University of Brasilia

Displaying 1-40 of 61 results

  • White Papers // Jan 2014

    A Role Based Access Control Model for Agent Based Control Systems

    The spreading of Ethernet TCP/IP protocol suite based communication in automation systems has raised new questions concerning data consistency and security. This paper introduces temporal-logic RBAC as a method to formalize the security relevant access constraints for an agent based control system. It also offers some examples of such formalized...

    Provided By University of Brasilia

  • White Papers // Jan 2014

    Change Detection in Hierarchically Structured Information

    Detecting and representing changes to data is important for active databases, data warehousing, view maintenance, and version and configuration management. Most previous paper in change management has dealt with flat-file and relational data; the authors focus on hierarchically structured data. Since in many cases changes must be computed from old...

    Provided By University of Brasilia

  • White Papers // Oct 2013

    UML/OCL Based Design and Analysis of Role-Based Access Control Policies

    Access control plays an important part in IT systems these days. Specifically Role-Based Access Control (RBAC) has been widely adopted in practice. One of the major challenges within the introduction of RBAC into an organization is the policy definition. Modeling technologies provide support by allowing to design and to validate...

    Provided By University of Brasilia

  • White Papers // Jul 2013

    Ontology-Based Data Access with Closed Predicates is Inherently Intractable

    When answering queries in the presence of ontologies, adopting the closed world assumption for some predicates easily results in intractability. The authors analyze this situation on the level of individual ontologies formulated in the description logics DL-Lite and EL and show that in all cases where answering Conjunctive Queries (CQs)...

    Provided By University of Brasilia

  • White Papers // Jun 2013

    Ontology-Based Data Access: A Study Through Disjunctive Datalog, CSP, and MMSNP

    Ontology-based data access is concerned with querying incomplete data sources in the presence of domain-specific knowledge provided by an ontology. A central notion in this setting is that of an ontology-mediated query, which is a database query coupled with an ontology. In this paper, the authors study several classes of...

    Provided By University of Brasilia

  • White Papers // Jun 2013

    The Transitivity-of-Trust Problem in Android Application Interaction

    Mobile phones have developed into complex platforms with large numbers of installed applications and a wide range of sensitive data. Application security policies limit the permissions of each installed application. As applications may interact, restricting single applications may create a false sense of security for end users, while data may...

    Provided By University of Brasilia

  • White Papers // Jun 2013

    Ontology-Based Access to Probabilistic Data

    In recent years, Ontology Based Data Access (OBDA) has become an active area of description logic research. In OBDA, an ontology provides a semantics for incomplete data with the aim of facilitating the computation of more complete answers to queries. The authors propose a framework for querying probabilistic data in...

    Provided By University of Brasilia

  • White Papers // Jun 2013

    Coping With CDMA Asynchronicity in Compressive Sensing Multi-User Detection

    The growing field of Machine-to-Machine communication requires new physical layer concepts to meet future requirements. In previous works it has been shown for a synchronous CDMA transmission that Compressive Sensing (CS) detectors are capable of jointly detecting both activity and data in Multi-User Detection (MUD). However, many practical applications show...

    Provided By University of Brasilia

  • White Papers // May 2013

    Conjunctive Queries with Negation over DL-Lite: A Closer Look

    While Conjunctive Query (CQ) answering over DL-Lite has been studied extensively, there have been few attempts to analyze CQs with negated atoms. This paper deepens the study of the problem. Answering CQs with safe negation and CQs with a single inequality over DL-Lite with role inclusions is shown to be...

    Provided By University of Brasilia

  • White Papers // May 2013

    Performance of HARQ With Reduced Size Retransmissions Using Network Coding Principles

    This paper discusses retransmission approaches to improve the throughput performance of Hybrid-ARQ (HARQ) schemes in a point-to-point single user 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE) uplink system. One goal of communication systems is to achieve a reliable transmission with a throughput performance as close as possible to...

