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shariatpanahi--peyman
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A Realistic Urban Mobility Model for Mobile Ad Hoc Network
, M.Sc. Thesis Sharif University of Technology ; Manzuri, Mohammad Taghi (Supervisor)
Abstract
A Mobile Ad hoc NETwork (MANET) is a set of wireless mobile nodes that form a self configured network. MANETs do not have infrastructure and are not currently deployed on large scales. So research in this area is simulation based. Mobility model in a mobile ad hoc network explains the movement pattern of mobile users and is designed to describe the change of their location, velocity and acceleration over time. One of the challenges in this field is the definition of a common mobility model that provides an accurate and realistic movement description of mobile nodes. In this thesis we want to study the mobility pattern of vehicles on Kish Island and compare it with different kinds of...
Performance Ehancement of Congestion Control Algorithm Through Traffic Flow Istinction
, M.Sc. Thesis Sharif University of Technology ; Jahangir, Amir Hossein (Supervisor)
Abstract
Congestion is an important issue in the network environment. To keep stable the perfor-mance of the network, congestion control algorithms have been extensively studied. Queue management method employed by the routers is one of the important issues in the congestion control study. Active Queue Management (AQM) has been proposed for early detection of congestion inside the network. AQM mechanisms control the queue length in a router by dropping arriving packets. The Random Early Detection (RED) is the most popular AQM mechanism used in routers on the Intenet to allow network users to simultaneously achieve high throughput and low average delay. The RED algorithm may cause heavy oscillation of...
Calculating Runoff Coefficient of Urmia Lake Basin by Empirical Models and Remot Sensing (RS) Technology
, M.Sc. Thesis Sharif University of Technology ; Tajrishy, Masoud (Supervisor) ; Arasteh, Peyman (Co-Advisor)
Abstract
Estimation of runoff in the ungauged basins is a challenge for hydrologists. The main objective of this research is to produce runoff coefficient map using SCS-CN (1972) and Kennessey (1930) as empirical models to for Urmia Lake basin between for 2006-2011.Both SCS-CN and Kennessey methods use slope, land use, and soil permeability data to estimate surface runoff. Accuracy of each model is tested along with the observed runoff using the Root Mean Square Error (RMSE).Urmia Lake basin includes about 400,000 hectares irrigated land, which constitutes around 10 percent of the entire basin area. To exclude the anthropological activities from the estimations, methods were applied only for 28...
On reliable routing in wireless networks with diversity
, Article 4th IEEE and IFIP International Conference on Wireless and Optical Communications Networks, WOCN 2007, Singapore, 2 July 2007 through 4 July 2007 ; 2007 ; 1424410045 (ISBN); 9781424410040 (ISBN) ; Foroughmand Aarabi, H ; Sharif University of Technology
2007
Abstract
Many forms of diversity have been exploited in communication systems to combat fading nature of wireless channels. Some examples are time diversity, frequency diversity, space diversity and multiuser diversity. However, another form of diversity inherent in any wireless network, which is usually not exploited, is the diversity due to the shared medium of propagation. When in a network one node transmits to the other node, all the other nodes may hear this transmission and some of them can decode the data as well. This data can be used later to enhance the end-to-end network reliability. Previous works mostly consider some special cases of relay nodes configurations, not the general case. In...
Delay-aware scheduling in heterogeneous multiuser systems
, Article 2006 IEEE 7th Workshop on Signal Processing Advances in Wireless Communications, SPAWC, Cannes, 2 July 2006 through 5 July 2006 ; 2006 ; 078039710X (ISBN); 9780780397101 (ISBN) ; Hossein Khalaj, B ; Sharif University of Technology
2006
Abstract
Adaptive scheduling schemes which consider channel conditions are examples of cross-layer design in wireless networks. Research work which has been done on optimizing the performance of scheduling systems have shown that in each time slot it is better to transmit to the users with the best channel condition. In order to realize such schemes, most of earlier works have considered perfect feedback channels to send Channel State Information (CSI) to the scheduler. However, in practical systems there are some sources of imperfectness in feedback channels such as delay and quantization error. In this paper, we consider the effect of CSI delay on the performance of such systems. A new delay-aware...
