Getting to Know Wireless Networks and Technology
Wireless networks have been an essential part of communication in the last century. Early adopters of wireless technology primarily have been the military, emergency services, and law enforcement organizations. Scenes from World War II movies, for example, show soldiers equipped with wireless communication equipment being carried in backpacks and vehicles.
As society moves toward information centricity, the need to have information accessible at any time and anywhere (as well as being reachable anywhere) takes on a new dimension. With the rapid growth of mobile telephony and networks, the vision of a mobile information society (introduced by Nokia) is slowly becoming a reality. It is common to see people communicating via their mobile phones and devices. The era of the pay phones is past, and pay phones stand witness as a symbol of the way things were. With today's networks and coverage, it is possible for a user to have connectivity almost anywhere.
Growth in commercial wireless networks occurred primarily in the late 1980s and 1990s, and continues into the 2000s. The competitive nature of the wireless industry and the mass acceptance of wireless devices have caused costs associated with terminals and air time to come down significantly in the last 10 years. As a result, we now have penetration rates of mobile users reaching almost 100% in countries like Taiwan, Italy, and Finland. Subscriber growth has been increasing by leaps and bounds; by mid-2002, the number of subscribers already exceeded 1 billion. The exponential growth of mobile subscribers is shown in Figure 31.
Figure 31 Subscriber statistics source: EMC World Cellular
The service offered on wireless networks today is primarily voice. However, the growth of data via short message services (over 24 billion messages per month, as per data in the Groupe Special Mobile [GSM] World Congress) in the last few years has been increasing rapidly. Wireless networks have evolved to the point today wherein there are two major technologies deployed today: the TDM-based GSM networks, and the CDMA-based networks. GSM networks account for about 70% of the wireless networks today. CDMA accounts for about 25% of the networks, and the other 5% are networks of other types, such as the PDC network in Japan. Many of the TDM-based IS-136 networks that were prevalent in the Americas are now transitioning to either GSM or CDMA. An example of this is the AT&T Wireless network in the U.S., which is currently rolling out a GSM/GPRS network to replace the IS-136 network; the same is the case with Cingular wireless.
The growth of wireless networks is expected to continue well into the first decade of the twenty-first century, and the number of wireless subscribers is expected to overtake the number of fixed lines within the next three years (by 2006).
3.1 Brief History
At the beginning of the 1950s, the Bell telephone company in the United States introduced a radio telephone service for its customers. This was the first instance of a radio telephony network for commercial use. However, this network was small and could accommodate very few subscribers. As the demand for radio telephony service slowly grew, it forced engineers to come up with better ways to use the radio spectrum to enhance capacity and serve more subscribers. In 1964 the concept of shared resources was introduced. This innovation allowed networks to allocate radio resources on a dynamic basis. As a result, more subscribers could be served by the radio networks.
Spectrum for radio telephony was a scarce resource (and still is), and the need to optimize the available resources to increase utilization has always been a driver in radio networks. In 1971 the FCC (Federal Communications Commission) in the United States allocated a frequency band for radio telephony. The Bell telephone company introduced the AMPS (Advanced Mobile Phone Service) radio network, thereby deploying the first cellular network. In 1982 the United States standardized the AMPS system specification, and this became the radio telephony standard for North America.
In the 1980s several cellular radio networks were deployed around the world. In Europe each country chose its own technology for analog cellular telephony. The UK and Italy chose the American system under the name TACS (Total Access Cellular System). The Scandinavian countries and France chose the NMT (Nordic Mobile Telephone) standard. Germany chose the C-Net standard. All these were analog systems and hence considered as first-generation systems.
In 1982 the Conference of European Posts and Telecommunications (CEPT) created the Groupe Special Mobile (now known as GSM) and mandated the creation of a European standard for mobile radio telecommunications in the frequency band reserved for this purpose. This group produced the GSM standard that is widely deployed today. It also introduced digital radio telephony. Hence the second generation of mobile systems was created. In the United States, the Telecommunication Industry Association has developed two interim standardsthe IS-54 standard in 1990, which is based on TDMA, and the IS-95 standard in 1993, which is based on CDMA. The evolution of these networks is covered in Chapter 15.