Carlos Mosquera - Academia.edu (original) (raw)
Papers by Carlos Mosquera
This work is concerned with the performance of adaptive filters with both poles and zeros in acti... more This work is concerned with the performance of adaptive filters with both poles and zeros in active noise control (ANC) applications. This filtered-error type of applications makes it necessary to modify classical adaptive algorithms to cancel the noise. Thus, a well established theory exists for filtered-error adaptive FIR filters, with a special mention for the FxLMS algorithm. However, when it comes to filtered-error adaptive IIR filters, convergence conditions are not so well understood. IIR filters are specially suited to those scenarios where feedback from the canceling loudspeaker to the primary source presents high values, and the performance of the cancellation with a fixed filter is not as good as desired. In this work we present the study of the convergence of a family of adaptive IIR algorithms appropriately modified for handling filtered-error situations. The results are particularized for Eriksson's algorithm FuRLMS, a popular scheme whose global convergence has never been proved formally. Conditions for the convergence of FuRLMS are shown to be an extension of those for FxLMS. Finally, some results based on real measurements are also presented.
∗ Dept. Teorıa de la Senal y Comunicaciones Universidad de Vigo 36200 Vigo, Spain Phone: +34-986... more ∗ Dept. Teorıa de la Senal y Comunicaciones Universidad de Vigo 36200 Vigo, Spain Phone: +34-986812672 Fax: +34-986812116 E-mail: mferreir@gts.tsc.uvigo.es ... Dept. Teorıa de la Senal y Comunicaciones Universidad de Vigo 36200 Vigo, Spain Phone: +34-...
The design of broadcasting networks operating in a single frequency way is challenging due to the... more The design of broadcasting networks operating in a single frequency way is challenging due to the difficulty of predicting the performance in a frequency selective channel, caused by natural multipath and echoes coming from different transmitters. In this paper we resort to the use of frame error rate prediction metrics (also known as effective SNR metrics) to characterize the performance gain (or loss) under different multipath and SNR regimes in a simplified scenario with two transmitters. The analysis shows clearly that receivers with a dominant line of sight reception and high SNR are more sensitive to the presence of echoes, while those users in low SNR or strong multipath conditions are easily enforced by the insertion of a second transmitter.
2014 7th Advanced Satellite Multimedia Systems Conference and the 13th Signal Processing For Space Communications Workshop, Sep 9, 2014
We consider the problem of modulation and coding scheme selection in the return link of a mobile ... more We consider the problem of modulation and coding scheme selection in the return link of a mobile satellite system. We propose to use a weighted combination of both open loop and closed loop signal quality indicators to perform this selection. The combination weights are not selected by making any assumptions on the channel distribution; instead, they are dynamically adapted according to the ACK/NAK exchange between both ends. This adaptation procedure is obtained as a stochastic programming solution to an optimization problem. Numerical results will show the good performance of the proposed method compared to previous algorithms, and its robustness to environment changes.
Ieee Transactions on Wireless Communications, Jun 9, 2014
Rain attenuation is among the major impairments for satellite systems operating in the K band and... more Rain attenuation is among the major impairments for satellite systems operating in the K band and above. In this paper, we investigate the impact of spatially correlated rain attenuation on the performance of a multibeam satellite return link. For a comprehensive assessment, an analytical model for the antenna pattern that generates the beams is also proposed. We focus on the outage capacity of the link, and obtain analytical approximations at high and low SNR. The derived approximations provide insights on the effect of key system parameterslike the inter-user distance, the satellite beam radius, or the rain intensity-and simulation results show that it fits tightly to the Monte Carlo results. Additionally, the derived expressions can be easily particularized for the single-user case, providing some novel insights.
ABSTRACT Current multibeam satellite systems consist of a very large number of spot beams. In thi... more ABSTRACT Current multibeam satellite systems consist of a very large number of spot beams. In this paper, we analyze them from the large scale MIMO perspective, and establish a comparison with massive MIMO systems. It will be shown that the large number of beams has important operational implications, and that it simplifies the analysis because it allows using asymptotic results. However, it will also be shown that current multibeam satellite links, despite their large number of antennas, do not qualify as massive MIMO systems.
