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Figure 2.3 attempts to illustrate how the core network has its own migration, and it can be done independently of the air interface. Generally, it can be said that the full 3G core network of cdma2000, based upon Mobile IP, is more advanced than GPRS and is probably closer to WCDMA phase 2 (introduces an all -IP core network). Some operators might choose to skip the Simple IP step and implement cdma2000 with Mobile IP directly.
The cdmaOne radio interface IS-95A supports voice calls and data rates of up to 14.4Kbps. SMS is also available but has never become the success that it has with GSM. With IS-95B, the overall functionality is improved, but the major step is increased data rates. By combining several 9.6 or 14.4 channels, up to 115.2Kbps can be achieved. As always, this rate is lower in reality and is limited by handsets and the overall capacity of the system. In Japan, services that have bit rates of up to 64Kbps have been launched.
Figure 2.3 cdmaOne evolution.
Most cdmaOne networks are implemented in the 800Mhz and 1900Mhz (PCS) bands and are most widespread in the United States, Korea, and Japan. In the United States, operators include Sprint PCS and Verizon, and cdmaOne has experienced a rapid growth in recent years. When considering the introduction of 3G, the United States has a bit of a problem. The PCS band already occupies the 2GHz frequency band that the International Telecommunication Union (ITU) recommends. Therefore, the 3G migration for cdmaOne works in the existing spectrum, rather than requiring a new spectrum to be freed.
With cdmaOne technology, each carrier (channel) is 1.25MHz wide (a GSM carrier is 200kHz and a TDMA carrier is 30kHz). The cdma2000 1X radio interface is backward compatible with IS-95A and IS-95B and therefore uses the same 1.25MHz channels. Through improved modulation, power control, and overall design, cdma2000 1X provides average bit rates of up to 144Kbps (commercial deployments will show the actual values) and also gives the operator more capacity, both for voice and for data. Developers then introduce the cdma2000 3G technology as an overlay to the existing system, where each user has three 1.25MHz channels. The terminology differs, and some call cdma2000 1X a 3G system while some compare it with GPRS and call it “evolved 2G or 2.5G.” People sometimes call cdma2000 multicarrier “cdma2000 3X” or “cdma2000 1X evolution.”
The core network of cdmaOne is based on the same IS-41 core network as TDMA. The vision of the cdma2000 3G core network is to have a network architecture that is solely based on Internet Engineering Task Force (IETF) IP standards with seamless connectivity (called Mobile IP). We will describe Mobile IP in Chapter 4, ‘‘3G Wireless Systems.”
In Japan, NTT DoCoMo was interested early on in introducing high-speed multimedia services to its subscribers. Because Japan was isolated with its PDC system for 2G, NTT and other Japanese companies wanted to make sure that this situation would not happen again. Early on, there was a close cooperation between different companies across the world in order to facilitate more of a global standard for 3G than what had been around for 2G. In the beginning, the Japanese, Association of Radio In Business (ARIB), and European Telecommunications Standards Institute (ETSI), suggestions for the standard diverged somewhat. After a few rounds of negotiations and harmonization, they agreed to proceed with a common standard in a global forum: the Third-Generation Partnership Project (3GPP). During this time, NTT DoCoMo introduced its own packet data add -on to PDC, P-PDC, on which I-Mode (described later in this chapter) runs. The main difference between the Japanese migration and the rest of the world’s migration is that the step to 3G is much faster.
Japanese operators plan to introduce commercial WCDMA services during spring/summer 2001, which is ahead of Europe and the rest of Asia. The Japanese market was somewhat left out in 2G, and it definitely does not want to repeat that record. The expected strong Japanese market is also likely to fuel the Japanese device manufacturers, and there certainly will be many exciting devices emerging from them.
WAP, Bluetooth, and Other Related Evolutions
So far, we have only talked about the networks and how they will evolve. Other technologies must evolve in parallel, however—technologies that can operate independently of EDGE, cdmaOne, WCDMA, and so on. We commonly call these technologies bearers, and they enable the transport of information over the air.
In order to transport information over a bearer, there must be mechanisms for deciding how and where to send the information. Protocols such as IP, TCP, User Datagram Protocol (UDP), and Wireless Session Protocol (WSP) perform some of these tasks, and we describe these protocols in more detail in Chapter 6, “Unwiring the Internet.” These protocols also can make sure that the information is received reliably and in order. The World Wide Web Consortium (W3C) standardizes most of the Internet protocols, and there is currently work going on to improve protocols such as TCP in order to better handle the wireless environments. WAP is a suite of protocols that will evolve as we get larger displays and more CPUs for devices. You must understand that WAP can evolve independently of the bearers, and WAP can run over SMS and GSM as well as on GPRS, Bluetooth, cdma2000, and on most other networks. We will provide more information about WAP in Chapter 7, “The Wireless Application Protocol (WAP),” and about Bluetooth in Chapter 5, “Bluetooth—Cutting the Cord!”