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communication-channels--information-theory
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Joint multi-user interference and clipping noise cancellation in uplink MC-CDMA system
, Article AEU - International Journal of Electronics and Communications ; Volume 64, Issue 5 , 2010 , Pages 425-432 ; 14348411 (ISSN) ; Azmi, P ; Marvasti, F ; Sharif University of Technology
Abstract
In this paper, an iterative method is proposed to jointly cancel multi-user interference and clipping noise in uplink Multi-Carrier Code Division Multiple Access (MC-CDMA) systems. Clipping is the simplest method to overcome high peak-to-average power ratio of multi-carrier signals but it makes the signals distorted. Reconstruction methods use non-distorted samples to reconstruct distorted samples in the receiver but multi-user interference causes the methods do not work properly because all the received samples are distorted due to clipping and interference and so there is no undistorted samples to be used in recovering clipped samples. On the other hand, multi-user interference...
Joint distributed source and network coding for multiple wireless unicast sessions
, Article 2009 IEEE Wireless Communications and Networking Conference, WCNC 2009, Budapest, 5 April 2009 through 8 April 2009 ; 2009 ; 15253511 (ISSN); 9781424429486 (ISBN) ; Movaghar, A ; Sharif University of Technology
2009
Abstract
Few works has been focused on the problem of joint distributed data compression and network coding. In this paper we give some examples showing the advantage of broadcast nature of wireless environment as a basis for joint codes design. Also we show that joint coding is possible in the case of multiple unicasts. The idea of this paper can be exploited in an opportunistic manner. Actually, the foundation of our idea is nothing but combining opportunistic network coding (COPE) and distributed source coding using syndromes (DISCUS) for wireless applications. © 2009 IEEE
Inter-symbol-interference reduction in indoor infrared systems by effective sampling
, Article Proceedings - 2009 International Conference on Future Computer and Communication, ICFCC 2009, 3 April 2009 through 5 April 2009, Kuala Lumpar ; 2009 , Pages 42-46 ; 9780769535913 (ISBN) ; Mansouri Rad, M. M ; Sharif University of Technology
2009
Abstract
A new and simple receiver structure for reducing the multipath inter-symbole interference (ISI) effect is proposed for infrared diffuse links. In this new method, bit-error rate (BER) performance of the system will be improved significantly without any essential change in the receiver structure. In our analysis, all major noise sources such as ambient light, signal shotnoise, dark current and thermal noise of the receiver are considered. © 2009 IEEE
Internally channel-coded framed time-hopping fiber-optic CDMA communications
, Article Journal of Lightwave Technology ; Volume 23, Issue 11 , 2005 , Pages 3702-3707 ; 07338724 (ISSN) ; Nasiri Kenari, M ; Salehi, J. A ; Sharif University of Technology
2005
Abstract
Due to the low cardinality of optical orthogonal codes (OOCs) with, a correlation value of 1, the capability of an internal channel-coding scheme cannot be applied effectively for an increasing number of simultaneous users in a typical fiber-optic code division multiple-access (FO-CDMA) system. In this paper, we consider applying the internal channel-coding scheme to the framed time-hopping (FTH) FO-CDMA system. Due to the extremely high cardinality of the spreading sequence in FTH FO-CDMA, the technique highlights the ability of the internal channel-coding scheme to increase the effective number of users in an FO-CDMA system. For the FTH FO-CDMA system, we only consider a Poisson...
Interference efficiency: A new metric to analyze the performance of cognitive radio networks
, Article IEEE Transactions on Wireless Communications ; Volume 16, Issue 4 , 2017 , Pages 2123-2138 ; 15361276 (ISSN) ; Musavian, L ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2017
Abstract
In this paper, we develop and analyze a novel performance metric, called interference efficiency, which shows the number of transmitted bits per unit of interference energy imposed on the primary users (PUs) in an underlay cognitive radio network (CRN). Specifically, we develop a framework to maximize the interference efficiency of a CRN with multiple secondary users (SUs) while satisfying target constraints on the average interference power, total transmit power, and minimum ergodic rate for the SUs. In doing so, we formulate a multiobjective optimization problem (MOP) that aims to maximize ergodic sum rate of SUs and to minimize average interference power on the primary receiver. We solve...
