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Packet Data Flow Control in Evolved WCDMA Networks
Linköping University, Department of Electrical Engineering.
2005 (English)Independent thesis Basic level (professional degree), 20 credits / 30 HE creditsStudent thesisAlternative title
Flödeskontroll av Paketdata i Vidareutvecklade WCDMA Nätverk (Swedish)
Abstract [en]

The key idea of the new, shared high-capacity channel HSDPA, is to adapt the transmission rate to fast variations in the current radio conditions, thus enabling download peak data rates much higher than what WCDMA can offer today. This has induced a need for data that traverses the mobile network to be intermediately buffered in the Radio Base Station, RBS. A scheduling algorithm then basically selects the user with the most beneficial instantaneous radio conditions for access to the high-speed channel and transmission of its data over the air interface.

The purpose of this thesis is to design a flow control algorithm for the transmission of data packets between the network node directly above the RBS, the RNC, and the RBS. This flow control algorithm should keep the level of the buffers in the RBS on such a level that the air interface may be fully utilized. Yet it is not desirable with large buffers since e.g., this induces longer round-trip times as well as loss of all data in the buffers whenever the user moves to another cell and a handover is performed. Theoretical argumentations and simulations show that both of these requirements may be met, even though it is a balancing act.

Suggested is a control-theoretic framework in which the level in the RBS buffers are kept sufficiently large by taking into account predictions of future outflow over air and by using methods to compensate for outstanding data on the transport network. This makes it possible to keep the buffer levels stable and high enough to fully utilize the air interface. By using a more flexible adaptive control algorithm, it is shown possible to reach an even higher utilization of the air interface with the same or even lower buffering, which reduces the amount of data lost upon handovers. This loss is shown to be even more reduced by actively taking system messages about upcoming handover events into account as well.

Place, publisher, year, edition, pages
Institutionen för systemteknik , 2005. , 74 p.
Keyword [en]
Flow Control, Buffer Management, HSDPA, WCDMA, UMTS, 3G
National Category
Engineering and Technology
URN: urn:nbn:se:liu:diva-4881ISRN: LiTH-ISY-EX–05/3652–SEOAI: diva2:20795
Subject / course
Automatic Control and Communication
Available from: 2005-11-23 Created: 2005-11-23 Last updated: 2012-12-11

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