The Experts below are selected from a list of 51072 Experts worldwide ranked by ideXlab platform

Chandra R. Murthy - One of the best experts on this subject based on the ideXlab platform.

  • Group Testing-Based Spectrum Hole Search for Cognitive Radios
    IEEE Transactions on Vehicular Technology, 2014
    Co-Authors: Abhay Sharma, Chandra R. Murthy
    Abstract:

    This paper investigates the use of adaptive group testing to find a Spectrum Hole of a specified bandwidth in a given wideband of interest. We propose a group testing-based Spectrum Hole search algorithm that exploits sparsity in the primary spectral occupancy by testing a group of adjacent subbands in a single test. This is enabled by a simple and easily implementable sub-Nyquist sampling scheme for signal acquisition by the cognitive radios (CRs). The sampling scheme deliberately introduces aliasing dur- ing signal acquisition, resulting in a signal that is the sum of signals from adjacent subbands. Energy-based hypothesis tests are used to provide an occupancy decision over the group of subbands, and this forms the basis of the proposed algorithm to find contiguous Spectrum Holes of a specified bandwidth. We extend this frame- work to a multistage sensing algorithm that can be employed in a variety of Spectrum sensing scenarios, including noncontiguous Spectrum Hole search. Furthermore, we provide the analytical means to optimize the group tests with respect to the detection thresholds, number of samples, group size, and number of stages to minimize the detection delay under a given error probability constraint. Our analysis allows one to identify the sparsity and SNR regimes where group testing can lead to significantly lower detection delays compared with a conventional bin-by-bin energy detection scheme; the latter is, in fact, a special case of the group test when the group size is set to 1 bin. We validate our analytical results via Monte Carlo simulations.

  • GLOBECOM - A group testing based Spectrum Hole search using a simple sub-Nyquist sampling scheme
    2012 IEEE Global Communications Conference (GLOBECOM), 2012
    Co-Authors: Abhay Sharma, Chandra R. Murthy
    Abstract:

    In this paper, we consider the problem of finding a Spectrum Hole of a specified bandwidth in a given wide band of interest. We propose a new, simple and easily implementable sub-Nyquist sampling scheme for signal acquisition and a Spectrum Hole search algorithm that exploits sparsity in the primary spectral occupancy in the frequency domain by testing a group of adjacent subbands in a single test. The sampling scheme deliberately introduces aliasing during signal acquisition, resulting in a signal that is the sum of signals from adjacent sub-bands. Energy-based hypothesis tests are used to provide an occupancy decision over the group of subbands, and this forms the basis of the proposed algorithm to find contiguous Spectrum Holes. We extend this framework to a multi-stage sensing algorithm that can be employed in a variety of Spectrum sensing scenarios, including non-contiguous Spectrum Hole search. Further, we provide the analytical means to optimize the hypothesis tests with respect to the detection thresholds, number of samples and group size to minimize the detection delay under a given error rate constraint. Depending on the sparsity and SNR, the proposed algorithms can lead to significantly lower detection delays compared to a conventional bin-by-bin energy detection scheme; the latter is in fact a special case of the group test when the group size is set to 1. We validate our analytical results via Monte Carlo simulations.

  • On the design of location-invariant sensing performance for secondary users
    2009 First UK-India International Workshop on Cognitive Wireless Systems (UKIWCWS), 2009
    Co-Authors: Srikanth B. Pai, Tanumay Datta, Chandra R. Murthy
    Abstract:

    In this article, we consider the setting of one-shot Spectrum Hole detection for a uniformly distributed secondary network under fading and path loss. We separate the sensors that are used to detect spectral Holes from the secondary transmitters, thus allowing each secondary transmitter to benefit from the decisions of multiple (shared)sensors. The detection performance of the sensors varies with the distance from the primary transmitter. Thus a secondary listens to different average number of sensors as it moves around the cell, making the fusion rule complicated. We coin the term communicating shaping function f that is used by the sensors to modulate the coverage area of the sensors. A shaping function is designed heuristically so that the area of coverage normalised by the detection probability of the sensors is the same throughout the cell. This makes the average number of communicating sensors seen by a secondary invariant to the location of the secondary users, allowing a fixed location-invariant fusion rule to be employed at the secondary transmitter.

Brian L Mark - One of the best experts on this subject based on the ideXlab platform.

  • Opportunistic Spectrum sharing with multiple cochannel primary transmitters
    IEEE Transactions on Wireless Communications, 2009
    Co-Authors: Ahmed O. Nasif, Brian L Mark
    Abstract:

    We present a distributed, collaborative algorithm to enable opportunistic Spectrum access for cognitive radios in the presence of multiple cochannel transmitters. A Spectrum Hole detection and estimation technique based on received signal strength observations is developed, which allows the coexistence of both licensed and unlicensed transmitters. We address the issues of how to perform collaborative Spectrum sensing in the presence of multiple cochannel transmitters and how to determine the maximum transmit power that can be used for a given frequency channel by a cognitive radio while avoiding harmful interference to the licensed network. Simulation results are provided to validate the feasibility and performance of the proposed scheme.

