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A study of the system impact from different approaches to link \t adaptation in WLAN
KTH, School of Information and Communication Technology (ICT).
2015 (English)Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
Abstract [en]

The IEEE 802.11 standards define several transmission rates that can be used at the physical layer to adapt the transmission rate to channel conditions. This dynamic adaptation attempts to improve the performance in Wireless LAN (WLAN) and hence can have impact on the Quality of Service (QoS) perceived by the users. In this work we present the design and implementation of several new link adaptation (LA) algorithms. The performance of the developed algorithms is tested and compared against some existing algorithms such as Minstrel as well as an ideal LA.

The evaluation is carried out in a network system simulator that models all the procedures needed for the exchange of data frames according to the 802.11 standards. Different scenarios are used to simulate various realistic conditions. In particular, the Clear Channel Assessment Threshold (CCAT) is modified in the scenarios and the impact of its modification is also assessed. The algorithms are tested under identical environments to ensure that the experiments are controllable and repeatable. For each algorithm the mean and 5th percentile throughput are measured under different traffic loads to evaluate and compare the performance of the different algorithms. The tradeoff between signaling overhead and performance is also evaluated. It was found that the proposed link adaptation schemes achieved higher mean throughput than the Minstrel algorithm. We also found that the performance of some of the proposed schemes is close to that of the ideal LA.

Abstract [sv]

IEEE 802.11-standarderna definierar flera överföringshastigheter som kan användas vid det fysiska skiktet för att anpassa överföringshastigheten till kanal förhÅllanden. Denna dynamiska anpassning försöker förbättra prestandan i wireless LAN (WLAN) och därmed kan ha inverkan på Quality of Service (QoS) uppfattas av användarna. I detta examensarbete presenterar vi utformningen och genomförandet av flera ny link adaptation (LA) algoritmer. Prestandan hos de utvecklade algoritmer testas och jämförs med vissa befintliga algoritmer så som Minstrel liksom en ideal LA.

Utvärderingen genomförs i ett nätverkssystem simulator som ger alla de förfaranden som behövs för utbyte av dataramar enligt 802.11-standarderna. Olika scenarier används för att simulera olika realistiska förhållanden. Algoritmerna ar testade under identiska miljöer för att experimenten är styrbar och repeterbar. För varje algoritm genomströmningen mättes under olika trafikbelastningar för att utvärdera och jämföra resultaten för de olika algoritmer. Den avvägning mellan signalering overhead och prestanda utvärderas också

Det konstaterades att de system som föreslas link adaptation uppnås högre genomsnittlig throughput än Minstrel algoritm. Vi fann också att utförandet av vissa av de föreslagna systemen är nära den av ideal LA.

Place, publisher, year, edition, pages
2015. , 148 p.
TRITA-ICT-EX, 2015:106
Keyword [en]
WLAN, link adaptation, medium reuse, channel estimation.
Keyword [sv]
WLAN, link adaptation, medium reuse, channel estimation.
National Category
Computer and Information Science
URN: urn:nbn:se:kth:diva-177504OAI: diva2:873103
Available from: 2015-11-25 Created: 2015-11-23 Last updated: 2015-11-25Bibliographically approved

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