Sidelobe Suppression for OFDM-Based Cognitive Radios Using Constellation Expansion

Pagadarai, Srikanth; Rajbanshi, Rakesh; Wyglinski, Alexander M.; Minden, Gary J.

doi:10.1109/wcnc.2008.162

Cited by 90 publications

(46 citation statements)

References 7 publications

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“…4. To reduce the sidelobe power in primary band, different variants of constellation expansion [12] are used. Simulations are performed for four different scenarios with primary band (PU) spanning over either 16 or 32 subcarriers.…”

Section: A Simulation Results and Discussionmentioning

confidence: 99%

“…The focus of our work in this study, is the OOBR suppression unit. We have divided our study into two parts: In the first part, we compare different variants of the original Constellation expansion technique [12] to reduce the OOBR. In the basic CE technique, the baseband symbols are mapped to a higher constellation in a random fashion and the constellation symbol sequence that produces minimum OOBR, is selected for transmission.…”

Section: System Modelmentioning

confidence: 99%

“…In the Constellation Expansion (CE) technique [12], each symbol is randomly mapped to a corresponding symbol from higher constellation space before modulation. If an n bit/symbol modulation scheme having 2 n constellation points, is mapped to an (n+1) bit/symbol modulation scheme with 2 (n+1) constellation points, then for each constellation point we have to make a choice from two higher order constellation points.…”

Section: Constellation Expansion With Single Symbol Mappingmentioning

confidence: 99%

“…In this paper, we study different variants of constellation expansion (CE) technique [12], to reduce the out of band interference power from the secondary users to the primary users. We study CE technique by varying the type of mapping, number of iterations and the width of PU band.…”

Section: Introductionmentioning

confidence: 99%

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Reduction of Out of Band Radiation Using Modified Constellation Expansion in OFDM based Cognitive Radio

Malik¹

2016

IJCNT

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Abstract:Out of band radiation (OOBR) is one of the major problems in OFDM based Cognitive Radios. In the spectrum sharing scenario, OOBR generates appreciable interference to the primary user, even if its spectrum band is not used. The basic cause of this OOBR is the rectangular shaped OFDM symbol. To mitigate the effects of the OOBR, a number of techniques have been proposed in the literature. These techniques shape the OFDM symbol either in time or in frequency domain. Time domain techniques achieve OOBR reduction by using smoother windows. But this reduces the overall throughput of the system. In frequency domain techniques, some of the subcarriers are either used as guard band or reserved for interference cancellation. These subcarriers do not carry any data and as such reduce the spectral efficiency of the system. In this paper, we use different variants of Constellation expansion (CE) technique to reduce OOBR. CE techniques do not suffer from throughput reduction or spectral efficiency loss, as the original symbols are mapped to a higher order constellation set and the symbol sequence is replaced by a new sequence that produces minimum OOBR. We study different mapping techniques based on single bit or two bit mapping of CE technique. We show through simulations that two bit mapping of CE technique gives appreciable improvement over the basic CE technique.

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Section: A Simulation Results and Discussionmentioning

confidence: 99%

Section: System Modelmentioning

confidence: 99%

Section: Constellation Expansion With Single Symbol Mappingmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Reduction of Out of Band Radiation Using Modified Constellation Expansion in OFDM based Cognitive Radio

Malik¹

2016

IJCNT

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“…Active and null cancellation carriers (ANCC) [19] technique combine active and null cancellation carriers in the guard band. Subcarrier weighting (SW) [20] technique suppresses the sidelobes by weighting all the subcarriers with an optimal set of real-valued coefficients, advance subcarrier weightings (ASW) [21], in which Selim, A. and Doyle, L. propose a heuristic approach for sidelobe suppression for OFDM systems using subcarrier weighting, multiple choice sequence (MCS) [22], where the sequence of symbols carried by subcarriers is mapped to an optimal sequence that yields lower sidelobe interference, Constellation expansion (CE) [23][24][25] transmits symbols from a higher order constellation set and chooses the sequence that results in the lowest possible sidelobe power level, Insertion of guard bands [26,27] where the interference is alleviated by adaptively deactivating the nearby subcarriers, providing flexible guard bands between licensed and un-licensed users and spectral precoding schemes [28][29][30][31][32] to reduce the interference by designing special precoder matrices, etc.…”

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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References

2017

Advanced Multicarrier Technologies for Future Radio Communication

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Sidelobe Suppression for OFDM-Based Cognitive Radios Using Constellation Expansion

Cited by 90 publications

References 7 publications

Reduction of Out of Band Radiation Using Modified Constellation Expansion in OFDM based Cognitive Radio

Reduction of Out of Band Radiation Using Modified Constellation Expansion in OFDM based Cognitive Radio

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

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