Contributions to time-frequency synchronization in wireless systems

Tommi Koivisto

Contributions to time-frequency synchronization in wireless systems

Julkaisun otsikon käännös: Kontribuutioita aika- ja taajuussynkronointiin langattomissa järjestelmissä

Tommi Koivisto

Tutkimustuotos: Doctoral Thesis › Collection of Articles

Abstrakti

Aika- ja taajuussynkronointi on oleellinen toiminto kaikissa langattomissa vastaanottimissa ja järjestelmissä. Nykyaikaisissa langattomissa järjestelmissä, kuten 4G- sekä tulevissa 5G-järjestelmissä, uudet langattomat teknologiat asettavat uusia haasteita myös synkronoinnille. Uusia synkronointiratkaisuja tarvitaan erityisesti moniantennijärjestelmissä sekä yhteis-toiminnallisissa järjestelmissä. Joissain sovelluksissa, esimerkiksi häiriönpoistossa ja kognitiivisissa radioissa, synkronointi on tehtävä vastaanottimessa tuntematta kaikkia signaalin lähetysparametreja, jolloin synkronointi on erityisen haastavaa. Myös sotilas-sovelluksissa, esimerkiksi tiedusteluvastaanottimien synkronoinnissa, on vastaavia tilanteita. Tässä väitöskirjassa tutkitaan ja analysoidaan uusia menetelmiä aika- ja taajuussynkronointiin langattomissa järjestelmissä. Tutkimuksen kohteena ovat sekä monikantoaaltomodu-laatioon perustuvat OFDM-järjestelmät että suorahajotukseen perustuvat hajaspektri-järjestelmät. Työ koostuu seitsemästä erillisestä julkaisusta sekä yhteenvedosta, johon on koottu myös laaja kirjallisuuskatsaus aiheesta. Suorahajotushajaspektrijärjestelmiin liittyen väitöskirjassa on tutkittu menetelmiä, joilla synkronointi voidaan tehdä tuntematta hajotuskoodia. Työssä on kehitetty aliavaruus-menetelmiin pohjautuva algoritmi synkronointiin ja hajotuskoodin estimointiin asynk-ronisissa monen käyttäjän hajaspektrijärjestelmissä. Menetelmällä voidaan saavuttaa lähes sovitettua suodatinta vastaava optimaalinen prosessointivahvistus. Tutkittuja menetelmiä voidaan käyttää häiriönpoistossa, kognitiivisissa radioissa sekä sotilassovelluksissa. Väitöskirjassa on tutkittu myös synkronointimenetelmiä moniantennijärjestelmissä. Työssä on johdettu analyyttisiä tuloksia synkronoinnin onnistumisen todennäköisyydelle tilanteissa, joissa useampaa antennia käytetään sekä lähetys- että vastaanottopäässä lähetys-, vastaanotto- ja aikadiversiteetin parantamiseen. Analyyttisten tulosten on myös näytetty vastaavan simuloituja tuloksia. Työssä on myös tutkittu optimaalisia lähetystapoja. Menetelmiä on simuloitu laajasti eri signaalikohinatasoilla, erilaisilla radiokanavan korrelaatioilla sekä Doppler-hajeilla. Tuloksilla on käyttöä esimerkiksi moniantennijärjestelmien suunnittelussa.Työssä on tutkittu myös aika- ja taajuuspoikkeamien vaikutuksia yhteistoiminnallisissa OFDM-järjestelmissä, ja näytetty vaikutusten olevan merkittävästi haitallisempia kuin perinteisissä OFDM-järjestelmissä. Näiden ongelmien ratkaisemiseksi työssä on tutkittu menetelmiä taajuuspoikkeamien estimointiin ja kehitetty uusia menetelmiä, joiden avulla taajuuspoikkeamat voidaan estimoida laskennallisesti yksinkertaisilla algoritmeilla. Menetelmillä saavutetaan alhainen estimoinnin keskineliövirhe, joka on hyvin lähellä Cramér-Raon alarajaa.