Adapting the transmission rate in an LMS channel is a challenging task because of the relatively ... more Adapting the transmission rate in an LMS channel is a challenging task because of the relatively fast time variations, of the long delays involved, and of the difficulty in mapping the parameters of a time-varying channel into communication performance. In this paper, we propose two strategies for dealing with these impairments, namely, multi-layer coding (MLC) in the forward link, and open-loop adaptation in the return link. Both strategies rely on physical-layer abstraction tools for predicting the link performance. We will show that, in both cases, it is possible to increase the average spectral efficiency while at the same time keeping the outage probability under a given threshold. To do so, the forward link strategy will rely on introducing some latency in the data stream by using retransmissions. The return link, on the other hand, will rely on a statistical characterization of a physical-layer abstraction measure.
2011 IEEE Global Telecommunications Conference - GLOBECOM 2011, 2011
ABSTRACT Next generation high throughput satellite systems are expected to rely on the deployment... more ABSTRACT Next generation high throughput satellite systems are expected to rely on the deployment of a high number of beams in the user link, and therefore operate in an interference limited regime. This paper builds on the combination of advanced interference mitigation techniques and ground based beamforming to cope with this increased level of interference among users. Focussing on the forward link of a multi-beam broadband satellite system, we consider the joint design of linear precoding and ground based beamforming at the gateway. This joint design is modeled, and different linear precoding techniques are considered for comparison. The provided simulation results quantify the performance gain generated by this joint design with respect to considering precoding for a fixed on-board beamforming. The robustness of the considered scheme to channel estimation errors is also analyzed.
Digital Intermediate Frequency (IF) receivers are achieving a widespread use, also in satellite a... more Digital Intermediate Frequency (IF) receivers are achieving a widespread use, also in satellite applications. By means of this paradigm the received RF spectrum is moved down to IF, and digitization occurs at the low IF. Thereafter, digital signal processing techniques are used to extract the signal. When it comes to synchroniza-tion, some new issues arise due to the possibly di
Proceedings of 1995 34th IEEE Conference on Decision and Control, 1995
IEEE Transactions on Wireless Communications, 2014
Rain attenuation is among the major impairments for satellite systems operating in the K band and... more Rain attenuation is among the major impairments for satellite systems operating in the K band and above. In this paper, we investigate the impact of spatially correlated rain attenuation on the performance of a multibeam satellite return link. For a comprehensive assessment, an analytical model for the antenna pattern that generates the beams is also proposed. We focus on the outage capacity of the link, and obtain analytical approximations at high and low SNR. The derived approximations provide insights on the effect of key system parameterslike the inter-user distance, the satellite beam radius, or the rain intensity-and simulation results show that it fits tightly to the Monte Carlo results. Additionally, the derived expressions can be easily particularized for the single-user case, providing some novel insights.
The design of broadcasting networks operating in a single frequency way is challenging due to the... more The design of broadcasting networks operating in a single frequency way is challenging due to the difficulty of predicting the performance in a frequency selective channel, caused by natural multipath and echoes coming from different transmitters. In this paper we resort to the use of frame error rate prediction metrics (also known as effective SNR metrics) to characterize the performance gain (or loss) under different multipath and SNR regimes in a simplified scenario with two transmitters. The analysis shows clearly that receivers with a dominant line of sight reception and high SNR are more sensitive to the presence of echoes, while those users in low SNR or strong multipath conditions are easily enforced by the insertion of a second transmitter.
Current multibeam satellite systems consist of a very large number of spot beams. In this paper, ... more Current multibeam satellite systems consist of a very large number of spot beams. In this paper, we analyze them from the large scale MIMO perspective, and establish a comparison with massive MIMO systems. It will be shown that the large number of beams has important operational implications, and that it simplifies the analysis because it allows using asymptotic results. However, it will also be shown that current multibeam satellite links, despite their large number of antennas, do not qualify as massive MIMO systems.
