References of "Shankar, Bhavani 50002712"
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See detailPerformance Analysis of Fractionally Spaced Equalization in Non-linear Multicarrier Satellite Channels
Piazza, Roberto UL; Shankar, Bhavani UL; Berheide, Tobias et al

in Proceedings of 32nd AIAA International Communications Satellite Systems Conference (ICSSC), (2014, August 05)

Joint amplification of multiple carriers with a single wideband high power amplifier (HPA) has been considered towards reusing the satellite resources among multiple links to reduce the mission cost. The ... [more ▼]

Joint amplification of multiple carriers with a single wideband high power amplifier (HPA) has been considered towards reusing the satellite resources among multiple links to reduce the mission cost. The non-linear characteristic of the HPA, especially near saturation, coupled with the on-board IMUX/ OMUX filters result in non-linear adjacent carrier interference (ACI) and inter-symbol interference (ISI) during multicarrier power amplification. To benefit from the advantages of multicarrier transmissions, on-ground techniques to mitigate the non-linear distortions need to be devised. These techniques include predistortion at the transmitter and equalization at the receiver. Several works have considered the use of multicarrier predistortion along with single carrier equalization. A symbol synchronous equalizer, while being simple to implement, may not necessarily provide for the optimum linear filter. Towards improving the performance, fractionally spaced equalizers (FSE) have been considered. Such receivers are shown to provide enhanced performance by effectively compensating for the group delay distortions. The objective of this work is to consider the use of FSE in the context of multicarrier transmissions over non-linear channels and illustrate their performance enhancements [less ▲]

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See detailApplicability of MIMO to satellite communications
Kyrolainen, Jukka; Hulkonnen, Ari; Juha, Ylitalo et al

in International Journal of Satellite Communications and Networking (2014)

This paper presents achievements of an on-going activity where the applicability of MIMO to satellite communications with Digital Video Broadcasting – Satellite services to Handhelds as the key ... [more ▼]

This paper presents achievements of an on-going activity where the applicability of MIMO to satellite communications with Digital Video Broadcasting – Satellite services to Handhelds as the key application is studied. The potential satellite and hybrid satellite-terrestrial MIMO scenarios are described, and the applicable MIMO schemes for each scenario are selected. The performance of the MIMO schemes was studied by performing comprehensive computer simulations, and the main results are presented in this paper. [less ▲]

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See detailMulticarrier LUT-based data predistortion for non-linear satellite channels
Piazza, Roberto UL; Shankar, Bhavani UL; Ottersten, Björn UL

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

Current satellite communication architectures can be potentially improved by applying multicarrier power amplification. Joint on-board amplification of multiple carriers reduces hardware and weight ... [more ▼]

Current satellite communication architectures can be potentially improved by applying multicarrier power amplification. Joint on-board amplification of multiple carriers reduces hardware and weight, enabling cost-efficient satellite architectures. However, on board power amplification is inherently a non-linear operation, whose distortion effects drastically increase when the high power amplifier (HPA) is operated in multiple carrier mode due to the generated inter-modulation products. In order to achieve the desired on-board power efficiency and to reduce the non-linear distortion, specific countermeasures need to be put in place. In this work we provide a novel data predistortion technique for multiple carriers satellite channel based on look up table (LUT) for high throughput applications. In contrast to known single carrier LUT techniques, the entries of the table are obtained by pursuing an analytical approach exploiting channel model and implementing recursive least squares techniques (RLS). A novel method to reduce the number of LUT entries based on LUT partitioning is proposed. Considerable performance gains over standard polynomial based predistortion are realized by the proposed technique. [less ▲]

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See detailEnhanced List-Based Group-Wise Overloaded Receiver with Application to Satellite Reception
Abu Shaban, Zohair UL; Shankar, Bhavani UL; Mehrpoyan, Hani et al

in Proceedings of IEEE ICC 2014 (2014, June)

The market trends towards the use of smaller dish antennas for TV satellite receivers, as well as the growing density of broadcasting satellites in orbit require the application of robust adjacent ... [more ▼]

The market trends towards the use of smaller dish antennas for TV satellite receivers, as well as the growing density of broadcasting satellites in orbit require the application of robust adjacent satellite interference (ASI) cancellation algorithms at the receivers. The wider beamwidth of a small size dish and the growing number of satellites in orbit impose an overloaded scenario, i.e., a scenario where the number of transmitting satellites exceeds the number of receiving antennas. For such a scenario, we present a two stage receiver to enhance signal detection from the satellite of interest, i.e., the satellite that the dish is pointing to, while reducing interference from neighboring satellites. Towards this objective, we propose an enhanced List-based Group-wise Search Detection (LGSD) receiver architecture that takes into account the spatially correlated additive noise and uses the signal-to-interference-plus-noise ratio (SINR) maximization criterion to improve detection performance. Simulations show that the proposed receiver structure enhances the performance of satellite systems in the presence of ASI when compared to existing methods. [less ▲]

