870 research outputs found
Multiplierless CSD techniques for high performance FPGA implementation of digital filters.
I leverage FastCSD to develop a new, high performance iterative multiplierless structure based on a novel real-time CSD recoding, so that more zero partial products are introduced. Up to 66.7% zero partial products occur compared to 50% in the traditional modified Booth's recoding. Also, this structure reduces the non-zero partial products to a minimum. As a result, the number of arithmetic operations in the carry-save structure is reduced. Thus, an overall speed-up, as well as low-power consumption can be achieved. Furthermore, because the proposed structure involves real time CSD recoding and does not require a fixed value for the multiplier input to be known a priori, the proposed multiplier can be applied to implement digital filters with non-fixed filter coefficients, such as adaptive filters.My work is based on a dramatic new technique for converting between 2's complement and CSD number systems, and results in high-performance structures that are particularly effective for implementing adaptive systems in reconfigurable logic.My research focus is on two key ideas for improving DSP performance: (1) Develop new high performance, efficient shift-add techniques ("multiplierless") to implement the multiply-add operations without the need for a traditional multiplier structure. (2) There is a growing trend toward design prototyping and even production in FPGAs as opposed to dedicated DSP processors or ASICs; leverage this trend synergistically with the new multiplierless structures to improve performance.Implementation of digital signal processing (DSP) algorithms in hardware, such as field programmable gate arrays (FPGAs), requires a large number of multipliers. Fast, low area multiply-adds have become critical in modern commercial and military DSP applications. In many contemporary real-time DSP and multimedia applications, system performance is severely impacted by the limitations of currently available speed, energy efficiency, and area requirement of an onboard silicon multiplier.I also introduce a new multi-input Canonical Signed Digit (CSD) multiplier unit, which requires fewer shift/add/subtract operations and reduced CSD number conversion overhead compared to existing techniques. This results in reduced power consumption and area requirements in the hardware implementation of DSP algorithms. Furthermore, because all the products are produced simultaneously, the multiplication speed and thus the throughput are improved. The multi-input multiplier unit is applied to implement digital filters with non-fixed filter coefficients, such as adaptive filters. The implementation cost of these digital filters can be further reduced by limiting the wordlength of the input signal with little or no sacrifice to the filter performance, which is confirmed by my simulation results. The proposed multiplier unit can also be applied to other DSP algorithms, such as digital filter banks or matrix and vector multiplications.Finally, the tradeoff between filter order and coefficient length in the design and implementation of high-performance filters in Field Programmable Gate Arrays (FPGAs) is discussed. Non-minimum order FIR filters are designed for implementation using Canonical Signed Digit (CSD) multiplierless implementation techniques. By increasing the filter order, the length of the coefficients can be decreased without reducing the filter performance. Thus, an overall hardware savings can be achieved.Adaptive system implementations require real-time conversion of coefficients to Canonical Signed Digit (CSD) or similar representations to benefit from multiplierless techniques for implementing filters. Multiplierless approaches are used to reduce the hardware and increase the throughput. This dissertation introduces the first non-iterative hardware algorithm to convert 2's complement numbers to their CSD representations (FastCSD) using a fixed number of shift and logic operations. As a result, the power consumption and area requirements required for hardware implementation of DSP algorithms in which the coefficients are not known a priori can be greatly reduced. Because all CSD digits are produced simultaneously, the conversion speed and thus the throughput are improved when compared to overlap-and-scan techniques such as Booth's recoding
High-level power optimisation for Digital Signal Processing in Recon gurable Logic
This thesis is concerned with the optimisation of Digital Signal Processing (DSP) algorithm
implementations on recon gurable hardware via the selection of appropriate word-lengths
for the signals in these algorithms, in order to minimise system power consumption. Whilst
existing word-length optimisation work has concentrated on the minimisation of the area of
algorithm implementations, this work introduces the rst set of power consumption models
that can be evaluated quickly enough to be used within the search of the enormous design
space of multiple word-length optimisation problems. These models achieve their speed by
estimating both the power consumed within the arithmetic components of an algorithm
and the power in the routing wires that connect these components, using only a high-level
description of the algorithm itself. Trading o a small reduction in power model accuracy
for a large increase in speed is one of the major contributions of this thesis.
