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capacity-regions
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New Achievable Rates In Frequency Hopped Spread Spectrum Systems
, M.Sc. Thesis Sharif University of Technology ; Marvasti, Farrokh (Supervisor)
Abstract
In this dissertation, we investigate the frequency hopped spread spectrum systems which are extensively used in many communication systems. We derive the capacity region of Synchronous Frequency Hopped Multiple Access (FHMA) channels (for any kind of noisy or nonselective fading environment) by using the side information which exists in the multi‐user detection. We assume that random hopping patterns are used by all the transmitters, and the common receiver knows the hopping patterns. We also compute the capacities of FHMA with and without power control for AWGN and noiseless MFSK (in particular BFSK) modulated systems and compare the ...
On the Capacity of Information Networks Utilizing Cognition and Cooperative Strategies
, Ph.D. Dissertation Sharif University of Technology ; Aref, Mohammad Reza (Supervisor)
Abstract
Interference management is one of the key issues in wireless networks wherein multiple source-destination pairs share the same medium and frequency band and interfere with each other. The exponentially growth in the number of wireless systems and services results in the spectrum shortage which has emerged the technologies that increase the spectral efficiency. Providing the users with cognition equipments in these networks enables them to sense the medium and use the obtained data to adapt their transmissions to cooperate with other users and improve their own rates as well as the others which results in the cognitive radio technology. In order to access the full potential of this technology,...
Application of Lattice Codes Over Channels with State
, M.Sc. Thesis Sharif University of Technology ; Behroozi, Hamid (Supervisor)
Abstract
Although in the network information theory most of results are based on applying random codes, one of the important challenges is to design linear structured codes that achieves the performance close to the performance of random codes. Recently, it is shown that lattice codes can be designed as good codes for quantization and also capacity-achieving in additive white Gaussian noise (AWGN) channel. Due to such a good performance, lattice codes can be designed properly and applied in various problems in network information theory.In this work, we study the performance of lattice codes for the following problems:1. Gaussian multiple access channel (MAC) with state: A joint source channel coding...
Analysis of Secret Key Agreement in The Channel Model with Side Information
, M.Sc. Thesis Sharif University of Technology ; Aref, Mohammad Reza (Supervisor)
Abstract
In this thesis, the problem of secret key agreement in the channel model with side information is studiedx. In order to investigate the problem, we consider three models according to the different ways of side information availability which are the state-dependent broadcast channel; the state-dependent broadcast channel in presence of public channel and the state-dependent wiretap channel with degraded versions of the channel state information.For the problem of secret key agreement in broadcast channels, two models, the state-dependent wiretap channel and state-dependent three receivers broadcast channel, are considered. We obtain inner and outer bounds of the secret key capacity region for...
Performance Analysis of Lattice Codes on Interference and Relay Channels
, M.Sc. Thesis Sharif University of Technology ; Behroozi, Hamid (Supervisor)
Abstract
Random codes can achieve the capacity region of so many channels like AWGN channel, multiple access channel (MAC), etc. Recently, it is shown that these codes cannot achieve any positive rate for some channels such as doubly dirty MAC.Because of this fact and also practical consideration, structured codes have been introduced recently. It is shown that one of the structured codes, referred to as lattice codes, can achieve positive rates for doubly dirty MAC. These codes can also achieve the capacity of AWGN channel, MAC and Broadcast channel. For these reasons, in this work we analyze the performance of lattice codes over relay channels as well as interference channels. Here, we implement...
Multiple access channel with common message and secrecy constraint
, Article IET Communications ; Volume 10, Issue 1 , 2016 , Pages 98-110 ; 17518628 (ISSN) ; Akhbari, B ; Ahmadian Attari, M ; Aref, M. R ; Sharif University of Technology
Institution of Engineering and Technology
Abstract
The authors study the problem of secret communication over a multiple-access channel with a common message. Here, the authors assume that two transmitters have confidential messages, which must be kept secret from the wiretapper (the second receiver), and both of them have access to a common message which can be decoded by the two receivers. The authors call this setting as multiple-access wiretap channel with common message (MAWC-CM). For this setting, the authors derive general inner and outer bounds on the secrecy capacity region for the discrete memoryless case and show that these bounds meet each other for a special case called the switch channel. As well, for a Gaussian version of...
On the duality of additivity and tensorization
, Article IEEE International Symposium on Information Theory - Proceedings, 14 June 2015 through 19 June 2015 ; Volume 2015-June , 2015 , Pages 2381-2385 ; 21578095 (ISSN) ; 9781467377041 (ISBN) ; Gohari, A ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2015
Abstract
A function is said to be additive if, similar to mutual information, expands by a factor of n, when evaluated on n i.i.d. repetitions of a source or channel. On the other hand, a function is said to satisfy the tensorization property if it remains unchanged when evaluated on i.i.d. repetitions. Additive rate regions are of fundamental importance in network information theory, serving as capacity regions or upper bounds thereof. Tensorizing measures of correlation have also found applications in distributed source and channel coding problems as well as the distribution simulation problem. Prior to our work only two measures of correlation, namely the hypercontractivity ribbon and maximal...
