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communication-channels--information-theory
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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...
Blind interference alignment for three-user multi-hop SISO interference channel
, 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 462-467 ; 21570221 (ISSN) ; Mirmohseni, M ; Akhaee, M. A ; Sharif University of Technology
IEEE Computer Society
2015
Abstract
Interference Alignment (IA) is a rather new technique to achieve higher Degrees-of-Freedom (DoF) compared to traditional orthogonal naive methods, like, Time Division Multiple Access (TDMA). In many IA schemes, Instantaneous Channel State Information at Transmitter (CSIT) is mandatory. However, this requirement becomes an obstacle to implement those methods in practice. In some practical scenarios, it is not possible to provide instantaneous or even delayed CSIT. Recently, Blind Interference Alignment (BIA) has been introduced as a solution to align interference without CSIT. In spit of major advances in single-hop Interference Channels (ICs), few researches focused on multi-hop ICs. In this...
Comprehensive study on a 2 × 2 full-rate and linear decoding complexity space-time block code
, Article IET Communications ; Volume 9, Issue 1 , 2015 , Pages 122-132 ; 17518628 (ISSN) ; Talebi, S ; Abouei, J ; Sharif University of Technology
Institution of Engineering and Technology
2015
Abstract
This paper presents a comprehensive study on the Full-Rate and Linear-Receiver (FRLR) STBC proposed as a newly coding scheme with the low decoding complexity for a 2×2 MIMO system. It is shown that the FRLR code suffers from the lack of the non-vanishing determinant (NVD) property that is a key parameter in designing a full-rate STBC with a good performance in higher data rates, across QAM constellation. To overcome this drawback, we show that the existence of the NVD feature for the FRLR code depends on the type of the modulation. In particular, it is analytically proved that the FRLR code fulfills the NVD property across the PAM constellation but not for the QAM scheme. Simulation results...
A new approach to fast decode quasi-orthogonal space-time block codes
, Article IEEE Transactions on Wireless Communications ; Volume 14, Issue 1 , 2015 , Pages 165-176 ; 15361276 (ISSN) ; Talebi, S ; Shahabinejad, M ; Sharif University of Technology
Abstract
Motivated by the statistical correspondence between phases of the transmitted and received vectors, we present a fast decoding method for quasi-orthogonal space-time block codes (QOSTBCs) in this paper. The proposed decoder selects proper candidates from precomputed and sorted sets by focusing on the phase of a specific entry of the combined and decoupled vector. The ML metric of the most probable candidates is first evaluated, and then, the remaining candidates are assessed based on the similarity between the phases. The new algorithm can work with any type of constellation such as QAM and PSK and supports generalized block-diagonal QOSTBCs. Theoretical results backed by simulation tests...
Delay-constrained utility maximisation in multi-hop random access networks
, Article IET Communications ; Volume 4, Issue 16 , November , 2010 , Pages 1908-1918 ; 17518628 (ISSN) ; Khalaj, B. H ; Sharif University of Technology
2010
Abstract
Multi-hop random access networks have received much attention because of their distributed nature which facilitates deploying many new applications over the sensor and computer networks. Recently, utility maximisation framework is applied in order to optimise performance of such networks; however, proposed algorithms result in large transmission delays. In this study, the authors will analyse delay in random access multi-hop networks and solve the delay-constrained utility maximisation problem. We define the network utility as a combination of rate utility and energy cost functions and solve the following two problems: 'optimal medium access control with link delay constraint' and, 'optimal...
Code design for IMTSC/CEO problem using multilevel Slepian-Wolf coded quantization framework
, Article Proceedings - 2010 18th Iranian Conference on Electrical Engineering, ICEE 2010, 11 May 2010 through 13 May 2010 ; 2010 , Pages 282-287 ; 9781424467600 (ISBN) ; Aghagolzadeh, A ; Rabiee, H. R ; Sharif University of Technology
Abstract
The aim of this paper is introducing coding scheme that can potentially achieve the sum rate-distortion bound of Gaussian IMTSC/CEO problem with arbitrary number of encoders. No previous work has been reported on code design for the IMTSC/CEO problem with the number of encoders greater than two. In this paper the framework of Slepian-Wolf coded quantization is extended to the case with the number of encoders greater than two. On the other hand, we apply the approach to the case of unequal levels of the observation noise at the encoders. Encoding process consists of trellis coded quantization (TCQ) and LDPC codes. The proposed framework can be easily used for any number of active encoders...
