Browsing by Author "Hadaschik, Niels"

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    Measurement matrix design for compressed sensing based time delay estimation
    (IEEE, 2016) Roemer, Florian; Ibrahim, Mohamed; Franke, Norbert; Hadaschik, Niels; Eidloth, Andreas; Sackenreuter, Benjamin; Del Galdo, Giovanni
    In this paper we study the problem of estimating the unknown delay(s) in a system where we receive a linear combination of several delayed copies of a known transmitted waveform. This problem arises in many applications such as timing-based localization or wireless synchronization. Since accurate delay estimation requires wideband signals, traditional systems need high-speed AD converters which poses a significant burden on the hardware implementation. Compressive sensing (CS) based system architectures that take measurements at rates significantly below the Nyquist rate and yet achieve accurate delay estimation have been proposed with the goal to alleviate the hardware complexity. In this paper, we particularly discuss the design of the measurement kernels based on a frequency-domain representation and show numerically that an optimized choice can outperform randomly chosen functionals in terms of the delay estimation accuracy.
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    Temporal wireless synchronization with compressed opportunistic signals
    (IEEE, 2016) Ibrahim, Mohamed; Roemer, Florian; Hadaschik, Niels; Tröger, Hans-Martin; Sackenreuter, Benjamin; Franke, Norbert; Robert, Joerg; Del Galdo, Giovanni
    In this paper we introduce a wireless temporal synchronization scheme based on wideband signals of opportunity (SOO) such as DVB-T or LTE signals. Since these signals may not be decodable we show that it is necessary that one (reference) node broadcasts an excerpt of the SOO to all other nodes to provide a reference. However, the transmission of this reference signals requires a high bandwidth. Therefore, we propose to replace this transmission with a lower-bandwidth “compressed” version of this reference signal, using ideas from the field of compressed sensing (CS). We show that the high time resolution of the original wideband SOO can be maintained so that accurate temporal synchronization is possible. On the other hand, the compression leads to higher sidelobes in the correlation function which reduces the effective SNR. Therefore, the compression rate allows to control the trade-off between the required bandwidth and the SNR.