Books
in black and white
Main menu
Share a book About us Home
Books
Biology Business Chemistry Computers Culture Economics Fiction Games Guide History Management Mathematical Medicine Mental Fitnes Physics Psychology Scince Sport Technics
Ads

GPRS and 3G Wireless application - Anderson C.

Anderson C. GPRS and 3G Wireless application - Wiley publishing , 2001. - 356 p.
ISBN: 0-471-41405 -0
Download (direct link): gprsand3gwirelessapplica2001.pdf
Previous << 1 .. 6 7 8 9 10 11 < 12 > 13 14 15 16 17 18 .. 125 >> Next

In Europe, the countries struggled with no fewer than nine competing analog standards during the 1980s, such as Nordic Mobile Telephony (NMT), Total Access Communications System (TACS), and so on. Pan-European roaming was nothing more than a distant dream at this point, and capacity became an increasingly difficult issue. Europeans therefore saw the need for a completely new system—a system that could accommodate both the increasing subscriber base as well as more advanced features and a standardized solution across the continent. Because of the shortcomings and incompatibility issues with analog systems, they decided to institute a completely new digital solution. The new standard, Groupe Sp?ciale Mobile (GSM), was built as a wireless counterpart of the land-line Integrated Services Digital Network (ISDN) system. Although
Page 15
GSM initially stood for Groupe Sp?ciale Mobile, named after the study group that created it, the acronym later changed to stand for Global System for Mobile communications. This occurrence would not be the last time in the history of mobile systems that an acronym would change, as we will see later. Twenty-six European national phone companies standardized the system, and the working process set the standard for a way of working that has proven successful many times. The countries and the individual companies realized the power of a cross-border standard and the kind of money and energy that can be wasted when competing for world domination on your own.
The results of this and other projects related to “going digital” led to four major 2G wireless systems. Digital AMPS (DAMPS) was a digital add-on to AMPS (which we now call TDMA). With D-AMPS, the handset can switch between analog and digital operation. IS-95, a CDMA-based solution that Qualcomm introduced in the mid 1990s, picked up toward the end of the century. IS-95 is now more commonly called cdmaOne. In Europe and Asia, GSM quickly became the dominant standard with a high degree of extra services, such as the popular Short Message Service (SMS). In Japan, Personal Digital Cellular (PDC) became the number one system. However, this system put Japan in an awkward situation, with an old system that was incompatible with all of the others. This situation triggered the Japanese operators to start an aggressive pursuit of new technology and standards. In the late 1990s, cdmaOne began gaining ground in the Japanese market, increasing the pressure even more on existing PDC operators. Table 2.1 and Figure 2.1 show the distribution between the different systems as of fall 2000.
With the advent of digital systems, the sound of the speaker’s voice was sampled and filtered through various advance speech models, which basically imitate a human ear. The resulting 1s and 0s were sent over the wireless network to the receiving party. A digital mobile user who received a call would hear the reconstructed voice, created by the digital signals passing filters that imitate the human speech system (vocal cords and so on). The digitalization made it possible to squeeze more subscribers into the same radio spectrum, thus increasing efficiency. In addition, the advances in digital chip technology facilitated the development of small and light handsets that boasted an ever-increasing degree
Table 2.1 Number of 2G Subscribers as of August 2000 (per System)
SYSTEM NUMBER OF SUBSCRIBERS IN MILLIONS
GSM 362
cdmaOne 72
PDC 48.8
TDMA (IS-136) 54.3
Page 16
World Subscribers, August 2000
TDM A-136 10%
1
cdmaOr
13%
GSM
Figure 2.1 Number of subscribers of 2G systems as of fall 2000.
Source: EMC World Cellular
of features. These features included voice mail, call waiting, and advanced supplementary services such as SMS. SMS uses the control channels of GSM, TDMA, and cdmaOne systems to transmit messages up to 160 characters long. In the late 1990s, the GSM operators saw an amazing increase in SMS usage. In late 2000, there were almost 15 billion SMS messages sent every month and one billion in Germany alone. Even more noteworthy was the fact that a new segment of the market—teenagers—had taken the lead in using these advanced services. The SMS messages are perfect for communicating in environments where it is hard to hear each other, such as in nightclubs. They also are a quick way of notifying others without entering a long voice call.
The major driving force behind the 3G wireless systems was once again the need for capacity and global roaming, but this time, the motivation was also higher bit rates and a higher Quality of Service (QoS). The work on 3G concepts started in the early 1990s, and in parallel, the Internet wave started to catch on. Therefore, the initial vision was to create a global wireless system with high speed and quality as complements that would fit the need of a mobile Internet. In the struggle to achieve global roaming, the legacy systems were again a major obstacle. With several hundred million mobile users, no one wanted to abandon those subscribers. In the United States, there was another problem with the frequency allocations. Previous auctions of the spectrum that paved the way for the digital 2G systems in the country had effectively blocked the implementation in the 2GHz band (the PCS frequency band is 1900MHz, or 1.9GHz). Japanese and European operators and infrastructure vendors had planned to use this band for 3G. An intensive battle ensued as more and more players started to realize how much was at stake. After many rounds of discussion, they decided that there would be three main branches of the 3G standard and that a convergence effort would begin. The three standards are WCDMA, CDMA2000, and Enhanced Datarates for Global Evolution (EDGE), where
Previous << 1 .. 6 7 8 9 10 11 < 12 > 13 14 15 16 17 18 .. 125 >> Next