Outage analysis of relay-assisted free-space optical communications
, Article IET Communications ; Volume 4, Issue 12 , 2010 , Pages 1423-1432 ; 17518628 (ISSN) ; Nasiri Kenari, M ; Sharif University of Technology
Abstract
Despite their attractive features, free-space optical (FSO) communications suffer from several challenges in practical deployment; the major of them is fading or scintillation. To overcome such limitations, multiple input multiple output (MIMO) and cooperative techniques have been proposed. Although the promising effects of cooperative transmissions in radio frequency (RF) communications have greatly been investigated, there have not been remarkable researches on cooperative transmissions in FSO communications. In this study, the authors consider a relay-assisted FSO communication and investigate the outage performance of two well-known cooperative protocols, namely amplify-and-forward (AF)...
Transmission-line model to design matching stage for light coupling into two-dimensional photonic crystals
, Article Optics Letters ; Volume 35, Issue 2 , 2010 , Pages 115-117 ; 01469592 (ISSN) ; Khavasi, A ; Mehrany, K ; Rashidian, B ; Sharif University of Technology
Abstract
The transmission-line analogy of the planar electromagnetic reflection problem is exploited to obtain a transmission-line model that can be used to design effective, robust, and wideband interference-based matching stages. The proposed model based on a new definition for a scalar impedance is obtained by using the reflection coefficient of the zeroth-order diffracted plane wave outside the photonic crystal. It is shown to be accurate for in-band applications, where the normalized frequency is low enough to ensure that the zeroth-order diffracted plane wave is the most important factor in determining the overall reflection. The frequency limitation of employing the proposed approach is...
Performability/energy tradeoff in error-control schemes for on-chip networks
, Article IEEE Transactions on Very Large Scale Integration (VLSI) Systems ; Volume 18, Issue 1 , 2010 , Pages 1-14 ; 10638210 (ISSN) ; Al Hashimi, B. M ; Rosinger, P ; Miremadi, S. G ; Benini, L ; Sharif University of Technology
Abstract
High reliability against noise, high performance, and low energy consumption are key objectives in the design of on-chip networks. Recently some researchers have considered the impact of various error-control schemes on these objectives and on the tradeoff between them. In all these works performance and reliability are measured separately. However, we will argue in this paper that the use of error-control schemes in on-chip networks results in degradable systems, hence, performance and reliability must be measured jointly using a unified measure, i.e., performability. Based on the traditional concept of performability, we provide a definition for the "Interconnect Performability"....
Optimal wavelength allocation in hybrid quantum-classical networks
, Article European Signal Processing Conference, 28 August 2016 through 2 September 2016 ; Volume 2016-November , 2016 , Pages 483-487 ; 22195491 (ISSN) ; 9780992862657 (ISBN) ; Razavi, M ; Salehi, J. A ; Sharif University of Technology
European Signal Processing Conference, EUSIPCO
2016
Abstract
An efficient method for optimal allocation of wavelengths in a hybrid dense-wavelength-division-multiplexing system, carrying both quantum and classical data, is proposed. The transmission of quantum bits alongside intense classical signals on the same fiber faces major challenges arising from the background noise generated by classical channels. Raman scattering, in particular, is shown to have detrimental effects on the performance of quantum key distribution systems. Here, by using a nearly optimal wavelength allocation technique, we minimize the Raman induced background noise on quantum channels, hence maximize the achievable secret key generation rate for quantum channels. It turns out...
