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Total 105 records

    Optimal sensor placement for source localization in nlos conditions

    , Article 26th Iranian Conference on Electrical Engineering, ICEE 2018, 8 May 2018 through 10 May 2018 ; 2018 , Pages 435-439 ; 9781538649169 (ISBN) Juybari, S. M. S ; Behnia, F ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2018
    Abstract
    The problem of sensor placement for passive source localization under the non-line of sight signal propagation is considered in this paper. To this end, first we derive the Cramer-Rao lower bound for the time of arrival based source localization under non-line of sight conditions. Then, the optimal arrangement of sensors to achieve this lower bound is obtained in the two important cases with all of the receivers being non line of sight ones in the first case and a combination of line of sight and non-line of sight receivers in the 2nd case. © 2018 IEEE  

    An analytical framework for computation of throughput capacity in multi-hop mobile ad hoc networks

    , Article 18th Annual IEEE International Symposium on Personal, Indoor and Mobile Radio Communications, PIMRC'07, Athens, 3 September 2007 through 7 September 2007 ; December , 2007 ; 1424411440 (ISBN); 9781424411443 (ISBN) Ashtiani, F ; Hamdi, M ; Shafiee, K ; Sharif University of Technology
    2007
    Abstract
    In this paper, we propose an analytical framework in order to compute the throughput capacity of a multi-hop ad hoc network with a finite number of mobile wireless nodes. The proposed framework consists of two related queueing networks; a closed BCMP queueing network to represent the mobility model of the wireless nodes and an open BCMP queueing network comprising symmetric M/G/l nodes to represent the multi-hop packet routing process from sources to destinations. In this respect, we consider very simple MAC and routing schemes and then map the related parameters onto several components of the queueing network. By solving the linear traffic equations corresponding to concerned queueing... 

    Cross layering design of IPv6 fast handover in mobile WiMAX

    , Article ICT 2010: 2010 17th International Conference on Telecommunications, 4 April 2010 through 7 April 2010, Doha ; April , 2010 , Pages 304-308 ; 9781424452477 (ISBN) Farahbakhsh, R ; Sorooshi, M ; Sharif University of Technology
    2010
    Abstract
    Over the past few years, rapid advances in wireless broadband networks have been driving the evolution of communication and network technologies towards new mobile services for users. Handover management is still one of the most challenging issues to be solved for seamless mobility in wireless networks. To support mobility on terminal stations mobile WiMAX has been standardized. Moreover to provide seamless communications for such network Fast Mobile IPv6 (FMIPv6) has been proposed by IETF. But for seamless handover, collaboration of layer 2 and layer 3 is required. Thus, there is a requirement for cross-layering design to support proper behavior of the MIPv6 nodes in WiMAX networks. In this... 

    Coverage improvement in femtocell networks via efficient utility pricing

    , Article IET Communications ; Volume 10, Issue 16 , 2016 , Pages 2215-2221 ; 17518628 (ISSN) Shafiei kordshouli, M ; Zeinalpour Yazdi, Z ; Ramezanian, R ; Sharif University of Technology
    Institution of Engineering and Technology 
    Abstract
    Employing femtocell technology noticeably improves both the indoor coverage and the overall cellular network's capacity. In the downlink scenario, when macrocell users (MUs) are far from the macro base station (MBS) and close to the femto access points (FAPs), the transmitted signals of FAPs to their users cause severe interference on MUs. One solution to overcome this issue is serving MUs by neighbouring FAPs. Generally femtocells are selfish and have no desire to allocate their resources to MUs. In this study, a framework to motivate femtocells to share their free resources with MUs is proposed. In this framework, the femtocells are assumed to belong to a specific unit. The unit encourages... 

    A low-complexity fully scalable interleaver/address generator based on a novel property of QPP interleavers

    , Article Proceedings - IEEE International Symposium on Circuits and Systems, 28 May 2017 through 31 May 2017 ; 2017 ; 02714310 (ISSN) ; 9781467368520 (ISBN) Ardakani, A ; Shabany, M ; Sharif University of Technology
    Abstract
    5-th generation mobile networks aim the peak data rates in excess of few Gbs, which may appear to be challenging to achieve due to the existence of some blocks such as the turbo decoder. In fact, the interleaver is known to be a major challenging part of the turbo decoder due to its need to the parallel interleaved memory access. LTE uses Quadratic Permutation Polynomial (QPP) interleaver, which makes it suitable for the parallel decoding. In this paper, a new property of the QPP interleaver, called the correlated shifting property, is theoretically proved, leading to a fully scalable interleaver and a low-complexity address generator for an arbitrary order of parallelism. The proposed... 

