References of "Sharma, Shree Krishna 50003084"
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See detailCompressive Sensing based Target Counting and Localization Exploiting Joint Sparsity
Lagunas, Eva UL; Sharma, Shree Krishna UL; Chatzinotas, Symeon UL et al

in Proc. IEEE ICASSP 2016 (2016, March)

One of the fundamental issues in Wireless Sensor Networks (WSN) is to count and localize multiple targets accurately. In this context, there has been an increasing interest in the literature in using ... [more ▼]

One of the fundamental issues in Wireless Sensor Networks (WSN) is to count and localize multiple targets accurately. In this context, there has been an increasing interest in the literature in using Compressive Sensing (CS) based techniques by exploiting the sparse nature of spatially distributed targets within the monitored area. However, most existing works aim to count and localize the sparse targets utilizing a Single Measurement Vector (SMV) model. In this paper, we consider the problem of counting and localizing multiple targets exploiting the joint sparsity feature of a Multiple Measurement Vector (MMV) model. Furthermore, the conventional MMV formulation in which the same measurement matrix is used for all sensors is not valid any more in practical time-varying wireless environments. To overcome this issue, we reformulate the MMV problem into a conventional SMV in which MMVs are vectorized. Subsequently, we propose a novel reconstruction algorithm which does not need the prior knowledge of the sparsity level unlike the most existing CS-based approaches. Finally, we evaluate the performance of the proposed algorithm and demonstrate the superiority of the proposed MMVapproach over its SMV counterpart in terms of target counting and localization accuracies. [less ▲]

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See detailSensing-Throughput Tradeoff for Interweave Cognitive Radio System: A Deployment-Centric Viewpoint
Kaushik, Ankit UL; Sharma, Shree Krishna UL; Chatzinotas, Symeon UL et al

in IEEE Transactions on Wireless Communications (2016)

Secondary access to the licensed spectrum is viable only if the interference is avoided at the primary system. In this regard, different paradigms have been conceptualized in the existing literature ... [more ▼]

Secondary access to the licensed spectrum is viable only if the interference is avoided at the primary system. In this regard, different paradigms have been conceptualized in the existing literature. Among these, interweave systems (ISs) that employ spectrum sensing have been widely investigated. Baseline models investigated in the literature characterize the performance of the IS in terms of a sensing-throughput tradeoff, however, this characterization assumes perfect knowledge of the involved channels at the secondary transmitter, which is unavailable in practice. Motivated by this fact, we establish a novel approach that incorporates channel estimation in the system model, and consequently investigate the impact of imperfect channel knowledge on the performance of the IS. More particularly, the variation induced in the detection probability affects the detector’s performance at the secondary transmitter, which may result in severe interference at the primary receivers. In this view, we propose to employ average and outage constraints on the detection probability, in order to capture the performance of the IS. Our analysis reveals that with an appropriate choice of the estimation time determined by the proposed approach, the performance degradation of the IS can be effectively controlled, and subsequently the achievable secondary throughput can be significantly enhanced. [less ▲]

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See detailMultiple Access Techniques for Next Generation Wireless: Recent Advances and Future Perspectives
Sharma, Shree Krishna UL; Patwary, Mohammad; Chatzinotas, Symeon UL

in EAI Endorsed Transactions on Wireless Spectrum (2016), 2(7),

The advances in multiple access techniques has been one of the key drivers in moving from one cellular generation to another. Starting from the first generation, several multiple access techniques have ... [more ▼]

The advances in multiple access techniques has been one of the key drivers in moving from one cellular generation to another. Starting from the first generation, several multiple access techniques have been explored in different generations and various emerging multiplexing/multiple access techniques are being investigated for the next generation of cellular networks. In this context, this paper first provides a detailed review on the existing Space Division Multiple Access (SDMA) related works. Subsequently, it highlights the main features and the drawbacks of various existing and emerging multiplexing/multiple access techniques. Finally, we propose a novel concept of clustered orthogonal signature division multiple access for the next generation of cellular networks. The proposed concept envisions to employ joint antenna coding in order to enhance the orthogonality of SDMA beams with the objective of enhancing the spectral efficiency of future cellular networks. [less ▲]

