| 1. |
- Hamid, Mohamed, 1983-, et al.
(författare)
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Multi-Interference Detection Algorithm using Discriminant Analysis in Industrial Environments
- 2013
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Ingår i: 39th Annual Conference of the IEEE Industrial Electronics Society (IECON 2013). - New York : IEEE conference proceedings. - 9781479902248 ; , s. 5600-5604
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Konferensbidrag (refereegranskat)abstract
- In this paper a technique to detect multiple impulsive interference in an industrial environment is proposed and evaluated. The technique is based on discriminant analysis which iteratively peels-off the impulsive interferences. The probability of detection of the technique is tested with and without the iterative peeling-off part. The simulations show that the SIR can be improved by applying the detection technique and then blank or clip the impulsive interference components. The improvement in the SIR depends on the impulsive interference parameters and it can reach up to 17 dB.
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| 2. |
- Hamid, Mohamed, 1983-, et al.
(författare)
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A Novel Approach for Energy Detector Sensing Time and Periodic Sensing Interval Optimization in Cognitive Radios
- 2011
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Ingår i: CogART '11 Proceedings of the 4th International Conference on Cognitive Radio and Advanced Spectrum Management. - New York, NY, USA : ACM. - 9781450309127
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Konferensbidrag (refereegranskat)abstract
- In this paper a new approach of optimizing the sensing time and periodic sensing interval for energy detectors has been explored. This new approach is built upon maximizing the probability of right detection, captured opportunities and transmission efficiency. The probability of right detection is defined as the probability of having no false alarm and correct detection. Optimization of the sensing time relies on maximizing the summation of the probability of right detection and the transmission efficiency while optimization of periodic sensing interval subject to maximizing the summation of transmission efficiency and the captured opportunities. The optimum sensing time and periodic sensing interval are dependent on each other, hence, iterative approach to optimize them is applied and convergence criterion is defined. The simulations show that both converged sensing time and periodic sensing interval increase with the increase of the channel utilization factor, moreover, the probability of false alarm, the probability of detection, the probability of right detection, the transmission efficiency and the captured opportunities have been taken as the detector performance metrics and evaluated for different values of channel utilization factor and signal-to-noise ratio.
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| 3. |
- Hamid, Mohamed, 1983-, et al.
(författare)
-
Blind spectrum sensing for cognitive radios using discriminant analysis : A novel approach
- 2013
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Ingår i: IEEE Transactions on Instrumentation and Measurement. - : IEEE. - 0018-9456 .- 1557-9662. ; 62:11, s. 2912-2921
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, we present a new spectrum sensing technique for cognitive radios based on discriminant analysis called spectrum discriminator. The presented technique uses the knowledge of the noise uncertainty and a probabilistic validation to overcome the limitations of the discriminant analysis. A comparative study between the proposed technique and the maximum-minimum eigenvalue detection has been performed based on two performance metrics: the probability of false alarm and the probability of detection. The spectrum discriminator has been further developed to a peel-off technique where all primary users can be detected. The performance of the spectrum discriminator and the peel-off technique has been tested on simulations and experimentally verified. The comparative study is based on simulations as well as measurements.
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| 4. |
- Hamid, Mohamed, 1983-, et al.
(författare)
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Downlink Throughput Driven Channel Access Framework for Cognitive LTE Femto-Cells
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- This paper proposes an optimized sensing based channel access framework for the LTE cognitive femto cells with an objective of maximizing femto-cells downlink throughput. Energy detection is used by the LTE cognitive femto cells to locate and thereafter utilize the free channels. Moreover, periodic sensing is adopted to detect any changes of the sensing outcomes. The developed channel access framework is based on an objective of maximization the femto-cell downlink throughput which varies with the macro-cell channel occupancy. Therefore, the LTE macro-cell occupancy statistics are empirically modelled using exponential distributions mixture. The LTE cognitive femto-cell downlink throughput is maximized by compromising the transmission efficiency, the explored spectrum opportunities and the interference from the macro-cell. An analytical solution for the optimal periodic sensing interval that maximizes the throughput is found and verified by simulations. The obtained results show that there is indeed a single periodic sensing interval value that maximizes the LTE cognitive femto-cell downlink throughput which changes with the change of the macro-cell channel occupancy. Yet, at a specific channel occupancy statistical parameters, our framework provides the optimal throughput. At the peak of the macro-cell traffic, our framework increased the femto-cell throughput by $\simeq 15\%$ compared to the senseless case. The impact of the available channels for opportunistic access is studied. The simulation results show that increasing the number of the available channels becomes less significant for more than three channels.
