"Alice came to a fork in the road. 'Which road do I take?' she asked. 'Where do you want to go?' responded the Cheshire cat 'I don't know,' Alice answered. 'Then,'said the cat, 'it doesn't matter.'"

Lewis Carroll, Alice in Wonderland

In June 2002 the worldwide number of wireless subscribers finally reached a long anticipated 1 billion, beating even the most optimistic analyst's estimates by almost a year. The growth rate of Internet hosts is not far behind, pushing 200 million at the time of this book's publication. The important conclusions, however, can be drawn from the percentage of total wireless users who are also using the Internet. According to the latest analyst's research, close to 80 percent of Internet users are also cellular wireless subscribers, and the percentage of business users for both is about 40 percent.

Not surprisingly, there is a growing interest in wireless data for both commercial and residential applications—especially in the context of the next generation systems such as CDMA2000, GPRS, UMTS, EDGE, and WLAN. One of the most prominent recent trends in commercial landline data communications is the use of virtual private networking (VPN) to gain secure connection to remote private networks over public shared infrastructures such as Internet. The obvious next step is to apply the benefits of landline VPN technologies to mobile environments, creating Mobile Virtual Private Networks (MVPNs) that allow secure pervasive private communications over a variety of shared mobile networks offered by wireless operators and wireless Internet service providers (WISPs).

What This Book Is About

We are at the stage in the wireless data communications life cycle when most of its underlying technologies have reached maturity or at least have stabilized in standards. Third-generation wireless systems, which defined new services and provided high-speed data and multimedia support, have been standardized and are being rapidly deployed all over the world (albeit with some expected early-growth problems, unfortunately, perversely associated to financial issues due to unprecedented financial speculation and overexcitement around new technologies at the end of the past millennium). All of these systems include support for packet-switched data communications, as opposed to their predecessors, which relied on circuit-switched technologies. The important aspects of these systems include not only the potentially higher throughput, which is often relatively modest during initial rollouts and under certain circumstances, but also availability, always-on capabilities, higher efficiency, and a strong foundation for the delivery of new services. Packet data (covered in Chapter 4), effectively brought wireless networks one step closer—in functionality, throughput, and resource utilization—to wireline data networks while preserving and enhancing one of its most important features of wireless communications: mobility.

Additionally, advancements in virtual private networking technologies allowed the easy use of public shared wireline infrastructures such as the Internet to securely transmit private data traffic, thus extending the reach of private networks by allowing remote users to connect to remote resources, information, and services. These advancements have mainly occurred in the past 3 years, so we believe now is the best time to come up with a comprehensive guide on the subject that would allow the reader to study it on any desired level of complexity and perhaps help in addressing research and development efforts in the most appropriate direction.

The focus of the book is remote access to private networks in the wireless environment achieved by the use of technology called Mobile Virtual Private Networking. Most of the discussion is centered on the second- and third-generation cellular systems—supporting packet-switched data communications—and Wireless LANs. These systems, including CDMA2000, GPRS, and UMTS, are being deployed at this writing and are expected to proliferate throughout the world during the next few years. With this text we strived to provide a comprehensive guide on the subject complete with background on both wireline data and cellular wireless communications. The book touches on special topics such as support for Mobile VPN over integrated cellular/WLAN infrastructures and the support of advanced Mobile IP services. In the second part of the book we introduced a new approach to classification of VPN and other private network access methods used in GPRS, UMTS, and CDMA2000 and discussed a variety of other complex issues in the field of wireless data. We supplemented the material with a healthy amount of practical network design scenarios and real-life examples (specifically in Chapters 6, 7, and 9). The book also provides a look at the open issues and future trends in wireless data communications in general and at private network access over untethered medium in particular.