Analysis of quantization effects on performance of hierarchical cooperation schemes in ad-hoc wireless networks
, Article Proceedings - Conference on Local Computer Networks, LCN ; 2011 , Pages 171-174 ; 9781612849287 (ISBN) ; Khalaj, B. H ; Sharif University of Technology
2011
Abstract
In this paper, we analyze the role of the number of quantization bits on the third phase of the hierarchical cooperation scheme proposed by Ozgur et al. in 2007. The hierarchical cooperation scheme has a digital architecture and requires quantization of MIMO (Multiple-Input Multiple-Output) observations in the third phase. The choice of the number of quantization bits Q has direct effect on the pre-constant factor of the network throughput. By increasing the number of quantization bits, the MIMO capacity in the second phase increases at the expense of higher computational complexity of the third phase. We investigate such trade-off and show that there is an optimum number of quantization...
Hydrodynamic Interactions of Artificial Reef using a Laboratory Model
,
M.Sc. Thesis
Sharif University of Technology
;
Borghei, Mahmoud
(Supervisor)
;
Aghtouman, Peyman
(Supervisor)
Abstract
Resources management is essential duo to sustainable development and marine resources limitations. There are several ways to restore coastal damaged ecosystems, one of the best and most cost effective solution is establishment of artificial reefs. A popular type of artificial reef is named Reef ball, a hollow hemisphere. In some regions these habitats has also been used as submerged breakwater. These structures recover and protect endangered species ecosystem although they provide aesthetic view to a beach. Main application of these structures is to provide a safe environment for marine creature. In this study initially Transmission coefficient variation in two-dimensional model experiments...
Information Flow in Random Wireless Networks
, Ph.D. Dissertation Sharif University of Technology ; Hossein Khalaj, Babak (Supervisor)
Abstract
We analyze the fundamental communication limits and capabilities of random wireless networks. In order to achieve this goal, we investigate and analyze efficient communication strategies in such networks. The traffic model considered is unicasting. Also, we consider two different channel models, namely, the geometric channel model and the random connections model.
In networks with random connection model, channel powers between different nodes are drawn from a common distribution in an independent manner. We assume an on-off strategy for operation of transmitters, and show that finding the optimum transmission strategy problem is an NP-hard problem. Thus, we propose a heuristic algorithm...
In networks with random connection model, channel powers between different nodes are drawn from a common distribution in an independent manner. We assume an on-off strategy for operation of transmitters, and show that finding the optimum transmission strategy problem is an NP-hard problem. Thus, we propose a heuristic algorithm...
Non-fixed scatterers and their effects on MIMO multicarrier fading communication channels
, Article 50th Annual IEEE Global Telecommunications Conference, GLOBECOM 2007, Washington, DC, 26 November 2007 through 30 November 2007 ; December , 2007 , Pages 3765-3769 ; 1424410436 (ISBN); 9781424410439 (ISBN) ; Gazor, S ; Shariatpanahi, P ; Sharif University of Technology
2007
Abstract
There are two types of scatterers in a multipath propagation environment: fixed and non-fixed scatterers. Fixed scatterers like buildings, mountains and tree stems do not move, while non-fixed (moving) scatterers like cars, people and tree leaves move from their initial positions. In addition to different movements of the mobile station (MS) that cause different kinds of Doppler fading, movements of non-fixed scatterers are also anticipated to generate other kinds of fading/correlation. This fading changes depend on the type of the propagation environment and the type of movements of local surrounding scatterers. In this paper we characterize these effects in terms of temporal correlations....
Feedback bit reduction for antenna selection methods in wireless systems
, Article 2005 13th IEEE International Conference on Networks jointly held with the 2005 7th IEEE Malaysia International Conference on Communications, Kuala Lumpur, 16 November 2005 through 18 November 2005 ; Volume 1 , 2005 , Pages 229-233 ; 1424400007 (ISBN); 9781424400003 (ISBN) ; Babadi, B ; Hossein Khalaj, B ; Sharif University of Technology
2005
Abstract
A well known method to reduce the intrinsic complexity of Multiple Input Multiple Output (MIMO) systems is to choose a subset of available antennas which have stronger links than the others, in order to perform the specified MIMO algorithm. The data resulted from the antenna selection process (at the receiver side) is sent back to the transmitter side via a feedback channel. There seems to be a need to reduce the number of feedack bits, specially when the number of antennas is not small. In this paper, we investigate the problem of reducing the number of feedback bits in antenna selection techniques. We've proposed two methods using vector quantization techniques to perform feedback bit...
