King Fahd University of Petroleum & Minerals

Displaying 1-32 of 32 results

  • White Papers // Jul 2012

    Low Complexity Blind Equalization for OFDM Systems with General Constellations

    This paper proposes a low-complexity algorithm for blind equalization of data in OFDM-based wireless systems with general constellation. The proposed algorithm is able to recover data even when the channel changes on a symbol-by-symbol basis, making it suitable for fast fading channels. The proposed algorithm does not require any statistical...

    Provided By King Fahd University of Petroleum & Minerals

  • White Papers // Jan 2012

    A Secure, Publisher-Centric Web Caching Infrastructure

    The current Web cache infrastructure, though it has a number of performance benefits, does not address many of the publishers' requirements. The authors argue that web caches should be enhanced to address publishers' needs. For example, caches will need to log client accesses, run scripts to dynamically produce content, and...

    Provided By King Fahd University of Petroleum & Minerals

  • White Papers // Jul 2011

    A Robust LMS Adaptive Algorithm Over Distributed Networks

    This paper explains the effect of erroneous noise power estimates on the behavior of noise constrained diffusion based adaptive algorithm for distributed adaptive networks. The Noise Constrained Diffusion Least Mean Square (NCDLMS) algorithm assumes knowledge of the noise variance is available at each node for good performance. Here, it is...

    Provided By King Fahd University of Petroleum & Minerals

  • White Papers // Mar 2011

    A Numerical Comparison Between LSSTC and VBLAST in Wireless Systems

    In this paper, the authors evaluate a recently proposed Multiple-Input Multiple-Output (MIMO) system called the Layered Steered Space-Time Codes (LSSTC) that combines the benefits of Vertical Bell Labs Space-Time (VBLAST) scheme, Space-Time Block Codes (STBC) and beamforming. This evaluation is done by comparing the capacity and the error rate of...

    Provided By King Fahd University of Petroleum & Minerals

  • White Papers // Jan 2011

    Engineering Evolutionary Algorithm to Solve Multi-Objective OSPF Weight Setting Problem

    Setting weights for Open Shortest Path First (OSPF) routing protocol is an NP-hard problem. Optimizing these weights leads to less congestion in the network while utilizing link capacities efficiently. In this paper, Simulated Evolution (SimE), a non-deterministic iterative heuristic, is engineered to solve this problem. A cost function that depends...

    Provided By King Fahd University of Petroleum & Minerals

  • White Papers // Jan 2011

    Fuzzy Aggregating Functions for Multiobjective VLSI Placement

    When fuzzy logic is used with multiobjective optimization, min/max operators may not be desirable. This is primarily due to lack of compensation/submission of min/max. To over-come this, Ordered Weighted Averaging (OWA) operators were proposed by Yager. OWA requires the selection of a control parameter ?, which is different for different...

    Provided By King Fahd University of Petroleum & Minerals

  • White Papers // Jan 2011

    Simulation-Based Comparative Study of on Demand Routing Protocols for MANET

    If the cable replacement feature of WLANs (Wireless LAN) is the core factor of its popularity, so is the non-existence of any prior infrastructure for MANET (Mobile Ad-hoc NETwork). The wireless links in an Ad-hoc network are highly error prone and can go down frequently because of node mobility, interference,...

    Provided By King Fahd University of Petroleum & Minerals

  • White Papers // Jan 2011

    On the Possibility of Consensus in Asynchronous Systems

    The authors demonstrate that the leader election and consensus problems are solvable in a timed asynchronous distributed system provided a majority of processes are always eventually able to communicate in a timely manner for a sufficiently long time. Failures and recoveries affecting the other processes and the communications between them...

    Provided By King Fahd University of Petroleum & Minerals

  • White Papers // Jan 2011

    OSPF Weight Setting Optimization for Single Link Failures

    In operational networks, nodes are connected via multiple links for load sharing and redundancy. This is done to make sure that a failure of a link does not disconnect or isolate some parts of the network. However, link failures have an effect on routing, as the routers find alternate paths...