2013 Asilomar Conference on Signals, Systems and Computers, 2013
The inherently large propagation delay present in satellite communications makes link adaptation ... more The inherently large propagation delay present in satellite communications makes link adaptation procedures difficult to apply. Particularly, channel state information at the transmitter (CSIT) can be completely outdated after a round-trip time for high-speed receivers. For moderate speeds, some correlation is expected between the current channel and the CSIT. In this paper we present a link adaptation procedure that uses both CSIT and statistical information about the channel variation. We exploit the use of retransmissions to alleviate the rate backoff induced by the outage constraint. The link adaptation procedure is stated as the maximization of the throughput subject to a packet error probability constraint, and the channel variation is captured by a time-homogeneous Markov chain.
Security, Steganography, and Watermarking of Multimedia Contents VIII, 2006
2014 7th Advanced Satellite Multimedia Systems Conference and the 13th Signal Processing for Space Communications Workshop (ASMS/SPSC), 2014
We consider the problem of modulation and coding scheme selection in the return link of a mobile ... more We consider the problem of modulation and coding scheme selection in the return link of a mobile satellite system. We propose to use a weighted combination of both open loop and closed loop signal quality indicators to perform this selection. The combination weights are not selected by making any assumptions on the channel distribution; instead, they are dynamically adapted according to the ACK/NAK exchange between both ends. This adaptation procedure is obtained as a stochastic programming solution to an optimization problem. Numerical results will show the good performance of the proposed method compared to previous algorithms, and its robustness to environment changes.
2012 6th Advanced Satellite Multimedia Systems Conference (ASMS) and 12th Signal Processing for Space Communications Workshop (SPSC), 2012
Hybrid terrestrial-satellite Single Frequency Networks (SFN) achieve large spectral efficiencies ... more Hybrid terrestrial-satellite Single Frequency Networks (SFN) achieve large spectral efficiencies due to a higher frequency reuse, which is attained by transmitting the same waveform in the same frequency band from satellite and terrestrial transmitters. However, the presence of multiple transmitters propitiates the existence of the so-called SFN echoes, which can degrade the system performance even if they arrive within the Orthogonal Frequency Division Multiplexing (OFDM) guard interval. In this paper we characterize this effect by resorting to Packet Error Rate (PER) prediction metrics (or effective Signal to Noise Ratio (SNR) metrics), and analyze two simple preprocessing schemes that mitigate this degradation: the use of Alamouti space-time codes, and a convenient pre-filtering at the terrestrial transmitter.
This work is concerned with the performance of adaptive filters with both poles and zeros in acti... more This work is concerned with the performance of adaptive filters with both poles and zeros in active noise control (ANC) applications. This filtered-error type of applications makes it necessary to modify classical adaptive algorithms to cancel the noise. Thus, a well established theory exists for filtered-error adaptive FIR filters, with a special mention for the FxLMS algorithm. However, when it comes to filtered-error adaptive IIR filters, convergence conditions are not so well understood. IIR filters are specially suited to those scenarios where feedback from the canceling loudspeaker to the primary source presents high values, and the performance of the cancellation with a fixed filter is not as good as desired. In this work we present the study of the convergence of a family of adaptive IIR algorithms appropriately modified for handling filtered-error situations. The results are particularized for Eriksson's algorithm FuRLMS, a popular scheme whose global convergence has never been proved formally. Conditions for the convergence of FuRLMS are shown to be an extension of those for FxLMS. Finally, some results based on real measurements are also presented.
∗ Dept. Teorıa de la Senal y Comunicaciones Universidad de Vigo 36200 Vigo, Spain Phone: +34-986... more ∗ Dept. Teorıa de la Senal y Comunicaciones Universidad de Vigo 36200 Vigo, Spain Phone: +34-986812672 Fax: +34-986812116 E-mail: mferreir@gts.tsc.uvigo.es ... Dept. Teorıa de la Senal y Comunicaciones Universidad de Vigo 36200 Vigo, Spain Phone: +34-...
The design of broadcasting networks operating in a single frequency way is challenging due to the... more The design of broadcasting networks operating in a single frequency way is challenging due to the difficulty of predicting the performance in a frequency selective channel, caused by natural multipath and echoes coming from different transmitters. In this paper we resort to the use of frame error rate prediction metrics (also known as effective SNR metrics) to characterize the performance gain (or loss) under different multipath and SNR regimes in a simplified scenario with two transmitters. The analysis shows clearly that receivers with a dominant line of sight reception and high SNR are more sensitive to the presence of echoes, while those users in low SNR or strong multipath conditions are easily enforced by the insertion of a second transmitter.