    Provided By University of Brasilia

  • White Papers // May 2013

    Joint Activity and Data Detection for Machine to Machine Communication Via Bayes Risk Optimization

    Performing joint detection of activity and data is a promising approach to reduce management overhead in Machine-to-Machine communication. However, erroneous activity detection has severe impacts on the system performance. Estimating an active node or user erroneously to be inactive results in a loss of data. To optimally balance activity and...

    Provided By University of Brasilia

  • White Papers // Apr 2013

    First-Order Rewritability of Atomic Queries in Horn Description Logics

    One of the most advanced approaches to querying data in the presence of ontologies is to make use of relational database systems, rewriting the original query and the ontology into a new query that is formulated in SQL or, equivalently, in First-Order logic (FO). For ontologies written in many standard...

    Provided By University of Brasilia

  • White Papers // Feb 2013

    Compressed Sensing Bayes Risk Minimization for Under-Determined Systems Via Sphere Detection

    The application of Compresses Sensing is a promising physical layer technology for the joint activity and data detection of signals. Detecting the activity pattern correctly has severe impact on the system performance and is therefore of major concern. In contrast to previous work, in this paper the authors optimize joint...

    Provided By University of Brasilia

  • White Papers // Feb 2013

    Complexity Reduction Strategy for RAID in Multi-User Relay Systems

    In this paper, distributed Interleave-Division-Multiplexing Space Time Codes (dIDM-STC) in Multi-User Decode-and-Forward Relay Systems are considered. Due to decoding errors at the relays, which are unavoidable in practical systems, error propagation to the destination occurs. In order to cope with this error propagation, recently a Reliability-Aware Iterative Detection Scheme (RAID)...

    Provided By University of Brasilia

  • White Papers // Feb 2013

    Physical-Layer Network Coding in Coded OFDM Systems With Multiple-Antenna Relay

    In this paper Physical Layer Network Coding (PLNC) in two-phase two-way relaying networks using coded Orthogonal Frequency Division Multiplexing (OFDM) transmission is investigated. After receiving the superimposed signal from both sources, the relay estimates the XOR-based network coded signal, which is broadcast back to the sources. Assuming that the relay...

    Provided By University of Brasilia

  • White Papers // Feb 2013

    Sparsity-Aware Successive Interference Cancellation With Practical Constraints

    This paper investigates new detection methods for low data-rate Machine Type Communication. Special attention is paid to uplink communication in networks where nodes are only active occasionally, which requires a joint activity and data detection at the receiver. This paper shows that a modified version of Successive Interference Cancellation is...

    Provided By University of Brasilia

  • White Papers // Dec 2012

    Extracting and Analyzing the Implemented Security Architecture of Business Applications

    Security is getting more and more important for the software development process as the advent of more complex, connected and extensible software entails new risks. In particular, multi-tier business applications, e.g., based on the Service-Oriented Architecture (SOA), are vulnerable to new attacks, which may endanger the business processes of an...

    Provided By University of Brasilia

  • White Papers // Dec 2012

    Deciding FO-Rewritability in EL

    Over the last years, query answering over instance data has developed into one of the most prominent problems in Description Logic (DL) research. Many approaches aim at utilizing Relational DataBase Management Systems (RDBMSs), exploiting their mature technology, advanced optimization techniques, and the general infrastructure that those systems offer. Roughly, RDBMS-based...

    Provided By University of Brasilia

  • White Papers // Nov 2012

    Performance Comparison of Scheduling Algorithms for Multipath Transfer

    Multipath transport protocols such as Multipath TCP can concurrently use several sub-flows to transmit a TCP flow over potentially different paths. Since more than one sub-flow is used, an efficient multipath scheduling algorithm is needed at the sender. The objective of the scheduler is to identify the sub-flow over which...

    Provided By University of Brasilia

  • White Papers // Nov 2012

    Mutual Information Based Analysis for Physical-Layer Network Coding With Optimal Phase Control

    In this paper two-way relaying networks are considered using physical-layer network coding in a two-phase protocol. In the multiple access phase, both sources transmit their messages to the relay simultaneously. Subsequently, the relay estimates and broadcasts the XOR-based network coded message back to the sources in the broadcast phase. The...