Interference alignment for two-user two-hop interference X-channel with delayed and no CSIT
, Article International Congress on Ultra Modern Telecommunications and Control Systems and Workshops, 6 October 2014 through 8 October 2014 ; Volume 2015-January, Issue January , 2015 , Pages 473-479 ; 21570221 (ISSN) ; Mirmohseni, M ; Akhaee, M. A ; Sharif University of Technology
IEEE Computer Society
2015
Abstract
Capacity approximation of multi-hop unicast and multi-hop multicast channels is one of unsolved problems in information theory. Recently some researches investigate Degrees of Freedom (DoF) characterization and Interference Alignment schemes for these channels. However most of them assumed perfect instantaneous Channel State Information (CSI) at the relays and the transmitters. Due to practical limitations, like the delay and the rate limitation in the feedback links and the fading channels, it is difficult to provide perfect instantaneous CSI at the transmitters and even the relays. Achievable DoF by the IA schemes collapses greatly with imperfect CSI. It has been shown that the delayed CSI...
Integer forcing-and-forward transceiver design for MIMO multipair two-way relaying
, Article IEEE Transactions on Vehicular Technology ; Volume 65, Issue 11 , 2016 , Pages 8865-8877 ; 00189545 (ISSN) ; Nasiri Kenari, M ; Maham, B ; Hejazi, M ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2016
Abstract
In this paper, we propose a new transmission scheme, called integer forcing-and-forward (IFF), for communications among multipair multiple-antenna users in which each pair exchanges their messages with the help of a single multiple-antenna relay in the multiple-access and broadcast phases. The proposed scheme utilizes integer forcing linear receiver (IFLR) at the relay, which uses equations, i.e., linear integer combinations of messages, to harness intrapair interference. Accordingly, we propose the design of a mean square error (MSE)-based transceiver, including precoder and projection matrices for the relay and users, assuming that perfect channel state information (CSI) is available. In...
Improving coverage-capacity tradeoff and power consumption of TDMA-CDMA by coverage-dependent timeslot allocation
, Article 4th IEEE International Conference on Wireless and Mobile Computing, Networking and Communication, WiMob 2008, Avignon, 12 October 2008 through 14 October 2008 ; 2008 , Pages 266-271 ; 9780769533933 (ISBN) ; Ashtiani, F ; Sharif University of Technology
2008
Abstract
Cellular CDMA systems have to trade user capacity to increase cell coverage. Moreover, coverage of CDMA is uplink-limited because uplink channels are not orthogonal and transmit powers of mobile stations are limited. In this paper, we propose a coverage-dependent dynamic channel allocation (DCA) method for TDMA-CDMA. In this method, different uplink timeslots have different level of coverage-capacity tradeoff, i.e., Non-Homogeneous Coverage-Capacity Tradeoff (NHCCT). This method reduces uplink power consumption and improves coverage-capacity tradeoff, compared to Load Balancing DCA method. Finally, we verify our approach by numerical analysis and simulation. © 2008 IEEE
Imperfect and Perfect Secrecy in Compound Multiple Access Channel with Confidential Message
, Article IEEE Transactions on Information Forensics and Security ; Volume 11, Issue 6 , 2016 , Pages 1239-1251 ; 15566013 (ISSN) ; Akhbari, B ; Ahmadian Attari, M ; Aref, M. R ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
Abstract
In this paper, we study the problem of secret communication over a compound Multiple Access Channel (MAC). In this channel, we assume that one of the transmitted messages is confidential, which is only decoded by its corresponding receiver and kept secret from the other receiver. We call this proposed setting the compound MAC with a confidential message. For this model, we derive general inner and outer bounds for both imperfect and perfect secrecy conditions for the second receiver. Also, as examples, we investigate less noisy and Gaussian versions of this channel, and extend the results of the discrete memoryless version to these cases. Moreover, providing numerical examples for the...
Image restoration using gaussian mixture models with spatially constrained patch clustering
, Article IEEE Transactions on Image Processing ; Volume 24, Issue 11 , June , 2015 , Pages 3624-3636 ; 10577149 (ISSN) ; Rabbani, H ; Babaie Zadeh, M ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2015
Abstract
In this paper, we address the problem of recovering degraded images using multivariate Gaussian mixture model (GMM) as a prior. The GMM framework in our method for image restoration is based on the assumption that the accumulation of similar patches in a neighborhood are derived from a multivariate Gaussian probability distribution with a specific covariance and mean. Previous methods of image restoration with GMM have not considered spatial (geometric) distance between patches in clustering. Our conducted experiments show that in the case of constraining Gaussian estimates into a finite-sized windows, the patch clusters are more likely to be derived from the estimated multivariate Gaussian...
