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Signal Enhancement in Wireless Communications Systems
Responsible organisation
2002 (English)Doctoral thesis, comprehensive summary (Other academic)Alternative title
Signalförbättring i trådlösa telekommunikationssytem (Swedish)
Abstract [en]

Digital Wireless communications has been one of the fastest growing communication techniques during the last decade. Today there exists several different communication systems that use wireless techniques. They share one common property that they transmit data through a radio interface. The radio channel is a tough channel that will both distort and disturb the transmitted signal in various ways. In Jörgen Nordberg's PhD-thesis "Signal Enhancement in Wireless Communications Systems" several different signal enhancement schemes are presented. They have the objective to minimize the impact of the channel. The main part of this thesis presents work on interference cancellation, i.e. how to reduce the impact of other interfering signals on the channel of interest. This is achieved by utilizing the spatial domain, i.e. the receiver is using several antennas to receive the transmitted signals. By using a multitude of antennas techniques like spatial diversity, adaptive antenna arrays, signal separation and beamforming can be applied to combat the interfering signals. In the single antenna case there is often a need to do channel equalization. Since, channel equalization is an inverse filtering, it will often result in estimation of equalization filter parameters of very high order. To reduce the both the complexity and improve the convergence speed of the equalization filter parameter estimation subband processing techniques can be used. In this case the received signal is separated up into different frequency bands (subbands) and decimated according to the bandwidth of the signal. The channel equalization problem is then solved for each subband at a lower sampling rate. Hence, the channel equalization problem is transformed from estimating the parameters of a high order filter into estimating several filter of much lower order.

Abstract [sv]

Ett av områdena inom telekommunikation som har ökat mest de senaste åren är radio kommunikation. Det finns många olika varianter av trådlösa radio system, men de har alla en sak gemensamt, de överför information/data via ett radiogränssnitt. Signaler som sänds över en radiokanal kommer på grund av många olika anledningar att bli störda eller distorderade. I Jörgen Nordbergs doktorsavhandling ?Signal Enhancement in Wireless Communication Systems? presenteras flera metoder för att förbättra kvaliten i de mottagna signalerna vilket ger betydande kvalitetsförbättring. Huvuddelen av denna doktorsavhandling behandlar interferensundertrycking, d.v.s. hur man undertrycker oönskad störning på den egna radiokanalen. Dessa metoder är baserade på användning av flera antenner i mottagaren. Genom att ta emot signalerna med flera antenner så kan metoder såsom diversitetskombinering, adaptiva antenner, lobformning, signal separation användas för att förbättra kvaliteten i den mottagna signalen. Om mottagaren har en antenn så behövs oftast kanalutjämning för att förbättra den mottagna signalen och undertrycka intersymbolinterferens. Eftersom kanalutjämning är en typ av inversfiltrering leder detta ofta till estimering av filterparametrar av hög ordning. Estimeringsproblem av hög ordning leder ofta till komplexitetsproblem och konvergensproblem hos estimerings algoritmen. För att motverka dessa problem så presenteras i denna avhandling en kanalutjämnare som är baserad på subbandsteknik. I denna kanalutjämnare så delas den mottagna signalen upp i flera frekvensband (subband) som decimeras till en takt som motsvarar subbandets bandbredd varefter filterparametrarna estimeras i denna lägre takt. Därvid har estimeringsproblemet delats upp i flera små problem som kan hanteras enklare.

Place, publisher, year, edition, pages
Ronneby: Blekinge Institute of Technology , 2002. , 146 p.
Series
Blekinge Institute of Technology Dissertation Series, ISSN 1650-2159 ; 7
Keyword [en]
Channel equlization, Multirate Equalization, Signal Separation, Beamforming, Sptial Equalization
National Category
Telecommunications Signal Processing
Identifiers
URN: urn:nbn:se:bth-00229ISBN: 91-7295-018-8 (print)OAI: oai:DiVA.org:bth-00229DiVA: diva2:837455
Available from: 2012-09-18 Created: 2003-01-07 Last updated: 2016-02-15Bibliographically approved

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TelecommunicationsSignal Processing

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