Endre søk
RefereraExporteraLink to record
Permanent link

Direct link
Referera
Referensformat
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Annet format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annet språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf
Link Adaptation Improvements for Long Term Evolution (LTE)
Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap.
2009 (engelsk)Independent thesis Advanced level (degree of Master (Two Years))Oppgave
Abstract [en]

The Long Term Evolution (LTE) link adaptation is based on measured instantaneous Signal to Interference and Noise Ratio (SINR) which is used for selecting Modulation and Coding Scheme (MCS) for transmissions. In addition, depending on the scheduler, SINR may be used to determine which users are scheduled for a certain transmission time interval and on which frequency resources. The measured SINR can be inaccurate due to measurement errors, rounding errors due to quantization of the SINR values, and delay from time of measurement until the actual data transmissions. To compensate for SINR inaccuracies, the SINR can be adjusted by a certain offset before being used for link adaptation and scheduling. This offset value, referred to as the link adaptation margin in this thesis, can be a fixed value common to all the users in the system at all times or adaptively adjusted for each user based on some algorithm via a feedback loop, referred to as differentiated link adaptation. This thesis tries to improve the system performance for LTE downlink and uplink by using differentiated link adaptation based on packet error occurrences of each user as feedback. The performance of the differentiated link adaptation was compared to the best performance that is achievable using a fixed link adaptation margin. We investigated the influence of several parameters on the link adaptation error characteristics, such as settings for SINR estimation, scheduling algorithms, traffic patterns. It was shown that there are error clusters, but that these are short and difficult to react to on time. A performance gain was only possible in the downlink for FTP traffic with a proportional fair in time and frequency (PFTF) scheduler which was the scenario with the largest variations with regards to both scheduling and traffic model. It was seen that the gains of using differentiated link adaptation increased in the downlink as the transmissions got more random. For more stable situations, a fixed link adaptation margin performed better. The uplink performance was worse with differentiated link adaptation than with a fixed optimized link adaptation margin. This could be because the uplink SINR estimation was much better than in the downlink, with low estimation error variance, in which case frequent SINR adjustments could make the situation worse off.

sted, utgiver, år, opplag, sider
2009. , s. 73
Emneord [en]
LTE, Long Term Evolution, link adaptation, Adaptive modulation and coding
HSV kategori
Identifikatorer
URN: urn:nbn:se:bth-6072Lokal ID: oai:bth.se:arkivexF3A3D240F97953ACC12576A10044DDB2OAI: oai:DiVA.org:bth-6072DiVA, id: diva2:833491
Uppsök
Technology
Veileder
Merknad
Thesis conducted at Ericsson research, Luleå under the supervision of Dr. Sara Landström (sara.landstrom@ericsson.com).Tilgjengelig fra: 2015-04-22 Laget: 2010-01-04 Sist oppdatert: 2015-06-30bibliografisk kontrollert

Open Access i DiVA

fulltekst(2545 kB)516 nedlastinger
Filinformasjon
Fil FULLTEXT01.pdfFilstørrelse 2545 kBChecksum SHA-512
3f8e91c78f25036c4b6565df0382353ebf65b2f420c08344ff1131687012ffe8c2070d9f02e956f31851cc79ccca8a9bf7130abf3248e7a6fb3806ff7e59d7b7
Type fulltextMimetype application/pdf

Av organisasjonen

Søk utenfor DiVA

GoogleGoogle Scholar
Totalt: 516 nedlastinger
Antall nedlastinger er summen av alle nedlastinger av alle fulltekster. Det kan for eksempel være tidligere versjoner som er ikke lenger tilgjengelige

urn-nbn

Altmetric

urn-nbn
Totalt: 2617 treff
RefereraExporteraLink to record
Permanent link

Direct link
Referera
Referensformat
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Annet format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annet språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf