Method for compensation of information losses in an OFDM-based multi-carrier communication signal caused by blanking out pulse-shaped interferences

1. A method for compensation of information losses caused by blanking out pulse-shaped interferences, in a communication signal received by a receiver, wherein, in said method,

the receiver receives a modulated OFDM-based multi-carrier signal comprising an overlap of a sequence of a predetermined number of subcarrier signals whose frequencies differ from each other by a constant amount and which have substantially no signal portions at the frequencies of the respective other subcarrier signals, with pulse-shaped interference signals, wherein complex data symbols are transmitted on each subcarrier,

the pulse-shaped interference signals are eliminated in the receiver by pulse blanking in that the interfering pulses are first detected and then the modulated time domain signal is set to zero at the points affected by the pulse-shaped interference,

the thus obtained signal, when represented by way in the frequency domain, is characterized in that the signal portions at each subcarrier frequency consist of an overlap of determinable signal portions respectively of all other subcarrier signals, and therefore inter-carrier interference (ICI) occurs, and

from the respective signal portion at a subcarrier frequency, those determinable signal portions are subtracted in the frequency do-main which result from the subcarrier signals of all other subcarriers and are reconstructed from an estimation of the complex data symbols transmitted on each subcarrier, an estimation of the influence of the transmission channel on each subcarrier and knowledge on the position and number of the points affected by the pulse-shaped interference, where pulse blanking has been applied,

the estimates for the complex data symbols are obtained by detecting and decoding the received equalized complex symbols and encoding and modulating them again and estimates of the channel coefficients are obtained from channel estimation, and

the signal where the undesired signal portions of all other subcarrier signals, namely ICI, have been partly compensated is processed in the same way in further iterations in order to improve the estimates of data symbols and channel coefficients and thereby, the information losses caused by blanking out the pulse-shaped interferences are compensated for.

2. The method according to claim 1 , wherein complex data symbols are modulated on the subcarrier frequencies and, in the receiver, the transmitted sequence of data symbols is iteratively determined by first detecting and decoding the sequence of the received data on the subcarriers, then coding said sequence again and modulating the sequence, for use as estimated values for the complex data symbol, onto the subcarrier frequencies, wherein these estimated values are used during the process of compensating for the influence of the blanking of the pulse-shaped interferences.

3. The method according to claim 1 , wherein the received communication signal represents an overlap of, on the one hand, a pulse-shaped signal of a system for distance and/or position determination of an aircraft, particularly such a system of the ground-based type, and respectively, a radio system for data transmission, particularly such a system of the military type, and, on the other hand, an OFDM-based signal.

4. The method according to claim 3 , wherein the signal of said ground-based system for distance and/or position determination of an air-craft, is a DME/TACAN signal or a JTIDS/MIDS signal with a plurality of frequency channels, the OFDM-based signal being positioned between the center frequencies of adjacent frequency channels or onto the center frequencies of said DME/TACAN and respectively JTIDS/MIDS signal.