Joachim Speidel

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Abstract– A time domain equalization technique to be used in an Orthogonal Frequency Division Multiplex (OFDM) or Discrete Multi Tone (DMT) system is proposed, which directly minimizes the delay spread of the overall channel impulse response (CIR). It will be shown that this technique can provide superior performance compared to recent developments of(More)
In this paper an adaptive channel estimator is proposed and investigated to improve the performance of the receiver for pilot aided wireless and mobile OFDM systems. The estimator consists of a two-dimensional Wiener filter which is implemented as a cascade of two one-dimensional filters. We propose an efficient algorithm for adaptation to time varying(More)
In this letter, we investigate two iterative channel estimators for mobile orthogonal-frequency division multiplexing. The first estimator is based on iterative filtering and decoding whereas the second one uses an a posteriori probability (APP) algorithm. The first method consists of two cascaded one-dimensional Wiener filters, which interpolate the(More)
We propose and analyze a generalized spatial modulation scheme, where depending on the bits to be transmitted a certain data symbol as well as a certain beamforming vector is chosen. The receiver then has to estimate both the used beamforming vector and the transmitted data symbol for being able to reconstruct the originally transmitted bit sequence. We(More)
We present a low complexity encoder and mapper for wireless multiple-input multiple-output (MIMO) systems. The BLAST (Bell Laboratories Layered Space-Time) algorithm is enhanced by a dedicated iterative QAM demapper with antiGray code. At the the transmitter a low complexity convolutional encoder and a QAM mapper with anti-Gray code are used, whose EXIT(More)
Recently, the authors proposed statistical prefilters for MMSE and ZF receivers that minimize SER (Kiessling, M. et al., IEEE WCNC, 2003; IEEE VTC, 2003). We now give a general derivation of their structure based on majorization theory. For both receiver types, it is shown that the optimal prefilter essentially transmits on the strongest long-term(More)
In this paper we present a novel and computationally efficient waterfilling algorithm for multiuser OFDM. This algorithm is based on the multiuser waterfilling theorem and determines the subcarrier allocation for a multiple access OFDM system. This approach maximizes the total bitrate under the constraints of user-individual power budgets. Once the(More)