| Summary: | The performance of the backbone bearer service of the Universal Mobile Telecommunications
System (UMTS), or of its 2.5G precedent General Packet Radio Service (GPRS),
has a considerable impact on the end-to-end Quality of Service (QoS) observed by a traffic
flow. The purpose of this thesis is to provide a basic methodology for provisioning QoS
in this backbone network by using Differentiated Services (DiffServ), which is an IP-based
QoS technology. It focuses on two important issues. First, a basic plan for QoS mapping
from one system to another is presented. Second, the structure of a DiffServ-based UMTS
backbone router is studied which can provide the appropriate functionality of forwarding
packets with PHB s equivalent to the original UMTS QoS.
In particular, three major components of a DiffServ router, including the scheduler,
the dropper, and the meter, have been addressed and novel algorithms have been proposed
to make them suitable for a UMTS backbone router. This thesis proposes an efficient, fair
scheduling and link sharing system called DDB - FFQ , which has the capability of assigning
decoupled delay bounds and bandwidth allocations. This paper also studies the implementation
of Random Early Detection (RED) on a shared-memory buffer and proposes new
schemes that have improved packet loss ratios. The performance of a multiple node backbone
network is then evaluated by using the OPNET simulation package. The results show
that in terms of delay and allocated bandwidth, the routers are able to provide the PHBs
considered for each traffic aggregate. They also illustrate the link sharing capability of the
router in times of congestion.
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