Edge Windowing for OFDM Based Systems

Şahin, Alphan; Arslan, Hüseyin

doi:10.1109/lcomm.2011.090611.111530

Cited by 86 publications

(52 citation statements)

References 6 publications

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“…The windowing method including several kinds of window functions is proposed in [9][10][11]. Since the window function is directly multiplied to the signal after IFFT, ε l = 0, H is a diagonal matrix and the values of its diagonal entries depend on the selection of the window function.…”

Section: Techniques Represented By the Time-domain Approachesmentioning

confidence: 99%

“…They can be classified into two categories: the time-domain schemes and the frequency-domain schemes. The time-domain schemes include filtering [8], windowing [9][10][11], etc., where the OOBE reduction processes are carried out after the inverse fast Fourier transform (IFFT). The frequency-domain schemes include carrier cancellation (CC) [12], constellation extension (CE) [13], precoding [14][15][16][17][18], etc., where the OOBE reduction processes are carried out before the IFFT.…”

Section: Introductionmentioning

confidence: 99%

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Out-of-band emission suppression techniques based on a generalized OFDM framework

You

Fang

2014

EURASIP J. Adv. Signal Process.

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Orthogonal frequency division multiplexing (OFDM)-based cognitive radio (CR) systems suffer from the large out-of-band emission (OOBE) that may interfere with other users. Since most existing OFDM OOBE suppression schemes are derived on the base of an original OFDM system without any other scheme, we first propose a generalized OFDM framework that is capable of describing these schemes no matter whether any one or more of the schemes is applied. Then, according to the place where these schemes are implemented in our framework, they are classified into three groups, namely symbol mapping techniques, precoding techniques, and time-domain techniques. Finally, based on the proposed framework, we propose three new schemes by combining a precoding scheme named singular value decomposition (SVD) precoding with three other schemes from the three groups, namely spectral precoding, N-continuous symbol mapping, and filtering. Numerical results show the power spectral density (PSD), peak-to-average power ratio (PAPR), and bit error rate (BER) performances of the three proposed schemes. Since the individual schemes have complementary characteristics, the three proposed combined schemes are constructed to maintain the merits and avoid the drawbacks of the individual schemes involved. Thus, it is demonstrated that the proposed framework can be employed to develop other new combined OOBE suppression schemes tailoring to some specific practical needs.

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Section: Techniques Represented By the Time-domain Approachesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Out-of-band emission suppression techniques based on a generalized OFDM framework

You

Fang

2014

EURASIP J. Adv. Signal Process.

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“…To tackle the OOB radiation problem, various techniques are proposed in the literature that can be categorized into two groups: time domain techniques and frequency domain techniques. Time domain techniques include filtering [7], which suffers from high complexity and lack of guard interval, and windowing [8,9], which expands the signal in time domain and results in intersymbol interference (ISI). Frequency domain techniques include adaptive symbol transition (AST) [10], which expands the signal by injecting additional samples within a specified power threshold between two transmission blocks to reduce the interference of these two blocks at definite frequencies, active interference cancellation (AIC) [11][12][13], where a few subcarriers lying at the border of the licensed user band are reserved for reducing the interference.…”

Section: Introductionmentioning

confidence: 99%

Sidelobe Reduction in Non-Contiguous OFDM-Based Cognitive Radio Systems Using a Generalized Sidelobe Canceller

et al. 2015

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Abstract:In orthogonal frequency division multiplexing (OFDM), sidelobes of the modulated subcarriers cause high out-of-band (OOB) radiation, resulting in interference to licensed and un-licensed users in a cognitive radio system environment. In this work, we present a novel technique based on a generalized sidelobe canceller (GSC) for the reduction of sidelobes. The upper branch of the GSC consists of a weight vector designed by multiple constraints to preserve the desired portion of the input signal. The lower branch has a blocking matrix that blocks the desired portion and preserves the undesired portion (the sidelobes) of the input signal, followed by an adaptive weight vector. The adaptive weight vector adjusts the amplitudes of the undesired portion (the sidelobes) so that when the signal from the lower branch is subtracted from the signal from the upper branch, it results in cancellation of the sidelobes of the input signal. The effectiveness and strength of the proposed technique are verified through extensive simulations. The proposed technique produces competitive results in terms of sidelobe reduction as compared to existing techniques. OPEN ACCESSAppl. Sci. 2015, 5 895

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“…These approaches can be classified into two categories: the time-domain and frequencydomain approaches. The time-domain approaches include windowing [7] and filtering [8] where the OOBE suppression processes are carried out in the time domain (after the inverse fast Fourier transform (IFFT) operation). The frequency-domain approaches include subcarrier weighting [9], carrier cancellation [10,11], and spectral precoding [12,13], where the OOBE suppression processes are carried out in the frequency domain (before the IFFT operation).…”

Section: Introductionmentioning

confidence: 99%

Practical designs for out-of-band emission suppression and adjacent channel interference rejection for orthogonal frequency division multiplexing-based cognitive radios

Fang

2015

J Wireless Com Network

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Opposite to the conventional wisdom, practical considerations for out-of-band emission (OOBE) suppression and adjacent channel interference (ACI) rejection in orthogonal frequency division multiplexing (OFDM) -based cognitive radio systems are not completely alike. For example, ACI will increase after discarding the cyclic prefix (CP) because the interference signal is also truncated during the CP removal process. Furthermore, effective OOBE is much larger than the estimated OOBE if there is a timing offset (TO) between the primary and secondary users. To the best of our knowledge, these and some other practical issues have not been well addressed. Various important practical issues (including multipath delay spread, high peak-to-average power ratio (PAPR), spectral efficiency loss, high complexity, sensitivities to frequency and timing offsets, non-contiguous and dynamically changing spectrum, CP removal, spectral containment, etc.) concerning OOBE suppression and ACI rejection are studied in this paper. Numerical results show that none of the existing approaches can deal with all practical issues satisfactorily. Hybrid combinations of frequency-domain approaches (spectral precoding and PAPR precoding) and time-domain approaches (windowing and filtering) are developed to maintain the merits and mitigate the drawbacks of each constituent approach in order to deal with these practical challenges. It is shown that a combination of filtering and precoding provides the best OOBE suppression and a combination of windowing and precoding provides the best ACI rejection characteristics in our numerical examples.

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Edge Windowing for OFDM Based Systems

Cited by 86 publications

References 6 publications

Out-of-band emission suppression techniques based on a generalized OFDM framework

Out-of-band emission suppression techniques based on a generalized OFDM framework

Sidelobe Reduction in Non-Contiguous OFDM-Based Cognitive Radio Systems Using a Generalized Sidelobe Canceller

Practical designs for out-of-band emission suppression and adjacent channel interference rejection for orthogonal frequency division multiplexing-based cognitive radios

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