33.2 WIRELESS INTERNET ROADMAP: GENERATIONS OF WIRELESS NETWORKS

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First generation wireless networks: The first generation wireless networks were analog systems such as AMPS (Advanced Mobile Phone System), TACS (Total Access Control System), and NMT (Nordic Mobile Telephony). which had a large installation base in North America and Europe. These systems supported mainly voice communication and had very limited data capability. Because of the limited, radio spectrum, the capacities of these systems were limited, and expansion was a problem. Slowly, these systems were replaced by digital systems.

The first Generation wireless networks were analog systems that supported only voice communication. These systems have been replaced by digital systems in most countries.

Second generation wireless networks: The 2G (second generation) networks, which are presently in operation in all countries, are digital systems. These systems include:

Global System for Mobile Communications (GSM)-based networks which were initially deployed in Europe. Subsequently, GSM standards have been adopted by many other countries in Asia and Africa. GSM systems also are being introduced in North America.
TDMA systems based on IS 136 and IS 41 (IS stands for interim standard)
CDMA systems based on IS 95 and IS 41 deployed extensively in the U.S., China, and Korea.

These systems typically support data rates less than 28.8 kbps. To access the Internet at these data rates is not a good experience. However, to retrieve focused information (for example, stock quotes, bank information, sports/entertainment news, and travel information these data rates will suffice. The TCP/IP protocol suite cannot run and hence on the mobile devices because of its high protocol overhead, so new protocols such as wireless application protocol (WAP) and i-mode have been developed. The WAP stack with a microbrowser runs on the mobile device. A special markup language known as Wireless Markup Language (WML) has been developed to create content that can be accessed through the WAP protocols from mobile devices.

The second generation wireless networks are digital systems that support data services with data rates up to 28.8kbps in addition to voice services. GSM, TDMA, and CDMA networks presently in operation in most countries are examples of 2G wireless networks.

2.5G wireless networks: The two-and-a-half generation (2.5G) wireless networks will evolve from the 2G networks to support data rates in the range 64-144 kbps, using technologies such as general packet radio service (GPRS) and cdma2000-1x. With the higher data rates, reasonably high-quality graphics and reasonably good quality video can be supported. With 2.5G systems, the mobile devices can access multimedia content.

Third generation wireless networks: The 3G wireless networks will be capable of supporting very high data rates in the range 384kbps-2.048Mbps to provide multimedia services to mobile users. With these data rates, applications such as two-way video conferencing, high-quality audio (music) downloading, and high-resolution graphics can be supported. The 3G systems will evolve from the GSM or CDMA system.

2.5G wireless networks support data services with data rates in the range 64-144 kbps. General packet radio service (GPRS) and cdma2000-1x are examples of 2.5G networks.

The roadmap for evolution to 3G is shown in Figure 33.1. It needs to be noted that standardization process has not reached a stage wherein a single technology will be chosen for 3G. This is because the 3G systems should have backward compatibility with the existing cellular infrastructure, and there is wide range of technologies today. Hence, it is likely that there will be variety of technologies under the 3G umbrella. Regional standardization bodies such as ETSI in Europe, CWTS in China, T1 in the U.S., and TTA in Korea formed the 3G Partnership Project (3GPP) group to bring harmony to the various conflicting proposals submitted for standardization.

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Figure 33.1: Evolution to 3G.

3G wireless networks will be capable of supporting data rates in the range 384-2.048 kbps to provide multimedia services to mobile users. 3G networks will evolve from the present GSM and CDMA networks.

For deploying 3G systems, there are many issues to be resolved, such as spectrum allocations, the standards for protocol stacks, and the standards for developing content to be accessed by mobile devices. During the next few years, there will be a lot of activity in this direction. In the following sections, we will review the present trends on these aspects.

Note

There is no single international standard for 3G networks mainly because the 3G networks evolve from the present mobile networks, which follow different standards in different countries.

33.2.1 Wireless Access Devices

The wireless Internet access device can be any of the following: mobile phone (cell phone or hand phone, as it is called in some countries), pagers, two-way radios, personal communicators, smart phones, desktops, laptops, palmtops, Personal Digital Assistants, WebTV, and Internet kiosks installed in rural or remote areas. The important point to note here is that each of these devices has different processing capabilities and different platform technologies. All these devices vary in terms of processing power, primary and secondary storage capacity, display size and resolution, battery capacity, input device capability and so on. Not all devices have a full-fledged operating system residing on them-some only have a mobile operating system (such as Win CE, Palm OS, OS-9, Symbian or Java OS). Some use 32-bit processors, and some have only 8-or 16-bit microcontrollers.

Because of the variety of wireless access devices, the mechanism for accessing the content from the Internet also varies:

Mobile phones, two-way pagers, and such have limited processing capability, limited memory, and very small display. They need to access the content using protocols such as WAP, and the content has to be in a format such as WML.
Handheld computers have higher processing power, more memory, and color display with larger size. They can run a mobile operating system such as Win CE, PalmOS, or Symbian OS. They can run a browser with better features than a microbrowser and interpret markup languages such as XHTML or XML. Alternatively, these computers can run a KVM (kilobytes virtual machine) that occupy less than 256KB of memory and can download Java code and interpret it.
Laptop computers that can run a full-fledged desktop operating system and access Internet content the way we access the content from desktops.

Handheld computers are becoming more and more powerful, with a full-fledged operating system, color display, handwritten character recognition software, and compact secondary storage devices capable of storing large amounts of data. In a few years they will have processing capabilities comparable to today's desktops, and wireless access of Internet content will be a much better experience. However, cost will continue to be the important factor for users in selecting a mobile device, and a large number of users will continue to have less powerful mobile devices for accessing the Internet.

Wireless Internet access device can be any of the following: mobile phone, pager, personal digital assistant, laptop, palmtop, smart phone, or Internet kiosk installed in a remote/rural area.

Note

The capabilities (processing power, memory, display size, keypad and such) vary widely for mobile devices. Hence, developing the content to take care of these varying capabilities is the biggest challenge in wireless Internet.

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