88 research outputs found
Efficient and Stable Algorithms to Extend Greville's Method to Partitioned Matrices Based on Inverse Cholesky Factorization
Greville's method has been utilized in (Broad Learn-ing System) BLS to
propose an effective and efficient incremental learning system without
retraining the whole network from the beginning. For a column-partitioned
matrix where the second part consists of p columns, Greville's method requires
p iterations to compute the pseudoinverse of the whole matrix from the
pseudoinverse of the first part. The incremental algorithms in BLS extend
Greville's method to compute the pseudoinverse of the whole matrix from the
pseudoinverse of the first part by just 1 iteration, which have neglected some
possible cases, and need further improvements in efficiency and numerical
stability. In this paper, we propose an efficient and numerical stable
algorithm from Greville's method, to compute the pseudoinverse of the whole
matrix from the pseudoinverse of the first part by just 1 iteration, where all
possible cases are considered, and the recently proposed inverse Cholesky
factorization can be applied to further reduce the computational complexity.
Finally, we give the whole algorithm for column-partitioned matrices in BLS. On
the other hand, we also give the proposed algorithm for row-partitioned
matrices in BLS
Two Ridge Solutions for the Incremental Broad Learning System on Added Nodes
The original Broad Learning System (BLS) on new added nodes and its existing
efficient implementation both assume the ridge parameter is near 0 in the ridge
inverse to approximate the generalized inverse, and compute the generalized
inverse solution for the output weights. In this paper, we propose two ridge
solutions for the output weights in the BLS on added nodes, where the ridge
parameter can be any positive real number. One of the proposed ridge solutions
computes the output weights from the inverse Cholesky factor, which is updated
by extending the existing inverse Cholesky factorization. The other proposed
ridge solution computes the output weights from the ridge inverse, and updates
the ridge inverse by extending the Greville method that can only computes the
generalized inverse of a partitioned matrix. The proposed BLS algorithm based
on the ridge inverse requires the same complexity as the original BLS
algorithm, while the proposed BLS algorithm based on the inverse Cholesky
factor requires less complexity and training time than the original BLS and the
existing efficient BLS. Both the proposed ridge solutions for BLS achieve the
same testing accuracy as the standard ridge solution in the numerical
experiments. The difference between the testing accuracy of the proposed ridge
solutions and that of the existing generalized inverse solutions is negligible
when the ridge parameter is very small, and becomes too big to be ignored when
the ridge parameter is not very small. When the ridge parameter is not near 0,
usually the proposed two ridge solutions for BLS achieve better testing
accuracy than the existing generalized inverse solutions for BLS, and then the
former are more preferred than the latter
Design and Implementation of an Universal Lattice Decoder on FPGA
In wireless communication, MIMO (multiple input multiple output) is one of the promising technologies which improves the range and performance of transmission without increasing the bandwidth, while providing high rates. High speed hardware MIMO decoders are one of the keys to apply this technology in applications. In order to support the high data rates, the underlying hardware must have significant processing capabilities. FPGA improves the speed of signal processing using parallelism and reconfigurability advantages. The objective of this thesis is to develop an efficient hardware architectural model for the universal lattice decoder and prototype it on FPGA. The original algorithm is modified to ensure the high data rate via taking the advantage of FPGA features. The simulation results of software, hardware are verified and the BER performance of both the algorithms is estimated. The system prototype of the decoder with 4-transmit and 4-receive antennas using a 4-PAM (Pulse amplitude modulation) supports 6.32 Mbit/s data rate for parallelpipeline implementation on FPGA platform, which is about two orders of magnitude faster than its DSP implementation
Combined data detection scheme for zero-padded OFDM signals in MMF links
© © 2015 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.In this letter, we propose a receiver scheme for zero-padded orthogonal frequency division multiplexing (OFDM) that combines low complexity from overlap-and-add equalizer and low error rate provided by successive interference cancellation data detection from optimal ordering vertical Bell Laboratories layered space-time (V-BLAST) architecture. Results of numerical simulations on multimode optical fiber links show that the proposed scheme improves the error rate performance of zero forcing (ZF) equalization receiver, reaching results similar to V-BLAST. For example, the proposed scheme can reach 33.9 Gb/s in a 600-m link, whereas the ZF receiver would reach 29.06 Gb/s and cyclic prefix OFDM only 19.37 Gb/s. These results are obtained with a reduction in computational complexity (measured in number of real products) of 86% in detection and 66% in preprocessing with respect to the ZF receiver, and 75% and 97% with respect to the V-BLAST receiver.Manuscript received May 6, 2015; accepted May 24, 2015. Date of publication June 1, 2015; date of current version July 10, 2015. This work was supported by the Spanish Ministerio de Economia y Competitividad under Project TEC2012-38558-C02-02 and Project TEC2012-38558-C02-01, both with FEDER funds. The work of P. Medina was supported by the Formacion de Personal Investigador Grant Program of the Universitat Politecnica de Valencia.Medina Sevila, P.; Almenar Terré, V.; Corral, JL. (2015). Combined data detection scheme for zero-padded OFDM signals in MMF links. IEEE Photonics Technology Letters. 27(16):1753-1756. https://doi.org/10.1109/LPT.2015.2439158S17531756271
Efficient detection algorithms for Multiple-Input Multiple-Output (MIMO) systems
[EN] In the last ten years, one of the most significant technological developments that will lead to the
new broadband wireless generation is the communication via Multiple-Input Multiple-Output
(MIMO) systems. MIMO systems are known to provide an increase of the maximum rate, reliability
and coverage of current wireless communications. Maximum-Likelihood (detection over
Gaussian MIMO channels is shown to get the lowest Bit Error Rate for a given scenario. However,
it has a prohibitive complexity which grows exponentially with the number of transmit
antennas and the size of the constellation. Motivated by this, there is a continuous search for
computationally efficient optimal or suboptimal detectors.