2014 7th Advanced Satellite Multimedia Systems Conference and the 13th Signal Processing For Space Communications Workshop, Sep 9, 2014
We consider the problem of modulation and coding scheme selection in the return link of a mobile ... more We consider the problem of modulation and coding scheme selection in the return link of a mobile satellite system. We propose to use a weighted combination of both open loop and closed loop signal quality indicators to perform this selection. The combination weights are not selected by making any assumptions on the channel distribution; instead, they are dynamically adapted according to the ACK/NAK exchange between both ends. This adaptation procedure is obtained as a stochastic programming solution to an optimization problem. Numerical results will show the good performance of the proposed method compared to previous algorithms, and its robustness to environment changes.
Ieee Transactions on Wireless Communications, Jun 9, 2014
Rain attenuation is among the major impairments for satellite systems operating in the K band and... more Rain attenuation is among the major impairments for satellite systems operating in the K band and above. In this paper, we investigate the impact of spatially correlated rain attenuation on the performance of a multibeam satellite return link. For a comprehensive assessment, an analytical model for the antenna pattern that generates the beams is also proposed. We focus on the outage capacity of the link, and obtain analytical approximations at high and low SNR. The derived approximations provide insights on the effect of key system parameterslike the inter-user distance, the satellite beam radius, or the rain intensity-and simulation results show that it fits tightly to the Monte Carlo results. Additionally, the derived expressions can be easily particularized for the single-user case, providing some novel insights.
ABSTRACT Current multibeam satellite systems consist of a very large number of spot beams. In thi... more ABSTRACT Current multibeam satellite systems consist of a very large number of spot beams. In this paper, we analyze them from the large scale MIMO perspective, and establish a comparison with massive MIMO systems. It will be shown that the large number of beams has important operational implications, and that it simplifies the analysis because it allows using asymptotic results. However, it will also be shown that current multibeam satellite links, despite their large number of antennas, do not qualify as massive MIMO systems.
Adapting the transmission rate in an LMS channel is a challenging task because of the relatively ... more Adapting the transmission rate in an LMS channel is a challenging task because of the relatively fast time variations, of the long delays involved, and of the difficulty in mapping the parameters of a time-varying channel into communication performance. In this paper, we propose two strategies for dealing with these impairments, namely, multi-layer coding (MLC) in the forward link, and open-loop adaptation in the return link. Both strategies rely on physical-layer abstraction tools for predicting the link performance. We will show that, in both cases, it is possible to increase the average spectral efficiency while at the same time keeping the outage probability under a given threshold. To do so, the forward link strategy will rely on introducing some latency in the data stream by using retransmissions. The return link, on the other hand, will rely on a statistical characterization of a physical-layer abstraction measure.
2011 IEEE Global Telecommunications Conference - GLOBECOM 2011, 2011
ABSTRACT Next generation high throughput satellite systems are expected to rely on the deployment... more ABSTRACT Next generation high throughput satellite systems are expected to rely on the deployment of a high number of beams in the user link, and therefore operate in an interference limited regime. This paper builds on the combination of advanced interference mitigation techniques and ground based beamforming to cope with this increased level of interference among users. Focussing on the forward link of a multi-beam broadband satellite system, we consider the joint design of linear precoding and ground based beamforming at the gateway. This joint design is modeled, and different linear precoding techniques are considered for comparison. The provided simulation results quantify the performance gain generated by this joint design with respect to considering precoding for a fixed on-board beamforming. The robustness of the considered scheme to channel estimation errors is also analyzed.
Digital Intermediate Frequency (IF) receivers are achieving a widespread use, also in satellite a... more Digital Intermediate Frequency (IF) receivers are achieving a widespread use, also in satellite applications. By means of this paradigm the received RF spectrum is moved down to IF, and digitization occurs at the low IF. Thereafter, digital signal processing techniques are used to extract the signal. When it comes to synchroniza-tion, some new issues arise due to the possibly di
Proceedings of 1995 34th IEEE Conference on Decision and Control, 1995
IEEE Transactions on Wireless Communications, 2014
Rain attenuation is among the major impairments for satellite systems operating in the K band and... more Rain attenuation is among the major impairments for satellite systems operating in the K band and above. In this paper, we investigate the impact of spatially correlated rain attenuation on the performance of a multibeam satellite return link. For a comprehensive assessment, an analytical model for the antenna pattern that generates the beams is also proposed. We focus on the outage capacity of the link, and obtain analytical approximations at high and low SNR. The derived approximations provide insights on the effect of key system parameterslike the inter-user distance, the satellite beam radius, or the rain intensity-and simulation results show that it fits tightly to the Monte Carlo results. Additionally, the derived expressions can be easily particularized for the single-user case, providing some novel insights.
