A limited feedback scheme based on spatially correlated channels for coordinated multipoint systems

High spectral efficiency can be achieved in the downlink of multi-antenna coordinated multi-point systems provided that the multiuser interference is appropriately managed at the transmitter side. For this sake, downlink channel information needs to be sent back by the users, thus reducing the rate available at the uplink channel. The amount and type of feedback information required has been extensively studied and many limited feedback schemes have been proposed lately. A common pattern to all of them is that achieving low rates of feedback information is possible at the cost of increasing complexity at the user side and, sometimes, assuming that some statistics of the channel are known. In this article, we propose a simple and versatile limited feedback scheme that exploits the spatial correlation at each multi-antenna base station (BS) without requiring any previous statistical information of the channel and without adding significant computational complexity. It is based on the separate quantization of the channel impulse response modulus and phase and it shows better mean square error performance than the standard scheme based on quantization of real and imaginary parts. In order to evaluate the performance of the downlink regarding multiuser interference management, different precoding techniques at the BSs, such as zero-forcing (ZF), Tomlinson-Harashima precoding (THP) and lattice reduction Tomlinson- Harashima precoding (LRTHP), have been evaluated. Simulations results show that LRTHP and THP present a higher robustness than ZF precoding against channel quantization errors but at the cost of a higher complexity at the BS. Regarding sum-capacity and bit error rate performances, our versatile scheme achieves better results than the standard one in the medium and high SNR regime, that is, in the region where quantization errors are dominant against noise, for the same feedback cost measured in bits per user

Coordination in a multi-cell multi-antenna multi-user W-CDMA system: a beamforming approach

The problem of designing Joint Power Control and Optimal Beamforming (JPCOB) algorithms for the downlink of a coordinated multi-cellW-CDMA system is considered throughout this paper. In this case, the JPCOB design is formulated as the problem of minimizing the total transmitted power in the coordinated multi-cell system, subject to a certain quality of service requirement for each user. In this paper, the performance of two JPCOB algorithms based on different beamforming approaches is compared over the coordinated multi-cell system. The first one, obtains local beamformers by means of the well-known virtual uplink-downlink duality. In contrast, the second algorithm implements multi-base beamformers, taking into account match filter equalizers at the receivers. Moreover, realistic system parameters, such as per-base station power constraints or the asynchronous nature of the signals arriving at the receivers, are taken into account. Simulation results show that the algorithm based on multi-base beamforming presents attractive properties, such as an inherent multi-base scheduling technique or a decreasing total transmitted power as the degree of coordination between base stations is increased

Affine Projection Algorithm Over Acoustic Sensor Networks for Active Noise Control

[EN] Acoustic sensor networks (ASNs) are an effective solution to implement active noise control (ANC) systems by using distributed adaptive algorithms. On one hand, ASNs provide scalable systems where the signal processing load is distributed among the network nodes. On the other hand, their noise reduction performance is comparable to that of their respective centralized processing systems. In this sense, the distributed multiple error filtered-x least mean squares (DMEFxLMS) adaptive algorithm has shown to obtain the same performance than its centralized counterpart as long as there are no communications constraints in the underlying ASN. Regarding affine projection (AP) adaptive algorithms, some distributed approaches that are approximated versions of the multichannel filtered-x affine projection (MFxAP) algorithm have been previously proposed. These AP algorithms can efficiently share the processing load among the nodes, but at the expense of worsening their convergence properties. In this paper we develop the exact distributed multichannel filtered-x AP (EFxAP) algorithm, which obtains the same solution as that of the MFxAP algorithm as long as there are no communications constraints in the underlying ASN. In the EFxAP algorithm each node can compute a part or the entire inverse matrix needed by the centralized MFxAP algorithm. Thus, we propose three different strategies that obtain significant computational saving: 1) Gauss Elimination, 2) block LU factorization, and 3) matrix inversion lemma. As a result, each node computes only between 25%¿60% of the number of multiplications required by the direct inversion of the matrix. Regarding the performance in transient and steady states, the EFxAP exhibits the fastest convergence and the highest noise level reduction for any size of the acoustic network and any projection order of the AP algorithm compared to the DMEFxLMS and two previously reported distributed AP algorithms.This work was supported by EU together with Spanish Government through RTI2018-098085B-C41 (MINECO/FEDER) and Generalitat Valenciana through PROMETEO/2019/109.Ferrer Contreras, M.; Diego Antón, MD.; Piñero, G.; Gonzalez, A. (2021). Affine Projection Algorithm Over Acoustic Sensor Networks for Active Noise Control. IEEE/ACM Transactions on Audio Speech and Language Processing. 29:448-461. https://doi.org/10.1109/TASLP.2020.3042590S4484612

