One of the most fascinating and swift evolution has been that of the mobile services and the relevant market. It is this evolution that I intend to capture in the following lines. The reasons why I am interested in this is pretty obvious and self-approving. If I can use the clichéd phase that “mobile has become the part and parcel of our life” than it would not be an overstatement by any means. I for myself cannot imagine one-day without my cell phone. Although I sometimes wish I had one. But practically it would be tough. Ok! Now let us take a dive into the world of mobile and different technology evolutions pertaining to it.
The first telephone service was launched in the US at the end of the 1940s. Initial intent was to connect mobile users in cars to the public fixed network. A new system launched by Bell Systems in 1960s, called Improved Mobile Telephone Service” (IMTS), brought many improvements like:
- direct dialing and
- Higher bandwidth.
The first analog cellular systems were based on IMTS and developed in the late 1960s and early 1970s. The systems were called “cellular”, the reason behind that were the smaller areas into which the coverage areas were split. These smaller areas are called “cells” and thus the system is called cellular. Each of these cells is served by a low power transmitter and receiver.
This first generation (1G) analog system for mobile communications witnessed two key improvements during the 1970s:
1. The invention of the microprocessor and
2. The digitization of the control link between the mobile phone and the cell site.
Second generation (2G) digital cellular systems were came into being at the end of the 1980s. These systems did the following:
1. Digitized not only the control link but also the voice signal.
2. The new system provided better quality and higher capacity at lower cost to consumers.
Third generation (3G) systems are the latest kid in the block. They promise faster communications services, including voice, fax and Internet, anytime and anywhere with seamless global roaming.
ITU’s IMT-2000 global standard for 3G has opened the way to enabling innovative applications and services (e.g. multimedia entertainment, infotainment and location-based services, among others). The first 3G network was deployed in Japan in the year 2001.
And very soon we will be hearing about the next gen i.e. the 4G.
The Basics of Cellular Technology and the Use of the Radio Spectrum
Mobile operators make use of radio spectrum to provide the services. Spectrum is generally considered a scarce resource, and has been allocated as such. It has traditionally been shared by a number of industries, including broadcasting, mobile communications and the military.
Before the advent of cellular technology, capacity was enhanced through a division of frequencies, and the resulting addition of available channels. However, this reduced the total bandwidth available to each user, affecting the quality of service. Cellular technology allowed for the division of geographical areas, rather than frequencies, leading to a more efficient use of the radio spectrum. This geographical re-use of radio channels is known as ”frequency reuse”.
In a cellular network, cells are generally organized in groups of seven to form a cluster. There is a “cell site” or “base station” at the center of each cell, which houses the transmitter/receiver antennae and switching equipment. The size of a cell depends on the density of subscribers in an area: for instance, in a densely populated area, the capacity of the network can be improved by reducing the size of a cell or by adding more overlapping cells. This enhances the number of channels available without increasing the actual number of frequencies being used. All base stations of each cell are connected to a central point, called the Mobile Switching Office (MSO), either by fixed lines or microwave. The MSO is generally connected to the PSTN (Public Switched Telephone Network):
Cellular technology allows the “hand-off” of subscribers from one cell to another as they travel around. This is the key feature which allows the mobility of users. A computer constantly tracks mobile subscribers of units within a cell, and when a user reaches the border of a call, the computer automatically hands-off the call and the call is assigned a new channel in a different cell.
As spectrum capacity has been a critical issue each generation has been based on a dominant technology which helped in improving the spectrum capacity.
First Generation – The beginning – 1G:
1) Advanced Mobile Phone System (AMPS): First launched in the US. It is an analog system based on FDMA (Frequency Division Multiple Access) technology. Today, it is the most used analog system and the second largest worldwide.
2) Nordic Mobile Telephone (NMT): Mainly developed in the Nordic countries. (4.5 million in 1998 in some 40 countries including Nordic countries, Asia, Russia, and other Eastern European Countries)
3) Total Access Communications System (TACS): First used in the UK in 1985.
A smarter Second Generation – 2G:
1) Global System for Mobile Communications (GSM) was the first commercially operated digital cellular system. A pan-European initiative, involving the European Commission, telecommunications operators and equipment manufacturers led to its development in 1980s.
2) The European Telecommunications Standards Institute was responsible for GSM standardization.
3) GSM uses TDMA (Time Division Multiple Access) technology. It is being used by all European countries, and has been adopted in other continents.
4) It is the dominant cellular standard today, with over (45%) of the world’s subscribers at April 1999.
5) TDMA IS-136 is the digital enhancement of the analog AMPS technology.
6) It was called D-AMPS when it was first launched in late 1991 and its main objective was to protect the substantial investment that service providers had made in AMPS technology.
7) Digital AMPS services have been launched in some 70 countries worldwide (by March 1999, there were almost 22 million TDMA handsets in circulation, the dominant markets being the Americas, and parts of Asia)
8 ) CDMA IS-95 increases capacity by using the entire radio band with each using a unique code (CDMA or Code Division Multiple Access).
9) It is a family of digital communication techniques and South Korea is the largest single CDMA IS-95 market in the world.
10) Personal Digital Cellular (PDC) is the second largest digital mobile standard although it is exclusively used in Japan where it was introduced in 1994.
11) Like GSM, it is based on the TDMA access technology. In November 2001, there were some 66.39 million PDC users in Japan.
12) Personal Hand-phone System (PHS) is a digital system used in Japan, first launched in 1995 as a cheaper alternative to cellular systems. It is somewhere in between a cellular and a cordless technology.
13) PHS has inferior coverage area and limited usage in moving vehicles.
The emergence of the Third Generation – 3G:
The concept for IMT-2000, “International Mobile Telecommunications”, was born at the ITU as the third generation system for mobile communications. After years of consistent effort under the guidance of the ITU, a important decision was taken in the year 2000: the decision of unanimous approval of the technical specifications for third generation systems under the brand IMT-2000. Following were the further consequences of the decision:
1. The spectrum between 400 MHz and 3 GHz is technically suitable for the third generation.
2. The entire telecommunication industry, including both industry and national and regional standards-setting bodies gave a concerted effort to avoiding the fragmentation that had thus far characterized the mobile market.
3. This approval meant that for the first time, full interoperability and interworking of mobile systems could be achieved.
4. IMT-2000 is the result of collaboration of many entities, inside the ITU (ITU-R and ITU-T), and outside the ITU (3GPP, 3GPP2, UWCC and soon) IMT-2000 offers the capability of providing value-added services and applications on the basis of a single standard.
5. The system envisages a platform for distributing converged fixed, mobile, voice, data, Internet and multimedia services.
6. One of its key visions is to provide seamless global roaming, enabling users to move across borders while using the same number and handset.
7. IMT-2000 also aims to provide seamless delivery of services, over a number of media (satellite, fixed, etc).
8. It is expected that IMT-2000 will provide higher transmission rates:
a. a minimum speed of 2Mbit/s for stationary or walking users, and 348 kb/s in a moving vehicle.
b. Second-generation systems only provide speeds ranging from 9.6 kb/s to 28.8 kb/s.
9. IMT-2000 also provided the following key advantages:
c. Compatibility with existing systems
d. Modular design
Although the third generation has already heralded a sea-change in the way mobile services are perceived, however further developments would definitely be there in this field and we would be seeing many more generations evolving. May be faster than we expect!