Loading...
Search for: wireless-channel
0.006 seconds

    Hardware Implementation of ANFIS Based Equalizer

    , M.Sc. Thesis Sharif University of Technology Hakimi Toroghi, Navid (Author) ; Bagheri Shouraki, Saeed (Supervisor) ; Ghorshi, Mohammad Ali (Co-Advisor)
    Abstract
    Nowadays, prolific usage of free air as a medium for data transmission leads interests to optimize the conditions of devices which are involved in wireless communication systems. Inter-Symbol Interference (ISI) distortion is a natural characteristic of wireless channels that occurs due to propagating electromagnetic waves in different directions. Due to different paths between a transmitter and a receiver, the received signal consists of several copies of the transmitted signal with different delays. The most common way of eliminating or mitigating the effects of ISI is channel equalization. The present work leads to implementing a supervised equalization in wireless communication. The... 

    An efficient architecture for Sequential Monte Carlo receivers in wireless flat-fading channels

    , Article Journal of Signal Processing Systems ; Volume 68, Issue 3 , 2012 , Pages 303-315 ; 19398018 (ISSN) Shabany, M ; Sharif University of Technology
    Springer New York LLC  2012
    Abstract
    A pipelined architecture is developed for a Sequential Monte Carlo (SMC) receiver that performs joint channel estimation and data detection. The promising feature of the proposed SMC receiver is achieving the near-bound performance in fading channels without using any decision feedback, training or pilot symbols. The proposed architecture exploits the parallelism intrinsic to the algorithm and consists of three blocks, i.e., the SMC core, weight calculator, and resampler. Hardware efficient/parallel architectures for each functional block including the resampling block is developed. The novel feature of the proposed architecture is that makes the execution time of the resampling independent... 

    PIRS: Pseudo inversion based recovery of speech signals

    , Article ISSPIT 2007 - 2007 IEEE International Symposium on Signal Processing and Information Technology, Cairo, 15 December 2007 through 18 December 2007 ; 2007 , Pages 285-290 ; 9781424418350 (ISBN) Ajorloo, H ; Lakdashti, A ; Manzuri Shalmani, M. T ; Sharif University of Technology
    2007
    Abstract
    Communication of speech over error prone channels such as wireless channels and internet usually suffers from loss of large number of adjacent samples. In this paper, we propose to make artificial correlation between speech samples which distorts it. By choosing appropriate parameters, one can control this distortion to lie below acceptable ranges. Using this correlation, the receiver can recover lost samples up to a certain limit using our proposed algorithm. Experimental results show that our solution overcomes a previous one reported in the literature specially when the amount of lost samples are below the mentioned limit. ©2007 IEEE  

    Statistical-Empirical Modeling of Millimeter Wave Propagation (at 60 GHz) for Wireless Communications

    , M.Sc. Thesis Sharif University of Technology Eslami Rasekh, Maryam (Author) ; Farzaneh, Forouhar (Supervisor)
    Abstract
    Due to the short wavelengths in millimeter waves and the specific characteristics of wave propagation in this frequency band, the methods used for modeling channel response in lower frequency bands are not applicable without appropriate modifications. Considering the fact that many obstacles in the channel have sizes comparable to the wavelength (eg branches and tree leaves, brick spacing and roughness height of many surfaces), statistical-empirical methods can be an efficient way of modeling propagation in the presence of such components.
    Here an attempt has been made to obtain an appropriate model for the propagation channel using propagation models proposed in the literature. Surface... 

    Prioritisation of data partitioned MPEG-4 for streaming video in GPRS mobile networks

    , Article First IEEE and IFIP International Conference in Central Asia on Internet, 2005, Bishkek, 26 September 2005 through 28 September 2005 ; Volume 2005 , 2005 ; 0780391799 (ISBN); 9780780391796 (ISBN) Jafari, M ; Kasaei, S ; Sharif University of Technology
    2005
    Abstract
    With the advance of multimedia systems and wireless mobile communications, there has been a growing need to support multimedia services (such as mobile teleconferencing, mobile TV, telemedicine, and distance learning) using mobile multimedia technologies. Despite the research done in the field of mobile multimedia, delivery of real-time interactive video over noisy wireless channels is still a challenge for researchers. This paper presents a method for prioritising data partitioned MPEG-4 video in a way suitable for transmission over a mobile network. The effectiveness of the technique is demonstrated by examing its performance when the transport of the prioritized video streams can be... 

    A new hybrid model for performance evaluation of IEEE 802.11p broadcast mode in vehicular ad hoc networks: A numerical analysis

    , Article 2013 International Conference on Connected Vehicles and Expo, ICCVE 2013 - Proceedings ; 2013 , Pages 719-725 Ghahramani, S. A. A ; Hemmatyar, A. M. A ; Sharif University of Technology
    2013
    Abstract
    In this paper, we will propose a new methodology for performance modeling of IEEE 802.11p medium access control (MAC) sub-layer in broadcast mode. In most of the current works, it is assumed that the number of contending nodes is deterministic and constant. However, in vehicular ad hoc networks, we can observe a kind of uncertainty in number of contending vehicles, which try to get access to the shared wireless channel. This uncertainty can affect the performance analysis of MAC protocols in vehicular environments. In this paper, we will try to model the dynamicity of number of contending vehicles based on the distribution of vehicles' velocity. This model will be combined with the current... 