Personal Sound Zones by Subband Filtering and Time Domain Optimization

[EN] Personal Sound Zones (PSZ) systems aim to render independent sound signals to multiple listeners within a room by using arrays of loudspeakers. One of the algorithms used to provide PSZ is Weighted Pressure Matching (wPM), which computes the filters required to render a desired response in the listening zones while reducing the acoustic energy arriving to the quiet zones. This algorithm can be formulated in time and frequency domains. In general, the time-domain formulation (wPM-TD) can obtain good performance with shorter filters and delays than the frequency-domain formulation (wPM-FD). However, wPM-TD requires higher computation for obtaining the optimal filters. In this article, we propose a novel approach to the wPM algorithm named Weighted Pressure Matching with Subband Decomposition (wPMSD), which formulates an independent time-domain optimization problem for each of the subbands of a Generalized Discrete Fourier Transform (GDFT) filter bank. Solving the optimization independently for each subband has two main advantages: 1) lower computational complexity than wPM-TD to compute the optimal filters; 2) higher versatility than the classic wPM algorithms, as it allows different configurations (sets of loudspeakers, filter lengths, etc.) in each subband. Moreover, filtering the input signals with a GDFT filter bank (as in wPM-SD) requires lower computational effort than broadband filtering (as in wPM-TD and wPM-FD), which is beneficial for practical PSZ systems. We present experimental evaluations showing that wPM-SD offers very similar performance to wPM-TD. In addition, two cases where the versatility of wPM-SD is beneficial for a PSZ system are presented and experimentally validated.This work was supported by Grants RTI2018-098085-B-C41 (MCIU/AEI/FEDER, UE), RED2018-102668-T and PROMETEO/2019/109. The work of Vicent Moles-Cases has been supported by Spanish Ministry of Education under Grant FPU17/01288.Molés-Cases, V.; Piñero, G.; Diego Antón, MD.; Gonzalez, A. (2020). Personal Sound Zones by Subband Filtering and Time Domain Optimization. IEEE/ACM Transactions on Audio Speech and Language Processing. 28:2684-2696. https://doi.org/10.1109/TASLP.2020.3023628S268426962

