Loading...
Search for:
communication-channels--information-theory
0.016 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...
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
Cooperative relay 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 1064-1069 ; 9781424469406 (ISBN) ; Aref, M. R ; Ahmadian Attari, M ; Sharif University of Technology
2010
Abstract
The cooperative relay cognitive interference channel (RCIC) is a four-node network with two source nodes (primary source and cognitive source) and two destination nodes, in which sources try to communicate at certain rates with their corresponding destinations simultaneously through a common medium and each destination can act as a relay to assist the other one. For the partially cooperative RCIC (PC-RCIC), in which only one of the destinations (corresponding to the cognitive source) acts as a relay, we derive an achievable rate region based on using rate splitting and superposition coding at the cognitive source, and using decode-and-forward scheme at the relay. For the degraded PC-RCIC, we...
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...
Achievable rate region for multiple-access-relay-networks
, Article IET Communications ; Volume 4, Issue 15 , October , 2010 , Pages 1792-1798 ; 17518628 (ISSN) ; Ghabeli, L ; Aref, M. R ; Sharif University of Technology
Abstract
The authors introduce a generalisation of the multiple-access-relay-channel (MARC) called multiple-access-relay-network (MARN). The MARC model was first introduced by Kramer et al. and consists of many transmitters, one receiver and only one relay. In the MARN, there are many transmitters, many relays and one receiver. The authors obtained an achievable rate region for MARN by considering partial decode-and-forward (PDF) strategy at the relays. They showed that the region obtained using PDF strategy subsumes the region obtained by Kramer et al. for MARC. In the proposed coding scheme, the authors take advantage of PDF strategy based on regular encoding/backward decoding strategy. They also...
A game-theoretic approach for power allocation in bidirectional cooperative communication
, Article IEEE Wireless Communications and Networking Conference, WCNC, 18 April 2010 through 21 April 2010 ; April , 2010 ; 15253511 (ISSN) ; 9781424463985 (ISBN) ; Pakravan, M ; Sedghi, H ; Sharif University of Technology
2010
Abstract
Cooperative communication exploits wireless broadcast advantage to confront the severe fading effect on wireless communications. Proper allocation of power can play an important role in the performance of cooperative communication. In this paper, we propose a distributed gametheoretical method for power allocation in bidirectional cooperative communication networks. In this work, we consider two nodes as data sources who want to cooperate in sending data to the destination. In addition to being data source, each source node has to relay the other's data. We answer the question: How much power each node contributes for relaying other node's data? We use Stackelberg game which is an...
Secrecy capacity of wiretap channel for a new scenario and designing code for wiretap channel
, Article Proceedings - 2010 18th Iranian Conference on Electrical Engineering, ICEE 2010, 11 May 2010 through 13 May 2010 ; 2010 , Pages 183-187 ; 9781424467600 (ISBN) ; Salimi, S ; Salmasizadeh, M ; Sharif University of Technology
Abstract
The concept of information theoretic security is introduced. Secrecy capacity of two receiver broadcast channel for a new scenario is derived in which it is assumed that the legitimate receiver has access to a noisy version of eavesdroppers channel outputs. Also the ideas of code designing to achieve zero error on main channel and perfect secrecy on the eavesdropper's channel, without invoking complicated capacity achieving codes are provided
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)...
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...
A polynomial algorithm for partitioning problems
, Article Transactions on Embedded Computing Systems ; Volume 9, Issue 4 , 2010 ; 15399087 (ISSN) ; Jahangir, A. H ; Sharif University of Technology
2010
Abstract
This article takes a theoretical approach to focus on the algorithmic properties of hardware/software partitioning. It proposes a method with polynomial complexity to find the global optimum of an NP-hard model partitioning problem for 75% of occurrences under some practical conditions. The global optimum is approached with a lower bound distance for the remaining 25%. Furthermore, this approach ensures finding the 2-approximate of the global optimum partition in 97% of instances where technical assumptions exist. The strategy is based on intelligently changing the parameters of the polynomial model of the partitioning problem to force it to produce (or approach) the exact solution to the...
Bit error probability analysis of UWB communications with a relay node
, Article IEEE Transactions on Wireless Communications ; Volume 9, Issue 2 , 2010 , Pages 802-813 ; 15361276 (ISSN) ; Nasiri Kenari, M ; Aazhang, B ; Sharif University of Technology
2010
Abstract
In this paper, the extension of cooperative communication to the context of TH-UWB is investigated. In particular, the average bit error probability (BEP) is provided for cooperative TH-UWB systems with decode-and-forward relaying protocol. In the considered relay network, UWB links among the nodes are modeled according to IEEE 802.15.4a standards. Our methodology is based on computing the Characteristic Function (CF) of the decision variable at the destination terminal. We use Gaussian quadrature numerical method to approximate the CF of interference component appeared in decision variable term. This technique permits to predict the system performance in different IEEE 802.15.4a defined...
On the capacity region of semi-deterministic multiple-access-relay-networks
, Article 2010 Australian Communications Theory Workshop, AusCTW 2010, Canberra, ACT, 3 February 2010 through 5 February 2010 ; 2010 , Pages 54-58 ; 9781424454334 (ISBN) ; Ghabeli, L ; Aref, M. R ; ANU - The Australian National University; ACoRN - ARC Communications Research Network; NICTA; UniSA; CSIRO ; Sharif University of Technology
2010
Abstract
In this paper, we introduce a generalization of the Multiple-Access-Relay- Channel (MARC) called Multiple-Access-Relay-Network (MARN). In the proposed network, there are many transmitters, many relays and one receiver. The MARC model was first introduced by Kramer and consists of many transmitters, one receiver and only one relay.We also define semi-deterministic MARN, in which the output of the link between each transmitter and each relay is a deterministic function of the transmitter's input. We first obtain an achievable rate region for MARN by considering Partial Decode-and-Forward (PDF) strategy at the relays. Then we show that in semi-deterministic MARN, the proposed achievable rate...
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"....
An achievable rate for relay networks based on compress-and-forward strategy
, Article IEEE Communications Letters ; Volume 14, Issue 4 , 2010 , Pages 279-281 ; 10897798 (ISSN) ; Ghabeli, L ; Aref, M. R ; Sharif University of Technology
Abstract
Compress-and-Forward (CF) is a well-known coding strategy proposed for relay channels. Few works which were done about the generalization of the CF strategy to the relay networks, are based on irregular encoding/successive decoding. In this paper, a new generalization of the CF strategy to the relay networks based on regular encoding/backward decoding is presented. In general, backward decoding has been shown to yield higher rates in comparison with successive decoding. Here we will investigate the performance of backward decoding in our problem and show that our achievable rate includes the previously proposed rates