    An area-scalable human-based mobility model

    , Article Computer Networks ; Volume 177 , 2020 Gharib, M ; Foroozani, A ; Rezaei, S ; Hemmatyar, A. M. A ; Movaghar, A ; Sharif University of Technology
    Elsevier B.V  2020
    Abstract
    Mobile networks have been growing rapidly, where it is of paramount importance to evaluate the performance of any protocol designed for such networks before deployment. Mobility is one of the main mobile network issues that directly affects performance metrics. Since mobile nodes are often carried by their owners, nodes movement should be modeled according to humans movement. In this paper, we extend our previously published human mobility model based on real collected data. The real human movement is traced, cleaned up and analyzed. To the best of our knowledge, our collected data set is the only one that contains the detail of both walking and driving nodes. The analysis shows several... 

    A simple method for detecting the possible changes of hidden information of watermarked image in an MMS message

    , Article IEEE- International Symposium on Biometrics and Security Technologies, ISBAST'08, Islamabad, 23 April 2008 through 24 April 2008 ; 2008 Shirali Shahreza, M ; Sharif University of Technology
    2008
    Abstract
    After expanding the use of computer and its affect on different aspect of life, the copyright issue has gained many attractions. For this purpose watermarking methods are proposed. In these methods a code is embedded into digital material that can be used to approve ownership, it can be visible or invisible to the user. On the other hand with the rapid growth of mobile phones, mobile telecommunication companies starting to add additional features to their mobile phones such as MMS (Multimedia Messaging Service) in order to attract more customers. MMS is a technology that allows mobile phones sending messages that includes multimedia objects esp. images. For copyright protection of images... 

    Non-fixed scatterers and their effects on MIMO multicarrier fading communication channels

    , Article 50th Annual IEEE Global Telecommunications Conference, GLOBECOM 2007, Washington, DC, 26 November 2007 through 30 November 2007 ; December , 2007 , Pages 3765-3769 ; 1424410436 (ISBN); 9781424410439 (ISBN) Saligheh Rad, H ; Gazor, S ; Shariatpanahi, P ; Sharif University of Technology
    2007
    Abstract
    There are two types of scatterers in a multipath propagation environment: fixed and non-fixed scatterers. Fixed scatterers like buildings, mountains and tree stems do not move, while non-fixed (moving) scatterers like cars, people and tree leaves move from their initial positions. In addition to different movements of the mobile station (MS) that cause different kinds of Doppler fading, movements of non-fixed scatterers are also anticipated to generate other kinds of fading/correlation. This fading changes depend on the type of the propagation environment and the type of movements of local surrounding scatterers. In this paper we characterize these effects in terms of temporal correlations.... 

    Improved user identity confidentiality for UMTS mobile networks

    , Article ECUMN 2007: Fourth European Conference on Universal Multiservice Networks, Toulouse, 14 February 2007 through 16 February 2007 ; 2007 , Pages 401-409 ; 076952768X (ISBN); 9780769527680 (ISBN) Sattarzadeh, B ; Asadpour, M ; Jalili, R ; Sharif University of Technology
    2007
    Abstract
    In UMTS mobile networks, there are some circumstances that the International Mobile Subscriber Identity (IMSI) of a user is conveyed in clear-text over the radio interface. Such situations violate the anonymity of users. In this paper, we introduce an Improved User Identity Confidentiality (IUIC) mechanism which attempts to avoid the drawback and makes users more anonymous. We give the role of IMSI to anonymous tickets in such a way that IMSI is never exposed on the radio interface or over any other link. Our IUIC mechanism, employs symmetric cryptography based on the existing network access security features of UMTS. Its implementation, security, and performance issues are also considered.... 

    Stealth steganography in SMS

    , Article 2006 IFIP International Conference on Wireless and Optical Communications Networks, Bangalore, 11 April 2006 through 13 April 2006 ; 2006 ; 1424403405 (ISBN); 9781424403400 (ISBN) Shahreza, M. S ; Sharif University of Technology
    IEEE Computer Society  2006
    Abstract
    The short message service, abbreviated to SMS, is one of the services used in mobile phones and has been warmly welcomed by the public throughout the world, esp. in Asia and Europe. Using this service, individuals can write and send to each other short messages and also black and white pictures. On the one hand, considering the issue of information security and esp. establishing hidden communications, many methods have been presented for hidden communications, among which steganography is a relatively new one. Combining steganography of data in picture and using pictures in SMS messages, this article proposes a method for hidden exchange of information. The main focus of this article is on... 