Julkaisun otsikon käännös	Kontribuutioita aika- ja taajuussynkronointiin langattomissa järjestelmissä
Alkuperäiskieli	Englanti
Pätevyys	Tohtorintutkinto
Myöntävä instituutio	Aalto-yliopisto
Valvoja/neuvonantaja	Koivunen, Visa, Vastuuprofessori Koivunen, Visa, Ohjaaja
Kustantaja	Aalto University
Painoksen ISBN	978-952-60-6332-4
Sähköinen ISBN	978-952-60-6333-1
Tila	Julkaistu - 2015
OKM-julkaisutyyppi	G5 Artikkeliväitöskirja

Tutkimusalat

synkronointi
hajaspektritekniikka

Pääsy asiakirjaan

http://urn.fi/URN:ISBN:978-952-60-6333-1Lisenssi: Määrittelemätön

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@phdthesis{6b66101c428c48009cd9ee5ff2f45c16,

title = "Contributions to time-frequency synchronization in wireless systems",

abstract = "Time and frequency synchronization is an indispensable task for all wireless transceivers and systems. In modern wireless systems, such as 4G and future 5G systems, new wireless technologies set new challenges also to synchronization. In particular, new solutions for time and frequency synchronization are needed in multiantenna and cooperative systems. New research areas arise also in context of interference cancellation and cognitive radio systems where the transmission parameters of the signal of interest may not be known to the receiver. Similar applications can be found also in the military domain. Obviously, synchronization in such cases poses significant challenges. In this thesis, new methods for time and frequency synchronization in wireless systems are developed and analyzed. Both orthogonal frequency division multiplexing (OFDM) -based as well as direct sequence spread spectrum (DSSS) -based systems are considered. The thesis consists of seven publications and a summary which contains also an extensive literature review on the topic. Synchronization acquisition methods in DSSS-based systems without the knowledge of the spreading sequence are developed. A subspace -based method for asynchronous multi-user DSSS systems is proposed and shown to achieve nearly optimal processing gain corresponding to that of the conventional matched filter. The studied methods find applications in interference cancellation, cognitive radio as well as in military applications. Multiantenna methods for synchronization are analyzed. Probabilities of synchronization acquisition and false alarm are derived analytically for the multiantenna case where transmit, receive and time diversity schemes are used. The analytical results are verified by simulations. Also optimum synchronization sequence transmission schemes are derived. Extensive simulation results for various scenarios in terms of signal-to-noise ratio, spatial correlation and Doppler spread are provided. The results can be used to facilitate practical design of wireless multiantenna systems. The impacts of time and frequency offsets in cooperative OFDM wireless systems are analyzed and quantified and shown to be, in some cases, much more severe than in traditional OFDM systems. Solutions to estimation of multiple frequency offsets in cooperative OFDM systems are then studied. A method enabling low complexity algorithms to be used for the estimation is proposed and shown to achieve mean square error performance close to the Cram{\'e}r-Rao bound.",

keywords = "synchronization, OFDM, spread spectrum, MIMO, synkronointi, hajaspektritekniikka, synchronization, OFDM, spread spectrum, MIMO",