    Multi-party secret key agreement over state-dependent wireless broadcast channels

    , Article IEEE Transactions on Information Forensics and Security ; Volume PP, Issue 99 , 2016 ; 15566013 (ISSN) Jafari Siavoshani, M ; Mishra, S ; Fragouli, C ; Diggavi, S. N ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2016
    Abstract
    We consider a group of m trusted and authenticated nodes that aim to create a shared secret key K over a wireless channel in the presence of an eavesdropper Eve. We assume that there exists a state dependent wireless broadcast channel from one of the honest nodes to the rest of them including Eve. All of the trusted nodes can also discuss over a cost-free, noiseless and unlimited rate public channel which is also overheard by Eve. For this setup, we develop an information-theoretically secure secret key agreement protocol. We show the optimality of this protocol for "linear deterministic" wireless broadcast channels. This model generalizes the packet erasure model studied in literature for... 

    Wireless interfacing to cortical neural recording implants using 4-FSK modulation scheme

    , Article IEEE International Conference on Electronics, Circuits, and Systems, 6 December 2015 through 9 December 2015 ; Volume 2016 March , 2016 , Pages 221-224 ; 9781509002467 (ISBN) Eslampanah Sendi, M. S ; Judy, M ; Molaei, H ; Sodagar, A. M ; Sharifkhani, M ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc 
    Abstract
    This paper used a 4-level frequency shift keying (4-FSK) modulation scheme to enhance the density of wireless data transfer from implantable biomedical microsystems to the outside world. Modeling and simulation of the wireless channel for 4-FSK modulation in the case of a neural recording implant has been done. To realize the 4-FSK scheme, the modulator and demodulator circuits are proposed, designed and simulated in a 0.18-μm CMOS process, and in the 174-216 MHz frequency band at a data rate of 13.5 Mbps. Operated using a 1.8 V supply voltage, the modulator circuit consumes a power of 7.8 μW  

    Multi-Party secret key agreement over state-dependent wireless broadcast channels

    , Article IEEE Transactions on Information Forensics and Security ; Volume 12, Issue 2 , 2017 , Pages 323-337 ; 15566013 (ISSN) Jafari Siavoshani, M ; Mishra, S ; Fragouli, C ; Diggavi, S. N ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2017
    Abstract
    We consider a group of m trusted and authenticated nodes that aim to create a shared secret key K over a wireless channel in the presence of an eavesdropper Eve. We assume that there exists a state-dependent wireless broadcast channel from one of the honest nodes to the rest of them including Eve. All of the trusted nodes can also discuss over a cost-free, noiseless and unlimited rate public channel which is also overheard by Eve. For this setup, we develop an information-theoretically secure secret key agreement protocol. We show the optimality of this protocol for 'linear deterministic' wireless broadcast channels. This model generalizes the packet erasure model studied in the literature... 

    Spatial multiplexing gain in MIMO radars with widely separated antennas

    , Article IET Signal Processing ; Volume 12, Issue 2 , March , 2018 , Pages 207-213 ; 17519675 (ISSN) Nazari Majd, M ; Radmard, M ; Chitgarha, M. M ; Farina, A ; Bastani, M. H ; Nayebi, M. M ; Sharif University of Technology
    Institution of Engineering and Technology  2018
    Abstract
    Multiple-input multiple-output (MIMO) radars have attracted much attention for their superior ability to enhance a system's performance. In this study, the authors' goal was the study of the spatial multiplexing gain of MIMO radars with widely separated antennas (WS-MIMO), which the authors showed that is equal to the number of unambiguously detectable targets. They obtained this number from two different aspects: first, by defining the ambiguity function of a WS-MIMO radar in the case of multiple targets, suitable for such purpose; Second, by modelling the MIMO radar system with a MIMO wireless channel. They showed that a MIMO radar is indeed a MIMO wireless system communicating the... 

    Adaptive access and rate control of CSMA for energy, rate, and delay optimization

    , Article Eurasip Journal on Wireless Communications and Networking ; Volume 2012 , 2012 ; 16871472 (ISSN) Khodaian, M ; Pérez, J ; Khalaj, B. H ; Crespo, P. M ; Sharif University of Technology
    2012
    Abstract
    In this article, we present a cross-layer adaptive algorithm that dynamically maximizes the average utility function. A per stage utility function is defined for each link of a carrier sense multiple access-based wireless network as a weighted concave function of energy consumption, smoothed rate, and smoothed queue size. Hence, by selecting weights we can control the trade-off among them. Using dynamic programming, the utility function is maximized by dynamically adapting channel access, modulation, and coding according to the queue size and quality of the time-varying channel. We show that the optimal transmission policy has a threshold structure versus the channel state where the optimal... 