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See detailCarrier Rate Optimization on the Return Link of Interactive Mobile Satellite Networks
Piazza, Roberto UL; Shankar, Bhavani UL; Ottersten, Björn UL

in European Wireless 2014; 20th European Wireless Conference; Proceedings of (2014, May)

Emerging interactive satellite applications demand highly efficient transmission schemes. Narrow-band satellite return channels for mobile users have peculiar characteristics that make the optimal user ... [more ▼]

Emerging interactive satellite applications demand highly efficient transmission schemes. Narrow-band satellite return channels for mobile users have peculiar characteristics that make the optimal user-rate determination a hard problem. Carrier rate enhancement can only be enabled by increasing the user bandwidth and by the application of highly efficient coding schemes. However, with the system bandwidth held constant, gains from increased user bandwidth can be offset by interference from an adjacent user channels. Additional interference is caused by spurious emissions from adjacent channels; these arise from the spectral regrowth caused by the user terminal power amplifier when operated in high-efficiency region. On the other hand, efficient amplification is mandatory to achieve the required signal to noise ratio at the receiver. In this work we propose a combination of transmitter and receiver techniques to improve the user-rate while controlling the user power efficiency. [less ▲]

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See detailEffect of imperfect channel estimate on the performance of MMSE receivers in multibeam satellite systems: First order analysis
Shankar, Bhavani UL; Ottersten, Björn UL

in Electronics, Computing and Communication Technologies (IEEE CONECCT), 2014 IEEE International Conference on (2014, January)

Aggressive frequency reuse in a multibeam satellite system offers wider bandwidths per beam at the cost of increased co-channel interference. Focussing on the return link of interactive mobile satellite ... [more ▼]

Aggressive frequency reuse in a multibeam satellite system offers wider bandwidths per beam at the cost of increased co-channel interference. Focussing on the return link of interactive mobile satellite systems, emphasis has been laid on Minimum Mean Squared Error (MMSE) receivers at the gateway to reduce the co-channel interference arising out of aggressive reuse. Performance of such receivers have been evaluated in presence of perfect channel information and synchronization showing impressive gains in throughput. Towards bringing such receivers closer to system implementation, this work aims at understanding the effect of imperfect channel estimates on the resulting performance. In particular, utilizing first order approximations, closed-form expressions for the MMSE receiver and the resulting Mean Squared Error (MSE) have been derived. These expressions provide insight into the effect of channel, noise levels and the estimation error on performance while indicating the robustness of MMSE receiver. [less ▲]

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See detailTiming and Frequency Synchronisation for Multiuser Detection on the Return Link of Interactive Mobile Satellite Networks
Abu Shaban, Zohair UL; Shankar, Bhavani UL; Christopoulos, Dimitrios UL et al

in Proceedings of the ICSSC conferrence (2013, October)

Synchronization, a key process in a communication system, can be very demanding, especially in burst mode transmissions. The estimation of timing, frequency and phase offsets is sensitive to the magnitude ... [more ▼]

Synchronization, a key process in a communication system, can be very demanding, especially in burst mode transmissions. The estimation of timing, frequency and phase offsets is sensitive to the magnitude of these offsets as well as the ambient interference and noise levels. The aggressive reuse of frequencies in a multibeam satellite system increases the co-channel interference significantly and motivates the need to revisit, and re-design if needed, the algorithms used for synchronization. This paper deals with such a scenario occurring on the return link of a mobile interactive satellite system and provides a set of synchronization sub-systems that allow for the design of a robust modem that can reap the benefits of sophisticated interference mitigation techniques. [less ▲]

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See detailLarge Scale Transmit Diversity in Q/V Band Feeder Link with Multiple Gateways
Gharanjik, Ahmad UL; Shankar, Bhavani UL; Arapoglou, Pantelis-Daniel UL

in Proceeding of IEEE 24th International Symposium on Personal, Indoor, and Mobile Radio Communication(PIMRC) (2013, September 08)

Exploiting transmit diversity amid a high number of multiple gateways (GW) is a new research challenge in Q/V band satellite communication providing data rates of hundreds of Gbit/s. In this paper, we ... [more ▼]

Exploiting transmit diversity amid a high number of multiple gateways (GW) is a new research challenge in Q/V band satellite communication providing data rates of hundreds of Gbit/s. In this paper, we propose a practical switching strategy in a scenario with N +P GWs (N active and P redundant GWs) towards achieving GW transmit diversity. Differently from other works, the treatment in this paper is analytical and explores two key factors: outage performance and switching rate in detail. Further, the interplay between the number of redundant and active GWs on the availability is illustrated highlighting the contribution of the work towards system sizing. [less ▲]