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| 5. |
- Hamid, Mohamed, 1983-, et al.
(författare)
-
Empirical Statistical Model for LTE Downlink Channel Occupancy
- 2017
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Ingår i: Wireless personal communications. - : Springer Science and Business Media LLC. - 0929-6212 .- 1572-834X. ; 96:1, s. 855-866
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Tidskriftsartikel (refereegranskat)abstract
- This paper develops an empirical statistical channel occupancy model for downlink long-term evolution (LTE) cellular systems. The model is based on statistical distributions mixtures for the holding times of the channels. Moreover, statistical distribution of the time when the channels are free is also considered. The data is obtained through an extensive measurement campaign performed in Stockholm, Sweden. Two types of mixtures are considered, namely, exponential and log-normal distributions to fit the measurement findings. The log-likelihood of both mixtures is used as a quantitative measure of the goodness of fit. Moreover, finding the optimal number of linearly combined distributions using the Akaike information criterion (AIC) is investigated. The results show that good fitting can be obtained by using either exponential or log-normal distributions mixture. Even though, the fitting is done for a representative case with a tempo-spatial consideration, the model is yet applicable in general for LTE and other cellular systems in a wider sense.
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| 6. |
- Hamid, Mohamed, 1983-, et al.
(författare)
-
Empirical Statistical Model for LTE Downlink Channel Occupancy
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- This paper develops an empirical statistical channel occupancy model for downlink long-term evolution (LTE) cellular systems. The model is based on statistical distributions mixtures for the holding times of the channels. Moreover, statistical distribution of the time when the channels are free is also considered. The data is obtained through an extensive measurement campaign performed in Stockholm, Sweden. Two types of mixtures are considered, namely, exponential and log-normal distributions to fit the measurement findings. The log-likelihood of both mixtures is used as a quantitative measure of the goodness of fit. Moreover, finding the optimal number of linearly combined distributions using the Akaike information criterion (AIC) is investigated. The results show that good fitting can be obtained by using either exponential or log-normal distributions mixture. Even though, the fitting is done for a representative case with a tempo-spatial consideration, the model is yet applicable in general for LTE and other cellular systems in a wider sense.
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| 7. |
- Hamid, Mohamed, 1983-, et al.
(författare)
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Energy and Eigenvalue-Based Combined Fully-Blind Self-Adapted Spectrum Sensing Algorithm
- 2015
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Ingår i: IEEE Transactions on Vehicular Technology. - : IEEE. - 0018-9545 .- 1939-9359. ; 65:2, s. 630-642
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, a comparison between energy and maximum-minimum eigenvalue detectors is performed. The comparison has been made concerning the sensing complexity and the sensing accuracy in terms of the receiver operating characteristics curves. The impact of the signal bandwidth compared to the observation bandwidth is studied for each detector. For the energy detector, the probability of detection increases monotonically with the increase of the signal bandwidth. For the maximum-minimum eigenvalue detector, an optimal value of the ratio between the signal bandwidth and the observation bandwidth is found to be $0.5$ when reasonable values of the system dimensionality are used. Based on the comparison findings, a combined two-stage detector is proposed. The combined detector performance is evaluated based on simulations and measurements. The combined detector achieves better sensing accuracy than the two individual detectors with a complexity lies in between the two individual complexities. The combined detector is fully-blind and self-adapted as the maximum-minimum eigenvalue detector estimates the noise and feeds it back to the energy detector. The performance of the noise estimation process is evaluated in terms of the normalized mean square error.
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| 8. |
- Hamid, Mohamed, 1983-, et al.
