Sharif Digital Repository

Matsufuji and Imamura (see IEEE Trans. on Info. Theory, vol.46, no.4, p.1691-95, 2000) proposed a new method to generate an optimal set of bent sequences as a set of signature sequences for a CDMA system has been introduced. This method is designed to make the CDMA system secure against interception, for both an insider intruder (a user) and an outsider intruder. The security analysis of this system of Matsufuji et al. was based on computing the cardinality of the search space. In this paper after reforming the bent function decomposition, we reapply the above analysis to the system. Then for binary sequences, we consider another analysis to this system, which is based on the fact that all... 

This article analyzes various roles of development practitioners (called outsiders) in five different cases of community-based development (CBD) in rural Iran. It provides a review of the literature on CBD and identifies three main types of roles fulfilled by outsiders to support indigenous development processes. These include preparing the ground, activating community-based organizations as participatory institutions, and taking on the role of brokers who bridge the gap between the local community and outside institutions—especially the state and market. From the analysis of empirical qualitative data collected during fieldwork in Iran, the article concludes that while the roles played by... 

We study quantum information transmission in a Heisenberg-XY chain where qubits are affected by quasi-local environment action and compare it with the case of local action of the environment. We find that for open boundary conditions the former situation always improves quantum state transfer process, especially for short chains. In contrast, for closed boundary conditions quasi-local environment results advantageous in the strong noise regime. When the noise strength is comparable with the XY interaction strength, the state transfer fidelity through chain of odd/even number of qubits in presence of quasi-local environment results smaller/greater than that in presence of local environment. ©... 

The use of Spread-Time CDMA for ultrawideband (UWB) wireless communication is proposed and its capability for supporting many high data rate users is investigated. Furthermore we will study a hybrid technique, namely, Spread-Time/Time-Hopping to increase the capacity of the above mentioned technique and simultaneously minimizing the effect of near-far in a typical CDMA system  

[No abstract available]  

In this paper, we propose a new algorithm that minimizes the worst expected growth of an epidemic by reducing the size of the largest connected component (LCC) of the underlying contact network. The proposed algorithm is applicable to any level of available resources and, despite the greedy approaches of most immunization strategies, selects nodes simultaneously. In each iteration, the proposed method partitions the LCC into two groups. These are the best candidates for communities in that component, and the available resources are sufficient to separate them. Using Laplacian spectral partitioning, the proposed method performs community detection inference with a time complexity that rivals... 

A comparative world map of scientific misconduct reveals that countries with the most rapid growth in scientific publications also have the highest retraction rate. To avoid polluting the scientific record further, these nations must urgently commit to enforcing research integrity among their academic communities. © 2017 Springer Science+Business Media B.V  

The great surge in the research of community discovery in complex network is going on due to its challenging aspects. Dynamicity and overlapping nature are among the common characteristics of these networks which are the main focus of this paper. In this research, we attempt to approximate the granular human-inspired viewpoints of the networks. This is especially helpful when making decisions with partial knowledge. In line with the principle of granular computing, in which precision is avoided, we define the micro- and macrogranules in two levels of nodes and communities, respectively. The proposed algorithm takes microgranules as input and outputs meaningful communities in rough... 

A comparative world map of scientific misconduct reveals that countries with the most rapid growth in scientific publications also have the highest retraction rate. To avoid polluting the scientific record further, these nations must urgently commit to enforcing research integrity among their academic communities. © 2017, Springer Science+Business Media B.V  

Nowadays users of the Web are encouraged to generate content on the Web by themselves. Weblogs are the most popular tools to do this. In fact Weblogs are one kind of social networks and they are one of the most important components in Web 2.0. Blogs are often situated within a Blog community of similar interest. These communities can be a useful way for readers to access space slice of millions of Weblogs. In this paper we introduce a new algorithm to infer communities based on their link structure. This algorithm uses self organizing maps to identify communities among Weblogs. The link pattern of each Weblog is the input for SOM. © 2007 IADIS  

In this paper, we will introduce a new constraint on linear space-time block codes that will result in a novel decoupled symbol-by-symbol detection scheme. Based on the new framework, a quasi-decoupled space-time code that is applicable to any number of transmit and receive antennas will be proposed. We will also solve a more general case and show that all other known solutions to this problem such as orthogonal designs and Clifford algebra representations, represent special cases of such general solution which will provide an easier framework, to deal with such codes. It is noticeable that the new framework not only provides better understanding of earlier solutions but may also help in... 