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See detailApplication of Compressive Sensing in Cognitive Radio Communications: A Survey
Sharma, Shree Krishna UL; Lagunas, Eva UL; Chatzinotas, Symeon UL et al

in IEEE COMMUNICATION SURVEYS & TUTORIALS (2016)

Compressive Sensing (CS) has received much attention in several fields such as digital image processing, wireless channel estimation, radar imaging, and Cognitive Radio (CR) communications. Out of these ... [more ▼]

Compressive Sensing (CS) has received much attention in several fields such as digital image processing, wireless channel estimation, radar imaging, and Cognitive Radio (CR) communications. Out of these areas, this survey paper focuses on the application of CS in CR communications. Due to the underutilization of the allocated radio spectrum, spectrum occupancy is usually sparse in different domains such as time, frequency and space. Such a sparse nature of the spectrum occupancy has inspired the application of CS in CR communications. In this regard, several researchers have already applied the CS theory in various settings considering the sparsity in different domains. In this direction, this survey paper provides a detailed review of the state of the art related to the application of CS in CR communications. Starting with the basic principles and the main features of CS, it provides a classification of the main usage areas based on the radio parameter to be acquired by a wideband CR. Subsequently, we review the existing CS-related works applied to different categories such as wideband sensing, signal parameter estimation and Radio Environment Map (REM) construction, highlighting the main benefits and the related issues. Furthermore, we present a generalized framework for constructing the REM in compressive settings. Finally, we conclude this survey paper with some suggested open research challenges and future directions. [less ▲]

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See detailTwo-phase concurrent sensing and transmission scheme for full duplex cognitive radio
Sharma, Shree Krishna UL; Bogale, T.E.; Le, L.B. et al

in IEEE 84th Vehicular Technology Conference (2016)

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See detailImpact of Transceiver Impairments on the Capacity of Dual-Hop Relay Massive MIMO Systems
Papazafeiropoulos, Anastasios; Sharma, Shree Krishna UL; Chatzinotas, Symeon UL

in Proceedings of IEEE Globecom 2015 (2015, December)

Despite the deleterious effect of hardware impairments on communication systems, most prior works have not investigated their impact on widely used relay systems. Most importantly, the application of ... [more ▼]

Despite the deleterious effect of hardware impairments on communication systems, most prior works have not investigated their impact on widely used relay systems. Most importantly, the application of inexpensive transceivers, being prone to hardware impairments, is the most cost-efficient way for the implementation of massive multiple-input multiple-output (MIMO) systems. Consequently, the direction of this paper is towards the investigation of the impact of hardware impairments on MIMO relay networks with large number of antennas. Specifically, we obtain the general expression for the ergodic capacity of dual-hop (DH) amplify-and-forward (AF) relay systems. Next, given the advantages of the free probability (FP) theory with comparison to other known techniques in the area of large random matrix theory, we pursue a large limit analysis in terms of number of antennas and users by shedding light to the behavior of relay systems inflicted by hardware impairments. [less ▲]

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See detailImpact of Terrain Aware Interference Modeling on the Throughput of Cognitive Ka-Band Satellite Systems
Lagunas, Eva UL; Sharma, Shree Krishna UL; Maleki, Sina UL et al

in Ka and Broadband Communications Conference (KaConf), Bologna, Italy, Oct 2015. (2015, October)

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See detailResource Allocation for Cognitive Satellite Communications with Incumbent Terrestrial Networks
Lagunas, Eva UL; Sharma, Shree Krishna UL; Maleki, Sina UL et al

in IEEE Transactions on Cognitive Communications and Networking (2015)

The lack of available unlicensed spectrum together with the increasing spectrum demand by multimedia applications has resulted in a spectrum scarcity problem, which affects Satellite Communications ... [more ▼]

