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See detailCooperative Spectrum Sensing for Heterogeneous Sensor Networks Using Multiple Decision Statistics
Sharma, Shree Krishna UL; Chatzinotas, Symeon UL; Ottersten, Björn UL

in Proceedings of CROWNCOM 2015 (2015, April)

The detection of active Primary Users (PUs) in practical wireless channels with a single Cognitive Radio (CR) sensor is challenging due to several issues such as the hidden node problem, path loss ... [more ▼]

The detection of active Primary Users (PUs) in practical wireless channels with a single Cognitive Radio (CR) sensor is challenging due to several issues such as the hidden node problem, path loss, shadowing, multipath fading, and receiver noise/interference uncertainty. In this context, Cooperative Spectrum Sensing (CSS) is considered a promising technique in order to enhance the overall sensing efficiency. Existing CSS methods mostly focus on homogeneous cooperating nodes considering identical node capabilities, equal number of antennas, equal sampling rate and identical Signal to Noise Ratio (SNR). However, in practice, nodes with different capabilities can be deployed at different stages and are very much likely to be heterogeneous in terms of the aforementioned features. In this context, we study a decision statistics-based centralized CSS which can reduce the signalling burden compared to the one of the sample-based CSS and at the same time achieve the desired level of sensing performance. More specifically, we propose a novel CSS technique based on the joint Probability Distribution Function (PDF) of the multiple decision statistics resulting from different processing capabilities at the sensor nodes and compare its performance with various existing cooperative schemes. Further, we provide a design guideline for the network operators to facilitate decision making while upgrading a sensor network. [less ▲]

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See detailExploiting Polarization for Spectrum Awareness in Cognitive Satellite Communications
Sharma, Shree Krishna UL; Chatzinotas, Symeon UL; Ottersten, Björn UL

in Software-Defined and Cognitive Radio Technologies for Dynamic Spectrum Access and Management (2015)

The continuously increasing demand of spectrum and current static spectrum allocation policies are rendering the available radio spectrum scarce. To address the problem of spectrum scarcity in the ... [more ▼]

The continuously increasing demand of spectrum and current static spectrum allocation policies are rendering the available radio spectrum scarce. To address the problem of spectrum scarcity in the satellite paradigm, cognitive Satellite Communications (SatComs) has been considered as a promising technique. In addition to the existing spectrum sharing dimensions such as frequency, time and space, polarization domain can be exploited as an additional degree of freedom in order to explore the spectral gaps in the under-utilized licensed spectrum. In this context, this chapter firstly provides an overview of the existing works in polarization-based spectrum sharing. Secondly, it presents the theoretical analysis of Energy Detection technique for dual polarized Additive White Gaussian Noise (AWGN) and Rayleigh fading channels considering the spectral coexistence scenarios of dual and hybrid satellite systems. Thirdly, it provides the comparison of different combining techniques in terms of the sensing performance in the considered dual polarized channels with the help of theoretical analysis and numerical results. Finally, it provides interesting future research directions in this domain. [less ▲]

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See detailResource allocation for cognitive satellite uplink and fixed-service terrestrial coexistence in ka-band
Lagunas, E.; Sharma, Shree Krishna UL; Maleki, Sina UL et al

in Lecture Notes of the Institute for Computer Sciences, Social-Informatics and Telecommunications Engineering, LNICST (2015), 156

This paper addresses the cognitive Geostationary Orbit (GSO) satellite uplink where satellite terminals reuse frequency bands of Fixed-Service (FS) terrestrial microwave links which are the incumbent ... [more ▼]

This paper addresses the cognitive Geostationary Orbit (GSO) satellite uplink where satellite terminals reuse frequency bands of Fixed-Service (FS) terrestrial microwave links which are the incumbent users in the Ka 27.5-29.5 GHz band. In the scenario considered herein, the transmitted power of the cognitive satellite user has to ensure that the interference impact on potentially present FS links does not exceed the regulatory interference limitations. In order to satisfy the interference constraint and assuming the existence of a complete and reliable FS database, this paper proposes a Joint Power and Carrier Allocation (JPCA) strategy to enable the cognitive uplink access to GSO Fixed Satellite Service (FSS) terminals. The proposed approach identifies the worst FS link per user in terms of interference and divides the amount of tolerable interference among the maximum number of FSS terminal users that can potentially interfere with it. In so doing, the cognitive system is guaranteed to never exceed the prescribed interference threshold. Subsequently, powers and carriers are jointly allocated so as to maximize the throughput of the FSS system. Supporting results based on numerical simulations are provided. It is shown that the proposed cognitive approach represents a promising solution to significantly boost the performance of conventional satellite systems. © Institute for Computer Sciences, Social Informatics and Telecommunications Engineering 2015. [less ▲]

