Loading...
Search for:
communication-channels--information-theory
0.008 seconds
Total 149 records
Cooperative relay broadcast channels with partial causal channel state information
, Article IET Communications ; Volume 5, Issue 6 , 2011 , Pages 760-774 ; 17518628 (ISSN) ; Khosravi Farsani, R ; Aref, M. R ; Sharif University of Technology
Abstract
The authors consider 'partially' and 'fully cooperative' state-dependent relay broadcast channels (RBCs), where partial channel state information (CSI) is available at the nodes causally. First, the authors derive an achievable rate region for general discrete memoryless partially cooperative RBC (PC-RBC) with partial causal CSI, by exploiting superposition coding at the source, decode-and-forward scheme at the relay and Shannon's strategy at the source and the relay. Then, they establish the capacity region of the discrete memoryless physically degraded PC-RBC with partial causal CSI. They also characterise the capacity region of discrete memoryless PC-RBC with feedback and partial causal...
Lattice-coded cooperation protocol for the half-duplex Gaussian two-way relay channel
, Article Eurasip Journal on Wireless Communications and Networking ; Volume 2015, Issue 1 , 2015 , Pages 1-18 ; 16871472 (ISSN) ; Behroozi, H ; Sharif University of Technology
Abstract
This paper studies the Gaussian two-way relay channel (GTWRC), where two nodes exchange their messages with the help of a half-duplex relay. We investigate a cooperative transmission protocol, consisting of four phases: multiple access (MA) phase, broadcast (BC) phase, and two cooperative phases. For this setup, we propose a new transmission scheme based on superposition coding for nested lattice codes, random coding, and jointly typical decoding. This scheme divides the message of each node into two parts, referred to as satellite codeword and cloud center. Depending on the phase type, the encoder sends a linear combination of satellite codewords or cloud centers. For comparison, a rate...
On optimum asymptotic multiuser efficiency of randomly spread CDMA
, Article IEEE Transactions on Information Theory ; Volume 61, Issue 12 , 2015 , Pages 6635-6642 ; 00189448 (ISSN) ; Müller, R. R ; Marvasti, F ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2015
Abstract
We extend the result by Tse and Verdú on the optimum asymptotic multiuser efficiency of randomly spread code division multiple access (CDMA) with binary phase shift keying input. Random Gaussian and random binary antipodal spreading are considered. We obtain the optimum asymptotic multiuser efficiency of a K-user system with spreading gain N when K and N → ∞ and the loading factor, (K/N) , grows logarithmically with K under some conditions. It is shown that the optimum detector in a Gaussian randomly spread CDMA system has a performance close to the single user system at high signal-to-noise ratio when K and N → ∞ and the loading factor, (K/N), is kept less than (log3 K/2). Random binary...
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...
Cohering and decohering power of quantum channels
, Article Physical Review A - Atomic, Molecular, and Optical Physics ; Volume 92, Issue 3 , 2015 ; 10502947 (ISSN) ; Karimipour, V ; Sharif University of Technology
American Physical Society
2015
Abstract
We introduce the concepts of cohering and decohering power of quantum channels. Using the axiomatic definition of the coherence measure, we show that the optimization required for calculations of these measures can be restricted to pure input states and hence greatly simplified. We then use two examples of this measure, one based on the skew information and the other based on the l1 norm; we find the cohering and decohering measures of a number of one-, two-, and n-qubit channels. Contrary to the view at first glance, it is seen that quantum channels can have cohering power. It is also shown that a specific property of a qubit unitary map is that it has equal cohering and decohering power in...
