33.6 THIRD GENERATION (3G) WIRELESS NETWORKS

< Day Day Up >

To develop high-speed wireless networks, ITU initiated the standardization process in 1986-the Future Public Land Mobile Telecommunication Systems (FPLMTS) working group developed the initial set of standards. FPLMTS is now known as IMT 2000 (International Mobile Telecommunications in the year 2000). UMTS (Universal Mobile Telecommunications Systems) is the European version of IMT 2000. The work was challenging, keeping in mind the different technologies that were in vogue, the huge infrastructures put in place by different operators, the lack of availability of spectrum in the same bands in different countries and increasing demand for higher and higher data rates by the end users. Even today, no common spectrum is available worldwide for 3G networks, and no single technology could be standardized.

3G networks support 2Mbps for handheld devices, 384 kbps for walking mobile devices, and 144kbps for carborne mobile devices.

The broad objectives of 3G systems are:

Should support 2Mbps for handheld devices, 384kbps for walking mobile devices, and 144kbps for car-borne mobile devices.
Should support global roaming.
Should work in all types of radio environments: urban, suburban, and mountainous regions. In these regions, depending on the terrain, the cell size may vary considerably. In suburban or rural areas, the cell size may be large; in indoor environments, the cell size may be very small (picocells).
Should support asymmetric and symmetric services. In asymmetric services, the uplink (from handset to base station) data rates can be lower, and downlink (base station to handset) data rates can be higher. In symmetric services, both uplink and downlink speeds are the same.
Should support the following services:
- Data services such as mail, file transfer, mobile computing.
- Telecom services such as telephony, video telephony, video and audio conferencing, audio/video on-demand, teleshopping, TV, and radio broadcast.

Note

The objective of 3G networks is to support international roaming. Moreover, they should operate in all types of radio environments such as urban, suburban, and hilly and mountainous regions.

33.6.1 3G Standardization Activities

ETSI Special Mobile Group (SMG) in Europe, Research Institute of Telecommunications Transmission (RITT) in China, Association of Radio Industry and Business (ARIB) and Telecommunications Technology Committee in Japan, Telecommunication Technologies Association (TTA) in Korea, and Telecommunications Industries Association (TIA) and T1P1 in the U.S. submitted proposals for 3G standardization based on the call for proposals by ITU Radio Communications Standardization Sector (ITU-R) Task Group 8/1. ETSI SMG submitted UMTS Terrestrial Radio Access (UTRA), China proposed TD-SCDMA, ARIB proposed W-CDMA, and TTA Korea submitted two proposals-one close to ARIB's W-CDMA and one similar to TIA cdma2000. The U.S. proposals were UWC-136, which is an evolution of IS-136; cdma2000, which is an evolution of IS-95; and W-CDMA. Subsequently, two international bodies were established: 3GPP (3G Partnership Programme) and 3GPP2: 3GPP to harmonize and standardize the similar proposal proposals from ETSI, ARIB, TTC, TIA and T1 WCDMA, and related proposals and 3GPP2 for cdma2000-based proposals from TIA and TTA.

A summary of some of the proposed 3G standard systems is as follows:

W-CDMA (FDD): Wideband CDMA with frequency division duplex systems are likely to be deployed in the U.S., Europe, Japan, and other Asian countries. These systems operate in the following frequency bands: IMT 2000 band (1920-1980 MHz, 2110-2170 MHz), PCS 1900 band (1850-1910 MHz, 1930-1990 MHz), and DCS 1800 band (1710-1785 MHz, 1805-1880 MHz). Channel spacing is 5MHz.

A number of proposals have been submitted for standardization of 3G networks. These proposals are based on wideband CDMA and TDMA technologies.

W-CDMA (TDD): Wideband CDMA with time division duplex systems are likely to be deployed in U.S., Europe, Japan, and other Asian countries. The multiple access used is TDMA/CDMA. Channel spacing is 5MHz.

W-CDMA (low chip rate TDD): These systems are similar to W-CDMA (TDD) except that channel spacing is 1.6MHz and data support is limited to 384kbps.

TD-SCDMA: Time division synchronous CDMA systems will be deployed in China and other countries that deploy W-CDMA (TDD). The multiple access technique used is TDMA/CDMA. The channel spacing is 1.6MHz. In phase I, the system supports 384kbps, and in phase II, 2Mbps.

The architecture of Universal Mobile Telecommunications System (UMTS) being standardized by ETSI is shown in Figure 33.9. The radio base station does the functions of a base transceiver subsystem, and the radio network controller does the functions of a base station controller. The RNCs are interconnected through a backbone network called the core network. The core network can be based on ATM technology.

click to expand
Figure 33.9: UMTS.

