The Experts below are selected from a list of 26601 Experts worldwide ranked by ideXlab platform
Bjorn Ottersten - One of the best experts on this subject based on the ideXlab platform.
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massive mimo transmission for leo Satellite Communications
arXiv: Information Theory, 2020Co-Authors: Li You, Jiaheng Wang, Xiqi Gao, Xianggen Xia, Bjorn OtterstenAbstract:Low earth orbit (LEO) Satellite Communications are expected to be incorporated in future wireless networks, in particular 5G and beyond networks, to provide global wireless access with enhanced data rates. Massive MIMO techniques, though widely used in terrestrial communication systems, have not been applied to LEO Satellite communication systems. In this paper, we propose a massive MIMO transmission scheme with full frequency reuse (FFR) for LEO Satellite communication systems and exploit statistical channel state information (sCSI) to address the difficulty of obtaining instantaneous CSI (iCSI) at the transmitter. We first establish the massive MIMO channel model for LEO Satellite Communications and simplify the transmission designs via performing Doppler and delay compensations at user terminals (UTs). Then, we develop the low-complexity sCSI based downlink (DL) precoder and uplink (UL) receiver in closed-form, aiming to maximize the average signal-to-leakage-plus-noise ratio (ASLNR) and the average signal-to-interference-plus-noise ratio (ASINR), respectively. It is shown that the DL ASLNRs and UL ASINRs of all UTs reach their upper bounds under some channel condition. Motivated by this, we propose a space angle based user grouping (SAUG) algorithm to schedule the served UTs into different groups, where each group of UTs use the same time and frequency resource. The proposed algorithm is asymptotically optimal in the sense that the lower and upper bounds of the achievable rate coincide when the number of Satellite antennas or UT groups is sufficiently large. Numerical results demonstrate that the proposed massive MIMO transmission scheme with FFR significantly enhances the data rate of LEO Satellite communication systems. Notably, the proposed sCSI based precoder and receiver achieve the similar performance with the iCSI based ones that are often infeasible in practice.
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multicast multigroup precoding for frame based multi gateway Satellite Communications
2016 8th Advanced Satellite Multimedia Systems Conference and the 14th Signal Processing for Space Communications Workshop (ASMS SPSC), 2016Co-Authors: Dimitrios Christopoulos, Symeon Chatzinotas, Harri Pennanen, Bjorn OtterstenAbstract:The present work focuses on the forward link of fixed multibeam broadband Satellite systems which employ aggressive frequency reuse patterns in the user-link. For such scenarios, the state-of-the art frame based precoding methods can improve the system performance, exploiting the super framing structure of the latest physical layer evolutions in Satellite Communications. Nevertheless, the limitations of feeder link need to be considered. Since the increase of the user link capacity leads to a proportional increase in the capacity requirements of the point-to-point feeder link, the deployment of multiple gateways to feed the Satellite is examined. The main concept lies in each earth station being dedicated to serve a cluster of beams. In this context, the performance degradation due to inter-cluster interference is quantified. Since inter-cluster interference is expected to primarily affect cluster-edge users, the chosen performance metric is system fairness. Next, coordination between the multiple gateways is proposed as a means to mitigate interference between the different clusters and thus increase the minimum SINR over the coverage. Consequently, the gains in terms of system availability, a crucial metric in Satellite Communications, are exhibited via numerical system level simulations. The energy efficiency of the proposed system is also presented.
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resource allocation for cognitive Satellite Communications in ka band 17 7 19 7 ghz
International Conference on Communications, 2015Co-Authors: Shree Krishna Sharma, Eva Lagunas, Sina Maleki, Symeon Chatzinotas, Joel Grotz, Jens Krause, Bjorn OtterstenAbstract: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.
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Resource Allocation for Cognitive Satellite Communications With Incumbent Terrestrial Networks
IEEE Transactions on Cognitive Communications and Networking, 2015Co-Authors: Eva Lagunas, Shree Krishna Sharma, Sina Maleki, Symeon Chatzinotas, Bjorn OtterstenAbstract: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.
