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    LPRE: Lost speech packet recovery withenhancement

    , Article 2007 IEEE International Conference on Communications, ICC'07, Glasgow, Scotland, 24 June 2007 through 28 June 2007 ; August , 2007 , Pages 1778-1783 ; 05361486 (ISSN); 1424403537 (ISBN); 9781424403530 (ISBN) Ajorloo, H ; Manzuri Shalmani, M. T ; Sharif University of Technology
    In the internet telephony, loss of IP packets causes instantaneous discontinuities in the received speech. In this paper, we have focused on finding an error resilient method for this problem. Our proposed method creates artificial correlation between speech samples that pre-distorts the speech signal. The receiver uses this correlation to reconstruct the lost speech packets. An appropriate speech enhancement technique is designed for the reduction of the processing error in the recovered speech caused by the speech codecs. The SegSNR results show the superiority of our proposed speech enhancement method over a recently proposed one. © 2007 IEEE  

    Security Improvement of Key Management Protocols in Hierarchical Wireless Sensor Network

    , M.Sc. Thesis Sharif University of Technology Mokhtari Ardakani, Ehsan (Author) ; Salmasizadeh, Mahmood (Supervisor) ; Mohajeri, Javad (Supervisor)

    Wireless sensor networks (WSNs) use many tiny sensors to monitor phenomena such as temperature, humidity, brightness and traffic, and then transmit this information to a base station using wireless channels. WSNs find applications in military, ecological, urban and health related areas. Hierarchical wireless sensor networks are kind of sensor networks that use communication entities with different capabilities in terms of energy, processing power, bandwidth, communication range and etc. In this thesis, an introduction to WSNs and their applications, characteristics and designing factors is expressed. It continues on studying the infrastructures and the role of cryptography in enhancing... 

    Evaluating the Impact of Noise and QoS Parameters on Satisfaction (QoE) of VoIP Users

    , M.Sc. Thesis Sharif University of Technology Fathi, Parshang (Author) ; Jahangir, Amir Hossein (Supervisor)
    Today, users can easily access network and Internet services from anywhere, anytime, using mobile computing devices, such as laptops, tablets, smartphones, and so forth This trend has diversified users and their need for network protocol-based services, including VoIP. VoIP is an Internet protocol for voice transmission and reception, which has become one of the biggest challenges in today's world of communications and telecommunications. Analyzing and evaluating the quality of network service (QoS) in VoIP traffic is an essential part of the process of ensuring and improving the quality of multimedia networks. Therefore, monitoring and measuring "users’ satisfaction" toward voice... 

    Using Multiple-Radio for Solving Communication Problem in Internet of Things

    , M.Sc. Thesis Sharif University of Technology ZandKarimi, Nima (Author) ; Hemmatyar, Ali Mohammad Afshin (Supervisor)
    One of the main application domains of Internet of Things is the smart home. There are lots of kinds object in any home and all of them need to be connected to each other for sharing information. The central management system of smart home uses this information for controlling and organizing the home. The first condition of smart home is that the home should know every detail about itself. So the network infrastructure of home is very important and every single object in home must be connected to the central management system of home. But because of variety in objects there are so many connection ways which any object uses them for connecting to the network. So the central management system... 

    State-Space Model for Speech Enhancement in VoIP

    , M.Sc. Thesis Sharif University of Technology Rahimi, Alaa (Author) ; Ghorshi, Mohammad Ali (Supervisor)
    Speech enhancement in noisy environments improves the quality and intelligibility of speech and reduces communication fatigue. High performance speech enhancement models are based on Bayesian estimation models, requiring estimations of the parameters of the functions that describe the likelihood and the prior distributions of the signal and noise processes. Two Bayesian speech enhancement models which are used in this thesis are Bayesian-Kalman filter and Bayesian MAP estimation.In real time applications including VoIP, in addition to additive noise, packet loss or packet delays might also occur. In real time communications the receiver terminal replaces silence for the duration of lost... 