    Provided By King Fahd University of Petroleum & Minerals

  • White Papers // Dec 2010

    A New Formula for the BER of Binary Modulations With Dual-Branch Selection Over Generalized-K Composite Fading Channels

    Error performance is one of the main performance measures and derivation of its closed-form expression has proved to be quite involved for certain systems. In this paper, a unified closed-form expression, applicable to different binary modulation schemes, for the bit error rate of dual-branch selection diversity based systems undergoing independent...

    Provided By King Fahd University of Petroleum & Minerals

  • White Papers // Nov 2010

    A Reliable Peer-to-Peer Protocol for Mobile Ad-Hoc Wireless Networks

    Reliable, fast, and power aware communication is needed for Ad-Hoc wireless networks. Current techniques based on client-server and Publish/Subscribe communication models are not suitable in multi-robot systems and generally for mobile applications. For this the authors propose a reliable peer-to-peer protocol based on a UDP Broadcast and Token Passing (UBTP)....

    Provided By King Fahd University of Petroleum & Minerals

  • White Papers // Nov 2010

    Enhanced Channel Estimation Using Cyclic Prefix in MIMO STBC OFDM Sytems

    Channel estimation is an important part of any receiver design. This paper presents an improved iterative joint channel estimation and data detection algorithm for Space Time Block Coded (STBC) MIMO OFDM systems in fast fading environments. The algorithm utilizes both time and frequency correlation information. The authors show how the...

    Provided By King Fahd University of Petroleum & Minerals

  • White Papers // Oct 2010

    Impulsive Noise Estimation and Cancellation in DSL Using Compressive Sampling

    Impulsive noise is the bottle neck that determines the maximum length of the DSL. Impulsive noise seldom occurs in DSL but when it occurs, it is very destructive and results in dropping the affected DSL symbols at the receiver as they cannot be recovered. By considering impulsive noise a sparse...

    Provided By King Fahd University of Petroleum & Minerals

  • White Papers // Sep 2010

    A Comparative Study of Gaussian Mixture Model and Radial Basis Function for Voice Recognition

    A comparative study of the application of Gaussian Mixture Model (GMM) and Radial Basis Function (RBF) in biometric recognition of voice has been carried out and presented. The application of machine learning techniques to biometric authentication and recognition problems has gained a widespread acceptance. In this paper, a GMM model...

    Provided By King Fahd University of Petroleum & Minerals

  • White Papers // Aug 2010

    A Simulation Study: The Impact of Random and Realistic Mobility Models on the Performance of Bypass-AODV in Ad Hoc Wireless Networks

    To bring VANET into reality, it is crucial to devise routing protocols that can exploit the inherited characteristics of VANET environment to enhance the performance of the running applications. Previous studies have shown that a certain routing protocol behaves differently under different presumed mobility patterns. Bypass-AODV is a new optimization...

    Provided By King Fahd University of Petroleum & Minerals

  • White Papers // Jun 2010

    Towards Green Computing Using Diskless High Performance Clusters

    In recent years, significant research has been conducted to boost the performance and increase the reliability of high performance computing (HPC) clusters. Such clusters are being used by Saudi Aramco's Exploration Computer Center (ECC) for oil reservoir simulations and exploration. As the number of compute nodes in modern HPC clusters...

    Provided By King Fahd University of Petroleum & Minerals

  • White Papers // Apr 2010

    Enhanced Equalization in OFDM Systems Using Cyclic Prefix

    Orthogonal Frequency Division Multiplexing (OFDM) is a modulation technique that provides high achievable data rates in wireless environment by combating multipath effects and has relatively simple implementation. In this paper, it is demonstrated that how the cyclic prefix can be used to enhance the operation of an OFDM equalizer when...

    Provided By King Fahd University of Petroleum & Minerals

  • White Papers // Apr 2010

    A New Client Interface Architecture for the Modified Fat Tree (MFT) Network-on-Chip (NoC) Topology

    A new client interface for the Modified Fat Tree (MFT) Network-on-Chip (NoC) is presented. It is directly inspired from the findings related to lane utilization and maximum FIFO sizes found in simulations of the MFT. A new smart arbitration circuit that efficiently realizes a round-robin scheduler between the receiving lanes...