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See detailPerformance Analysis of Underlay Cognitive Radio Systems: Estimation-Throughput Tradeoff
Kaushik, Ankit UL; Sharma, Shree Krishna UL; Chatzinotas, Symeon UL et al

in arXiv preprint arXiv:1510.03353 (2015)

In this letter, we study the performance of cognitive Underlay Systems (USs) that employ power control mechanism at the Secondary Transmitter (ST). Existing baseline models considered for the performance ... [more ▼]

In this letter, we study the performance of cognitive Underlay Systems (USs) that employ power control mechanism at the Secondary Transmitter (ST). Existing baseline models considered for the performance analysis either assume the knowledge of involved channels at the ST or retrieve this information by means of a feedback channel, however, such situations hardly exist in practice. Motivated by this fact, we propose a novel approach that incorporates the estimation of the involved channels at the ST, in order to characterize the performance of USs under realistic scenarios. Moreover, we apply an outage constraint that captures the impact of imperfect channel knowledge, particularly on the interference power received at the primary receiver. Besides this, we employ a transmit power constraint at the ST to determine an operating regime for the US. Finally, we analyze an interesting tradeoff between the estimation time and the secondary throughput allowing an optimized performance of the US. [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 Wireless Communications, IEEE Transactions on (2015), PP(99), 14

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 detailSpectrum Awareness and Exploitation for Cognitive Satellite Communications
Guidotti, Alessandro; Icolari, Vincenzo; Tarchi, Danielle et al

in European Conference on Networks and Communications (EuCNC), Paris, France, Jun 2015. (2015)

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See detailExtending the Usable Ka Band Spectrum for Satellite Communications: The CoRaSat Project
Evans, Barry; Thompson, Paul; Lagunas, Eva UL et al

in Advanced Next Generation Broadband Satellite Systems Workshop, International Conference on Wireless and Satellite Systems (WiSATS, formerly PSATS), Bradford, UK, July 2015. (2015)

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See detailCognitive interference alignment for spectral coexistence
Sharma, Shree Krishna UL; Chatzinotas, Symeon UL; Ottersten, Björn UL

in Cognitive Radio and Networking for Heterogeneous Wireless Networks (2015)

Interference Alignment (IA) has been widely recognized as a promising interference mitigation technique since it can achieve the optimal degrees of freedom in certain interference limited channels. In the ... [more ▼]

Interference Alignment (IA) has been widely recognized as a promising interference mitigation technique since it can achieve the optimal degrees of freedom in certain interference limited channels. In the context of Cognitive Radio (CR) networks, this technique allows the coexistence of two heterogeneous wireless systems in an underlay cognitive mode. The main concept behind this technique is the alignment of the interference on a signal subspace in such a way that it can be filtered out at the non-intended receiver by sacrificing some signal dimensions. This chapter starts with an overview of IA principle, Degree of Freedom (DoF) concept, and the classification of existing IA techniques. Furthermore, this chapter includes a discussion about IA applications in CR networks.Moreover, a generic system model is presented for allowing the coexistence of two heterogeneous networks using IA approach while relevant precoding and filtering processes are described. In addition, two important practical applications of the IA technique are presented along with the numerical results for underlay spectral coexistence of (i) femtocell-macrocell systems, and (ii) monobeam-multibeam satellite systems. More specifically, an uplink IA scheme is investigated in order to mitigate the interference of femtocell. User Terminals (UTs) towards the macrocell Base Station (BS) in the spatial domain and the interference of multibeam satellite terminals towards themonobeam satellite in the frequency domain. [less ▲]

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See detailInterweave/Underlay Cognitive Radio Techniques and Applications in Satellite Communication Systems
Sharma, Shree Krishna UL

Doctoral thesis (2014)

The demand for precious radio spectrum is continuously increasing while the available radio frequency resource has become scarce due to spectrum segmentation and the dedicated frequency allocation of ... [more ▼]