Though a lot of activity is going on to standardize the 3G wireless networks, the progress is slow because every country already has a huge installation base of cellular networks operating in different frequency bands with different protocols. Achieving uniformity is a difficult and time-consuming task.

Japan, which has its own set of proprietary protocols for its 2G and 2.5G wireless networks, however, has made headway in deploying a 3G network and offering multimedia services.

In October 2001, Japan's NTT DoCoMo became the first operator to introduce a 3G network on a commercial basis. The network is based on W-CDMA. The architecture of the network is shown in Figure 33.10. The network supports both packet switching and circuit switching operation. Data services use packet switching. The packet switching speeds are 64kbps in uplink and 384kbps in downlink. For applications like video conferencing, circuit switching is used at a data rate of 64kbps. In addition to all the data services, applications such as music and image distribution are also supported. This service is known as FOMA (Freedom of Mobile Multimedia Access). The protocols used are known as i-mode, proprietary to NTT DoCoMo.

click to expand
Figure 33.10: NTT DoCoMo's FOMA.

NTT DoCoMo is the first operator to provide 3G services in Japan. The network is based on W-CDMA and supports 64kbps uplink speed and 384kbps downlink speed. This service is known as Freedom of Mobile Multimedia Access (FOMA).

Wireless Internet holds great promise-wireless subscribers are likely to grow from 400 million in 2000 to 1.8 billion by 2010. By 2010, 60% of the traffic is expected to be multimedia. Hence, operators and equipment manufacturers can reap rich benefits. More than that, users will be greatly benefited-a wide variety of services will be available to them anywhere, anytime and at a very low cost.

Summary

In this chapter, we studied the technologies for accessing the Internet through wireless devices. The second generation wireless networks support data rates up to 28.8kbps only. Even mobile devices to access the data services have limited capabilities, such as low processing power, small display, and little RAM. To access Internet services using such devices over wireless networks with low data rate support, the wireless application protocol (WAP) has been developed. The WAP protocol stack facilitates accessing Web service for applications such as obtaining stock quotes, weather information, and so forth that are basically text oriented. WAP has very limited capability to support high-resolution graphics or animation.

With the advent of 2.5G wireless networks, data rates up to 144kbps can be supported using high-speed circuit switched data (HSCSD) and general packet radio service (GPRS), which evolved from the GSM system. As the capabilities of the mobile devices also increased, services such as audio streaming multimedia services can be supported over these networks.

Third generation wireless networks based on CDMA technology will support data rates up to 2Mbps, and full-fledged multimedia applicatio0ns can be accessed over these networks. However, standardization of technologies for 3G is still in progress. 3G promises multimedia communications anytime, anywhere in the near future.

References

Dreamtech Software Team. WAP, Bluetooth and 3G Programming. Wiley-Dreamtech India Pvt. Ltd., 2002. This book gives the source code listings for a number of wireless applications.
Dreamtech Software Team. Programming for Embedded Systems, Wiley-Dreamtech India Pvt. Ltd., 2002. This book also contains source code listings for wireless applications using J2ME, BREW, and WAP.
J. Korhonen. Introduction to 3G Mobile Communications, Artech House, 2001.
T. Ojanpera, R. Prasad (Ed.): WCDMA: Towards IP Mobility and Mobile Internet, Artech House, 2001.
http://www.3gpp.org Official site of the 3G Partnership Program.
http://www.cdg.org Web site of CDMA development group.
http://www.java.sun.com/products/j2metoolkit/download.html You can download the J2ME toolkit from this link. Using J2ME, you can develop wireless mobile applications.
http://www.microsoft.com/mobile/pocketpc Microsoft's Pocket PC is another popular platform for mobile applications.
http://www.nttdocomo.com Gives information on i-mode and FOMA.
http://www.openwap.org Web site that provides links to WAP toolkits.
http://www.palmos.com Web site of Palm Corporation. Palm OS is a popular operating system for mobile devices.
http://www.qualcomm.com/Brew You can download the BREW (binary runtime environment for wireless) development kit from Qualcomm's Web site. BREW facilitates development of wireless data applications. Qualcomm is a pioneer in CDMA technology, and the site provides information on CDMA-based 3G systems.
http://www.sss-mag.com/w-cdma1.html Provides resources on CDMA.
http://www.the3gportal.com Provides rich information on 3G wireless networks.
http://www.tiaonline.org/standards IMT 2000 standards and other resources from Telecommunications Industries Association.
http://www.uwcc.org Web site of Universal Wireless Communications Consortium.
http://www.wapforum.org Provides information on technology and standards of WAP.