The lack of available unlicensed spectrum together with the increasing spectrum demand by multimedia applications has resulted in a spectrum scarcity problem, which affects Satellite Communications (SatCom) as well as terrestrial systems. The goal of this paper is to propose Resource Allocation (RA) techniques, i.e. carrier, power and bandwidth allocation, for a cognitive spectrum utilization scenario where the satellite system aims at exploiting the spectrum allocated to terrestrial networks as the incumbent users without imposing harmful interference to them. In particular, we focus on the microwave frequency bands 17.7-19.7 GHz for the cognitive satellite downlink and 27.5-29.5 GHz for the cognitive satellite uplink, although the proposed techniques can be easily extended to other bands. In the first case, assuming that the satellite terminals are equipped with multiple Low Block Noise Converters (LNB), we propose a joint beamforming and carrier allocation scheme to enable cognitive Space-to-Earth communications in the shared spectrum where Fixed Service (FS) microwave links have priority of operation. In the second case, however, the cognitive satellite uplink should not cause harmful interference to the incumbent FS system. For the latter, we propose a Joint Power and Carrier Allocation (JPCA) strategy followed by a bandwidth allocation scheme which guarantees protection of the terrestrial FS system while maximizing the satellite total throughput. The proposed cognitive satellite exploitation techniques are validated with numerical simulations considering realistic system parameters. It is shown that the proposed cognitive exploitation framework represents a promising approach for enhancing the throughput of conventional satellite systems. [less ▲]

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See detail3D Beamforming for Spectral Coexistence of Satellite and Terrestrial Networks
Sharma, Shree Krishna UL; Chatzinotas, Symeon UL; Grotz, Joel et al

in IEEE Vehicular Technology Conference 2015 (2015, September)

Satellite communication (SatCom) is facing a spectrum scarcity problem due to the limited available exclusive spectrum and the high demand of the broadband satellite services. In this context, there has ... [more ▼]

Satellite communication (SatCom) is facing a spectrum scarcity problem due to the limited available exclusive spectrum and the high demand of the broadband satellite services. In this context, there has been an increasing interest in the satellite community to exploit the non-exclusive Ka-band spectrum in order to enhance the spectral efficiency of future broadband satellite systems. Herein, we propose a novel concept of enabling the spectral coexistence of satellite and terrestrial networks using three dimensional (3D) beamforming, which exploits the elevation dimension in addition to the commonly used azimuth dimension. The proposed beamforming solution is employed in a Multiple-Input Low Noise Block Downconverter (MLNB) based Feed Array Reflector (FAR) in contrast to the widely used Uniform Linear Array (ULA) structure. Within the employed antenna structure, the performance of the proposed beamforming solution is evaluated considering different feed arrangements. Finally, a database-assisted approach and two blind approaches are suggested for the effective implementation of the proposed solutions. [less ▲]

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See detailImproving Robustness of Cyclostationary Detectors to Cyclic Frequency Mismatch Using Slepian Basis
Sharma, Shree Krishna UL; Bogale, Tadilo Endeshaw; Chatzinotas, Symeon UL et al

in Proceedings of IEEE PIMRC 2015 (2015, September)

Spectrum Sensing (SS) is one of the fundamental mechanisms required by a Cognitive Radio (CR). Among several SS techniques, cyclostationary feature detection is considered as an important technique due to ... [more ▼]

Spectrum Sensing (SS) is one of the fundamental mechanisms required by a Cognitive Radio (CR). Among several SS techniques, cyclostationary feature detection is considered as an important technique due to its robustness against noise variance uncertainty and its capability to distinguish among different systems on the basis of their cyclostationary features. However, one of the main limitations of this detector in practical scenarios is its performance degradation in the presence of cyclic frequency mismatch, which mainly arises due to the lack of knowledge about the transmitter clock/oscillator errors at the detector. In this context, this paper proposes a novel solution to address the cyclic frequency mismatch problem utilizing the Slepian basis expansion instead of the widely used Fourier basis expansion. It is shown that the proposed approach captures the deviation in the cyclic frequency caused by the aforementioned imperfections and hence provides a significant improvement in the sensing performance in the presence of cyclic frequency mismatch. [less ▲]

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See detailPower Control for Satellite Uplink and Terrestrial Fixed-Service Co-existence in Ka-band
Lagunas, Eva UL; Sharma, Shree Krishna UL; Maleki, Sina UL et al

in IEEE Vehicular Technology Conference, Boston 6-9 Sept 2015 (2015, September)