ACM: Accurate crosstalk modeling to predict channel delay in Network-on-Chips
, Article 2016 IEEE 22nd International Symposium on On-Line Testing and Robust System Design, IOLTS 2016, 4 July 2016 through 6 July 2016 ; 2016 , Pages 7-8 ; 9781509015061 (ISBN) ; Shirmohammadi, Z ; Miremadi, S. G ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2016
Abstract
The severity of timing delay in the communication channels of Network on Chip (NoC) depends on the transition patterns appearing on the wires. An analytical model can estimate the timing delay in NoC channels in the presence of crosstalk faults. However, recently proposed analytical model does not have enough accuracy and is based on 3-wire delay model. In this paper, an Accurate Crosstalk Model (ACM) based on 5-wire delay model is proposed to estimate the delay of communication channels in the presence of crosstalk faults. ACM is more accurate due to considering more wires in the delay model and also considering the overlaps between locations of transition patterns
Throughput modeling of distributed reservation protocol
, Article IEEE Transactions on Mobile Computing ; Volume 15, Issue 2 , 2016 , Pages 503-515 ; 15361233 (ISSN) ; Manzuri Shalmani, M. T ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
Abstract
To evaluate the performance of distributed mediumaccess control (MAC) layer of emerging ultra wideband (UWB) and 60-GHz millimeter wave (mmWave) wireless personal area networks (WPANs) based on distributed reservation protocol (DRP) of ECMA-368 and ECMA-387 standards, we provide an analytical model for the probability distribution of steady state throughput as a function of the network dimensions size, number of devices, antenna beamwidth, transmission range, bit error rate (BER), antenna disturbance rate (ADR), aggregation length, payload size, and incoming frame rate. Using this model, the optimal payload size is computed as an example of optimization problem.We also propose a formula for...
Cross-layer QSI-Aware radio resource management for HetNets with flexible backhaul
, Article 2016 IEEE Wireless Communications and Networking Conference, 3 April 2016 through 7 April 2016 ; Volume 2016-September , 2016 ; 15253511 (ISSN) ; 9781467398145 (ISBN) ; Zhang, F ; Liu, A ; Lau, V ; Tsang, D ; Pakravan, M. R ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
Abstract
In this paper, we consider the problem of cross-layer radio resource management in heterogeneous networks (HetNets) with flexible backhaul, which aims at minimizing the total transmit power of base stations (BSs) while guaranteeing the average end-To-end data rate requirement of each data flow. We formulate the problem as a two-Timescale stochastic optimisation, where the long-Timescale control variables are flow control, routing control and interference coordination, while the short-Timescale control variable is instantaneous beamforming within each cell. Using a stochastic cutting plane (SCP) method, we propose a cross-layer queue-state information (QSI) aware radio resource management...
On the capacity region of asymmetric gaussian two-way line channel
, Article IEEE Transactions on Communications ; Volume 64, Issue 9 , 2016 , Pages 3669-3682 ; 00906778 (ISSN) ; Karimi Bidhendi, S ; Behroozi, H ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2016
Abstract
Lattice codes are known to outperform random codes for certain networks, especially in the Gaussian two-way relay channels (GTWRCs) where lattice codes are able to exploit their linearity. As an extension of the GTWRC, in this paper, we consider the asymmetric Gaussian two-way line network where two nodes exchange their messages through multiple relays. We first investigate the capacity region of the full-duplex two-way two-relay line network. The results can be extended to an arbitrary number of relays and to half-duplex scenarios. This channel consists of four nodes: 1 ↔ 2 ↔ 3 ↔ 4, where nodes 1 and 4 with the help of two full-duplex relays, i.e., nodes 2 and 3, exchange their messages...
