10
Packet Scheduling
10.1 Introduction
This chapter presents the radio access algorithms for supporting packet switched services and analyses their performance. Such services are, for example, messaging, email, WAP/web browsing, streaming video or Voice over IP. This chapter is organized as follows. Packet data protocols are first discussed in Section 10.2. The network delay aspects in terms of round trip time are analysed in Section 10.3. The transport channels and the user specific packet scheduler are introduced in Section 10.4. The cell specific packet scheduler algorithms are discussed in Section 10.5. The packet data system performance results are presented in Section 10.6 and the application performance results in Section 10.7. The services in general are introduced in Chapter 2.
All four UMTS traffic classes—from background to conversational—can be supported by WCDMA radio networks. See Chapter 2 for the introduction of the traffic classes. Background and interactive traffic classes do not require any guaranteed minimum bit rate and they are transmitted through the packet scheduler. The streaming class requires a minimum guaranteed bit rate but tolerates some delay, and packet scheduling can be utilized for streaming. The conversational class is transmitted without scheduling on dedicated channel DCH. The traffic classes and their mapping to transport channels are shown in