High performance lattice reduction on heterogeneous computing platform

The final publication is available at Springer via http://dx.doi.org/10.1007/s11227-014-1201-2The lattice reduction (LR) technique has become very important in many engineering fields. However, its high complexity makes difficult its use in real-time applications, especially in applications that deal with large matrices. As a solution, the modified block LLL (MB-LLL) algorithm was introduced, where several levels of parallelism were exploited: (a) fine-grained parallelism was achieved through the cost-reduced all-swap LLL (CR-AS-LLL) algorithm introduced together with the MB-LLL by Jzsa et al. (Proceedings of the tenth international symposium on wireless communication systems, 2013) and (b) coarse-grained parallelism was achieved by applying the block-reduction concept presented by Wetzel (Algorithmic number theory. Springer, New York, pp 323-337, 1998). In this paper, we present the cost-reduced MB-LLL (CR-MB-LLL) algorithm, which allows to significantly reduce the computational complexity of the MB-LLL by allowing the relaxation of the first LLL condition while executing the LR of submatrices, resulting in the delay of the Gram-Schmidt coefficients update and by using less costly procedures during the boundary checks. The effects of complexity reduction and implementation details are analyzed and discussed for several architectures. A mapping of the CR-MB-LLL on a heterogeneous platform is proposed and it is compared with implementations running on a dynamic parallelism enabled GPU and a multi-core CPU. The mapping on the architecture proposed allows a dynamic scheduling of kernels where the overhead introduced is hidden by the use of several CUDA streams. Results show that the execution time of the CR-MB-LLL algorithm on the heterogeneous platform outperforms the multi-core CPU and it is more efficient than the CR-AS-LLL algorithm in case of large matrices.Financial support for this study was provided by grants TAMOP-4.2.1./B-11/2/KMR-2011-0002, TAMOP-4.2.2/B-10/1-2010-0014 from the Pazmany Peter Catholic University, European Union ERDF, Spanish Government through TEC2012-38142-C04-01 project and Generalitat Valenciana through PROMETEO/2009/013 project.Jozsa, CM.; Domene Oltra, F.; Vidal Maciá, AM.; Piñero Sipán, MG.; González Salvador, A. (2014). High performance lattice reduction on heterogeneous computing platform. Journal of Supercomputing. 70(2):772-785. https://doi.org/10.1007/s11227-014-1201-2S772785702Józsa CM, Domene F, Piñero G, González A, Vidal AM (2013) Efficient GPU implementation of lattice-reduction-aided multiuser precoding. In: Proceedings of the tenth international symposium on wireless communication systems (ISWCS 2013)Wetzel S (1998) An efficient parallel block-reduction algorithm. In: Buhler JP (ed) Algorithmic number theory. Lecture notes in computer science, vol 1423. Springer, Berlin, Heidelberg, pp 323–337Wubben D, Seethaler D, Jaldén J, Matz G (2011) Lattice reduction. Signal Process Mag IEEE 28(3):70–91Lenstra AK, Lenstra HW, Lovász L (1982) Factoring polynomials with rational coefficients. Math Ann 261(4):515–534Bremner MR (2012) Lattice basis reduction: an introduction to the LLL algorithm and its applications. CRC Press, USAWu D, Eilert J, Liu D (2008) A programmable lattice-reduction aided detector for MIMO-OFDMA. In: 4th IEEE international conference on circuits and systems for communications (ICCSC 2008), pp 293–297Barbero LG, Milliner DL, Ratnarajah T, Barry JR, Cowan C (2009) Rapid prototyping of Clarkson’s lattice reduction for MIMO detection. In: IEEE international conference on communications (ICC’09), pp 1–5Gestner B, Zhang W, Ma X, Anderson D (2011) Lattice reduction for MIMO detection: from theoretical analysis to hardware realization. IEEE Trans Circ Syst I Regul Pap 58(4):813–826Shabany M, Youssef A, Gulak G (2013) High-throughput 0.13- \upmu μ m CMOS lattice reduction core supporting 880 Mb/s detection. IEEE Trans Very Large Scale Integr (VLSI) Syst 21(5):848–861Luo Y, Qiao S (2011) A parallel LLL algorithm. In: Proceedings of the fourth international C* conference on computer science and software engineering, pp 93–101Backes W, Wetzel S (2011) Parallel lattice basis reduction—the road to many-core. In: IEEE 13th international conference on high performance computing and communications (HPCC)Ahmad U, Amin A, Li M, Pollin S, Van der Perre L, Catthoor F (2011) Scalable block-based parallel lattice reduction algorithm for an SDR baseband processor. In: 2011 IEEE international conference on communications (ICC)Villard G (1992) Parallel lattice basis reduction. In: Papers from the international symposium on symbolic and algebraic computation (ISSAC’92). ACM, New YorkDomene F, Józsa CM, Vidal AM, Piñero G, Gonzalez A (2013) Performance analysis of a parallel lattice reduction algorithm on many-core architectures. In: Proceedings of the 13th international conference on computational and mathematical methods in science and engineeringGestner B, Zhang W, Ma X, Anderson DV (2008) VLSI implementation of a lattice reduction algorithm for low-complexity equalization. In: 4th IEEE international conference on circuits and systems for communications (ICCSC 2008), pp 643–647Burg A, Seethaler D, Matz G (2007) VLSI implementation of a lattice-reduction algorithm for multi-antenna broadcast precoding. In: IEEE international symposium on circuits and systems (ISCAS 2007), pp 673–676Bruderer L, Studer C, Wenk M, Seethaler D, Burg A (2010) VLSI implementation of a low-complexity LLL lattice reduction algorithm for MIMO detection. In: Proceedings of 2010 IEEE international symposium on circuits and systems (ISCAS