In this work, we carry out an state of the art review of detection algorithms and propose the
combination of a suboptimal MIMO detector called K-Best Sphere Decoder with a channel
matrix condition number estimator to obtain a versatile combined detector with predictable
performance and suitable for hardware implementation. The effect of the channel matrix condition
number in data detection is exploited in order to achieve a decoding complexity lower
than the one of already proposed algorithms with similar performance. Some practical algorithms
for finding the 2-norm condition number of a given channel matrix and for performing
the threshold selection are also presented and their computational costs and accuracy are discussed[ES] Uno de los desarrollos tecnol'ogicos m'as significativos de la ' ultima d'ecada que llevar'an a la
nueva generaci'on de banda ancha en movilidad es la comunicaci'on mediante sistemas de
m' ultiples entradas y m' ultiples salidas (MIMO). Los sistemas MIMO proporcionan un notable
incremento en la capacidad, fiabilidad y cobertura de las comunicaciones inal'ambricas actuales.
Se puede demostrar que la detecci'on 'optima o dem'axima verosimilitud (ML) en canales
MIMO Gaussianos proporciona la m'¿nima tasa de error de bit (BER) para un escenario dado
pero tiene el inconveniente de que su complejidad crece exponencialmente con el n'umero de
antenas y el tama¿no de la constelaci'on utilizada. Por este motivo, hay una cont'¿nua b' usqueda
de detectores 'optimos o sub'optimos que sean m'as eficientes computacionalmente.
En este trabajo, se ha llevado a cabo una revisi 'on del estado del arte de los principales algoritmos
de detecci'on para sistemas MIMO y se ha propuesto la combinaci'on de un detector MIMO
sub'optimo conocido como K-Best Sphere Decoder con un estimador del n'umero de condici'on de
la matriz de canal, para conseguir un detector combinado basado en umbral con complejidad
predecible y adecuado para implementaci'on en hardware. Se ha explotado el efecto del n'umero
de condici'on en la detecci'on de datos para disminuir la complejidad de los algoritmos de detecci
'on existentes sin apenas alterar sus prestaciones. Por ' ultimo tambi'en se presentan distintos
algoritmos pr'acticos para encontrar el dos n'umero de condici'on as'¿ como para realizar la selecci
'on del umbral.Roger Varea, S. (2008). Efficient detection algorithms for Multiple-Input Multiple-Output (MIMO) systems. http://hdl.handle.net/10251/12200Archivo delegad
Improved Recursive Algorithms for V-BLAST to Reduce the Complexity and Save Memories
Improvements I-IV were proposed to reduce the computational complexity of the
original recursive algorithm for vertical Bell Laboratories layered space-time
architecture (VBLAST). The existing recursive algorithm with speed advantage
and that with memory saving incorporate Improvements I-IV and only Improvements
III-IV into the original algorithm, respectively. To the best of our knowledge,
the algorithm with speed advantage and that with memory saving require the
lowest complexity and the least memories, respectively, among the existing
recursive V-BLAST algorithms.
We propose Improvements V and VI to replace Improvements I and II,
respectively. Instead of the lemma for inversion of partitioned matrix applied
in Improvement I, Improvement V uses another lemma to speed up the matrix
inversion step by the factor of 1.67. Then the formulas adopted in our
Improvement V are applied to deduce Improvement VI, which includes the improved
interference cancellation scheme with memory saving. In the existing algorithm
with speed advantage, the proposed algorithm I with speed advantage replaces
Improvement I with Improvement V, while the proposed algorithm II with both
speed advantage and memory saving replaces Improvements I and II with
Improvements V and VI, respectively. Both proposed algorithms speed up the
existing algorithm with speed advantage by the factor of 1.3, while the
proposed algorithm II achieves the speedup of 1.86 and saves about half
memories, compared to the existing algorithm with memory saving
- …