The demand for precious radio spectrum is continuously increasing while the available radio frequency resource has become scarce due to spectrum segmentation and the dedicated frequency allocation of standardized wireless systems. This scarcity has led to the concept of cognitive radio communication which comprises a variety of techniques capable of allowing the coexistence of licensed and unlicensed systems over the same spectrum. In this context, this thesis focuses on interweave and underlay cognitive radio paradigms which are widely considered as important enablers for realizing cognitive radio technology. In the interweave paradigm, an unlicensed user explores the spectral holes by means of some spectrum awareness methods and utilizes the available spectral availabilities opportunistically while in the underlay paradigm, an unlicensed user is allowed to coexist with the licensed user only if sufficient protection to the licensed user can be guaranteed. Starting with a detailed overview of the existing techniques, this thesis provides contributions in both theoretical and the practical aspects of these paradigms. This thesis is structured into two main parts as described below. One of the important capabilities required for a cognitive radio transceiver is to be able to acquire the knowledge of its surrounding radio environment in order to utilize the available spectral opportunities efficiently. The higher the level of information it can acquire, the better becomes the spectrum utilization. In this context, the first part of this thesis focuses on spectrum awareness techniques such as spectrum sensing, signal to noise ratio estimation and sparsity order estimation which are useful for realizing interweave and underlay based cognitive transceivers as well as a hybrid cognitive transceiver, which overcomes the drawbacks of both the above approaches. The effects of noise and channel correlations, which are often neglected in the existing literature, are considered in our analysis. In the above context, firstly, we propose new sensing thresholds for the eigenvalue based sensing approach using recent results from random matrix theory in order to achieve the improved sensing in correlated scenarios. Then we study the signal to noise ratio estimation problem for both narrowband and wideband transceivers with the help of a detailed theoretical analysis under the signal plus noise hypothesis for a range of correlated scenarios. Subsequently, we study the problem of compressive sparsity order estimation in order to estimate the sparsity order of the carrier occupancy over the wide spectrum using a compressive sensing approach. In addition, we carry out the performance analysis of a hybrid cognitive transceiver which combines the spectrum sensing approach with a power control-based underlay approach. The second part of this thesis introduces the concept of cognitive satellite communications which is a rather unexplored area in the literature despite its significant benefits to both satellite and terrestrial operators. This concept has been motivated due to the limited availability of the satellite spectrum as well as the continuously increasing demand of broadband multimedia, broadcast and interactive satellite services. Subsequently, we study the applications of various cognitive radio techniques in satellite communication systems focusing on the following two scenarios: (i) Hybrid cognitive satellite communication which deals with the spectral coexistence of satellite systems with the terrestrial systems, and (ii) Dual cognitive satellite communication which deals with the spectral coexistence of two satellite systems operating over the same coverage area. Understanding the characteristics of coexisting systems is of great importance while applying a suitable cognitive radio technique. In this context, this thesis exploits the specific characteristics of satellite systems in order to map a suitable cognitive radio technique to a specific scenario. For hybrid cognitive scenarios, we propose the following enabling techniques: (a) Interference modeling, (b) Harmful interference detection, (c) Cognitive beamforming including both transmit and receive beamforming, and (d) Dual-polarized spectrum sensing. Similarly, for dual cognitive scenarios, we propose the following techniques: (i) Cognitive interference alignment, (ii) Cognitive beamhopping, and (iii) Dual-polarized spectrum sensing. Finally, we provide interesting open research issues in the considered domain. [less ▲]

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See detailImplementation Issues of Cognitive Radio Techniques for Ka-band (17.7-19.7 GHZ) SatComs
Sharma, Shree Krishna UL; Maleki, Sina UL; Chatzinotas, Symeon UL et al

in Proceedings of 7th ASMS/13th SPSC (2014, September)

The usable satellite spectrum has become scarce due to continuously increasing demand for broadband multimedia, broadcast and interactive services. In this context, investigating efficient spectrum ... [more ▼]