Multi-tone Active Noise Equalizer with Spatially Distributed User-selected Profiles

[EN] In this work we propose a multi-channel active noise equalizer (ANE) that can deal with multi-frequency noise signals and assigns simultaneously different equalization gains to each frequency component at each monitoring sensor. For this purpose, we state a pseudo-error noise signal for each sensor of the ANE, which has to be cancelled out in order to get the desired equalization profiles. Firstly the optimal analytic solution for the ANE filters in the case of single-frequency noise is provided, and an adaptive algorithm based on the Least Mean Squared (LMS) is proposed for the same case. We also show that this adaptive strategy reaches the theoretical solution in steady state. Secondly, we state an equivalent approach for the case of multi-frequency noise based on two alternatives: a common pseudo-error signal at each sensor for all frequencies, and a different pseudo-error signal at each sensor for each frequency. The analytic and adaptive solutions for the ANE control filters have been developed for both pseudo-error alternatives. Finally, the ability of the proposed ANE to achieve simultaneously different user-selected noise profiles in different locations has been validated by their transfer functions and simulations.This work was supported by EU jointly with Spanish Government and Generalitat Valenciana under Grants RTI2018-098085-BC41, PID2021-125736OB-I00 (MCIU/AEI/FEDER), RE D2018-102668-T, and PROMETEO/2019/109.Ferrer Contreras, M.; Diego Antón, MD.; Hassani, A.; Moonen, M.; Piñero, G.; Gonzalez, A. (2022). Multi-tone Active Noise Equalizer with Spatially Distributed User-selected Profiles. IEEE/ACM Transactions on Audio Speech and Language Processing. 30:3199-3213. https://doi.org/10.1109/TASLP.2022.3212833319932133

