10.1 Introduction

Future communication systems are intended to support a wide range of applications that require different levels of quality of service (QoS). Unlike the current single-service network, future multimedia applications will require multiple-service operation in integrated network environments.

The beyond-3G communication network concept involves the coexistence of all the different network technologies. Thus, heterogeneity will play a major role in future networks and operating system environments. Highly-differentiated access technologies allow a user terminal to exploit a number of platforms to access heterogeneous services. Application data transmitted over heterogeneous networks will therefore experience systems with limited and varying capacity. Under this condition, the multimedia performance-enhancement algorithms will need to be optimized in order to achieve optimal QoS for multimedia over end-to-end systems. In particular, QoS parameter-mapping will become important as different networks provide different QoS. When multimedia is transmitted from a network with poor performance to a network with good performance, problems will arise in guaranteeing the required quality for the end user.

In this chapter, the issue of supporting optimal quality for multimedia applications in heterogeneous network scenarios is addressed. First, a generic QoS infrastructure that guarantees multimedia quality in inter-networked operation is described. The QoS infrastructure is designed in a generic manner to enable the accommodation of evolving wireless communication systems. The proposed infrastructure uses a layered architecture, which enables cross-protocol layer optimization as well as cross-network optimization for multimedia quality. Operation of the proposed infrastructure is demonstrated through the design of a QoS parameter-mapping emulator. Furthermore, MPEG-4-encoded video is transmitted over the simulated heterogeneous environment, and the results show the importance of such a QoS infrastructure in maintaining acceptable multimedia quality for the end user.