    Provided By King Fahd University of Petroleum & Minerals

  • White Papers // Feb 2010

    ML Blind Channel Estimation in OFDM Using Cyclostationarity and Spectral Factorization

    Channel estimation is vital in OFDM systems for efficient data recovery. In this paper, the authors propose a blind algorithm for channel estimation that is based on the assumption that the transmitted data in an OFDM system is Gaussian (by central limit arguments). The channel estimate can then be obtained...

    Provided By King Fahd University of Petroleum & Minerals

  • White Papers // Jan 2010

    Native ATM Videoconferencing based on H.323

    Due to the potential of videoconference as a communication service, ITU-T has issued several standards that try to regulate its transmission and control protocols. ATM is considered a good transmission media for this kind of traffic, due to its ability to assure Quality of Service (QoS) parameters. In this paper...

    Provided By King Fahd University of Petroleum & Minerals

  • White Papers // Oct 2009

    An EM Based Frequency Domain Channel Estimation Algorithm for Multi-Access OFDM Systems

    Channel estimation is an important prerequisite for receiver design. In this paper the authors present a semi-blind low complexity frequency domain based channel estimation algorithm for multi-access Orthogonal Frequency Division Multiplexing (OFDM) systems. The algorithm is based on eigenvalues interpolation and makes a collective use of data and channel constraints....

    Provided By King Fahd University of Petroleum & Minerals

  • White Papers // Sep 2009

    Compressive Sensing Based Opportunistic Protocol for Throughput Improvement in Wireless Networks

    A key feature in the design of any MAC protocol is the throughput it can provide. In wireless networks, the channel of a user is not fixed but varies randomly. Thus, in order to maximize the throughput of the MAC protocol at any given time, only users with large channel...

    Provided By King Fahd University of Petroleum & Minerals

  • White Papers // Aug 2009

    A Simplified Router Architecture for the Modified Fat Tree Network-on-Chip Topology

    The architecture of the class of routers to implement the modified Fat Tree topology is shown. The router architecture is buffer-less with a simplified routing function. The routing function is obtained from a model that describes the Fat Tree topology and from where the equations governing the routing circuitry are...

    Provided By King Fahd University of Petroleum & Minerals

  • White Papers // Aug 2009

    Blind Channel Estimation in OFDM Systems by Relying on the Gaussian Assumption of the Input

    In an OFDM system, the receiver requires an estimate of the channel to recover the transmitted data. Most channel estimation methods rely on some form of training which reduces the useful data rate. Here instead the authors blindly estimate the channel by maximizing the log likelihood of the channel given...

    Provided By King Fahd University of Petroleum & Minerals

  • White Papers // May 2009

    Frequency Domain Estimation of Time Varying Channels in OFDMA Systems: An EM Approach

    OFDM modulation combines advantages of high achievable data rates and relatively easy implementation. However, for proper recovery of input, the OFDM receiver needs accurate channel information. Most algorithms proposed in literature perform channel estimation in time domain which increases computational complexity in multi-access situations where the user is only interested...

    Provided By King Fahd University of Petroleum & Minerals

  • White Papers // Apr 2009

    Multiuser Parameter Estimation Using Divided Difference Filter in CDMA Systems

    In this paper, the authors investigate time delay and channel gain estimation for multipath fading Code Division Multiple Access (CDMA) signals using the second order Divided Difference Filter (DDF). Given the nonlinear dependency of the channel parameters on the received signals in multiuser/multipath scenarios, they show that the DDF achieves...

    Provided By King Fahd University of Petroleum & Minerals

  • White Papers // Feb 2009

    Performance Evaluation of Scheduling Precedence-Constrained Computations on Message-Passing Systems

    Scheduling precedence graphs with communication times is the theoretical basis for achieving efficient parallelism in message-passing machines. The lack of global information on the tasks, due to communication, has lead to develop local scheduling heuristics such as the Earliest-Task-First. Using knowledge on computation, communication, and system topology, a class of...