In addition to the work on power consumption modelling, this thesis also develops a
new technique for selecting the appropriate word-lengths for an algorithm implementation
in order to minimise its cost in terms of power (or some other metric for which models
are available). The method developed is able to provide tight lower and upper bounds on
the optimal cost that can be obtained for a particular word-length optimisation problem
and can, as a result, nd provably near-optimal solutions to word-length optimisation
problems without resorting to an NP-hard search of the design space.
Finally the costs of systems optimised via the proposed technique are compared to
those obtainable by word-length optimisation for minimisation of other metrics (such as
logic area) and the results compared, providing greater insight into the nature of wordlength
optimisation problems and the extent of the improvements obtainable by them
High sample-rate Givens rotations for recursive least squares
The design of an application-specific integrated circuit of a parallel array processor is considered
for recursive least squares by QR decomposition using Givens rotations, applicable
in adaptive filtering and beamforming applications. Emphasis is on high sample-rate operation,
which, for this recursive algorithm, means that the time to perform arithmetic operations
is critical. The algorithm, architecture and arithmetic are considered in a single
integrated design procedure to achieve optimum results.
A realisation approach using standard arithmetic operators, add, multiply and divide is
adopted. The design of high-throughput operators with low delay is addressed for fixed- and
floating-point number formats, and the application of redundant arithmetic considered. New
redundant multiplier architectures are presented enabling reductions in area of up to 25%,
whilst maintaining low delay. A technique is presented enabling the use of a conventional
tree multiplier in recursive applications, allowing savings in area and delay. Two new divider
architectures are presented showing benefits compared with the radix-2 modified SRT algorithm.
Givens rotation algorithms are examined to determine their suitability for VLSI implementation.
A novel algorithm, based on the Squared Givens Rotation (SGR) algorithm, is developed
enabling the sample-rate to be increased by a factor of approximately 6 and offering
area reductions up to a factor of 2 over previous approaches. An estimated sample-rate of
136 MHz could be achieved using a standard cell approach and O.35pm CMOS technology.
The enhanced SGR algorithm has been compared with a CORDIC approach and shown to
benefit by a factor of 3 in area and over 11 in sample-rate. When compared with a recent implementation
on a parallel array of general purpose (GP) DSP chips, it is estimated that a single
application specific chip could offer up to 1,500 times the computation obtained from a
single OP DSP chip
Practical Non-Uniform Channelization for Multistandard Base Stations
A Multistandard software-defined radio base station must perform non-uniform channelization of multiplexed frequency bands. Non-uniform
channelization accounts for a significant portion of the digital signal processing workload in the base station receiver and can be difficult to realize in a physical
implementation. In non-uniform channelization methods based on generalized DFT filter banks, large prototype filter orders are a significant issue for
implementation. In this paper, a multistage filter design is applied to two different non-uniform generalized DFT-based channelizers in order to reduce their filter
orders. To evaluate the approach, a TETRA and TEDS base station is used. Experimental results show that the new multistage design reduces both the number
of coefficients and operations and leads to a more feasible design and practical physical implementation
Practical Non-Uniform Channelization for Multistandard Base Stations
A Multistandard software-defined radio base station must perform non-uniform channelization of multiplexed frequency bands. Non-uniform
channelization accounts for a significant portion of the digital signal processing workload in the base station receiver and can be difficult to realize in a physical
implementation. In non-uniform channelization methods based on generalized DFT filter banks, large prototype filter orders are a significant issue for
implementation. In this paper, a multistage filter design is applied to two different non-uniform generalized DFT-based channelizers in order to reduce their filter
orders. To evaluate the approach, a TETRA and TEDS base station is used. Experimental results show that the new multistage design reduces both the number
of coefficients and operations and leads to a more feasible design and practical physical implementation
PERFORMANCE IMPROVEMENT OF MULTICHANNEL AUDIO BY GRAPHICS PROCESSING UNITS
Multichannel acoustic signal processing has undergone major development
in recent years due to the increased complexity of current audio processing
applications. People want to collaborate through communication with the
feeling of being together and sharing the same environment, what is considered
as Immersive Audio Schemes. In this phenomenon, several acoustic
e ects are involved: 3D spatial sound, room compensation, crosstalk cancelation,
sound source localization, among others. However, high computing
capacity is required to achieve any of these e ects in a real large-scale system,
what represents a considerable limitation for real-time applications.