An efficient DVS scheme for on-chip networks using reconfigurable Virtual Channel allocators
, Article Proceedings of the International Symposium on Low Power Electronics and Design, 22 July 2015 through 24 July 2015 ; Volume 2015-September , July , 2015 , Pages 249-254 ; 15334678 (ISSN) ; 9781467380096 (ISBN) ; Mirhosseini, A ; Aghilinasab, H ; Sarbazi Azad, H ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2015
Abstract
Network-on-Chip (NoC) is a key element in the total power consumption of a chip multiprocessor. Dynamic Voltage Scaling is a promising method for power saving in NoCs since it contributes to reduction in both static and dynamic power consumptions. In this paper, we propose a novel scheme to reduce on-chip network power consumption when the number of Virtual Channels (VCs) with active allocation requests per cycle is less than the number of total VCs. In our method, we introduce a reconfigurable arbitration logic which can be configured to have multiple latencies and hence, multiple slack times. The increased slack times are then used to reduce the supply voltage of the routers in order to...
Secret key cryptosystem based on non-systematic polar codes
, Article Wireless Personal Communications ; Volume 84, Issue 2 , September , 2015 , Pages 1345-1373 ; 09296212 (ISSN) ; Aref, M. R ; Eghlidos, T ; Sharif University of Technology
Springer New York LLC
2015
Abstract
Polar codes are a new class of error correcting linear block codes, whose generator matrix is specified by the knowledge of transmission channel parameters, code length and code dimension. Moreover, regarding computational security, it is assumed that an attacker with a restricted processing power has unlimited access to the transmission media. Therefore, the attacker can construct the generator matrix of polar codes, especially in the case of binary erasure channels, on which this matrix can be easily constructed. In this paper, we introduce a novel method to keep the generator matrix of polar codes in secret in a way that the attacker cannot access the required information to decode the...
Optimal MIMO waveform design with controlled characteristics
, Article Proceedings International Radar Symposium, 24 June 2015 through 26 June 2015 ; Volume 2015-August , 2015 , Pages 1141-1146 ; 21555753 (ISSN) ; 9783954048533 (ISBN); 9783954048533 (ISBN); 9783954048533 (ISBN) ; Radmard, M ; Nayebi, M. M ; Bastani, M. H ; Rohling, H ; Rohling, H ; Rohling, H ; Sharif University of Technology
IEEE Computer Society
2015
Abstract
In a MIMO (Multiple Input Multiple Output) radar system, proper design of transmit signal and receive filter is an advantageous tool to improve the detection performance. Thus, in this paper, we consider the problem of transmit code and receive filter design, in order to maximize the Signal to Noise Ratio (SNR) at the receiver while enforcing a similarity constraint between the transmit space-time code (STC) and a reference STC which has a desirable ambiguity function. We will show that by solving such constrained optimization problem through successive iterations, our proposed method leads to satisfactory results
On Körner-Marton's sum modulo two problem
, Article IWCIT 2015 - Iran Workshop on Communication and Information Theory, 6 May 2015 through 7 May 2015 ; May , 2015 ; 9781479982356 (ISBN) ; Gohari, A ; Aref, M. R ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2015
Abstract
In this paper we study the sum modulo two problem proposed by Körner and Marton. In this source coding problem, two transmitters who observe binary sources X and Y, send messages of limited rate to a receiver whose goal is to compute the sum modulo of X and Y. This problem has been solved for the two special cases of independent and symmetric sources. In both of these cases, the rate pair (H(X|Y), H(Y|X)) is achievable. The best known outer bound for this problem is a conventional cut-set bound, and the best known inner bound is derived by Ahlswede and Han using a combination of Slepian-Wolf and Körner-Marton's coding schemes. In this paper, we propose a new outer bound which is strictly...
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...
