingo spatial data prefetcher

    , Article 25th IEEE International Symposium on High Performance Computer Architecture, HPCA 2019, 16 February 2019 through 20 February 2019 ; 2019 , Pages 399-411 ; 9781728114446 (ISBN) Bakhshalipour, M ; Shakerinava, M ; Lotfi Kamran, P ; Sarbazi Azad, H ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2019
    Applications extensively use data objects with a regular and fixed layout, which leads to the recurrence of access patterns over memory regions. Spatial data prefetching techniques exploit this phenomenon to prefetch future memory references and hide the long latency of DRAM accesses. While state-of-the-art spatial data prefetchers are effective at reducing the number of data misses, we observe that there is still significant room for improvement. To select an access pattern for prefetching, existing spatial prefetchers associate observed access patterns to either a short event with a high probability of recurrence or a long event with a low probability of recurrence. Consequently, the... 

    Correlation between concentrations of chlorophyll-a and satellite derived climatic factors in the Persian Gulf

    , Article Marine Pollution Bulletin ; Volume 161, Part A , December , 2020 Moradi, M ; Moradi, N ; Sharif University of Technology
    Elsevier Ltd  2020
    Monthly mean satellite derived Chl-a, aerosols, wind, SST, PAR, and turbidity datasets were used to investigate the possible factors regulating phytoplankton variability in the Persian Gulf. The spatial correlation analysis revealed two distinct regions of SST and PAR, and a relatively uniform spatial correlation pattern of the other parameters. The cross correlation between aeolian dusts and Chl-a was significantly positive with 1–3 months offset. The pattern of spatial correlation between Chl-a and SST was positive in the shallow regions without time lag, and was negative with time offset of 3–5 months in deeper regions. The cross correlation between Chl-a and north-ward winds were... 

    Antenna Selection in MIMO Relaying Networks

    , M.Sc. Thesis Sharif University of Technology Tarkhan, Ali Asghar (Author) ; Farzaneh, Forouhar (Supervisor) ; Hoseini Khalaj, Babak (Supervisor)
    Multiple-input multiple-output (MIMO) systems have been considered a lot in the recent decade. Use of these systems results in higher data rate and higher reliability in communication systems. Use of intermediate nodes which are called relay in cooperative networks result in higher reliability and higher coverage range in wireless networks. Finally use of multiple antennas in cooperative networks results in higher data rate, higher reliability and higher coverage range in wireless networks. A drawback of multi-antenna systems is that more antennas require more RF chains. More RF chains result in higher computational complexity and higher hardware cost. A remedy for this drawback is the... 

    Image Recovery from Random and Block Losses

    , M.Sc. Thesis Sharif University of Technology Hosseini, Hossein (Author) ; Marvasti, Farrokh (Supervisor)
    Digital images degrade during transmittion via noisy channels. The goal of this thesis is to propose new methods for image recovery from random and block losses In the first part of the thesis, various techniques for image recovery from random losses will be reviewd and then a method will be proposed based on the correlation among image pixels in the spatial domain. The method is fast, efficient and robust against Gaussian noise. Also a technique will be developed for quality estimation in the recipient. The second part of the thesis devotes image recovery from block losses. After a brief survey for image inpainting techniques we intoduce the concept of image reconstruction using the... 

    Satellite and ground-based assessment of middle east meteorological parameters impact on dust activities in western iran

    , Article Scientia Iranica ; Volume 23, Issue 6 , 2016 , Pages 2478-2493 ; 10263098 (ISSN) Kermanshah, A ; Sotoudeheian, S ; Tajrishy, M ; Sharif University of Technology
    Sharif University of Technology  2016
    In this article, the relation between meteorological parameters and dust activities in western Iran has been studied. Satellite-based data achieved from TOMS are used to investigate the dust activities within a time period of 30 years. In the first part of this study, we examine the statistical trend of Aerosol Index (AI) and local meteorological parameters in 15 different stations. The same patterns of AI variations in all stations indicate that this region has always been subjected to dust storms which originate from similar sources in the neighboring countries that could be known as a sole dust transfer system. In the second part, we investigate the spatial correlation between the... 

    Predicting crash frequency for multi-vehicle collision types using multivariate poisson-lognormal spatial model: a comparative analysis

    , Article Accident Analysis and Prevention ; Volume 118 , 2018 , Pages 277-288 ; 00014575 (ISSN) Hosseinpour, M ; Sahebi, S ; Zamzuri, Z. H ; Shukri Yahaya, A ; Ismail, N ; Sharif University of Technology
    According to crash configuration and pre-crash conditions, traffic crashes are classified into different collision types. Based on the literature, multi-vehicle crashes, such as head-on, rear-end, and angle crashes, are more frequent than single-vehicle crashes, and most often result in serious consequences. From a methodological point of view, the majority of prior studies focused on multivehicle collisions have employed univariate count models to estimate crash counts separately by collision type. However, univariate models fail to account for correlations which may exist between different collision types. Among others, multivariate Poisson lognormal (MVPLN) model with spatial correlation... 