The increase of the computational capacity has been historically linked
to the number of transistors in a chip. However, nowadays the improvements
in the computational capacity are mainly given by increasing the
number of processing units, i.e expanding parallelism in computing. This
is the case of the Graphics Processing Units (GPUs), that own now thousands
of computing cores. GPUs were traditionally related to graphic or image
applications, but new releases in the GPU programming environments,
CUDA or OpenCL, allowed that most applications were computationally
accelerated in elds beyond graphics. This thesis aims to demonstrate
that GPUs are totally valid tools to carry out audio applications that require
high computational resources. To this end, di erent applications in
the eld of audio processing are studied and performed using GPUs. This
manuscript also analyzes and solves possible limitations in each GPU-based
implementation both from the acoustic point of view as from the computational
point of view. In this document, we have addressed the following
problems:
Most of audio applications are based on massive ltering. Thus, the
rst implementation to undertake is a fundamental operation in the audio
processing: the convolution. It has been rst developed as a computational
kernel and afterwards used for an application that combines multiples convolutions
concurrently: generalized crosstalk cancellation and equalization.
The proposed implementation can successfully manage two di erent and
common situations: size of bu ers that are much larger than the size of the
lters and size of bu ers that are much smaller than the size of the lters.
Two spatial audio applications that use the GPU as a co-processor have been developed from the massive multichannel ltering. First application
deals with binaural audio. Its main feature is that this application is able
to synthesize sound sources in spatial positions that are not included in the
database of HRTF and to generate smoothly movements of sound sources.
Both features were designed after di erent tests (objective and subjective).
The performance regarding number of sound source that could be rendered
in real time was assessed on GPUs with di erent GPU architectures. A
similar performance is measured in a Wave Field Synthesis system (second
spatial audio application) that is composed of 96 loudspeakers. The proposed
GPU-based implementation is able to reduce the room e ects during
the sound source rendering.
A well-known approach for sound source localization in noisy and reverberant
environments is also addressed on a multi-GPU system. This
is the case of the Steered Response Power with Phase Transform (SRPPHAT)
algorithm. Since localization accuracy can be improved by using
high-resolution spatial grids and a high number of microphones, accurate
acoustic localization systems require high computational power. The solutions
implemented in this thesis are evaluated both from localization and
from computational performance points of view, taking into account different
acoustic environments, and always from a real-time implementation
perspective.
Finally, This manuscript addresses also massive multichannel ltering
when the lters present an In nite Impulse Response (IIR). Two cases are
analyzed in this manuscript: 1) IIR lters composed of multiple secondorder
sections, and 2) IIR lters that presents an allpass response. Both
cases are used to develop and accelerate two di erent applications: 1) to
execute multiple Equalizations in a WFS system, and 2) to reduce the
dynamic range in an audio signal.Belloch RodrĂguez, JA. (2014). PERFORMANCE IMPROVEMENT OF MULTICHANNEL AUDIO BY GRAPHICS PROCESSING UNITS [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/40651TESISPremios Extraordinarios de tesis doctorale
Algorithms and architectures for the multirate additive synthesis of musical tones
In classical Additive Synthesis (AS), the output signal is the sum of a large number of independently controllable sinusoidal partials. The advantages of AS for music synthesis are well known as is the high computational cost. This thesis is concerned with the computational optimisation of AS by multirate DSP techniques. In note-based music synthesis, the expected bounds of the frequency trajectory of each partial in a finite lifecycle tone determine critical time-invariant partial-specific sample rates which are lower than the conventional rate (in excess of 40kHz) resulting in computational savings. Scheduling and interpolation (to suppress quantisation noise) for many sample rates is required, leading to the concept of Multirate Additive Synthesis (MAS) where these overheads are minimised by synthesis filterbanks which quantise the set of available sample rates. Alternative AS optimisations are also appraised. It is shown that a hierarchical interpretation of the QMF filterbank preserves AS generality and permits efficient context-specific adaptation of computation to required note dynamics. Practical QMF implementation and the modifications necessary for MAS are discussed. QMF transition widths can be logically excluded from the MAS paradigm, at a cost. Therefore a novel filterbank is evaluated where transition widths are physically excluded. Benchmarking of a hypothetical orchestral synthesis application provides a tentative quantitative analysis of the performance improvement of MAS over AS. The mapping of MAS into VLSI is opened by a review of sine computation techniques. Then the functional specification and high-level design of a conceptual MAS Coprocessor (MASC) is developed which functions with high autonomy in a loosely-coupled master- slave configuration with a Host CPU which executes filterbanks in software. Standard hardware optimisation techniques are used, such as pipelining, based upon the principle of an application-specific memory hierarchy which maximises MASC throughput
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