    Provided By King Fahd University of Petroleum & Minerals

  • White Papers // Jan 2009

    Optimizing OSPF Routing Using Accelerated Iterative Heuristic

    The problem of setting Open Shortest Path First (OSPF) weights on links such that congestion can be avoided is proved to be NP-hard. Many iterative heuristics have been applied to solve the OSPF weight setting (OSPFWS) problem. As the size of any combinatorial optimization problem increases, it becomes more difficult...

    Provided By King Fahd University of Petroleum & Minerals

  • White Papers // Jan 2009

    Cyclic Prefix Based Enhanced Data Recovery in OFDM

    In this correspondence, the authors show how the cyclic prefix can be used to enhance the performance of an OFDM receiver. Specifically, they show how an OFDM symbol can be blindly detected using output symbol and associated cyclic prefix. The algorithm boils down to a nonlinear relationship involving the input...

    Provided By King Fahd University of Petroleum & Minerals

  • White Papers // Dec 2008

    An Analytical Simulator for Deploying IP Telephony

    Deploying IP telephony or Voice over IP (VoIP) is a major and challenging task. This paper describes an analytical design and planning simulator to assess the readiness of existing IP networks for the deployment of VoIP. The analytical simulator utilizes techniques used for network flows and queuing network analysis to...

    Provided By King Fahd University of Petroleum & Minerals

  • White Papers // Dec 2008

    Implementation and Experimental Performance Evaluation of a Hybrid Interrupt-Handling Scheme

    The performance of network hosts can be severely degraded when subjected to heavy traffic of today's Gigabit networks. This degradation occurs as a result of the interrupt overhead associated with the high rate of packet arrivals. NAPI, a packet reception mechanism integrated into the latest version of Linux networking subsystem,...

    Provided By King Fahd University of Petroleum & Minerals

  • White Papers // Jan 2008

    An OPNET-Based Simulation Approach for Deploying VoIP

    These days a massive deployment of VoIP is taking place over IP networks. VoIP deployment is a challenging task for network researchers and engineers. This paper presents a detailed simulation approach for deploying VoIP successfully. The simulation uses the OPNET network simulator. Recently OPNET has gained a considerable popularity in...

    Provided By King Fahd University of Petroleum & Minerals

  • White Papers // Jul 2012

    Low Complexity Blind Equalization for OFDM Systems with General Constellations

    This paper proposes a low-complexity algorithm for blind equalization of data in OFDM-based wireless systems with general constellation. The proposed algorithm is able to recover data even when the channel changes on a symbol-by-symbol basis, making it suitable for fast fading channels. The proposed algorithm does not require any statistical...

    Provided By King Fahd University of Petroleum & Minerals

  • White Papers // Jan 2010

    Native ATM Videoconferencing based on H.323

    Due to the potential of videoconference as a communication service, ITU-T has issued several standards that try to regulate its transmission and control protocols. ATM is considered a good transmission media for this kind of traffic, due to its ability to assure Quality of Service (QoS) parameters. In this paper...

    Provided By King Fahd University of Petroleum & Minerals

  • White Papers // Jun 2010

    Towards Green Computing Using Diskless High Performance Clusters

    In recent years, significant research has been conducted to boost the performance and increase the reliability of high performance computing (HPC) clusters. Such clusters are being used by Saudi Aramco's Exploration Computer Center (ECC) for oil reservoir simulations and exploration. As the number of compute nodes in modern HPC clusters...

    Provided By King Fahd University of Petroleum & Minerals

  • White Papers // Dec 2008

    An Analytical Simulator for Deploying IP Telephony

    Deploying IP telephony or Voice over IP (VoIP) is a major and challenging task. This paper describes an analytical design and planning simulator to assess the readiness of existing IP networks for the deployment of VoIP. The analytical simulator utilizes techniques used for network flows and queuing network analysis to...

    Provided By King Fahd University of Petroleum & Minerals

  • White Papers // Oct 2009

    An EM Based Frequency Domain Channel Estimation Algorithm for Multi-Access OFDM Systems

    Channel estimation is an important prerequisite for receiver design. In this paper the authors present a semi-blind low complexity frequency domain based channel estimation algorithm for multi-access Orthogonal Frequency Division Multiplexing (OFDM) systems. The algorithm is based on eigenvalues interpolation and makes a collective use of data and channel constraints....