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Massive MIMO Transmission for LEO Satellite Communications
IEEE Journal on Selected Areas in Communications, 2024Co-Authors: Ke-xin Li, Jiaheng Wang, Bjorn OtterstenAbstract:Low earth orbit (LEO) Satellite Communications are expected to be incorporated in future wireless networks, in particular 5G and beyond networks, to provide global wireless access with enhanced data rates. Massive multiple-input multipleoutput (MIMO) techniques, though widely used in terrestrial communication systems, have not been applied to LEO Satellite communication systems. In this paper, we propose a massive MIMO transmission scheme with full frequency reuse (FFR) for LEO Satellite communication systems and exploit statistical channel state information (sCSI) to address the difficulty of obtaining instantaneous CSI (iCSI) at the transmitter. We first establish the massive MIMO channel model for LEO Satellite Communications and simplify the transmission designs via performing Doppler and delay compensations at user terminals (UTs). Then, we develop the low-complexity sCSI based downlink (DL) precoder and uplink (UL) receiver in closed-form, aiming to maximize the average signal-to-leakage-plus-noise ratio (ASLNR) and the average signal-to-interference-plus-noise ratio (ASINR), respectively. It is shown that the DL ASLNRs and UL ASINRs of all UTs reach their upper bounds under some channel condition. Motivated by this, we propose a space angle based user grouping (SAUG) algorithm to schedule the served UTs into different groups, where each group of UTs use the same time and frequency resource. The proposed algorithm is asymptotically optimal in the sense that the lower and upper bounds of the achievable rate coincide when the number of Satellite antennas or UT groups is sufficiently large. Numerical results demonstrate that the proposed massive MIMO transmission scheme with FFR significantly enhances the data rate of LEO Satellite communication systems. Notably, the proposed sCSI based precoder and receiver achieve the similar performance with the iCSI based ones that are often infeasible in practice.
Xuexia Yang - One of the best experts on this subject based on the ideXlab platform.
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dual band circularly polarized shared aperture array for c x band Satellite Communications
IEEE Transactions on Antennas and Propagation, 2017Co-Authors: Chunxu Mao, Steven Gao, Yi Wang, Qingxin Chu, Xuexia YangAbstract:A novel method of achieving a single-feed circularly polarized (CP) microstrip antenna with both broad impedance bandwidth and axial ratio (AR) bandwidth is presented. The CP characteristics are generated by employing a resonator to excite the two orthogonal modes of the patch via two coupling paths and the required 90° phase difference is achieved by using the different orders of the two paths. The presented method, instead of conventional methods that power dividers and phase delay lines are usually required, not only significantly enhances the bandwidths of the antenna but also results in a compact feed, reduced loss and high gain. Based on this method, a dual-band shared-aperture CP array antenna is implemented for $C$ -/ $X$ -band Satellite Communications. The antenna aperture includes a $2 \times 2$ array at $C$ -band and a $4 \times 4$ array at $X$ -band. To accommodate the $C$ - $X$ -band elements into the same aperture while achieving a good isolation between them, the $C$ -band circular patches are etched at the four corners. The measured results agree well with the simulations, showing a wide impedance bandwidth of 21% and 21.2% at $C$ -band and $X$ -band, respectively. The $C$ -band and $X$ -band 3 dB AR bandwidths are 13.2% and 12.8%. The array also exhibits a high aperture efficiency of over 55%, low sidelobe ( $C$ -band: −12.5 dB and $X$ -band: −15 dB), and high gain ( $C$ -band: 14.5 dBic and $X$ -band: 17.5 dBic).
Nelson J G Fonseca - One of the best experts on this subject based on the ideXlab platform.
