enters (MSC). The last two chapters in Part 4 discuss data services for cellular subscribers. Chapter 20, "Short Message Service (SMS)," discusses the SMS system, which carries small user messages over the cellular signal channel without establishing a circuit, and its descendants, enhanced message service (EMS) and multimedia Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. Key Data Concepts Key Data Concepts service (MMS), which add small voice and video attachments. In Chap. 21, "Wireless Data Services," we discuss the high- bandwidth data services being deployed in 2.5G and 3G cellular systems. Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. Source: CDMA CAPACITY AND QUALITY OPTIMIZATION Chapter Quality of Service (QoS) The convergence of voice and data is a key issue for code division multiple access (CDMA) quality and capacity, particularly with the deployment of third-generation (3G) systems. QoS is the most crucial challenge for this convergence. Overall, conver- gence is the term used for the integration of the services, industries, and networks that provide voice, video, and data services around the world. Television-quality video has not yet become a major issue for wireless communications, so our primary concern is with voice and data convergence. The public switched telephone network (PSTN) and the Internet developed separately. Each of them is designed to provide high-quality ser- vice for the services it offers: The PSTN offers real-time audio with good voice quality for telephone calls, and the Internet offers slow but very reliable transmission of data. At the same time, each system performs relatively poorly for the type of service was not designed to p