    Physical Layer Authentication in the Internet of Things based on Deep Learning

    , M.Sc. Thesis Sharif University of Technology Abdollahi, Majid (Author) ; Behroozi, Hamid (Supervisor)
    IoT security is an important step in the rapid development of its applications and ser-vices. Many security protocols have been defined to maintain security at higher communication layers, such as the transport layer and the application layer, but with the advent of quantum computers due to high-speed parallel computing, the previous methods are no longer secure and we have to establish security at lower layers such as the physical layer. The efficiency of IoT devices depends on the reliability of their message transmission. Cyber-attacks such as data injection, eavesdropping and man-in-the-middle can lead to security challenges. In this study, we propose a new deep learning based component... 

    Improving security issues in MANET AODV routing protocol

    , Article Lecture Notes of the Institute for Computer Sciences, Social-Informatics and Telecommunications Engineering, LNICST, 1 September 2015 through 2 September 2015 ; Volume 155 , November , 2015 , Pages 237-250 ; 18678211 (ISSN) ; 9783319250663 (ISBN) Gharehkoolchian, M ; Hemmatyar, A. M. A ; Izadi, M ; Sharif University of Technology
    Springer Verlag  2015
    Mobile Ad-hoc Networks (MANETs) are forming dynamically by joining or leaving the nodes into/from the network without any fix infrastructure. It is also possible that each mobile node act as a host or router. This kind of wireless network is prone to various security threats or attacks due to its unique characteristics like dynamic topology, open medium, lack of central monitoring, etc. So security is a vital scope in MANET to protect communication between mobile nodes. Ad-hoc On-demand Distance Vector (AODV) is one of the on-demand reactive routing protocols in MANET that initially was improved without considering security protection. Significant attempts have been done to secure AODV... 

    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
    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... 

    ARM-PFC an optimized AQM congestion controller in TCP/IP networks

    , Article Iranian Journal of Science and Technology, Transaction B: Engineering ; Volume 31, Issue 6 , December , 2007 , Pages 663-678 ; 10286284 (ISSN) Bigdeli, N ; Haeri, M ; Sharif University of Technology
    In this paper, a new effective and computationally reduced method for congestion control in high speed dynamic computer networks is introduced. The controller is designed using the well-known predictive functional control (PFC) scheme and an ARMarkov model representation that considers the system delay explicitly. Use of the multi-step-ahead predictive ARMarkov model structure within the PFC results in a simple algebraic control law that does not require recursive model output computation in the so-called prediction horizon performed in the other Model Predictive Controllers (MPC). This combination not only reduces the required computational load, but the accumulative error due to the model... 

    Performability estimation of network services in the presence of component failures

    , Article 2006 Int. Conf. on Telecommunications and Networking, TeNe 2006, and the 2006 Int. Conf. on Industrial Electronics, Technology and Automation, IETA 2006, Part of the CISSE 2006, 4 December 2006 through 14 December 2006 ; 2007 , Pages 323-328 ; 9781402062650 (ISBN) Bidmeshki, M. M ; Shaad Zolpirani, M ; Miremadi, S. G ; Sharif University of Technology
    Springer Science and Business Media B.V  2007
    This paper presents a performability estimation approach which measures the ability of a network to deliver its services in the presence of component failures. The measurement is based on two important network service parameters, the endto- end delay and the packet loss. To evaluate the approach, different network topologies are studied using the OPNET Modeler. The results of simulations for four random topologies and two routing protocols, the RIP and the OSPF are presented and compared. The OSPF protocol with different delay timer values is also evaluated. © 2007 Springer  

    A linear AC power flow model for unbalanced multi-phase distribution networks based on current injection equations

    , Article IEEE Transactions on Power Systems ; Volume 36, Issue 4 , 2021 , Pages 3806-3809 ; 08858950 (ISSN) Heidari-Akhijahani, A ; Safdarian, A ; Vrakopoulou, M ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2021
    A realistic and practicable modeling of unbalanced distribution networks (DNs) is the missing link in most studies undertaken in these networks, e.g., optimal power flow (OPF), energy markets, etc. To address the issue, this letter proposes an unbalanced linear three-phase four-wire power flow (PF) model based on current injection equations at nodes. Also, the ZIP representation is considered for loads. The model can be easily generalized for unbalanced three-wire networks with minor changes and assumptions. Hence, the scope of the proposed method can be extended to cover both low-voltage and medium-voltage DNs. The performance of the proposed model is verified through simulations on two... 