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dual band dual linear to circular polarization converter in transmission mode application to k ka band Satellite Communications
IEEE Transactions on Antennas and Propagation, 2018Co-Authors: Parinaz Naseri, Sergio A Matos, Jorge R Costa, Carlos A Fernandes, Nelson J G FonsecaAbstract:Many wireless communication applications such as Satellite Communications use circularly polarized (CP) signals, with the requirement for easy switching of the polarization sense between uplink and downlink. Specifically, in Satellite Communications, the trend is also to move to higher frequencies and integrate the receiving and transmitting antennas in one dual-band terminal. However, these simultaneous demands make the design and fabrication of the composing parts very challenging. We propose, here, a dual-band dual-linear polarization (LP)-to-CP converter that works in the transmission mode. The working principle of this polarizer is explained through an example for Ka-band Satellite Communications at 19.7–20.2 and 29.5–30 GHz. The LP-to-CP converter is a single panel composed of identical unit cells with a thickness of only 1.05 mm and a size of 5.3 mm $\times5.3$ mm. Due to its operation in the transmission mode, the polarizer can be combined with a simple dual-band dual-LP antenna to obtain the desired dual-band dual-CP single antenna. However, the unique property of this polarizer is yet the fact that it converts a given LP wave, e.g., x-polarization, to orthogonal CP waves at the two nonadjacent frequency bands, e.g., left-handed CP at lower band and right-handed CP at higher band. The polarizer is tested both with 20 and 30 GHz LP rectangular horns to illuminate a dual-band transmit array (TA) to obtain wide-angle steering of CP beams. The performance of the polarizer and its association with the TA is evaluated through simulation and measurements. We also present design guidelines for this type of polarizer.
B G Evans - One of the best experts on this subject based on the ideXlab platform.
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technical challenges for cognitive radio application in Satellite Communications
International Conference on Cognitive Radio Oriented Wireless Networks and Communications, 2014Co-Authors: Daniele Tarchi, Vincenzo Icolari, Alessandro Guidotti, Alessandro Vanellicoralli, Shree Krishna Sharma, Sina Maleki, Symeon Chatzinotas, B G Evans, Paul Thompson, Wuchen TangAbstract: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.
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satnex a european network of excellence in Satellite Communications
International Journal of Satellite Communications and Networking, 2005Co-Authors: B G EvansAbstract:Satellite Communications represents a specialised area of teleCommunications. While the development of Satellite technology is relatively slow in comparison to wireless networks evolution, due to the need for high reliability, the services that Satellites are able to offer are evolving at much the same pace as their terrestrial counterparts. It is within this context that the Satellite Communications Network of Excellence (SatNEx) has evolved its initiative, the aim being to serve the engineering community with the latest technological trends, while also providing a solid grounding in the fundamentals for those new to the subject area.
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satnex the european Satellite Communications network of excellence air interface activities
2005Co-Authors: Michel Bousquet, Laurent Castanet, Giovanni Giambene, G E Corazza, Erina Ferro, Erich Lutz, Anton Donner, B G Evans, Gerard Maral, Robert RumeauAbstract:The SatNEx project has brought together twenty-two partners from European research organisations and academia to form a pan-European research network. A major objective of SatNEx is to rectify the fragmentation in Satellite Communications research by bringing together leading European academic research organisations in a durable way. Furthermore, the Network aims to establish critical mass and allow access to a range of expertise currently distributed across Europe. In this respect, mobility is an important aspect of SatNEx’s work, with academic staff and research students being encouraged to move between institutions to allow access to specialised research equipment and to facilitate research integration. Training represents an important part of SatNEx’s remit and is supported through a number of initiatives including the hosting of internship projects, the establishment of summer schools and the dissemination of papers of a tutorial nature This paper discusses the background and motivation for implementation of the network and highlights the SatNEx mission and key objectives. A top-level overview is provided including a description of the consortium and the Joint Programme of Activities (JPA). Details of the activities carried out under the Work Package 2400 “Access”, dealing with the Air Interface system components (physical and access layers) are provided.
