comm did not keep the CDMA standard proprietary. Only the patents on the chips are proprietary. ANSI, with the assistance of IEEE and other organizations, took the CDMA standard for cellular telephony through multiple revisions as Interim Standard 95 (IS-95) and then approved the standard for North American cdmaOne. The ITU defined the third generation (3G) of mobile telephony standards and requested proposals for standards to meet its re- quirements. The CDMA Development Group (CDG), an industry group more on the political and promotional side of things than IEEE is, proposed cdma2000, a standard based on cdmaOne but meeting the requirements of ITU's 3G. There is much more than this to the story of CDMA for 3G, and we will discuss it again later in this chapter. Even when we know what the official status of a standard is, there may be confusion about what is being standardized. This is discussed in the next subsection. 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. General Cellular Standards General Cellular Standards 9.1.2 Standards and interfaces Standards can be confusing. One of the best ways to get clear about them is to ask the question, What interface is being standardized? We can think of an interface as the de- fined communication between two systems. Expanding on this idea, we can picture an interface as a gap between two systems that is being crossed and the standard as the agreed-on way to get information across the gap. At a detail level, each single standard specifies one interface. However, we often use the term standard to mean a set of stan- dards. For example, we talk about the Global System for Mobility (GSM) standard. Ac- tually, the set of standards in GSM defines many interfaces: the radio-air interface from base station to cell phone; the interface between the base station and the mobile switching center (MSC), the s