Autonomous Physical Resource Block Selection in Fractional Load Scenario for 3GPP Long Term Evolution Downlink
Authors
Nin Guerrero, Jaume ; Ordás Villamandos, Iván
Term
10. term
Publication year
2007
Pages
130
Abstract
Orthogonal Frequency Division Multiple Access (OFDMA) er den adgangsmetode, som 3GPP har valgt til nedlink i LTE UTRAN. OFDMA kan skabe orthogonalitet inden for den enkelte celle, så brugernes signaler ikke forstyrrer hinanden. Den største udfordring er derfor intercelle‑interferens fra naboceller, som kan begrænse datahastigheden for brugere tæt på cellekanten. Ved lav trafik kan en fraktionel belastningsstrategi sende kun på en del af de tilgængelige fysiske ressourceblokke (PRB'er – små tid‑frekvens‑enheder), så overlap mellem celler undgås. Det er dog ikke trivielt at beslutte, hvilke PRB'er hver celle skal bruge. I denne afhandling udvikles autonome algoritmer til ressourcevalg, der udpeger PRB'er ved kun at bruge information, som er tilgængelig internt i hver celle. Algoritmerne implementeres i en systemniveausimulator og testes med både konstant og varierende antal brugere under lave og høje belastninger. Den bedst præsterende algoritme reducerer mærkbart intercelle‑interferens ved at undgå overlap og forbedrer dermed signal‑til‑interferens‑plus‑støj‑forholdet (SINR). Desuden foreslås en metode, der lader cellen justere sin belastning dynamisk efter øjeblikkelige behov estimeret via brugernes feedback.
Orthogonal Frequency Division Multiple Access (OFDMA) is the access scheme selected by 3GPP for the downlink in LTE UTRAN. Because OFDMA provides intra‑cell orthogonality, signals from users in the same cell do not interfere. The main issue is inter‑cell interference from neighboring cells, which can limit throughput for users near the cell edge. Under light traffic, a fractional load strategy can transmit on only part of the available physical resource blocks (PRBs—small time‑frequency chunks) to avoid overlap between cells and reduce interference. However, choosing which PRBs each cell should use is non‑trivial. This thesis develops autonomous resource‑selection algorithms that allocate PRBs using only information available within each cell. The algorithms are implemented in a system‑level simulator and tested with both constant and variable numbers of users, under low and high loads. The best‑performing algorithm significantly reduces inter‑cell interference by avoiding overlapping PRBs and thereby improves the Signal‑to‑Interference‑plus‑Noise Ratio (SINR). In addition, a new method enables dynamic adjustments of the cell’s load based on instantaneous requirements estimated through user feedback.
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