Method for interference suppression for TDMA and/or FDMA transmission

Abstract

Equalising methods for digital transmission, e.g. trellis-based methods, generally presuppose a disturbance caused by a white noise. In mobile radiotelephony or during cable transmission, an additional disturbance often occurs due to interference. Said additional disturbance must be taken into account during the design of the receiver in order to avoid a degradation. Interference can be cancelled by means of a pre-filtering process. Following said pre-treatment, an approximately white noise having low variance is apparent and a trellis-based equalization can then be carried out. According to the invention, the pre-filtering process is carried out by means of a structure which is modified in relation to prior art and in which projections on vectors having complex values when the channel pulse responses are sufficiently different. The invention principle can be applied both to antenna diversity and mono-reception. The sampling of the receiver signals can be carried out according to the cycle of the symbols and in a fractionally spaced manner. It can be proven that said structure can cancel interference especially well. The feedforward filters of a DFE comprising a feedback filter are especially suitable for the pre-filtering processes in the inventive structure. The adjustment thereof can be carried out, for example, by means of an LMS algorithm. The projections following the feedforward filtering processes are also to be taken into account during the optimization of the filters. On the whole, the inventive structure, combined with the ensuring equalization, enables better efficiency (lower error rate or tolerance of a lower ratio of useful signal power to interference power) to be achieved than with conventional methods.

Description

technical field [0001] The present invention relates to a digital data transmission method applied in, for example, a digital mobile communication system, or a digital transmission method for twisted pair wires. In particular, it relates to interference suppression methods for TDMA and / or FDMA transmissions which can be at least approximately described as pulse amplitude modulation and have an arbitrary number of receive antennas, where the complex-valued receive signal of at least one receive antenna is filtered with complex-valued coefficients filter to produce at least one output signal. Here, TDMA and FDMA refer to Time Division Multiple Access and Frequency Division Multiple Access, respectively. Furthermore, the invention relates to an interference suppression system for TDMA and / or FDMA transmission which can be described at least approximately as pulse amplitude modulation and with any number of receive antennas, wherein the complex-valued receive signal of at least o...

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