search query: @supervisor Tirkkonen, Olav / total: 43
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Author: | Hassen, Tewodros Wolde |
Title: | Synchronization in Cognitive Overlay Systems |
Publication type: | Master's thesis |
Publication year: | 2012 |
Pages: | viii + 64 s. + liitt. 20 Language: eng |
Department/School: | Tietoliikenne- ja tietoverkkotekniikan laitos |
Main subject: | Tietoliikennetekniikka (S-72) |
Supervisor: | Tirkkonen, Olav |
Instructor: | Poikonen, Jussi |
Electronic version URL: | http://urn.fi/URN:NBN:fi:aalto-201211243398 |
OEVS: | Electronic archive copy is available via Aalto Thesis Database.
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Location: | P1 Ark Aalto 770 | Archive |
Keywords: | synchronization cognitive radio spectrum sharing interweave overlay Gnu radio DVB-T LTE |
Abstract (eng): | The primary purpose of this thesis is to study the effect of synchronization problems in cognitive radio based overlay systems. In such systems the secondary transmitter should know the transmission timing of the primary transmitter for cooperation to take place between the two systems. The thesis also investigates the effect of relaying in overlay systems. By splitting the secondary transmission power into two parts by a ratio alpha, the secondary transmitter can relay the primary transmission while transmitting its own message. Another aim of the thesis is to study the effects of time and frequency offsets in the primary and the secondary systems. Hence, time and frequency synchronization issues are investigated for DVB-T and LTE systems individually. Cell search and selection procedures are also studied for LTE systems. Two N200 Universal Software Radio Peripherals (USRPs) were used to transmit and receive the signal using the Gnu Radio platform and the captured signals were post processed in Matlab to study the effects of time offset and frequency offset of the devices. Moreover, a Matlab simulation was used to investigate the effect of timing offset between primary and secondary transmitters in overlay systems. From the investigation of the overlay scenario with relay, we have found out that the relaying introduce a multi-path effect at the secondary receiver. If there is a delay between the primary and the secondary receivers, the components of the multi-path signal might be added-up in such a way that it is impossible to separate the primary and the secondary signals at the secondary receiver. Hence, we have implemented synchronization and equalization algorithms to estimate the delay and frequency offsets. We observed that the performance of the equalizer at the secondary receiver deteriorates for high delays and low alpha values. |
ED: | 2012-11-20 |
INSSI record number: 45419
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