Channel Quality Information Reporting and Channel Quality Dependent Scheduling in LTE
Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
Telecommunication systems are under constant development. Currently 3GPP is working on an evolution of the 3G-standard, under the name 3G Long Term Evolution (LTE). Some of the goals are higher throughput and higher peak bit rates. A crucial part to achieve the higher performance is channel dependent scheduling (CDS). CDS is to assign users when they have favorable channel conditions. Channel dependent scheduling demands accurate and timely channel quality reports. These channel quality indication (CQI) reports can possibly take up a large part of the allocated uplink. This thesis report focuses on the potential gains from channel dependent scheduling in contrast to the loss in uplink to reporting overhead.
System simulations show that the gain from channel dependent scheduling is substantial but highly cell layout dependent. The gain with frequency and time CDS, compered to CDS in time domain only, is also large, around 20\%. With a full uplink it can still be a considerable gain in downlink performance if a large overhead is used for channel quality reports. This gives a loss in uplink performance, and if the uplink gets to limited it will severely affect both uplink and downlink performance negatively.
How to schedule and transmit CQI-reports is also under consideration. A suggested technique is to transmit the CQI reports together with uplink data. With a web traffic model simulations show that a high uplink load is required to get the reports often enough. The overhead also gets unnecessary large, if the report-size only depends on the allocated capacity.
Place, publisher, year, edition, pages
Institutionen för systemteknik , 2007. , 77 p.
LTE, Scheduling, CQI, Channel dependent
IdentifiersURN: urn:nbn:se:liu:diva-11033ISRN: LiTH-ISY-EX--07/4067--SEOAI: oai:DiVA.org:liu-11033DiVA: diva2:17485