Daniel Bielefeld

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The interplay between signal processing and wireless networking plays a crucial role in sensor networks deployed for detection and estimation applications. In this paper, an opportunistic power assignment strategy for IR-UWB sensor networks is presented which is designed to optimize detection performance in terms of the global probability of error. The(More)
Analyses by anion exchange chromatography indicate that heparan sulfate proteoglycans isolated from the livers of experimentally diabetic rats have a reduced net negative charge as compared with heparan sulfate proteoglycans from control rats. In contrast, the size of the normal and diabetic proteoglycans are indistinguishable as are the size of individual(More)
The limited energy of sensor nodes in wireless sensor networks strongly recommends power-aware design methodologies. In this paper, a power-aware sensor selection strategy for wireless sensor networks is presented that is especially designed for distributed detection with soft decision fusion. The objective is to minimize the global probability of error at(More)
Adaptive modulation of subcarriers for orthogonal frequency division multiplexing (OFDM) has been shown to improve system performance significantly. As a prerequisite, accurate channel state information (CSI) must be available at the transmitter. For time varying, noisy channels, however, this is difficult to achieve in practical systems. In this paper, we(More)
A low-cost deployment of wireless sensor networks heavily depends on the availability of low-complexity sensor nodes. In this paper, a sensor network with simple transmit-only IR-UWB sensor nodes is analyzed, that is deployed for distributed detection of signals in a region of interest. The nodes transmit their local decisions with a fixed transmission(More)
The reliable detection of unused spectrum while meeting a required probability of detecting primary user activity is a key functionality of cognitive radio systems. In cooperative spectrum sensing, the detection results of multiple cognitive radios are combined to a global result with high reliability. In order to transmit the local decisions a signaling(More)
Several attractive features of ultra wideband (UWB) communications make it a good candidate for physical-layer of wireless sensor networks (WSN). These features include low power consumption, low complexity and low cost of implementation. In this paper, we present an opportunistic power assignment strategy for distributed detection in parallel fusion WSNs,(More)
The frequency selectivity of wireless communication channels can be characterized by the delay spread Ds of the channel impulse response. If the delay spread is small compared to the bandwidth W of the input signal, that is, DsW ≈ 1, the channel appears to be flat fading. For DsW ≫ 1, the channel appears to be frequency selective, which is usually the case(More)
Least square and minimum mean square error data estimation based on rectangular and circulant channel submatrices is compared in terms of estimation quality, storage requirements and the number of multiplications. The circulant case is applied in OFDM based transmission systems. When applying an approximated Cholesky decomposition, the computation of the(More)