H. Elders-Boll

Bio: H. Elders-Boll is an academic researcher from Cologne University of Applied Sciences. The author has contributed to research in topics: Single antenna interference cancellation & Spread spectrum. The author has an hindex of 11, co-authored 28 publications receiving 368 citations. Previous affiliations of H. Elders-Boll include RWTH Aachen University & Synopsys.

Efficient differentially coherent code/Doppler acquisition of weak GPS signals

Abstract: Differentially coherent combining of correlation results is proposed for the acquisition of weak GPS signals, i.e. signals down to -147 dBm received power. It is shown that, with a combined coherent/differentially coherent acquisition scheme, GPS signals can be acquired in 200 msec without any assistance data. By complementing the proposed scheme with methods to estimate the fractional delay, the acquisition unit can provide high quality Doppler and delay estimates such that additional tracking units seem obsolete. Since the need for a complex FFT post-processing of correlation results is avoided, the proposed scheme offers an efficient way of implementing a rapid acquisition GPS receiver in hardware.

Efficient implementation of linear multiuser detectors for asynchronous CDMA systems by linear interference cancellation

Abstract: The decorrelating and the linear, minimum mean-squared error (MMSE) detector for asynchronous code-division multiple-access communications are ideally infinite memory-length detectors. Finite memory approximations of these detectors require the inversion of a correlation matrix whose dimension is given by the product of the number of active users and the length of the processing window. With increasing number of active users or increasing length of the processing window, the calculation of the inverse may soon become numerically very expensive. In this paper, we prove that the decorrelating and the linear MMSE detector can both be realized by linear multistage interference cancellation algorithms with ideally an infinite number of stages. It will be shown that depending on the signal-to-noise ratio, the number of active users, and the choice of the cancellation algorithm, only a few stages are necessary to obtain the same BER performance as with the ideal detectors. The computational costs for one stage of a linear interference cancellation algorithm are essentially given by one matrix-vector multiplication. Thus, the computational complexity can be reduced considerably. Since each stage introduces a time delay equivalent to the bit duration, the number of stages also determines the detection delay. Because a few stages are sufficient, this approach can also be used to obtain receiver structures with low memory consumption and detection delay.

Coded aperture imaging with multiple measurements

Abstract: In coded aperture imaging, only aperture arrays consisting of (0, 1) elements are physically realizable. If multiple coded images are obtained with different aperture masks and the resulting detector images are suitably combined, a larger variety of aperture arrays, such as multilevel, complex-valued, vector-valued, or complementary arrays becomes applicable. We present a general theory of coded aperture imaging with multiple measurements. An image reconstruction scheme from the coded images is described that results in a maximum signal-to-noise ratio. Also, the design of sets of aperture arrays is addressed and explicitly solved for several important cases. It is shown how known classes of correlation arrays can be beneficially applied to coded aperture imaging.

Adaptive multi-rate multi-code CDMA systems

Abstract: To support variable data-rates multi-code code-division multiple-access (MC-CDMA) systems have been proposed for mobile communications. They allow the support of variable source data-rates by variation of the set of spreading-sequences assigned to each user. The impact of the sequence-design on the system performance is considered. For the antifading capability and the multiuser interference performance measures are derived. We describe sequence-sets which are almost optimum with respect to these parameters and which allow each user to change its data-rate without affecting the other users.

Combinatorial design of near-optimum masks for coded aperture imaging

Abstract: In coded aperture imaging the attainable quality of the reconstructed images strongly depends on the choice of the aperture pattern. Optimum mask patterns can be designed from binary arrays with constant sidelobes of their periodic autocorrelation function, the so-called URAs. However, URAs exist for a restricted number of aperture sizes and open fractions only. Using a mismatched filter decoding scheme, artifact-free reconstructions can be obtained even if the aperture array violates the URA condition. A general expression and an upper bound for the signal-to-noise ratio as a function of the aperture array and the relative detector noise level are derived. Combinatorial optimization algorithms, such as the great deluge algorithm, are employed for the design of near-optimum aperture arrays. The signal-to-noise ratio of the reconstructions is predicted to be only slightly inferior to the URA case while no restrictions with respect to the aperture size or open fraction are imposed.

Random Matrix Theory and Wireless Communications

Abstract: Random matrix theory has found many applications in physics, statistics and engineering since its inception. Although early developments were motivated by practical experimental problems, random matrices are now used in fields as diverse as Riemann hypothesis, stochastic differential equations, condensed matter physics, statistical physics, chaotic systems, numerical linear algebra, neural networks, multivariate statistics, information theory, signal processing and small-world networks. This article provides a tutorial on random matrices which provides an overview of the theory and brings together in one source the most significant results recently obtained. Furthermore, the application of random matrix theory to the fundamental limits of wireless communication channels is described in depth.

Adaptive receiver structures for asynchronous CDMA systems

Abstract: Adaptive linear and decision feedback receiver structures for coherent demodulation in asynchronous code division multiple access (CDMA) systems are considered. It is assumed that the adaptive receiver has no knowledge of the signature waveforms and timing of other users. The receiver is trained by a known training sequence prior to data transmission and continuously adjusted by an adaptive algorithm during data transmission. The proposed linear receiver is as simple as a standard single-user detector receiver consisting of a matched filter with constant coefficients, but achieves essential advantages with respect to timing recovery, multiple access interference elimination, near/far effect, narrowband and frequency-selective fading interference suppression, and user privacy

Quadrature Amplitude Modulation: From Basics to Adaptive Trellis-Coded, Turbo-Equalised and Space-Time Coded OFDM, CDMA and MC-CDMA Systems

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Sensor system for identifying and tracking movements of multiple sources

Abstract: One embodiment of the present invention is a system for identifying a human being from movement of the human being. The system includes a dual element pyroelectric detector, a Fresnel lens array, and a processor. The dual element pyroelectric detector detects radiation from the human being as the human being moves over time. The Fresnel lens array is located between the dual element pyroelectric detector and the human being. The Fresnel lens array improves collection efficiency and spatial resolution of the dual element pyroelectric detector. The Fresnel lens array includes a mask. The mask provides at least one zone of visibility. The processor is coupled to the dual element pyroelectric detector, the processor converts the detected radiation to a spectral radiation signature. The processor compares the spectral radiation signature to at least a second spectral radiation signature to identify the human being.

Linear interference cancellation in CDMA based on iterative techniques for linear equation systems

Abstract: It has previously been shown that well known iterations for solving a set of linear equations correspond to linear interference cancellation structures. Here, we suggest applying a block-wise iteration that consists of an outer and an inner iteration. The outer iteration used is the Gauss-Seidel (GS) method, while for the inner iteration, we study direct matrix inversion, the Jacobi over-relaxation iteration, and the conjugate gradient iteration. When a true inner iteration is used, this approach allows for a timely derivation of the acceleration parameters required by advanced iterations. The block iteration is based on a symbol-level implementation which leads to the same detection delay profile for both parallel and serial structures at the expense of differences in the amount of serial processing required. This is discussed in some detail and quantified for comparison. The performance of the detectors is studied via computer simulations where it is found that the block approach can provide significantly faster convergence, leading to improved detection delay over the simpler GS iteration. The improvements are obtained at the expense of an increase in the required serial processing speed.