Impact of Terrain Aware Interference Modeling on the Throughput of Cognitive Ka-Band Satellite Systems

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

3D Beamforming for Spectral Coexistence of Satellite and Terrestrial Networks

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 ▲]

Resource Allocation for Cognitive Satellite Communications with Incumbent Terrestrial Networks

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 ▲]

Resource Allocation for Cognitive Satellite Communications in Ka-band (17.7-19.7 GHz)

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 ▲]

Joint Carrier Allocation and Beamforming for Cognitive SatComs in Ka-band (17.3-18.1 GHz)

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 ▲]

Cognitive Beamforming for Spectral Coexistence of Hybrid Satellite Systems

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 ▲]

Cooperative Spectrum Sensing for Heterogeneous Sensor Networks Using Multiple Decision Statistics

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 ▲]

Exploiting Polarization for Spectrum Awareness in Cognitive Satellite Communications

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 ▲]

Extending the Usable Ka Band Spectrum for Satellite Communications: The CoRaSat Project

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

Performance Analysis of Underlay Cognitive Radio Systems: Estimation-Throughput Tradeoff

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 ▲]