  • estimation of maximum interference free power level for opportunistic Spectrum access
    IEEE Transactions on Wireless Communications, 2009
    Co-Authors: Brian L Mark, Ahmed O. Nasif
    Abstract:

    We consider a scenario in which frequency agile radios opportunistically share a fixed Spectrum resource with a set of primary nodes. We develop a collaborative scheme for a group of frequency agile radios to estimate the maximum power at which they can transmit on a given frequency channel, without causing harmful interference to the primary receivers. The proposed scheme relies on signal strength measurements taken by a group of frequency agile radios, which are then used by a target node to characterize the spatial size of its perceived Spectrum Hole in terms of the maximum permissible transmit power. We derive an approximation to the maximum interference-free transmit power using the Cramer-Rao bound on localization accuracy. We present numerical results to demonstrate the effectiveness of the proposed scheme under a variety of scenarios.

  • a framework for cognitive wimax with frequency agility
    Proceedings of the IEEE, 2009
    Co-Authors: A E Leu, Brian L Mark, M A Mchenry
    Abstract:

    Cognitive radios have the ability to sense the radio Spectrum environment and to switch dynamically to available frequency ranges. Mobile WiMax is an emerging wireless networking standard that could potentially benefit from cognitive radio technology. We develop a framework for applying cognitive radio technology to mobile WiMax networks to increase capacity and simplify network operations. In the proposed cognitive WiMax architecture, base stations are equipped with sensitive detectors and assign channels to subscriber stations dynamically based on Spectrum availability. Power control is employed to increase frequency reuse in conjunction with Spectrum sensing. Using computer simulation, we evaluate the performance of ldquocognitive channel assignmentrdquo relative to conventional dynamic channel assignment. Our numerical results show that cognitive radios can substantially increase the capacity of emerging WiMax networks by exploiting inherent Spectrum Hole opportunities. The key performance parameters determining the achievable capacity of cognitive WiMax networks are the detection and interference range, which depend in turn on characteristics of the radio propagation environment.

  • GLOBECOM - Collaborative Opportunistic Spectrum Access in the Presence of Multiple Transmitters
    IEEE GLOBECOM 2008 - 2008 IEEE Global Telecommunications Conference, 2008
    Co-Authors: Ahmed O. Nasif, Brian L Mark
    Abstract:

    We present a collaborative algorithm to enable opportunistic Spectrum access for cognitive radios in the presence of multiple co-channel transmitters. A Spectrum Hole detection and estimation technique based on received signal strength observations is developed, which allows the coexistence of both licensed and unlicensed transmitters. We address the issue of how to perform collaborative Spectrum sensing in the presence of multiple co-channel transmitters and how to determine the maximum transmit power that can be used for a given frequency channel by a cognitive radio while avoiding harmful interference to the licensed network. We provide some simulation results to validate the feasibility of our approach.

Ahmed O. Nasif - One of the best experts on this subject based on the ideXlab platform.

  • Opportunistic Spectrum sharing with multiple cochannel primary transmitters
    IEEE Transactions on Wireless Communications, 2009
    Co-Authors: Ahmed O. Nasif, Brian L Mark
    Abstract:

    We present a distributed, collaborative algorithm to enable opportunistic Spectrum access for cognitive radios in the presence of multiple cochannel transmitters. A Spectrum Hole detection and estimation technique based on received signal strength observations is developed, which allows the coexistence of both licensed and unlicensed transmitters. We address the issues of how to perform collaborative Spectrum sensing in the presence of multiple cochannel transmitters and how to determine the maximum transmit power that can be used for a given frequency channel by a cognitive radio while avoiding harmful interference to the licensed network. Simulation results are provided to validate the feasibility and performance of the proposed scheme.

  • estimation of maximum interference free power level for opportunistic Spectrum access
    IEEE Transactions on Wireless Communications, 2009
    Co-Authors: Brian L Mark, Ahmed O. Nasif
    Abstract:

    We consider a scenario in which frequency agile radios opportunistically share a fixed Spectrum resource with a set of primary nodes. We develop a collaborative scheme for a group of frequency agile radios to estimate the maximum power at which they can transmit on a given frequency channel, without causing harmful interference to the primary receivers. The proposed scheme relies on signal strength measurements taken by a group of frequency agile radios, which are then used by a target node to characterize the spatial size of its perceived Spectrum Hole in terms of the maximum permissible transmit power. We derive an approximation to the maximum interference-free transmit power using the Cramer-Rao bound on localization accuracy. We present numerical results to demonstrate the effectiveness of the proposed scheme under a variety of scenarios.