    Provided By King Fahd University of Petroleum & Minerals

  • White Papers // Dec 2008

    Implementation and Experimental Performance Evaluation of a Hybrid Interrupt-Handling Scheme

    The performance of network hosts can be severely degraded when subjected to heavy traffic of today's Gigabit networks. This degradation occurs as a result of the interrupt overhead associated with the high rate of packet arrivals. NAPI, a packet reception mechanism integrated into the latest version of Linux networking subsystem,...

    Provided By King Fahd University of Petroleum & Minerals

  • White Papers // May 2009

    Frequency Domain Estimation of Time Varying Channels in OFDMA Systems: An EM Approach

    OFDM modulation combines advantages of high achievable data rates and relatively easy implementation. However, for proper recovery of input, the OFDM receiver needs accurate channel information. Most algorithms proposed in literature perform channel estimation in time domain which increases computational complexity in multi-access situations where the user is only interested...

    Provided By King Fahd University of Petroleum & Minerals

  • White Papers // Jan 2011

    Engineering Evolutionary Algorithm to Solve Multi-Objective OSPF Weight Setting Problem

    Setting weights for Open Shortest Path First (OSPF) routing protocol is an NP-hard problem. Optimizing these weights leads to less congestion in the network while utilizing link capacities efficiently. In this paper, Simulated Evolution (SimE), a non-deterministic iterative heuristic, is engineered to solve this problem. A cost function that depends...

    Provided By King Fahd University of Petroleum & Minerals

  • White Papers // Nov 2010

    A Reliable Peer-to-Peer Protocol for Mobile Ad-Hoc Wireless Networks

    Reliable, fast, and power aware communication is needed for Ad-Hoc wireless networks. Current techniques based on client-server and Publish/Subscribe communication models are not suitable in multi-robot systems and generally for mobile applications. For this the authors propose a reliable peer-to-peer protocol based on a UDP Broadcast and Token Passing (UBTP)....

    Provided By King Fahd University of Petroleum & Minerals

  • White Papers // Jan 2011

    Fuzzy Aggregating Functions for Multiobjective VLSI Placement

    When fuzzy logic is used with multiobjective optimization, min/max operators may not be desirable. This is primarily due to lack of compensation/submission of min/max. To over-come this, Ordered Weighted Averaging (OWA) operators were proposed by Yager. OWA requires the selection of a control parameter ?, which is different for different...

    Provided By King Fahd University of Petroleum & Minerals

  • White Papers // Aug 2009

    A Simplified Router Architecture for the Modified Fat Tree Network-on-Chip Topology

    The architecture of the class of routers to implement the modified Fat Tree topology is shown. The router architecture is buffer-less with a simplified routing function. The routing function is obtained from a model that describes the Fat Tree topology and from where the equations governing the routing circuitry are...

    Provided By King Fahd University of Petroleum & Minerals

  • White Papers // Apr 2010

    A New Client Interface Architecture for the Modified Fat Tree (MFT) Network-on-Chip (NoC) Topology

    A new client interface for the Modified Fat Tree (MFT) Network-on-Chip (NoC) is presented. It is directly inspired from the findings related to lane utilization and maximum FIFO sizes found in simulations of the MFT. A new smart arbitration circuit that efficiently realizes a round-robin scheduler between the receiving lanes...

    Provided By King Fahd University of Petroleum & Minerals

  • White Papers // Aug 2010

    A Simulation Study: The Impact of Random and Realistic Mobility Models on the Performance of Bypass-AODV in Ad Hoc Wireless Networks

    To bring VANET into reality, it is crucial to devise routing protocols that can exploit the inherited characteristics of VANET environment to enhance the performance of the running applications. Previous studies have shown that a certain routing protocol behaves differently under different presumed mobility patterns. Bypass-AODV is a new optimization...

    Provided By King Fahd University of Petroleum & Minerals

  • White Papers // Jan 2011

    Simulation-Based Comparative Study of on Demand Routing Protocols for MANET

    If the cable replacement feature of WLANs (Wireless LAN) is the core factor of its popularity, so is the non-existence of any prior infrastructure for MANET (Mobile Ad-hoc NETwork). The wireless links in an Ad-hoc network are highly error prone and can go down frequently because of node mobility, interference,...

