divi- sion multiplexing (OFDM). The pilot system achieved the impressive speed of 34 Mbps, matching the level of service provided by E-3 lines. The goal of the standard is to reach 155 Mbps, comparable with OC-3 rates. This is over a thousand times faster than wire- less data rates available today. Despite the changing technologies and goals, some say that 4G systems may be available as early as 2006. Japan has set a requirement that all Internet service 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. CDMA Now and in the Future CDMA Now and in the Future providers (ISPs) support IPv6 by 2006, and this, presumably, would include wireless service providers. It remains to be seen if other nations will follow suit. IPv6 solves many problems of today's networks. It offers a single stack of communi- cations protocols that provides these benefits, overcoming limitations of IP version 4 (IPv4, the current version), ATM, and other services: Enough addresses for the foreseeable future, whereas IPv4 is running out of addresses Addressing systems that support virtual addresses and mobility, making it easier to pre- vent tromboning and to deploy flexible networks Built-in security Support for independent definitions of quality of service (QoS) for voice, video, and vari- ous types of data services sharing the same packet network The downside of IPv6 is simply that it will require the replacement of every router and many other pieces of equipment on the Internet. If backward compatibility works, com- puters running IPv4 will work on IPv6 networks. However, backward compatibility, even when designed into the new system, always brings engineering challenges. Estimates for when 4G services will arrive vary from 2006 to 2020. The initiative got several boosts in late 2001 and early 2002, including a major commitment of investors in Japan, who see it as the lo