We consider orthogonal frequency-division multiplexing systems with intercarrier interference (ICI) due to insufficient cyclic prefix and/or temporal variations Intersymbol interference (ISI) and ICI lead to an error floor in conventional receivers We suggest two techniques for the equalization of ICI The first, called "operator-perturbation technique" is an iterative technique for the inversion of a linear system of equations Alternatively, we show that serial or parallel interference cancellation can be used to drastically reduce the error floor Simulations show that, depending on the SNR and the origin of the ICI, one of the schemes performs best In all cases, our schemes lead to a drastic reduction of the bit error rate

Iterative Methods for Cancellation of Intercarrier Interference in OFDM Systems

This letter describes an improved method to mitigate interference when the cyclic prefix is not sufficient for coded orthogonal frequency-division multiplexing (OFDM) systems. The proposed method, based on the residual intersymbol interference cancellation (RISIC), efficiently restores the cyclicity of the ith received symbol by adding the weighted (i+1)th received symbol to the ith received symbol. Simulation results show that the proposed scheme outperforms the conventional RISIC in the symbol error rate even when the channel impulse response is longer than a half of the symbol duration.

Efficient cyclic prefix reconstruction for coded OFDM systems

We consider the problem of mitigating narrowband interference (NBI) in conventional orthogonal frequency-division multiplexing (OFDM) systems, wherein the presence of the NBI dramatically degrades the performances of both the linear zero-forcing and minimum mean-square error equalizers. A new receiver based on successive NBI cancellation is synthesized, which is capable of assuring good NBI rejection, without requiring insertion of additional redundancy in the OFDM signal

Successive narrowband interference cancellation for OFDM systems

A method reduces noise in a multiple carrier modulated (MCM) signal. Such a method may include: estimating impulse noise based in the equalized signal; and removing a portion of the noise in the equalized signal as a function of the estimated impulse noise. An apparatus reduces noise in the MCM. Such an apparatus may include: a down-converter; an analog to digital converter to digitize the output of the down-converter; a guard-interval removing unit operable upon the digitized output of the down-converter; and a combined FFT, equalization and impulse-noise-compensation unit operable upon a signal from the guard-interval-removing unit.

Impulse noise reduction to an MCM signal

In this paper, spatial modulation (SM)-orthogonal frequency division multiplexing is introduced to massive multi-input multi-output high speed train systems to reduce the complexity of the receiver. First, the mathematic model of signal detection in frequency domain is formed as a compressive sensing (CS) problem. Based on this model, a novel detector, which exploits the unique group sparsity of the signal, is proposed to improve the accuracy of the nonzero elements localization. On the basis of the channel matrix decomposition, the detector combines the CS algorithms and the iteration process together to overcome the performance deterioration brought by inter-carrier interference. Moreover, theoretical analysis about the performance gain guarantee of our proposed detector is conducted and the complexity of the proposed detector is compared with the related works. Furthermore, we also extend our proposed detector into the special scenario that the train passes the overlapped area of the adjacent two cells and receives the superimposed signal. In order to deal with the inter-cell interference, a generalized SM framework is adopted to model the signal detection. Simulation results verify that the proposed detectors have an apparent performance gain compared to the conventional CS schemes with the same complexity order.

Compressive Sensing-Based Detector Design for SM-OFDM Massive MIMO High Speed Train Systems

Intercarrier interference can be a dominant source of errors in OFDM-systems, requiring some sort of equalization. We show that serial and parallel interference cancellation techniques, which were originally developed for CDMA multiuser techniques, can be used for OFDM equalization and are much more efficient than a brute force inversion of the channel matrix. Maximum excess delays of up to 70% of the OFDM block duration can be handled without loss of performance.

A.F. Molisch

Papers

Equalization of OFDM-systems by interference cancellation techniques