 that actually will implement cdma2000 and W-CDMA are de- veloped, many issues will still need to be resolved. Standards are not intended to re- solve all questions but to answer some and define others, which are then resolved in design specifications and real-world experience. As 3G services become a reality, will learn more and improve standards, specifications, and equipment. At a minimum, vendors will need to allocate enough carriers to data-only (DO) or to voice-and-data use to support variable demand for voice and data. 21.1.1 Voice The addition of a reverse pilot and of other aspects of the 3G standard is expected to increase voice capacity per cell by about half as cdma2000 replaces cdmaOne. 1 How- ever, fully realizing this capacity gain relies on user terminals that use the reverse pi- lot, and it is reasonable to expect that the existing base of cdmaOne phones will not vanish quickly, especially in the current economy. If demand increases before this creased capacity is realized, bottlenecks could create poor service over the air interface. Another uncertain element is the effect of cdma2000 3x services. These services will offer 5 MHz of bandwidth spread over three 1.25-MHz cdmaOne carriers (with guard bands). A cdma2000 3x needs to operate at its own frequency; it cannot be deployed on Superscript(1)Some industry estimates say that capacity may double, but we believe that a 50 percent in- crease is more likely. 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. Wireless Data Services Key Data Concepts top of existing 1x carriers. However, there is an option called cdma2000 multicarrier (MC) that would coordinate three 1x carriers, supporting an increased data rate. In the multicarrier specification, orthogonal codes are maintained, SO interference on each 1x band and on the multichannel band, which is effectively 3x, should be mana