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See detailCognitive Radio Techniques under Practical Imperfections: A Survey
Sharma, Shree Krishna UL; Bogale, Tadilo Endeshaw; Chatzinotas, Symeon UL et al

in IEEE Communications Surveys and Tutorials (2015)

Cognitive Radio (CR) has been considered as a potential candidate for addressing the spectrum scarcity problem of future wireless networks. Since its conception, several researchers, academic institutions ... [more ▼]

Cognitive Radio (CR) has been considered as a potential candidate for addressing the spectrum scarcity problem of future wireless networks. Since its conception, several researchers, academic institutions, industries, regulatory and standardization bodies have put their significant efforts towards the realization of CR technology. However, as this technology adapts its transmission based on the surrounding radio environment, several practical issues may need to be considered. In practice, several imperfections such as noise uncertainty, channel/interference uncertainty, transceiver hardware imperfections, signal uncertainty, synchronization issues, etc. may severely deteriorate the performance of a CR system. To this end, the investigation of realistic solutions towards combating various practical imperfections is very important for successful implementation of the cognitive technology. In this direction, first, this survey paper provides an overview of the enabling techniques for CR communications. Subsequently, it discusses the main imperfections that may occur in the most widely used CR paradigms and then reviews the existing approaches towards addressing these imperfections. Finally, it provides some interesting open research issues. [less ▲]

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See detailRepeater for 5G Wireless: A Complementary Contender for Spectrum Sensing Intelligence
Sharma, Shree Krishna UL; Patwary, Mohammad; Chatzinotas, Symeon UL et al

in Proceedings of International Conference on Communications 2015 (2015, June)

Exploring innovative cellular architectures to achieve enhanced system capacity and good coverage has become a critical issue towards realizing the fifth generation (5G) of wireless communications. In ... [more ▼]

Exploring innovative cellular architectures to achieve enhanced system capacity and good coverage has become a critical issue towards realizing the fifth generation (5G) of wireless communications. In this context, this paper proposes a novel concept of an intelligent Amplify and Forward (AF) 5G repeater for enabling the densification of future cellular networks. The proposed repeater features a Spectrum Sensing (SS) intelligence capability and utilizes such intelligence in a complementary fashion in comparison to its existing counterpart (e.g., Cognitive Radio) by detecting the active channels within the assigned spectrum. This intelligence allows the proposed repeater to carry out selective amplification of the active channels in contrast to the full amplification in conventional AF repeaters. Furthermore, the performance of a Frequency Division Multiple Access (FDMA) based two hop cellular network utilizing the proposed repeater is evaluated in terms of the system throughput. Simulation results demonstrate up to 13 % increase when compared with the conventional repeaters. Moreover, the effect of SS errors on the system capacity is analyzed. [less ▲]

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See detailResource Allocation for Cognitive Satellite Communications in Ka-band (17.7-19.7 GHz)
Sharma, Shree Krishna UL; Lagunas, Eva UL; Maleki, Sina UL et al

in Proceedings of International Conference on Communications (ICC) (2015, June)

In this paper, we consider the problem of resource allocation in the context of cognitive Satellite Communications (SatCom). In particular, we focus on the cognitive downlink access by Geostationary (GEO ... [more ▼]

In this paper, we consider the problem of resource allocation in the context of cognitive Satellite Communications (SatCom). In particular, we focus on the cognitive downlink access by Geostationary (GEO) Fixed Satellite Service (FSS) terminals in the band 17.7-19.7 GHz, where the incumbent users are Fixed-Service (FS) microwave links. Assuming a multiple Low Noise Block Converter (LNB) satellite receiver at the cognitive FSS terminal-side, an efficient receive beamforming technique combined with carrier allocation is proposed in order to maximize the overall downlink throughput as well as to improve the beam availability. The proposed cognitive exploitation framework allows the flexibility of using non-exclusive spectrum for the FSS downlink system, thus improving the overall system throughput. More importantly, the proposed approach is validated with the help of numerical results considering realistic system parameters. [less ▲]

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See detailEstimation-Throughput Tradeoff for Underlay Cognitive Radio Systems
Kaushik, Ankit; Sharma, Shree Krishna UL; Chatzinotas, Symeon UL et al

in Proceedings of International Conference on Communications (ICC) (2015, June)