    Provided By University of Brasilia

  • White Papers // Oct 2012

    Secure Mobile Business Information Processing

    An ever increasing amount of functionality is incorporated into mobile phones - this trend will continue as new mobile phone platforms are more widely used such as the iPhone or Android. Along with this trend, however, new risks arise, especially for enterprises using mobile phones for security-critical applications such as...

    Provided By University of Brasilia

  • White Papers // Sep 2012

    Sparsity Aware Multiuser Detection for Machine to Machine Communication

    With the expected growth of Machine-To-Machine (M2M) communication, new requirements for future communication systems have to be considered. Traffic patterns in M2M communication fundamentally differ from human based communication. Especially packets in M2M are rather small and transmitted sporadically only. Moreover, nodes for M2M communication are often of reduced functionality...

    Provided By University of Brasilia

  • White Papers // Sep 2012

    An Update on Query Answering with Restricted Forms of Negation

    One of the most prominent applications of description logic ontologies is their use for accessing data. In this setting, ontologies provide an abstract conceptual layer of the data schema, and queries over the ontology are then used to access the data. In this paper, the authors focus on extensions of...

    Provided By University of Brasilia

  • White Papers // Sep 2012

    The Combined Approach to OBDA: Taming Role Hierarchies Using Filters

    There are several approaches to implementing query answering over instance data in the presence of an ontology that target conventional relational database systems (SQL databases) as their back-end. They all share the limitation that, for ontologies formulated in OWL2 QL or versions of the description logic DL-Lite that admit both...

    Provided By University of Brasilia

  • White Papers // Aug 2012

    Ontology-Based Access to Probabilistic Data with OWL QL

    There are many applications that require data to be first extracted from the web and then further processed locally, by feeding it into a Relational DataBase Management System (RDBMS). The authors propose a framework for querying probabilistic instance data in the presence of an OWL2 QL ontology, arguing that the...

    Provided By University of Brasilia

  • White Papers // Jul 2012

    Future Mobile Communications, LTE Optimization and Mobile Network Virtualization

    In this paper, the authors present the concepts of network virtualization, focusing specifically on wireless virtualization of the LTE mobile communication system. A novel wireless virtualization framework is proposed and developed, which allows mobile network operators to share the wireless spectrum, as well as, the infrastructure (i.e., hardwares equipment). The...

    Provided By University of Brasilia

  • White Papers // Jul 2012

    Towards a Unifying Approach to Representing and Querying Temporal Data in Description Logics

    Establishing a generic approach to representing and querying temporal data in the context of Description Logics (DLs) is an important and still open challenge. The difficulty lies in that a proposed approach should reconcile a number of valuable contributions coming from diverse, yet relevant research lines, such as temporal databases...

    Provided By University of Brasilia

  • White Papers // Jun 2012

    An Improved Detection Scheme for Distributed IDM-STCs in Relay-Systems

    This paper is concerned with the application of distributed Interleave-Division-Multiplexing Space-Time Codes (dIDM-STCs) in relaying systems with error-prone relays applying Decode-and-Forward (DF). In case of erroneous decoding at the relays, error propagation occurs this is not considered by the original detection scheme for IDM-STCs. Hence, a new Reliability Aware Iterative...

    Provided By University of Brasilia

  • White Papers // May 2012

    Mixing Open and Closed World Assumption in Ontology-Based Data Access: Non-Uniform Data Complexity

    When using ontologies to access instance data, it can be useful to make a Closed World Assumption (CWA) for some predicates and an Open World Assumption (OWA) for others. The main problem with such a setup is that Conjunctive Query (CQ) answering becomes intractable already for inexpressive description logics such...

    Provided By University of Brasilia

  • White Papers // Mar 2012

    Query Containment in Description Logics Reconsidered

    While query answering in the presence of Description Logic (DL) ontologies is a well-studied problem, questions of static analysis such as query containment and query optimization have received less attention. In this paper, the authors study a rather general version of query containment that, unlike the classical version, cannot be...

