Telefonaktiebolaget Lm Ericsson (Publ)

Lars Björkman

Leif Wilhelmsson

Fredrik Nordström

Bo Magnus Bernhardsson

Methods for positioning an FFT-window in an OFDM-receiver are disclosed as well as electronic apparatuses and computer program products for performing the methods. The method comprises determining a position of the FFT-window in relation to one or more OFDM-symbols of a received OFDM-signal, using the position of the FFT-window to obtain a first OFDM-symbol from the received OFDM-signal, and applying an FFT to the first OFDM-symbol to produce an FFT-output signal. The method also comprises determining a frequency dependent phase rotation component of the FFT-output signal, and removing the determined frequency dependent phase rotation component from the FFT-output signal to obtain a compensated FFT-output signal. A delay spread estimate is calculated based on at least one of the FFT-output signal and the compensated FFT-output signal, and the position of the FFT-window is adjusted based on at least the determined frequency dependent phase rotation component and the calculated delay spread estimate.

Method and apparatus for positioning an FFT-window in an OFDM-receiver

Methods for calculating a delay spread estimate in an OFDM-receiver are described, along with computer program products and electronic apparatuses for performing the methods. The methods comprise determining a position of an FFT-window in relation to one or more OFDM-symbols of a received OFDM-signal and using the determined position to obtain a first OFDM-symbol from the received OFDM-signal. An FFT is applied to the first OFDM-symbol to produce an FFT-output signal. A frequency dependent phase rotation component of the FFT-output signal is determined and removed from the FFT-output signal. A number of zero-crossings of at least one of a real component and an imaginary component of a transfer function of a channel, over which the received OFDM-signal has been transmitted, derived from the FFT-output signal where the frequency dependent phase rotation component has been removed is determined, and a delay spread estimate is calculated based on the determined number of zero-crossings.

Growing community of inventors

Malmö, Sweden

Lars Björkman