Visual Media Coding and Transmission

9.1 Introduction

Third-generation (3G) access networks were designed from the outset to provide a wide range of bearer services with different levels of quality of service (QoS) suitable for multimedia applications with bit rates of up to 2 Mbps. The bearer services are characterized by a set of transport channel parameters, which include: transport block size, CRC code length, channel coding schemes, RLC mode, MAC type, transport time interval, rate matching, and spreading factor. The perceived quality of the application seen by the end user is greatly affected by the settings of these transport channel parameters. The optimal parameter settings depend highly on the characteristics of the application, the propagation conditions, and the end-user QoS requirements. This section will examine the effect of these transport channel (network) parameter settings upon the performance of MPEG-4-coded video telephony and AMR-WB speech applications, and will investigate the optimal radio bearer design for real-time speech and video transmission over UTRAN, GPRS, and EGPRS. The influence of the network parameter settings and different channel and interference conditions upon the received video/speech quality and network performance will be assessed experimentally using the real-time UMTS, GPRS, and EGPRS emulators described in Chapter 8. Furthermore, differences between packet-switched and circuit-switched radio bearer configurations for conversational video applications over UMTS will be ...