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...
Dynamic index coding gain over a complete bi-directional side information graph
, Article IWCIT 2016 - Iran Workshop on Communication and Information Theory, 3 May 2016 through 4 May 2016 ; 2016 ; 9781509019229 (ISBN) ; Mojahedian, M. M ; Aref, M. R ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2016
Abstract
Dynamic Index coding as a generalization of the traditional index coding problem, deals with transmission of some dynamic data flows in the presence of side information. For a dynamic index coding system, the set of average flow rates for which the system can be stable is named Code-Constraint Capacity region. In this paper, we identify the code-constraint capacity region for a dynamic index coding problem with complete bi-directional side information graph. Furthermore, we introduce the concept of Dynamic Index Coding Gain to quantify the improvement resulted from the dynamic index coding with respect to uncoded transmissions. We also provide some corollaries about system performance...
Information theory of mixed population genome-wide association studies
, Article 2018 IEEE Information Theory Workshop, ITW 2018, 25 November 2018 through 29 November 2018 ; 2019 ; 9781538635995 (ISBN) ; Maddah Ali, M. A ; Motahari, S. A ; Sun Yat-Sen University ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2019
Abstract
Genome-Wide Association Study (GWAS) addresses the problem of associating subsequences of individuals' genomes to the observable characteristics called phenotypes. In a genome of length G, it is observed that each characteristic is only related to a specific subsequence of it with length L, called the causal subsequence. The objective is to recover the causal subsequence, using a dataset of N individuals' genomes and their observed characteristics. Recently, the problem has been investigated from an information theoretic point of view in [1]. It has been shown that there is a threshold effect for reliable learning of the causal subsequence at Gh ( N L/G ) by characterizing the capacity of...
A lattice-based compress-and-forward strategy for Gaussian two-way relay channel with direct links
, Article IEEE Wireless Communications Letters ; Volume 5, Issue 5 , 2016 , Pages 500-503 ; 21622337 (ISSN) ; Mardani, S ; Behroozi, H ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
Abstract
In this letter, the Gaussian two-way relay channel with direct links is investigated in which two users aim at exchanging their messages with the help of a relay node. We propose a new lattice-based compress-and-forward strategy and obtain its achievable rate-region. We show that the proposed scheme is superior to all previously known achievable schemes for channel gains larger than one. In particular, under the symmetric case, the proposed scheme is able to achieve a capacity region within 0.5 bit or (1/2)log 3 ≅ 0.79 bit, depending on the power of the relay
Three-user cognitive interference channel: Capacity region with strong interference
, Article IET Communications ; Volume 6, Issue 13 , 2012 , Pages 2099-2107 ; 17518628 (ISSN) ; Akhbari, B ; Aref, M. R ; Sharif University of Technology
IET
2012
Abstract
This study investigates the capacity region of a three-user cognitive radio network with two primary users and one cognitive user. A three-user cognitive interference channel (C-IFC) is proposed by considering a three-user interference channel (IFC) where one of the transmitters has cognitive capabilities and knows the messages of the other two transmitters in a non-causal manner. First, two inner bounds on the capacity region of the three-user C-IFC are obtained based on using the schemes which allow all receivers to decode all messages with two different orders. Next, two sets of conditions are derived, under which the capacity region of the proposed model coincides with the capacity...
Simultaneously generating multiple keys in a four-terminal network
, Article IET Information Security ; Volume 6, Issue 3 , 2012 , Pages 190-201 ; 17518709 (ISSN) ; Salimi, S ; Aref, M. R ; Sharif University of Technology
IET
2012
Abstract
A source model including four terminals is considered, where three simultaneously generating three types of keys are intended. Terminals 1, 2 and 3 wish to share a common key, the secret key, which should be kept secret from terminal 4 and simultaneously terminals 1 and 2 intend to share a private key with terminal 3, which should be kept secret from each other. Also, all the keys should be concealed from terminal 4 (the external wiretapper). The authors assume that all terminals including the external wiretapper have access to distinct correlated i.i.d. sources; there is also a noiseless public channel with unlimited capacity among the terminals. The authors have investigated the model on...
On the transmission strategies for the two-user state-dependent gaussian interference channel
, Article Proceedings of the International Symposium on Wireless Communication Systems ; Aug , 2013 , Pages 224-228 ; 21540217 (ISSN) ; 9783800735297 (ISBN) ; Behroozi, H ; Sharif University of Technology
IEEE Computer Society
2013
Abstract
In this paper, we study a general additive state-dependent Gaussian interference channel (ASD-GIC) where we consider two-user interference channel with two independent states known non-causally at both transmitters, but unknown to either of the receivers. A special case, where there is a common additive state is studied in [1], [2], where it is shown that the gap between the achievable symmetric rate and the upper bound is less than 1 /4 bits for the strong interference case. Here, we also consider the case where interference link gains satisfy a12 ≥ N1/ N2 and a 21 ≥ N2/ N1 (Ni is the channel noise variance) and each channel state has an unbounded variance [3], which is referred to as the...