    Provided By University of Brasilia

  • White Papers // Mar 2012

    An Approach to Detecting Inter-Session Data Flow Induced by Object Pooling

    Security tools, using static code analysis, are employed to find common bug classes, such as SQL injections and cross-site scripting vulnerabilities. This paper focuses on another bug class that is related to the object-pool pattern, which allows objects to be reused over multiple sessions. The authors show that the pattern...

    Provided By University of Brasilia

  • White Papers // Aug 2011

    An Android Security Case Study with Bauhaus

    Software security has made great progress; code analysis tools are widely-used in industry for detecting common implementation-level security bugs. However, given the fact that the authors must deal with legacy code they plead to employ the techniques long been developed in the research area of program comprehension for software security....

    Provided By University of Brasilia

  • White Papers // Aug 2011

    Employing UML and OCL for Designing and Analyzing Role-Based Access Control

    Stringent security requirements of organizations like banks or hospitals frequently adopt Role-Based Access Control (RBAC) principles to represent and simplify their internal permission management. While representing a fundamental advanced RBAC concept enabling precise restrictions on access rights, authorization constraints increase the complexity of the resulting security policies so that tool...

    Provided By University of Brasilia

  • White Papers // Aug 2011

    LTE Virtualization: from Theoretical Gain to Practical Solution

    Virtualization of wireless networks has received more and more research attention. As a means to reduce the investment of mobile network operators and to improve the network performance, LTE (Long Term Evolution) virtualization is one important study cases in the scope of wireless virtualization. To investigate the advantages of virtualization...

    Provided By University of Brasilia

  • White Papers // Aug 2011

    Review of Trust-Based File Sharing in Cloud Computing

    The recent advances in cloud computing have risen a number of unforeseen security related issues in different aspects of cloud environments. Among these, the problem of guaranteeing secure access to computing resources in the cloud is gathering special attention. In this paper, the authors address open issues related to trust...

    Provided By University of Brasilia

  • White Papers // Apr 2011

    The Combined Approach to Ontology-Based Data Access

    The use of ontologies for accessing data is one of the most exciting new applications of description logics in databases and other information systems. A realistic way of realizing sufficiently scalable ontology-based data access in practice is by reduction to querying relational databases. In this paper, the authors describe the...

    Provided By University of Brasilia

  • White Papers // Mar 2011

    Comprehensive Two-Level Analysis of Static and Dynamic RBAC Constraints with UML and OCL

    Organizations with stringent security requirements like banks or hospitals frequently adopt Role-Based Access Control (RBAC) principles to simplify their internal permission management. Authorization constraints represent a fundamental advanced RBAC concept enabling precise restrictions on access rights. Thereby, the complexity of the resulting security policies increases so that tool support for...

    Provided By University of Brasilia

  • White Papers // Feb 2011

    A Formal Classification of Internet Banking Attacks and Vulnerabilities

    Currently there is a clear need for efficient security models by banks which offer online access to their banking systems. In face of the growing number of transactions processed through online banking systems, several new security technologies and models which aim at providing authenticated secure communications through known insecure channels...

    Provided By University of Brasilia

  • White Papers // Dec 2010

    A Context-Dependent Trust Model for the MAC Layer in LR-WPANs

    Low rate wireless personal networks are vulnerable to several attacks focused on the Media Access Layer. Malicious or faulty nodes can subvert CSMA/CA and GTS allocation algorithms, achieving MAC unfairness in order to obtain higher medium access priority or to interrupt legitimate communication, ultimately leading to Denial-of-Service. While there exist...

    Provided By University of Brasilia

  • White Papers // Dec 2010

    An Architecture-Centric Approach to Detecting Security Patterns in Software

    Today, software security is an issue with increasing importance. Developers, software designers, end users, and enterprises have their own needs w.r.t. software security. Therefore, when designing software, security should be built in from the beginning, for example, by using security patterns. Utilizing security patterns already improves the security of software...