    Provided By King Fahd University of Petroleum & Minerals

  • White Papers // Jan 2009

    Cyclic Prefix Based Enhanced Data Recovery in OFDM

    In this correspondence, the authors show how the cyclic prefix can be used to enhance the performance of an OFDM receiver. Specifically, they show how an OFDM symbol can be blindly detected using output symbol and associated cyclic prefix. The algorithm boils down to a nonlinear relationship involving the input...

    Provided By King Fahd University of Petroleum & Minerals

  • White Papers // Oct 2010

    Impulsive Noise Estimation and Cancellation in DSL Using Compressive Sampling

    Impulsive noise is the bottle neck that determines the maximum length of the DSL. Impulsive noise seldom occurs in DSL but when it occurs, it is very destructive and results in dropping the affected DSL symbols at the receiver as they cannot be recovered. By considering impulsive noise a sparse...

    Provided By King Fahd University of Petroleum & Minerals

  • White Papers // Nov 2010

    Enhanced Channel Estimation Using Cyclic Prefix in MIMO STBC OFDM Sytems

    Channel estimation is an important part of any receiver design. This paper presents an improved iterative joint channel estimation and data detection algorithm for Space Time Block Coded (STBC) MIMO OFDM systems in fast fading environments. The algorithm utilizes both time and frequency correlation information. The authors show how the...

    Provided By King Fahd University of Petroleum & Minerals

  • White Papers // Apr 2010

    Enhanced Equalization in OFDM Systems Using Cyclic Prefix

    Orthogonal Frequency Division Multiplexing (OFDM) is a modulation technique that provides high achievable data rates in wireless environment by combating multipath effects and has relatively simple implementation. In this paper, it is demonstrated that how the cyclic prefix can be used to enhance the operation of an OFDM equalizer when...

    Provided By King Fahd University of Petroleum & Minerals

  • White Papers // Feb 2010

    ML Blind Channel Estimation in OFDM Using Cyclostationarity and Spectral Factorization

    Channel estimation is vital in OFDM systems for efficient data recovery. In this paper, the authors propose a blind algorithm for channel estimation that is based on the assumption that the transmitted data in an OFDM system is Gaussian (by central limit arguments). The channel estimate can then be obtained...

    Provided By King Fahd University of Petroleum & Minerals

  • White Papers // Jan 2008

    An OPNET-Based Simulation Approach for Deploying VoIP

    These days a massive deployment of VoIP is taking place over IP networks. VoIP deployment is a challenging task for network researchers and engineers. This paper presents a detailed simulation approach for deploying VoIP successfully. The simulation uses the OPNET network simulator. Recently OPNET has gained a considerable popularity in...

    Provided By King Fahd University of Petroleum & Minerals

  • White Papers // Jul 2011

    A Robust LMS Adaptive Algorithm Over Distributed Networks

    This paper explains the effect of erroneous noise power estimates on the behavior of noise constrained diffusion based adaptive algorithm for distributed adaptive networks. The Noise Constrained Diffusion Least Mean Square (NCDLMS) algorithm assumes knowledge of the noise variance is available at each node for good performance. Here, it is...

    Provided By King Fahd University of Petroleum & Minerals

  • White Papers // Mar 2011

    A Numerical Comparison Between LSSTC and VBLAST in Wireless Systems

    In this paper, the authors evaluate a recently proposed Multiple-Input Multiple-Output (MIMO) system called the Layered Steered Space-Time Codes (LSSTC) that combines the benefits of Vertical Bell Labs Space-Time (VBLAST) scheme, Space-Time Block Codes (STBC) and beamforming. This evaluation is done by comparing the capacity and the error rate of...

    Provided By King Fahd University of Petroleum & Minerals

  • White Papers // Jan 2012

    A Secure, Publisher-Centric Web Caching Infrastructure

    The current Web cache infrastructure, though it has a number of performance benefits, does not address many of the publishers' requirements. The authors argue that web caches should be enhanced to address publishers' needs. For example, caches will need to log client accesses, run scripts to dynamically produce content, and...