author = "Tommi Koivisto",

year = "2015",

language = "English",

isbn = "978-952-60-6332-4",

series = "Aalto University publication series DOCTORAL DISSERTATIONS",

publisher = "Aalto University",

number = "114",

address = "Finland",

school = "Aalto University",

}

TY - BOOK

T1 - Contributions to time-frequency synchronization in wireless systems

AU - Koivisto, Tommi

PY - 2015

Y1 - 2015

N2 - Time and frequency synchronization is an indispensable task for all wireless transceivers and systems. In modern wireless systems, such as 4G and future 5G systems, new wireless technologies set new challenges also to synchronization. In particular, new solutions for time and frequency synchronization are needed in multiantenna and cooperative systems. New research areas arise also in context of interference cancellation and cognitive radio systems where the transmission parameters of the signal of interest may not be known to the receiver. Similar applications can be found also in the military domain. Obviously, synchronization in such cases poses significant challenges. In this thesis, new methods for time and frequency synchronization in wireless systems are developed and analyzed. Both orthogonal frequency division multiplexing (OFDM) -based as well as direct sequence spread spectrum (DSSS) -based systems are considered. The thesis consists of seven publications and a summary which contains also an extensive literature review on the topic. Synchronization acquisition methods in DSSS-based systems without the knowledge of the spreading sequence are developed. A subspace -based method for asynchronous multi-user DSSS systems is proposed and shown to achieve nearly optimal processing gain corresponding to that of the conventional matched filter. The studied methods find applications in interference cancellation, cognitive radio as well as in military applications. Multiantenna methods for synchronization are analyzed. Probabilities of synchronization acquisition and false alarm are derived analytically for the multiantenna case where transmit, receive and time diversity schemes are used. The analytical results are verified by simulations. Also optimum synchronization sequence transmission schemes are derived. Extensive simulation results for various scenarios in terms of signal-to-noise ratio, spatial correlation and Doppler spread are provided. The results can be used to facilitate practical design of wireless multiantenna systems. The impacts of time and frequency offsets in cooperative OFDM wireless systems are analyzed and quantified and shown to be, in some cases, much more severe than in traditional OFDM systems. Solutions to estimation of multiple frequency offsets in cooperative OFDM systems are then studied. A method enabling low complexity algorithms to be used for the estimation is proposed and shown to achieve mean square error performance close to the Cramér-Rao bound.

AB - Time and frequency synchronization is an indispensable task for all wireless transceivers and systems. In modern wireless systems, such as 4G and future 5G systems, new wireless technologies set new challenges also to synchronization. In particular, new solutions for time and frequency synchronization are needed in multiantenna and cooperative systems. New research areas arise also in context of interference cancellation and cognitive radio systems where the transmission parameters of the signal of interest may not be known to the receiver. Similar applications can be found also in the military domain. Obviously, synchronization in such cases poses significant challenges. In this thesis, new methods for time and frequency synchronization in wireless systems are developed and analyzed. Both orthogonal frequency division multiplexing (OFDM) -based as well as direct sequence spread spectrum (DSSS) -based systems are considered. The thesis consists of seven publications and a summary which contains also an extensive literature review on the topic. Synchronization acquisition methods in DSSS-based systems without the knowledge of the spreading sequence are developed. A subspace -based method for asynchronous multi-user DSSS systems is proposed and shown to achieve nearly optimal processing gain corresponding to that of the conventional matched filter. The studied methods find applications in interference cancellation, cognitive radio as well as in military applications. Multiantenna methods for synchronization are analyzed. Probabilities of synchronization acquisition and false alarm are derived analytically for the multiantenna case where transmit, receive and time diversity schemes are used. The analytical results are verified by simulations. Also optimum synchronization sequence transmission schemes are derived. Extensive simulation results for various scenarios in terms of signal-to-noise ratio, spatial correlation and Doppler spread are provided. The results can be used to facilitate practical design of wireless multiantenna systems. The impacts of time and frequency offsets in cooperative OFDM wireless systems are analyzed and quantified and shown to be, in some cases, much more severe than in traditional OFDM systems. Solutions to estimation of multiple frequency offsets in cooperative OFDM systems are then studied. A method enabling low complexity algorithms to be used for the estimation is proposed and shown to achieve mean square error performance close to the Cramér-Rao bound.

KW - synchronization

KW - OFDM

KW - spread spectrum

KW - MIMO

KW - synkronointi

KW - hajaspektritekniikka

KW - synchronization

KW - OFDM

KW - spread spectrum

KW - MIMO

M3 - Doctoral Thesis

SN - 978-952-60-6332-4

T3 - Aalto University publication series DOCTORAL DISSERTATIONS

PB - Aalto University

ER -

Contributions to time-frequency synchronization in wireless systems

Abstrakti

Tutkimusalat

Pääsy asiakirjaan

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