    Provided By University of Brasilia

  • White Papers // Jul 2012

    Future Mobile Communications, LTE Optimization and Mobile Network Virtualization

    In this paper, the authors present the concepts of network virtualization, focusing specifically on wireless virtualization of the LTE mobile communication system. A novel wireless virtualization framework is proposed and developed, which allows mobile network operators to share the wireless spectrum, as well as, the infrastructure (i.e., hardwares equipment). The...

    Provided By University of Brasilia

  • White Papers // Feb 2010

    Semantic Cloud: An Enhanced Browsing Interface for Exploring Resources in Folksonomy Systems

    Popular web folksonomy systems such as Delicious or Flickr allow users to create web contents and annotate them with a set of freely chosen keywords (tags) in order to organize them for later retrieval. Unfortunately, existing user interfaces of folksonomy systems have limited browsing capabilities and do not exploit tag...

    Provided By University of Brasilia

  • White Papers // Dec 2012

    Extracting and Analyzing the Implemented Security Architecture of Business Applications

    Security is getting more and more important for the software development process as the advent of more complex, connected and extensible software entails new risks. In particular, multi-tier business applications, e.g., based on the Service-Oriented Architecture (SOA), are vulnerable to new attacks, which may endanger the business processes of an...

    Provided By University of Brasilia

  • White Papers // May 2007

    Security Challenges for RFID Key Applications

    RFID technology is an emerging market with a wide spectrum of application domains. The introduction of RFID systems in industrial manufacturing has already been taken up more than ten years ago. Currently RFID tags are appearing in public environments like ticketing applications and retail supply chains. One the one hand...

    Provided By University of Brasilia

  • White Papers // Aug 2011

    An Android Security Case Study with Bauhaus

    Software security has made great progress; code analysis tools are widely-used in industry for detecting common implementation-level security bugs. However, given the fact that the authors must deal with legacy code they plead to employ the techniques long been developed in the research area of program comprehension for software security....

    Provided By University of Brasilia

  • White Papers // Dec 2009

    Idea: Towards Architecture-Centric Security Analysis of Software

    Static security analysis of software has made great progress over the last years. In particular, this applies to the detection of low-level security bugs such as buffer overflows, Cross-Site Scripting (XSS) and SQL injection vulnerabilities. Complementarily to commercial static code review tools, the authors present an approach to the static...

    Provided By University of Brasilia

  • White Papers // Oct 2012

    Secure Mobile Business Information Processing

    An ever increasing amount of functionality is incorporated into mobile phones - this trend will continue as new mobile phone platforms are more widely used such as the iPhone or Android. Along with this trend, however, new risks arise, especially for enterprises using mobile phones for security-critical applications such as...

    Provided By University of Brasilia

  • White Papers // Dec 2010

    An Architecture-Centric Approach to Detecting Security Patterns in Software

    Today, software security is an issue with increasing importance. Developers, software designers, end users, and enterprises have their own needs w.r.t. software security. Therefore, when designing software, security should be built in from the beginning, for example, by using security patterns. Utilizing security patterns already improves the security of software...

    Provided By University of Brasilia

  • White Papers // Sep 2008

    Enforcing Role-Based Access Control Policies in Web Services with UML and OCL

    Role-Based Access Control (RBAC) is a powerful means for laying out and developing higher-level organizational policies such as separation of duty, and for simplifying the security management process. One of the important aspects of RBAC is authorization constraints that express such organizational policies. While RBAC has generated a great interest...

    Provided By University of Brasilia

  • White Papers // Aug 2007

    Analyzing and Managing Role-Based Access Control Policies

    Today more and more security-relevant data is stored on computer systems; security-critical business processes are mapped to their digital counterparts. This situation applies to various domains such as health care industry, digital government, and financial service institutes requiring that different security requirements must be fulfilled. Authorization constraints can help the...

    Provided By University of Brasilia

  • White Papers // Nov 2008

    Implementing Advanced RBAC Administration Functionality with USE

    Role-Based Access Control (RBAC) is a powerful means for laying out and developing higher-level organizational policies such as separation of duty, and for simplifying the security management process. One of the important aspects of RBAC is authorization constraints that express such organizational policies. While, RBAC has generated a great interest...

