1.1 Background
There seemed to be a great sparkle of 3G communication lifestyle when ITU-R (ITU-Radio communication) gave birth to the IMT-2000 (International Mobile Telecommunications 2000) in 1996. In the near future, the following scenes could be imagined. People can watch video streams more fluently, browse websites from the Internet more smoothly, and also download bulky files as fast as in the wired-network using their diverse mobile devices with up to 2Mbps bandwidth supported in 3G system. Hereafter, the mobile communication services provided by 3G are not only voice communications but also tremendous amount of data communications.
Several 3G-system standards are proposed. One of the most prospective 3G systems is UMTS (Universal Mobile Telecommunication System) that is proposed by ETSI (European Telecommunication Standard Institute) due to its well system compatible, open-system, vendor-supported and other beneficial features. Therefore, this study would base on the UMTS mobile communication system. Moreover, since there are many mobile communication services would share the limited 3G network resources, the QoS of 3G becomes an important issue. For UMTS, 3GPP has proposed the UMTS QoS architecture and defined four different kinds of QoS classes such as conversational, streaming, interactive, and background class. Each class application has its own bearer service attributes to construct its QoS profile [11].
1.2 Motivation
Because of the limitation of 3G mobile communication bandwidth and the QoS profiles required by diverse mobile services, a proper queueing mechanism in an UMTS core network would be required to support a QoS profile to each mobile
service. In general, the conversational or streaming service applications are most time sensitive and should have the higher priority to allocate 3G bandwidth to ensure voice or video stream transmission smoothly and sequentially. Moreover, the time delay seems not so important for the interactive and background applications in 3G mobile network. Additionally, the packet transmission sequences of these two type applications seem not to be an issue for these two type applications.
Figure 1.1 Worldwide Revenue from Non-voice Services [21]
The interactive/background mobile applications include E-Mail, SMS (Short Message System), MMS (Multimedia Message System), and FTP. They would become more and more popular and gain more revenues year by year, shown in Figure 1.1. In UMTS networks, the interactive/background services are supported by a packet-switching transmission and these two services are delay-tolerant applications.
Although some queueing schemes have been proposed for 3G conversational and streaming services, but the features of interactive/background services are different
from conversational/streaming services. These proposed queueing schemes for 3G conversational/streaming services might not be proper for the interactive/background services. Since the interactive/background applications are getting important, it is necessary to propose a queueing scheme for interactive/background applications to support the QoS of interactive/background services.
This study would focus on the packet-switching mobile services and proposes a preemptive queueing mechanism to operate in an UMTS core network gateway. With the proposed queueing mechanism operation, the important mobile services with higher transmission priority could preempt the bandwidth of lower priority mobile services to receive better transmission performance.
1.3 Objective
This study would base on the role that user plays to propose a preemptive queueing scheme to support the background service operations in an UMTS core network gateway. According to the users’ importance, different transmission priorities would be assigned to their UMTS background applications to satisfy the required QoS profiles for UMTS users. The proposed queueing scheme would provide an effective mechanism of differentiated service. Several assumptions in this study would be specified as the following:
1. The proposed role-based queueing scheme would aim at the UMTS background applications. The background traffic is generally considered as the traffic type of the lowest delay-sensitive data and the highest packet-loss-sensitive among these four QoS class [17].
2. The proposed role-based queueing scheme would be operated in an UMTS core network gateway. Its operation domain would be on the packet switching network which corresponds to All-IP Core Network domain in UMTS R5 architecture [20].
The role-based queueing (RBQ) scheme would base on the status of each user to the different weighted priority to each UMTS background application. There exists a mapping between the status of mobile user and the transmission priority of an UMTS background application. The users’ roles can be divided into three types, such as:
Member, VIP and Emergency, each of them has a distinct specific priority from low to
high. Therefore, mobile users can choose distinct roles with paying cost to have one relative guarantee performance to deliver traffic packets with the RBQ in an UMTS core network. When the background UMTS packets enter the UMTS core network gateway, the RBQ scheme would base on the priorities received by the background applications to forward the applications’ packets. With RBQ scheme operating in an UMTS core network gateway, differentiated services would be provided according to the role of mobile users. The limited UMTS network bandwidth could be utilized efficiently for the UMTS background applications within the UMTS core network.
1.4 Chapters and Sections
In the following chapters and sections, the overview of UMTS architecture, Internet QoS, and UMTS QoS classes would be reviewed in Chapter 2. A role-based preemptive queueing scheme, called RBQ, in an UMTS core network gateway would be proposed in Chapter3. In Chapter 4, several scenarios would be simulated. The simulation results would be collected and analyzed. At last, the conclusion on this study would be described in Chapter 5.