    Developing a Test Platform for IP Multimedia Service in Mobile Core Networks

    , M.Sc. Thesis Sharif University of Technology Hatami, Amir Mohammad (Author) ; Hossein Khalaj, Babak (Supervisor)
    The value of data transmission has surprisingly increased in the past years. Years ago, transmission of a few by telegraph systems satisfied human needs. But the amount of data transmitted increases exponentially and that is where engineers face real challenges. In the first generation of mobile networks, the voice was transmitted using Analog technology but in the second generation it switched to digital systems. In third and fourth generation systems data rate and quality of service was increased. A big change from the third to fourth generation networks was being an all IP network, meaning everything including voice and data were transmitted in packet switched networks. This creates... 

    Detecting Voice in Encrypted Traffic

    , M.Sc. Thesis Sharif University of Technology Sharafi, Mohammad Hossein (Author) ; Jalili, Rasool (Supervisor)
    Today, smartphones became a universal technology, and mobile networks speed and bandwidth have increased. Additionally, some of the messengers support voice call services that are easy to use and economical. Many of the VoIP servers provide encrypted VoIP service. On the other side, ISPs need to recognize the VoIP flows to enforce their policies. In some case, ISPs should block illegal VoIP calls or fix a specific charge for them. Also, for providing a better quality of service, it’s necessary to decrease the delay of VoIP packets. Most related works have concentrated on the methods of detecting VoIP traffic that just worked on a specific application. Some other works detect VoIP by using IP... 

    Web driven alert verification

    , Article 2014 11th International ISC Conference on Information Security and Cryptology, ISCISC 2014 ; Sep , 2014 , p. 180-185 Najafi, A ; Sepahi, A ; Jalili, R ; Sharif University of Technology
    A web attack is an attack against a web server through the HTTP Protocol. By analyzing known web attacks, we find out that each one has its own behavior. Vestiges of their behavior could be detected in non-body parts of the HTTP Protocol. Such information can be used to verify web alerts generated by Web Application Firewalls (WAFs) and Web Intrusion Detection Systems (Web IDSs). In this paper, we propose a method to verify web alerts generated by mentioned sensors. The goal of the alert verification component is to eliminate or tag alerts that do not represent successful attacks. Our approach is based on analyzing HTTP Transaction metadata, including Request method, Request Headers, Status... 

    An efficient group key management protocol using code for key calculation: CKC

    , Article Telecommunication Systems ; Volume 51, Issue 2-3 , 2012 , Pages 115-123 ; 10184864 (ISSN) Hajyvahabzadeh, M ; Eidkhani, E ; Mortazavi, S. A ; Nemaney Pour, A ; Sharif University of Technology
    This paper presents a new group key management protocol, CKC (Code for Key Calculation) for secure IP multicast. In this protocol which is based on logical key hierarchy, only the group key needs to be sent to new member at join. Then, using the group key current members and the new member calculate the necessary keys by node codes and one-way hash function. A node code is a random number assigned to each node to help users calculate necessary keys. Again, at leave server just sends the new group key to the remaining members. By this key, members calculate necessary keys using node codes and one-way hash function. The security of the keys is based on one-wayness of hash function. The results... 