    Provided By University of Brasilia

  • White Papers // Jan 2014

    A Role Based Access Control Model for Agent Based Control Systems

    The spreading of Ethernet TCP/IP protocol suite based communication in automation systems has raised new questions concerning data consistency and security. This paper introduces temporal-logic RBAC as a method to formalize the security relevant access constraints for an agent based control system. It also offers some examples of such formalized...

    Provided By University of Brasilia

  • White Papers // Mar 2012

    An Approach to Detecting Inter-Session Data Flow Induced by Object Pooling

    Security tools, using static code analysis, are employed to find common bug classes, such as SQL injections and cross-site scripting vulnerabilities. This paper focuses on another bug class that is related to the object-pool pattern, which allows objects to be reused over multiple sessions. The authors show that the pattern...

    Provided By University of Brasilia

  • White Papers // Sep 2008

    Supporting Agile Development of Authorization Rules for SME Applications

    Custom SME applications for collaboration and work flow have become affordable when implemented as web applications employing Agile methodologies. Security engineering is still difficult with Agile development, though: heavy-weight processes put the improvements of Agile development at risk. The authors propose Agile security engineering and increased end-user involvement to improve...

    Provided By University of Brasilia

  • White Papers // Oct 2013

    UML/OCL Based Design and Analysis of Role-Based Access Control Policies

    Access control plays an important part in IT systems these days. Specifically Role-Based Access Control (RBAC) has been widely adopted in practice. One of the major challenges within the introduction of RBAC into an organization is the policy definition. Modeling technologies provide support by allowing to design and to validate...

    Provided By University of Brasilia

  • White Papers // May 2010

    Towards Formal Specification and Verification of a Role-Based Authorization Engine Using JML

    Employing flexible access control mechanisms, formally specifying and correctly implementing relevant security properties, and ensuring that the implementation satisfies its formal specification, are some of the important aspects towards achieving higher-level organization-wide access control that maintains the characteristics of software quality. In the access control arena, the Role-Based Access Control...

    Provided By University of Brasilia

  • White Papers // Jun 2013

    The Transitivity-of-Trust Problem in Android Application Interaction

    Mobile phones have developed into complex platforms with large numbers of installed applications and a wide range of sensitive data. Application security policies limit the permissions of each installed application. As applications may interact, restricting single applications may create a false sense of security for end users, while data may...

    Provided By University of Brasilia

  • White Papers // Apr 2008

    Using Library Dependencies for Clustering

    Software clustering is an established approach to automatic architecture recovery. It groups components that are in some way similar to each other. Usually, the similarity measure is based on the dependencies between components of a system. Library dependencies are intentionally ignored during the clustering process - otherwise, system components would...

    Provided By University of Brasilia

  • White Papers // Mar 2011

    Comprehensive Two-Level Analysis of Static and Dynamic RBAC Constraints with UML and OCL

    Organizations with stringent security requirements like banks or hospitals frequently adopt Role-Based Access Control (RBAC) principles to simplify their internal permission management. Authorization constraints represent a fundamental advanced RBAC concept enabling precise restrictions on access rights. Thereby, the complexity of the resulting security policies increases so that tool support for...

    Provided By University of Brasilia

  • White Papers // Aug 2011

    Employing UML and OCL for Designing and Analyzing Role-Based Access Control

    Stringent security requirements of organizations like banks or hospitals frequently adopt Role-Based Access Control (RBAC) principles to represent and simplify their internal permission management. While representing a fundamental advanced RBAC concept enabling precise restrictions on access rights, authorization constraints increase the complexity of the resulting security policies so that tool...

    Provided By University of Brasilia

  • White Papers // Nov 2010

    The Economics Of Demand Led-Growth Theory And Evidence For Brazil

    The objective of the present paper is to present the theory of demand-led growth and some econometric evidence of the existence of a demand-led growth regime for the Brazilian economy. Initially, the authors will do a brief review of the theory of demand-led growth, based on Kaldor's (1988) contribution for...