    Plane embeddings of planar graph metrics

    , Article 22nd Annual Symposium on Computational Geometry 2006, SCG'06, Sedona, AZ, 5 June 2006 through 7 June 2006 ; Volume 2006 , 2006 , Pages 197-206 ; 1595933409 (ISBN); 9781595933409 (ISBN) Bateni, M ; Demaine, E. D ; Hajiaghayi, M ; Moharrami, M ; ACM SIGACT; ACM SIGGRAPH ; Sharif University of Technology
    Association for Computing Machinery  2006
    Abstract
    Embedding metrics into constant-dimensional geometric spaces, such as the Euclidean plane, is relatively poorly understood. Motivated by applications in visualization, ad-hoc networks, and molecular reconstruction, we consider the natural problem of embedding shortest-path metrics of unweighted planar graphs (planar graph metrics) into the Euclidean plane. It is known that, in the special case of shortest-path metrics of trees, embedding into the plane requires Θ(√n) distortion in the worst case [19, 1], and surprisingly, this worst-case upper bound provides the best known approximation algorithm for minimizing distortion. We answer an open question posed in this work and highlighted by... 

    Performance evaluation of mobile ad hoc networks in the presence of energy-based selfishness

    , Article 2006 3rd International Conference on Broadband Communications, Networks and Systems, BROADNETS 2006, San Jose, CA, 1 October 2006 through 5 October 2006 ; 2006 ; 1424404258 (ISBN); 9781424404254 (ISBN) Ataie, E ; Movaghar, A ; Sharif University of Technology
    2006
    Abstract
    Cooperation of nodes for routing and packet forwarding is inevitable in a mobile ad hoc network. Selfishness in such networks is a significant challenge and can cause network performance to noticeably degrade. In this paper, we propose some new selfishness models elicited from psychological behavior of human beings. We also evaluate performance of MANET in the presence of different percentages of selfish nodes that act based on our selfishness models. Results show that energy-based selfishness is a serious problem that could affect performance depends on mobility of nodes, density of network, and time of simulation. This kind of selfishness needs a comprehensive mechanism to cope with and we... 

    Emergency SMS

    , Article 2006 SICE-ICASE International Joint Conference, Busan, 18 October 2006 through 21 October 2006 ; 2006 , Pages 1139-1142 ; 8995003855 (ISBN); 9788995003855 (ISBN) Shirali Shahreza, M ; Sharif University of Technology
    2006
    Abstract
    Delivering first aid before transferring patients to hospital is among keys to survival. Moreover, calling the emergency center as soon as possible and providing brief information about the patient are helpful for the emergency center to dispatch specialized medical team and equipments proportionate to the conditions of the patient. Mobile phone is a device which many people use and always carry with them. One more thing is that SMS (Short Message Service) stands as a favorite service in mobile network, used to exchange short messages and featuring low cost, non-stop lines of dispatch, possibilities for offline work and so forth. This paper puts forward procedures of calling an emergency... 

    Energy conserving movement-assisted deployment of Ad hoc sensor networks

    , Article IEEE Communications Letters ; Volume 10, Issue 4 , 2006 , Pages 269-271 ; 10897798 (ISSN) Mousavi, H ; Nayyeri, A ; Yazdani, N ; Lucas, C ; Sharif University of Technology
    2006
    Abstract
    Sensor network deployment is very challenging due to hostile and unpredictable nature of usage environments. In this letter, we propose two methods for the self-deployment of mobile sensors. The first one is a randomized solution that provides both simplicity and applicability to different environments. Inspired by simulated annealing, it improves both speed and energy conservation of the deployment process. The other method is suggested for environments where sensors form a connected graph, initially. At the cost of this extra limitation, we gain considerable improvements. © 2006 IEEE  

    Distributed user association and femtocell allocation in heterogeneous wireless networks

    , Article IEEE Transactions on Communications ; Vol. 62, issue. 8 , 2014 , p. 3027-3043 Bayat, S ; Louie, R. H. Y ; Han, Z ; Vucetic, B ; Li, Y ; Sharif University of Technology
    Abstract
    Deployment of low-power low-cost small access points such as femtocell access points (FAPs) constitute an attractive solution for improving the existing macrocell access points' (MAPs) capacity, reliability, and coverage. However, FAP deployment faces challenging problems such as interference management and the lack of flexible frameworks for deploying the FAPs by the service providers (SPs). In this paper, we propose a novel solution that jointly associates the user equipment (UE) to the APs, and allocates the FAPs to the SPs such that the the total satisfaction of the UEs in an uplink OFDMA network is maximized. We model the competitive behaviors among the UEs, FAPs, and SPs as a dynamic... 