The evolution of communication and its consequences on living objects is a challenging subject for many researches. Due to lack of our knowledge about the real trend of this evolution, artificial life simulations can shed light on many dark points of this process. In this paper, we have used Zamin artificial life environment to test the emergence of a very simple form of communication. The usability of this new capability is tested by a simple test of coping with new environment  

One of the most prominent features of code division multiple-access (CDMA) cellular networks is their ability for applying soft-handoff. This type of handoff results in a better supporting of seamless communication services, capacity enhancement, QoS improvement, etc. Because of existence of more parameters and flexibilities compared to hard-handoff, an optimum solution for soft-handoff management and admission control for new and handoff calls is necessary. In this paper we propose a new algorithm with two thresholds for admission of new and handoff calls, and with two decision boundaries for controlling of handoff traffic. We compare this algorithm with a simpler one with only one decision... 

In this paper we present and investigate a digital design and implementational details of a wireless optical CDMA (OCDMA) system based on generalized optical orthogonal codes (OOCs). A detailed digital implementation analysis and transmitter/receiver architectures in the context of the above design are fully studied. We analyze various subsystems for a wireless OCDMA system including detector and receiver structure, acquisition, and tracking blocks as well as evaluating their performance in a typical wireless OCDMA communication system. By analyzing two main parts of the system, namely, chip-level detector and OCDMA receiver blocks we evaluate the performance of the overall system.... 

An electric power supply is the backbone of development in advanced as well as in developing economies. An integral part of ensuring a secure power supply system is a power communication system. Due to the high and sustained performance requirements of power communication systems, electric companies prefer to construct their own communication networks privately rather than relying solely on a public communication system. The focus of this paper is on the optimal topological design of a power communication network. Based on advanced optimization models in public communication networks, and taking into account the specific Quality of Service, as demanded by various applications, such as... 

With the proliferation of cloud computing concept, the datacenters, as the basic infrastructure for cloud computing, have gained an ever-growing attention during the last decade. Energy consumption in datacenters is one of the several features of them that have been the target of various researches. Two major consumers of energy in datacenters are the cooling system and IT equipment. Computing resources, such as servers, and communicating ones, such as switches, constitute the main portion of IT equipment. Among these two major players, the servers have been considered more than networking equipment. Making servers energy proportional as well as server consolidation are the two essential... 

The ability to perform multicast communication efficiently in parallel computing systems is increasingly becoming an essential feature of these systems. Therefore, any emerging parallel architecture must be able to provide effective multicasting performance. OTIS-based multi-computer systems are parallel systems that efficiently exploit optical connections between distant nodes, while using electronic connections for physically close processors. No previous work has attempted to determine an optimal multicast communication scheme for OTIS networks. This paper presents two approaches to implement efficient multicast communication in wormhole-routed OTIS networks, for the two different... 

In recent years, flash memory solid state disks (SSDs) have shown a great potential to change storage infrastructure because of its advantages of high speed and high throughput random access. This promising storage, however, greatly suffers from performance loss because of frequent ''erase-before-write'' and ''garbage collection'' operations. Thus, novel circuit-level, architectural, and algorithmic techniques are currently explored to address these limitations. In parallel with others, current study investigates replacing shared buses in multi-channel architecture of SSDs with an interconnection network to achieve scalable, high throughput, and reliable SSD storage systems. Roughly... 

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... 

We investigate the problem of reliable communication in the presence of active adversaries that can tamper with the transmitted data. We consider a legitimate transmitter-receiver pair connected over multiple communication paths (routes). We propose two new models of adversary, a 'memoryless' and a 'foreseer' adversary. For both models, the adversaries are placing themselves arbitrarily on the routes, keeping their placement fixed throughout the transmission block. This placement may or may not be known to the transmitter. The adversaries can choose their best modification strategy to increase the error at the legitimate receiver, subject to a maximum distortion constraint. We investigate...