    Provided By University of Brasilia

  • White Papers // Nov 2010

    An Appraisal Of The Import Substitution Strategy From A Structural Economic Dynamic Approach

    This paper seeks to establish that a Structural Economic Dynamic (SED) approach toward understanding technological gaps offers a superior method relative to the Import Substitution Strategy (ISS). It is argued that the ISS approach fails to account for the role of demand and hence, the structural dynamics of underdeveloped economies,...

    Provided By University of Brasilia

  • White Papers // Nov 2010

    A Bayesian Trust Model for the MAC Layer in IEEE 802.15.4 Networks

    While the IEEE 802.15.4 standard provides internal security mechanisms, it is still possible that a malicious or faulty node abuses CSMA/CA and GTS allocation to gain continuous access to media or to prevent other nodes from transmitting, resulting in MAC unfairness. In this paper, the authors present a practical attack...

    Provided By University of Brasilia

  • White Papers // Sep 2010

    Improving Video Quality for Handover Between Legacy MIPv4 Overlay Networks

    In this paper, the authors introduce a novel Specialized MIP implementation (S-MIP) to reduce native MIP latency into a scenario in which Wireless Local Network (WLAN) and 3G networks are integrated through user multimode terminal. This solution attempts to preserve the quality of the streaming video during each handover and...

    Provided By University of Brasilia

  • White Papers // Dec 2010

    A Context-Dependent Trust Model for the MAC Layer in LR-WPANs

    Low rate wireless personal networks are vulnerable to several attacks focused on the Media Access Layer. Malicious or faulty nodes can subvert CSMA/CA and GTS allocation algorithms, achieving MAC unfairness in order to obtain higher medium access priority or to interrupt legitimate communication, ultimately leading to Denial-of-Service. While there exist...

    Provided By University of Brasilia

  • White Papers // Dec 2009

    Optimal Investment Specific Technological Progress Allocation In A Two Sector Model

    In this paper the impact of investment specific technical progress on investment allocation is studied by using an extended version of the Feldman's two sector model that takes into account embodied technical progress. The aim of the paper is to analyze the impact of investment specific technical progress on the...

    Provided By University of Brasilia

  • White Papers // Aug 2011

    Review of Trust-Based File Sharing in Cloud Computing

    The recent advances in cloud computing have risen a number of unforeseen security related issues in different aspects of cloud environments. Among these, the problem of guaranteeing secure access to computing resources in the cloud is gathering special attention. In this paper, the authors address open issues related to trust...

    Provided By University of Brasilia

  • White Papers // Dec 2009

    Seamless Video Session Handoff Between WLANs

    Handoff in a distributed IEEE 802.11 Wireless LAN network is a source of significant amount of problems on the video transmission environment. The visual quality of video streaming applications is lowered when stations are in handoff status. In this paper, the authors introduce an architecture of a Session Proxy (SP),...

    Provided By University of Brasilia

  • White Papers // Feb 2013

    Physical-Layer Network Coding in Coded OFDM Systems With Multiple-Antenna Relay

    In this paper Physical Layer Network Coding (PLNC) in two-phase two-way relaying networks using coded Orthogonal Frequency Division Multiplexing (OFDM) transmission is investigated. After receiving the superimposed signal from both sources, the relay estimates the XOR-based network coded signal, which is broadcast back to the sources. Assuming that the relay...

    Provided By University of Brasilia

  • White Papers // Feb 2013

    Complexity Reduction Strategy for RAID in Multi-User Relay Systems

    In this paper, distributed Interleave-Division-Multiplexing Space Time Codes (dIDM-STC) in Multi-User Decode-and-Forward Relay Systems are considered. Due to decoding errors at the relays, which are unavoidable in practical systems, error propagation to the destination occurs. In order to cope with this error propagation, recently a Reliability-Aware Iterative Detection Scheme (RAID)...

