Selective self ICI cancellation scheme for OFDM systems

International Journal of Computer and Communication Engineering, 2014

Orthogonal Frequency Division Multiplexing (OFDM) is sensitive to Carrier Frequency Offset (CFO), which in turn causes Intercarrier Interference (ICI) and degrades system performance. During the last decade, several ICI self cancellation schemes were proposed in the literature. This paper introduces a new ICI self-cancellation scheme with an improved immunity against CFO errors as evidenced by Carrier to Interference Ratio (CIR) and Bit Error Rate (BER) analyses. Index Terms-Carrier frequency offset (CFO), self cancellation (SC), intercarrier interference (ICI), CIR (carrier to interference ratio), OFDM (orthogonal frequency-division multiplexing).

2015 IEEE International Conference on Computational Intelligence & Communication Technology, 2015

Intercarrier interference (ICI) is one of the critical problems faced in orthogonal frequency division multiplexing (OFDM) systems which is caused mainly due to frequency impairment of local oscillators, Doppler spread of time varying channels which results in carrier frequency offset (CFO). ICI destroys the orthogonality of OFDM signals and degrades the system performance. Many ICI reduction techniques like frequency domain equalization, time domain windowing, pulse shaping and ICI self cancellation have been developed. ICI self cancellation is an efficient technique in terms of bit error rate, computational complexity. Interference in adjacent subcarriers is self cancelled by modulating the same data on adjacent subcarriers with predefined weighting coefficients. This paper gives a brief overview of various ICI self cancellation techniques based on this principle.

International journal of physical sciences

A well-known problem of orthogonal frequency division multiplexing (OFDM) is its sensitivity to offset between the transmitted and received carrier frequencies. In OFDM communication systems, the frequency offsets in mobile radio channels deform the orthogonality between subcarriers which causes inter carrier interference (ICI). ICI causes power leakage among subcarriers and it further degrades the system performance. In this paper a novel bandwidth efficient method for combating the effects of ICI is presented. In the present scheme, the self cancellation mechanism is used to compress ICI signals without any equalization. At transmitter and receiver parallel Fast Fourier Transform (FFT) factorization is performed using Radix-2 decimation in frequency (DIF) FFT algorithm derived from the well known Cooley-turkey factorization. The proposed scheme cancels the ICI coefficient effectively and further improves system performance as shown through extensive simulations.

2005 Asia-Pacific Conference on Applied Electromagnetics

OFDM is a successful technique in wireless communication system. Frequency offset in OFDM systems leads to loss of orthogonality among subcarriers, which resulted in intercarrier interference (ICI) to occur. Another main problem of OFDM is the occurrence of high PAPR. To mitigate ICI problem, ICI self-cancellation scheme and frequency domain partial response coding has been proposed. In this paper, we evaluate the performance of ICI selfcancellation schemes and the integer-coefficients partial response coding (PRC). ICI self-cancellation data allocation of (Xk,+=-X*k) has the best PAPR performance while the data allocation of (XakXk+=-Xk) has the most CIR enhancement The integer coefficients PRC outperform the ICI self-cancellation schemes in terns of bandwidth efficiency and in the BER performance especially at high E/N0.

In the area of wireless communications, the demand for high data rate transmission is rapidly increasing. Orthogonal frequency division multiplexing (OFDM) is known to be a promising technique for high-rate transmission that can overcome the inter symbol interference (ISI) which results from the time dispersive nature of wireless channels. For OFDM communication systems the orthogonality is lost among the sub-carriers due to frequency offset which results in Inter carrier Interference (ICI). This ICI rapidly degrades the performance of OFDM system. We have so many ICI cancellation methods like time windowing and frequency equalization to improve the BER performance of OFDM systems. In this an efficient ICI cancellation methods termed ICI self-cancellation (SC) scheme, extended Kalman filter (EKF) method and another ICI cancellation scheme, named Total ICI Cancellation scheme are proposed. However the total ICI cancellation scheme has does not lower the transmission rate or reduce the bandwidth efficiency. It is shown that for high values of the frequency offset and for higher order modulation schemes, the EKF method perform better than the SC method. Keywords—Orthogonal frequency divison multiplexing (OFDM) Inter carrier interference(ICI), self cancellation (SC),Extended Kalman filtering (EKF) .