The design of broadcasting networks operating in a single frequency way is challenging due to the... more The design of broadcasting networks operating in a single frequency way is challenging due to the difficulty of predicting the performance in a frequency selective channel, caused by natural multipath and echoes coming from different transmitters. In this paper we resort to the use of frame error rate prediction metrics (also known as effective SNR metrics) to characterize the performance gain (or loss) under different multipath and SNR regimes in a simplified scenario with two transmitters. The analysis shows clearly that receivers with a dominant line of sight reception and high SNR are more sensitive to the presence of echoes, while those users in low SNR or strong multipath conditions are easily enforced by the insertion of a second transmitter.
Current multibeam satellite systems consist of a very large number of spot beams. In this paper, ... more Current multibeam satellite systems consist of a very large number of spot beams. In this paper, we analyze them from the large scale MIMO perspective, and establish a comparison with massive MIMO systems. It will be shown that the large number of beams has important operational implications, and that it simplifies the analysis because it allows using asymptotic results. However, it will also be shown that current multibeam satellite links, despite their large number of antennas, do not qualify as massive MIMO systems.
2013 Asilomar Conference on Signals, Systems and Computers, 2013
The inherently large propagation delay present in satellite communications makes link adaptation ... more The inherently large propagation delay present in satellite communications makes link adaptation procedures difficult to apply. Particularly, channel state information at the transmitter (CSIT) can be completely outdated after a round-trip time for high-speed receivers. For moderate speeds, some correlation is expected between the current channel and the CSIT. In this paper we present a link adaptation procedure that uses both CSIT and statistical information about the channel variation. We exploit the use of retransmissions to alleviate the rate backoff induced by the outage constraint. The link adaptation procedure is stated as the maximization of the throughput subject to a packet error probability constraint, and the channel variation is captured by a time-homogeneous Markov chain.
Security, Steganography, and Watermarking of Multimedia Contents VIII, 2006
2014 7th Advanced Satellite Multimedia Systems Conference and the 13th Signal Processing for Space Communications Workshop (ASMS/SPSC), 2014
We consider the problem of modulation and coding scheme selection in the return link of a mobile ... more We consider the problem of modulation and coding scheme selection in the return link of a mobile satellite system. We propose to use a weighted combination of both open loop and closed loop signal quality indicators to perform this selection. The combination weights are not selected by making any assumptions on the channel distribution; instead, they are dynamically adapted according to the ACK/NAK exchange between both ends. This adaptation procedure is obtained as a stochastic programming solution to an optimization problem. Numerical results will show the good performance of the proposed method compared to previous algorithms, and its robustness to environment changes.
2012 6th Advanced Satellite Multimedia Systems Conference (ASMS) and 12th Signal Processing for Space Communications Workshop (SPSC), 2012
Hybrid terrestrial-satellite Single Frequency Networks (SFN) achieve large spectral efficiencies ... more Hybrid terrestrial-satellite Single Frequency Networks (SFN) achieve large spectral efficiencies due to a higher frequency reuse, which is attained by transmitting the same waveform in the same frequency band from satellite and terrestrial transmitters. However, the presence of multiple transmitters propitiates the existence of the so-called SFN echoes, which can degrade the system performance even if they arrive within the Orthogonal Frequency Division Multiplexing (OFDM) guard interval. In this paper we characterize this effect by resorting to Packet Error Rate (PER) prediction metrics (or effective Signal to Noise Ratio (SNR) metrics), and analyze two simple preprocessing schemes that mitigate this degradation: the use of Alamouti space-time codes, and a convenient pre-filtering at the terrestrial transmitter.