Adaptive beamforming for interference rejection in an OFDM system

Abstract

Orthogonal frequency-division multiplexing . (OFDM) has been utilized in various communication sysfems because of its ability to compensate for niultipath channels using simple low-complexity equalizers. However: the performance of OFDMsysfertts can still be compromised due to adjacent channel and cochannel interjerence. In this paper.we investigate the performance of an adaptive beanforming algorithm for an OFDM system based on the constant modulus (CM) array. We consider this blind technique for a wireless local area nehvork such as the IEEE 802.IIa standard. The algorithm exploits the constant ntodulusproperfy of the low-rare OFDM data carriers, and we show that it can also be used for the nonconstanf modulus constellations at higher data rates. We consider the case where cochannel users become active part way into the transmitted packet such that new beanformer weights should be computed to null these interfering signals.

Mutual Interference of Automotive OFDM Radars—Analysis and Countermeasures

“…The recursive algorithm [34], [35] can be included into the signal processing chain of the Rx OFDM symbols. In the spectrogram and after the spectral division, the N received modulation symbols of the m-th OFDM symbol d RX (m)∈ C N of all P Rx channels form the input matrix X(m) ∈ C P×N of iteration m. Based on the weight vector of the previous iteration, the output signal…”

An energy‐efficient anti‐jam cognitive system for wireless OFDM communication

“…The vulnerability of pilot‐based Weiner filtering channel estimation under narrowband and partial band jamming for OFDM/MC‐CDMA system has been analyzed in . The performance of beamforming algorithms for adjacent channel and co‐channel interference cancelation in OFDM systems has been studied in . In , beamforming techniques for canceling the jamming effects in OFDM systems have also been investigated.…”

Compensation of the clustering in post-FFT OFDM beamforming using pilot relocation

“…Conventional single antenna OFDM receivers are not able to cancel such interferences efficiently. An array of antennas have been employed to suppress CCI by spatial domain processing techniques [1][2][3][4][5][6][7][8]. Antenna arrays, at the same time, can mitigate the effect of ISI and relax the design of channel equalizers.…”

“…Algorithms of this type recruit pilot symbols transmitted by the desired user to produce a weight vector that attempts to minimize the mean square error between the array output and the known pilots at the receiver. Such algorithms can be applied in either time domain [1][2][3][4] or frequency domain [5][6][7][8][9]. In general, time-domain array processing which is referred to as pre-FFT scheme has low complexity because only one FFT operation is required.…”