    Provided By King Fahd University of Petroleum & Minerals

  • White Papers // Sep 2010

    A Comparative Study of Gaussian Mixture Model and Radial Basis Function for Voice Recognition

    A comparative study of the application of Gaussian Mixture Model (GMM) and Radial Basis Function (RBF) in biometric recognition of voice has been carried out and presented. The application of machine learning techniques to biometric authentication and recognition problems has gained a widespread acceptance. In this paper, a GMM model...

    Provided By King Fahd University of Petroleum & Minerals

  • White Papers // Jan 2009

    Optimizing OSPF Routing Using Accelerated Iterative Heuristic

    The problem of setting Open Shortest Path First (OSPF) weights on links such that congestion can be avoided is proved to be NP-hard. Many iterative heuristics have been applied to solve the OSPF weight setting (OSPFWS) problem. As the size of any combinatorial optimization problem increases, it becomes more difficult...

    Provided By King Fahd University of Petroleum & Minerals

  • White Papers // Aug 2009

    Blind Channel Estimation in OFDM Systems by Relying on the Gaussian Assumption of the Input

    In an OFDM system, the receiver requires an estimate of the channel to recover the transmitted data. Most channel estimation methods rely on some form of training which reduces the useful data rate. Here instead the authors blindly estimate the channel by maximizing the log likelihood of the channel given...

    Provided By King Fahd University of Petroleum & Minerals

  • White Papers // Feb 2009

    Performance Evaluation of Scheduling Precedence-Constrained Computations on Message-Passing Systems

    Scheduling precedence graphs with communication times is the theoretical basis for achieving efficient parallelism in message-passing machines. The lack of global information on the tasks, due to communication, has lead to develop local scheduling heuristics such as the Earliest-Task-First. Using knowledge on computation, communication, and system topology, a class of...

    Provided By King Fahd University of Petroleum & Minerals

  • White Papers // Jan 2011

    On the Possibility of Consensus in Asynchronous Systems

    The authors demonstrate that the leader election and consensus problems are solvable in a timed asynchronous distributed system provided a majority of processes are always eventually able to communicate in a timely manner for a sufficiently long time. Failures and recoveries affecting the other processes and the communications between them...

    Provided By King Fahd University of Petroleum & Minerals

  • White Papers // Jan 2011

    OSPF Weight Setting Optimization for Single Link Failures

    In operational networks, nodes are connected via multiple links for load sharing and redundancy. This is done to make sure that a failure of a link does not disconnect or isolate some parts of the network. However, link failures have an effect on routing, as the routers find alternate paths...

    Provided By King Fahd University of Petroleum & Minerals

  • White Papers // Sep 2009

    Compressive Sensing Based Opportunistic Protocol for Throughput Improvement in Wireless Networks

    A key feature in the design of any MAC protocol is the throughput it can provide. In wireless networks, the channel of a user is not fixed but varies randomly. Thus, in order to maximize the throughput of the MAC protocol at any given time, only users with large channel...

    Provided By King Fahd University of Petroleum & Minerals

  • White Papers // Dec 2010

    A New Formula for the BER of Binary Modulations With Dual-Branch Selection Over Generalized-K Composite Fading Channels

    Error performance is one of the main performance measures and derivation of its closed-form expression has proved to be quite involved for certain systems. In this paper, a unified closed-form expression, applicable to different binary modulation schemes, for the bit error rate of dual-branch selection diversity based systems undergoing independent...

    Provided By King Fahd University of Petroleum & Minerals

  • White Papers // Apr 2009

    Multiuser Parameter Estimation Using Divided Difference Filter in CDMA Systems

    In this paper, the authors investigate time delay and channel gain estimation for multipath fading Code Division Multiple Access (CDMA) signals using the second order Divided Difference Filter (DDF). Given the nonlinear dependency of the channel parameters on the received signals in multiuser/multipath scenarios, they show that the DDF achieves...

    Provided By King Fahd University of Petroleum & Minerals