    Making HeNB more secure with improved secure access protocol and analyzing it

    , Article Lecture Notes of the Institute for Computer Sciences, Social-Informatics and Telecommunications Engineering, LNICST, 16 September 2015 through 18 September 2015 ; Volume 158 , 2015 , Pages 107-120 ; 18678211 (ISSN) ; 9783319269245 (ISBN) Ghasemi Najm, F ; Payandeh, A ; Habibi, H ; Sharif University of Technology
    Springer Verlag  2015
    The 3rd Generation Partnership Project (3GPP) defined a new architecture, called Home eNode B (HeNB). HeNB is able to provide new services with higher data rate in a low cost. Security is a critical aspect of HeNB. In order to have HeNB secure access to core network, 3GPP defines an authentication protocol based on IKEv2. A number of security vulnerabilities such as HeNB masquerading have not been addressed and solved by 3GPP technical specification yet. In this paper an improved HeNB authentication protocol is introduced which does not allow an attacker to connect unauthorized network users using a mask. Finally, we evaluate our protocol performance and verify it by Automated Validation of... 

    A new group key management protocol using code for key calculation: CKC

    , Article 2010 International Conference on Information Science and Applications, ICISA 2010, 21 April 2010 through 23 April 2010 ; April , 2010 ; 9781424459438 (ISBN) Hajyvahabzadeh, M ; Eidkhani, E ; Mortazavi, S. A ; Nemaney Pour, A ; Sharif University of Technology
    This paper presents a new group key management protocol, CKC (Code for Key Calculation). This protocol is based on logical key hierarchy. When a new member joins the group, server sends only the group key for that member. Then, current members and the new member calculate the necessary keys using node codes and one-way hash function. Node code is a code which is assigned to each node of the key tree. Again at leave, server just sends the new group key to remaining members. By this key, members calculate necessary keys using node codes and one-way hash function. The security of the keys is based on one-wayness of hash function. The results show that CKC reduces computational and communication... 

    A robust and efficient SIP authentication scheme

    , Article Scientia Iranica ; Volume 17, Issue 1 D , June , 2010 , Pages 25-38 ; 10263098 (ISSN) Mohammadi Nodooshan, A ; Darmani, Y ; Jalili, R ; Nourani, M ; Sayad Haghighi, M ; Sharif University of Technology
    The Session Initiation Protocol (SIP), which is becoming the de facto standard for the next-generation VoIP networks, is currently receiving much attention in many aspects. One aspect that was not deeply addressed in the original SIP is its authentication procedure. Apart from its security, an SIP authentication procedure should be efficient. This paper proposes a robust and efficient three-party SIP authentication protocol. In this protocol, the. end users are. authenticated with the proxy server in their domain using the. registrar server. Compared to previous works, our proposed protocol is more efficient and secure. To support our protocol with a formal security proof, its model is... 

    A learning automata and clustering-based routing protocol for named data networking

    , Article Telecommunication Systems ; 2016 , Pages 1-21 ; 10184864 (ISSN) Shariat, Z ; Movaghar, A ; Hoseinzadeh, M ; Sharif University of Technology
    Springer New York LLC 
    Named Data Networking (NDN) is a new information-centric networking architecture in which data or content is identified by a unique name and saved pieces of the content are used in the cache of routers. Certainly, routing is one of the major challenges in these networks. In NDN, to achieve the required data for users, interest messages containing the names of data are sent. Because the source and destination addresses are not included in this package, routers forward them using the names that carried in packages. This forward will continue until the interest package is served. In this paper, we propose a routing algorithm for NDN. The purpose of this protocol is to choose a path with the... 

    General study of jitter mechanisms for metric-based wireless routing protocols

    , Article AEU - International Journal of Electronics and Communications ; Volume 79 , 2017 , Pages 132-140 ; 14348411 (ISSN) Rezaei, S ; Hemmatyar, A. M. A ; Sharif University of Technology
    To ameliorate high collision, a nefarious side effect of route discovery stage of reactive routing protocols in wireless networks, jitter mechanisms are proposed which enforce wireless nodes to postpone their transmission for a random amount of time so as to reduce probability of simultaneous transmission. Although it has been shown that jitter mechanisms can dramatically improve reactive routing protocols, it was not until recently that jitter mechanisms have been subjected to study. In this paper, different random distributions are proposed for jittering mechanisms and also shaping function, with the aim of which a simple routing protocol like AODV becomes sensitive to any arbitrary...