The usable satellite spectrum has become scarce due to continuously increasing demand for broadband multimedia, broadcast and interactive services. In this context, investigating efficient spectrum coexistence techniques is a crucial challenge in order to enhance the spectral efficiency of future satellite systems. Herein, we study a satellite-terrestrial coexistence scenario where a Fixed Satellite Service (FSS) downlink coexists with the Fixed Service (FS) point to point microwave links in the Ka-band (17.7-19.7 GHz). First, we identify various practical challenges and provide possible solutions in order to allow this coexistence. Then we propose four different sensing and avoidance schemes in order to protect FSS satellite terminals from the harmful FS interference. Further, we evaluate the performance of one of the proposed solutions in the considered scenario with the help of theoretical and numerical analysis. More specifically, we focus on harmful FS detection problem in order to guarantee the sufficient protection of FSS terminals. It is shown that the FS harmful interference can be reliably detected with the help of an additional dipole antenna and this solution further overcomes the noise uncertainty problem encountered while sensing with the satellite dish. [less ▲]

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See detailNew Generation Cooperative and Cognitive Dual Satellite Systems: Performance Evaluation
Sharma, Shree Krishna UL; Christopoulos, Dimitrios UL; Chatzinotas, Symeon UL et al

in Proceedings of 32nd AIAA ICSSC (2014, August)

Investigating innovative satellite architectures with enhanced system through- put is one of the most important challenges towards realizing the next generation of satellite communication systems. In this ... [more ▼]

Investigating innovative satellite architectures with enhanced system through- put is one of the most important challenges towards realizing the next generation of satellite communication systems. In this context, we study two advanced architectures, namely cooperative and cognitive satellite systems. These designs allow the spectral coexistence of two multibeam satellites over a common coverage area with the overlapping beam patterns. In the cooperative dual satellite system, we consider coordination between two coexisting transmitters in order to reduce the intersatellite interference. This is achieved by employing adequate user scheduling, based on the channel state information of each user. To this end, a semi-orthogonal interference aware scheduling algorithm is applied. Further, in the cognitive dual satellite system, we employ a cognitive beamhopping technique assuming that the secondary gateway is aware of the primary's beamhopping pattern. Moreover, we compare the performances of these schemes with those of the conventional multi- beam and overlapping dual satellite systems in terms of spectral efficiency, power efficiency and user fairness. Finally, we provide several insights on the performance of these schemes and provide interesting future works in these domains. [less ▲]

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See detailInline Interference Mitigation Techniques for Spectral Coexistence of GEO and NGEO Satellites
Sharma, Shree Krishna UL; Chatzinotas, Symeon UL; Ottersten, Björn UL

in International Journal of Satellite Communications and Networking (2014)

The interest towards the deployment of Low Earth Orbit (LEO)/Medium Earth Orbit (MEO) satellite systems in several frequency bands is increasing due to the requirement of low latency for real-time systems ... [more ▼]

The interest towards the deployment of Low Earth Orbit (LEO)/Medium Earth Orbit (MEO) satellite systems in several frequency bands is increasing due to the requirement of low latency for real-time systems and high demand of broadband data. When the number of usable Non-Geostationary (NGEO) satellites, that is, LEO/MEO in space, increases, the frequency coexistence between the NGEO satellite systems with the already existing geostationary (GEO) satellite networks becomes a requisite. In this context, it is crucial to explore interference mitigation techniques between GEO and NGEO systems in order to allow their spectral coexistence. More specifically, in the coexistence scenario of GEO and NGEO satellite networks, in-line interference may be a serious problem, especially in the equatorial region. In this paper, we provide several frequency sharing studies in the context of the coexistence of an NGEO satellite link with another NGEO/GEO satellite link. Furthermore, we carry out interference analysis between GEO and MEO satellite systems considering the case of the O3b satellite system and propose an adaptive power control technique for both the uplink and downlink scenarios in order to mitigate the in-line interference. Moreover, we suggest several cognitive solutions for mitigating the in-line interference and provide future research issues. [less ▲]

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See detailCognitive Radio for Ka Band Satellite Communications
Maleki, Sina UL; Chatzinotas, Symeon UL; Sharma, Shree Krishna UL et al

in 32nd AIAA International Communications Satellite Systems Conference, August 2014 (2014, August)

The satellite communication data traffic is increasing dramatically over the coming years. High throughput multibeam satellite networks in Ka band are potentially able to accommodate the upcoming high ... [more ▼]

The satellite communication data traffic is increasing dramatically over the coming years. High throughput multibeam satellite networks in Ka band are potentially able to accommodate the upcoming high data rate demands. However, there is only 500 MHz of exclusive band for download and the same amount for upload. This spectrum shortage impose a barrier in order to satisfy the increasing demands. Cognitive satellite communication in Ka band is considered in this paper in order to potentially provide an additional 4.4 GHz bandwidth for downlink and uplink fixed-satellite-services. In this way, it is expected that the problem of spectrum scarcity for future generation of satellite networks is alleviated to a great extent. The underlying scenarios and enabling techniques are discussed in detail, and finally we investigate the implementation issues related to the considered techniques. [less ▲]