Human body scattering modeling and measurement for millimeter-wave and 5g bands
, Article Proceedings of the 2019 Texas Symposium on Wireless and Microwave Circuits and Systems, WMCS 2019, 28 March 2019 through 29 March 2019 ; 2019 ; 9781728118031 (ISBN) ; Alamdar, M ; Fakharzadeh, M ; et al.; eV-Technologies; Keysight Technologies; Maury Microwave; Nokia; Wireless and Microwave Circuits and Systems Lab, Baylor University ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2019
Abstract
In this paper we address the electromagnetic (EM) wave scattering from human body in millimeter-wave (MMW) band and 5G networks, where human body can be considered as an electrically large object. The complicated geometry of human body is accurately modeled using non-uniform rational B-spline (NURBS) surfaces as a thin dielectric slab with permittivity of human skin. Physical optics (PO) approximation is used to formulate the scattering problem. To solve highly oscillatory PO integrals, triangular boundary-rectangular mesh (TBRM) algorithm is exploited. This algorithm provides frequency-independent solution for PO integrals and allows frequency-independent meshing of the human body surface....
Group-covariant extreme and quasiextreme channels
, Article Physical Review Research ; Volume 4, Issue 3 , 2022 ; 26431564 (ISSN) ; Sanders, B. C ; Sharif University of Technology
American Physical Society
2022
Abstract
Constructing all extreme instances of the set of completely positive trace-preserving (CPTP) maps, i.e., quantum channels, is a challenging and valuable open problem in quantum information theory. Here we introduce a systematic approach that, despite the lack of knowledge about the full parametrization of the set of CPTP maps on arbitrary Hilbert-spaced dimension, enables us to construct exactly those extreme channels that are covariant with respect to a finite discrete group or a compact connected Lie group. Innovative labeling of quantum channels by group representations enables us to identify the subset of group-covariant channels whose elements are group-covariant generalized-extreme...
Estimation of nonlinear dynamic systems over communication channels
, Article IEEE Transactions on Automatic Control ; Volume 63, Issue 9 , 2018 , Pages 3024-3031 ; 00189286 (ISSN) ; Farhadi, A ; Motahari, A. S ; Khalaj, B. H ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2018
Abstract
Remote observation of the state trajectory of nonlinear dynamic systems over limited capacity communication channels is studied. It is shown that two extreme cases are possible: Either the system is fully observable or the error in estimation blows up. The key observation is that such behavior is determined by the relationship between the Shannon capacity and the Lyapunov exponents; the well-known characterizing parameters of a communication channel on one side, and a dynamic system from the other side. In particular, it is proved that for nonlinear systems with initial state x0, the minimum capacity of an additive white Gaussian noise channel required for full observation of the system in...
Estimation error minimization in sensor networks with mobile agents
, Article 2006 3rd IEEE Consumer Communications and Networking Conference, CCNC 2006, Las Vegas, NV, 8 January 2006 through 10 January 2006 ; Volume 2 , 2006 , Pages 964-968 ; 1424400856 (ISBN); 9781424400850 (ISBN) ; Arbab, V. R ; Pakravan, M. R ; Sharif University of Technology
2006
Abstract
In a SEnsor Network with Mobile Agents (SENMA) is an architecture proposed for large scale sensor networks. In sensor networks, a fraction of the packets generated by only part of the sensors is sufficient to provide a good estimation of all network information. SENMA uses this inherent redundancy. However, the performance of such system is limited by estimation errors and packet errors due to collision. Estimation error is a major problem in applications such as habitat monitoring in which information is a function of node position. In this paper, we first derive the equations of distortion in a general scenario and use this model to compare the estimation error for regular networks. Then...