(författare)
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Geo-location Spectrum Opportunities Database in Downlink Radar Bands for OFDM Based Cognitive Radios
- 2011
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Konferensbidrag (refereegranskat)abstract
- In this paper a model to investigate the spectrum opportunities for cognitive radio networks in three radar frequency bands L, S and C at a specific location is introduced. We consider underlay unaware spectrum sharing model. The Secondary System we assume is an OFDM based system. The followed strategy is built upon defining a specific co or adjacent channel as a spectrum opportunity if -and only if- the interference generated by the secondary system occupying that channel into the radar system is less than the permissible interference defined by the value of Interference to Noise ratio (INR) and the radar receiver inherited noise level. The simulation results show that for the same transmission parameters C band offer more spectrum opportunities than S band which is itself offers more spectrum opportunities than L band.
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| 9. |
- Hamid, Mohamed, 1983-, et al.
(författare)
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Maximum minimum eigenvalues based spectrum scanner for cognitive radios
- 2012
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Ingår i: 2012 IEEE I2MTC - International Instrumentation and Measurement Technology Conference, Proceedings. - New York : IEEE. - 9781457717710 - 9781457717734 ; , s. 2248-2251
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Konferensbidrag (refereegranskat)abstract
- In this paper we introduce a technique for spectrum scanning with the maximum minimum eigenvalue detection based spectrum sensing. The fundamental problem we address in this paper is the inability of using maximum minimum eigenvalue detection with filtering in time domain where the white noise becomes coloured. The solution we propose here is based on frequency domain rectangular filtering. By frequency domain rectangular filtering we take the spectral lines inside each sub-band and throw out the rest. After doing the frequency domain rectangular filtering, we generate the corresponding time domain signal and inject it to the maximum minimum eigenvalue detector. An experimental verification has been performed and the obtained results show that the technique is implementable with a performance better than the energy detector as a reference technique in terms of the probability of detection when both technique have the same probability of false alarm.
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| 10. |
- Hamid, Mohamed, 1983-
(författare)
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On Finding Spectrum Opportunities in Cognitive Radios : Spectrum Sensing and Geo-locations Database
- 2013
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The spectacular growth in wireless services imposes scarcity in term of the available radio spectrum. A solution to overcome this scarcity is to adopt what so called cognitive radio based on dynamic spectrum access. With dynamic spectrum access, secondary (unlicensed) users can access spectrum owned by primary (licensed) users when it is temporally and/or geographically unused. This unused spectrum is termed as spectrum opportunity. Finding these spectrum opportunities related aspects are studied in this thesis where two approaches of finding spectrum opportunities, namely spectrum sensing and geo-locations databases are considered.In spectrum sensing arena, two topics are covered, blind spectrum sensing and sensing time and periodic sensing interval optimization. For blind spectrum sensing, a spectrum scanner based on maximum minimum eigenvalues detector and frequency domain rectangular filtering is developed. The measurements show that the proposed scanner outperforms the energy detector scanner in terms of the probability of detection. Continuing in blind spectrum sensing, a novel blind spectrum sensing technique based on discriminant analysis called spectrum discriminator has been developed in this thesis. Spectrum discriminator has been further developed to peel off multiple primary users with different transmission power from a wideband sensed spectrum. The spectrum discriminator performance is measured and compared with the maximum minimum eigenvalues detector in terms of the probability of false alarm, the probability of detection and the sensing time.For sensing time and periodic sensing interval optimization, a new approach that aims at maximizing the probability of right detection, the transmission efficiency and the captured opportunities is proposed and simulated. The proposed approach optimizes the sensing time and the periodic sensing interval iteratively. Additionally, the periodic sensing intervals for multiple channels are optimized to achieve as low sensing overhead and unexplored opportunities as possible for a multi channels system.The thesis considers radar bands and TV broadcasting bands to adopt geo-locations databases for spectrum opportunities. For radar bands, the possibility of spectrum sharing with secondary users in L, S and C bands is investigated. The simulation results show that band sharing is possible with more spectrum opportunities offered by C band than S and L band which comes as the least one. For the TV broadcasting bands, the thesis treats the power assignment for secondary users operate in Gävle area, Sweden. Furthermore, the interference that the TV transmitter would cause to the secondary users is measured in different locations in the same area.
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