Comparison of OFDM Acquisition Methods and Their Architectural Design
Author
Zorica, Marko
Term
10. term
Education
Publication year
2011
Abstract
Denne afhandling undersøger akquisition i OFDM-modtagere med fokus på synkronisering (ramme-/symbolstartdetektion) og grov vurdering af bærefrekvensforskydning. Motiveret af OFDM’s robusthed mod flervejsforplantning og følsomhed over for synkroniseringsfejl sammenlignes to udbredte tilgange: guard-interval-baseret (GIB), som anvendes i DVB-T, og præambelbaseret, som bruges i WLAN og nyere 4G-systemer. Teksten introducerer OFDM-grundlag, sender- og modtagerarkitektur samt den cykliske præfiks’ rolle i at reducere intersymbolinterferens. Der udvikles en MATLAB-simulationsmodel baseret på IEEE 802.11a (forenklet uden FEC) til at studere timing- og frekvensakquisition ved hjælp af korte og lange præambler; indledende simuleringer analyserer, hvordan bærefrekvensforskydning påvirker timingmetrik under idealiserede kanalforhold. Senere kapitler (ikke med i dette uddrag) præsenterer bredere simuleringer af frekvens- og tidsmetoder samt en implementeringsarkitektur med algoritmespecifikationer og planlægning. Da detaljerede resultater og sammenlignende konklusioner ikke fremgår af dette uddrag, henvises der til resten af afhandlingen for dem.
This thesis examines acquisition in OFDM receivers, focusing on synchronization (frame/symbol start detection) and coarse carrier frequency offset estimation. Motivated by OFDM’s robustness to multipath and its sensitivity to synchronization errors, it compares two widely used approaches: guard-interval–based (GIB), as in DVB-T, and preamble-based methods, as in WLAN and emerging 4G systems. The document introduces OFDM fundamentals, transmitter and receiver architectures, and the role of the cyclic prefix in mitigating intersymbol interference. A MATLAB simulation model aligned with IEEE 802.11a (simplified without FEC) is developed to study timing and frequency-offset acquisition using short and long preambles; initial simulations explore how carrier frequency offset affects timing metrics under idealized channel conditions. Subsequent chapters (not included here) present broader simulations of frequency-offset and timing methods and an architectural design for implementation, including algorithm specifications and scheduling. Detailed results and comparative conclusions are reported later in the thesis and are not available in this excerpt.
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