  • GLOBECOM - Collaborative Opportunistic Spectrum Access in the Presence of Multiple Transmitters
    IEEE GLOBECOM 2008 - 2008 IEEE Global Telecommunications Conference, 2008
    Co-Authors: Ahmed O. Nasif, Brian L Mark
    Abstract:

    We present a collaborative algorithm to enable opportunistic Spectrum access for cognitive radios in the presence of multiple co-channel transmitters. A Spectrum Hole detection and estimation technique based on received signal strength observations is developed, which allows the coexistence of both licensed and unlicensed transmitters. We address the issue of how to perform collaborative Spectrum sensing in the presence of multiple co-channel transmitters and how to determine the maximum transmit power that can be used for a given frequency channel by a cognitive radio while avoiding harmful interference to the licensed network. We provide some simulation results to validate the feasibility of our approach.

Syed Hasnain Raza Tirmazi - One of the best experts on this subject based on the ideXlab platform.

  • Spectrum estimation and Spectrum Hole opportunities prediction for cognitive radios using higher-order statistics
    2011 Wireless Advanced WiAd 2011, 2011
    Co-Authors: Ahmad Ali Tabassam, Muhammad Uzair Suleman, Sheheryar Khan, Syed Hasnain Raza Tirmazi
    Abstract:

    Cognitive Radio (CR) is a wireless advanced technology which can utilize an unlicensed as well as a licensed Spectrum without a harmful interference to the primary users. An unbiased consistent Spectrum estimator is required for the primary user's detection (sensing) for distinguishing the narrow band signals in a noisy environment. Cognitive radio's hardware solutions available in a commercial market are frequency band constrained at RF Front-End. In multi-dimensional radio Spectrum space any of the dimension: time, frequency, code or space can be used as a transmission opportunity. The Spectrum Hole time opportunistic prediction is a promising solution to determine the free time slots for transmission within a frequency band. This paper presents classical and parametric statistical Spectrum estimators for primary user's detection. It also presents statistical auto-regressive and moving average predictive modeling for grey-Hole Spectrum opportunities prediction in a time domain for cognitive radios where frequency, code and space (geographical location) are operational constraints. A prototype system for a cognitive radio is built on top of the software-defined radio in a MATLAB/-Simulink and interfaced with an USRP2 main-board and RFX2400 daughter-board from Ettus Research LLC.

Abhay Sharma - One of the best experts on this subject based on the ideXlab platform.

  • Group Testing-Based Spectrum Hole Search for Cognitive Radios
    IEEE Transactions on Vehicular Technology, 2014
    Co-Authors: Abhay Sharma, Chandra R. Murthy
    Abstract:

    This paper investigates the use of adaptive group testing to find a Spectrum Hole of a specified bandwidth in a given wideband of interest. We propose a group testing-based Spectrum Hole search algorithm that exploits sparsity in the primary spectral occupancy by testing a group of adjacent subbands in a single test. This is enabled by a simple and easily implementable sub-Nyquist sampling scheme for signal acquisition by the cognitive radios (CRs). The sampling scheme deliberately introduces aliasing dur- ing signal acquisition, resulting in a signal that is the sum of signals from adjacent subbands. Energy-based hypothesis tests are used to provide an occupancy decision over the group of subbands, and this forms the basis of the proposed algorithm to find contiguous Spectrum Holes of a specified bandwidth. We extend this frame- work to a multistage sensing algorithm that can be employed in a variety of Spectrum sensing scenarios, including noncontiguous Spectrum Hole search. Furthermore, we provide the analytical means to optimize the group tests with respect to the detection thresholds, number of samples, group size, and number of stages to minimize the detection delay under a given error probability constraint. Our analysis allows one to identify the sparsity and SNR regimes where group testing can lead to significantly lower detection delays compared with a conventional bin-by-bin energy detection scheme; the latter is, in fact, a special case of the group test when the group size is set to 1 bin. We validate our analytical results via Monte Carlo simulations.

  • GLOBECOM - A group testing based Spectrum Hole search using a simple sub-Nyquist sampling scheme
    2012 IEEE Global Communications Conference (GLOBECOM), 2012
    Co-Authors: Abhay Sharma, Chandra R. Murthy
    Abstract:

    In this paper, we consider the problem of finding a Spectrum Hole of a specified bandwidth in a given wide band of interest. We propose a new, simple and easily implementable sub-Nyquist sampling scheme for signal acquisition and a Spectrum Hole search algorithm that exploits sparsity in the primary spectral occupancy in the frequency domain by testing a group of adjacent subbands in a single test. The sampling scheme deliberately introduces aliasing during signal acquisition, resulting in a signal that is the sum of signals from adjacent sub-bands. Energy-based hypothesis tests are used to provide an occupancy decision over the group of subbands, and this forms the basis of the proposed algorithm to find contiguous Spectrum Holes. We extend this framework to a multi-stage sensing algorithm that can be employed in a variety of Spectrum sensing scenarios, including non-contiguous Spectrum Hole search. Further, we provide the analytical means to optimize the hypothesis tests with respect to the detection thresholds, number of samples and group size to minimize the detection delay under a given error rate constraint. Depending on the sparsity and SNR, the proposed algorithms can lead to significantly lower detection delays compared to a conventional bin-by-bin energy detection scheme; the latter is in fact a special case of the group test when the group size is set to 1. We validate our analytical results via Monte Carlo simulations.