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See detailGateway Switching in Q/V Band Satellite Feeder Links
Gharanjik, Ahmad UL; Shankar, Bhavani UL; Arapoglou, Pantelis-Daniel UL et al

in IEEE Communications Letters (2013), 17(7), 1384-1387

A main challenge towards realizing the next generation Terabit/s broadband satellite communications (SatCom) is the limited spectrum available in the Ka band. An attractive solution is to move the feeder ... [more ▼]

A main challenge towards realizing the next generation Terabit/s broadband satellite communications (SatCom) is the limited spectrum available in the Ka band. An attractive solution is to move the feeder link to the higher Q/V band, where more spectrum is available. When utilizing the Q/V band, due to heavy rain attenuation, gateway diversity is considered a necessity to ensure the required feeder link availability. Although receive site diversity has been studied in the past for SatCom, there is much less maturity in terms of transmit diversity techniques. In this paper, a modified switch and stay combining scheme is proposed for a Q/V band feeder link, but its performance is also evaluated over an end-to-end satellite link. The proposed scheme is pragmatic and has close to optimal performance with notably lower complexity. [less ▲]

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See detailGateway Diversity Strategies in Q/V Band Feeder Links
Arapoglou, Pantelis-Daniel UL; Shankar, Bhavani UL; Panagopoulos, Athanasios et al

in Gateway Diversity Strategies in Q/V Band Feeder Links (2013, July)

A main challenge towards realizing the next generation Terabit/s broadband satellite communications (SatCom) is the limited spectrum available in the Ka band. An attractive solution is to move the feeder ... [more ▼]

A main challenge towards realizing the next generation Terabit/s broadband satellite communications (SatCom) is the limited spectrum available in the Ka band. An attractive solution is to move the feeder link to the higher Q/V band, where more spectrum is available. When utilizing the Q/V band, due to heavy rain attenuation, gateway diversity is considered a necessity to ensure the required feeder link availability. Although receive site diversity has been studied in the past for SatCom, there is much less maturity in terms of transmit diversity techniques. In this paper, a modified switch and stay combining scheme is proposed for a Q/V band feeder link, but its performance is also evaluated over an end-to-end satellite link. The proposed scheme is pragmatic and has close to optimal performance with notably lower complexity. [less ▲]

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See detailData Predistortion for Multicarrier Satellite Channels using Orthogonal Memory polynomials
Piazza, Roberto UL; Shankar, Bhavani UL; Ottersten, Björn UL

in International Workshop on Signal Processing Advances for Wireless Communications (2013) (2013, June 16)

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See detailNon-parametric data predistortion for non-linear channels with memory
Piazza, Roberto UL; Shankar, Bhavani UL; Ottersten, Björn UL

in Acoustics, Speech and Signal Processing (ICASSP), 2013 IEEE International Conference on (2013, May 26)

With the growing application of high order modulation techniques, the mitigation of the non-linear distortions introduced by the power amplification, has become a major issue in telecommunication. More ... [more ▼]

With the growing application of high order modulation techniques, the mitigation of the non-linear distortions introduced by the power amplification, has become a major issue in telecommunication. More sophisticated techniques to counteract the strong generated interferences need to be investigated in order to achieve the desired power and spectral efficiency. This work proposes a novel approach for the definition of a transmitter technique (predistortion) that outperforms the standard methods with respect to both performance and efficiency. [less ▲]

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See detailSensitivity Analysis of Multicarrier Digital Pre-distortion/ Equalization Techniques for Non-linear Satellite Channels
Piazza, Roberto UL; Shankar, Bhavani UL; Zenteno, Efrain et al

in Proceedings of 31st AIAA International Communications Satellite Systems Conference (ICSSC), (2013)

On-board joint power amplification of multiple-carrier DVB-S2 signals using a single High-Power Amplifier (HPA) is an emerging configuration that aims to reduce flight hardware and weight. However ... [more ▼]

On-board joint power amplification of multiple-carrier DVB-S2 signals using a single High-Power Amplifier (HPA) is an emerging configuration that aims to reduce flight hardware and weight. However, effects specific to such a scenario degrade power and spectral efficiencies with increased Adjacent Channel Interference caused by non-linear characteristic of the HPA and power efficiency loss due to the increased Peak to Average Power Ratio (PAPR). The paper studies signal processing techniques that counteract for both aspects enabling efficient multicarrier on board amplification. Digital pre-distortion (DPD) at the gateway and equalization (EQ) at the User Terminal are the designed avenues of attack to mitigate the non-linear effects and improve power as well as spectral efficiencies. This paper builds on our initial work in Ref.1 that performed a survey on the adaptability of various compensation techniques to the considered scenario and short-listed the most favourable ones. Preliminary performance analysis of these techniques was undertaken with Signal to Interference Ratio (SINR) as the figure of merit. The contribution of this work over Ref. 1 includes : (a) a full DVB-S2 chain is simulated with the chosen techniques with Total Degradation (TD) as the figure of merit and (b) a sensitivity analysis is performed to study the dependence of the pre-distortion/ equalization performance ( measured as TD) on the channel parameters. [less ▲]