    A practical sparse channel estimation for current OFDM standards

    , Article 16th International Conference on Telecommunications, ICT 2009, 25 May 2009 through 27 May 2009 ; 2009 , Pages 217-222 ; 9781424429370 (ISBN) Soltanolkotabi, M ; Soltanalian, M ; Amini, A ; Marvasti, F ; Sharif University of Technology
    Abstract
    Wireless channels especially for OFDM transmissions can be precisely approximated by a time varying filter with sparse taps (in the time domain). Sparsity of the channel is a criterion which can highly improve the channel estimation task in mobile applications. In sparse signal processing, many efficient algorithms have been developed for finding the sparsest solution to linear equations (Basis Pursuit, Matching Pursuit) in the presence of noise. In current OFDM standards, a number of the ending subcarriers at both positive and negative frequencies are left unoccupied (for ease of analog filtering at the receiver) which results in an ill-conditioned frequency to time transformation matrix.... 

    An adaptive feedback bit allocation method for wireless systems with transmit diversity

    , Article 2005 1st International Conference on Computers, Communications and Signal Processing with Special Track on Biomedical Engineering, CCSP 2005, Kuala Lumpur, 14 November 2005 through 16 November 2005 ; 2005 , Pages 181-184 ; 1424400112 (ISBN); 9781424400119 (ISBN) Babadi, B ; Shariatpanahi, P ; Hossein Khalaj, B ; Sharif University of Technology
    2005
    Abstract
    Using multiple antenna transmitters and/or receivers is becoming a common method for improving spectral efficiency of wireless channels. The physical layer of the next generation of WLAN systems (802.11n) is based on a Multiple Input Multiple Output (MIMO) system which seems to be an efficient solution for defects which could occur in wireless channels. In this paper, we investigate an adaptive bit allocation method to feed the quantized channel state data back to the transmitting antennas, depending on the channel condition in a Multiple Input Single Output (MISO) scheme. We have proposed an adaptive bit allocation scheme with a significant performance improvement over the fixed bit... 

    Error control for multimedia communications in wireless sensor networks: A comparative performance analysis

    , Article Ad Hoc Networks ; Volume 10, Issue 6 , 2012 , Pages 1028-1042 ; 15708705 (ISSN) Naderi, M. Y ; Rabiee, H. R ; Khansari, M ; Salehi, M ; Sharif University of Technology
    Abstract
    The emerging multimedia applications of Wireless Sensor Network (WSNs) impose new challenges in design of algorithms and communication protocols for such networks. In the view of these challenges, error control is an important mechanism that enables us to provide robust multimedia communication and maintain Quality of Service (QoS). Despite the existence of some good research works on error control analysis in WSNs, none of them provides a thorough study of error control schemes for multimedia delivery. In this paper, a comprehensive performance evaluation of Automatic Repeat Request (ARQ), Forward Error Correction (FEC), Erasure Coding (EC), link-layer hybrid FEC/ARQ, and cross-layer hybrid... 

    A Street canyon approximation model for the 60 GHz propagation channel in an urban environment with rough surfaces

    , Article 2010 5th International Symposium on Telecommunications, IST 2010, 4 December 2010 through 6 December 2010 ; December , 2010 , Pages 132-137 ; 9781424481835 (ISBN) Eslami Rasekh, M ; Farzaneh, F ; Shishegar, A. A ; Sharif University of Technology
    2010
    Abstract
    In this paper, an effort has been made to model the 60 GHz wireless channel using a precise yet fast and simple method for short outdoor links that are a possible area for the use of 60 GHz wireless connectivity for high data rate services with dense frequency reuse. Considering the certain properties of this frequency band, it is possible to obtain a simple channel model to replace time consuming ray tracing methods with simpler models by disregarding low power multipath components. The street canyon model has been considered here as a replacement for ray tracing in an urban environment with below rooftop antennas to predict received power along streets and the results have been compared to... 

    Analytical study of binary differential impulse radio-ultra wide band over single-mode fibre systems using two receiver structures

    , Article IET Communications ; Volume 3, Issue 2 , 2009 , Pages 309-320 ; 17518628 (ISSN) Jazayerifar, M ; Salehi, J. A ; Cabon, B ; Sharif University of Technology
    2009
    Abstract
    A binary differential impulse radio-ultra wide band (IR-UWB) communication scheme over a single-mode optical fibre is examined. For a receiver structure, the conventional electrical receiver as well as an optical receiver structure, which is similar to the optical receiver used for digital, optically phase-modulated differential phase shift keying, are considered. The optical receiver can alleviate the IR-UWB receiver implementation challenges and it is studied for the first time in the context of IR-UWB. Considering various important noises, for example, phase noise, laser intensity noise, thermal noise and shot noise, analytical expressions for the error probability of the aforementioned...