An energy-efficient virtual channel power-gating mechanism for on-chip networks
, Article Proceedings -Design, Automation and Test in Europe, DATE, 9 March 2015 through 13 March 2015 ; Volume 2015-April , March , 2015 , Pages 1527-1532 ; 15301591 (ISSN) ; 9783981537048 (ISBN) ; Sadrosadati, M ; Fakhrzadehgan, A ; Modarressi, M ; Sarbazi Azad, H ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2015
Abstract
Power-gating is a promising method for reducing the leakage power of digital systems. In this paper, we propose a novel power-gating scheme for virtual channels in on-chip networks that uses an adaptive method to dynamically adjust the number of active VCs based on the on-chip traffic characteristics. Since virtual channels are used to provide higher throughput under high traffic loads, our method sets the number of virtual channel at each port selectively based on the workload demand, thereby do not negatively affect performance. Evaluation results show that by using this scheme, about 40% average reduction in static power consumption can be achieved with negligible performance overhead
Lossy transmission of correlated sources over multiple-access wiretap channels
, Article IET Communications ; Volume 9, Issue 6 , 2015 , Pages 754-770 ; 17518628 (ISSN) ; Aref, M. R ; Sharif University of Technology
Institution of Engineering and Technology
2015
Abstract
In this study, the authors study lossy communication of correlated sources over a multiple-access wiretap channel (MAC-WT). Consider a system with two transmitters, a receiver and an eavesdropper. There are two correlated sources where each of them is observed by the corresponding transmitter, separately. Each transmitter wishes to describe its source sequence to the receiver with a desired distortion. The sources need to be kept secret from the eavesdropper. They find an achievable region for the MAC-WT with correlated sources by separation. A joint source-channel coding scheme for the MAC-WT is also proposed. They consider lossy communication of a bivariate Gaussian source over Gaussian...
Compute-and-forward two-way relaying
, Article IET Communications ; Volume 9, Issue 4 , 2015 , Pages 451-459 ; 17518628 (ISSN) ; Hejazi, M ; Nasiri Kenari, M ; Sharif University of Technology
Institution of Engineering and Technology
2015
Abstract
In this study, a new two-way relaying scheme based on compute-and-forward (CMF) framework and relay selection strategies is proposed, which provides a higher throughput than the conventional two-way relaying schemes. Two cases of relays with or without feedback transmission capability are considered. An upper bound on the computation rate of each relay is derived, and based on that, a lower bound on the outage probability of the system is presented assuming block Rayleigh fading channels. Numerical results show that while the average sum rate of the system without feedback, named as max-CMF (M-CMF), reaches the derived upper bound only in low SNRs, that of the system with feedback, named as...
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...
Crosstalk modeling to predict channel delay in Network-on-Chips
, Article Proceedings - IEEE International Conference on Computer Design: VLSI in Computers and Processors, 3 October 2010 through 6 October 2010 ; October , 2010 , Pages 396-401 ; 10636404 (ISSN) ; 9781424489350 (ISBN) ; Miremadi, S. G ; Shafaei, M ; Sharif University of Technology
2010
Abstract
Communication channels in Network-on-Chips (NoCs) are highly susceptible to crosstalk faults due to the use of nano-scale VLSI technologies in the fabrication of NoCs. Crosstalk faults cause variable timing delay in NoC channels based on the patterns of transitions appearing on the channels. This paper proposes an analytical model to estimate the timing delay of an NoC channel in the presence of crosstalk faults. The model calculates expected number of 4C, 3C, 2C, and 1C transition patterns to predict delay of a K-bit communication channel. The model is applicable for both non-protected channels and channels which are protected by crosstalk mitigation methods. Spice simulations are done in a...
Compress-and-forward strategy for causal cognitive interference 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 1088-1095 ; 9781424469406 (ISBN) ; Akhbari, B ; Aref, M. R ; Sharif University of Technology
2010
Abstract
In this paper, we consider Causal Cognitive Interference Channel (CC-IFC), wherein the cognitive user overhears the channel and exploits knowledge of the primary user's message from the causally received signals. We propose a coding scheme which combines Compress-and-Forward (CF) strategy with Marton coding with common information at the cognitive user. Rate splitting for messages at both transmitters is used to have a collaborative strategy. Moreover, the cognitive user compresses its channel observation using Wyner-Ziv coding and splits the index of its compressed signal. Then, the cognitive user having common information to both receivers and private information to each of them, jointly...
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