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See detailLarge scale transmit diversity in Q/V band feeder link with multiple gateways
Gharanjik, Ahmad; Shankar, Bhavani UL; Arapoglou et al

in Personal Indoor and Mobile Radio Communications (PIMRC), 2013 IEEE 24th International Symposium on (2013)

Exploiting transmit diversity amid a high number of multiple gateways (GW) is a new research challenge in Q/V band satellite communication providing data rates of hundreds of Gbit/s. In this paper, we ... [more ▼]

Exploiting transmit diversity amid a high number of multiple gateways (GW) is a new research challenge in Q/V band satellite communication providing data rates of hundreds of Gbit/s. In this paper, we propose a practical switching strategy in a scenario with N+P GWs (N active and P redundant GWs) towards achieving GW transmit diversity. Differently from other works, the treatment in this paper is analytical and explores two key factors: outage performance and switching rate in detail. Further, the interplay between the number of redundant and active GWs on the availability is illustrated highlighting the contribution of the work towards system sizing. [less ▲]

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See detailSpace-Frequency Coding for Dual Polarized Hybrid Mobile Satellite Systems
Shankar, Bhavani UL; Arapoglou, Pantelis-Daniel UL; Ottersten, Björn UL

in IEEE Transactions on Wireless Communications (2012), 11(8), 2806-2814

An increasing number of hybrid mobile systems comprising a satellite and a terrestrial component are becoming standardized and realized. The next generation of these systems will employ higher dimensions ... [more ▼]

An increasing number of hybrid mobile systems comprising a satellite and a terrestrial component are becoming standardized and realized. The next generation of these systems will employ higher dimensions adopting multiple-input multiple-output orthogonal frequency division multiplexing (MIMO-OFDM) techniques. In this work, we build upon recent studies of dual polarization MIMO for each component and propose the use of full-rate full-diversity (FRFD) codes adopting a space-frequency paradigm. We also propose a scheme taking advantage of the separation between the subcarriers to enhance the coding gain. By critically assessing the different options for the 4 transmit, 2 receive hybrid scenario taking into account system and channel particularities, we demonstrate that the proposed scheme is a solution for enhancing the performance of next generation hybrid mobile satellite systems. [less ▲]

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See detailOperational Optimization of a Ku Multibeam Flexible Payload
Metzger, Nathalie; Morgues, Stephane; Morel, Coline et al

in Proceedings of 2nd ESA workshop on Advanced Flexible Telecom Payloads (2012, April)

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See detailMulticarrier Digital Pre-distortion/ Equalization Techniques for Non-linear Satellite Channels
Piazza, Roberto UL; Shankar, Bhavani UL; E, Zenteno et al

in Proceedings of 30th AIAA International Communications Satellite Systems Conference (ICSSC), (2012)

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See detailPower allocation in Multibeam satellites - A hybrid-Genetic Algorithm approach
Aravanis, Alexis; Shankar, Bhavani UL; Danoy, Grégoire UL et al

in ESA Workshop on Advanced Flexible Telecom Payloads (2012)

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See detailDetection of sparse random signals using compressive measurements
Shankar, Bhavani UL; Chatterjee, Saikat; Ottersten, Björn UL

in Acoustics, Speech and Signal Processing (ICASSP), 2012 IEEE International Conference on (2012)

We consider the problem of detecting a sparse random signal from the compressive measurements without reconstructing the signal. Using a subspace model for the sparse signal where the signal parameters ... [more ▼]

We consider the problem of detecting a sparse random signal from the compressive measurements without reconstructing the signal. Using a subspace model for the sparse signal where the signal parameters are drawn according to Gaussian law, we obtain the detector based on Neyman-Pearson criterion and analytically determine its operating characteristics when the signal covariance is known. These results are extended to situations where the covariance cannot be estimated. The results can be used to determine the number of measurements needed for a particular detector performance and also illustrate the presence of an optimal support for a given number of measurements. [less ▲]

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See detailMulti-objective Optimization Approach to Power Allocation in Multibeam Systems
Aravanis, Alexis; Shankar, Bhavani UL; Danoy, Grégoire UL et al

in Proceedings of 30th AIAA International Communications Satellite Systems Conference (ICSSC), (2012)

Detailed reference viewed: 158 (19 UL)