    Cooperative spectrum sensing by algorithmic techniques using spatial information

    , Article ; 2010 5th International ICST Conference on Communications and Networking in China, ChinaCom 2010, 25 August 2010 through 27 August 2010 , 2010 ; 9780984589333 (ISBN) Abachi, T ; Hemmatyar, M. A ; Fazli, M. A ; Izadi, M ; Sharif University of Technology
    Spectrum sensing is the basic step in cognitive radio networks. Its accuracy directly affects spectrum utilization. In this paper we propose a new method for blind cooperative spectrum sensing using spatial information. We model our sensing matrix as a graph, taking advantage of signal and spatial correlation of antennas. We prove that the general settings of the problem are hard to approximate. Taking spatial information into account, we propose a new scheme to find white space subregions. Cognitive radio users residing in the region may be able to transmit, but must keep their transmission power to the extent that no interference is caused to primary receivers out of the region  

    DACA: Data-aware clustering and aggregation in query-driven wireless sensor networks

    , Article 2012 21st International Conference on Computer Communications and Networks, ICCCN 2012 - Proceedings ; 2012 ; 9781467315449 (ISBN) Bahrami, S ; Yousefi, H ; Movaghar, A ; Sharif University of Technology
    Data aggregation is an effective technique which is introduced to conserve energy by reducing packet transmissions in wireless sensor networks (WSNs). In addition, it is possible to consume less energy by using the spatial correlation and redundancy of data in dense networks to form clusters of nodes sensing similar values and, in turn, transmit one data packet per cluster. In this paper, we propose a Data-Aware Clustering and Aggregation scheme (DACA) to manage the energy constraint in a query-driven WSN. The DACA selects cluster head nodes by forming a new factor as a function of three parameters including the residual energy, the data value, and the number of neighbors at each node.... 

    Multi-antenna assisted spectrum sensing in spatially correlated noise environments

    , Article Signal Processing ; Volume 108 , December , 2015 , Pages 69-76 ; 01651684 (ISSN) Koochakzadeh, A ; Malek Mohammadi, M ; Babaie Zadeh, M ; Skoglund, M ; Sharif University of Technology
    Elsevier  2015
    A significant challenge in spectrum sensing is to lessen the signal to noise ratio needed to detect the presence of primary users while the noise level may also be unknown. To meet this challenge, multi-antenna based techniques possess a greater efficiency compared to other algorithms. In a typical compact multi-antenna system, due to small interelement spacing, mutual coupling between thermal noises of adjacent receivers is significant. In this paper, unlike most of the spectrum sensing algorithms which assume spatially uncorrelated noise, the noises on the adjacent antennas can have arbitrary correlations. Also, in contrast to some other algorithms, no prior assumption is made on the... 

    A new approach for distributed image coding in wireless sensor networks

    , Article Proceedings - IEEE Symposium on Computers and Communications, 22 June 2010 through 25 June 2010, Riccione ; June , 2010 , Pages 563-566 ; 15301346 (ISSN) ; 9781424477555 (ISBN) Jamali, M ; Zokaei, S ; Rabiee, H. R ; Sharif University of Technology
    Power and bandwidth constraints are two major challenges in wireless sensor networks. Since a considerable amount of energy in sensor networks is consumed for data transmission, compression techniques may prolong the life of such networks. Moreover, with fewer bits to transmit, the network can cope better with the problem of inadequate bandwidth. In this paper, we consider an image sensor network and propose a paradigm based on the principles of Distributed Source Coding (DSC) for efficient compression. Our method relies on high correlation between the sensor nodes. The algorithm consists of two phases: the Training Phase and the Main Phase. In the Training Phase an aggregation node or a... 

    Improved dual frequency multiple access relay scheme for spatially correlated sources

    , Article 2008 International ITG Workshop on Smart Antennas, WSA 2008, Darmstadt, 26 February 2008 through 27 February 2008 ; 2008 , Pages 133-138 ; 9781424417575 (ISBN) Esteban, J. A ; Del Ser, J ; Crespo, P. M ; Khalaj, B. H ; Sharif University of Technology
    We consider the non-cooperative multiple access relay channel, where N users transmit their information to a common receiver with the assistance of a shared relay. For N = 2 independent sources and dual-frequency operation (i.e. two separate frequency channels are available for transmission), it has been recently shown [1, 2] that additional diversity gain can be attained by simply switching the transmit frequency bands between users at the relay site, thus reducing the scenario to a 2 × 2 MIMO channel with achievable diversity order equal to 2. In this paper we propose to extend this previous work to the case where the sources are spatially correlated. Under a Detect-and-Forward (DF) relay... 

    Accurate estimation of leakage power variability in sub-micrometer CMOS circuits

    , Article Proceedings - 15th Euromicro Conference on Digital System Design, DSD 2012 ; 2012 , Pages 18-25 ; 9780769547985 (ISBN) Assare, O ; Momtazpour, M ; Goudarzi, M ; Sharif University of Technology
    Leakage power has already become the major contributor to the total on-chip power consumption, rendering its estimation a necessary step in the IC design flow. The problem is further exacerbated with the increasing uncertainty in the manufacturing process known as process variability. We develop a method to estimate the variation of leakage power in the presence of both intra-die and inter-die process variability. Various complicating issues of leakage prediction such as spatial correlation of process parameters, the effect of different input states of gates on the leakage, and DIBL and stack effects are taken into account while we model the simultaneous variability of the two most critical...