Fast block QR update in digital signal processing

[EN] The processing of digital sound signals often requires the computation of the QR factorization of a rectangular system matrix. However, sometimes, only a given (and probably small) part of the system matrix varies from the current sample to the next one. We exploit this fact to reuse some computations carried out to process the former sample in order to save execution time in the processing of the current sample. These savings can be critical for real-time applications running on low power consumption devices with high mobility. In addition, we propose a simple out-of-order task-parallel algorithm for the QR factorization using OpenMP that exploits the multicore capability of modern processors. Furthermore, in the presence of a Graphics Processing Unit (GPU) in the system, our algorithm is able to off-load some tasks to the GPU to accelerate the computation on these hardware devices.This work was supported by the Spanish Ministry of Economy and Competitiveness under MINECO and FEDER projects TEC2015-67387-C4-1-R and TIN2014-53495-R; and the Generalitat Valenciana PROMETEOII/2014/003Alventosa, FJ.; Alonso-Jordá, P.; Vidal Maciá, AM.; Piñero, G.; Quintana-Ortí, ES. (2019). Fast block QR update in digital signal processing. The Journal of Supercomputing. 75(3):1051-1064. https://doi.org/10.1007/s11227-018-2298-5S10511064753Augonnet C, Thibault S, Namyst R (2010) StarPU: a runtime system for scheduling tasks over accelerator-based multicore machines. Research Report RR-7240, INRIAButtari A, Langou J, Kurzak J, Dongarra J (2008) Parallel tiled QR factorization for multicore architectures. Concurr Comput Pract Exp 20(13):1573–1590Buttari A, Langou J, Kurzak J, Dongarra J (2009) A class of parallel tiled linear algebra algorithms for multicore architectures. Parallel Comput 35(1):38–53Chan E, Quintana-Ortí ES, Quintana-Ortí G, van de Geijn R (2007) Supermatrix out-of-order scheduling of matrix operations for smp and multi-core architectures. In: Proceedings of the Nineteenth Annual ACM Symposium on Parallel Algorithms and Architectures, SPAA ’07. ACM, New York, pp 116–125Chan E, Van Zee FG, Quintana-Ortí ES, Quintana-Ortí G, De Van Geijn R (2007) Satisfying your dependencies with supermatrix. In: Proceedings—2007 IEEE International Conference on Cluster Computing, CLUSTER 2007. pp 91–99Chan E, Van Zee FG, Bientinesi P, Quintana-Ortí ES, Quintana-Ortí G, van de Geijn RA (2008) Supermatrix: a multithreaded runtime scheduling system for algorithms-by-blocks. In: Chatterjee S, Scott ML (eds) PPOPP. ACM, New york, pp 123–132Golub GH, Van Loan CF (2013) Matrix computations. Johns Hopkins Studies in the Mathematical Sciences. Johns Hopkins University Press, BaltimoreGunter BC, van de Geijn RA (2005) Parallel out-of-core computation and updating the QR factorization. ACM Trans Math Softw 31(1):60–78Joffrain T, Quintana-Ortí ES, van de Geijn RA (2004) Rapid development of high-performance out-of-core solvers. In: Applied Parallel Computing, State of the Art in Scientific Computing, 7th International Workshop, PARA 2004, Lyngby, Denmark, June 20–23, 2004, revised selected papers. pp 413–422NVIDIA. The cuBLAS library. http://docs.nvidia.com/cuda/cublas . Accessed May 2017Openblas. http://www.openblas.net . Accessed May 2017Quintana-Ortí G, Quintana-Ortí ES, Van De Geijn RA, Van Zee FG, Chan E (2009) Programming matrix algorithms-by-blocks for thread-level parallelism. ACM Trans Math Softw 36(3):14:1–14:26The OmpSs Programming Model. https://pm.bsc.es/ompss . Accessed May 2017Wende F, Steinke T, Cordes F (2014) Multi-threaded kernel offloading to gpgpu using hyper-q on kepler architecture. Technical Report 14-19, ZIB, Takustr.7, 14195 Berli

Administración de corticoides a los pacientes con sepsis grave y mejora de su mortalidad intrahospitalaria: Una revisión sistemática

Objective: To determine if there is scientific evidence to demonstrate a beneficial effect of corticosteroid treatment in patients with severe sepsis or septic shock. Also, to indicate the best clinical practice in the use of corticosteroids for the treatment of patients with severe sepsis or septic shock. We propose to determine the profile of the septic patient with critical illness that can benefit from the administration of corticosteroids for their treatment.Methodology: Search in databases of great evidence, establishing criteria of inclusion and exclusion to obtain a greater specificity of the subject. In the selection, the premises of the CASPe program were followed, and 9 articles were included in our systematic review.Results and conclusions: Most of the evidence shows that the administration of corticosteroids has a benefit in the reversion of shock, but does not decrease the mortality of patients. It was observed that patients who benefit from this type of treatment are those that are more critical, with APACHE II scores higher. On the other hand, the literature shows better results in relation to the benefit of this treatment, if it is started early in patients candidates for such treatment, and the best way to administer them is in a continuous infusion. A possible cause of the heterogeneity in the results regarding the benefits of corticosteroid administration could be related to a genetic variation, as shown by Schäfer et al.Objetivo: Averiguar si existe evidencia científica que demuestre un efecto beneficioso del tratamiento con corticoides en los pacientes con sepsis grave o shock séptico. También precisar la mejor práctica clínica en el uso de los corticoides para el tratamiento de los pacientes que presentan sepsis grave o shock séptico. Nos proponemos determinar el perfil del paciente séptico con enfermedad crítica que puede beneficiarse de la administración de corticoides para su tratamiento. Metodología: Búsqueda en bases de datos de gran evidencia, estableciendo unos criterios de inclusión y exclusión para obtener una mayor especificidad del tema. En la selección se siguieron las premisas del programa CASPe, y se incluyeron 9 artículos en nuestra revisión sistemática.Resultados y conclusiones: La mayoría de las evidencias muestran que la administración de corticoides presenta un beneficio en la reversión del shock, pero no disminuye la mortalidad de los pacientes. Se observó que los pacientes que se benefician de este tipo de tratamiento, son aquellos que están más críticos, con puntuaciones en la escala APACHE II más altas. Por otro lado, la bibliografía muestra unos mejores resultados en relación al beneficio de este tratamiento, si se inicia de una forma precoz en los pacientes candidatos a recibir dicho tratamiento, y la mejor forma de administrarlos es en bomba de perfusión continua. Una posible causa de la heterogeneidad en los resultados en cuanto a los beneficios de la administración de los corticoides, podría relacionarse con una variación genética, tal y como mostró Schäfer et al. &nbsp