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See detailJoint Carrier Allocation and Beamforming for Cognitive SatComs in Ka-band (17.3-18.1 GHz)
Sharma, Shree Krishna UL; Maleki, Sina UL; Chatzinotas, Symeon UL et al

in Proceedings of International Conference on Communications (2015, June)

Herein, we study the spectral coexistence of Geostationary (GEO) Fixed Satellite Services (FSS) downlink and Broadcasting Satellite Services (BSS) feeder links in the Ka-band (17.3 − 18.1 GHz) which is ... [more ▼]

Herein, we study the spectral coexistence of Geostationary (GEO) Fixed Satellite Services (FSS) downlink and Broadcasting Satellite Services (BSS) feeder links in the Ka-band (17.3 − 18.1 GHz) which is primarily allocated for BSS feeder links. Firstly, a novel cognitive spectrum exploitation framework is proposed in order to utilize the available band efficiently. Subsequently, based on the interference analysis carried out between these systems, two cognitive approaches, namely Carrier Allocation (CA) and Beamforming (BF), are investigated under the considered framework assuming the availability of an accurate Radio Environment Map (REM). The employed techniques allow the flexibility of using additional shared carriers for the FSS downlink system along with the already available exclusive carriers (19.7 − 20.2 GHz), thus increasing the overall system throughput. It is shown that a significant improvement in the per beam throughput as well as in the beam availability can be achieved by applying CA and BF approaches in the considered scenario. [less ▲]

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See detailCognitive Beamforming for Spectral Coexistence of Hybrid Satellite Systems
Sharma, Shree Krishna UL; Chatzinotas, Symeon UL; Ottersten, Björn UL

in Cooperative and Cognitive Satellite Systems (2015)

In Cognitive Radio (CR) communications, an angular dimension can be considered as an e cient way of exploiting the space dimension in order to enhance the spectral e ciency of an under-utilized primary ... [more ▼]

In Cognitive Radio (CR) communications, an angular dimension can be considered as an e cient way of exploiting the space dimension in order to enhance the spectral e ciency of an under-utilized primary spectrum. In this context, beamforming is an widely considered signal processing solution with the advantages of spatial discrimination and ltering capabilities. Recently, beamforming has received important attention for spectrum sharing purpose in the literature and has been studied for various objectives such as controlling interference, capacity maximization, Signal to Interference plus Noise Ratio (SINR) balancing etc. In this chapter, we provide a detailed overview of the existing beamforming techniques applied in the context of CR networks. Subsequently, we describe Cognitive Beamforming (CB) techniques which can be applicable in the context of cognitive Satellite Communications (SatComs). [less ▲]

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See detailSensing-Throughput Tradeoff for Cognitive Radio Systems with Unknown Received Power
Kaushik, Ankit; Sharma, Shree Krishna UL; Chatzinotas, Symeon UL et al

in Proceedings of CROWNCOM 2015 (2015, April)

Understanding the performance of the cognitive radio systems is of great interest. Different paradigms have been extensively analyzed in the literature to perform secondary access to the licensed spectrum ... [more ▼]

Understanding the performance of the cognitive radio systems is of great interest. Different paradigms have been extensively analyzed in the literature to perform secondary access to the licensed spectrum. Of these, Interweave System (IS) has been widely investigated for performance analysis. According to IS, sensing is employed at the Secondary Transmitter (ST) that protects the Primary Receiver (PR) from the interference induced. Thus, in order to control the interference at the PR, it is required to sustain a certain level of probability of detection. In this regard, ST requires the knowledge of the received power. However, in practice, this knowledge is not available at the ST. Thereby performing analysis considering the prior knowledge of the received power is too idealistic, thus, do not depict the actual performance of the IS. Motivated by this fact, an estimation model that includes received power estimation is proposed. Considering a sensing-throughput tradeoff, we apply this model to characterize the performance of the IS. Most importantly, the proposed model captures the estimation error to determine the distortion in the system performance. Based on analysis, it is illustrated that the ideal model overestimates the performance of the IS. Finally, it is shown that with an appropriate choice of the estimation time, the severity in distortion can be effectively regulated. [less ▲]

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