    Provided By University of Brasilia

  • White Papers // Jun 2013

    Coping With CDMA Asynchronicity in Compressive Sensing Multi-User Detection

    The growing field of Machine-to-Machine communication requires new physical layer concepts to meet future requirements. In previous works it has been shown for a synchronous CDMA transmission that Compressive Sensing (CS) detectors are capable of jointly detecting both activity and data in Multi-User Detection (MUD). However, many practical applications show...

    Provided By University of Brasilia

  • White Papers // Feb 2013

    Compressed Sensing Bayes Risk Minimization for Under-Determined Systems Via Sphere Detection

    The application of Compresses Sensing is a promising physical layer technology for the joint activity and data detection of signals. Detecting the activity pattern correctly has severe impact on the system performance and is therefore of major concern. In contrast to previous work, in this paper the authors optimize joint...

    Provided By University of Brasilia

  • White Papers // May 2013

    Performance of HARQ With Reduced Size Retransmissions Using Network Coding Principles

    This paper discusses retransmission approaches to improve the throughput performance of Hybrid-ARQ (HARQ) schemes in a point-to-point single user 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE) uplink system. One goal of communication systems is to achieve a reliable transmission with a throughput performance as close as possible to...

    Provided By University of Brasilia

  • White Papers // Nov 2012

    Mutual Information Based Analysis for Physical-Layer Network Coding With Optimal Phase Control

    In this paper two-way relaying networks are considered using physical-layer network coding in a two-phase protocol. In the multiple access phase, both sources transmit their messages to the relay simultaneously. Subsequently, the relay estimates and broadcasts the XOR-based network coded message back to the sources in the broadcast phase. The...

    Provided By University of Brasilia

  • White Papers // Sep 2012

    Sparsity Aware Multiuser Detection for Machine to Machine Communication

    With the expected growth of Machine-To-Machine (M2M) communication, new requirements for future communication systems have to be considered. Traffic patterns in M2M communication fundamentally differ from human based communication. Especially packets in M2M are rather small and transmitted sporadically only. Moreover, nodes for M2M communication are often of reduced functionality...

    Provided By University of Brasilia

  • White Papers // Feb 2013

    Sparsity-Aware Successive Interference Cancellation With Practical Constraints

    This paper investigates new detection methods for low data-rate Machine Type Communication. Special attention is paid to uplink communication in networks where nodes are only active occasionally, which requires a joint activity and data detection at the receiver. This paper shows that a modified version of Successive Interference Cancellation is...

    Provided By University of Brasilia

  • White Papers // Aug 2011

    LTE Virtualization: from Theoretical Gain to Practical Solution

    Virtualization of wireless networks has received more and more research attention. As a means to reduce the investment of mobile network operators and to improve the network performance, LTE (Long Term Evolution) virtualization is one important study cases in the scope of wireless virtualization. To investigate the advantages of virtualization...

    Provided By University of Brasilia

  • White Papers // Jul 2010

    LTE Wireless Virtualization and Spectrum Management

    Many research initiatives have started looking into Future Internet solutions in order to satisfy the ever increasing requirements on the Internet and also to cope with the challenges existing in the current one. Some are proposing further enhancements while others are proposing completely new approaches. Network Virtualization is one solution...

    Provided By University of Brasilia

  • White Papers // Jul 2013

    Ontology-Based Data Access with Closed Predicates is Inherently Intractable

    When answering queries in the presence of ontologies, adopting the closed world assumption for some predicates easily results in intractability. The authors analyze this situation on the level of individual ontologies formulated in the description logics DL-Lite and EL and show that in all cases where answering Conjunctive Queries (CQs)...

    Provided By University of Brasilia

  • White Papers // May 2012

    Mixing Open and Closed World Assumption in Ontology-Based Data Access: Non-Uniform Data Complexity

    When using ontologies to access instance data, it can be useful to make a Closed World Assumption (CWA) for some predicates and an Open World Assumption (OWA) for others. The main problem with such a setup is that Conjunctive Query (CQ) answering becomes intractable already for inexpressive description logics such...

    Provided By University of Brasilia