Coordination via a relay
, Article IEEE International Symposium on Information Theory - Proceedings ; 2012 , Pages 3048-3052 ; 9781467325790 (ISBN) ; Yassaee, M. H ; Gohari, A ; Aref, M. R ; Sharif University of Technology
IEEE
2012
Abstract
In this paper, we study the problem of coordinating two nodes which can only exchange information via a relay at limited rates. The nodes are allowed to do a two-round interactive two-way communication with the relay, after which they should be able to generate i.i.d. copies of two random variables with a given joint distribution within a vanishing total variation distance. We prove inner and outer bounds on the coordination capacity region for this problem. Our inner bound is proved using the technique of "output statistics of random binning" that has recently been developed by Yassaee, et al
On the secrecy capacity of 3-receiver Broadcast Channel with causal states and conferencing
, Article IEEE International Symposium on Information Theory - Proceedings ; 2012 , Pages 1167-1171 ; 9781467325790 (ISBN) ; Aref, M. R ; Sharif University of Technology
IEEE
2012
Abstract
We investigate the secrecy capacity region of 2-receiver, 1-eavesdropper Broadcast Channel (BC) with two causal states and conferencing decoders. The encoder sends two messages, one of them for both legitimate receivers and the other one for the first legitimate receiver. It keeps these messages secret from the eavesdropper. Each state is causally available at the corresponding receiver, while both states are known causally at the encoder. Each receiver wishes to send the state which is not available at the other receiver, through a noiseless link with limited capacity. We find an inner bound on the secrecy capacity region of this channel. The achievability scheme employs block Markov coding...
Compound multiple access channel with confidential messages
, Article 2014 IEEE International Conference on Communications, ICC 2014 ; 10-14 June 2014 , 2014 , Pages 1922-1927 ; ISBN: 9781479920037 ; Akhbari, B ; Ahmadian Attari, M ; Aref, M. R ; Sharif University of Technology
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 that is only decoded by its corresponding receiver and kept secret from the other receiver. For this proposed setting (compound MAC with confidential messages), we derive general inner and outer bounds on the secrecy capacity region. 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 Gaussian case, we illustrate the comparison between achievable rate...
On marton's inner bound and its optimality for classes of product broadcast channels
, Article IEEE Transactions on Information Theory ; Vol. 60, Issue. 1 , 2014 , pp. 22-41 ; ISSN: 0018-9448 ; Gohari, A ; Nair, C ; Yu, Y ; Sharif University of Technology
Abstract
Marton's inner bound is the tightest known inner bound on the capacity region of the broadcast channel. It is not known, however, if this bound is tight in general. One approach to settle this key open problem in network information theory is to investigate the multiletter extension of Marton's bound, which is known to be tight in general. This approach has become feasible only recently through the development of a new method for bounding cardinalities of auxiliary random variables by Gohari and Anantharam. This paper undertakes this long overdue approach to establish several new results, including 1) establishing the optimality of Marton's bound for new classes of product broadcast...
On marton's inner bound for the general broadcast channel
, Article IEEE Transactions on Information Theory ; Volume 60, Issue 7 , 2014 , Pages 3748-3762 ; ISSN: 00189448 ; Gamal, A. E ; Anantharam, V ; Sharif University of Technology
Abstract
We establish several new results on Marton's inner bound on the capacity region of the general broadcast channel. Inspired by the fact that Marton's coding scheme without superposition coding is optimal in the Gaussian case, we consider the class of binary input degraded broadcast channels with no common message that have the same property. We characterize this class. We also establish new properties of Marton's inner bound that help restrict the search space for computing the Marton sum rate. In particular, we establish an extension of the XOR case of the binary inequality of Nair, Wang, and Geng
On dimension bounds for auxiliary quantum systems
, Article IEEE Transactions on Information Theory ; Vol. 60, Issue. 1 , Jan , 2014 , PP . 368-387 ; ISSN: 00189448 ; Gohari, A ; Sharif University of Technology
Abstract
Expressions of several capacity regions in quantum information theory involve an optimization over auxiliary quantum registers. Evaluating such expressions requires bounds on the dimension of the Hilbert space of these auxiliary registers, for which no nontrivial technique is known; we lack a quantum analog of the Carathéodory theorem. In this paper, we develop a new non-Carathéodory-type tool for evaluating expressions involving a single quantum auxiliary register and several classical random variables. As we show, such expressions appear in problems of entanglement-assisted Gray-Wyner and entanglement-assisted channel simulation, where the question of whether entanglement helps in these...