Anticorrosion properties of smart coating based on polyaniline nanoparticles/epoxy-ester system
, Article Progress in Organic Coatings ; Volume 75, Issue 4 , 2012 , Pages 502-508 ; 03009440 (ISSN) ; Shojaei, A ; Shariatpanahi, H ; Neshati, J ; Sharif University of Technology
2012
Abstract
In this study, the anticorrosive effect of dodecylbenzenesulfonicacid-doped polyaniline nanoparticles [n-PANI (DBSA)] as a conductive polymer was investigated using electrochemical impedance spectroscopy (EIS) and X-ray photoelectron spectroscopy (XPS) techniques. Initially, the n-PANI (DBSA) were successfully synthesized via inverse microemulsion polymerization leading to the spherical nanoparticles with an average diameter less than 30 nm. Two coating systems including 1 wt% n-PANI(DBSA) blended epoxy ester (n-PANI(DBSA)/EPE) and neat epoxy ester (EPE) were coated on the carbon steal substrate. The anticorrosion performance of the prepared coatings was studied using EIS measurement in 3.5%...
Storage, communication, and load balancing trade-off in distributed cache networks
, Article IEEE Transactions on Parallel and Distributed Systems ; 2017 ; 10459219 (ISSN) ; Pourmiri, A ; Shariatpanahi, S. P ; Sharif University of Technology
2017
Abstract
We consider load balancing in a network of caching servers delivering contents to end users. Randomized load balancing via the so-called power of two choices is a well-known approach in parallel and distributed systems. In this framework, we investigate the tension between storage resources, communication cost, and load balancing performance. To this end, we propose a randomized load balancing scheme which simultaneously considers cache size limitation and proximity in the server redirection process. IEEE
Storage, communication, and load balancing trade-off in distributed cache networks
, Article IEEE Transactions on Parallel and Distributed Systems ; Volume 29, Issue 4 , April , 2018 , Pages 943-957 ; 10459219 (ISSN) ; Pourmiri, A ; Shariatpanahi, S. P ; Sharif University of Technology
IEEE Computer Society
2018
Abstract
We consider load balancing in a network of caching servers delivering contents to end users. Randomized load balancing via the so-called power of two choices is a well-known approach in parallel and distributed systems. In this framework, we investigate the tension between storage resources, communication cost, and load balancing performance. To this end, we propose a randomized load balancing scheme which simultaneously considers cache size limitation and proximity in the server redirection process. In contrast to the classical power of two choices setup, since the memory limitation and the proximity constraint cause correlation in the server selection process, we may not benefit from the...
Proximity-Aware balanced allocations in cache networks
, Article 31st IEEE International Parallel and Distributed Processing Symposium, IPDPS 2017, 29 May 2017 through 2 June 2017 ; 2017 , Pages 1068-1077 ; 9781538639146 (ISBN) ; Jafari Siavoshan, M ; Shariatpanahi, S. P ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2017
Abstract
We consider load balancing in a network of caching servers delivering contents to end users. Randomized load balancing via the so-called power of two choices is a well-known approach in parallel and distributed systems that reduces network imbalance. In this paper, we propose a randomized load balancing scheme which simultaneously considers cache size limitation and proximity in the server redirection process. Since the memory limitation and the proximity constraint cause correlation in the server selection process, we may not benefit from the power of two choices in general. However, we prove that in certain regimes, in terms of memory limitation and proximity constraint, our scheme results...
Multi-antenna coded caching
, Article IEEE International Symposium on Information Theory - Proceedings, 25 June 2017 through 30 June 2017 ; 2017 , Pages 2113-2117 ; 21578095 (ISSN) ; 9781509040964 (ISBN) ; Caire, G ; Khalaj, B. H ; Sharif University of Technology
2017
Abstract
In this paper we consider a single-cell downlink scenario where a multiple-antenna base station delivers contents to multiple cache-enabled user terminals. Based on the multicasting opportunities provided by the so-called Coded Caching technique, we investigate three delivery approaches. Our baseline scheme employs the coded caching technique on top of max-min fair multicasting. The second one consists of a joint design of Zero-Forcing (ZF) and coded caching, where the coded chunks are formed in the signal domain (complex field). The third scheme is similar to the second one with the difference that the coded chunks are formed in the data domain (finite field). We derive closed-form rate...