2005

For OFDM systems, the carrier frequency offsets will ruin the orithogonality among subcarriers and hence result in intercarrier interference (ICI). We propose a multi-step ICI self-cancellation algorithm, which can be implemented recursively to suppress ICI. In comparison with other ICI self-cancellation procedures, the proposed scheme is characterized by low complexity and not amplifying the data symbols. We compute the carrier-to-interference ratio (CIR) at each step to evaluate the gains on ICI reduction. The effectiveness of the proposed scheme is further verified by computing the bit error rates of various OFDM receivers, and significant performance improvements were found.

IEEE Transactions on Communications, 2001

For orthogonal frequency-division multiplexing (OFDM) communication systems, the frequency offsets in mobile radio channels distort the orthogonality between subcarriers resulting in intercarrier interference (ICI). This paper studies an efficient ICI cancellation method termed ICI self-cancellation scheme. The scheme works in two very simple steps. At the transmitter side, one data symbol is modulated onto a group of adjacent subcarriers with a group of weighting coefficients. The weighting coefficients are designed so that the ICI caused by the channel frequency errors can be minimized. At the receiver side, by linearly combining the received signals on these subcarriers with proposed coefficients, the residual ICI contained in the received signals can then be further reduced. The carrier-to-interference power ratio (CIR) can be increased by 15 and 30 dB when the group size is two or three, respectively, for a channel with a constant frequency offset. Although the redundant modulation causes a reduction in bandwidth efficiency, it can be compensated, for example, by using larger signal alphabet sizes. Simulations show that OFDM systems using the proposed ICI self-cancellation scheme perform much better than standard systems while having the same bandwidth efficiency in multipath mobile radio channels with large Doppler frequencies.

In the area of wireless communications, the demand for high data rate transmission is rapidly increasing. Orthogonal frequency division multiplexing (OFDM) is known to be a promising technique for high-rate transmission that can overcome the inter symbol interference (ISI) which results from the time dispersive nature of wireless channels. For OFDM communication systems the orthogonality is lost among the sub-carriers due to frequency offset which results in Inter carrier Interference (ICI). This ICI rapidly degrades the performance of OFDM system. We have so many ICI cancellation methods like time windowing and frequency equalization to improve the BER performance of OFDM systems. The Proposed ICI Cancellation scheme takes advantage of the orthogonality of the ICI matrix and offers perfect ICI cancellation and significant BER improvement at linearly growing cost. Simulation results in noise less channel confirm the superb performance of the proposed ICI Cancellation scheme in the presence of frequency offse t or time variations in the channel compared with other two schemes. Through a detailed analysis and simulation, it is shown that the performance of the proposed scheme gives better BER (Bit Error Rate) and CIR (Carrier to Interference Ratio) than the conventional self cancellation scheme.

IJPTT

— the consistently rising demand for very high rate data transmission over wireless mediums requires ingenious usage of electromagnetic resources considering constraints like power consumption, spectrum efficiency, robustness against multipath propagation and implementation complexity. Orthogonal frequency division multiplexing (OFDM) is a propitious technique for next generation wireless communication systems. Nevertheless it suffers from Inter-Carrier Interference (ICI) due to its susceptibility to the frequency offset caused by frequency difference between local oscillator of transmitter and receiver or due to Doppler shift. This paper epitomize self-cancellation techniques to mitigate ICI effect for OFDM based wireless systems. The performances of ICI self-cancellation schemes have been in terms of the bit error rate (BER). Simulation results exhibit ICI self-cancellation Scheme that outperforms other existing self-cancellation methods and robustness to large frequency offset.

Orthogonal frequency division multiplexing (OFDM) is a best technique for next generation wireless communication systems. However its susceptibility to the frequency offset caused by frequency difference between local oscillator of transmitter and receiver or due to Doppler shift leads to Inter Carrier Interference. This problem of ICI leads to degradation in performance of the wireless systems as bit error rate increases with increase in value of frequency offset. This paper epitomize self-cancellation techniques to mitigate ICI effect for OFDM based wireless systems.