    Power allocation and performance analysis for incremental-selective decode-and-forward cooperative communications over Nakagami-m fading channels

    , Article IEICE Transactions on Communications ; Volume E96-B, Issue 6 , 2013 , Pages 1531-1539 ; 09168516 (ISSN) Aghajani, R ; Saadat, R ; Aref, M. R ; Sharif University of Technology
    2013
    Abstract
    The focus of this study is the performance of the relaying network with incremental selective decode-and-forward (ISDF) protocol in non-selective slow Nakagami-m fading channels. To enhance bandwidth efficiency, when the direct transmission is not successful the relay is used to retransmit a clean copy of the source signal. The proposed protocol achieves a significant reduction in the power consumption and an improvement in performance compared to the fixed decode-and-forward (DF). The exact symbol error rate (SER) of M-PSK modulation for the ISDF protocol over general fading channels is derived. However, as the exact SER analysis is very complicated, we provide an approximated SER... 

    A low complexity architecture for the cell search applied to the LTE systems

    , Article 2012 19th IEEE International Conference on Electronics, Circuits, and Systems, ICECS 2012, 9 December 2012 through 12 December 2012 ; Dec , 2012 , Pages 300-303 ; 9781467312615 (ISBN) Golnari, A ; Sharifan, G ; Amini, Y ; Shabany, M ; Sharif University of Technology
    2012
    Abstract
    Cell search is a crucial process in the synchronization procedure for the 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE) system. In this paper, a high-speed, low-complexity and reliable architecture is proposed for both steps of cell search: sector ID and cell ID group detection. For the sector ID detection, two novel methods, sign-bit reduction and wise resource sharing, are proposed. In addition, for the cell ID group detection, we proposed an algorithm based on the Maximum Likelihood Sequence Detection (MLSD) called 'sign-bit MLSD'. Simulations show that the proposed methods result in more than 90% reduction in area compared to the state-of-the-art. We designed and... 

    An ultra-wideband 3-dB quadrature hybrid with multisection broadside stripline tandem structure

    , Article Lecture Notes of the Institute for Computer Sciences, Social-Informatics and Telecommunications Engineering ; Volume 77 LNICST , 2012 , Pages 672-681 ; 18678211 (ISSN) ; 9783642351549 (ISBN) Javadzadeh, S. M. H ; Majedi, S. M. S ; Farzaneh, F ; Sharif University of Technology
    2012
    Abstract
    Design of an Ultra-Wideband 3-dB quadrature (90°) Hybrid using ADS and HFSS softwares plus Measurement report are presented. Simultaneous Use of these two softwares lead to fast and accurate design procedure. The coupler is realized in broadside stripline and with the connection of coupled regions in tandem structure. The measured data agrees well with the expected values from simulations, and shows a good ultra wide bandwidth response over the frequency range of 1-10 GHz. Measurements showed an amplitude unbalance of ±1.5 dB, a phase unbalance of 90°±7° , and an isolation and a return loss characteristics of more than 14 dB over the frequency of 1 to 10 GHz  

    Dynamic and secure key management model for hierarchical heterogeneous sensor networks

    , Article IET Information Security ; Volume 6, Issue 4 , 2012 , Pages 271-280 ; 17518709 (ISSN) Alagheband, M. R ; Aref, M. R ; Sharif University of Technology
    2012
    Abstract
    Many applications that utilise wireless sensor networks (WSNs) require essentially secure communication. However, WSNs suffer from some inherent weaknesses because of restricted communication and hardware capabilities. Key management is the crucial important building block for all security goals in WSNs. Most existing researches tried to assign keys assuming homogeneous network architecture. Recently, a few key management models for heterogeneous WSNs have been proposed. In this study, the authors propose a dynamic key management framework based on elliptical curve cryptography and signcryption method for heterogeneous WSNs. The proposed scheme has network scalability and sensor node (SN)... 

    Graph-based altruistic games for interference mitigation in femtocell networks

    , Article 26th IEEE Annual International Symposium on Personal, Indoor, and Mobile Radio Communications, PIMRC 2015, 30 August 2015 through 2 September 2015 ; Volume 2015-December , 2015 , Pages 1883-1888 ; 9781467367820 (ISBN) Vahabpour, A ; Khalaj, B. H ; Sharif University of Technology
    Abstract
    Femtocell networks are a common means of offloading in current mobile networks. Game theoretic and learning-based self-organization schemes are known as two viable approaches for interference control in co-existing macro/femtocell networks. Nevertheless, extensions of these schemes to concurrent multi-agent scenarios often face several challenges including high computational complexity, cyclic behaviors, and lack of convergence. This paper addresses such challenges by introducing local games based on a graph representation of the network. The goal of the games is to optimize the aggregate network capacity through power control. Fairness among femtocells and quality of service (QoS) for...