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An analysis of out-of-band emission and in-band interference for precoded and classical OFDM systems
Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.ORCID iD: 0000-0002-9225-8150
Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.ORCID iD: 0000-0003-0413-4826
Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.ORCID iD: 0000-0001-8647-436X
2015 (English)In: European Wireless 2015: 21th European Wireless Conference, 20-22 May 2015, Budapest, Hungary, Piscataway, NJ: IEEE Communications Society, 2015, article id 7147703Conference paper, Published paper (Refereed)
Abstract [en]

In this paper we present analytical expressions for the out-of-band (OOB) emission and in-band interference of two different OOB suppressed OFDM-systems; classical low-pass filtered and precoded. Then, we analytically compare their performance in terms of OOB emission suppression and introduced level of in-band interference. We analyse the fact that the in-band interference introduced by the filter depends on the length of the cyclic prefix as well as the behavior of the channel while that of the precoded OFDM does not. The analysis confirms that edged subcarriers suffer higher in-band interference than central subcarriers. Moreover, frequency precoders, for a specific choice of notching frequencies, can outperform time precoders.

Place, publisher, year, edition, pages
Piscataway, NJ: IEEE Communications Society, 2015. article id 7147703
National Category
Signal Processing
Research subject
Signal Processing
Identifiers
URN: urn:nbn:se:ltu:diva-34467Local ID: 8ad284fe-4be4-4f35-b93d-3e81a90f5fb2ISBN: 978-3-8007-3976-9 (electronic)OAI: oai:DiVA.org:ltu-34467DiVA, id: diva2:1007718
Conference
European Wireless : 20/05/2015 - 22/05/2015
Note
Godkänd; 2015; 20150703 (jaavan)Available from: 2016-09-30 Created: 2016-09-30 Last updated: 2018-12-07Bibliographically approved
In thesis
1. Spectrally Precoded OFDM-Design and Analysis
Open this publication in new window or tab >>Spectrally Precoded OFDM-Design and Analysis
2019 (English)Doctoral thesis, comprehensive summary (Other academic)
Alternative title[sv]
Spektral förkodning i OFDM-design och analys
Abstract [en]

Despite shifting towards mm-wave bands, the sub-6 GHz band will continue to be a fundamental spectral band in 5G. However, the severe congestion in this band makes a well-constrained spectrum a critical requirementof 5G. A well-constrained spectrum means that the communications regimes should dwell within their dedicated spectral bands and do not interfere with other systems working on neighboring bands. Consequently, the communi-cations community seeks convenient modulation schemes.

The 5G standards have already defined cyclic prefix orthogonal frequency division multiplexing (CP-OFDM) as the modulation scheme for most of the sub-6 GHz band. However, the high out-of-band (OOB) emission phe-nomenon in OFDM is unfavorable for some regimes operating in 5G. Therefore, to legitimize OFDM in all 5G regimes, we need to suppress the OFDM OOB emission.

Since the discontinuous nature of the OFDM signal is the main reason forthe high OOB emission, one solution is to render the discontinuous OFDM signal continuous. Two factors control this discontinuity: the physical shape of the modulated signal and the correlation of the data symbols that modulate the OFDM signal.

While most traditional approaches focus on reshaping the OFDM signal to render it continuous, in this work, we give our attention to the spectral precoding approaches. These approaches manipulate the correlation of the data symbols to control the high OOB emission in OFDM.

After almost ten years of analytical and theoretical study of the spectralprecoding approaches in the literature, we believe it is time to investigate the practicality and ability of spectral precoding methods to compete with traditional approaches. Consequently, we check whether spectral precoding satisfies the spectral requirements of LTE measures. We analyze the precoders' implementation complexity and provide methodologies to reduce it. We design practical spectral precoders that match with the practical OFDM transmitters, and we study spectral precoding extensibility toward MIMO (and massive MIMO) systems.

Moreover, in this work, we introduce the first proof-of-concept prototype of spectrally precoded OFDM. In the prototype, we use software-defined radios (SDRs) to perform a real-time examination of how spectral precoding improves the spectral containment of OFDM systems.

Place, publisher, year, edition, pages
Luleå: Luleå University of Technology, 2019
Series
Doctoral thesis / Luleå University of Technology 1 jan 1997 → …, ISSN 1402-1544
Keywords
OFDM, spectral precoding, out of band emission, 5G
National Category
Signal Processing
Research subject
Signal Processing
Identifiers
urn:nbn:se:ltu:diva-71971 (URN)978-91-7790-282-9 (ISBN)978-91-7790-283-6 (ISBN)
Public defence
2019-02-19, E632, Luleå tekniska universitet, Luleå, 13:00 (English)
Opponent
Supervisors
Funder
Swedish Research Council
Available from: 2018-12-07 Created: 2018-12-07 Last updated: 2019-01-31Bibliographically approved

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Mohamad, MedhatNilsson, RickardBeek, Jaap van de

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