On the progressive nature of grain crushing

In this work acoustic emission (AE) is used as experimental evidence of the progressive nature of grain crushing. Stress controlled high pressure oedometric compression test are carried out on 1.2 mm monodisperse samples of glass beads. It was observed that the granular assembly starts to experience particle breakage at a vertical stress of about 25MPa. When this yield pressure is exceeded the glass beads start to break emitting loud impulsive sound and the vertical displacement increases rapidly. The load was increased beyond the yield stress and at each increment while the vertical stress remained constant the sample continued to emit sound. The emission of sound at a constant vertical stress indicates that crushing is a progressive failure mechanism; once the first crushing event occurs, the structure starts to rearrange causing other crushing events to occur and additional settlement. In particular, two signal processing algorithms are used on the samples of the acoustic signal to obtain two additional metrics of the crushing evolution. The first is the cumulative energy versus time. The second is the number of crushing events versus time, which is based on the automatic detection of the peaks of the sound signal envelope. There is a clear correlation between the cumulative acoustic energy emitted and the observed sample displacement. Using laser scanning, the evolution of the particle size distribution and particle shape are measured in detail so that a link between the acoustic data and the crushing intensity is established. The crushing intensity was controlled using materials with different strengths

On the feasibility of personal audio systems over a network of distributed loudspeakers

Los sistemas de reproducción de audio personal se ocupan de la creación de zonas sonoras personales dentro de una habitación sin necesidad de utilizar auriculares. Estos sistemas utilizan un conjunto de altavoces y diseñan los filtros necesarios en cada altavoz con el fin de que la señal de audio deseada llegue a cada persona en la sala lo más libre de interferencias posible. Existen propuestas muy interesantes en la literatura que hacen uso de arrays circulares o lineales, pero en este trabajo estudiamos el problema considerando una red de altavoces distribuidos controlados por un conjunto de nodos acústicos, que pueden intercambiar información a través de una red. Enunciamos el modelo de un sistema distribuido de este tipo considerando los caminos electroacústicos entre los altavoces y cada micrófono, y tratamos de proporcionar una relación mínima de señal a interferencia-ruido (SINR) a cada zona, pero limitando la potencia emitida por los altavoces a un valor máximo (evitando los molestos efectos de retroalimentación). Para ello, utilizamos técnicas de optimización para decidir si, dada una distribución de los altavoces y una ubicación de las zonas de sonido personales dentro la sala, el sistema será viable. Se realizan simulaciones para para apoyar el uso de las técnicas de optimización propuestas.TEC2015-67387-C4-1-RPROMETEOII/ 2014/003Personal audio reproduction systems deal with the creation of personal sound zones within a room without the necessity of using headphones. These systems use an array of loudspeakers and design the required filters at each loudspeaker in order to render the desired audio signal to each person in the room as free of interferences as possible. There are very interesting proposals in the literature that make use of circular or linear arrays, but in this paper we study the problem considering a network of distributed loudspeakers controlled by a set of acoustic nodes, which can exchange information through a network. We state the model of such a distributed system by considering the electro-acoustic paths between the loudspeakers and each microphone, and try to provide a minimum signal-to-interference-and-noise ratio (SINR) to each zone, but constraining the emitted power of the loudspeakers to a maximum value (avoiding annoying feedback effects). We make use of optimization techniques to decide if, given a distribution of the loudspeakers and a location of the personal sound zones within the room, the system will be feasible. Simulations are done to support the use of the proposed optimization techniques