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removing barriers integrating research spreading excellence the european Satellite Communications network of excellence satnex
Broadband Satellite Comunication Systems, 2004Co-Authors: M Werner, Michel Bousquet, G E Corazza, Erich Lutz, Robert Rumeau, Anton Donner, B G Evans, Gerard Maral, Fun Y Hu, Ray E SheriffAbstract:Within the recently launched 6th research framework programme of the European Commission, 21 major players in Satellite Communications research have joined forces to implement the European Satellite Communications network of excellence (SatNEx). The primary goal of SatNEx is to achieve long-lasting integration of the European research in Satellite communication. This paper discusses the motivation for implementation of the network and highlights the SatNEx mission and key objectives. A top-level overview is provided including a description of the consortium and the joint programme of activities (JPA). Finally, an update of ongoing work is presented.
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satnex the european Satellite Communications network of excellence
Vehicular Technology Conference, 2004Co-Authors: M Werner, Michel Bousquet, Erich Lutz, Robert Rumeau, Anton Donner, Gerard Maral, Ray E Sheriff, F Hu, Hartmut Brandt, B G EvansAbstract:Summary form only given. This paper outlines the primary goal of SatNEx which is to achieve long-lasting integration of the European research in Satellite Communications and to develop a common base of knowledge. Networks of excellence have been introduced as a new instrument within the 6/sup th/ IST framework program, and SatNEx is one of the first consortia to implement the new ideas and to overcome the fragmentation of European research. Through co-operation of outstanding universities and research organizations with excellent expertise in Satellite Communications, SatNEx will build a European virtual centre of excellence in Satellite Communications and contribute to the realization of the European Research Area (ERA) SatNEx will include an advisory board incorporating representatives of the European space industry, Satellite service providers, and standardization and regulation organizations. SatNEx will collaborate with these players and put together a critical mass of resources and expertise needed for making Europe a world force in the field of Satellite Communications.
Ke-xin Li - One of the best experts on this subject based on the ideXlab platform.
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Massive MIMO Transmission for LEO Satellite Communications
IEEE Journal on Selected Areas in Communications, 2024Co-Authors: Ke-xin Li, Jiaheng Wang, Bjorn OtterstenAbstract:Low earth orbit (LEO) Satellite Communications are expected to be incorporated in future wireless networks, in particular 5G and beyond networks, to provide global wireless access with enhanced data rates. Massive multiple-input multipleoutput (MIMO) techniques, though widely used in terrestrial communication systems, have not been applied to LEO Satellite communication systems. In this paper, we propose a massive MIMO transmission scheme with full frequency reuse (FFR) for LEO Satellite communication systems and exploit statistical channel state information (sCSI) to address the difficulty of obtaining instantaneous CSI (iCSI) at the transmitter. We first establish the massive MIMO channel model for LEO Satellite Communications and simplify the transmission designs via performing Doppler and delay compensations at user terminals (UTs). Then, we develop the low-complexity sCSI based downlink (DL) precoder and uplink (UL) receiver in closed-form, aiming to maximize the average signal-to-leakage-plus-noise ratio (ASLNR) and the average signal-to-interference-plus-noise ratio (ASINR), respectively. It is shown that the DL ASLNRs and UL ASINRs of all UTs reach their upper bounds under some channel condition. Motivated by this, we propose a space angle based user grouping (SAUG) algorithm to schedule the served UTs into different groups, where each group of UTs use the same time and frequency resource. The proposed algorithm is asymptotically optimal in the sense that the lower and upper bounds of the achievable rate coincide when the number of Satellite antennas or UT groups is sufficiently large. Numerical results demonstrate that the proposed massive MIMO transmission scheme with FFR significantly enhances the data rate of LEO Satellite communication systems. Notably, the proposed sCSI based precoder and receiver achieve the similar performance with the iCSI based ones that are often infeasible in practice.