BER derivation for UWB communication with a relay node in the presence of inter-channel interference
, Article 2009 IEEE 3rd International Symposium on Advanced Networks and Telecommunication Systems, ANTS 2009, 14 December 2009 through 16 December 2009, New Delhi ; 2009 ; 9781424459896 (ISBN) ; Nasiri Kenari, M ; Aazhang, B ; Sharif University of Technology
Abstract
In this paper, we present the average bit error probability (BEP) of a decode-and-forward relay network employing UWB links, developed by IEEE 802.15.4a standards, between its nodes. Our methodology is based on computing the Characteristic Function (CF) of the decision variable at the destination terminal. Numerical results show that significant improvement in the BEP of impulse radio UWB system is obtained by adding a relay node. The analytical expressions are also validated by computer simulations which confirm the accuracy of the approximations used in obtaining the BEP
A new nonlinear controller for active power filters
, Article 2009 International Conference on Electric Power and Energy Conversion Systems, EPECS 2009, 10 November 2009 through 12 November 2009 ; 2009 ; 9789948427155 (ISBN) ; Mokhtari, H ; Sharif University of Technology
Abstract
Linear controllers have been widely used for controlling Active Power Filters (APFs). However, due to their limitations, a tradeoff between the bandwidth of the current control loop (CCL) and the voltage control loop (VCL) need to be made to remain stable in all conditions. This tradeoff leads to imperfect usage of the APF's capacity. Nonlinear controllers can eliminate such limitations and simultaneously remain stable in all conditions. In this paper, a new nonlinear controller for controlling the output current and the DC voltage (Vdc) of an APF is proposed. Feedback linearization method is applied on the CCL and the VCL is controlled via indirect method. In this method, an auxiliary...
Sampling and distortion tradeoffs for bandlimited periodic signals
, Article IEEE Transactions on Information Theory ; 2017 ; 00189448 (ISSN) ; Marvasti, F ; Sharif University of Technology
Abstract
In this paper, the optimal sampling strategies (uniform or nonuniform) and distortion tradeoffs for Gaussian bandlimited periodic signals with additive white Gaussian noise are studied. Our emphasis is on characterizing the optimal sampling locations as well as the optimal pre-sampling filter to minimize the reconstruction distortion. We first show that to achieve the optimal distortion, no pre-sampling filter is necessary for any arbitrary sampling rate. Then, we provide a complete characterization of optimal distortion for low and high sampling rates (with respect to the signal bandwidth). We also provide bounds on the reconstruction distortion for rates in the intermediate region. It is...
Compressed sensing block MAP-LMS adaptive filter for sparse channel estimation and a Bayesian Cramer-Rao bound
, Article Machine Learning for Signal Processing XIX - Proceedings of the 2009 IEEE Signal Processing Society Workshop, MLSP 2009, 2 September 2009 through 4 September 2009 ; 2009 ; 9781424449484 (ISBN) ; Babaie Zadeh, M ; Jutten, C ; Sharif University of Technology
Abstract
This paper suggests to use a Block MAP-LMS (BMAP-LMS) adaptive filter instead of an Adaptive Filter called MAP-LMS for estimating the sparse channels. Moreover to faster convergence than MAP-LMS, this block-based adaptive filter enables us to use a compressed sensing version of it which exploits the sparsity of the channel outputs to reduce the sampling rate of the received signal and to alleviate the complexity of the BMAP-LMS. Our simulations show that our proposed algorithm has faster convergence and less final MSE than MAP-LMS, while it is more complex than MAP-LMS. Moreover, some lower bounds for sparse channel estimation is discussed. Specially, a Cramer-Rao bound and a Bayesian...
Binary fading interference channel with no CSIT
, Article IEEE Transactions on Information Theory ; Volume 63, Issue 6 , 2017 , Pages 3565-3578 ; 00189448 (ISSN) ; Maddah Ali, M. A ; Avestimehr, A. S ; Zhu, Y ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2017
Abstract
We study the capacity region of the two-user binary fading (or erasure) interference channel, where the transmitters have no knowledge of the channel state information. We develop new inner bounds and outer bounds for this problem. We identify three regimes based on the channel parameters: weak, moderate, and strong interference regimes. Interestingly, this is similar to the generalized degrees of freedom of the two-user Gaussian interference channel, where transmitters have perfect channel knowledge. We show that for the weak interference regime, treating interference as erasure is optimal while for the strong interference regime, decoding interference is optimal. For the moderate...
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...