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See detailCompressive Sparsity Order Estimation for Wideband Cognitive Radio Receiver
Sharma, Shree Krishna UL; Chatzinotas, Symeon UL; Ottersten, Björn UL

in Proceedings of IEEE International Conference on Communications (ICC) (2014, June)

Compressive Sensing (CS) has been widely investigated in the Cognitive Radio (CR) literature in order to reduce the hardware cost of sensing wideband signals assuming prior knowledge of the sparsity ... [more ▼]

Compressive Sensing (CS) has been widely investigated in the Cognitive Radio (CR) literature in order to reduce the hardware cost of sensing wideband signals assuming prior knowledge of the sparsity pattern. However, the sparsity order of the channel occupancy is time-varying and the sampling rate of the CS receiver needs to be adjusted based on its value in order to fully exploit the potential of CS-based techniques. In this context, investigating blind Sparsity Order Estimation (SOE) techniques is an open research issue. To address this, we study an eigenvalue based compressive SOE technique using asymptotic Random Matrix Theory. We carry out detailed theoretical analysis for the signal plus noise case to derive the asymptotic eigenvalue probability distribution function (aepdf) of the measured signal’s covariance matrix for sparse signals. Subsequently, based on the derived aepdf expression, we present a technique to estimate the sparsity order of the wideband spectrum with compressive measurements using the maximum eigenvalue of the measured signal’s covariance matrix. The performance of the proposed technique is evaluated in terms of normalized SOE Error (SOEE). It is shown that the sparsity order of the wideband spectrum can be reliably estimated using the proposed technique. [less ▲]

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See detailFP7 PROJECT CoRaSat intermediate results and standardization strategy: Cognitive radio techniques in Ka band SatCom context
Chumberre, Nicolas; Evans, Barry; Vanelli-Coralli, Alessandro et al

in Proc. European Conference on Networks and Communications (EuCNC) (2014, June)

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See detailA Hybrid Cognitive Transceiver Architecture: Sensing-Throughput Tradeoff
Sharma, Shree Krishna UL; Chatzinotas, Symeon UL; Ottersten, Björn UL

in Proceedings of 9th International Conference on Cognitive Radio Oriented Wireless Networks (2014, June)

Spectrum Sensing (SS) and underlay have been considered as two important techniques for enabling the spectral coexistence of the licensed and unlicensed wireless communication systems. The SS only ... [more ▼]

Spectrum Sensing (SS) and underlay have been considered as two important techniques for enabling the spectral coexistence of the licensed and unlicensed wireless communication systems. The SS only approach ignores the interference tolerance capability of the Primary Users (PUs) while assuming the bursty PU traffic whereas the possibility of having secondary transmission with full power is neglected in an underlay based approach. To address this, it’s crucial to investigate suitable hybrid spectrum awareness and transmission strategies which can overcome the aforementioned drawbacks and achieve higher secondary throughput while protecting the PUs. In this context, we propose a hybrid cognitive transceiver which combines the SS approach with the power control based underlay approach. Furthermore, we evaluate the performance of the proposed hybrid approach considering both periodic sensing and simultaneous sensing/transmission schemes. Moreover, sensing-throughput tradeoff for the proposed hybrid approach is investigated and the performance is compared with the conventional SS only approaches in terms of the achievable throughput. It is shown that the proposed scheme can achieve a significant improvement in the secondary throughput over the conventional approaches while respecting the interference constraints of the PUs. [less ▲]

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See detailTechnical Challenges for Cognitive Radio Application in Satellite Communications
Tarchi, Daniele; Guidotti, Alessandro; Icolari, Vincenzo et al

in 9th International Conference on Cognitive Radio Oriented Wireless Networks and Communications (CROWNCOM), 2014 (2014, June)

During the last years, spectrum scarcity has become one of the major issues for the development of new communication systems. Cognitive Radio (CR) approaches have gained an ever increasing attention from ... [more ▼]