Error resilient source coding for video communication
, Article 2007 IEEE 15th Signal Processing and Communications Applications, SIU, Eskisehir, 11 June 2007 through 13 June 2007 ; 2007 ; 1424407192 (ISBN); 9781424407194 (ISBN) ; Lakdashti, A ; Manzuri Shalmani, M. T ; Sharif University of Technology
2007
Abstract
A novel error resilient source coding method is proposed for video codecs such as H.264 standard. The main idea is to develop an error resilient part similar to the channel coders at the source coder. This enables the receiver to recover a damaged slice of a frame, inter or intra coded, up to a certain size determined by the encoder. In contrast to another previously approach presented in the literature, our algorithm has significantly less artifacts on the video frames with a considerable increase in speed
Energy efficient secure miso non-orthogonal multiple access transmission
, Article 2018 IEEE Globecom Workshops, GC Wkshps 2018, 9 December 2018 through 13 December 2018 ; 2019 ; 9781538649206 (ISBN) ; Mirmohseni, M ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2019
Abstract
In this paper, we consider a multiple-input single-output (MISO) non-orthogonal multiple access (NOMA) system in the presence of an external single-antenna eavesdropper. We study secure downlink transmission strategies. The challenge is that the multiple antenna configurations make the successive interference cancellation (SIC) condition, which is necessary for applying NOMA schemes, much complex. We formulate the transmission power minimization problem under the quality of service (QoS), SIC and secrecy constraints. In particular, the transmission power minimization problems are formulated under both perfect channel state information (CSI) and the bounded CSI error models. These problems...
Efficient secure channel coding based on quasi-cyclic low-density parity-check codes
, Article IET Communications ; Volume 3, Issue 2 , 2009 , Pages 279-292 ; 17518628 (ISSN) ; Eghlidos, T ; Aref, M. R ; Sharif University of Technology
2009
Abstract
A secure channel coding (joint encryption-channel coding) scheme provides both data security and reliability in one combined process to achieve faster processing and/or more efficient implementation. The issue of using quasi-cyclic low-density parity-check (QC-LDPC) codes in a symmetric-key secure channel coding scheme is addressed. A set of this class of LDPC codes has recently been recommended by the NASA Goddard Space Flight Center for near-earth and deep-space communications. The proposed scheme provides an efficient error performance, an acceptable level of security and a low-complexity practicable implementation. The results indicate that the proposed scheme can efficiently employ...
Diversity-multiplexing tradeoff in MIMO radars
, Article IET Radar, Sonar and Navigation ; Volume 11, Issue 4 , 2017 , Pages 691-700 ; 17518784 (ISSN) ; Radmard, M ; Chitgarha, M. M ; Farina, A ; Nayebi, M. M ; Bastani, M. H ; Sharif University of Technology
Institution of Engineering and Technology
2017
Abstract
Two gains play key roles in recently developed multiple-input-multiple-output (MIMO) wireless communication systems: 'spatial diversity' gain and 'spatial multiplexing' gain. The diversity gain (DG) refers to the capability to decrease the error rate of the MIMO channel, whereas the multiplexing gain (MG) implicitly refers to the amount of increase in the capacity of the MIMO channel. It has been shown that there is a fundamental tradeoff between these two types of gains, meaning interplay between increasing reliability (via an increase in the DG) and increasing data rate (via an increase in the MG). On the other hand, recently, MIMO radars have attracted much attention for their superior...
Differentially encoded blind multicell multiuser massive MIMO
, Article IEEE International Conference on Communication Workshop, ICCW 2015, 8 June 2015 through 12 June 2015 ; June , 2015 , Pages 1054-1059 ; 9781467363051 (ISBN) ; Khalaj, B. H ; Pesavento, M ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2015
Abstract
In this paper, we consider the uplink of the narrowband multicell multiuser massive multiple-input multiple-output (MIMO) systems. In traditional approaches, orthogonal pilots among users of all (interfering) cells are utilized to estimate their channels assumed to be constant during channel coherence time. However, in multicell scenarios, such schemes suffer from pilot contamination. In order to address this issue, based on asymptotic pairwise orthogonality of the users' channels in massive regime, blind channel estimation schemes have been proposed. On the other hand, such schemes rely on low interference or high signal to noise ratio (SNR) levels, to achieve reliable performance. Inspired...
Deterministic multiple access wiretap channel
, Article Proceedings 2010 IEEE International Conference on Information Theory and Information Security, ICITIS 2010, 17 December 2010 through 19 December 2010, Beijing ; 2010 , Pages 998-1001 ; 9781424469406 (ISBN) ; Salimi, S ; Salmasizadeh, M ; Sharif University of Technology
2010
Abstract
Two-user Multiple Access Channel with a Wire- Tapper (MAC-WT) is considered. A general outer bound for the secrecy capacity region is given. Also, we have defined the Deterministic MAC-WT, where the channel input of each user is a deterministic function of the channel output and the channel input of the other user. For this network single-letter inner and outer bounds for the secrecy capacity region are given. Furthermore, it is shown that in the Deterministic MAC-WT, if the wiretapper channel is a degraded version of the main channel, inner and outer bounds meet and the secrecy capacity region is characterized