Questions

What are the problems involved in accessing the Internet through wireless networks?
Describe the various proposals/plans to evolve 3G wireless networks from the present 2G wireless networks.
Describe the WAP protocol architecture.
Differentiate between the push model and the pull model. What are the pros and cons of the push model?
Explain how location-based services can be provided over mobile phones. Discuss the pros and cons of such services. Do you think that the privacy of individuals is at stake because of such services?

Exercises

1.	Download a WAP toolkit and experiment with it.
2.	Download J2ME toolkit and experiment with it.
3.	Download BREW development kit and experiment with it.
4.	Write a technical paper on mobile operating systems (Palm OS, Windows CE, Symbian OS, embedded Linux, Embedded XP, and others).
5.	Write a technical paper on Mobile IP.
6.	Write a technical paper on location-based services.

Answers

1.	You can download WAP toolkits from the Web sites of Nokia, Ericsson, Motorola, and others. These tookkits can be used to develop and test mobile applications in the lab before deploying the applications in the actual mobile network environment. Using WML and WML Script, you can create good applications and test them. The framework for developing a mobile commerce application using the push model is given in the following. Assume that there is a Web site that provides the facility to buy various items through your mobile phone. The Web site also sends the latest information about new arrivals in the items of your choice. To start with, you need to register yourself with the Web site and give details such as your mobile phone number, your preferences, and the frequency with which you would like to receive the advertisement information. A sample registration form is shown in Figure C.13. Figure C.13: Registration form for mobile push application. Once you are a registered user of the Web site, you keep getting information from the Web site using the push model. You can also use the mobile cart to place an order for different items. To achieve this functionality, you need to create the necessary HTML files, a database that stores the complete information about all the registered users, and Java programs that run on the server and send the information to the users. You also need to create the WML file that provides the interface to the user on the mobile device. The screenshot with the first screen of the mobile commerce application is shown in Figure C.14. Figure C.14: M-commerce application on a mobile phone.
2.	J2ME facilitates the development of mobile applications using the Java programming language. Keeping in mind the limitations of the mobile devices such as small display, limited functionality keypad, and so on. The J2ME provides limited GUI capabilities and is optimized to work on devices with less memory. You can download the J2ME kit from Sun Microsystems Web site.
3.	Binary runtime environment for wireless (BREW), developed by Qualcomm, facilitates development of mobile applications for CDMA-based wireless networks. You can download the kit from Qualcomm's Web site http://www.qualcomm.com.
4.	Mobile phones do not have an operating system. However, devices such as personal digital assistants and palmtops have an operating system. The operating systems that are ported on the mobile devices are known as mobile operating systems. Palm OS, developed by Palm Computing Inc., is the most famous mobile OS. Other operating systems that now have a large installation base are Symbian OS, Windows CE and Windows XP. Embedded Linux has also gained importance in recent years.
5.	When a mobile device moves from one service area to another service area, to ensure that there is no disruption in the service, mobile IP is required. In mobile IP, the mobile device is given two addresses, called home address and care-of address. The home address is a permanent address, and the care-of address is a temporary address that is given when the mobile device is in a foreign area. The packets addressed to the mobile device will be received by the home network and forwarded to the care-of address.
6.	You can obtain information from the following sites: http://www.nokia.com, http://www.ericsson.com, http://www.microsoft.com.

Projects

Develop a mobile commerce application using WML and WMLScript. The program has to access a WAP server that sells pizza, burger and, soda. You should be able to order any item of your choice and also specify the quantity. Test the application using a WAP toolkit (for instance, that of Nokia).
Create a WAP push application for mobile advertising. The user has to log on to a server and give his preferences for receiving advertisements (for example, books, jewelry, cosmetics). The arrival of a new item has to be pushed to the user. Write the code using WML, WMLScript, and servlets. Use a WAP toolkit.
Develop a mobile portal for tourism. The user has to log on to a server to obtain information about tourist spots such as historical places, museums, and parks in a city. He also should be able to obtain information about the important hotels and restaurants in the city. You can use a WAP toolkit or a BREW toolkit.
Using a WAP toolkit, develop a push application that sends the latest football scores every 15 minutes to a mobile phone.
Develop software that converts an HTML file into a WML file. Tags supported by HTML but not by WML should be ignored.

< Day Day Up >