During the last years, spectrum scarcity has become one of the major issues for the development of new communication systems. Cognitive Radio (CR) approaches have gained an ever increasing attention from system designers and operators, as they promise a more efficient utilization of the available spectral resources. In this context, while the application of CRs in terrestrial scenarios has been widely considered from both theoretical and practical viewpoints, their exploitation in satellite communications is still a rather unexplored area. In this paper, we address the definition of several satellite communications scenarios, where cognitive radio techniques promise to introduce significant benefits, and we discuss the major enablers and the associated challenges [less ▲]

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See detailMaximum Eigenvalue Detection for Spectrum Sensing Under Correlated Noise
Sharma, Shree Krishna UL; Chatzinotas, Symeon UL; Ottersten, Björn UL

in Proceedings of IEEE International Conference on Acoustics, Speech, and Signal Processing 2014 (2014, May)

Herein, we consider the problem of detecting primary users’ signals in the presence of noise correlation, which may arise due to imperfections in filtering and oversampling operations in a Cognitive Radio ... [more ▼]

Herein, we consider the problem of detecting primary users’ signals in the presence of noise correlation, which may arise due to imperfections in filtering and oversampling operations in a Cognitive Radio (CR) receiver. In this context, we study a Maximum Eigenvalue (ME) detection technique using recent results from Random Matrix Theory (RMT) for characterizing the distribution of the maximum eigenvalue of a class of sample covariance matrices. Subsequently, we derive a theoretical expression for a sensing threshold as a function of the probability of false alarm and evaluate the sensing performance in terms of probability of correct decision. It is shown that the proposed approach significantly improves the sensing performance of the ME detector in correlated noise scenarios. [less ▲]

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See detailCompressive SNR Estimation for Wideband Cognitive Radio under Correlated Scenarios
Sharma, Shree Krishna UL; Chatzinotas, Symeon UL; Ottersten, Björn UL

in Proceedings of IEEE Wireless Communications and Networking Conference (2014, April)

Estimating the Signal to Noise Ratio (SNR) of the Primary Users’ (PUs) signals over a wideband spectrum accurately is crucial in order to fully exploit an under-utilized primary spectrum using underlay ... [more ▼]

Estimating the Signal to Noise Ratio (SNR) of the Primary Users’ (PUs) signals over a wideband spectrum accurately is crucial in order to fully exploit an under-utilized primary spectrum using underlay Cognitive Radio (CR) techniques. In this context, we study an SNR estimation problem for a wideband CR under practical correlated scenarios in compressive settings. We carry out detailed theoretical analysis for the considered scenarios and then derive the expressions for the asymptotic eigenvalue probability distribution function (aepdf) of the measured signal’s covariance matrix using asymptotic Random Matrix Theory. Subsequently, based on the derived aepdfs, we present a technique to estimate the PU SNR over a wideband spectrum with compressive measurements. The performance of the proposed technique is evaluated in terms of normalized Mean Square Error (MSE) and it is shown that the SNR of the PU signals over the wideband spectrum can be reliably estimated using the proposed technique. [less ▲]

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See detailCognitive Beamhopping for Spectral Coexistence of Multibeam Satellites
Sharma, Shree Krishna UL; Chatzinotas, Symeon UL; Ottersten, Björn UL

in International Journal of Satellite Communications and Networking (2014)

Herein, the spectral coexistence scenario of two multibeam satellites over a common coverage area is studied where a primary satellite produces larger beams while a secondary satellite has smaller beams ... [more ▼]

Herein, the spectral coexistence scenario of two multibeam satellites over a common coverage area is studied where a primary satellite produces larger beams while a secondary satellite has smaller beams. A novel cognitive beamhopping satellite system is proposed assuming that the secondary gateway is aware of the primary’s beamhopping pattern. The performance of the proposed system is evaluated and compared with that of conventional multibeam and beamhopping systems in terms of throughput. It is shown that the proposed system significantly enhances the Spectral Efficiency (SE) in comparison to other systems. Furthermore, a power control technique is applied on the secondary transmission in order to adhere to the primary’s interference constraint. It is noted that the total SE increases with the number of secondary users in the full frequency reuse approach. Moreover, the Exclusion Zone (EZ) principle is applied to exploit the regions in which the secondary system can operate without causing harmful interference to the primary system. It is shown that the EZ radius of 8.5 dB is sufficient to protect the primary system perfectly with a significant gain in SE. Finally, it is shown that power control and the EZ methods are suitable for lower and higher values of secondary aggregated interference respectively. [less ▲]

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