7006061
Iterative extrapolation algorithm for data reconstruction over sphere
Given limited or incomplete measurement data on a sphere, a new iterative algorithm is proposed on how to extrapolate signal over the whole sphere. The algorithm is based on a priori assumption that the Fourier decomposition of the signal on the sphere has finite degree of spherical harmonic coefficients, that is, the signal is mode limited. The algorithm is a simple iteration involving only the spherical harmonic decomposition. It is proven that the algorithm converges to the original signal over observation region and the convergence rate is lower bounded by the largest eigenvalue of an associated Fredholm integral equation.
16445226
Modal expansion of HRTFs: Continuous representation in frequency-range-angle
This paper proposes a continuous HRTF representation in both 3D spatial and frequency domains. The method is based on the acoustic reciprocity principle and a modal expansion of the wave equation solution to represent the HRTF variations with different variables in separate basis functions. The derived spatial basis modes can achieve HRTF near-field and far-field representation in one formulation. The HRTF frequency components are expanded using Fourier Spherical Bessel series for compact representation. The proposed model can be used to reconstruct HRTFs at any arbitrary position in space and at any frequency point from a finite number of measurements. Analytical simulated and measured HRTFs from a KEMAR are used to validate the model.
1223138
Efficient Continuous HRTF Model Using Data Independent Basis Functions: Experimentally Guided Approach
This paper introduces a continuous functional model for head-related transfer functions (HRTFs) in the horizontal auditory scene. The approach uses a separable representation consisting of a Fourier-Bessel series expansion for the spectral components and a conventional Fourier series expansion for the spatial components. Being independent of the data, these two sets of basis functions remain unchanged for all subjects and measurement setups. Hence, the model can transform an individualized HRTF to a subject specific set of coefficients. A continuous functional model is also developed in the time domain. We show the efficient model performance in approximating experimental measurements by using the HRTF measurements from a KEMAR manikin and the synthetic data from the spherical head model. The statistical results are determined from a 50-subject HRTF data set. We also corroborate the predictive capability of the proposed model. The model has near optimal performance, which can be ascertained by comparison with the standard principle component analysis (PCA) and discrete Karhunen-Loeve expansion (KLE) methods at the measurement points and for a given number of parameters.
12929858
UWB Spatia - Frequency Channel Characterization
This paper investigates the spatial-frequency channel characterization of ultra-wideband (UWB) wireless communication systems. First, a novel frequency dependent UWB channel model is constructed based on the theory of electromagnetic diffraction mechanism, which causes the field strength to vary with the frequency in each multipath. Then, we build a space-frequency model, which includes spatial characteristics such as angular power spectrum, and physical sampling points in space. The space-frequency model has two special cases (i) discrete multipath model, and (ii) cluster model, which can be readily used to generate channel data for any arbitrary set of sensor locations. The reconstruction results from channel measurements show the accurateness of the novel frequency dependent model, with reconstruction error decreasing by 40%, compared to the traditional Turin model
9935868
Reducing instruction cache energy consumption using a compiler-based strategy
Excessive power consumption is widely considered as a major impediment to designing future microprocessors. With the continued scaling down of threshold voltages, the power consumed due to leaky memory cells in on-chip caches will constitute a significant portion of the processor's power budget. This work focuses on reducing the leakage energy consumed in the instruction cache using a compiler-directed approach.We present and analyze two compiler-based strategies termed as conservative and optimistic. The conservative approach does not put a cache line into a low leakage mode until it is certain that the current instruction in it is dead. On the other hand, the optimistic approach places a cache line in low leakage mode if it detects that the next access to the instruction will occur only after a long gap. We evaluate different optimization alternatives by combining the compiler strategies with state-preserving and state-destroying leakage control mechanisms. We also evaluate the sensitivity of these optimizations to different high-level compiler transformations, energy parameters, and soft errors.
12152152
Interprocedural optimizations for improving data cache performance of array-intensive embedded applications
As datasets processed by embedded processors increase in size and complexity, the management of higher levels of memory hierarchy (e.g., caches) is becoming an important issue. A major limitation of most of the cache locality optimization techniques proposed by previous research is that they handle a single procedure at a time. This prevents compilers from capturing the data access interactions between procedures and may result in poor performance. In this paper, we look at loop and data transformations from a different angle and use them in an interprocedural optimization framework. Employing the call graph representation of a given application, the proposed technique visits each node of this graph twice and uses loop and data transformations in a systematic way for optimizing array layouts whole program wide. Our experimental results show that this interprocedural locality optimization strategy is much more effective than the previous locality-based techniques that handle each procedure in isolation.
61988520
Exploiting VLIW schedule slacks for dynamic and leakage energy reduction
The mobile computing device market is projected to grow to 16.8 million units in 2004, representing an average annual growth rate of 28% over the five year forecast period. This brings the technologies that optimize system energy to the forefront. As circuits continue to scale in future, it would be important to optimize both leakage and dynamic energy. Effective optimization of leakage and dynamic energy consumption requires a vertical integration of techniques spanning from circuit to software levels. Schedule stacks in codes executing in VLIW architectures present an opportunity for such an integration. In this paper, we present compiler-directed techniques that take advantage of schedule slacks to optimize leakage and dynamic energy consumption. The proposed techniques have been incorporated into a cycle accurate simulator using parameters extracted from circuit level simulation. Our results show that a unified scheme that uses both dynamic and leakage energy reduction techniques is effective in reducing energy consumption.
42476129
Reducing Instruction Translation Look-Aside Buffer Energy Through Compiler-Directed Resizing
A check valve is positioned in the pneumatic power system of a vehicle in which air is supplied to a pneumatic compressor from an induction manifold of an engine. The compressor has an oil sump, a start and stop clutch, an air inlet, and an air outlet. A check valve is emplaced in the air inlet conduit leading from the engine manifold to the compressor to provide a one-way flow of air into the compressor when the compressor is running and to block the conduit in response to a vacuum created therein and prevent the vacuum from reaching the compressor when the compressor is not running. The valve prevents oil from the compressor sump from being drawn into the pneumatic system and fouling air actuated devices.