W.J. Barnes

University of Oklahoma, Oklahoma City, OK, United States

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Publications (11)1.77 Total impact

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    ABSTRACT: The speed and accuracy of spectrum sensing techniques are essential factors in the performance of cognitive radio networks. The limitations imposed by computational complexity and limited monitoring time window impede the success of spectrum sensing operation performed by cognitive radio nodes. Compressive sensing technique is viewed as a novel approach to solve scalability problems in some signal processing operations. One popular application of compressed sensing is sizable image recovery. This technique can be used in spectrum sensing applications to reduce the barriers of current spectrum sensing computational requirements. The success of this technique will result in faster sensing operations, less complex sensing modules, or wider spectrum sensing capabilities. The coming IEEE 802.22 air interface standard aims to provide wireless services in wireless regional area network using TV spectrum white spaces. This standard is considered as the first standard that is based on cognitive radio approach. Spectrum sensing is a critical functionality that needs to be performed by 802.22 compliant devices. While, the standard does not specify any spectrum sensing method, it requires the sensing operation to be performed within timing and accuracy constraints. This work in progress is investigating the feasibility of using one of the compressive sensing techniques named Fast Fourier Sampling to detect wireless microphone signals for IEEE 802.22 air interface.
    INFOCOM IEEE Conference on Computer Communications Workshops , 2010; 04/2010
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    N.J. LaSorte, W.J. Barnes, H.H. Refai
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    ABSTRACT: This work presents the results of a survey of the electromagnetic environment from 30 MHz-7 GHz in St. Francis Hospital, in Tulsa, Oklahoma. Measurements were considered short term as the full spectrum was measured in twelve minutes. The results show the dynamic environment apparent in today's hospitals. There were no recorded cases in which the IEC immunity standard specifications, 3V/m, was exceeded. Another contribution by this paper was to show an example of cross-floor attenuation in a hospital.
    Electromagnetic Compatibility, 2009. EMC 2009. IEEE International Symposium on; 09/2009
  • W.J. Barnes, N. LaSorte, H. Refai, M.B. Yeary
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    ABSTRACT: The flexible architecture provided by cognitive radio has spurned renewed interest in spectrum monitoring. To enable blind signal demodulation, the symbol rate must be determined. Recent techniques for determining symbol rates follow one of two broad approaches. The first approach estimates the carrier frequency and down-converts the signal for analysis at base-band. This approach is computationally expensive as carrier extraction hardware is needed for each modulation scheme. The other approach applies the wavelet transform to an over-sampled received signal to detect phase jumps and frequency changes. This paper introduces a new approach for detecting modulation-based carrier changes by monitoring the behaviour of an error signal associated with a direct frequency estimator. The proposed method has a simple architecture and eliminates the need for over-sampling seen in the wavelet transform approach. Symbol rate estimations were made under different carrier-to-noise ratios (CNRs) and modulation types and the results are provided.
    Instrumentation and Measurement Technology Conference, 2009. I2MTC '09. IEEE; 06/2009
  • Yahia Tachwali, W. Justin Barnes, Hazem H. Refai
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    ABSTRACT: In many synchronous receivers, symbol timing synchronization is achieved through implementation of an analog phase locked loop (PLL). A phase detector and voltage-controlled oscillator drive a reference signal to be in phase with the received training sequence. Due to the quick phase convergence this option is attractive; however, limitations in pre-packaged hardware make this approach infeasible at times. Changes in the received symbol rate in software radio applications can further complicate the hardware implementation by requiring additional control signals to alter the frequency of the reference signal. This paper examines a configurable symbol synchronizer for software-defined radio (SDR) architecture with a predefined RF front end. In this scenario, we implement a typical method for digital phase locking and make it adaptable to different data rates. A pre-synchronization step is used to provide a reasonable initial estimate for the received symbol period for lower, over-sampled data rates. This decreases the synchronization time while maintaining a constant sampling period at the ADC. It also maintains the down-conversion stage at the receiver. The paper shows the feasibility of this architecture to support wide range of symbol rates.
    Journal of Network and Computer Applications 05/2009; 32:607-615. · 1.77 Impact Factor
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    N. LaSorte, W.J. Barnes, B. Zigreng, H. Refai
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    ABSTRACT: This paper presents an evaluation of a deployed WiMAX system operating in the 4.9 GHz Public Safety Band in the City of Tulsa. The study includes propagation analysis for the coverage and network performance tests to demonstrate the viability of a WiMAX system as a medium for public safety. We considered existing propagation models in the UHF band (300 MHz to 3 GHz) to be applied to 4.9 GHz and compared the characteristics predicted by the models with the measured data. The results show that of the three models presented, the Cost-231 Hata Model best predicts the characteristics of the deployed WiMAX system. Network performance tests were also conducted to measure the throughput of the system at various adaptive modulation rates.
    Consumer Communications and Networking Conference, 2009. CCNC 2009. 6th IEEE; 02/2009
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    Nick LaSorte, W. Justin Barnes, Hazem H. Refai