Physical-Layer schemes for wireless coded caching
, Article IEEE Transactions on Information Theory ; Volume 65, Issue 5 , 2019 , Pages 2792-2807 ; 00189448 (ISSN) ; Caire, G ; Hossein Khalaj, B ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2019
Abstract
We investigate the potentials of applying the coded caching paradigm in wireless networks. In order to do this, we investigate physical layer schemes for downlink transmission from a multiantenna transmitter to several cache-enabled users. As the baseline scheme, we consider employing coded caching on the top of max-min fair multicasting, which is shown to be far from optimal at high-SNR values. Our first proposed scheme, which is near-optimal in terms of DoF, is the natural extension of multiserver coded caching to Gaussian channels. As we demonstrate, its finite SNR performance is not satisfactory, and thus we propose a new scheme in which the linear combination of messages is implemented...
Caching gain in wireless networks with fading: A multi-user diversity perspective
, Article IEEE Wireless Communications and Networking Conference, WCNC ; 2014 , p. 930-935 ; Shah Mansouri, H ; Khalaj, B. H ; Sharif University of Technology
2014
Abstract
We consider the effect of caching in wireless networks where fading is the dominant channel effect. First, we propose a one-hop transmission strategy for cache-enabled wireless networks, which is based on exploiting multi-user diversity gain. Then, we derive a closed-form result for throughput scaling of the proposed scheme in large networks, which reveals the inherent trade-off between cache memory size and network throughput. Our results show that substantial throughput improvements are achievable in networks with sources equipped with large cache size. We also verify our analytical result through simulations
Achievable throughput of wireless networks with local traffic
, Article IEEE Wireless Communications and Networking Conference, WCNC ; 10 November , 2014 , Pages 3076-3081 ; ISSN: 15253511 ; ISBN: 9781479930838 ; Khalaj, B. H ; Shah-Mansouri, H ; Sharif University of Technology
2014
Abstract
Many applications in wireless networks impose locally distributed traffic on the network. We consider the effect of traffic localization on throughput of large wireless networks in the scaling sense. We show that by careful exploitation of traffic localization, one can enhance the throughput of various schemes in wireless networks. Also, the important case of Small World traffic distribution in wireless networks is addressed. In this type of traffic, in addition to the local traffic, a non-negligible amount of global traffic should be handled by the network. It is shown that a non-negligible amount of network-wide traffic can be tolerated by network without any performance degradation in the...
On the route discovery rate of flooding in large wireless networks
, Article IEEE International Symposium on Personal, Indoor and Mobile Radio Communications, PIMRC ; 2012 , Pages 1238-1242 ; 9781467325691 (ISBN) ; Khalaj, B. H ; Shariatpanahi, S. P ; Sharif University of Technology
2012
Abstract
In this paper, we derive the rate of route discovery process for finding a randomly chosen destination in large wireless networks. The well-known protocol for route discovery is flooding in which each node simply rebroadcasts the route request packet once. Rate of route discovery process is defined as the inverse of time between transmitting two successive route request packets which shows how fast a node can request a route to its destination. Discovery time is another parameter of interest. For a single node discovering routes to its destination, at most the rate of Eθ (1/3√n) is feasible when n identical nodes are optimally placed in network area and the discovery time is of order...
Power allocation scheme in time division multiple access distributed multiple-input multiple-output interference channels
, Article IET Communications ; Volume 7, Issue 5 , 2013 , Pages 391-396 ; 17518628 (ISSN) ; Khalaj, B. H ; Shah Mansouri, H ; Sharif University of Technology
2013
Abstract
In this study, the authors propose a novel power allocation scheme in time division multiple access (TDMA)-based distributed multiple-input multiple-output (MIMO) channels. By modelling the problem with a TDMA MIMO interference channel, the authors have derived closed-form expressions for power and time slot assigned to each MIMO transmission. Although our scheme is sub-optimal, with the aid of Jensen's inequality, it is shown to be superior to solutions based on channel inversion. In addition, the proposed scheme is compared with the optimal solution, and also with the scheme proposed by Dohler. By applying our proposed power allocation to the hierarchical cooperation strategy, the authors...