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    ABSTRACT: This paper depicts the development of Orthogonal Frequency Division Multiplexing from a historical perspective. A summary of major research milestones are noted that contributed to modern-day OFDM. These contributions include the use of discrete Fourier transforms replacing the analog implementation and addition of cyclic extensions to ensure orthogonality among the sub-channels. Also, channel equalization algorithms to suppress inter-symbol interference and inter-carrier interference, channel estimation through the insertion of pilot tones among data blocks, peak-to-average power ratio reduction, and synchronization techniques are discussed.
    Proceedings of the Global Communications Conference, 2008. GLOBECOM 2008, New Orleans, LA, USA, 30 November - 4 December 2008; 01/2008
  • W. Justin Barnes, Yahia Tachwali, Hazem H. Refai
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    ABSTRACT: This paper provides a comprehensive symbol synchronization architecture for deployment in configurable digital receivers. While this is a well researched topic for static symbol rate conditions, significant work remains to be done in determining how to best implement variable data rates and training sequences while maintaining functionality. The synchronizer architecture is a modified version of the basic analog architecture for DSSS synchronizers making it applicable to both wideband and narrowband signals. A known training sequence is received and synchronized to within a half chip accuracy by delaying the generated sequence by half of a chip every sequence period and comparing the correlation to a set threshold. A delay-locked loop (DLL) uses the difference between early and late correlations to drive fine synchronization process. This process is made configurable with the knowledge of the number of samples per symbol, training sequence, sequence length, data rate, and coarse correlation threshold.
    Proceedings of the Global Communications Conference, 2008. GLOBECOM 2008, New Orleans, LA, USA, 30 November - 4 December 2008; 01/2008
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    ABSTRACT: A number of innovative methodologies have been developed in an effort to stem the number of collisions that occur at intersections. A number of collision avoidance systems involve the deployment of sensors before the intersection to relay important information to the base station (BS) which controls a stop/warning signal visible to the driver. To this end a study of the limitations that sensor-intersection distance, sensor spacing, the number of sensors, measurement noise and variance in acceleration of a vehicle are examined through simulation of a sensor network. Specifically, a network employing magnetic field sensors that communicate wirelessly with the BS is examined, with the idea that general design principles can be applied to various other types of sensor networks. Special emphasis is placed on rural intersections which typically have static intersection driver directions (stop/yield signs) rather than traffic lights. Thorough analysis of the simulated system performance under ideal and non-ideal conditions is provided.
    Intelligent Transportation Systems Conference, 2007. ITSC 2007. IEEE; 01/2007
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    ABSTRACT: With a growing number of vehicles entering roadways, it is important to take the initiative to decrease the number of collisions occurring on them. Intersections, in particular, are notorious for collisions. Unfortunately, due to the complexity of human driver behavior, there is limited technology capable of addressing this problem today. In rural areas, where non-stopping highways intersect with lower-traffic channels, the high speeds of the highway traffic make crossing and merging onto the road treacherous. Failure to yield to the higher priority traffic, for any reason, can have dire consequences. This paper describes a wireless intersection collision avoidance system (WICAS), an intelligent transportation system (ITS) technology to help mitigate collisions at intersections, particularly rural highway intersections based on a Kalman prediction algorithm that receives updated position and velocity estimates from deployed sensors.
    Intelligent Transportation Systems Conference, 2007. ITSC 2007. IEEE; 01/2007
  • Source
    Y Tachwali, F Basma, W J Barnes, H H Refai
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    ABSTRACT: The speed and accuracy of spectrum sensing techniques are essential factors in the performance of cognitive radio networks. The limitations imposed by computational complexity and a shortened monitoring time impede the success of spectrum sensing operation performed by cognitive radio nodes. Compressive sensing techniques are viewed as novel approaches to solve scalability problems in some signal processing operations. One popular application of compressed sensing is sizable image recovery. This technique can be used in spectrum sensing applications to reduce the barriers of current spectrum sensing computational requirements. The successful application of these techniques will result in faster sensing operations, less complex sensing modules, or wider spectrum sensing capabilities. The coming IEEE 802.22 air interface standard aims to provide wireless services in regional area networks using TV spectrum white spaces. This standard is considered the first standard that is based on a cognitive radio approach. Spectrum sensing is a critical functionality that needs to be performed by 802.22 compliant devices. While, the standard does not specify any spectrum sensing method, it requires the sensing operation to be performed within timing and accuracy constraints. This simulation study investigates the impact of different configuration parameters of a compressive sensing technique called Fast Fourier Sampling to detect wireless microphone signals as dictated by the IEEE 802.22 air interface.
  • Source
    Nickolas J Lasorte, W Justin Barnes, Hazem H Refai
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    ABSTRACT: An examination of the electromagnetic environment from 30MHz-7GHz in St. Francis Hospital, in Tulsa, Oklahoma is the focus of this paper. Measurements were considered short term as the full spectrum was measured in twelve minutes. An experimental characterization of building penetration 55-1950MHz was performed. In contrast to other buildings, most hospitals are constructed with special walls that include metallic layers. Building penetration loss for a hospital is the main contribution of this paper. The measurement data is useful for network designers and hospital engineers.